UK Protective Marking: UK HPR1000...the BSSD (2013) was revised in Reference [13] to reflect the requirements in the 2007 recommendations of the ICRP in Reference [14]. The EPR16,

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Pre-Construction Environmental Report Chapter 7 Radiological Assessment

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DISTRIBUTION LIST

Recipients Cross Box

General Nuclear System Executive ☐

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General Nuclear System and BRB all staff ☒

CGN ☒

EDF ☒

Regulators ☒

Public ☒

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TABLE OF CONTENTS

7.1 List of Abbreviations and Acronyms .................................................................... 3

7.2 Introduction ............................................................................................................ 4

7.3 Regulatory Context ................................................................................................ 6

7.3.1 Legislative Background ................................................................................. 6

7.3.2 Radioactive Substances Regulation Guidance ............................................... 7

7.4 Common Assumptions on the Generic Site ......................................................... 8

7.5 Direct Dose .............................................................................................................. 8

7.5.1 Methodology .................................................................................................. 9

7.5.2 Input Data ...................................................................................................... 9

7.5.3 Results and Discussion ................................................................................ 10

7.6 Dose to the Most Exposed Members of the Public ............................................ 10

7.6.1 Overview of the Radiological Assessment Methodologies ......................... 10

7.6.2 Stage 1 Assessment ...................................................................................... 12



7.7 Annual Dose to the Representative Person ........................................................ 23

7.7.1 Methodology ................................................................................................ 23

7.7.2 Input Data .................................................................................................... 24


7.8 Potential Dose due to the Short-term Discharge ............................................... 26

7.8.1 Methodology ................................................................................................ 26

7.8.2 Input Data .................................................................................................... 28


7.9 Comparison of the Calculated Doses with Relevant Dose Constraints ........... 33

7.10 Environmental Accumulation ........................................................................... 39

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7.10.1 Methodology .............................................................................................. 39

7.10.2 Input Data .................................................................................................. 42

7.10.3 Results and Discussion .............................................................................. 42

7.11 Assessment of Collective Dose ........................................................................... 44

7.11.1 Methodology .............................................................................................. 44

7.11.2 Input Data ................................................................................................... 45

7.11.3 Results and Discussion............................................................................... 45

7.12 Potential Dose Rate to Non-human Biota ........................................................ 47

7.12.1 Methodologies ........................................................................................... 47

7.12.2 Input Data .................................................................................................. 48

7.12.3 Results and Discussion .............................................................................. 50

7.13 Uncertainty and Variability .............................................................................. 51

7.14 Conclusions ......................................................................................................... 53

7.15 References ........................................................................................................... 55

Appendix 7A Results of Radiological Assessment ................................................... 58

Appendix 7B Other Tables ...................................................................................... 187

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7.1 List of Abbreviations and Acronyms ADMS Atmospheric Dispersion Modelling System

BAT Best Available Technique

BQF Spent Fuel Interim Storage

BQZ Interim Storage Facility for Intermediate Level Waste

BSSD Basic Safety Standards Directive

CGN China General Nuclear Power Corporation

DPUR Dose Per Unit Release

EA Environment Agency (UK)

EMCL Environmental Media Concentration Limit

EPR16 Environmental Permitting Regulations 2016 (England and Wales)

ERICA

Environmental Risk from Ionising Contaminants: Assessment and Management

FSA Food Standards Agency

GDA Generic Design Assessment

HPA Health Protection Agency (UK)

HPR1000 (FCG3)

Hua-long Pressurised Reactor under construction at Fangchenggang nuclear power plant unit 3

IAEA International Atomic Energy Agency

ICRP International Commission on Radiological Protection

ILW Intermediate Level Waste

IRA Initial Radiological Assessment

NHB Non-human Biota

NRPB National Radiological Protection Board (UK)

OPEX Operating Experience

P&ID Process and Information Document for Generic Assessment of Candidate Nuclear Power Plant Designs

PCER Pre-Construction Environmental Report

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PHE Public Health England

RGP Relevant Good Practice

RQ Risk Quotient

UF Uncertainty Factor

UK HPR1000 UK version of the Hua-long Pressurised Reactor

7.2 Introduction This chapter presents information pertaining to the likely impact on the environment and members of the public on the generic site from radioactive discharges and direct radiation arising from the normal operation of the UK version of the Hua-long Pressurised Reactor (UK HPR1000). This chapter is provided to satisfy the Environment Agency (EA)’s requirements as set out in item 7 of Table 1 of the Process and Information Document for Generic Assessment of Candidate Nuclear Power Plant Designs (P&ID) in Reference [1] which comprise the following：

• annual dose to most exposed members of the public for liquid discharges;

• annual dose to most exposed members of the public for gaseous discharges (identifying separately the dose associated with on-site incineration where applicable);

• annual dose to the most exposed members of the public for all discharges from the facility;

• annual dose from direct radiation to the most exposed member of the public;

• annual dose to the representative person for the facility;

• potential short-term doses, including via the food chain, based on the maximum anticipated short-term discharges from the facility in normal operation;

• a comparison of the calculated doses with the relevant dose constraints;

• an assessment of whether the build-up of radionuclides in the local environment of the facility, based on the anticipated lifetime discharges, might have the potential to prejudice legitimate users or uses of the land or sea;

• collective dose truncated at 500 years to the UK, European and world populations;

• dose-rate to non-human species.

The radiological assessment in this document is also conducted to demonstrate that the UK HPR1000 complies with the requirements of the Environmental Permitting Regulation (England and Wales) 2016 (EPR16) in Reference [2] and [3].

During step 3 of Generic Design Assessment (GDA) process, the radiological

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assessments from radioactive maximum annual discharges and direct exposure due to normal operation of the UK HPR1000 have been conducted to assess the prospective radiological impact on members of the public and the Non-Human Biota (NHB). The collective dose, the potential impacts on the surrounding land due to the accumulation of radioactive discharges and the potential radiological impact of short-term discharges have also been assessed.

The UK HPR1000’s maximum annual discharges have been revised based on the enrichment of the Operating Experience (OPEX) data and refinement of expected events contribution, which is produced based on the design reference version 2.1. The Environmental Risk from Ionising Contaminants: Assessment and Management (ERICA) tool has been improved since the step 3 of GDA. The feedback from the step 3 of GDA and the radiological assessments based on the refined maximum annual discharges and the updated ERICA tool are reflected in this document. The assessments in this chapter are based on the design reference 2.1 in Reference [4].

A number of models are used for estimating the impact of radioactive discharges on members of the public and NHBs, which are presented as follows:

a) The Initial Radiological Assessment (IRA) tool in Reference [5] and [6] is used to provide a system for undertaking an initial cautious prospective assessment of the dose arising from radioactive wastes discharged to the environment;

b) PC-CREAM 08, Reference [7], is used for conducting realistic prospective assessment of public dose, collective dose and assessing impact of the accumulation of radioactive material in the environment from continuous discharges;

c) The gaseous dispersion model in Atmospheric Dispersion Modelling System (ADMS) 5, Reference [8], is used to calculate the activity concentrations in air, deposition rate on land and the cloud gamma doses per unit discharge from short-term discharges;

d) The Environmental Risk from Ionising Contaminants: Assessment and Management (ERICA), Reference [9], and the Ar-Kr-Xe calculation tool, Reference [10], are used for the NHBs radiological dose assessment arising from continuous sources of radioactive waste discharged to the environment.

