Research ArticleStudy on Probabilistic Safety Goals for MultimoduleHigh-Temperature Gas-Cooled Reactor Based on ChineseSocietal Risks

Jinghan Zhang Jun Zhao and Jiejuan Tong

Tsinghua University Institute of Nuclear and New Energy Technology Beijing 100084 China

Correspondence should be addressed to Jiejuan Tong tongjjmailtsinghuaeducn

Received 18 February 2021 Accepted 27 May 2021 Published 7 June 2021

Academic Editor Alejandro Clausse

Copyright copy 2021 Jinghan Zhang et al(is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Nuclear safety goal is the basic standard for limiting the operational risks of nuclear power plants(e statistics of societal risks arethe basis for nuclear safety goals Core damage frequency (CDF) and large early release frequency (LERF) are typical probabilisticsafety goals that are used in the regulation of water-cooled reactors currently In fact Chinese current probabilistic safety goalsrefer to the Nuclear Regulatory Commission (NRC) and the International Atomic Energy Agency (IAEA) and they are not basedon Chinese societal risks And the CDF and LERF proposed for water reactor are not suitable for high-temperature gas-cooledreactors (HTGR) because the design of HTGR is very different from that of water reactor And current nuclear safety goals areestablished for single reactor rather than unit or site (erefore in this paper the development of the safety goal of NRC wasinvestigated firstly then the societal risks in China were investigated in order to establish the correlation between the probabilisticsafety goal of multimodule HTGR and Chinese societal risks In the end some other matters about multireactor site werediscussed in detail

1 Introduction

Nuclear energy is a special kind of energy source with manyadvantages and it is conducive to solving the energy crisis[1] However a large amount of radioactive materials will beproduced when using nuclear energy and they seriouslythreaten the surroundings So far there have been threemajor nuclear accidents in the world the (ree Mile Islandnuclear accident in the United States the Chernobyl nuclearaccident in the former Soviet Union and the Fukushimanuclear accident in Japan Each nuclear accident seriouslydamaged human health and the surrounding environment[2] Due to the adverse effects of a nuclear accident we needto ensure the safe design safe construction and safe op-eration of nuclear power plants to reassure the publicrsquosconcerns and doubts

Nuclear safety goals are set to control the severity of theadverse effects on the public and environment when nuclearpower plants are in operation or accidents occur On the one

hand the safety goals can be used to guide the designoperation and management of nuclear power plants toestablish a set of effective protection measures in nuclearpower plants to protect personnel society and the envi-ronment from radioactive hazards On the other handreasonable safety goals can promote public understanding ofthe safety of nuclear energy and have a positive impact onthe development of nuclear energy In order to promote therealization of nuclear safety goals and to make the safetygoals more applicable in the actual design and managementof nuclear power plants the subsidiary numerical safetygoals are always defined and used as surrogate safety goalsfor qualitative and quantitative safety goals Core damagefrequency (CDF) and large early release frequency (LERF)are the typical probabilistic safety goals that are used toevaluate the safety of water-cooled reactors [3]

(e modular pebble-bed high-temperature gas-cooledreactor (HTR-PM) is in the construction in China as ademonstration project It includes one turbine and two

HindawiScience and Technology of Nuclear InstallationsVolume 2021 Article ID 5523104 10 pageshttpsdoiorg10115520215523104

reactors and two reactors are used to drive one turbine [4](e typical CDF and LERF which has been developed basedon the characteristics of water-cooled reactors are not ap-plicable to HTR-PM due to the unique design concept ofhigh-temperature reactor (HTR) (e most important dif-ference is that core damage will not happen in the HTR(erefore the probabilistic safety goal of HTR-PM has beenreestablished by China National Nuclear Safety Adminis-tration (NNSA) that is ldquothe cumulative frequency of allbeyond design basis accident sequences that lead to off-site(including plant boundary) personal effective dose ex-ceeding 50mSv shall be less than 10minus 6(r middot y)rdquo It should benoted that this safety goal is dedicated to HTR-PM projectand it is focused on single reactor rather than unit (tworeactors and one turbine) In order to promote the devel-opment of multimodule HTGR the probabilistic safety goalbased on the ldquounitrdquo or ldquoplantrdquo must be studied

According to the method of nuclear safety goal for-mulation the societal risks statistics are the basis for nuclearsafety goals At present the probabilistic safety goals (CDFand LERF) of Chinese nuclear power plants refer to theAmerican nuclear safety goals which are based on the so-cietal risks of the United States rather than the societal risksof China (erefore it is necessary to investigate Chinesesocietal risks based on the mortality rate of statistical data toprovide a basis for the probabilistic safety goals of multi-module HTGR

(is paper aims to study the probabilistic safety goals ofmultimodule HTGR to support the probabilistic safety as-sessment of high-temperature gas-cooled reactors In Sec-tion 2 the existing nuclear safety goals in the InternationalAtomic Energy Agency (IAEA) the United States NuclearRegulatory Commission (NRC) and China have been in-vestigated to provide technical references for verifying thevalue of the probabilistic safety goals of HTGR And theformulation and evolution of United States National NuclearRegulatory Commission (USNRC) has been studied in orderto guide the development of probabilistic safety goals ofmultimodule HTGR In Section 3 the societal risks in Chinaand other countries have been investigated in detail toprovide the basis for determining the value of the proba-bilistic safety goals of multimodule HTGR In Section 4 thekey aspects of development of probabilistic safety goals ofmultimodule HTGR have been studied and the correlationbetween the probabilistic safety goals and Chinese societalrisks has been established (e last section is the discussionand conclusion

2 Evolution of Safety Goals

21 Overview of Existing Safety Goals In a report publishedby the Organization for Economic Cooperation and De-velopmentNuclear Energy probabilistic safety goals includethe following four categories core damage frequency (CDF)release frequencies such as large release frequency (LRF)and large early release frequency (LERF) frequency of dosesand criteria on containment failure frequency (CFF) [3] Atpresent many countries or organizations have formulatedthe probabilistic safety goals including International Atomic

Energy Agency (IAEA) [5] US Nuclear Users RequestDocumentation (URD) [6] European Utility Requirement(EUR) [7] and European Pressurized Reactor (EPR) [8]

In this section the probabilistic safety goals in IAEA theUS and China were introduced and the comparisons be-tween the nuclear safety goals in China and the US weregiven

(1) IAEA adopted the probabilistic safety goals of the USdirectly after the Chernobyl nuclear accident in 1986During 1988ndash2001 IAEA issued INSAG-3 INSAG-12 NS-G-1 and NS-G-12 for nuclear safety goals[9ndash12] Current probabilistic safety goals of IAEA areas follows for existing reactorsCDFlt 10minus 4(reactor middot year) (reactor middot year r middot y)LERFlt 10minus 5(r middot y) for new reactorsCDFlt 10minus 5(r middot y) eliminate radioactive large re-lease practically that require early off-site emergencyresponse

(2) (eUS is the first to quantify nuclear safety goals andcombine deterministic theory and probabilistictheory in the study of technical safety goals In 1986Nuclear Regulatory Commission (NRC) issued thefinal nuclear power plant safety goals policy state-ment which determined qualitative safety goalsquantitative safety goals and subsidiary safety goals[13ndash15] Current probabilistic safety goals of the USare as follows for existing reactorsCDFlt 10minus4(r middot y) LERFlt 10minus5(r middot y)

(3) Chinese nuclear safety goals mainly refer to thenuclear safety goals of US and IAEA Many laws andregulations have been issued in China includingHAF 102ndash1991 HAF102-2004 HAD10217ndash2006the 12th Five-Year Plan for Nuclear Safety HAF102-2016 and the 12th Five-Year Plan for Nuclear Safety[16ndash19] Current probabilistic safety goals in Chinaare as follows for existing reactorsCDFlt 10minus4(r middot y) LERFlt 10minus5(r middot y) for new re-actors CDFlt 10minus5(r middot y) LERFlt 10minus6(r middot y)

(e nuclear safety goal systems in China and the UnitedStates are shown in Figure 1 We compared the nuclearsafety goals of China and the US from protection andprevention qualitative safety goal quantitative safety goaland subsidiary safety goal In fact there is no specificquantitative safety goal in China

22 Probabilistic Safety Goals of NRC In this section theevolution of safety goals of NRC was investigated includingthe relationship between CDF and LERF with quantitativehealth objective (QHO)

221 Overview of Probabilistic Safety Goals of NRC In 1979the (ree Mile Island nuclear accident occurred in theUnited States After the accident the proposal of establishingnuclear power reactor quantitative safety goals and per-fecting safety principles was put forward In 1980 the NRCissued a response to set nuclear safety goals In 1981 the

2 Science and Technology of Nuclear Installations

NRC formulated a draft nuclear safety goals policy statementbased on the results of expert seminars [13] In 1983 theNRC issued a formal nuclear safety goals policy statementbased on the results of discussions in various industries [14]In 1986 the NRC issued a final nuclear safety goals policystatement and provided two qualitative safety goals and twoquantitative safety goals [15]

Individual qualitative safety goal (IQSG) means promptfatalities risks to an average individual in the vicinity of anuclear power plant caused by reactor accidents Societalqualitative safety goal (SQSG) means cancer fatalities to thepopulation in the area of a nuclear power plant caused bynuclear power plant operation Because the qualitative safetygoal cannot be used to guide the design and operation ofnuclear power plant (NPP) two quantitative safety goalshave been proposed based on the two 01 rule whichinclude early quantitative health objective (EQHO) andlatent quantitative health objective (LQHO)(e EQHO andLQHO have been derived from the societal risk of Americathat is the risk to residents of NPP cannot exceed otherexisting societal risks obviously this is the so-called ldquotwo01 rulerdquo (e risk to the average individual in the vicinityof a nuclear power plant of prompt fatalities that mightresult from reactor accidents should not exceed 01 of thesum of prompt fatality risks resulting from other accidents towhich members of the US population are generally exposed(e risk to the population in the area near a nuclear powerplant of cancer fatalities that might result from nuclearpower plant operation should not exceed 01 of the sum ofcancer fatality risks resulting from all other causes [15]

CDF and LERF as subsidiary safety goals used to besurrogate safety goals of LQHO and EQHO respectivelysince the applicability of quantitative safety goals is still poor(e unit of CDF and LERF is per reactor year (rmiddoty) (e unitof the individual fatality risk is per year (y) Based on thelater assessments of the sites surrounding environment and

demographic conditions of nuclear power plants in the USCDFlt 10minus 4(r middot y) and LERFlt 10minus 5(r middot y) meet the 01and 01 quantitative safety goals (e relationship amongnuclear safety goals in the US is shown in Figure 2 (equantitative safety goals (IQSG and SQSG) mean that theoperation of nuclear power plants will not cause obviousadditional risks to the life and health of the public Quali-tative safety goals (EQHO and LQHO) are measuredachieved through quantitative safety goals Subsidiary safetygoals (LERF and CDF) make quantitative safety goals morespecific and easier to implement

222 LERF and EQHO [20] LERFlt 10minus 5(r middot y) is a sub-sidiary goal of early quantitative health objectives (EQHO)for early prompt fatalities (e rationality of substitutingLERF for EQHO is demonstrated as follows

According to the data survey for nuclear safety goals theindividual risk of prompt fatality caused by all other acci-dents is 5 times 10minus 4y in the US (ese accidents include trafficaccidents production accidents and other accidentsAccording to the 01 in the early quantitative health ob-jective (EQHO) the individual early risk (IEREQHO) causedby nuclear power plant accidents need to be less than5 times 10minus 7(r middot y) (e vicinity of a nuclear power plant meansan extension of 1 mile from the boundary of the nuclearpower plant Individual early risk (IER) is

IER 1113944M

1

EFm lowast LERFm( 1113857

TP(1) (1)

where EFm is the number of early prompt fatalities within 1mile caused by accident sequencem LERFm is the frequencyof fatal early large release caused by accident sequence mand TP(1) is the total population within 1mile of the nuclearpower plant

Protection and prevention

Qualitative safety goal

Quantitative safety goal

Subsidiary safety goal

Defensendashinndashdepth

General safety goalradiation protection goal

technical safety goal

CDF LRF

Adequate protection

Life health society

Quantitative health objective01 and 01

CDF LRF

Nuclear safety goal Nuclear safety goal

As low as possible

Figure 1 Nuclear safety goal systems in China and the United States

Science and Technology of Nuclear Installations 3

(en in the population TP(1) the number of earlyprompt fatalities caused by accident sequence m is given by

EFm CPEFm lowastTP(1) (2)

CPEFm is the conditional probability of early promptfatalities caused by accident sequence m meaning theconditional probability of one personrsquos early fatality causedby a radioactive release nuclear accident

According to formulae (1) and (2) the individual earlyprompt fatality risk is

IER 1113944M

1CPEFm lowast LERFm (3)

Suppose a worst accident sequence m which has thegreatest impact on early prompt fatalities risk (is accidentsequencem corresponds to a large break in the containmentand an unscrubbed release occurred before the surroundingpopulation were effectively evacuated According to theSurry PRA in NUREG-1150 the CPEF of the worst accidentsequence is 3 times 10minus 2

Put CPEF 3 times 10minus 2 and the safety goal value LERF

1 times 10minus 5(r middot y) into formula (3) (en when the worstaccident sequence m occurs the individual early promptfatality risk is

IERm 3 times 10minus 21113872 1113873 times 10minus 5

1113872 1113873 3 times 10minus 7(r middot y)lt IEREQHO

5 times 10minus7(r middot y)

(4)

(erefore using LERFlt 10minus 5(r middot y) as a subsidiary goalof early quantitative health objectives (EQHO) for earlyprompt fatalities is acceptable

223 CDF and QHO [20] CDFlt 10minus 4(r middot y) is a subsid-iary goal of latent quantitative health objectives (LQHO) forlatent cancer fatalities (e rationality of substituting CDFfor LQHO is demonstrated as follows

According to the data survey for nuclear safety goals theindividual risk of cancer fatality from all other causes is 2 times

10minus 3y in the US According to the 01 in the latentquantitative health objective (LQHO) the individual latentrisk (ILRLQHO) caused by nuclear power plant operationsneed to be less than 2 times 10minus 6(r middot y) (e area of a nuclearpower plant means an extension of 10 mile from the

boundary of the nuclear power plant Individual latent risk(ILR) is

ILR 1113944N

1

LFn lowast LLRFn( 1113857

TP(10) (5)

where LFn is the number of latent cancer fatalities within 10miles caused by accident sequence n LLRFn is the frequencyof cancerogenic off-site individual doses caused by accidentsequence n and TP(10) is the total population within 10miles of the nuclear power plant

(en in the population TP(10) the number of latentcancer fatalities caused by accident sequence n is given by

LFn CPLFn lowastTP(10) (6)

where CPLFn is the conditional probability of latent cancerfatalities caused by accident sequence n

According to formulae (5) and (6) the individual latentcancer risk is

ILR 1113944N

1CPLFn lowast LLRFn (7)

Suppose a worst accident sequence n which has thegreatest impact on latent cancer fatalities risk (is accidentsequence n corresponds to a large opening in the con-tainment and an unscrubbed release occurred after thesurrounding population were effectively evacuated Supposethe worst accident occurs in an open containment theconditional large latent release probability for accident se-quence n (CLLRPn) is 10

(en

LLRFn CDFn lowastCLLRPn CDFn lowast 10 CDFn (8)

Putting formula (8) into formula (7) the risk of indi-vidual latent cancer fatality risk is

ILRn CPLFn lowastCDFn (9)

According to the Surry PRA in NUREG-1150 the CPLFof the worst accident sequence is 4 times 10minus 3

Put CPLF 4 times 10minus 3 and the safety goal value CDF

1 times 10minus 4(r middot y) into formula (6) (en when the worstaccident sequence n occurs the individual latent cancerfatality risk is

ILRn 4 times 10minus 31113872 1113873 times 10minus 4

1113872 1113873 4 times 10minus 7(r middot y)lt ILRLQHO

2 times 10minus6(r middot y)

(10)

(erefore using CDFlt 10minus 4(r middot y) as a subsidiary goalof latent quantitative health objectives (LQHO) for latentcancer fatalities is acceptable

3 Investigation into Chinese Societal Risk

According to the process of determining probabilistic safetygoals of USNRC probabilistic safety goals are based onsocietal risks Chinese current probabilistic safety goals refer

Qualitative safety goals

Quantitative safety goals

Subsidiary objectives

IQSG

EQHO

LERF

SQSG

LQHO

CDF

Figure 2 (e relationship among nuclear safety goals in the US

4 Science and Technology of Nuclear Installations

to NRC and IAEA and they are not based on Chinesesocietal risks (erefore we need to investigate the Chinesesocietal risks firstly and then formulate and verify proba-bilistic safety goals based on Chinese societal risks

(e data about the societal risk (ie mortality rate) canbe obtained from the Chinese government and internationalorganizations Chinese statistics include the National Eco-nomic and Societal Development Statistical Bulletin andChinarsquos Health Statistical Yearbook [21 22] Internationalorganizationsrsquo statistics include World Health Organiza-tionrsquos data [23] and World Bankrsquos data [24]

According to the contents of probabilistic safety goalswe focus on early prompt fatalities and latent cancer fatalitiescaused by nuclear power plant operation which can berepresented by accident mortality and cancer mortality insociety respectively

In this section the general overview of Chinese societywas investigated firstly including the analysis about maincauses of fatalities in Chinese society and then make acomparison between the death rate of China and severalother countries

31 Main Causes of Fatalities in China (e total populationof China the number of deaths the number of urban andrural residents and the GDP from 2012 to 2017 are shown inTable 1

(e mortality rates of different causes were countedrespectively when counting the main causes of fatalities ofChinese population (en the causes of death were sortedaccording to the value of mortality (e source data arederived from the Chinese government and internationalorganizations and the statistical results were compared toensure the authenticity of the data Statistics from theChinese government (2012ndash2017) are shown in Table 2Statistics from international organizations (2000 2010 2015and 2016) are shown in Table 3

(e causes of fatalities of Chinese population werecounted based on the source data from Chinese governmentand international organizations as shown above Accordingto the comparison of the above data the difference betweenthe data obtained through the two channels is small whichproves that the statistics are true and reliable (e maincauses of fatalities of Chinese population include malignantneoplasms cerebrovascular diseases heart diseases respi-ratory diseases and external causes of damage andpoisoning

32 Main Causes of Fatalities in Other Countries It is nec-essary to investigate other countriesrsquo societal risks andcompare the results with Chinese societal risks On the onehand the authenticity and reliability of the data can beproved through comparative analysis On the other handinvestigating more countriesrsquo societal risks can help us toprovide further suggestions for nuclear safety goals based onsocietal risks China the United States Japan the UnitedKingdom France India Egypt and Sudan were selected asthe research object countries according to the developmentstatus and the level of nuclear power in each country (e

causes of death and mortality in these countries in 2016 werecounted and the results are shown in Table 4

According to the statistical data from international or-ganizations the causes of death and mortality of China theUnited States Japan the United Kingdom France IndiaEgypt and Sudan in 2016 were counted According to thecomparisons of the causes of death and mortality of Chinaand the US the societal fatalitiesrsquo risks in China and in theUS are similar For example the mortality rates caused bycardiovascular diseases malignant neoplasms respiratorydiseases and injuries are 31710 16788 6647 and 5115 inChina and 25987 19483 7665 and 5698 in the US Forprobabilistic safety goals we focus on the mortality rate ofmalignant neoplasms and external causes which are similarbetween China and the US as well

Furthermore the nuclear safety goals of the US wereformulated and revised from 1979 to 1986 According todata from international organizations the mortality rate ofmalignant neoplasms and external causes in the UnitedStates from 1978 to 1985 were counted and the results areshown in Table 5