This chapter has a number of interfaces with other chapters of PCER, which are presented in T-7.2-1.

T-7.2-1 Interface with Other PCER Chapters

Chapter Interface Relationship

PCER Chapter 1 PCER Chapter 1 provides the summary of each PCER

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Chapter Interface Relationship

Introduction chapter and the P&ID route map

PCER Chapter 2 Generic Site Description

PCER Chapter 2 provides generic site description to support the radiological assessment

PCER Chapter 3 Demonstration of BAT

PCER Chapter 7 provides the radiological assessment results to support demonstration of Best Available

Technique (BAT) in PCER Chapter 3

PCER Chapter 6 Quantification of

Discharges & Limits

PCER Chapter 6 provides maximum annual discharges and short-term release as input for PCER Chapter 7.

PCER Chapter 7 provides the radiological impact assessment results based on maximum annual

discharges to support the selection of significant radionuclides for PCER Chapter 6.

7.3 Regulatory Context 7.3.1 Legislative Background

The Euratom Basic Safety Standards Directive (BSSD) (1996) in Reference [11] provides the mechanism for the implementation of the 1990 recommendations of International Commission on Radiological Protection (ICRP) in Reference [12]. And the BSSD (2013) was revised in Reference [13] to reflect the requirements in the 2007 recommendations of the ICRP in Reference [14].

The EPR16, Reference [2] and [3], transfers components of the BSSD (2013) into UK domestic legislation. The principle aims of this legislation are to require that the appropriate environment agencies, when exercising their duties and functions under radioactive substances legislation, ensure:

a) All public ionising radiation exposures from radioactive waste disposals are kept as low as reasonably achievable, with economic and social factors taken into account;

b) The sum of the doses arising from such exposures does not exceed the individual public dose limit of 1 mSv/y;

c) The dose does not exceed 0.3 mSv/y from any source from which radioactive discharges are first made on or after 13th May 2000;

d) The dose does not exceed 0.5 mSv/y from the any single site discharges.

In addition to the permitting requirements, the UK has produced a strategy for discharges in Reference [15] which states that the application of BAT in England and

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Wales to ensure that discharges from new nuclear power stations constructed in the UK do not exceed those from comparable power stations across the world.

The Health Protection Agency (HPA) (now known as Public Health England (PHE)) has suggested a dose constraint of 0.15 mSv/y for any new nuclear power station in Reference [16]. However, this is not currently enacted into UK legislation.

7.3.2 Radioactive Substances Regulation Guidance

The Radioactive Substances Regulation Environmental Principles in Reference [17] provides the objective for radioactive substances regulation, fundamental principles and generic developed principles for the protection of people and the environment against radioactivity, which including:

a) RPDP2: Radiation doses to individual people shall be below the relevant dose limits and in general should be below the relevant constraints;

b) RPDP3: NHBs should be adequately protected from exposure to ionising radiation;

c) RPDP4: Assessments of potential doses to people and to non-human species should be made prior to granting any new or revised permit for the discharge of radioactive wastes into the environment.

The EA, Scottish Environment Protection Agency and the Department of Environment in Northern Ireland (now Northern Ireland Environment Agency) in collaboration with the Food Standards Agency (FSA) and National Radiological Protection Board (NRPB) have developed and published principles and guidance for prospective assessment of public doses in the Reference [18]. This guidance sets out 13 general dose assessment principles, and several important principles for the prospective assessment of doses, which include:

a) When determining discharge permits or authorisations, the dose to the representative person should be assessed;

b) Doses to the most affected age group should be assessed for the purpose of determining discharge permits or authorisations. Assessment of doses to 1 year old, 10 year old and adults (and fetus when appropriate) provides adequate age group coverage;

c) The dose to the representative person which is assessed for comparison with the source constraint and, if appropriate, the site constraint, should include all reasonably foreseeable and relevant future exposure pathways;

d) Where a cautious estimate of the dose to the representative person exceeds 0.02 mSv/y, the assessments should be refined and, where appropriate, more realistic assumptions made. However, sufficient caution should be retained in assessments to provide confidence that actual doses received by the representative person will

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be below the dose limit;

e) The assessment of dose to the representative person should take account of accumulation of radionuclides in the environment from future discharges;

f) The dose assessed for operational short term release at notification levels or limits should be compared with the source constraint (maximum of 0.3 mSv/y) and the dose limit (1 mSv/y), taking into account remaining continuous discharges during the remainder of the year and contributions from other relevant sources under control;

g) For permitting or authorisation purposes, collective doses to the populations of UK, Europe and the world, truncated at 500 y, should be estimated;

h) Where the assessed mean dose to the representative person exceeds 0.02 mSv/y, the uncertainty and variability in the key assumptions used for the dose assessment should be reviewed.

7.4 Common Assumptions on the Generic Site According to the description in PCER Chapter 2, the generic site is assumed to be a coastal site, and located in an agricultural area with no freshwater ecosystems on or close to the site based on the location of potential sites identified in the UK Government’s National Policy Statement for Nuclear Power Generation (EN-6) in Reference [19].

The main assumptions about the generic site for the UK HPR1000 are:

a) The site is an estuarine/marine environmental site and the topography of the site is flat;

b) There is no water extraction from aquifers and no standing water on the site;

c) There are no freshwater bodies on or close to the site;

d) The nearest human receptors are assumed to be a fisherman family for liquid discharges and local resident family for gaseous discharges;

e) Discharge routes are assumed to be gaseous aerial discharges and liquid discharges to the coastal/estuarine environment;

f) There is no on-site incineration.

The layout of the UK HPR1000 is shown in PCER Chapter 2.

7.5 Direct Dose The direct dose is an important component to the overall doses received by both the most exposed groups as well as the representative person. This section describes how this dose is calculated.

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7.5.1 Methodology

The doses from direct radiation are difficult to be measured as they have to be distinguished from the dose associated with other discharge routes as well as natural radiation. There is no available data from similar plants, so the direct doses from sources on site are estimated by the following two steps:

• Step 1, where the sources on site are simulated, at specific distances, and the dose rates calculated using a Monte Carlo code.

• Step 2, where doses to members of the public are calculated from Step 1 using assumed habit data. The overall dose at the receptor location is equal to the dose rate at this location multiplied by the exposure time, taking into account the reduced dose rate while indoors, which is presented as:

Direct Dose (µSv/y) = Drs × [(Sfo × Tfo) + (Sfi × Tfi)] (7.5-1) Where:

Drs: External dose rate, μSv/h;

Sfo: Location factor for being outdoors;

Sfi: Location factor for being indoors;

Tfo: Hours per year spent outdoors, h/y; and,

Tfi: Hours per year spent indoors, h/y.

7.5.2 Input Data

a) Dose rates

The sources on site, with the potential for direct dose to members of the public, include the Reactor Building, Radioactive Waste Treatment Building, Fuel Building, the Nuclear Auxiliary Building, Interim Storage Facility for Intermediate Level Waste (BQZ) and the Spent Fuel Interim Storage (BQF). It is proposed to conduct conceptual design for the BQZ and the BQF in the GDA stage as they are highly site specific, Reference [20]. The source term and location of these two facilities are not determined at present. Therefore, the direct dose to public from the BQZ and the BQF are performed based on a conceptual design in this report to have a preliminary understanding of their contribution to public dose. The direct radiation from these facilities will be assessed in detail at the site specific stage. The detailed calculation methodology and assumptions of the whole sources on site are presented in public dose evaluation from direct radiation topic report, Reference [21].