According to the statistical data in the table the mor-tality rate of malignant neoplasms and external causes in theUnited States has not changed much from 1978 to 1985 andthey are similar to the current risks of malignant neoplasmsand external causes in China

33 Probabilistic Safety Goals of Multimodule HTGRHigh-temperature gas-cooled reactors are extremely un-likely to cause serious core damage and large early releasedue to inherent safety and unique design concepts CDF andLERF proposed for water-cooled reactor are not suitable forhigh-temperature gas-cooled reactor (erefore the prob-abilistic safety goal of HTR-PM has been reestablished byChina National Nuclear Safety Administration (NASA) thatis ldquothe cumulative frequency of all beyond design basisaccident sequences that lead to off-site (including plantboundary) personal effective dose exceeding 50mSv shall beless than 10minus 6(r middot y)rdquo and this risk metric is defined as theldquofrequency of LARGE release categoryrdquo in HTR-PM prob-abilistic safety analysis (PSA) model In this section weverified the rationality of Chinese existing probabilisticsafety goals for water reactors and then studied the prob-abilistic safety goals for Chinese high-temperature gas-cooled reactors

34ChineseExistingProbabilistic SafetyGoals (emortalityrate of malignant neoplasms and external causes are im-portant basis when verifying the rationality of Chineseexisting CDF and LERF based on the current societal risks inChina According to the above statistics on Chinese societalrisks the statistical results of the mortality rate of malignantneoplasms and external causes are as follows Statistics basedon data from the Chinese government are shown in Table 6and statistics based on data from international organizationsare shown in Table 7

According to the data from the Chinese government andinternational organizations shown in Tables 6 and 7 the

Science and Technology of Nuclear Installations 5

individual latent cancer fatality risk (ILCFR) is about16 times 10minus 3y and the individual early prompt fatality risk(IEPFR) is about 5 times 10minus 4y

According to the Chinese societal risks the reasonabilityof existing probabilistic safety goals in China is shown inFigure 3 Based on the Chinese societal risks and quantitativesafety goals (ldquotwo 01 rulerdquo) the individual latent cancerfatality risk caused by nuclear power plant operation(ILCFRNPP) should be less than 16 times 10minus 6y and the in-dividual early prompt fatality risk caused by nuclear powerplant accidents (IEPFRNPP) should be less than 5 times 10minus 7yBased on the subsidiary safety goals and the assessment ofnuclear power plant the ILCFRNPP is less than 4 times 10minus 8yand the IEPFRNPP is less than 3 times 10minus 8y As shown aboveChinese current probabilistic safety goals can meet the needsof Chinese societal risks control

35 Probabilistic Safety Goals of Multimodule HTGR (edesign characteristics and defense-in-depth measures ofmultimodule HTGR nuclear power plants are differentfrom those of water reactor nuclear power plants Due tothe safety design concept inherent safety and passive

safety measures there is extremely low large release fre-quency and longer time before radioactive material is re-leased into the environment So there is longer time forpostaccident mitigation and emergency response allowingmore measures to actually eliminate core damage and largeearly release (erefore it uses the ldquofrequency of LARGErelease categoryrdquo defined in HTGR PSA as the risk indexrather than the CDF or LERF According to the risk metricof HTR-PM it should be less than 10minus 6(r middot y) However itshould be noted that this safety goal is dedicated to HTR-PM project and it is focused on single reactor rather thanunit (two reactors and one turbine) (erefore this papertries to study whether this risk metric can be extended to beapplied to the multimodule HTGR that is can we use theldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y) as the risk metric ofmultimodule HTGR directly

In the following we will use the risk metric of HTR-PMto demonstrate the margin of probabilistic safety goal

(e ldquoLARGErdquo release category of HTR-PM is similarto the LERF of water reactors and it focuses on earlyprompt fatalities risks and EQHO Individual early risk(IER) is

Table 1 General overview of Chinese Society

Year Total population (rsquo0000) Dead population (rsquo0000) Urban population (rsquo0000) Rural population (rsquo0000) GDP (100 million)2012 135404 966 71182 64222 5193222013 136072 972 73111 62961 5688452014 136782 977 74916 61866 6364632015 137462 975 77116 60346 6767082016 138271 977 79298 58973 7441272017 139008 986 81347 57661 827122Source National Economic and Societal Development Statistical Bulletin [22]

Table 2 Demographic mortality statistics in China based on Chinese data

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017Malignant neoplasms 1583 1526 1574 1598 1583 1591Cerebrovascular diseases 1277 1370 1376 1394 1400 1394Heart diseases 1259 1383 1396 1402 1440 1469Respiratory diseases 890 760 768 763 744 719External causes of damage and poisoning 462 474 457 446 447 432Other diseases 264 82 68 62 61 60Digestive diseases 160 155 145 142 142 145Endocrine nutritional and metabolic diseases 142 146 156 171 184 188Infectious 69 74 72 72 70 67Neurological conditions 66 68 68 67 75 77Genitourinary diseases 65 67 69 68 69 71Mental disorders 25 28 27 28 28 27Acatalepsia 23 25 25 23 22 21Neonatal conditions 23 22 23 19 20 17Congenital anomalies and chromosomal abnormalities 20 21 20 18 16 16Musculoskeletal diseases 14 17 17 17 20 21Blood hematopoietic organ and immune disorders 12 12 12 12 13 13Complications of pregnancy childbirth and puerperium 01 01 01 01 01 01Parasitic diseases 01 01 00 01 01 01Source Chinarsquos Health Statistical Yearbook [21] Note External causes of injury and poisoning include traffic accidents poisoning falls fires naturaldisasters mechanical asphyxiation suicide homicide and mechanical injuries

6 Science and Technology of Nuclear Installations

IER 1113944H

1

EFh lowast LARGEh( 1113857

TP(1) (11)

where EFh is the number of early prompt fatalities within 1mile caused by accident sequence h LARGEh is the fre-quency of fatal LARGE categories caused by accident se-quence h TP(1) is the total population within 1 mile of thenuclear power plant

(en in the population TP(1) the number of earlyprompt fatalities caused by accident sequence h is

EFh CPEFh lowastTP(1) (12)

where CPEFh is the conditional probability of early promptfatalities caused by accident sequence h meaning the con-ditional probability of one personrsquos early fatality caused by aradioactive release nuclear accident

According to formulae (9) and (10) the individual earlyprompt fatality risk is

IER 1113944H

1CPEFh lowast LARGEh (13)

According to the data survey for Chinese societal risksthe individual risk of prompt fatality caused by all otheraccidents is 5 times 10minus 4y in China According to the 01 inthe early quantitative health objective (EQHO) the indi-vidual early risk (IEREQHO) caused by nuclear power plantaccidents needs to be less than 5 times 10minus 7(r middot y) Suppose aworst accident sequence h which has the greatest impact onearly prompt fatalities risk An unscrubbed release occurred

before the surrounding population were effectivelyevacuated

Suppose

IERh CPEFh lowast LARGEh IEREQHO 5 times 10minus 7

(r middot y) (14)

According to the probabilistic safety goals for multi-HTGR LARGEh 1 times 10minus 6(r middot y)

(us CPEFh 05(at is the conditional probability of early prompt fa-

talities caused by the worst accident sequence h is 05 it justmeets the EQHO for individual early prompt fatalities risks

In the International Commission on Radiological Pro-tection (ICPR) Publication 60 according to the dosethreshold of the deterministic effects the 60-day medianlethal dose (LD50[60]) is 3sim5Gytime (e probability ofstochastic effects increases with increasing dose Stochasticeffects include cancer and hereditary diseases For cancerthe probability coefficients of fatal cancer are 5 times 10minus 2Sv forthe public and 4 times 10minus 2Sv for occupational workers en-gaged in radiation For hereditary diseases the probabilitycoefficients of hereditary diseases are 1 times 10minus 2Sv for thepublic and 06 times 10minus 2Sv for workers ICPR 103 followed theconclusion of the ICRP 60 the combined detriment due tofatal cancer and hereditary diseases remains unchanged ataround 5 times 10minus 2Sv For HTR-PM there is extremely lowlarge release frequency and the personal effective dosecontrol threshold is 50mSv According to the results ofabove analysis when LARGEh 1 times 10minus 6(r middot y)andCPEFh 05 the risk metric of HTR-PM can meet the re-quirements of Chinese societal risks In fact the personaleffective dose control threshold is 50mSv and actual CPEFh

is extremely low as well so the risk metric of HTR-PM haslarge margin compared with Chinese societal risk(ereforeit give us the confidence to expand the risk metric of HTR-PM (ie 1 times 10minus 6reactor middot y) to multimodule HTGR (ie1 times 10minus 6(unit middot y) or 1 times 10minus 6(site middot ley)) and then therisk metric of multimodule HTGR can meet the require-ments of Chinese societal risks

4 Discussions

Existing nuclear safety goals is mainly for a single reactorBut in fact most of the plant sites are multireactor sitesMultireactor site means a nuclear power plant site with twoor more reactors on one site From the Fukushima nuclearaccident we realized the possibility and severity of nuclearaccidents occurring at multiple reactors at the same timeNuclear safety goals are set to protect the lives health andenvironment of populations For the populations not onlythe impact of a single reactor on the human body must beconsidered but also the impact of the entire plant site on thehuman body

For example expand the risk metric of HTR-PM from asingle reactor to a plant site and explore the adaptability ofprobabilistic safety goals (e current probabilistic safetygoals of HTR-PM are that the cumulative frequency of allaccident sequences that cause the personal effective dose

Table 3 Demographic mortality statistics in China based on theWHO data

Mortality rate (1100000) 2000 2010 2015 2016Cardiovascular diseases 2128 2696 3095 3171Malignant neoplasms 1444 1599 1663 1679Respiratory diseases 975 712 659 665External causes of damage andpoisoning 607 540 509 512

Neurological condition 206 323 420 449Digestive diseases 183 174 192 197Genitourinary diseases 98 123 149 152Respiratory infectious 192 126 124 126Diabetes mellitus 77 97 116 119Infectious and parasitic diseases 186 120 96 92Neonatal conditions 180 80 54 49Mental and substance use disorders 21 26 31 32Congenital anomalies 67 46 33 31Other neoplasms 15 24 29 29Endocrine blood and immunedisorders 15 14 17 17

Musculoskeletal diseases 11 13 15 15Nutritional deficiencies 14 09 11 11Skin diseases 03 04 05 05Sudden infant death syndrome 01 01 01 01Source World Health Organization statistics [23] Note External causes ofinjury and poisoning include road injury poisonings falls fire heat and hotsubstances drowning exposure to mechanical forces natural disastersother unintentional injuries self-harm interpersonal violence collectiveviolence and legal intervention

Science and Technology of Nuclear Installations 7

outside the plant (including the site boundary) to exceed50mSv is less than 10minus 6(r middot y) Expanding from a singlereactor to a plant site means LARGE 10minus 6(reactor middot year)changed to LARGE 10minus 6(site middot year) (sitemiddotyear smiddoty)

(rough the derivation in Section 4LARGE 10minus 6(s middot y) then CPEFh 05 (at is theconditional probability of early prompt fatalities caused bythe worst accident sequence h in the entire plant site is 05 it

just meets the EQHO for individual early prompt fatalitiesrsquorisks

Suppose there are two reactors in a plant site andsuppose that the two reactors suffer the worst accident se-quence at the same time In order to ensure the probabilisticsafety goals of the multimodule HTGR site and ensure asufficient safety margin it is necessary to ensure the cu-mulative frequency of beyond design basis accidents with a

Table 4 Demographic mortality statistics in different countries

Mortality rate (1100000) China (e US Japan (e UK France India Egypt SudanAll causes 7349 8698 10260 9124 8616 7226 6359 7123Cardiovascular diseases 3171 2599 2808 2287 2216 1956 2570 2029Malignant neoplasms 1679 1948 3129 2557 2679 616 812 446Respiratory diseases 665 767 901 760 480 768 271 221Injuries 512 570 497 318 548 818 367 896Neurological conditions 449 1021 418 1499 995 158 221 163Digestive diseases 197 367 453 435 384 385 834 209Genitourinary diseases 152 267 347 161 164 230 197 198Respiratory infectious diseases 126 206 1107 571 277 466 231 482Diabetes mellitus 119 262 113 100 191 233 187 146Infectious and parasitic diseases 92 175 170 101 154 906 124 1011Neonatal conditions 46 36 05 25 24 415 268 894Mental and substance use disorders 32 149 18 57 92 24 06 16Congenital anomalies 31 40 22 35 30 79 151 180Other neoplasms 29 51 99 60 118 11 38 32Endocrine blood and immune disorders 17 141 82 48 108 16 52 54Musculoskeletal diseases 15 45 52 70 67 37 02 07Nutritional deficiencies 11 30 25 06 65 63 14 34Skin diseases 05 16 15 31 21 10 01 08Maternal conditions 03 02 00 01 01 31 09 90Sudden infant death syndrome 01 05 01 02 02 04 06 09Sense organ diseases 00 00 01 01 Oral conditions 01 01 01 02 00 Source World Health Organization statistics [23]

Table 5 (e mortality rate of malignant neoplasms and external causes in the US

Mortality rate (1100000) 1978 1979 1980 1981 1982 1983 1984 1985Malignant neoplasms 1617 1754 1795 1802 1836 1859 1887 1905External causes 707 706 707 678 638 616 615 612Source World Health Organization statistics [23]

Table 6 (e mortality rate of malignant neoplasms and external causes in China (1)

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017 AverageMalignant neoplasms 1583 1526 1574 1598 1583 1591 1576External causes 462 474 457 446 447 432 453

Table 7 (e mortality rate of malignant neoplasms and external causes in China (2)

Mortality rate (1100000) 2016 2015 2010 2000 AverageMalignant neoplasms 1679 1663 1599 1444 1596External causes 512 509 540 607 542

8 Science and Technology of Nuclear Installations

personal effective dose exceeding 502 25mSv for eachreactor is less than 10minus 62 5 times 10minus7(r middot y)

In fact the individual effective dose and cumulativefrequency caused by the entire plant site are not necessarilythe simple addition of the individual effective dose andcumulative frequency caused by each single reactor How-ever in order to ensure the probabilistic safety goals thevalue of the probabilistic safety goals of each single reactor issmaller than the entire plant site We need to consider thefollowing points

(a) (e safety and reliability of a single reactor is con-stant (e number of reactors on the site needs to becontrolled and cannot be increased indefinitely

(b) (e design of the reactors can still be based on thesingle reactor for the convenience of design But forthe entire plant site we can consider different typesof reactors with different risk levels at the same site

5 Conclusions

According to the statistics on societal risks in China theindividual latent cancer fatality risk (ILCFR) is 16 times 10minus 3yand the individual early prompt fatality risk (IEPFR) is5 times 10minus 4y (e mortality rates are similar in China and theUnited States and the changes in recent years are small (eChinese current probabilistic safety goals can meet the re-quirement of little contribution to social risks

(e probabilistic safety goals of HTR-PM recom-mended by Chinarsquos National Nuclear Safety Adminis-tration (NNSA) are as follows the cumulative frequencyof all beyond-design-basis accident sequences that lead tooff-site (including plant boundary) personal effective doseexceeding 50mSv shall be less than 10minus 6(r middot y) Accordingto the inference the probabilistic safety goals are rationalAnd the risk metric of HTR-PM has large marginaccording to the societal risk of China maybe it can beextended to be applied to the multimodule HTGR asldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y)rdquo

In the end we think it is better that the probabilisticsafety goals based on entire plant site rather than a single

reactor We need to control the number of reactors on onesite and we can consider different types of reactors withdifferent risk levels at the same site And the above analysisprocess is applicable to other types of reactors

Data Availability

(e data used in this paper are obtained from China Na-tional Bureau of Statistics (httpwwwstatsgovcn) andWorld Health Organization (httpswwwwhointdatacollections)

Conflicts of Interest

(e authors declare that they have no conflicts of interestregarding the publication of this paper

Acknowledgments

(is study was supported by the National Science andTechnology Major Project (2018ZX06902015) and the Na-tional Natural Science Foundation of China (Project no71601139)

References

[1] C Meyer ldquoChina and nuclear energy solving an energycrisisndashpart 4rdquo Energize vol 7 no 42 pp 18-19 2011

[2] J Wood ldquoNuclear safety and three major accidentsrdquo NuclearPower IET Digital Library vol 18 no 6 2007

[3] OECDNEA Probabilistic Risk Criteria and Safety GoalsNEACSNIR Organization for Economic Cooperation andDevelopmentNuclear Energy Agency (OECDNEA) ParisFrance 2009

[4] Z Zhang Z Wu and Y Sun ldquoDesign aspects of the Chinesemodular high-temperature gas-cooled reactor HTR-PMrdquoNuclear Engineering amp Design vol 236 no 5-6 pp 485ndash4902006

[5] IAEA ldquoPolicy for setting and assessing regulatory safetygoalsrdquo 1995

[6] EPRI ldquoAdvanced light water reactor utility requirementsdocumentrdquo ALWR Policy and Summary of Top-Tier Re-quirements vol 1 1990

[7] K R KEMA ldquoEuropean utility requirements for LWR nuclearpower plantsrdquo Main Policies and Top Tier RequirementsRevision B vol 1 1995

[8] GPR-RSK ldquoIPSN-GRS proposals for the development oftechnical guideline for future pWRsrdquo 1997

[9] IAEA Safety Series 75-INSAG-3 Basic Safety Principles forNuclear Power Plants IAEA 1988 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

[10] IAEA Safety Series 75-INSAG-12 Basic Safety Principles forNuclear Power Plants IAEA 1999 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

Chinese societal risks

IEPFR 50E ndash 4y

ILCFR 16E ndash 3y

Risks based on quantitativehealth objectives

01 01

Probabilistic safety goals

LERF lt 1E ndash 6(rmiddoty)

CDF lt 1E ndash 5(rmiddoty)

IEPFRNPP 50E ndash 7y

ILCFRNPP 16E ndash 6y

IEPFRNPP 30E ndash 8y

ILCFRNPP 40E ndash 8y

Risks based on probabilisticsafety goals

IER ILR

gt

gt

Figure 3 (e rationality of existing probabilistic safety goals inChina

Science and Technology of Nuclear Installations 9

NRC formulated a draft nuclear safety goals policy statementbased on the results of expert seminars [13] In 1983 theNRC issued a formal nuclear safety goals policy statementbased on the results of discussions in various industries [14]In 1986 the NRC issued a final nuclear safety goals policystatement and provided two qualitative safety goals and twoquantitative safety goals [15]

Individual qualitative safety goal (IQSG) means promptfatalities risks to an average individual in the vicinity of anuclear power plant caused by reactor accidents Societalqualitative safety goal (SQSG) means cancer fatalities to thepopulation in the area of a nuclear power plant caused bynuclear power plant operation Because the qualitative safetygoal cannot be used to guide the design and operation ofnuclear power plant (NPP) two quantitative safety goalshave been proposed based on the two 01 rule whichinclude early quantitative health objective (EQHO) andlatent quantitative health objective (LQHO)(e EQHO andLQHO have been derived from the societal risk of Americathat is the risk to residents of NPP cannot exceed otherexisting societal risks obviously this is the so-called ldquotwo01 rulerdquo (e risk to the average individual in the vicinityof a nuclear power plant of prompt fatalities that mightresult from reactor accidents should not exceed 01 of thesum of prompt fatality risks resulting from other accidents towhich members of the US population are generally exposed(e risk to the population in the area near a nuclear powerplant of cancer fatalities that might result from nuclearpower plant operation should not exceed 01 of the sum ofcancer fatality risks resulting from all other causes [15]

CDF and LERF as subsidiary safety goals used to besurrogate safety goals of LQHO and EQHO respectivelysince the applicability of quantitative safety goals is still poor(e unit of CDF and LERF is per reactor year (rmiddoty) (e unitof the individual fatality risk is per year (y) Based on thelater assessments of the sites surrounding environment and

demographic conditions of nuclear power plants in the USCDFlt 10minus 4(r middot y) and LERFlt 10minus 5(r middot y) meet the 01and 01 quantitative safety goals (e relationship amongnuclear safety goals in the US is shown in Figure 2 (equantitative safety goals (IQSG and SQSG) mean that theoperation of nuclear power plants will not cause obviousadditional risks to the life and health of the public Quali-tative safety goals (EQHO and LQHO) are measuredachieved through quantitative safety goals Subsidiary safetygoals (LERF and CDF) make quantitative safety goals morespecific and easier to implement

222 LERF and EQHO [20] LERFlt 10minus 5(r middot y) is a sub-sidiary goal of early quantitative health objectives (EQHO)for early prompt fatalities (e rationality of substitutingLERF for EQHO is demonstrated as follows

According to the data survey for nuclear safety goals theindividual risk of prompt fatality caused by all other acci-dents is 5 times 10minus 4y in the US (ese accidents include trafficaccidents production accidents and other accidentsAccording to the 01 in the early quantitative health ob-jective (EQHO) the individual early risk (IEREQHO) causedby nuclear power plant accidents need to be less than5 times 10minus 7(r middot y) (e vicinity of a nuclear power plant meansan extension of 1 mile from the boundary of the nuclearpower plant Individual early risk (IER) is

IER 1113944M

1

EFm lowast LERFm( 1113857

TP(1) (1)

where EFm is the number of early prompt fatalities within 1mile caused by accident sequencem LERFm is the frequencyof fatal early large release caused by accident sequence mand TP(1) is the total population within 1mile of the nuclearpower plant

Protection and prevention

Qualitative safety goal

Quantitative safety goal

Subsidiary safety goal

Defensendashinndashdepth

General safety goalradiation protection goal

technical safety goal

CDF LRF

Adequate protection

Life health society

Quantitative health objective01 and 01

CDF LRF

Nuclear safety goal Nuclear safety goal

As low as possible

Figure 1 Nuclear safety goal systems in China and the United States

Science and Technology of Nuclear Installations 3

(en in the population TP(1) the number of earlyprompt fatalities caused by accident sequence m is given by

EFm CPEFm lowastTP(1) (2)

CPEFm is the conditional probability of early promptfatalities caused by accident sequence m meaning theconditional probability of one personrsquos early fatality causedby a radioactive release nuclear accident

According to formulae (1) and (2) the individual earlyprompt fatality risk is

IER 1113944M

1CPEFm lowast LERFm (3)

Suppose a worst accident sequence m which has thegreatest impact on early prompt fatalities risk (is accidentsequencem corresponds to a large break in the containmentand an unscrubbed release occurred before the surroundingpopulation were effectively evacuated According to theSurry PRA in NUREG-1150 the CPEF of the worst accidentsequence is 3 times 10minus 2

Put CPEF 3 times 10minus 2 and the safety goal value LERF

1 times 10minus 5(r middot y) into formula (3) (en when the worstaccident sequence m occurs the individual early promptfatality risk is

IERm 3 times 10minus 21113872 1113873 times 10minus 5

1113872 1113873 3 times 10minus 7(r middot y)lt IEREQHO

5 times 10minus7(r middot y)

(4)

(erefore using LERFlt 10minus 5(r middot y) as a subsidiary goalof early quantitative health objectives (EQHO) for earlyprompt fatalities is acceptable

223 CDF and QHO [20] CDFlt 10minus 4(r middot y) is a subsid-iary goal of latent quantitative health objectives (LQHO) forlatent cancer fatalities (e rationality of substituting CDFfor LQHO is demonstrated as follows

According to the data survey for nuclear safety goals theindividual risk of cancer fatality from all other causes is 2 times

10minus 3y in the US According to the 01 in the latentquantitative health objective (LQHO) the individual latentrisk (ILRLQHO) caused by nuclear power plant operationsneed to be less than 2 times 10minus 6(r middot y) (e area of a nuclearpower plant means an extension of 10 mile from the

boundary of the nuclear power plant Individual latent risk(ILR) is

ILR 1113944N

1

LFn lowast LLRFn( 1113857

TP(10) (5)

where LFn is the number of latent cancer fatalities within 10miles caused by accident sequence n LLRFn is the frequencyof cancerogenic off-site individual doses caused by accidentsequence n and TP(10) is the total population within 10miles of the nuclear power plant

(en in the population TP(10) the number of latentcancer fatalities caused by accident sequence n is given by

LFn CPLFn lowastTP(10) (6)

where CPLFn is the conditional probability of latent cancerfatalities caused by accident sequence n

According to formulae (5) and (6) the individual latentcancer risk is

ILR 1113944N

1CPLFn lowast LLRFn (7)

Suppose a worst accident sequence n which has thegreatest impact on latent cancer fatalities risk (is accidentsequence n corresponds to a large opening in the con-tainment and an unscrubbed release occurred after thesurrounding population were effectively evacuated Supposethe worst accident occurs in an open containment theconditional large latent release probability for accident se-quence n (CLLRPn) is 10

(en

LLRFn CDFn lowastCLLRPn CDFn lowast 10 CDFn (8)

Putting formula (8) into formula (7) the risk of indi-vidual latent cancer fatality risk is

ILRn CPLFn lowastCDFn (9)

According to the Surry PRA in NUREG-1150 the CPLFof the worst accident sequence is 4 times 10minus 3

Put CPLF 4 times 10minus 3 and the safety goal value CDF

1 times 10minus 4(r middot y) into formula (6) (en when the worstaccident sequence n occurs the individual latent cancerfatality risk is

ILRn 4 times 10minus 31113872 1113873 times 10minus 4

1113872 1113873 4 times 10minus 7(r middot y)lt ILRLQHO

2 times 10minus6(r middot y)

(10)

(erefore using CDFlt 10minus 4(r middot y) as a subsidiary goalof latent quantitative health objectives (LQHO) for latentcancer fatalities is acceptable

3 Investigation into Chinese Societal Risk

According to the process of determining probabilistic safetygoals of USNRC probabilistic safety goals are based onsocietal risks Chinese current probabilistic safety goals refer

Qualitative safety goals

Quantitative safety goals

Subsidiary objectives

IQSG

EQHO

LERF

SQSG

LQHO

CDF

Figure 2 (e relationship among nuclear safety goals in the US

4 Science and Technology of Nuclear Installations

to NRC and IAEA and they are not based on Chinesesocietal risks (erefore we need to investigate the Chinesesocietal risks firstly and then formulate and verify proba-bilistic safety goals based on Chinese societal risks

(e data about the societal risk (ie mortality rate) canbe obtained from the Chinese government and internationalorganizations Chinese statistics include the National Eco-nomic and Societal Development Statistical Bulletin andChinarsquos Health Statistical Yearbook [21 22] Internationalorganizationsrsquo statistics include World Health Organiza-tionrsquos data [23] and World Bankrsquos data [24]

According to the contents of probabilistic safety goalswe focus on early prompt fatalities and latent cancer fatalitiescaused by nuclear power plant operation which can berepresented by accident mortality and cancer mortality insociety respectively

In this section the general overview of Chinese societywas investigated firstly including the analysis about maincauses of fatalities in Chinese society and then make acomparison between the death rate of China and severalother countries

31 Main Causes of Fatalities in China (e total populationof China the number of deaths the number of urban andrural residents and the GDP from 2012 to 2017 are shown inTable 1

(e mortality rates of different causes were countedrespectively when counting the main causes of fatalities ofChinese population (en the causes of death were sortedaccording to the value of mortality (e source data arederived from the Chinese government and internationalorganizations and the statistical results were compared toensure the authenticity of the data Statistics from theChinese government (2012ndash2017) are shown in Table 2Statistics from international organizations (2000 2010 2015and 2016) are shown in Table 3

(e causes of fatalities of Chinese population werecounted based on the source data from Chinese governmentand international organizations as shown above Accordingto the comparison of the above data the difference betweenthe data obtained through the two channels is small whichproves that the statistics are true and reliable (e maincauses of fatalities of Chinese population include malignantneoplasms cerebrovascular diseases heart diseases respi-ratory diseases and external causes of damage andpoisoning

32 Main Causes of Fatalities in Other Countries It is nec-essary to investigate other countriesrsquo societal risks andcompare the results with Chinese societal risks On the onehand the authenticity and reliability of the data can beproved through comparative analysis On the other handinvestigating more countriesrsquo societal risks can help us toprovide further suggestions for nuclear safety goals based onsocietal risks China the United States Japan the UnitedKingdom France India Egypt and Sudan were selected asthe research object countries according to the developmentstatus and the level of nuclear power in each country (e

causes of death and mortality in these countries in 2016 werecounted and the results are shown in Table 4

According to the statistical data from international or-ganizations the causes of death and mortality of China theUnited States Japan the United Kingdom France IndiaEgypt and Sudan in 2016 were counted According to thecomparisons of the causes of death and mortality of Chinaand the US the societal fatalitiesrsquo risks in China and in theUS are similar For example the mortality rates caused bycardiovascular diseases malignant neoplasms respiratorydiseases and injuries are 31710 16788 6647 and 5115 inChina and 25987 19483 7665 and 5698 in the US Forprobabilistic safety goals we focus on the mortality rate ofmalignant neoplasms and external causes which are similarbetween China and the US as well

Furthermore the nuclear safety goals of the US wereformulated and revised from 1979 to 1986 According todata from international organizations the mortality rate ofmalignant neoplasms and external causes in the UnitedStates from 1978 to 1985 were counted and the results areshown in Table 5

According to the statistical data in the table the mor-tality rate of malignant neoplasms and external causes in theUnited States has not changed much from 1978 to 1985 andthey are similar to the current risks of malignant neoplasmsand external causes in China

33 Probabilistic Safety Goals of Multimodule HTGRHigh-temperature gas-cooled reactors are extremely un-likely to cause serious core damage and large early releasedue to inherent safety and unique design concepts CDF andLERF proposed for water-cooled reactor are not suitable forhigh-temperature gas-cooled reactor (erefore the prob-abilistic safety goal of HTR-PM has been reestablished byChina National Nuclear Safety Administration (NASA) thatis ldquothe cumulative frequency of all beyond design basisaccident sequences that lead to off-site (including plantboundary) personal effective dose exceeding 50mSv shall beless than 10minus 6(r middot y)rdquo and this risk metric is defined as theldquofrequency of LARGE release categoryrdquo in HTR-PM prob-abilistic safety analysis (PSA) model In this section weverified the rationality of Chinese existing probabilisticsafety goals for water reactors and then studied the prob-abilistic safety goals for Chinese high-temperature gas-cooled reactors

34ChineseExistingProbabilistic SafetyGoals (emortalityrate of malignant neoplasms and external causes are im-portant basis when verifying the rationality of Chineseexisting CDF and LERF based on the current societal risks inChina According to the above statistics on Chinese societalrisks the statistical results of the mortality rate of malignantneoplasms and external causes are as follows Statistics basedon data from the Chinese government are shown in Table 6and statistics based on data from international organizationsare shown in Table 7

According to the data from the Chinese government andinternational organizations shown in Tables 6 and 7 the

Science and Technology of Nuclear Installations 5

individual latent cancer fatality risk (ILCFR) is about16 times 10minus 3y and the individual early prompt fatality risk(IEPFR) is about 5 times 10minus 4y

According to the Chinese societal risks the reasonabilityof existing probabilistic safety goals in China is shown inFigure 3 Based on the Chinese societal risks and quantitativesafety goals (ldquotwo 01 rulerdquo) the individual latent cancerfatality risk caused by nuclear power plant operation(ILCFRNPP) should be less than 16 times 10minus 6y and the in-dividual early prompt fatality risk caused by nuclear powerplant accidents (IEPFRNPP) should be less than 5 times 10minus 7yBased on the subsidiary safety goals and the assessment ofnuclear power plant the ILCFRNPP is less than 4 times 10minus 8yand the IEPFRNPP is less than 3 times 10minus 8y As shown aboveChinese current probabilistic safety goals can meet the needsof Chinese societal risks control

35 Probabilistic Safety Goals of Multimodule HTGR (edesign characteristics and defense-in-depth measures ofmultimodule HTGR nuclear power plants are differentfrom those of water reactor nuclear power plants Due tothe safety design concept inherent safety and passive

safety measures there is extremely low large release fre-quency and longer time before radioactive material is re-leased into the environment So there is longer time forpostaccident mitigation and emergency response allowingmore measures to actually eliminate core damage and largeearly release (erefore it uses the ldquofrequency of LARGErelease categoryrdquo defined in HTGR PSA as the risk indexrather than the CDF or LERF According to the risk metricof HTR-PM it should be less than 10minus 6(r middot y) However itshould be noted that this safety goal is dedicated to HTR-PM project and it is focused on single reactor rather thanunit (two reactors and one turbine) (erefore this papertries to study whether this risk metric can be extended to beapplied to the multimodule HTGR that is can we use theldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y) as the risk metric ofmultimodule HTGR directly

In the following we will use the risk metric of HTR-PMto demonstrate the margin of probabilistic safety goal

(e ldquoLARGErdquo release category of HTR-PM is similarto the LERF of water reactors and it focuses on earlyprompt fatalities risks and EQHO Individual early risk(IER) is

Table 1 General overview of Chinese Society

Year Total population (rsquo0000) Dead population (rsquo0000) Urban population (rsquo0000) Rural population (rsquo0000) GDP (100 million)2012 135404 966 71182 64222 5193222013 136072 972 73111 62961 5688452014 136782 977 74916 61866 6364632015 137462 975 77116 60346 6767082016 138271 977 79298 58973 7441272017 139008 986 81347 57661 827122Source National Economic and Societal Development Statistical Bulletin [22]

Table 2 Demographic mortality statistics in China based on Chinese data

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017Malignant neoplasms 1583 1526 1574 1598 1583 1591Cerebrovascular diseases 1277 1370 1376 1394 1400 1394Heart diseases 1259 1383 1396 1402 1440 1469Respiratory diseases 890 760 768 763 744 719External causes of damage and poisoning 462 474 457 446 447 432Other diseases 264 82 68 62 61 60Digestive diseases 160 155 145 142 142 145Endocrine nutritional and metabolic diseases 142 146 156 171 184 188Infectious 69 74 72 72 70 67Neurological conditions 66 68 68 67 75 77Genitourinary diseases 65 67 69 68 69 71Mental disorders 25 28 27 28 28 27Acatalepsia 23 25 25 23 22 21Neonatal conditions 23 22 23 19 20 17Congenital anomalies and chromosomal abnormalities 20 21 20 18 16 16Musculoskeletal diseases 14 17 17 17 20 21Blood hematopoietic organ and immune disorders 12 12 12 12 13 13Complications of pregnancy childbirth and puerperium 01 01 01 01 01 01Parasitic diseases 01 01 00 01 01 01Source Chinarsquos Health Statistical Yearbook [21] Note External causes of injury and poisoning include traffic accidents poisoning falls fires naturaldisasters mechanical asphyxiation suicide homicide and mechanical injuries

6 Science and Technology of Nuclear Installations

IER 1113944H

1

EFh lowast LARGEh( 1113857

TP(1) (11)

where EFh is the number of early prompt fatalities within 1mile caused by accident sequence h LARGEh is the fre-quency of fatal LARGE categories caused by accident se-quence h TP(1) is the total population within 1 mile of thenuclear power plant

(en in the population TP(1) the number of earlyprompt fatalities caused by accident sequence h is

EFh CPEFh lowastTP(1) (12)

where CPEFh is the conditional probability of early promptfatalities caused by accident sequence h meaning the con-ditional probability of one personrsquos early fatality caused by aradioactive release nuclear accident

According to formulae (9) and (10) the individual earlyprompt fatality risk is

IER 1113944H

1CPEFh lowast LARGEh (13)

According to the data survey for Chinese societal risksthe individual risk of prompt fatality caused by all otheraccidents is 5 times 10minus 4y in China According to the 01 inthe early quantitative health objective (EQHO) the indi-vidual early risk (IEREQHO) caused by nuclear power plantaccidents needs to be less than 5 times 10minus 7(r middot y) Suppose aworst accident sequence h which has the greatest impact onearly prompt fatalities risk An unscrubbed release occurred

before the surrounding population were effectivelyevacuated

Suppose

IERh CPEFh lowast LARGEh IEREQHO 5 times 10minus 7

(r middot y) (14)

According to the probabilistic safety goals for multi-HTGR LARGEh 1 times 10minus 6(r middot y)

(us CPEFh 05(at is the conditional probability of early prompt fa-

talities caused by the worst accident sequence h is 05 it justmeets the EQHO for individual early prompt fatalities risks

In the International Commission on Radiological Pro-tection (ICPR) Publication 60 according to the dosethreshold of the deterministic effects the 60-day medianlethal dose (LD50[60]) is 3sim5Gytime (e probability ofstochastic effects increases with increasing dose Stochasticeffects include cancer and hereditary diseases For cancerthe probability coefficients of fatal cancer are 5 times 10minus 2Sv forthe public and 4 times 10minus 2Sv for occupational workers en-gaged in radiation For hereditary diseases the probabilitycoefficients of hereditary diseases are 1 times 10minus 2Sv for thepublic and 06 times 10minus 2Sv for workers ICPR 103 followed theconclusion of the ICRP 60 the combined detriment due tofatal cancer and hereditary diseases remains unchanged ataround 5 times 10minus 2Sv For HTR-PM there is extremely lowlarge release frequency and the personal effective dosecontrol threshold is 50mSv According to the results ofabove analysis when LARGEh 1 times 10minus 6(r middot y)andCPEFh 05 the risk metric of HTR-PM can meet the re-quirements of Chinese societal risks In fact the personaleffective dose control threshold is 50mSv and actual CPEFh

is extremely low as well so the risk metric of HTR-PM haslarge margin compared with Chinese societal risk(ereforeit give us the confidence to expand the risk metric of HTR-PM (ie 1 times 10minus 6reactor middot y) to multimodule HTGR (ie1 times 10minus 6(unit middot y) or 1 times 10minus 6(site middot ley)) and then therisk metric of multimodule HTGR can meet the require-ments of Chinese societal risks

4 Discussions

Existing nuclear safety goals is mainly for a single reactorBut in fact most of the plant sites are multireactor sitesMultireactor site means a nuclear power plant site with twoor more reactors on one site From the Fukushima nuclearaccident we realized the possibility and severity of nuclearaccidents occurring at multiple reactors at the same timeNuclear safety goals are set to protect the lives health andenvironment of populations For the populations not onlythe impact of a single reactor on the human body must beconsidered but also the impact of the entire plant site on thehuman body

For example expand the risk metric of HTR-PM from asingle reactor to a plant site and explore the adaptability ofprobabilistic safety goals (e current probabilistic safetygoals of HTR-PM are that the cumulative frequency of allaccident sequences that cause the personal effective dose

Table 3 Demographic mortality statistics in China based on theWHO data

Mortality rate (1100000) 2000 2010 2015 2016Cardiovascular diseases 2128 2696 3095 3171Malignant neoplasms 1444 1599 1663 1679Respiratory diseases 975 712 659 665External causes of damage andpoisoning 607 540 509 512

Neurological condition 206 323 420 449Digestive diseases 183 174 192 197Genitourinary diseases 98 123 149 152Respiratory infectious 192 126 124 126Diabetes mellitus 77 97 116 119Infectious and parasitic diseases 186 120 96 92Neonatal conditions 180 80 54 49Mental and substance use disorders 21 26 31 32Congenital anomalies 67 46 33 31Other neoplasms 15 24 29 29Endocrine blood and immunedisorders 15 14 17 17