The general layout of the UK HPR1000 is site specific, and is impacted by the topography, geology, meteorology, transport conditions and other factors of the future site. The future site layout will be designed to be environment-friendly, safe,

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economic as well as easy to construct, operate, maintain and decommission. In the GDA stage, the layout of the UK HPR1000 cannot be accurately described, it is conservatively assumed that members of the public are located at 100 m from these facilities, as demonstrated in PCER Chapter 2.

The dose rates at 100 m from these facilities are presented in T-7B-1.

b) Habits data

The habits data of members of the public who are considered for the calculation of the direct dose from sources within the UK HPR1000 is presented in T-2.4-4 of PCER Chapter 2, including the occupancy time (h/y), location factor, fraction of time indoors and outdoors.

7.5.3 Results and Discussion

The results of the direct dose to adult, child and infant are presented in T-7.5-1.

T-7.5-1 Total Direct Doses to the Different Age Groups

Age Group Direct Dose (µSv/y)

Adult 8.0

Child 4.1

Infant 2.8

The total direct doses to the adult, child and infant are 8.0 µSv/y, 4.1 μSv/y and 2.8 μSv/y, respectively.

From T-7.5-1, the adult group receives the highest dose from direct radiation, 8.0 µSv/y, which is primarily attributed to their higher outdoor occupancy compared to the child and infant groups.

7.6 Dose to the Most Exposed Members of the Public 7.6.1 Overview of the Radiological Assessment Methodologies

A staged approach to the assessment of dose to members of the public is recommended in Reference [18]. The IRA methodology used for the first two stages of dose assessment has been developed to calculate doses in a simple, cautious and consistent manner, which would not be suitable for conducting a detailed assessment for stage 3 dose assessment. For the last stage and in line with Relevant Good Practice (RGP), PC-CREAM 08 is selected for the detailed assessment. The staged approach to the assessment is summarised here:

a) Stage 1 – Initial radiological assessment using default data within IRA

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methodology. If assessed dose is >20 μSv/y, then proceed to stage 2 assessment;

b) Stage 2 – Initial radiological assessment using refined data within IRA methodology. If assessed dose is >20 μSv/y, then proceed to stage 3 assessment;

c) Stage 3 – The realistic radiological assessment using generic site parameters.

7.6.1.1 IRA Methodology

The IRA methodology used in the stage 1 and stage 2 radiological assessments is based on the Dose Per Unit Release (DPUR) values in Reference [5] for different radionuclides, different release routes and different exposure pathways. The initial doses to members of the public are calculated by multiplying DPUR values by the maximum annual discharges and scaling factors (scaling factor are only used in stage 2 radiological assessment).

The IRA methodology is appropriate for the initial radiological assessment of the UK HPR1000 and is presented here:

a) IRA methodology recommended in the P&ID, Reference [1], is in line with RGP. It is a staged approach for the first two stage radiological assessments commonly used for GDA dose assessment;

b) IRA has been developed to facilitate conducting a simple and cautious assessment of the dose to the most exposed group:

1) The DPUR values have been derived for 4 discharge scenarios (discharge to air, estuary/coastal water, river and sewer), 100 radionuclides and 7 exposure groups, and include a total of 41 exposure pathways;

2) The DPUR values presented in the IRA methodology are the highest DPUR factors for each radionuclide regardless of age groups, thus the dose to a specific age group is conservative;

3) IRA methodology is based on exposure pathways and groups which are likely to be the worst affected for a particular discharge route.

c) Dose assessments to the most exposed members of the public are also included in China General Nuclear Power Corporation (CGN)’s radiological assessment. However, CGN’s methodology differs from the approach described above and adopted for the UK HPR1000. This is mainly due to:

1) CGN’s methodology is developed to reflect relevant requirements in the Chinese guidance in Reference [22], which require a collective dose assessment to members of the public who live within the 80 km around the site. Therefore this methodology is not appropriate to be used for calculating the collective dose to the UK, the EU and the whole world;

2) The methodology highly relies on site specific data such as meteorological

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data, habit data, demography, and dilution factors etc., these are not available during the GDA process.

7.6.1.2 PC-CREAM 08

The PC-CREAM 08 is a computer code comprising a suite of models and data that was developed by HPA (now PHE) and tailored to UK legislative requirements, which is appropriate to be used for the stage 3 assessment as it has been verified against environment data as described in Reference [7], and has been used broadly for many other assessments in the UK.

PC-CREAM 08 consists of a number of sub modules. The main divisions of the program are “Models” and “ASSESSOR”. The “Models” includes a series of mathematical modules used to predict the transfer of radionuclides through the environment and to estimate the activity concentrations in various environmental media following a continuous release, Reference [7]. These modules are:

• Atmospheric dispersion module (PLUME);

• Transfer of radionuclides through the soil and gamma radiation from radionuclides deposited on the ground (GRANIS);

• Transfer of radionuclides into terrestrial foods following deposition onto the ground (FARMLAND);

• Estimate the activity concentrations in air arising from the resuspension of previously deposited radionuclides (RESUS);

• Marine dispersion module (DORIS).

The outputs of these modules are then put into the dose assessment part of the program, “ASSESSOR”, to enable the assessment of the individual and collective dose for the UK, European and the whole world due to gaseous and liquid discharges.

7.6.2 Stage 1 Assessment

7.6.2.1 Methodology

a) Liquid discharge

The fisherman family is identified as the most exposed group for liquid discharges in the IRA methodology. The relevant pathways are:

1) External exposure from radionuclides deposited on shore sediments; and

2) Internal exposure through consumption of seafood incorporating radionuclides with conservative habits.

Inhalation of sea spray, inhalation of resuspended sediment, inadvertent ingestion of seawater and external irradiation from the handling of fishing gear are not included, since the resulting doses are much smaller than doses from the pathways listed above,

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these are presented in Reference [23].

The initial assessment of doses to members of the public are calculated by multiplying DPUR values by the liquid maximum annual discharges. The DPUR values for coastal discharge scenario are derived from Appendix E of Reference [6], and the key assumptions in the calculation of DPUR values are that 50% of the fish and all other marine foods are caught from local compartment modeled as a “theoretical box” along the coast and the minimum volumetric exchange rate for most large estuaries and coastal areas is likely to be 100 m3/s.

When DPUR values are not available for several radionuclides in Reference [5], surrogate radionuclide can be used as recommended in Reference [5], and the specific surrogate radionuclide is selected in PCER Sub-chapter 7.6.2.2.

b) Gaseous discharge

In the IRA methodology, the local resident family is identified as the most exposed group for gaseous discharges. The relevant exposure pathways are:

1) Inhalation of radionuclides in the effluent plume;

2) External irradiation from radionuclides in the effluent plume and deposited on the ground; and

3) Internal exposure through consumption of terrestrial food incorporating radionuclides deposited on the ground with conservative habits.

Inhalation of resuspended deposited activity was not included, as it is not usually significant where there is on-going exposure to the effluent plume itself, these are also presented in Reference [23].

The initial assessment of doses to members of the public is calculated by multiplying DPUR values by the gaseous maximum annual discharges. The DPUR values for air discharge scenario are derived from Appendix D of Reference [6]. The key assumptions in the calculation of DPUR values are: the release is at ground level; the local resident is assumed to be located at a distance of 100 m from the release point; and the food consumed is 100% produced at a distance of 500 m from the release point.

When DPUR values are not available for several radionuclides in Reference [5], surrogate radionuclide can be used as recommended in Reference [5], and the specific surrogate radionuclide is selected in PCER Sub-chapter 7.6.2.2.

7.6.2.2 Input Data

When using the IRA methodology, most of the IRA default data is used. The detailed information is presented as follows:

a) Maximum annual discharges

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The maximum annual discharges derived in the PCER Chapter 6 are presented in T-7B-2 and T-7B-3 for liquid and gaseous discharges. The detailed information of the maximum annual discharges is included in Reference [24] and [25] which provides information on OPEX data selected for the UK HPR1000 and the estimation of maximum annual discharges for the UK HPR1000.

b) Liquid discharges

DPUR values of external irradiation and seafood consumption are used for the radiological assessment of liquid discharges. The parameters used to derive the DPUR for liquid discharges used to assess the exposure of the fisherman family are summarised in T-2.4-6 of PCER Chapter 2 (taken from Appendix E of Reference [6]).

The habits data with 97.5th of the generic public and the marine environment parameters, including the site of the local compartment for heysham which has the highest overall dose of all UK coastal sites and the minimum volumetric exchange rate of 100 m3/s, are used to derive DPUR values, which are considered conservative for dose assessment of the most exposed members of the public due to liquid discharges.

There are several radionuclides for which DPUR values are not available, and surrogate radionuclides are recommended in Table 11 of Reference [5]. If all of these radionuclides use the recommended surrogates in Reference [5], it may unnecessarily overestimate the dose to members of the public. Cs-137 is recommended as the surrogate radionuclide in this chapter, because Cs-137 has similar or higher dose conversion factors and, therefore, provides an appropriate level of conservatism. It is also generally used as the surrogate for “Other beta/gamma” emitters by other permit holders in the UK nuclear industry.

c) Gaseous discharges

DPUR values for terrestrial food consumption, external irradiation and inhalation are used for the radiological assessment of gaseous discharges. The parameters used to derive the DPUR for gaseous discharges are those used to assess the exposure of the resident family. A summarised of parameters is provided in T-2.4-1, T-2.4-2 and T-2.4-3 of PCER Chapter 2 (taken from Appendix D of Reference [6]).

The habits data with 97.5th of the generic public and the conservative meteorological conditions with 50% D distribution of pasquill stability category are used to derive the DPUR values. This is considered to be conservative for the assessment of the dose from gaseous discharges to the most exposed members of the public.

There are several radionuclides for which DPUR values are not available, and surrogate radionuclides are also recommended in Table 11 of Reference [5], except for noble gases where these are not deemed to be suitable. The recommended surrogate in Reference [5] used for noble gases may overestimate the dose to members of the public because the entire gaseous pathways are considered for the surrogate

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radionuclides in Reference [5]. However, for noble gases, only the external irradiation pathway is considered. The radionuclide Kr-88 is chosen as the surrogate for noble gases as this has the highest DPUR value of the noble gases, 5.10E-12 μSv/y per Bq/y, as determined in the Reference [26].

For other radionuclides for which DPUR values are not available, Cs-137 is used as the surrogate radionuclide. The reason for selecting Cs-137 as the surrogate radionuclide was discussed in the liquid discharge section.

7.6.2.3 Results and Discussion

The IRA stage 1 assessment for liquid, gaseous discharges together with the direct dose is summarised in T-7.6-1.

T-7.6-1 Doses to the Most Exposed Members of Public for Stage 1 Assessment

Discharge Route Estimated Dose

(µSv/y) Liquid 27.8

Gaseous 124.6

Direct Dose* 8.0

TOTAL 160.4

* This direct dose is calculated for adult, which is the most exposed person for direct radiation.

The total dose due to liquid discharges, gaseous discharges and direct radiation is found to be 160.4 µSv/y, which is dominated by gaseous discharges and exceeds the 20 µSv/y. Therefore, there is a requirement to conduct a stage 2 assessment.

The detailed information for the dose, from liquid and gaseous discharges, is:

a) The dose to the fisherman family is presented in T-7A-1. The total dose from all radionuclides is 27.8 µSv/y, with C-14 being the most significant contributor (97.7%) to the dose from liquid discharges. This is attributed to the much higher liquid discharge rates for C-14 compared to other radionuclides.

b) The dose to the resident family is presented in T-7A-2. The total dose is 125 µSv/y, with C-14 being the most significant contributor (92.1%) to the dose from gaseous discharges. Similarly, this is attributed to the much higher gaseous discharge rates for C-14 compared to other radionuclides.


7.6.3.1 Methodology

a) Liquid discharges

The methodology of stage 2 radiological assessment for liquid discharges also uses the DPUR values, but a scaling factor derived by refined input data is needed to be

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considered for the dose assessment.

The scaling factor is expressed as the ratio of the two volumetric exchange rates within the stage 1 and stage 2 radiological assessments, which is applied to calculate the dose to members of the public for stage 2 radiological assessments.

b) Gaseous discharges

The methodology of stage 2 radiological assessment for gaseous discharges also uses the DPUR values, but a scaling factor derived by refined input data is needed to be considered for the dose assessment.

According to Figure 2 of Reference [6], two scaling factors for gaseous discharges are identified with accounting for an effective release height. One scaling factor is applied to the inhalation and external radiation exposure pathways while another scaling factor is applied to the food consumption exposure pathways. There are separate scaling factors for these pathways, because the location of exposure of the local resident is assumed to be closer to the release point than the location where their food is sourced.

7.6.3.2 Input Data


The maximum annual discharges for stage 2 assessment are the same as that used in the stage 1 assessment in T-7B-2 and T-7B-3.

b) Liquid discharges

Scaling factors used to estimate the dose to the fisherman family are based on the refined volumetric exchange rate of 130 m3/s. This refined volumetric exchange rate is taken from the minimum volumetric exchange rate at potential sites according to the potential sites identified in PCER Chapter 2. This dataset is used as it is more representative of the dispersion at other potential sites.

The scaling factor is calculated to be 0.77 for liquid discharges, which is the ratio between volumetric exchange rate used in stage 1 (100 m3/s) and volumetric exchange rate used in stage 2 (130 m3/s).

c) Gaseous discharges

The input data for stage 2 assessment of gaseous discharges is also almost the same as that used in stage 1 with the exception that a more refined effective stack height.

The real stack height is dependent upon the local site topography and meteorological conditions, but these site specific parameters are not known in the GDA stage. A real stack height of 70 m, which refers to the design of Hua-long Pressurised Reactor under construction at Fangchenggang nuclear power plant unit 3 (HPR1000 (FCG3)), is considered for the dose assessment. The effective stack height derived by using the

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one third rule, as consideration in Reference [27], is 20 m. This is due to building effects such as re-entrainment, where the building wake is ignored when calculating the activity concentration in air.

According to Figure 2 of Reference [6], the two scaling factors identified are:

1) The scaling factor for food ingestion due to the effective stack height of 20 m is 0.27;

2) The scaling factor for inhalation and external due to the effective stack height of 20 m is 0.04.