Musculoskeletal diseases 11 13 15 15Nutritional deficiencies 14 09 11 11Skin diseases 03 04 05 05Sudden infant death syndrome 01 01 01 01Source World Health Organization statistics [23] Note External causes ofinjury and poisoning include road injury poisonings falls fire heat and hotsubstances drowning exposure to mechanical forces natural disastersother unintentional injuries self-harm interpersonal violence collectiveviolence and legal intervention

Science and Technology of Nuclear Installations 7

outside the plant (including the site boundary) to exceed50mSv is less than 10minus 6(r middot y) Expanding from a singlereactor to a plant site means LARGE 10minus 6(reactor middot year)changed to LARGE 10minus 6(site middot year) (sitemiddotyear smiddoty)

(rough the derivation in Section 4LARGE 10minus 6(s middot y) then CPEFh 05 (at is theconditional probability of early prompt fatalities caused bythe worst accident sequence h in the entire plant site is 05 it

just meets the EQHO for individual early prompt fatalitiesrsquorisks

Suppose there are two reactors in a plant site andsuppose that the two reactors suffer the worst accident se-quence at the same time In order to ensure the probabilisticsafety goals of the multimodule HTGR site and ensure asufficient safety margin it is necessary to ensure the cu-mulative frequency of beyond design basis accidents with a

Table 4 Demographic mortality statistics in different countries

Mortality rate (1100000) China (e US Japan (e UK France India Egypt SudanAll causes 7349 8698 10260 9124 8616 7226 6359 7123Cardiovascular diseases 3171 2599 2808 2287 2216 1956 2570 2029Malignant neoplasms 1679 1948 3129 2557 2679 616 812 446Respiratory diseases 665 767 901 760 480 768 271 221Injuries 512 570 497 318 548 818 367 896Neurological conditions 449 1021 418 1499 995 158 221 163Digestive diseases 197 367 453 435 384 385 834 209Genitourinary diseases 152 267 347 161 164 230 197 198Respiratory infectious diseases 126 206 1107 571 277 466 231 482Diabetes mellitus 119 262 113 100 191 233 187 146Infectious and parasitic diseases 92 175 170 101 154 906 124 1011Neonatal conditions 46 36 05 25 24 415 268 894Mental and substance use disorders 32 149 18 57 92 24 06 16Congenital anomalies 31 40 22 35 30 79 151 180Other neoplasms 29 51 99 60 118 11 38 32Endocrine blood and immune disorders 17 141 82 48 108 16 52 54Musculoskeletal diseases 15 45 52 70 67 37 02 07Nutritional deficiencies 11 30 25 06 65 63 14 34Skin diseases 05 16 15 31 21 10 01 08Maternal conditions 03 02 00 01 01 31 09 90Sudden infant death syndrome 01 05 01 02 02 04 06 09Sense organ diseases 00 00 01 01 Oral conditions 01 01 01 02 00 Source World Health Organization statistics [23]

Table 5 (e mortality rate of malignant neoplasms and external causes in the US

Mortality rate (1100000) 1978 1979 1980 1981 1982 1983 1984 1985Malignant neoplasms 1617 1754 1795 1802 1836 1859 1887 1905External causes 707 706 707 678 638 616 615 612Source World Health Organization statistics [23]

Table 6 (e mortality rate of malignant neoplasms and external causes in China (1)

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017 AverageMalignant neoplasms 1583 1526 1574 1598 1583 1591 1576External causes 462 474 457 446 447 432 453

Table 7 (e mortality rate of malignant neoplasms and external causes in China (2)

Mortality rate (1100000) 2016 2015 2010 2000 AverageMalignant neoplasms 1679 1663 1599 1444 1596External causes 512 509 540 607 542

8 Science and Technology of Nuclear Installations

personal effective dose exceeding 502 25mSv for eachreactor is less than 10minus 62 5 times 10minus7(r middot y)

In fact the individual effective dose and cumulativefrequency caused by the entire plant site are not necessarilythe simple addition of the individual effective dose andcumulative frequency caused by each single reactor How-ever in order to ensure the probabilistic safety goals thevalue of the probabilistic safety goals of each single reactor issmaller than the entire plant site We need to consider thefollowing points

(a) (e safety and reliability of a single reactor is con-stant (e number of reactors on the site needs to becontrolled and cannot be increased indefinitely

(b) (e design of the reactors can still be based on thesingle reactor for the convenience of design But forthe entire plant site we can consider different typesof reactors with different risk levels at the same site

5 Conclusions

According to the statistics on societal risks in China theindividual latent cancer fatality risk (ILCFR) is 16 times 10minus 3yand the individual early prompt fatality risk (IEPFR) is5 times 10minus 4y (e mortality rates are similar in China and theUnited States and the changes in recent years are small (eChinese current probabilistic safety goals can meet the re-quirement of little contribution to social risks

(e probabilistic safety goals of HTR-PM recom-mended by Chinarsquos National Nuclear Safety Adminis-tration (NNSA) are as follows the cumulative frequencyof all beyond-design-basis accident sequences that lead tooff-site (including plant boundary) personal effective doseexceeding 50mSv shall be less than 10minus 6(r middot y) Accordingto the inference the probabilistic safety goals are rationalAnd the risk metric of HTR-PM has large marginaccording to the societal risk of China maybe it can beextended to be applied to the multimodule HTGR asldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y)rdquo

In the end we think it is better that the probabilisticsafety goals based on entire plant site rather than a single

reactor We need to control the number of reactors on onesite and we can consider different types of reactors withdifferent risk levels at the same site And the above analysisprocess is applicable to other types of reactors

Data Availability

(e data used in this paper are obtained from China Na-tional Bureau of Statistics (httpwwwstatsgovcn) andWorld Health Organization (httpswwwwhointdatacollections)

Conflicts of Interest

(e authors declare that they have no conflicts of interestregarding the publication of this paper

Acknowledgments

(is study was supported by the National Science andTechnology Major Project (2018ZX06902015) and the Na-tional Natural Science Foundation of China (Project no71601139)

References

[1] C Meyer ldquoChina and nuclear energy solving an energycrisisndashpart 4rdquo Energize vol 7 no 42 pp 18-19 2011

[2] J Wood ldquoNuclear safety and three major accidentsrdquo NuclearPower IET Digital Library vol 18 no 6 2007

[3] OECDNEA Probabilistic Risk Criteria and Safety GoalsNEACSNIR Organization for Economic Cooperation andDevelopmentNuclear Energy Agency (OECDNEA) ParisFrance 2009

[4] Z Zhang Z Wu and Y Sun ldquoDesign aspects of the Chinesemodular high-temperature gas-cooled reactor HTR-PMrdquoNuclear Engineering amp Design vol 236 no 5-6 pp 485ndash4902006

[5] IAEA ldquoPolicy for setting and assessing regulatory safetygoalsrdquo 1995

[6] EPRI ldquoAdvanced light water reactor utility requirementsdocumentrdquo ALWR Policy and Summary of Top-Tier Re-quirements vol 1 1990

[7] K R KEMA ldquoEuropean utility requirements for LWR nuclearpower plantsrdquo Main Policies and Top Tier RequirementsRevision B vol 1 1995

[8] GPR-RSK ldquoIPSN-GRS proposals for the development oftechnical guideline for future pWRsrdquo 1997

[9] IAEA Safety Series 75-INSAG-3 Basic Safety Principles forNuclear Power Plants IAEA 1988 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

[10] IAEA Safety Series 75-INSAG-12 Basic Safety Principles forNuclear Power Plants IAEA 1999 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

Chinese societal risks

IEPFR 50E ndash 4y

ILCFR 16E ndash 3y

Risks based on quantitativehealth objectives

01 01

Probabilistic safety goals

LERF lt 1E ndash 6(rmiddoty)

CDF lt 1E ndash 5(rmiddoty)

IEPFRNPP 50E ndash 7y

ILCFRNPP 16E ndash 6y

IEPFRNPP 30E ndash 8y

ILCFRNPP 40E ndash 8y

Risks based on probabilisticsafety goals

IER ILR

gt

gt

Figure 3 (e rationality of existing probabilistic safety goals inChina

Science and Technology of Nuclear Installations 9

(en in the population TP(1) the number of earlyprompt fatalities caused by accident sequence m is given by

EFm CPEFm lowastTP(1) (2)

CPEFm is the conditional probability of early promptfatalities caused by accident sequence m meaning theconditional probability of one personrsquos early fatality causedby a radioactive release nuclear accident

According to formulae (1) and (2) the individual earlyprompt fatality risk is

IER 1113944M

1CPEFm lowast LERFm (3)

Suppose a worst accident sequence m which has thegreatest impact on early prompt fatalities risk (is accidentsequencem corresponds to a large break in the containmentand an unscrubbed release occurred before the surroundingpopulation were effectively evacuated According to theSurry PRA in NUREG-1150 the CPEF of the worst accidentsequence is 3 times 10minus 2

Put CPEF 3 times 10minus 2 and the safety goal value LERF

1 times 10minus 5(r middot y) into formula (3) (en when the worstaccident sequence m occurs the individual early promptfatality risk is

IERm 3 times 10minus 21113872 1113873 times 10minus 5

1113872 1113873 3 times 10minus 7(r middot y)lt IEREQHO

5 times 10minus7(r middot y)

(4)

(erefore using LERFlt 10minus 5(r middot y) as a subsidiary goalof early quantitative health objectives (EQHO) for earlyprompt fatalities is acceptable

223 CDF and QHO [20] CDFlt 10minus 4(r middot y) is a subsid-iary goal of latent quantitative health objectives (LQHO) forlatent cancer fatalities (e rationality of substituting CDFfor LQHO is demonstrated as follows

According to the data survey for nuclear safety goals theindividual risk of cancer fatality from all other causes is 2 times

10minus 3y in the US According to the 01 in the latentquantitative health objective (LQHO) the individual latentrisk (ILRLQHO) caused by nuclear power plant operationsneed to be less than 2 times 10minus 6(r middot y) (e area of a nuclearpower plant means an extension of 10 mile from the

boundary of the nuclear power plant Individual latent risk(ILR) is

ILR 1113944N

1

LFn lowast LLRFn( 1113857

TP(10) (5)

where LFn is the number of latent cancer fatalities within 10miles caused by accident sequence n LLRFn is the frequencyof cancerogenic off-site individual doses caused by accidentsequence n and TP(10) is the total population within 10miles of the nuclear power plant

(en in the population TP(10) the number of latentcancer fatalities caused by accident sequence n is given by

LFn CPLFn lowastTP(10) (6)

where CPLFn is the conditional probability of latent cancerfatalities caused by accident sequence n

According to formulae (5) and (6) the individual latentcancer risk is

ILR 1113944N

1CPLFn lowast LLRFn (7)

Suppose a worst accident sequence n which has thegreatest impact on latent cancer fatalities risk (is accidentsequence n corresponds to a large opening in the con-tainment and an unscrubbed release occurred after thesurrounding population were effectively evacuated Supposethe worst accident occurs in an open containment theconditional large latent release probability for accident se-quence n (CLLRPn) is 10

(en

LLRFn CDFn lowastCLLRPn CDFn lowast 10 CDFn (8)

Putting formula (8) into formula (7) the risk of indi-vidual latent cancer fatality risk is

ILRn CPLFn lowastCDFn (9)

According to the Surry PRA in NUREG-1150 the CPLFof the worst accident sequence is 4 times 10minus 3

Put CPLF 4 times 10minus 3 and the safety goal value CDF

1 times 10minus 4(r middot y) into formula (6) (en when the worstaccident sequence n occurs the individual latent cancerfatality risk is

ILRn 4 times 10minus 31113872 1113873 times 10minus 4

1113872 1113873 4 times 10minus 7(r middot y)lt ILRLQHO

2 times 10minus6(r middot y)

(10)

(erefore using CDFlt 10minus 4(r middot y) as a subsidiary goalof latent quantitative health objectives (LQHO) for latentcancer fatalities is acceptable

3 Investigation into Chinese Societal Risk

According to the process of determining probabilistic safetygoals of USNRC probabilistic safety goals are based onsocietal risks Chinese current probabilistic safety goals refer

Qualitative safety goals

Quantitative safety goals

Subsidiary objectives

IQSG

EQHO

LERF

SQSG

LQHO

CDF

Figure 2 (e relationship among nuclear safety goals in the US

4 Science and Technology of Nuclear Installations

to NRC and IAEA and they are not based on Chinesesocietal risks (erefore we need to investigate the Chinesesocietal risks firstly and then formulate and verify proba-bilistic safety goals based on Chinese societal risks

(e data about the societal risk (ie mortality rate) canbe obtained from the Chinese government and internationalorganizations Chinese statistics include the National Eco-nomic and Societal Development Statistical Bulletin andChinarsquos Health Statistical Yearbook [21 22] Internationalorganizationsrsquo statistics include World Health Organiza-tionrsquos data [23] and World Bankrsquos data [24]

According to the contents of probabilistic safety goalswe focus on early prompt fatalities and latent cancer fatalitiescaused by nuclear power plant operation which can berepresented by accident mortality and cancer mortality insociety respectively

In this section the general overview of Chinese societywas investigated firstly including the analysis about maincauses of fatalities in Chinese society and then make acomparison between the death rate of China and severalother countries

31 Main Causes of Fatalities in China (e total populationof China the number of deaths the number of urban andrural residents and the GDP from 2012 to 2017 are shown inTable 1

(e mortality rates of different causes were countedrespectively when counting the main causes of fatalities ofChinese population (en the causes of death were sortedaccording to the value of mortality (e source data arederived from the Chinese government and internationalorganizations and the statistical results were compared toensure the authenticity of the data Statistics from theChinese government (2012ndash2017) are shown in Table 2Statistics from international organizations (2000 2010 2015and 2016) are shown in Table 3

(e causes of fatalities of Chinese population werecounted based on the source data from Chinese governmentand international organizations as shown above Accordingto the comparison of the above data the difference betweenthe data obtained through the two channels is small whichproves that the statistics are true and reliable (e maincauses of fatalities of Chinese population include malignantneoplasms cerebrovascular diseases heart diseases respi-ratory diseases and external causes of damage andpoisoning

32 Main Causes of Fatalities in Other Countries It is nec-essary to investigate other countriesrsquo societal risks andcompare the results with Chinese societal risks On the onehand the authenticity and reliability of the data can beproved through comparative analysis On the other handinvestigating more countriesrsquo societal risks can help us toprovide further suggestions for nuclear safety goals based onsocietal risks China the United States Japan the UnitedKingdom France India Egypt and Sudan were selected asthe research object countries according to the developmentstatus and the level of nuclear power in each country (e

causes of death and mortality in these countries in 2016 werecounted and the results are shown in Table 4

According to the statistical data from international or-ganizations the causes of death and mortality of China theUnited States Japan the United Kingdom France IndiaEgypt and Sudan in 2016 were counted According to thecomparisons of the causes of death and mortality of Chinaand the US the societal fatalitiesrsquo risks in China and in theUS are similar For example the mortality rates caused bycardiovascular diseases malignant neoplasms respiratorydiseases and injuries are 31710 16788 6647 and 5115 inChina and 25987 19483 7665 and 5698 in the US Forprobabilistic safety goals we focus on the mortality rate ofmalignant neoplasms and external causes which are similarbetween China and the US as well

Furthermore the nuclear safety goals of the US wereformulated and revised from 1979 to 1986 According todata from international organizations the mortality rate ofmalignant neoplasms and external causes in the UnitedStates from 1978 to 1985 were counted and the results areshown in Table 5

According to the statistical data in the table the mor-tality rate of malignant neoplasms and external causes in theUnited States has not changed much from 1978 to 1985 andthey are similar to the current risks of malignant neoplasmsand external causes in China

33 Probabilistic Safety Goals of Multimodule HTGRHigh-temperature gas-cooled reactors are extremely un-likely to cause serious core damage and large early releasedue to inherent safety and unique design concepts CDF andLERF proposed for water-cooled reactor are not suitable forhigh-temperature gas-cooled reactor (erefore the prob-abilistic safety goal of HTR-PM has been reestablished byChina National Nuclear Safety Administration (NASA) thatis ldquothe cumulative frequency of all beyond design basisaccident sequences that lead to off-site (including plantboundary) personal effective dose exceeding 50mSv shall beless than 10minus 6(r middot y)rdquo and this risk metric is defined as theldquofrequency of LARGE release categoryrdquo in HTR-PM prob-abilistic safety analysis (PSA) model In this section weverified the rationality of Chinese existing probabilisticsafety goals for water reactors and then studied the prob-abilistic safety goals for Chinese high-temperature gas-cooled reactors

34ChineseExistingProbabilistic SafetyGoals (emortalityrate of malignant neoplasms and external causes are im-portant basis when verifying the rationality of Chineseexisting CDF and LERF based on the current societal risks inChina According to the above statistics on Chinese societalrisks the statistical results of the mortality rate of malignantneoplasms and external causes are as follows Statistics basedon data from the Chinese government are shown in Table 6and statistics based on data from international organizationsare shown in Table 7

According to the data from the Chinese government andinternational organizations shown in Tables 6 and 7 the

Science and Technology of Nuclear Installations 5

individual latent cancer fatality risk (ILCFR) is about16 times 10minus 3y and the individual early prompt fatality risk(IEPFR) is about 5 times 10minus 4y

According to the Chinese societal risks the reasonabilityof existing probabilistic safety goals in China is shown inFigure 3 Based on the Chinese societal risks and quantitativesafety goals (ldquotwo 01 rulerdquo) the individual latent cancerfatality risk caused by nuclear power plant operation(ILCFRNPP) should be less than 16 times 10minus 6y and the in-dividual early prompt fatality risk caused by nuclear powerplant accidents (IEPFRNPP) should be less than 5 times 10minus 7yBased on the subsidiary safety goals and the assessment ofnuclear power plant the ILCFRNPP is less than 4 times 10minus 8yand the IEPFRNPP is less than 3 times 10minus 8y As shown aboveChinese current probabilistic safety goals can meet the needsof Chinese societal risks control

35 Probabilistic Safety Goals of Multimodule HTGR (edesign characteristics and defense-in-depth measures ofmultimodule HTGR nuclear power plants are differentfrom those of water reactor nuclear power plants Due tothe safety design concept inherent safety and passive

safety measures there is extremely low large release fre-quency and longer time before radioactive material is re-leased into the environment So there is longer time forpostaccident mitigation and emergency response allowingmore measures to actually eliminate core damage and largeearly release (erefore it uses the ldquofrequency of LARGErelease categoryrdquo defined in HTGR PSA as the risk indexrather than the CDF or LERF According to the risk metricof HTR-PM it should be less than 10minus 6(r middot y) However itshould be noted that this safety goal is dedicated to HTR-PM project and it is focused on single reactor rather thanunit (two reactors and one turbine) (erefore this papertries to study whether this risk metric can be extended to beapplied to the multimodule HTGR that is can we use theldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y) as the risk metric ofmultimodule HTGR directly

In the following we will use the risk metric of HTR-PMto demonstrate the margin of probabilistic safety goal

(e ldquoLARGErdquo release category of HTR-PM is similarto the LERF of water reactors and it focuses on earlyprompt fatalities risks and EQHO Individual early risk(IER) is

Table 1 General overview of Chinese Society

Year Total population (rsquo0000) Dead population (rsquo0000) Urban population (rsquo0000) Rural population (rsquo0000) GDP (100 million)2012 135404 966 71182 64222 5193222013 136072 972 73111 62961 5688452014 136782 977 74916 61866 6364632015 137462 975 77116 60346 6767082016 138271 977 79298 58973 7441272017 139008 986 81347 57661 827122Source National Economic and Societal Development Statistical Bulletin [22]