The IRA stage 2 assessment for liquid, gaseous discharges together with the direct dose are summarised in T-7.6-2.

T-7.6-2 Doses to the Most Exposed Group for Stage 2 Assessment

Discharge Route Estimated Dose

(µSv/y) Liquid 21.4

Gaseous 18.2

Direct Dose* 8.0

TOTAL 47.6

* This direct dose is calculated for adult, which is the most exposed person for direct radiation.

The total dose due to liquid discharges, gaseous discharges and direct radiation is found to be 47.6 µSv/y, which is dominated by the liquid discharges, and exceeds the 20 µSv/y. Therefore, it is a necessary to conduct a stage 3 assessment.

The detailed information for the doses, from liquid and gaseous discharges, is:

a) The dose to the fisherman family is presented in the T-7A-3. The total dose is 21.4 µSv/y, with C-14 being the most significant contributor (97.7%) to the dose from liquid discharges. This is attributed to the much higher liquid discharge rates for C-14 compared to other radionuclides.

b) The dose to the resident family is presented in the T-7A-4. The total dose is 18.2 µSv/y, with C-14 being the most significant contributor (95.5%) to the dose of gaseous discharges. Similarity, this is attributed to the much higher liquid discharge rates for C-14 compared to other radionuclide.

The dose results calculated by using refined input data are more realistic compared to the stage 1 radiological assessment, but some input data used in this stage is still conservative. A more detailed radiological assessment is needed in the stage 3 assessment.

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7.6.4.1 Methodology

As described in the PCER Sub-chapter 7.6.1.2, PC-CREAM 08 is more appropriate for a realistic radiological assessment to members of the public.

a) Liquid discharge

The radiological assessment due to liquid discharges is divided in two steps:

1) The DORIS module of PC-CREAM 08 is set to predict the activity concentrations in sea water, sediments and marine biotas;

2) The results of the DORIS module are called up in the marine individual dose module of ASSESSOR, used for individual dose calculation. These include the external dose from beaches and fishing equipment, and the internal dose from inhalation of spray and ingestion of seafood.

Different age groups are considered in the radiological assessment: 1 year old infants, 10 year old children, and adults.

It is also noticed that doses to the fetus (including embryo and breast fed infants in the first 3 months after birth) may need to be assessed, particularly if P-32, P-33, Ca-45 and Sr-89 are presented in the discharges, Reference [18]. Only Sr-89 is present in liquid discharges from the UK HPR 1000. Since it forms a small part of the liquid discharges, as shown in T-7B-2, and contributes very little to the total dose for the adult group, as shown in T-7A-3,doses to the fetus are therefore not considered in this assessment.

For other age groups, the dose assessment is conducted with average and high food consumption rates to fisherman family.

b) Gaseous discharge

The radiological assessment due to gaseous discharges is also divided in two steps:

1) The modules of PLUME, GRANIS, FARMLAND, RESUS are used for predicting the transfer of radionuclides through the environment and providing estimates of the activity concentrations in various environmental media following a continuous release. Each of these modules is used in different scenarios in Reference [7], such as:

The PLUME module is set to calculate the activity concentrations in air, deposition rates and external gamma dose rates from radionuclides in the plume (plume gamma) at various distances downwind of the release point;

The GRANIS module is set to model the transfer of radionuclides

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through the soil and takes into account the shielding properties of the soil when estimating doses one metre above the soil surface;

The FARMLAND module is set to predict the transfer of radionuclides into terrestrial foods following deposition onto the ground;

The RESUS module is set to estimate the activity concentrations in air arising from the resuspension of previously deposited radionuclides;

2) The results of these modules are called up in the atmospheric individual module of ASSESSOR used for individual dose calculation. These include the external dose from plume and ground, and the internal dose from inhalation of plume, resuspension radioactive substances and ingestion of terrestrial foods.

Different age groups are considered for the gaseous radiological assessment, similar to those used in the dose assessment for liquid discharges. Similarly, only Sr-89 is present in gaseous discharges from the UK HPR 1000. Since it forms a small part of the gaseous discharges, as shown in T-7B-3, and contributes very little to the total dose for the adult group, as shown in T-7A-2, doses to the fetus are therefore not considered in this assessment.

For other age groups, the dose assessment for resident family is conducted with average and top two food consumption rates.

7.6.4.2 Input Data


The maximum annual discharges for stage 3 assessment are the same as that used in the stage 1 and stage 2 assessments as shown in T-7B-2 and T-7B-3.

b) Liquid discharge

Refined environmental data used for the stage 3 radiological assessments for liquid discharges are:

1) Dispersion parameters

The marine environment parameters used to model the dispersion of liquid discharges are presented T-2.4-5 of PCER Chapter 2. This dataset is used as it is more representative of the dispersion at other potential sites.

2) Habits data

Refined habits data used for stage 3 liquid radiological assessment is provided in T-2.4-8 and T-2.4-9 of PCER Chapter 2.

3) Transfer parameters through the marine environment

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Radionuclides are transferred from seawater to the marine organisms and sediments, the important parameters for these processes are the distribution coefficients for the marine sediment and the concentration factors. Default values in PC-CREAM 08 are used for these two parameters, which are mainly adopted from International Atomic Energy Agency (IAEA) No 247 in Reference [28].

There are no default values for Br, Mo and Rb in PC-CREAM 08. To ensure the dose assessment is conservative enough, the minimum distribution coefficient and the maximum concentration factor from other radionuclides, in liquid maximum annual discharges, are used for these three radionuclides due to the ingestion pathway is mainly contribution of total pathways. These values are presented in T-7B-4.

c) Gaseous discharge

1) Dispersion and deposition parameters

Refined meteorological condition is considered and presented in T-2.4-1 of PCER Chapter 2. The 65% D of meteorological condition represents the condition for coastal location in Figure 11 of Reference [29]. Other important dispersion and deposition parameters are considered as following:

• The surface roughness value used for defining agricultural areas is 0.3m, which is related to calculate the wind speed at the effective stack height and the vertical standard deviation of the plume for the various stability categories.

• The effective stack height of 20 m used for the stage 3 radiological assessments is similar to that used in the stage 2 radiological assessment.

• The deposition rates are mainly depended on the dry deposition velocity and washout coefficient. The default values in PC-CREAM 08 are used and presented in T-7B-5.

2) Transfer parameters through the terrestrial environment

Radionuclides are transferred from soil to the plants, and the most important parameter is equilibrium soil-to-plant concentration ratios (wet weight plant: dry weight soil). The default values in PC-CREAM 08 are used except for the Na, which values come from Table D.10 and Table D.11 of Reference [6]. These values are presented in T-7B-6.

Radionuclides are transferred from plants to animals, and the most important parameters are the equilibrium transfer factors and biological half-life. The default values in PC-CREAM 08 are used except for the Na, which values come from Table D.8 and Table D.9 of Reference [6]. These values are presented in T-7B-7.

3) Habits data

The local resident family is assumed to be located at a distance of 100 m from the

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discharge point, and foodstuffs are produced at a distance of 500 m from the discharge point, which is consistent with stage 1 and stage 2 radiological assessments.