Table 2 Demographic mortality statistics in China based on Chinese data

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017Malignant neoplasms 1583 1526 1574 1598 1583 1591Cerebrovascular diseases 1277 1370 1376 1394 1400 1394Heart diseases 1259 1383 1396 1402 1440 1469Respiratory diseases 890 760 768 763 744 719External causes of damage and poisoning 462 474 457 446 447 432Other diseases 264 82 68 62 61 60Digestive diseases 160 155 145 142 142 145Endocrine nutritional and metabolic diseases 142 146 156 171 184 188Infectious 69 74 72 72 70 67Neurological conditions 66 68 68 67 75 77Genitourinary diseases 65 67 69 68 69 71Mental disorders 25 28 27 28 28 27Acatalepsia 23 25 25 23 22 21Neonatal conditions 23 22 23 19 20 17Congenital anomalies and chromosomal abnormalities 20 21 20 18 16 16Musculoskeletal diseases 14 17 17 17 20 21Blood hematopoietic organ and immune disorders 12 12 12 12 13 13Complications of pregnancy childbirth and puerperium 01 01 01 01 01 01Parasitic diseases 01 01 00 01 01 01Source Chinarsquos Health Statistical Yearbook [21] Note External causes of injury and poisoning include traffic accidents poisoning falls fires naturaldisasters mechanical asphyxiation suicide homicide and mechanical injuries

6 Science and Technology of Nuclear Installations

IER 1113944H

1

EFh lowast LARGEh( 1113857

TP(1) (11)

where EFh is the number of early prompt fatalities within 1mile caused by accident sequence h LARGEh is the fre-quency of fatal LARGE categories caused by accident se-quence h TP(1) is the total population within 1 mile of thenuclear power plant

(en in the population TP(1) the number of earlyprompt fatalities caused by accident sequence h is

EFh CPEFh lowastTP(1) (12)

where CPEFh is the conditional probability of early promptfatalities caused by accident sequence h meaning the con-ditional probability of one personrsquos early fatality caused by aradioactive release nuclear accident

According to formulae (9) and (10) the individual earlyprompt fatality risk is

IER 1113944H

1CPEFh lowast LARGEh (13)

According to the data survey for Chinese societal risksthe individual risk of prompt fatality caused by all otheraccidents is 5 times 10minus 4y in China According to the 01 inthe early quantitative health objective (EQHO) the indi-vidual early risk (IEREQHO) caused by nuclear power plantaccidents needs to be less than 5 times 10minus 7(r middot y) Suppose aworst accident sequence h which has the greatest impact onearly prompt fatalities risk An unscrubbed release occurred

before the surrounding population were effectivelyevacuated

Suppose

IERh CPEFh lowast LARGEh IEREQHO 5 times 10minus 7

(r middot y) (14)

According to the probabilistic safety goals for multi-HTGR LARGEh 1 times 10minus 6(r middot y)

(us CPEFh 05(at is the conditional probability of early prompt fa-

talities caused by the worst accident sequence h is 05 it justmeets the EQHO for individual early prompt fatalities risks

In the International Commission on Radiological Pro-tection (ICPR) Publication 60 according to the dosethreshold of the deterministic effects the 60-day medianlethal dose (LD50[60]) is 3sim5Gytime (e probability ofstochastic effects increases with increasing dose Stochasticeffects include cancer and hereditary diseases For cancerthe probability coefficients of fatal cancer are 5 times 10minus 2Sv forthe public and 4 times 10minus 2Sv for occupational workers en-gaged in radiation For hereditary diseases the probabilitycoefficients of hereditary diseases are 1 times 10minus 2Sv for thepublic and 06 times 10minus 2Sv for workers ICPR 103 followed theconclusion of the ICRP 60 the combined detriment due tofatal cancer and hereditary diseases remains unchanged ataround 5 times 10minus 2Sv For HTR-PM there is extremely lowlarge release frequency and the personal effective dosecontrol threshold is 50mSv According to the results ofabove analysis when LARGEh 1 times 10minus 6(r middot y)andCPEFh 05 the risk metric of HTR-PM can meet the re-quirements of Chinese societal risks In fact the personaleffective dose control threshold is 50mSv and actual CPEFh

is extremely low as well so the risk metric of HTR-PM haslarge margin compared with Chinese societal risk(ereforeit give us the confidence to expand the risk metric of HTR-PM (ie 1 times 10minus 6reactor middot y) to multimodule HTGR (ie1 times 10minus 6(unit middot y) or 1 times 10minus 6(site middot ley)) and then therisk metric of multimodule HTGR can meet the require-ments of Chinese societal risks

4 Discussions

Existing nuclear safety goals is mainly for a single reactorBut in fact most of the plant sites are multireactor sitesMultireactor site means a nuclear power plant site with twoor more reactors on one site From the Fukushima nuclearaccident we realized the possibility and severity of nuclearaccidents occurring at multiple reactors at the same timeNuclear safety goals are set to protect the lives health andenvironment of populations For the populations not onlythe impact of a single reactor on the human body must beconsidered but also the impact of the entire plant site on thehuman body

For example expand the risk metric of HTR-PM from asingle reactor to a plant site and explore the adaptability ofprobabilistic safety goals (e current probabilistic safetygoals of HTR-PM are that the cumulative frequency of allaccident sequences that cause the personal effective dose

Table 3 Demographic mortality statistics in China based on theWHO data

Mortality rate (1100000) 2000 2010 2015 2016Cardiovascular diseases 2128 2696 3095 3171Malignant neoplasms 1444 1599 1663 1679Respiratory diseases 975 712 659 665External causes of damage andpoisoning 607 540 509 512

Neurological condition 206 323 420 449Digestive diseases 183 174 192 197Genitourinary diseases 98 123 149 152Respiratory infectious 192 126 124 126Diabetes mellitus 77 97 116 119Infectious and parasitic diseases 186 120 96 92Neonatal conditions 180 80 54 49Mental and substance use disorders 21 26 31 32Congenital anomalies 67 46 33 31Other neoplasms 15 24 29 29Endocrine blood and immunedisorders 15 14 17 17

Musculoskeletal diseases 11 13 15 15Nutritional deficiencies 14 09 11 11Skin diseases 03 04 05 05Sudden infant death syndrome 01 01 01 01Source World Health Organization statistics [23] Note External causes ofinjury and poisoning include road injury poisonings falls fire heat and hotsubstances drowning exposure to mechanical forces natural disastersother unintentional injuries self-harm interpersonal violence collectiveviolence and legal intervention

Science and Technology of Nuclear Installations 7

outside the plant (including the site boundary) to exceed50mSv is less than 10minus 6(r middot y) Expanding from a singlereactor to a plant site means LARGE 10minus 6(reactor middot year)changed to LARGE 10minus 6(site middot year) (sitemiddotyear smiddoty)

(rough the derivation in Section 4LARGE 10minus 6(s middot y) then CPEFh 05 (at is theconditional probability of early prompt fatalities caused bythe worst accident sequence h in the entire plant site is 05 it

just meets the EQHO for individual early prompt fatalitiesrsquorisks

Suppose there are two reactors in a plant site andsuppose that the two reactors suffer the worst accident se-quence at the same time In order to ensure the probabilisticsafety goals of the multimodule HTGR site and ensure asufficient safety margin it is necessary to ensure the cu-mulative frequency of beyond design basis accidents with a

Table 4 Demographic mortality statistics in different countries

Mortality rate (1100000) China (e US Japan (e UK France India Egypt SudanAll causes 7349 8698 10260 9124 8616 7226 6359 7123Cardiovascular diseases 3171 2599 2808 2287 2216 1956 2570 2029Malignant neoplasms 1679 1948 3129 2557 2679 616 812 446Respiratory diseases 665 767 901 760 480 768 271 221Injuries 512 570 497 318 548 818 367 896Neurological conditions 449 1021 418 1499 995 158 221 163Digestive diseases 197 367 453 435 384 385 834 209Genitourinary diseases 152 267 347 161 164 230 197 198Respiratory infectious diseases 126 206 1107 571 277 466 231 482Diabetes mellitus 119 262 113 100 191 233 187 146Infectious and parasitic diseases 92 175 170 101 154 906 124 1011Neonatal conditions 46 36 05 25 24 415 268 894Mental and substance use disorders 32 149 18 57 92 24 06 16Congenital anomalies 31 40 22 35 30 79 151 180Other neoplasms 29 51 99 60 118 11 38 32Endocrine blood and immune disorders 17 141 82 48 108 16 52 54Musculoskeletal diseases 15 45 52 70 67 37 02 07Nutritional deficiencies 11 30 25 06 65 63 14 34Skin diseases 05 16 15 31 21 10 01 08Maternal conditions 03 02 00 01 01 31 09 90Sudden infant death syndrome 01 05 01 02 02 04 06 09Sense organ diseases 00 00 01 01 Oral conditions 01 01 01 02 00 Source World Health Organization statistics [23]

Table 5 (e mortality rate of malignant neoplasms and external causes in the US

Mortality rate (1100000) 1978 1979 1980 1981 1982 1983 1984 1985Malignant neoplasms 1617 1754 1795 1802 1836 1859 1887 1905External causes 707 706 707 678 638 616 615 612Source World Health Organization statistics [23]

Table 6 (e mortality rate of malignant neoplasms and external causes in China (1)

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017 AverageMalignant neoplasms 1583 1526 1574 1598 1583 1591 1576External causes 462 474 457 446 447 432 453

Table 7 (e mortality rate of malignant neoplasms and external causes in China (2)

Mortality rate (1100000) 2016 2015 2010 2000 AverageMalignant neoplasms 1679 1663 1599 1444 1596External causes 512 509 540 607 542

8 Science and Technology of Nuclear Installations

personal effective dose exceeding 502 25mSv for eachreactor is less than 10minus 62 5 times 10minus7(r middot y)

In fact the individual effective dose and cumulativefrequency caused by the entire plant site are not necessarilythe simple addition of the individual effective dose andcumulative frequency caused by each single reactor How-ever in order to ensure the probabilistic safety goals thevalue of the probabilistic safety goals of each single reactor issmaller than the entire plant site We need to consider thefollowing points

(a) (e safety and reliability of a single reactor is con-stant (e number of reactors on the site needs to becontrolled and cannot be increased indefinitely

(b) (e design of the reactors can still be based on thesingle reactor for the convenience of design But forthe entire plant site we can consider different typesof reactors with different risk levels at the same site

5 Conclusions

According to the statistics on societal risks in China theindividual latent cancer fatality risk (ILCFR) is 16 times 10minus 3yand the individual early prompt fatality risk (IEPFR) is5 times 10minus 4y (e mortality rates are similar in China and theUnited States and the changes in recent years are small (eChinese current probabilistic safety goals can meet the re-quirement of little contribution to social risks

(e probabilistic safety goals of HTR-PM recom-mended by Chinarsquos National Nuclear Safety Adminis-tration (NNSA) are as follows the cumulative frequencyof all beyond-design-basis accident sequences that lead tooff-site (including plant boundary) personal effective doseexceeding 50mSv shall be less than 10minus 6(r middot y) Accordingto the inference the probabilistic safety goals are rationalAnd the risk metric of HTR-PM has large marginaccording to the societal risk of China maybe it can beextended to be applied to the multimodule HTGR asldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y)rdquo

In the end we think it is better that the probabilisticsafety goals based on entire plant site rather than a single

reactor We need to control the number of reactors on onesite and we can consider different types of reactors withdifferent risk levels at the same site And the above analysisprocess is applicable to other types of reactors

Data Availability

(e data used in this paper are obtained from China Na-tional Bureau of Statistics (httpwwwstatsgovcn) andWorld Health Organization (httpswwwwhointdatacollections)

Conflicts of Interest

(e authors declare that they have no conflicts of interestregarding the publication of this paper

Acknowledgments

(is study was supported by the National Science andTechnology Major Project (2018ZX06902015) and the Na-tional Natural Science Foundation of China (Project no71601139)

References

[1] C Meyer ldquoChina and nuclear energy solving an energycrisisndashpart 4rdquo Energize vol 7 no 42 pp 18-19 2011

[2] J Wood ldquoNuclear safety and three major accidentsrdquo NuclearPower IET Digital Library vol 18 no 6 2007

[3] OECDNEA Probabilistic Risk Criteria and Safety GoalsNEACSNIR Organization for Economic Cooperation andDevelopmentNuclear Energy Agency (OECDNEA) ParisFrance 2009

[4] Z Zhang Z Wu and Y Sun ldquoDesign aspects of the Chinesemodular high-temperature gas-cooled reactor HTR-PMrdquoNuclear Engineering amp Design vol 236 no 5-6 pp 485ndash4902006

[5] IAEA ldquoPolicy for setting and assessing regulatory safetygoalsrdquo 1995

[6] EPRI ldquoAdvanced light water reactor utility requirementsdocumentrdquo ALWR Policy and Summary of Top-Tier Re-quirements vol 1 1990

[7] K R KEMA ldquoEuropean utility requirements for LWR nuclearpower plantsrdquo Main Policies and Top Tier RequirementsRevision B vol 1 1995

[8] GPR-RSK ldquoIPSN-GRS proposals for the development oftechnical guideline for future pWRsrdquo 1997

[9] IAEA Safety Series 75-INSAG-3 Basic Safety Principles forNuclear Power Plants IAEA 1988 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

[10] IAEA Safety Series 75-INSAG-12 Basic Safety Principles forNuclear Power Plants IAEA 1999 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

Chinese societal risks

IEPFR 50E ndash 4y

ILCFR 16E ndash 3y

Risks based on quantitativehealth objectives

01 01

Probabilistic safety goals

LERF lt 1E ndash 6(rmiddoty)

CDF lt 1E ndash 5(rmiddoty)

IEPFRNPP 50E ndash 7y

ILCFRNPP 16E ndash 6y

IEPFRNPP 30E ndash 8y

ILCFRNPP 40E ndash 8y

Risks based on probabilisticsafety goals

IER ILR

gt

gt

Figure 3 (e rationality of existing probabilistic safety goals inChina

Science and Technology of Nuclear Installations 9

to NRC and IAEA and they are not based on Chinesesocietal risks (erefore we need to investigate the Chinesesocietal risks firstly and then formulate and verify proba-bilistic safety goals based on Chinese societal risks

(e data about the societal risk (ie mortality rate) canbe obtained from the Chinese government and internationalorganizations Chinese statistics include the National Eco-nomic and Societal Development Statistical Bulletin andChinarsquos Health Statistical Yearbook [21 22] Internationalorganizationsrsquo statistics include World Health Organiza-tionrsquos data [23] and World Bankrsquos data [24]

According to the contents of probabilistic safety goalswe focus on early prompt fatalities and latent cancer fatalitiescaused by nuclear power plant operation which can berepresented by accident mortality and cancer mortality insociety respectively

In this section the general overview of Chinese societywas investigated firstly including the analysis about maincauses of fatalities in Chinese society and then make acomparison between the death rate of China and severalother countries

31 Main Causes of Fatalities in China (e total populationof China the number of deaths the number of urban andrural residents and the GDP from 2012 to 2017 are shown inTable 1

(e mortality rates of different causes were countedrespectively when counting the main causes of fatalities ofChinese population (en the causes of death were sortedaccording to the value of mortality (e source data arederived from the Chinese government and internationalorganizations and the statistical results were compared toensure the authenticity of the data Statistics from theChinese government (2012ndash2017) are shown in Table 2Statistics from international organizations (2000 2010 2015and 2016) are shown in Table 3

(e causes of fatalities of Chinese population werecounted based on the source data from Chinese governmentand international organizations as shown above Accordingto the comparison of the above data the difference betweenthe data obtained through the two channels is small whichproves that the statistics are true and reliable (e maincauses of fatalities of Chinese population include malignantneoplasms cerebrovascular diseases heart diseases respi-ratory diseases and external causes of damage andpoisoning

32 Main Causes of Fatalities in Other Countries It is nec-essary to investigate other countriesrsquo societal risks andcompare the results with Chinese societal risks On the onehand the authenticity and reliability of the data can beproved through comparative analysis On the other handinvestigating more countriesrsquo societal risks can help us toprovide further suggestions for nuclear safety goals based onsocietal risks China the United States Japan the UnitedKingdom France India Egypt and Sudan were selected asthe research object countries according to the developmentstatus and the level of nuclear power in each country (e

causes of death and mortality in these countries in 2016 werecounted and the results are shown in Table 4

According to the statistical data from international or-ganizations the causes of death and mortality of China theUnited States Japan the United Kingdom France IndiaEgypt and Sudan in 2016 were counted According to thecomparisons of the causes of death and mortality of Chinaand the US the societal fatalitiesrsquo risks in China and in theUS are similar For example the mortality rates caused bycardiovascular diseases malignant neoplasms respiratorydiseases and injuries are 31710 16788 6647 and 5115 inChina and 25987 19483 7665 and 5698 in the US Forprobabilistic safety goals we focus on the mortality rate ofmalignant neoplasms and external causes which are similarbetween China and the US as well

Furthermore the nuclear safety goals of the US wereformulated and revised from 1979 to 1986 According todata from international organizations the mortality rate ofmalignant neoplasms and external causes in the UnitedStates from 1978 to 1985 were counted and the results areshown in Table 5

According to the statistical data in the table the mor-tality rate of malignant neoplasms and external causes in theUnited States has not changed much from 1978 to 1985 andthey are similar to the current risks of malignant neoplasmsand external causes in China

33 Probabilistic Safety Goals of Multimodule HTGRHigh-temperature gas-cooled reactors are extremely un-likely to cause serious core damage and large early releasedue to inherent safety and unique design concepts CDF andLERF proposed for water-cooled reactor are not suitable forhigh-temperature gas-cooled reactor (erefore the prob-abilistic safety goal of HTR-PM has been reestablished byChina National Nuclear Safety Administration (NASA) thatis ldquothe cumulative frequency of all beyond design basisaccident sequences that lead to off-site (including plantboundary) personal effective dose exceeding 50mSv shall beless than 10minus 6(r middot y)rdquo and this risk metric is defined as theldquofrequency of LARGE release categoryrdquo in HTR-PM prob-abilistic safety analysis (PSA) model In this section weverified the rationality of Chinese existing probabilisticsafety goals for water reactors and then studied the prob-abilistic safety goals for Chinese high-temperature gas-cooled reactors

34ChineseExistingProbabilistic SafetyGoals (emortalityrate of malignant neoplasms and external causes are im-portant basis when verifying the rationality of Chineseexisting CDF and LERF based on the current societal risks inChina According to the above statistics on Chinese societalrisks the statistical results of the mortality rate of malignantneoplasms and external causes are as follows Statistics basedon data from the Chinese government are shown in Table 6and statistics based on data from international organizationsare shown in Table 7

According to the data from the Chinese government andinternational organizations shown in Tables 6 and 7 the

Science and Technology of Nuclear Installations 5

individual latent cancer fatality risk (ILCFR) is about16 times 10minus 3y and the individual early prompt fatality risk(IEPFR) is about 5 times 10minus 4y

According to the Chinese societal risks the reasonabilityof existing probabilistic safety goals in China is shown inFigure 3 Based on the Chinese societal risks and quantitativesafety goals (ldquotwo 01 rulerdquo) the individual latent cancerfatality risk caused by nuclear power plant operation(ILCFRNPP) should be less than 16 times 10minus 6y and the in-dividual early prompt fatality risk caused by nuclear powerplant accidents (IEPFRNPP) should be less than 5 times 10minus 7yBased on the subsidiary safety goals and the assessment ofnuclear power plant the ILCFRNPP is less than 4 times 10minus 8yand the IEPFRNPP is less than 3 times 10minus 8y As shown aboveChinese current probabilistic safety goals can meet the needsof Chinese societal risks control

35 Probabilistic Safety Goals of Multimodule HTGR (edesign characteristics and defense-in-depth measures ofmultimodule HTGR nuclear power plants are differentfrom those of water reactor nuclear power plants Due tothe safety design concept inherent safety and passive

safety measures there is extremely low large release fre-quency and longer time before radioactive material is re-leased into the environment So there is longer time forpostaccident mitigation and emergency response allowingmore measures to actually eliminate core damage and largeearly release (erefore it uses the ldquofrequency of LARGErelease categoryrdquo defined in HTGR PSA as the risk indexrather than the CDF or LERF According to the risk metricof HTR-PM it should be less than 10minus 6(r middot y) However itshould be noted that this safety goal is dedicated to HTR-PM project and it is focused on single reactor rather thanunit (two reactors and one turbine) (erefore this papertries to study whether this risk metric can be extended to beapplied to the multimodule HTGR that is can we use theldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y) as the risk metric ofmultimodule HTGR directly

In the following we will use the risk metric of HTR-PMto demonstrate the margin of probabilistic safety goal

(e ldquoLARGErdquo release category of HTR-PM is similarto the LERF of water reactors and it focuses on earlyprompt fatalities risks and EQHO Individual early risk(IER) is

Table 1 General overview of Chinese Society

Year Total population (rsquo0000) Dead population (rsquo0000) Urban population (rsquo0000) Rural population (rsquo0000) GDP (100 million)2012 135404 966 71182 64222 5193222013 136072 972 73111 62961 5688452014 136782 977 74916 61866 6364632015 137462 975 77116 60346 6767082016 138271 977 79298 58973 7441272017 139008 986 81347 57661 827122Source National Economic and Societal Development Statistical Bulletin [22]

Table 2 Demographic mortality statistics in China based on Chinese data

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017Malignant neoplasms 1583 1526 1574 1598 1583 1591Cerebrovascular diseases 1277 1370 1376 1394 1400 1394Heart diseases 1259 1383 1396 1402 1440 1469Respiratory diseases 890 760 768 763 744 719External causes of damage and poisoning 462 474 457 446 447 432Other diseases 264 82 68 62 61 60Digestive diseases 160 155 145 142 142 145Endocrine nutritional and metabolic diseases 142 146 156 171 184 188Infectious 69 74 72 72 70 67Neurological conditions 66 68 68 67 75 77Genitourinary diseases 65 67 69 68 69 71Mental disorders 25 28 27 28 28 27Acatalepsia 23 25 25 23 22 21Neonatal conditions 23 22 23 19 20 17Congenital anomalies and chromosomal abnormalities 20 21 20 18 16 16Musculoskeletal diseases 14 17 17 17 20 21Blood hematopoietic organ and immune disorders 12 12 12 12 13 13Complications of pregnancy childbirth and puerperium 01 01 01 01 01 01Parasitic diseases 01 01 00 01 01 01Source Chinarsquos Health Statistical Yearbook [21] Note External causes of injury and poisoning include traffic accidents poisoning falls fires naturaldisasters mechanical asphyxiation suicide homicide and mechanical injuries

6 Science and Technology of Nuclear Installations

IER 1113944H

1

EFh lowast LARGEh( 1113857

TP(1) (11)

where EFh is the number of early prompt fatalities within 1mile caused by accident sequence h LARGEh is the fre-quency of fatal LARGE categories caused by accident se-quence h TP(1) is the total population within 1 mile of thenuclear power plant

(en in the population TP(1) the number of earlyprompt fatalities caused by accident sequence h is

EFh CPEFh lowastTP(1) (12)

where CPEFh is the conditional probability of early promptfatalities caused by accident sequence h meaning the con-ditional probability of one personrsquos early fatality caused by aradioactive release nuclear accident

According to formulae (9) and (10) the individual earlyprompt fatality risk is

IER 1113944H

1CPEFh lowast LARGEh (13)

According to the data survey for Chinese societal risksthe individual risk of prompt fatality caused by all otheraccidents is 5 times 10minus 4y in China According to the 01 inthe early quantitative health objective (EQHO) the indi-vidual early risk (IEREQHO) caused by nuclear power plantaccidents needs to be less than 5 times 10minus 7(r middot y) Suppose aworst accident sequence h which has the greatest impact onearly prompt fatalities risk An unscrubbed release occurred

before the surrounding population were effectivelyevacuated

Suppose

IERh CPEFh lowast LARGEh IEREQHO 5 times 10minus 7

(r middot y) (14)

According to the probabilistic safety goals for multi-HTGR LARGEh 1 times 10minus 6(r middot y)

(us CPEFh 05(at is the conditional probability of early prompt fa-

talities caused by the worst accident sequence h is 05 it justmeets the EQHO for individual early prompt fatalities risks

In the International Commission on Radiological Pro-tection (ICPR) Publication 60 according to the dosethreshold of the deterministic effects the 60-day medianlethal dose (LD50[60]) is 3sim5Gytime (e probability ofstochastic effects increases with increasing dose Stochasticeffects include cancer and hereditary diseases For cancerthe probability coefficients of fatal cancer are 5 times 10minus 2Sv forthe public and 4 times 10minus 2Sv for occupational workers en-gaged in radiation For hereditary diseases the probabilitycoefficients of hereditary diseases are 1 times 10minus 2Sv for thepublic and 06 times 10minus 2Sv for workers ICPR 103 followed theconclusion of the ICRP 60 the combined detriment due tofatal cancer and hereditary diseases remains unchanged ataround 5 times 10minus 2Sv For HTR-PM there is extremely lowlarge release frequency and the personal effective dosecontrol threshold is 50mSv According to the results ofabove analysis when LARGEh 1 times 10minus 6(r middot y)andCPEFh 05 the risk metric of HTR-PM can meet the re-quirements of Chinese societal risks In fact the personaleffective dose control threshold is 50mSv and actual CPEFh

is extremely low as well so the risk metric of HTR-PM haslarge margin compared with Chinese societal risk(ereforeit give us the confidence to expand the risk metric of HTR-PM (ie 1 times 10minus 6reactor middot y) to multimodule HTGR (ie1 times 10minus 6(unit middot y) or 1 times 10minus 6(site middot ley)) and then therisk metric of multimodule HTGR can meet the require-ments of Chinese societal risks

4 Discussions

Existing nuclear safety goals is mainly for a single reactorBut in fact most of the plant sites are multireactor sitesMultireactor site means a nuclear power plant site with twoor more reactors on one site From the Fukushima nuclearaccident we realized the possibility and severity of nuclearaccidents occurring at multiple reactors at the same timeNuclear safety goals are set to protect the lives health andenvironment of populations For the populations not onlythe impact of a single reactor on the human body must beconsidered but also the impact of the entire plant site on thehuman body

For example expand the risk metric of HTR-PM from asingle reactor to a plant site and explore the adaptability ofprobabilistic safety goals (e current probabilistic safetygoals of HTR-PM are that the cumulative frequency of allaccident sequences that cause the personal effective dose

Table 3 Demographic mortality statistics in China based on theWHO data

Mortality rate (1100000) 2000 2010 2015 2016Cardiovascular diseases 2128 2696 3095 3171Malignant neoplasms 1444 1599 1663 1679Respiratory diseases 975 712 659 665External causes of damage andpoisoning 607 540 509 512

Neurological condition 206 323 420 449Digestive diseases 183 174 192 197Genitourinary diseases 98 123 149 152Respiratory infectious 192 126 124 126Diabetes mellitus 77 97 116 119Infectious and parasitic diseases 186 120 96 92Neonatal conditions 180 80 54 49Mental and substance use disorders 21 26 31 32Congenital anomalies 67 46 33 31Other neoplasms 15 24 29 29Endocrine blood and immunedisorders 15 14 17 17

Musculoskeletal diseases 11 13 15 15Nutritional deficiencies 14 09 11 11Skin diseases 03 04 05 05Sudden infant death syndrome 01 01 01 01Source World Health Organization statistics [23] Note External causes ofinjury and poisoning include road injury poisonings falls fire heat and hotsubstances drowning exposure to mechanical forces natural disastersother unintentional injuries self-harm interpersonal violence collectiveviolence and legal intervention

Science and Technology of Nuclear Installations 7

outside the plant (including the site boundary) to exceed50mSv is less than 10minus 6(r middot y) Expanding from a singlereactor to a plant site means LARGE 10minus 6(reactor middot year)changed to LARGE 10minus 6(site middot year) (sitemiddotyear smiddoty)

(rough the derivation in Section 4LARGE 10minus 6(s middot y) then CPEFh 05 (at is theconditional probability of early prompt fatalities caused bythe worst accident sequence h in the entire plant site is 05 it

just meets the EQHO for individual early prompt fatalitiesrsquorisks

Suppose there are two reactors in a plant site andsuppose that the two reactors suffer the worst accident se-quence at the same time In order to ensure the probabilisticsafety goals of the multimodule HTGR site and ensure asufficient safety margin it is necessary to ensure the cu-mulative frequency of beyond design basis accidents with a

Table 4 Demographic mortality statistics in different countries

Mortality rate (1100000) China (e US Japan (e UK France India Egypt SudanAll causes 7349 8698 10260 9124 8616 7226 6359 7123Cardiovascular diseases 3171 2599 2808 2287 2216 1956 2570 2029Malignant neoplasms 1679 1948 3129 2557 2679 616 812 446Respiratory diseases 665 767 901 760 480 768 271 221Injuries 512 570 497 318 548 818 367 896Neurological conditions 449 1021 418 1499 995 158 221 163Digestive diseases 197 367 453 435 384 385 834 209Genitourinary diseases 152 267 347 161 164 230 197 198Respiratory infectious diseases 126 206 1107 571 277 466 231 482Diabetes mellitus 119 262 113 100 191 233 187 146Infectious and parasitic diseases 92 175 170 101 154 906 124 1011Neonatal conditions 46 36 05 25 24 415 268 894Mental and substance use disorders 32 149 18 57 92 24 06 16Congenital anomalies 31 40 22 35 30 79 151 180Other neoplasms 29 51 99 60 118 11 38 32Endocrine blood and immune disorders 17 141 82 48 108 16 52 54Musculoskeletal diseases 15 45 52 70 67 37 02 07Nutritional deficiencies 11 30 25 06 65 63 14 34Skin diseases 05 16 15 31 21 10 01 08Maternal conditions 03 02 00 01 01 31 09 90Sudden infant death syndrome 01 05 01 02 02 04 06 09Sense organ diseases 00 00 01 01 Oral conditions 01 01 01 02 00 Source World Health Organization statistics [23]

Table 5 (e mortality rate of malignant neoplasms and external causes in the US

Mortality rate (1100000) 1978 1979 1980 1981 1982 1983 1984 1985Malignant neoplasms 1617 1754 1795 1802 1836 1859 1887 1905External causes 707 706 707 678 638 616 615 612Source World Health Organization statistics [23]

Table 6 (e mortality rate of malignant neoplasms and external causes in China (1)

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017 AverageMalignant neoplasms 1583 1526 1574 1598 1583 1591 1576External causes 462 474 457 446 447 432 453

Table 7 (e mortality rate of malignant neoplasms and external causes in China (2)

Mortality rate (1100000) 2016 2015 2010 2000 AverageMalignant neoplasms 1679 1663 1599 1444 1596External causes 512 509 540 607 542

8 Science and Technology of Nuclear Installations

personal effective dose exceeding 502 25mSv for eachreactor is less than 10minus 62 5 times 10minus7(r middot y)

In fact the individual effective dose and cumulativefrequency caused by the entire plant site are not necessarilythe simple addition of the individual effective dose andcumulative frequency caused by each single reactor How-ever in order to ensure the probabilistic safety goals thevalue of the probabilistic safety goals of each single reactor issmaller than the entire plant site We need to consider thefollowing points

(a) (e safety and reliability of a single reactor is con-stant (e number of reactors on the site needs to becontrolled and cannot be increased indefinitely

(b) (e design of the reactors can still be based on thesingle reactor for the convenience of design But forthe entire plant site we can consider different typesof reactors with different risk levels at the same site

5 Conclusions

According to the statistics on societal risks in China theindividual latent cancer fatality risk (ILCFR) is 16 times 10minus 3yand the individual early prompt fatality risk (IEPFR) is5 times 10minus 4y (e mortality rates are similar in China and theUnited States and the changes in recent years are small (eChinese current probabilistic safety goals can meet the re-quirement of little contribution to social risks

(e probabilistic safety goals of HTR-PM recom-mended by Chinarsquos National Nuclear Safety Adminis-tration (NNSA) are as follows the cumulative frequencyof all beyond-design-basis accident sequences that lead tooff-site (including plant boundary) personal effective doseexceeding 50mSv shall be less than 10minus 6(r middot y) Accordingto the inference the probabilistic safety goals are rationalAnd the risk metric of HTR-PM has large marginaccording to the societal risk of China maybe it can beextended to be applied to the multimodule HTGR asldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y)rdquo

In the end we think it is better that the probabilisticsafety goals based on entire plant site rather than a single

reactor We need to control the number of reactors on onesite and we can consider different types of reactors withdifferent risk levels at the same site And the above analysisprocess is applicable to other types of reactors

Data Availability

(e data used in this paper are obtained from China Na-tional Bureau of Statistics (httpwwwstatsgovcn) andWorld Health Organization (httpswwwwhointdatacollections)

Conflicts of Interest

(e authors declare that they have no conflicts of interestregarding the publication of this paper

Acknowledgments

(is study was supported by the National Science andTechnology Major Project (2018ZX06902015) and the Na-tional Natural Science Foundation of China (Project no71601139)

References

[1] C Meyer ldquoChina and nuclear energy solving an energycrisisndashpart 4rdquo Energize vol 7 no 42 pp 18-19 2011

[2] J Wood ldquoNuclear safety and three major accidentsrdquo NuclearPower IET Digital Library vol 18 no 6 2007

[3] OECDNEA Probabilistic Risk Criteria and Safety GoalsNEACSNIR Organization for Economic Cooperation andDevelopmentNuclear Energy Agency (OECDNEA) ParisFrance 2009

[4] Z Zhang Z Wu and Y Sun ldquoDesign aspects of the Chinesemodular high-temperature gas-cooled reactor HTR-PMrdquoNuclear Engineering amp Design vol 236 no 5-6 pp 485ndash4902006

[5] IAEA ldquoPolicy for setting and assessing regulatory safetygoalsrdquo 1995

[6] EPRI ldquoAdvanced light water reactor utility requirementsdocumentrdquo ALWR Policy and Summary of Top-Tier Re-quirements vol 1 1990

[7] K R KEMA ldquoEuropean utility requirements for LWR nuclearpower plantsrdquo Main Policies and Top Tier RequirementsRevision B vol 1 1995

[8] GPR-RSK ldquoIPSN-GRS proposals for the development oftechnical guideline for future pWRsrdquo 1997

[9] IAEA Safety Series 75-INSAG-3 Basic Safety Principles forNuclear Power Plants IAEA 1988 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

[10] IAEA Safety Series 75-INSAG-12 Basic Safety Principles forNuclear Power Plants IAEA 1999 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

Chinese societal risks

IEPFR 50E ndash 4y

ILCFR 16E ndash 3y

Risks based on quantitativehealth objectives

01 01

Probabilistic safety goals

LERF lt 1E ndash 6(rmiddoty)

CDF lt 1E ndash 5(rmiddoty)

IEPFRNPP 50E ndash 7y

ILCFRNPP 16E ndash 6y

IEPFRNPP 30E ndash 8y

ILCFRNPP 40E ndash 8y

Risks based on probabilisticsafety goals

IER ILR

gt

gt

Figure 3 (e rationality of existing probabilistic safety goals inChina

Science and Technology of Nuclear Installations 9

individual latent cancer fatality risk (ILCFR) is about16 times 10minus 3y and the individual early prompt fatality risk(IEPFR) is about 5 times 10minus 4y

According to the Chinese societal risks the reasonabilityof existing probabilistic safety goals in China is shown inFigure 3 Based on the Chinese societal risks and quantitativesafety goals (ldquotwo 01 rulerdquo) the individual latent cancerfatality risk caused by nuclear power plant operation(ILCFRNPP) should be less than 16 times 10minus 6y and the in-dividual early prompt fatality risk caused by nuclear powerplant accidents (IEPFRNPP) should be less than 5 times 10minus 7yBased on the subsidiary safety goals and the assessment ofnuclear power plant the ILCFRNPP is less than 4 times 10minus 8yand the IEPFRNPP is less than 3 times 10minus 8y As shown aboveChinese current probabilistic safety goals can meet the needsof Chinese societal risks control

35 Probabilistic Safety Goals of Multimodule HTGR (edesign characteristics and defense-in-depth measures ofmultimodule HTGR nuclear power plants are differentfrom those of water reactor nuclear power plants Due tothe safety design concept inherent safety and passive

safety measures there is extremely low large release fre-quency and longer time before radioactive material is re-leased into the environment So there is longer time forpostaccident mitigation and emergency response allowingmore measures to actually eliminate core damage and largeearly release (erefore it uses the ldquofrequency of LARGErelease categoryrdquo defined in HTGR PSA as the risk indexrather than the CDF or LERF According to the risk metricof HTR-PM it should be less than 10minus 6(r middot y) However itshould be noted that this safety goal is dedicated to HTR-PM project and it is focused on single reactor rather thanunit (two reactors and one turbine) (erefore this papertries to study whether this risk metric can be extended to beapplied to the multimodule HTGR that is can we use theldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y) as the risk metric ofmultimodule HTGR directly

In the following we will use the risk metric of HTR-PMto demonstrate the margin of probabilistic safety goal

(e ldquoLARGErdquo release category of HTR-PM is similarto the LERF of water reactors and it focuses on earlyprompt fatalities risks and EQHO Individual early risk(IER) is

Table 1 General overview of Chinese Society

Year Total population (rsquo0000) Dead population (rsquo0000) Urban population (rsquo0000) Rural population (rsquo0000) GDP (100 million)2012 135404 966 71182 64222 5193222013 136072 972 73111 62961 5688452014 136782 977 74916 61866 6364632015 137462 975 77116 60346 6767082016 138271 977 79298 58973 7441272017 139008 986 81347 57661 827122Source National Economic and Societal Development Statistical Bulletin [22]

Table 2 Demographic mortality statistics in China based on Chinese data

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017Malignant neoplasms 1583 1526 1574 1598 1583 1591Cerebrovascular diseases 1277 1370 1376 1394 1400 1394Heart diseases 1259 1383 1396 1402 1440 1469Respiratory diseases 890 760 768 763 744 719External causes of damage and poisoning 462 474 457 446 447 432Other diseases 264 82 68 62 61 60Digestive diseases 160 155 145 142 142 145Endocrine nutritional and metabolic diseases 142 146 156 171 184 188Infectious 69 74 72 72 70 67Neurological conditions 66 68 68 67 75 77Genitourinary diseases 65 67 69 68 69 71Mental disorders 25 28 27 28 28 27Acatalepsia 23 25 25 23 22 21Neonatal conditions 23 22 23 19 20 17Congenital anomalies and chromosomal abnormalities 20 21 20 18 16 16Musculoskeletal diseases 14 17 17 17 20 21Blood hematopoietic organ and immune disorders 12 12 12 12 13 13Complications of pregnancy childbirth and puerperium 01 01 01 01 01 01Parasitic diseases 01 01 00 01 01 01Source Chinarsquos Health Statistical Yearbook [21] Note External causes of injury and poisoning include traffic accidents poisoning falls fires naturaldisasters mechanical asphyxiation suicide homicide and mechanical injuries

6 Science and Technology of Nuclear Installations

IER 1113944H

1

EFh lowast LARGEh( 1113857

TP(1) (11)

where EFh is the number of early prompt fatalities within 1mile caused by accident sequence h LARGEh is the fre-quency of fatal LARGE categories caused by accident se-quence h TP(1) is the total population within 1 mile of thenuclear power plant

(en in the population TP(1) the number of earlyprompt fatalities caused by accident sequence h is

EFh CPEFh lowastTP(1) (12)

where CPEFh is the conditional probability of early promptfatalities caused by accident sequence h meaning the con-ditional probability of one personrsquos early fatality caused by aradioactive release nuclear accident