Refined habits data, used for the stage 3 gaseous radiological assessment, are provided in T-2.4-2 and T-2.4-3 of PCER Chapter 2. The main assumptions include the food consumption rates considered at “top two” rates and the consumption of terrestrial food assumed as 100% locally produced.

4) Other input data

For external irradiation due to deposition, the undisturbed wet soil is considered. The external dose to a local resident is mainly from surface deposition. The activity concentration in surface ground of undisturbed wet soil is higher than that of well mixed soil.

For resuspension inhalation dose, the resuspension concentrations of radionuclides in air mainly depend on the concentration on the ground and resuspension factors which are calculated in PC-CREAM 08.


The following two scenarios are considered respectively:

a) The assessment of the exposure from each discharge route at the high/top two consumption rates and direct exposure for the age groups that have the highest predicted exposure.

b) The assessment of the exposure from each discharge route at average consumption rates and direct exposure for the age groups.

The results of stage 3 dose assessment from liquid discharges, gaseous discharges together with the direct radiation are presented in T-7.6-3 and T-7.6-4.

T-7.6-3 Summary Doses of High/Top Two Consumption Rates and Direct Exposure

Discharge Route Adult Annual

Dose μSv/y Child Annual

Dose μSv/y Infant Annual

Dose μSv/y

Liquid discharges1

11.2 4.3 0.9

Gaseous discharges2

9.8 9.6 15.1

Direct radiation

8.0 4.1 2.8

Total 29.0 18.0 18.8 1 Doses are calculated with high consumption rates of marine foodstuffs, and data source from T-7A-5 to T-7A-7; 2 Doses are calculated with “top two” consumption rates of terrestrial foodstuffs, and data source

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from T-7A-11 to T-7A-13.

T-7.6-4 Summary Doses of Average Consumption Rate and Direct Exposure

Discharge route Adult annual Dose μSv/y

Child Annual Dose μSv/y

Infant Annual Dose μSv/y

Liquid discharges1 2.2 3.0 0.6

Gaseous discharges2 6.9 6.4 7.7

Direct radiation 8.0 4.1 2.8

Total 17.1 13.5 11.1

1 Doses are calculated with average consumption rates of marine foodstuff, and data source from T-7A-8 to T-7A-10;

2 Doses are calculated with average consumption rates of terrestrial foodstuffs, and data source from T-7A-14 to T-7A-16.

The dose due to gaseous discharges is higher than that due to liquid discharges and direct radiation. The highest total predicted dose is found to be 29.0 µSv/y.

The detailed information of the results is presented here:

a) Liquid discharges

The detailed dose to an adult, child and infant of a fisherman family with high and average marine foodstuffs are presented in T-7A-5 to T-7A-10.

The doses to an adult, child and infant of a fisherman family with high consumption rates from liquid discharges are 11.2 µSv/y, 4.3 µSv/y and 0.9 µSv/y, respectively. The dose to an adult is higher than that to a child and infant.

By comparing the dose results for each pathway, it is found that the dominant pathway is ingestion of seafood which contributes 99.1%, 99.9% and 98.8% of the total dose for the adult, child and infant respectively. And C-14 has the most significant contribution to the total dose, estimated at 98.8%, 99.4% and 98.4% to the total dose for the adult, child and infant, respectively.

The doses to an adult, child and infant of a fisherman family with an average consumption rate from liquid discharges are 2.2 µSv/y, 3.0 µSv/y and 0.6 µSv/y, respectively.

The dose is also dominated by ingestion of seafood which contributes 95.8%, 98.2% and 98.4% of the total dose for the adult, child and infant, respectively. And C-14 also has the most significant contribution to the total dose, which contributes 96.8%, 99.5% and 97.9% of the total dose for the adult, child and infant, respectively.

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b) Gaseous discharges

The detailed doses to adult, child and infant of resident family with “top two” and average terrestrial food consumption rates are presented in T-7A-11 to T-7A-16.

The doses to an adult, child and infant of a resident family with “top two” consumption rates from gaseous discharges are 9.8 µSv/y, 9.6 µSv/y and 15.1 µSv/y, respectively. The dose to an infant is higher than that to a child and adult.

By comparing the dose results from each pathway, it is found that the dominant pathway is ingestion of terrestrial foods which contributes 84.0%, 84.9% and 92.3% of the total dose for the adult, child and infant, respectively. And C-14 has the most significant contribution to the total dose, estimated at 96.0%, 96.3% and 95.7% of the total dose for adult, child and infant, respectively.

The doses to an adult, child and infant of a resident family with average consumption rates for gaseous discharges are 6.9 µSv/y, 6.4 µSv/y and 7.7 µSv/y, respectively.

The dose is also dominated by ingestion of terrestrial foods which contribute to 77.4%, 77.2% and 84.9% to the total dose for the adult, child and infant, respectively. And C-14 also has the most significant contribution to the total dose, estimated at 95.7%, 96.1% and 95.6% of the total dose for the adult, child and infant, respectively.

7.7 Annual Dose to the Representative Person The definition of the representative person is “an individual receiving a dose that is representative of the more highly exposed individuals in the population” in Reference [14]. The ICRP and the PHE have stated that this term is the equivalent of and replacement for the average member of the critical group.

ICRP Publication 103 in Reference [14] states that “the representative person may be hypothetical, but it is important that the habits…used to characterise the representative person are typical habits of a small number of individuals representative of those most highly exposed and not the extreme habits of a single member of the population. Consideration may be given to some extreme or unusual habits, but they should not dictate the characteristics of the representative person considered”.

7.7.1 Methodology

The radiological assessment for the representative person is based on the results of the stage 3 radiological assessment and the direct radiation from sources on site. The candidates of the representative person are determined by the methodology presented in the F-7.7-1 and described here:

a) Case A resident family: The most exposed individual of resident to gaseous discharges may be identified, and the most exposed person to gaseous discharges may also be exposed to a lesser degree to liquid discharges (only the pathway of

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consuming seafood at average rate is considered) and direct radiation.

b) Case B fisherman family: The most exposed individual of fisherman to liquid discharges may be identified, and the most exposed person to liquid discharges may also be exposed to a lesser degree to gaseous discharges (only the pathway of consuming terrestrial food at average rate is considered) and direct radiation.

c) Case C: The most exposed individual to direct radiation may be identified, and the most exposed person to direct radiation may also be exposed to a lesser degree to gaseous discharges (only the pathway of consuming terrestrial food at average rate is considered) and liquid discharges (only the pathway of consuming seafood at average rate is considered).

The candidate with the highest dose is the likely representative person. In the GDA stage, the dose from direct radiation is calculated for one conservative exposure scenario as described in Sub-chapter 7.5. It is obvious that the dose results of case C is lower than that of case A and case B, therefore no longer considered in the identification of the representative person.

F-7.7-1 Methodology for Determine Representative Person

7.7.2 Input Data

The input data for the representative radiological assessment of liquid discharge is the same as that used in the stage 3 assessment, both for liquid and gaseous discharges.


The dose results to the two groups of candidates of the representative person are presented inT-7.7-1 and T-7.7-2.