According to formulae (9) and (10) the individual earlyprompt fatality risk is

IER 1113944H

1CPEFh lowast LARGEh (13)

According to the data survey for Chinese societal risksthe individual risk of prompt fatality caused by all otheraccidents is 5 times 10minus 4y in China According to the 01 inthe early quantitative health objective (EQHO) the indi-vidual early risk (IEREQHO) caused by nuclear power plantaccidents needs to be less than 5 times 10minus 7(r middot y) Suppose aworst accident sequence h which has the greatest impact onearly prompt fatalities risk An unscrubbed release occurred

before the surrounding population were effectivelyevacuated

Suppose

IERh CPEFh lowast LARGEh IEREQHO 5 times 10minus 7

(r middot y) (14)

According to the probabilistic safety goals for multi-HTGR LARGEh 1 times 10minus 6(r middot y)

(us CPEFh 05(at is the conditional probability of early prompt fa-

talities caused by the worst accident sequence h is 05 it justmeets the EQHO for individual early prompt fatalities risks

In the International Commission on Radiological Pro-tection (ICPR) Publication 60 according to the dosethreshold of the deterministic effects the 60-day medianlethal dose (LD50[60]) is 3sim5Gytime (e probability ofstochastic effects increases with increasing dose Stochasticeffects include cancer and hereditary diseases For cancerthe probability coefficients of fatal cancer are 5 times 10minus 2Sv forthe public and 4 times 10minus 2Sv for occupational workers en-gaged in radiation For hereditary diseases the probabilitycoefficients of hereditary diseases are 1 times 10minus 2Sv for thepublic and 06 times 10minus 2Sv for workers ICPR 103 followed theconclusion of the ICRP 60 the combined detriment due tofatal cancer and hereditary diseases remains unchanged ataround 5 times 10minus 2Sv For HTR-PM there is extremely lowlarge release frequency and the personal effective dosecontrol threshold is 50mSv According to the results ofabove analysis when LARGEh 1 times 10minus 6(r middot y)andCPEFh 05 the risk metric of HTR-PM can meet the re-quirements of Chinese societal risks In fact the personaleffective dose control threshold is 50mSv and actual CPEFh

is extremely low as well so the risk metric of HTR-PM haslarge margin compared with Chinese societal risk(ereforeit give us the confidence to expand the risk metric of HTR-PM (ie 1 times 10minus 6reactor middot y) to multimodule HTGR (ie1 times 10minus 6(unit middot y) or 1 times 10minus 6(site middot ley)) and then therisk metric of multimodule HTGR can meet the require-ments of Chinese societal risks

4 Discussions

Existing nuclear safety goals is mainly for a single reactorBut in fact most of the plant sites are multireactor sitesMultireactor site means a nuclear power plant site with twoor more reactors on one site From the Fukushima nuclearaccident we realized the possibility and severity of nuclearaccidents occurring at multiple reactors at the same timeNuclear safety goals are set to protect the lives health andenvironment of populations For the populations not onlythe impact of a single reactor on the human body must beconsidered but also the impact of the entire plant site on thehuman body

For example expand the risk metric of HTR-PM from asingle reactor to a plant site and explore the adaptability ofprobabilistic safety goals (e current probabilistic safetygoals of HTR-PM are that the cumulative frequency of allaccident sequences that cause the personal effective dose

Table 3 Demographic mortality statistics in China based on theWHO data

Mortality rate (1100000) 2000 2010 2015 2016Cardiovascular diseases 2128 2696 3095 3171Malignant neoplasms 1444 1599 1663 1679Respiratory diseases 975 712 659 665External causes of damage andpoisoning 607 540 509 512

Neurological condition 206 323 420 449Digestive diseases 183 174 192 197Genitourinary diseases 98 123 149 152Respiratory infectious 192 126 124 126Diabetes mellitus 77 97 116 119Infectious and parasitic diseases 186 120 96 92Neonatal conditions 180 80 54 49Mental and substance use disorders 21 26 31 32Congenital anomalies 67 46 33 31Other neoplasms 15 24 29 29Endocrine blood and immunedisorders 15 14 17 17

Musculoskeletal diseases 11 13 15 15Nutritional deficiencies 14 09 11 11Skin diseases 03 04 05 05Sudden infant death syndrome 01 01 01 01Source World Health Organization statistics [23] Note External causes ofinjury and poisoning include road injury poisonings falls fire heat and hotsubstances drowning exposure to mechanical forces natural disastersother unintentional injuries self-harm interpersonal violence collectiveviolence and legal intervention

Science and Technology of Nuclear Installations 7

outside the plant (including the site boundary) to exceed50mSv is less than 10minus 6(r middot y) Expanding from a singlereactor to a plant site means LARGE 10minus 6(reactor middot year)changed to LARGE 10minus 6(site middot year) (sitemiddotyear smiddoty)

(rough the derivation in Section 4LARGE 10minus 6(s middot y) then CPEFh 05 (at is theconditional probability of early prompt fatalities caused bythe worst accident sequence h in the entire plant site is 05 it

just meets the EQHO for individual early prompt fatalitiesrsquorisks

Suppose there are two reactors in a plant site andsuppose that the two reactors suffer the worst accident se-quence at the same time In order to ensure the probabilisticsafety goals of the multimodule HTGR site and ensure asufficient safety margin it is necessary to ensure the cu-mulative frequency of beyond design basis accidents with a

Table 4 Demographic mortality statistics in different countries

Mortality rate (1100000) China (e US Japan (e UK France India Egypt SudanAll causes 7349 8698 10260 9124 8616 7226 6359 7123Cardiovascular diseases 3171 2599 2808 2287 2216 1956 2570 2029Malignant neoplasms 1679 1948 3129 2557 2679 616 812 446Respiratory diseases 665 767 901 760 480 768 271 221Injuries 512 570 497 318 548 818 367 896Neurological conditions 449 1021 418 1499 995 158 221 163Digestive diseases 197 367 453 435 384 385 834 209Genitourinary diseases 152 267 347 161 164 230 197 198Respiratory infectious diseases 126 206 1107 571 277 466 231 482Diabetes mellitus 119 262 113 100 191 233 187 146Infectious and parasitic diseases 92 175 170 101 154 906 124 1011Neonatal conditions 46 36 05 25 24 415 268 894Mental and substance use disorders 32 149 18 57 92 24 06 16Congenital anomalies 31 40 22 35 30 79 151 180Other neoplasms 29 51 99 60 118 11 38 32Endocrine blood and immune disorders 17 141 82 48 108 16 52 54Musculoskeletal diseases 15 45 52 70 67 37 02 07Nutritional deficiencies 11 30 25 06 65 63 14 34Skin diseases 05 16 15 31 21 10 01 08Maternal conditions 03 02 00 01 01 31 09 90Sudden infant death syndrome 01 05 01 02 02 04 06 09Sense organ diseases 00 00 01 01 Oral conditions 01 01 01 02 00 Source World Health Organization statistics [23]

Table 5 (e mortality rate of malignant neoplasms and external causes in the US

Mortality rate (1100000) 1978 1979 1980 1981 1982 1983 1984 1985Malignant neoplasms 1617 1754 1795 1802 1836 1859 1887 1905External causes 707 706 707 678 638 616 615 612Source World Health Organization statistics [23]

Table 6 (e mortality rate of malignant neoplasms and external causes in China (1)

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017 AverageMalignant neoplasms 1583 1526 1574 1598 1583 1591 1576External causes 462 474 457 446 447 432 453

Table 7 (e mortality rate of malignant neoplasms and external causes in China (2)

Mortality rate (1100000) 2016 2015 2010 2000 AverageMalignant neoplasms 1679 1663 1599 1444 1596External causes 512 509 540 607 542

8 Science and Technology of Nuclear Installations

personal effective dose exceeding 502 25mSv for eachreactor is less than 10minus 62 5 times 10minus7(r middot y)

In fact the individual effective dose and cumulativefrequency caused by the entire plant site are not necessarilythe simple addition of the individual effective dose andcumulative frequency caused by each single reactor How-ever in order to ensure the probabilistic safety goals thevalue of the probabilistic safety goals of each single reactor issmaller than the entire plant site We need to consider thefollowing points

(a) (e safety and reliability of a single reactor is con-stant (e number of reactors on the site needs to becontrolled and cannot be increased indefinitely

(b) (e design of the reactors can still be based on thesingle reactor for the convenience of design But forthe entire plant site we can consider different typesof reactors with different risk levels at the same site

5 Conclusions

According to the statistics on societal risks in China theindividual latent cancer fatality risk (ILCFR) is 16 times 10minus 3yand the individual early prompt fatality risk (IEPFR) is5 times 10minus 4y (e mortality rates are similar in China and theUnited States and the changes in recent years are small (eChinese current probabilistic safety goals can meet the re-quirement of little contribution to social risks

(e probabilistic safety goals of HTR-PM recom-mended by Chinarsquos National Nuclear Safety Adminis-tration (NNSA) are as follows the cumulative frequencyof all beyond-design-basis accident sequences that lead tooff-site (including plant boundary) personal effective doseexceeding 50mSv shall be less than 10minus 6(r middot y) Accordingto the inference the probabilistic safety goals are rationalAnd the risk metric of HTR-PM has large marginaccording to the societal risk of China maybe it can beextended to be applied to the multimodule HTGR asldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y)rdquo

In the end we think it is better that the probabilisticsafety goals based on entire plant site rather than a single

reactor We need to control the number of reactors on onesite and we can consider different types of reactors withdifferent risk levels at the same site And the above analysisprocess is applicable to other types of reactors

Data Availability

(e data used in this paper are obtained from China Na-tional Bureau of Statistics (httpwwwstatsgovcn) andWorld Health Organization (httpswwwwhointdatacollections)

Conflicts of Interest

(e authors declare that they have no conflicts of interestregarding the publication of this paper

Acknowledgments

(is study was supported by the National Science andTechnology Major Project (2018ZX06902015) and the Na-tional Natural Science Foundation of China (Project no71601139)

References

[1] C Meyer ldquoChina and nuclear energy solving an energycrisisndashpart 4rdquo Energize vol 7 no 42 pp 18-19 2011

[2] J Wood ldquoNuclear safety and three major accidentsrdquo NuclearPower IET Digital Library vol 18 no 6 2007

[3] OECDNEA Probabilistic Risk Criteria and Safety GoalsNEACSNIR Organization for Economic Cooperation andDevelopmentNuclear Energy Agency (OECDNEA) ParisFrance 2009

[4] Z Zhang Z Wu and Y Sun ldquoDesign aspects of the Chinesemodular high-temperature gas-cooled reactor HTR-PMrdquoNuclear Engineering amp Design vol 236 no 5-6 pp 485ndash4902006

[5] IAEA ldquoPolicy for setting and assessing regulatory safetygoalsrdquo 1995

[6] EPRI ldquoAdvanced light water reactor utility requirementsdocumentrdquo ALWR Policy and Summary of Top-Tier Re-quirements vol 1 1990

[7] K R KEMA ldquoEuropean utility requirements for LWR nuclearpower plantsrdquo Main Policies and Top Tier RequirementsRevision B vol 1 1995

[8] GPR-RSK ldquoIPSN-GRS proposals for the development oftechnical guideline for future pWRsrdquo 1997

[9] IAEA Safety Series 75-INSAG-3 Basic Safety Principles forNuclear Power Plants IAEA 1988 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

[10] IAEA Safety Series 75-INSAG-12 Basic Safety Principles forNuclear Power Plants IAEA 1999 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

Chinese societal risks

IEPFR 50E ndash 4y

ILCFR 16E ndash 3y

Risks based on quantitativehealth objectives

01 01

Probabilistic safety goals

LERF lt 1E ndash 6(rmiddoty)

CDF lt 1E ndash 5(rmiddoty)

IEPFRNPP 50E ndash 7y

ILCFRNPP 16E ndash 6y

IEPFRNPP 30E ndash 8y

ILCFRNPP 40E ndash 8y

Risks based on probabilisticsafety goals

IER ILR

gt

gt

Figure 3 (e rationality of existing probabilistic safety goals inChina

Science and Technology of Nuclear Installations 9

IER 1113944H

1

EFh lowast LARGEh( 1113857

TP(1) (11)

where EFh is the number of early prompt fatalities within 1mile caused by accident sequence h LARGEh is the fre-quency of fatal LARGE categories caused by accident se-quence h TP(1) is the total population within 1 mile of thenuclear power plant

(en in the population TP(1) the number of earlyprompt fatalities caused by accident sequence h is

EFh CPEFh lowastTP(1) (12)

where CPEFh is the conditional probability of early promptfatalities caused by accident sequence h meaning the con-ditional probability of one personrsquos early fatality caused by aradioactive release nuclear accident

According to formulae (9) and (10) the individual earlyprompt fatality risk is

IER 1113944H

1CPEFh lowast LARGEh (13)

According to the data survey for Chinese societal risksthe individual risk of prompt fatality caused by all otheraccidents is 5 times 10minus 4y in China According to the 01 inthe early quantitative health objective (EQHO) the indi-vidual early risk (IEREQHO) caused by nuclear power plantaccidents needs to be less than 5 times 10minus 7(r middot y) Suppose aworst accident sequence h which has the greatest impact onearly prompt fatalities risk An unscrubbed release occurred

before the surrounding population were effectivelyevacuated

Suppose

IERh CPEFh lowast LARGEh IEREQHO 5 times 10minus 7

(r middot y) (14)

According to the probabilistic safety goals for multi-HTGR LARGEh 1 times 10minus 6(r middot y)

(us CPEFh 05(at is the conditional probability of early prompt fa-

talities caused by the worst accident sequence h is 05 it justmeets the EQHO for individual early prompt fatalities risks

In the International Commission on Radiological Pro-tection (ICPR) Publication 60 according to the dosethreshold of the deterministic effects the 60-day medianlethal dose (LD50[60]) is 3sim5Gytime (e probability ofstochastic effects increases with increasing dose Stochasticeffects include cancer and hereditary diseases For cancerthe probability coefficients of fatal cancer are 5 times 10minus 2Sv forthe public and 4 times 10minus 2Sv for occupational workers en-gaged in radiation For hereditary diseases the probabilitycoefficients of hereditary diseases are 1 times 10minus 2Sv for thepublic and 06 times 10minus 2Sv for workers ICPR 103 followed theconclusion of the ICRP 60 the combined detriment due tofatal cancer and hereditary diseases remains unchanged ataround 5 times 10minus 2Sv For HTR-PM there is extremely lowlarge release frequency and the personal effective dosecontrol threshold is 50mSv According to the results ofabove analysis when LARGEh 1 times 10minus 6(r middot y)andCPEFh 05 the risk metric of HTR-PM can meet the re-quirements of Chinese societal risks In fact the personaleffective dose control threshold is 50mSv and actual CPEFh

is extremely low as well so the risk metric of HTR-PM haslarge margin compared with Chinese societal risk(ereforeit give us the confidence to expand the risk metric of HTR-PM (ie 1 times 10minus 6reactor middot y) to multimodule HTGR (ie1 times 10minus 6(unit middot y) or 1 times 10minus 6(site middot ley)) and then therisk metric of multimodule HTGR can meet the require-ments of Chinese societal risks

4 Discussions

Existing nuclear safety goals is mainly for a single reactorBut in fact most of the plant sites are multireactor sitesMultireactor site means a nuclear power plant site with twoor more reactors on one site From the Fukushima nuclearaccident we realized the possibility and severity of nuclearaccidents occurring at multiple reactors at the same timeNuclear safety goals are set to protect the lives health andenvironment of populations For the populations not onlythe impact of a single reactor on the human body must beconsidered but also the impact of the entire plant site on thehuman body

For example expand the risk metric of HTR-PM from asingle reactor to a plant site and explore the adaptability ofprobabilistic safety goals (e current probabilistic safetygoals of HTR-PM are that the cumulative frequency of allaccident sequences that cause the personal effective dose

Table 3 Demographic mortality statistics in China based on theWHO data

Mortality rate (1100000) 2000 2010 2015 2016Cardiovascular diseases 2128 2696 3095 3171Malignant neoplasms 1444 1599 1663 1679Respiratory diseases 975 712 659 665External causes of damage andpoisoning 607 540 509 512

Neurological condition 206 323 420 449Digestive diseases 183 174 192 197Genitourinary diseases 98 123 149 152Respiratory infectious 192 126 124 126Diabetes mellitus 77 97 116 119Infectious and parasitic diseases 186 120 96 92Neonatal conditions 180 80 54 49Mental and substance use disorders 21 26 31 32Congenital anomalies 67 46 33 31Other neoplasms 15 24 29 29Endocrine blood and immunedisorders 15 14 17 17

Musculoskeletal diseases 11 13 15 15Nutritional deficiencies 14 09 11 11Skin diseases 03 04 05 05Sudden infant death syndrome 01 01 01 01Source World Health Organization statistics [23] Note External causes ofinjury and poisoning include road injury poisonings falls fire heat and hotsubstances drowning exposure to mechanical forces natural disastersother unintentional injuries self-harm interpersonal violence collectiveviolence and legal intervention

Science and Technology of Nuclear Installations 7

outside the plant (including the site boundary) to exceed50mSv is less than 10minus 6(r middot y) Expanding from a singlereactor to a plant site means LARGE 10minus 6(reactor middot year)changed to LARGE 10minus 6(site middot year) (sitemiddotyear smiddoty)

(rough the derivation in Section 4LARGE 10minus 6(s middot y) then CPEFh 05 (at is theconditional probability of early prompt fatalities caused bythe worst accident sequence h in the entire plant site is 05 it

just meets the EQHO for individual early prompt fatalitiesrsquorisks

Suppose there are two reactors in a plant site andsuppose that the two reactors suffer the worst accident se-quence at the same time In order to ensure the probabilisticsafety goals of the multimodule HTGR site and ensure asufficient safety margin it is necessary to ensure the cu-mulative frequency of beyond design basis accidents with a

Table 4 Demographic mortality statistics in different countries

Mortality rate (1100000) China (e US Japan (e UK France India Egypt SudanAll causes 7349 8698 10260 9124 8616 7226 6359 7123Cardiovascular diseases 3171 2599 2808 2287 2216 1956 2570 2029Malignant neoplasms 1679 1948 3129 2557 2679 616 812 446Respiratory diseases 665 767 901 760 480 768 271 221Injuries 512 570 497 318 548 818 367 896Neurological conditions 449 1021 418 1499 995 158 221 163Digestive diseases 197 367 453 435 384 385 834 209Genitourinary diseases 152 267 347 161 164 230 197 198Respiratory infectious diseases 126 206 1107 571 277 466 231 482Diabetes mellitus 119 262 113 100 191 233 187 146Infectious and parasitic diseases 92 175 170 101 154 906 124 1011Neonatal conditions 46 36 05 25 24 415 268 894Mental and substance use disorders 32 149 18 57 92 24 06 16Congenital anomalies 31 40 22 35 30 79 151 180Other neoplasms 29 51 99 60 118 11 38 32Endocrine blood and immune disorders 17 141 82 48 108 16 52 54Musculoskeletal diseases 15 45 52 70 67 37 02 07Nutritional deficiencies 11 30 25 06 65 63 14 34Skin diseases 05 16 15 31 21 10 01 08Maternal conditions 03 02 00 01 01 31 09 90Sudden infant death syndrome 01 05 01 02 02 04 06 09Sense organ diseases 00 00 01 01 Oral conditions 01 01 01 02 00 Source World Health Organization statistics [23]

Table 5 (e mortality rate of malignant neoplasms and external causes in the US

Mortality rate (1100000) 1978 1979 1980 1981 1982 1983 1984 1985Malignant neoplasms 1617 1754 1795 1802 1836 1859 1887 1905External causes 707 706 707 678 638 616 615 612Source World Health Organization statistics [23]

Table 6 (e mortality rate of malignant neoplasms and external causes in China (1)

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017 AverageMalignant neoplasms 1583 1526 1574 1598 1583 1591 1576External causes 462 474 457 446 447 432 453

Table 7 (e mortality rate of malignant neoplasms and external causes in China (2)

Mortality rate (1100000) 2016 2015 2010 2000 AverageMalignant neoplasms 1679 1663 1599 1444 1596External causes 512 509 540 607 542

8 Science and Technology of Nuclear Installations

personal effective dose exceeding 502 25mSv for eachreactor is less than 10minus 62 5 times 10minus7(r middot y)

In fact the individual effective dose and cumulativefrequency caused by the entire plant site are not necessarilythe simple addition of the individual effective dose andcumulative frequency caused by each single reactor How-ever in order to ensure the probabilistic safety goals thevalue of the probabilistic safety goals of each single reactor issmaller than the entire plant site We need to consider thefollowing points

(a) (e safety and reliability of a single reactor is con-stant (e number of reactors on the site needs to becontrolled and cannot be increased indefinitely

(b) (e design of the reactors can still be based on thesingle reactor for the convenience of design But forthe entire plant site we can consider different typesof reactors with different risk levels at the same site

5 Conclusions

According to the statistics on societal risks in China theindividual latent cancer fatality risk (ILCFR) is 16 times 10minus 3yand the individual early prompt fatality risk (IEPFR) is5 times 10minus 4y (e mortality rates are similar in China and theUnited States and the changes in recent years are small (eChinese current probabilistic safety goals can meet the re-quirement of little contribution to social risks

(e probabilistic safety goals of HTR-PM recom-mended by Chinarsquos National Nuclear Safety Adminis-tration (NNSA) are as follows the cumulative frequencyof all beyond-design-basis accident sequences that lead tooff-site (including plant boundary) personal effective doseexceeding 50mSv shall be less than 10minus 6(r middot y) Accordingto the inference the probabilistic safety goals are rationalAnd the risk metric of HTR-PM has large marginaccording to the societal risk of China maybe it can beextended to be applied to the multimodule HTGR asldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y)rdquo

In the end we think it is better that the probabilisticsafety goals based on entire plant site rather than a single

reactor We need to control the number of reactors on onesite and we can consider different types of reactors withdifferent risk levels at the same site And the above analysisprocess is applicable to other types of reactors

Data Availability

(e data used in this paper are obtained from China Na-tional Bureau of Statistics (httpwwwstatsgovcn) andWorld Health Organization (httpswwwwhointdatacollections)

Conflicts of Interest

(e authors declare that they have no conflicts of interestregarding the publication of this paper

Acknowledgments

(is study was supported by the National Science andTechnology Major Project (2018ZX06902015) and the Na-tional Natural Science Foundation of China (Project no71601139)

References

[1] C Meyer ldquoChina and nuclear energy solving an energycrisisndashpart 4rdquo Energize vol 7 no 42 pp 18-19 2011

[2] J Wood ldquoNuclear safety and three major accidentsrdquo NuclearPower IET Digital Library vol 18 no 6 2007

[3] OECDNEA Probabilistic Risk Criteria and Safety GoalsNEACSNIR Organization for Economic Cooperation andDevelopmentNuclear Energy Agency (OECDNEA) ParisFrance 2009

[4] Z Zhang Z Wu and Y Sun ldquoDesign aspects of the Chinesemodular high-temperature gas-cooled reactor HTR-PMrdquoNuclear Engineering amp Design vol 236 no 5-6 pp 485ndash4902006

[5] IAEA ldquoPolicy for setting and assessing regulatory safetygoalsrdquo 1995

[6] EPRI ldquoAdvanced light water reactor utility requirementsdocumentrdquo ALWR Policy and Summary of Top-Tier Re-quirements vol 1 1990

[7] K R KEMA ldquoEuropean utility requirements for LWR nuclearpower plantsrdquo Main Policies and Top Tier RequirementsRevision B vol 1 1995

[8] GPR-RSK ldquoIPSN-GRS proposals for the development oftechnical guideline for future pWRsrdquo 1997

[9] IAEA Safety Series 75-INSAG-3 Basic Safety Principles forNuclear Power Plants IAEA 1988 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

[10] IAEA Safety Series 75-INSAG-12 Basic Safety Principles forNuclear Power Plants IAEA 1999 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

Chinese societal risks

IEPFR 50E ndash 4y

ILCFR 16E ndash 3y

Risks based on quantitativehealth objectives

01 01

Probabilistic safety goals

LERF lt 1E ndash 6(rmiddoty)

CDF lt 1E ndash 5(rmiddoty)

IEPFRNPP 50E ndash 7y

ILCFRNPP 16E ndash 6y

IEPFRNPP 30E ndash 8y

ILCFRNPP 40E ndash 8y

Risks based on probabilisticsafety goals

IER ILR

gt

gt

Figure 3 (e rationality of existing probabilistic safety goals inChina

Science and Technology of Nuclear Installations 9

outside the plant (including the site boundary) to exceed50mSv is less than 10minus 6(r middot y) Expanding from a singlereactor to a plant site means LARGE 10minus 6(reactor middot year)changed to LARGE 10minus 6(site middot year) (sitemiddotyear smiddoty)

(rough the derivation in Section 4LARGE 10minus 6(s middot y) then CPEFh 05 (at is theconditional probability of early prompt fatalities caused bythe worst accident sequence h in the entire plant site is 05 it

just meets the EQHO for individual early prompt fatalitiesrsquorisks

Suppose there are two reactors in a plant site andsuppose that the two reactors suffer the worst accident se-quence at the same time In order to ensure the probabilisticsafety goals of the multimodule HTGR site and ensure asufficient safety margin it is necessary to ensure the cu-mulative frequency of beyond design basis accidents with a

Table 4 Demographic mortality statistics in different countries

Mortality rate (1100000) China (e US Japan (e UK France India Egypt SudanAll causes 7349 8698 10260 9124 8616 7226 6359 7123Cardiovascular diseases 3171 2599 2808 2287 2216 1956 2570 2029Malignant neoplasms 1679 1948 3129 2557 2679 616 812 446Respiratory diseases 665 767 901 760 480 768 271 221Injuries 512 570 497 318 548 818 367 896Neurological conditions 449 1021 418 1499 995 158 221 163Digestive diseases 197 367 453 435 384 385 834 209Genitourinary diseases 152 267 347 161 164 230 197 198Respiratory infectious diseases 126 206 1107 571 277 466 231 482Diabetes mellitus 119 262 113 100 191 233 187 146Infectious and parasitic diseases 92 175 170 101 154 906 124 1011Neonatal conditions 46 36 05 25 24 415 268 894Mental and substance use disorders 32 149 18 57 92 24 06 16Congenital anomalies 31 40 22 35 30 79 151 180Other neoplasms 29 51 99 60 118 11 38 32Endocrine blood and immune disorders 17 141 82 48 108 16 52 54Musculoskeletal diseases 15 45 52 70 67 37 02 07Nutritional deficiencies 11 30 25 06 65 63 14 34Skin diseases 05 16 15 31 21 10 01 08Maternal conditions 03 02 00 01 01 31 09 90Sudden infant death syndrome 01 05 01 02 02 04 06 09Sense organ diseases 00 00 01 01 Oral conditions 01 01 01 02 00 Source World Health Organization statistics [23]

Table 5 (e mortality rate of malignant neoplasms and external causes in the US

Mortality rate (1100000) 1978 1979 1980 1981 1982 1983 1984 1985Malignant neoplasms 1617 1754 1795 1802 1836 1859 1887 1905External causes 707 706 707 678 638 616 615 612Source World Health Organization statistics [23]

Table 6 (e mortality rate of malignant neoplasms and external causes in China (1)

Mortality rate (1100000) 2012 2013 2014 2015 2016 2017 AverageMalignant neoplasms 1583 1526 1574 1598 1583 1591 1576External causes 462 474 457 446 447 432 453

Table 7 (e mortality rate of malignant neoplasms and external causes in China (2)

Mortality rate (1100000) 2016 2015 2010 2000 AverageMalignant neoplasms 1679 1663 1599 1444 1596External causes 512 509 540 607 542

8 Science and Technology of Nuclear Installations

personal effective dose exceeding 502 25mSv for eachreactor is less than 10minus 62 5 times 10minus7(r middot y)

In fact the individual effective dose and cumulativefrequency caused by the entire plant site are not necessarilythe simple addition of the individual effective dose andcumulative frequency caused by each single reactor How-ever in order to ensure the probabilistic safety goals thevalue of the probabilistic safety goals of each single reactor issmaller than the entire plant site We need to consider thefollowing points

(a) (e safety and reliability of a single reactor is con-stant (e number of reactors on the site needs to becontrolled and cannot be increased indefinitely

(b) (e design of the reactors can still be based on thesingle reactor for the convenience of design But forthe entire plant site we can consider different typesof reactors with different risk levels at the same site

5 Conclusions

According to the statistics on societal risks in China theindividual latent cancer fatality risk (ILCFR) is 16 times 10minus 3yand the individual early prompt fatality risk (IEPFR) is5 times 10minus 4y (e mortality rates are similar in China and theUnited States and the changes in recent years are small (eChinese current probabilistic safety goals can meet the re-quirement of little contribution to social risks

(e probabilistic safety goals of HTR-PM recom-mended by Chinarsquos National Nuclear Safety Adminis-tration (NNSA) are as follows the cumulative frequencyof all beyond-design-basis accident sequences that lead tooff-site (including plant boundary) personal effective doseexceeding 50mSv shall be less than 10minus 6(r middot y) Accordingto the inference the probabilistic safety goals are rationalAnd the risk metric of HTR-PM has large marginaccording to the societal risk of China maybe it can beextended to be applied to the multimodule HTGR asldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y)rdquo

In the end we think it is better that the probabilisticsafety goals based on entire plant site rather than a single

reactor We need to control the number of reactors on onesite and we can consider different types of reactors withdifferent risk levels at the same site And the above analysisprocess is applicable to other types of reactors

Data Availability

(e data used in this paper are obtained from China Na-tional Bureau of Statistics (httpwwwstatsgovcn) andWorld Health Organization (httpswwwwhointdatacollections)

Conflicts of Interest

(e authors declare that they have no conflicts of interestregarding the publication of this paper

Acknowledgments

(is study was supported by the National Science andTechnology Major Project (2018ZX06902015) and the Na-tional Natural Science Foundation of China (Project no71601139)

References

[1] C Meyer ldquoChina and nuclear energy solving an energycrisisndashpart 4rdquo Energize vol 7 no 42 pp 18-19 2011

[2] J Wood ldquoNuclear safety and three major accidentsrdquo NuclearPower IET Digital Library vol 18 no 6 2007

[3] OECDNEA Probabilistic Risk Criteria and Safety GoalsNEACSNIR Organization for Economic Cooperation andDevelopmentNuclear Energy Agency (OECDNEA) ParisFrance 2009

[4] Z Zhang Z Wu and Y Sun ldquoDesign aspects of the Chinesemodular high-temperature gas-cooled reactor HTR-PMrdquoNuclear Engineering amp Design vol 236 no 5-6 pp 485ndash4902006

[5] IAEA ldquoPolicy for setting and assessing regulatory safetygoalsrdquo 1995

[6] EPRI ldquoAdvanced light water reactor utility requirementsdocumentrdquo ALWR Policy and Summary of Top-Tier Re-quirements vol 1 1990

[7] K R KEMA ldquoEuropean utility requirements for LWR nuclearpower plantsrdquo Main Policies and Top Tier RequirementsRevision B vol 1 1995

[8] GPR-RSK ldquoIPSN-GRS proposals for the development oftechnical guideline for future pWRsrdquo 1997

[9] IAEA Safety Series 75-INSAG-3 Basic Safety Principles forNuclear Power Plants IAEA 1988 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

[10] IAEA Safety Series 75-INSAG-12 Basic Safety Principles forNuclear Power Plants IAEA 1999 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

Chinese societal risks

IEPFR 50E ndash 4y

ILCFR 16E ndash 3y

Risks based on quantitativehealth objectives

01 01

Probabilistic safety goals

LERF lt 1E ndash 6(rmiddoty)

CDF lt 1E ndash 5(rmiddoty)

IEPFRNPP 50E ndash 7y

ILCFRNPP 16E ndash 6y

IEPFRNPP 30E ndash 8y

ILCFRNPP 40E ndash 8y

Risks based on probabilisticsafety goals

IER ILR

gt

gt

Figure 3 (e rationality of existing probabilistic safety goals inChina

Science and Technology of Nuclear Installations 9

personal effective dose exceeding 502 25mSv for eachreactor is less than 10minus 62 5 times 10minus7(r middot y)

In fact the individual effective dose and cumulativefrequency caused by the entire plant site are not necessarilythe simple addition of the individual effective dose andcumulative frequency caused by each single reactor How-ever in order to ensure the probabilistic safety goals thevalue of the probabilistic safety goals of each single reactor issmaller than the entire plant site We need to consider thefollowing points

(a) (e safety and reliability of a single reactor is con-stant (e number of reactors on the site needs to becontrolled and cannot be increased indefinitely

(b) (e design of the reactors can still be based on thesingle reactor for the convenience of design But forthe entire plant site we can consider different typesof reactors with different risk levels at the same site

5 Conclusions

According to the statistics on societal risks in China theindividual latent cancer fatality risk (ILCFR) is 16 times 10minus 3yand the individual early prompt fatality risk (IEPFR) is5 times 10minus 4y (e mortality rates are similar in China and theUnited States and the changes in recent years are small (eChinese current probabilistic safety goals can meet the re-quirement of little contribution to social risks

(e probabilistic safety goals of HTR-PM recom-mended by Chinarsquos National Nuclear Safety Adminis-tration (NNSA) are as follows the cumulative frequencyof all beyond-design-basis accident sequences that lead tooff-site (including plant boundary) personal effective doseexceeding 50mSv shall be less than 10minus 6(r middot y) Accordingto the inference the probabilistic safety goals are rationalAnd the risk metric of HTR-PM has large marginaccording to the societal risk of China maybe it can beextended to be applied to the multimodule HTGR asldquofrequency of LARGE release category less than10minus 6(unit middot y) or 10minus 6(site middot y)rdquo

In the end we think it is better that the probabilisticsafety goals based on entire plant site rather than a single

reactor We need to control the number of reactors on onesite and we can consider different types of reactors withdifferent risk levels at the same site And the above analysisprocess is applicable to other types of reactors

Data Availability

(e data used in this paper are obtained from China Na-tional Bureau of Statistics (httpwwwstatsgovcn) andWorld Health Organization (httpswwwwhointdatacollections)

Conflicts of Interest

(e authors declare that they have no conflicts of interestregarding the publication of this paper

Acknowledgments

(is study was supported by the National Science andTechnology Major Project (2018ZX06902015) and the Na-tional Natural Science Foundation of China (Project no71601139)

References

[1] C Meyer ldquoChina and nuclear energy solving an energycrisisndashpart 4rdquo Energize vol 7 no 42 pp 18-19 2011

[2] J Wood ldquoNuclear safety and three major accidentsrdquo NuclearPower IET Digital Library vol 18 no 6 2007

[3] OECDNEA Probabilistic Risk Criteria and Safety GoalsNEACSNIR Organization for Economic Cooperation andDevelopmentNuclear Energy Agency (OECDNEA) ParisFrance 2009

[4] Z Zhang Z Wu and Y Sun ldquoDesign aspects of the Chinesemodular high-temperature gas-cooled reactor HTR-PMrdquoNuclear Engineering amp Design vol 236 no 5-6 pp 485ndash4902006

[5] IAEA ldquoPolicy for setting and assessing regulatory safetygoalsrdquo 1995

[6] EPRI ldquoAdvanced light water reactor utility requirementsdocumentrdquo ALWR Policy and Summary of Top-Tier Re-quirements vol 1 1990

[7] K R KEMA ldquoEuropean utility requirements for LWR nuclearpower plantsrdquo Main Policies and Top Tier RequirementsRevision B vol 1 1995

[8] GPR-RSK ldquoIPSN-GRS proposals for the development oftechnical guideline for future pWRsrdquo 1997

[9] IAEA Safety Series 75-INSAG-3 Basic Safety Principles forNuclear Power Plants IAEA 1988 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

[10] IAEA Safety Series 75-INSAG-12 Basic Safety Principles forNuclear Power Plants IAEA 1999 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

Chinese societal risks

IEPFR 50E ndash 4y

ILCFR 16E ndash 3y

Risks based on quantitativehealth objectives

01 01

Probabilistic safety goals

LERF lt 1E ndash 6(rmiddoty)

CDF lt 1E ndash 5(rmiddoty)

IEPFRNPP 50E ndash 7y

ILCFRNPP 16E ndash 6y

IEPFRNPP 30E ndash 8y

ILCFRNPP 40E ndash 8y

Risks based on probabilisticsafety goals

IER ILR

gt

gt

Figure 3 (e rationality of existing probabilistic safety goals inChina

Science and Technology of Nuclear Installations 9

[11] IAEA Safety Standards Series NoNS-R-1 Safety of NuclearPower Plants Design IAEA 2000 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

[12] IAEA Safety Standards Series NoNS-G-12 Safety Assessmentand Verification for Nuclear Power Plants IAEA 2001 httpswwwgooglecomsearchrlz=1C1GCEJ_enIN954IN954ampq=Viennaampstick=H4sIAAAAAAAAAOPgE-LQz9U3MC43slACs9IyCiy1tLKTrfTzi9IT8zKrEksy8_NQOFYZqYkphaWJRSWpRcWLWNnCMlPz8hJ3sDICANR77yBOAAAAampsa=Xampved=2ahUKEwipg5u38-zwAhULIbcAHc0pBCcQmxMoATA4egQINRAD

[13] USNRC 51 Federal Register 7023 Safety Goals for the Op-eration of Nuclear Power Plants Policy Statement USNRCRockville MD USA 1982

[14] USNRC 51 Federal Register 10772 Safety Goals for the Op-eration of Nuclear Power Plants Policy Statement USNRCRockville MD USA 1983

[15] USNRC 51 Federal Register 30028 Safety Goals for the Op-eration of Nuclear Power Plants Policy Statement Republi-cation Federal Register USNRC Rockville MD USA 1986

[16] China National Nuclear Safety Administration Provisions onDesign Safety of Nuclear Power Plant HAF102 NationalNuclear Safety Administration 1991 Beijing China 2016

[17] China National Nuclear Safety Administration Safety Eval-uation and Validation of Nuclear Power Plant NationalNuclear Safety Administration Beijing China 2006

[18] China National Nuclear Safety Administration Twelfth Five-Year Plan and Vision 2020 for Nuclear Safety and RadioactivePollution Prevention Beijing China Environmental NewsBeijing China 2012

[19] China National Nuclear Safety Administration CirteenthFive-Year Plan and Vision 2025 for Nuclear Safety and Ra-dioactive Pollution Prevention Beijing China EnvironmentalNews Beijing China 2017

[20] USNRC NUREG-1860 Feasibility Study for a Risk-Informedand Performance-Based Regulatory Structure for Future PlantLicensing Washing DC United States Nuclear RegulatoryCommission Washington DC USA 2007

[21] China National Health Commission China Health StatisticalYearbook China UnionMedical College Press Beijing China2017

[22] China National Bureau of Statistics National Economic andSocietal Development Statistical Bulletin National Bureau ofStatistics Beijing China 2017

[23] World Health Organization Global Health Estimates Sum-mary Tables WHO Geneva Switzerland 2021 httpwwwwhointhealthinfoglobal_burden_diseaseen

[24] (eWorld Bank Free and Open Access to Global DevelopmentData (e World Bank Washington DC USA 2021 httpsdataworldbankorg

10 Science and Technology of Nuclear Installations