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T-7.7-1 Dose to Fisherman Family

Age group

Liquid discharges (μSv/y)

Gaseous discharges

(μSv/y)

Direct dose(μSv/y)

Total

Adult1 11.2 5.3 8.0 24.5 Child2 4.3 4.9 4.1 13.3 Infant3 0.9 6.5 2.8 10.2

1 Data source from T-7A-17; 2 Data source from T-7A-18; 3.Data source from T-7A-19.

T-7.7-2 Dose to Resident Family

Age group

Liquid discharges (μSv/y)

Gaseous discharges

(μSv/y)

Direct dose(μSv/y)

Total

Adult1 2.2 9.8 8.0 20.0 Child2 3.0 9.6 4.1 16.7 Infant3 0.6 15.1 2.8 18.5

1 Data source from T-7A-20; 2 Data source from T-7A-21; 3.Data source from T-7A-22.

The dose results from liquid and gaseous discharges are presented in T-7A-17 to T-7A-22, and the direct radiation results are presented in the T-7.5-1. It can be seen that the maximum total dose (24.5 μSv/y) is received by an adult from the fisherman family. Therefore the adult of fisherman family is considered as the representative person.

According to the dose results, the significant pathways differ between receptors and age groups:

a) For the fisherman family, the dose to the adult is dominated by exposure to liquid discharges, whilst the doses to the child and infant are dominated by exposure to gaseous discharges.

When comparing the dose results from each age group, the dominant pathway is ingestion of seafood for the adult which contributes 67.2% of the total dose, and ingestion of terrestrial foodstuffs for the child and infant at 53.5% and 88.3% of the total dose, respectively.

C-14 has the most significant contribution to the ingestion dose, and it contributes 98.5%, 98.4% and 96.5% of the total dose to the adult, child and infant, respectively.

b) For the resident family, the doses to the adult, child and infant are dominated by

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exposure to gaseous discharges.

When comparing the dose results from each pathway, it is found that the dominant pathway is ingestion of terrestrial foodstuffs which contributes 68.7%, 64.7% and 88.8% of total dose for the adult, child and infant, respectively.

C-14 has the most significant contribution to the ingestion dose, and it contributes 96.7%, 97.1% and 95.9% of the total dose to the adult, child and infant, respectively.

7.8 Potential Dose due to the Short-term Discharge During normal operations, elevated short-term releases of radionuclides may occur as a result of planned maintenance operations or particular features of operations of plants, which may lead to a higher annual dose to the members of the public than that assessed for a uniform release rate over the year.

7.8.1 Methodology

a) Discharge scenario

The assessment of the potential dose due to short-term discharges only considers gaseous discharges. Liquid discharges from the UK HPR1000 design are made on a batch basis. The design prevents spikes of short-term activity being released due to the effluent being held in storage tanks which are sampled prior to final discharge to the environment. If activity values exceed the prescribed limits, the effluent can be returned to the effluent waste management system for further treatment until levels are acceptable for release into the environment. For this reason, no short-term dose assessment of the liquid effluent discharged to the environment will be undertaken. Therefore the doses from gaseous discharges are considered for the short-term radiological assessment.

b) Gaseous dispersion

The gaseous discharges are estimated in a manner that consistent with the methodologies set out in Reference [30] and [31]. The gaseous dispersion model ADMS 5 is used to calculate the activity concentrations in air per unit discharge, the deposition rate per unit discharge and the plume gamma doses for the radionuclides from the short-term discharges.

Location factors are not used in the assessment since individuals are assumed to stay outside during the entire duration of exposure to the plume.

c) Dose calculation

The radiological assessment of short-term discharges considers the following exposure pathways:

1) Inhalation and external radiation from plume (gamma external radiation from

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plume is calculated by the ADMS 5);

2) Ground external radiation and ingestion of terrestrial foodstuffs for a year following the release.

The doses are calculated using the approach outlined in Appendix I of Reference [31]:

1) Ingestion dose

, , = ∑ ∑ , × , , × , × × (7.8-1)

Where:

DoseT,n,r: Individual effective dose (Sv) to the chosen age group received from the food consumption, over time (T), of all foods (F), for radionuclide (n) and release (r);

Depn,r: Total deposition (Bq/m2) from the passage of the plume;

IntActt,f,n: Integrated activity concentration per unit deposit (Bq∙y∙kg per Bq/m2) in food f over time t;

IngRatet,f: Ingestion rate (kg/y) of food f over time t for the chosen age group;

DPUIn: Dose per unit intake (Sv/Bq) for the radionuclide and chosen age group;

LocPcntf: The percentage of food f that is locally produced.

2) Inhalation dose ℎ = × , × ℎ × ( × ) + (7.8-2) DoseInhn: Inhalation dose for radionuclide n (Sv);

Actn: Activity concentration in air during the passage of the plume (Bq/m3);

Hing,n: Dose coefficient to calculate committed effective dose for radionuclide n (Sv/Bq);

Inh: Breathing rate (m3/h);

Tid,od: Indoor and outdoor exposure time (h);

DRFn: Dose reduction factor for radionuclide n.

Actn is calculated from: = × (7.8-3) Where:

Actn: Activity concentration in air of radionuclide n during the passage of the

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plume (Bq/m3);

Rn: Release rate of radionuclide n (Bq/s);

Cn: Activity concentration in air of radionuclide n per unit release rate (Bq/m3 per Bq/s release).

3) Ground dose = × × × ( × ) + ( × ) (7.8-4)

Where:

DoseDep: Effective dose (Sv) from deposited discharges for radionuclides n over time t;

n: Radioactive decay constant (1/h) for radionuclide n;

t: Exposure time (h);

GrActn: Activity concentration in the ground resulting from the deposition of the plume (Bq/m2);

DCext: External dose coefficient (Sv/h per Bq/m2);

LFid,od: Indoors (id) and outdoors (od) factors;

Fid,od: Fraction of time spent in location.

GrActn is calculated from: = × × , (7.8-5) Where:

GrActn: Activity concentration on the ground resulting from the deposition of the plume (Bq/m2);

Rn: Release rate of radionuclide n (Bq/s);

T: Release duration (s);

Cdep,n: Deposition rate of the radionuclide n per release rate (Bq/(m2∙s) per Bq/s). 7.8.2 Input Data

a) Short-term discharges

Operational (i.e. routine, planned or reasonably foreseeable) short-term discharges are higher than normal releases and can be attributed to a number of causes, including variations in site production. For the UK HPR1000, the monthly discharges presented

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as short-term discharges are shown in T-7B-8.

Not all of the radionuclides in the short-term discharges are important to the dose members of the public. The significant radionuclides are identified according to the dose results from continuous discharges of gases in T-7B-9. The radionuclides which have higher dose contribution to the total dose are selected in the short–term radiological assessment. These radionuclides are listed in T-7B-10. And it is conservatively assumed that these radionuclides are released uniformly over a short period of 24 hours.

b) Dispersion and deposition parameters

The effective stack height for short-term discharges is set at 20 m, similar to that assumed in the stage 2 and stage 3 dose assessments.

The default values of stack diameter (1m) and temperature of gases (15°C) in ADMS 5 are used, and the discharge velocity is set as 10 m/s. Discharge velocity assumed in this assessment is lower than the 12 m/s used for the HPR1000 (FCG3).

The meteorological conditions are presented in T-2.4-1 of PCER Chapter 2, which is the realistic cautious condition recommended in Reference [31]. The Pasquill stability categories are associated with the surface heat fluxes which are used in the ADMS model. Figure 2 of NRPB R91, Reference [29], shows the relationship between Pasquill stability categories and the surface heat fluxes, and the surface heat flux estimated at 0 W/m2 corresponds to category D.

The wind is assumed to blow directly toward members of the public with a degree of lateral spread. According to the approach in Reference [29], the lateral spread of the wind direction for the 24 hour release can be presented as follows:

The dispersion of the plume in the horizontal plane is the result of turbulence processes together with fluctuations in wind direction. The standard deviation σ in the horizontal plane is presented as: σ = σ + σ (7.8-6) Where: σ : Turbulent diffusion component (m); σ : Component due to fluctuations in wind direction (m). The σ for the downwind distance of 100m and under the Pasquill category D, which is identified in Figure 10 of Reference [29], is determined as 8 m.

The σ is calculated using the following equation: σ = 0.065 (7.8-7)

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Where: u: Wind speed, m/s; T: Release duration in hour, h;

: Downwind distance, m.

The σ for the downwind distance of 100 m calculated from Equation (7.8-7) is 48.6 m.

The value of σ at 100m is 49.3m. The lateral spread is 27.6 degree, which is calculated from: = 2 ( . ) (7.8-8) For the deposition process, the deposition rates are mainly dependent on the dry deposition velocity and washout coefficient. For radionuclides from gaseous discharges (with the exception of noble gases, iodine, H-3 and C-14), the dry deposition velocities are calculated from the model within ADMS 5 on the basis of the default value for particle size and density in ADMS 5. Similarly, for radionuclides from gaseous discharges (with the exception of noble gases, H-3 and C-14), the washout coefficients are calculated from Equation (7.8-9) with rainfall rates of 0.1 mm/h. Washout coefficients of radionuclides are presented in T-7B-11.

= (7.8-9) Where: Λ: Washout coefficient (1/s); A: Default value in ADMS 5, the value is 0.0001;

B: Default value in ADMS 5, 0.64.

c) Habits data

It is also assumed that members of the public are located at 100 m from the discharge point and all food production occurs 500 m from the discharge point. For the purpose of a conservative dose assessment, all of the ingested foodstuffs are produced locally.

The habits data used for the short-term dose assessment is provided in T-2.4-2 and T-2.4-3 of PCER Chapter 2, and the terrestrial foodstuffs are assumed to be consumed at the “top two” rates. The breathing rates are different from those used in the assessment of continuous discharges, because the breathing rates in the short-term assessment are presented for a period of a few hours compared to the average level over the year. The adult breathing rate averaged over a working day for heavy work is selected for the short-term assessment.

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d) Integrated activity concentration per unit deposit

1) Radionuclides except for C-14 and H-3

The integrated activity concentrations in foods for most radionuclides (except for the H-3 and C-14) are calculated using the values of integrated activity concentration per unit deposit from Table A3 of Reference [32]. However, food concentration factors for Ag-110m, I-133, Co-58, Mn-54, I-135 and Cs-134 are not available. Conservatively, I-129 is selected as surrogate for I-133 and I-135, and Cs-137 surrogate for Cs-134. The surrogate radionuclides with longer half-life have similar transfer coefficients in the environment media with these radionuclides.

Conservatively, the maximum food concentration factor for each foodstuff is selected for Ag-110m, Co-58 and Mn-54. The concentration factors for radionuclides of interest except for H-3 and C-14 are presented in T-7B-12.

According to the Equation (7.8-1), the activity concentration in foodstuffs for most radionuclides can be calculated using the integrated activity concentration per unit deposit. The transfer of H-3 and C-14 between the atmosphere and the terrestrial environment is more complex than for other radionuclides, since hydrogen and carbon are fundamental to biological systems.

2) C-14 and H-3

The specific methodology in Appendix D of Reference [6] is used for C-14 and H-3 to calculate the activity concentrations in foodstuffs. It is assumed that all foodstuffs come into rapid equilibrium with atmospheric H-3 and C-14. The specific activity for each element in the food is equal to the atmospheric concentration. The concentration in food is therefore calculated using the following equation:

Cfood =Cplume × F (7.8-9) Where:

Cfood: Concentration in food (Bq/kg);

Cplume: Concentration in plume (Bq/m3);

F: Conversion factor (Bq/kg per Bq/m3) relating the airborne concentration of the radionuclide in the plume at the point of interest to the concentration of the radionuclide in foodstuffs produced at that point.

The conversion factors are given in T-7B-13 refer to IRA methodology Part 2 of Reference [6]. The conversion factor is used to calculate the activity in foodstuffs due from continuous release where the foodstuffs are in equilibrium with the activity in air. Therefore, to take account for the short transient duration of the release, a time factor is applied to modify the concentration factor. The time factor is the release duration divided by the number of hours per year, i.e. 24/8760 = 2.74E-03.

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The doses from short-term discharges are calculated for the adult, child and infant groups using the above methodology and input data. The results are presented in T-7A-23, T-7A-24 and T-7A-25, respectively.

The results show total doses of 8.7 µSv, 9.0 µSv and 14.6 µSv to the adult, child and infant groups, respectively. The dose to the infant group is higher than that to the adult and child groups.

The detailed information is presented as follows:

a) The total doses are dominated by the ingestion of terrestrial foods which contributes 7.8 µSv (88.8%), 8.1 µSv (90.6%) and 13.7 µSv (94.2%) to the dose to the adult, child and infant groups, respectively.

b) The total doses are dominated by C-14 which contributes 8.4 µSv (96.2%), 8.6 µSv (96.3%) and 14.1 µSv (96.3%) to the dose to the adult, child and infant groups, respectively.

As mentioned in Reference [30] ‘the dose assessed for operational short-term releases at notification levels or limits should be compared with the annual source constraint (maximum of 0.3 mSv) and the annual dose limit (1 mSv), taking into account other relevant contributions. Other contributions will include the dose from any continuous releases for the remainder of the 12-month period’. The summations of short-term dose and continuous dose for different age groups are presented in T-7.8-1. The maximum dose is 37.7 µSv/y for the adult of a resident family, which is considerably below the dose constraint.

T-7.8-1 Summary Dose of Most Exposed Members of the Public and Short-term Discharges

Discharge RouteAdult Annual

Dose μSv/y Child Annual Dose

μSv/y Infant Annual

Dose μSv/y

Short-term discharges

8.7 8.9 14.6

Liquid discharges

11.2 4.3 0.9

Gaseous discharges

9.8 9.6 15.1

Direct radiation 8.0 4.1 2.8

Total 37.7 26.9 33.4

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7.9 Comparison of the Calculated Doses with Relevant Dose Constraints

The summary of radiological protection criteria for members of the public is presented in T-7.9-1 referring to the Reference [18]. It includes the dose limits, dose constraints, threshold for optimisation and potentially ‘of no regulatory concern’.

• Dose limits and dose constraints

Dose limits apply when retrospective assessments of doses from past discharges are made. For prospective assessments the dose criteria are the dose constraints. However a complete prospective assessment may need to consider additional elements including an assessment of doses from historical discharges and doses from other sites nearby. The total outcome can then be compared with the dose limit.

The generic site of the UK HPR1000 is assumed that no historical discharges or other sites nearby exist. Therefore, the prospective assessment is then conducted, and the results can be compared to the dose constraints.

• Threshold for optimisation and potentially ‘of no regulatory concern’

The threshold for optimisation is used to assist constrained optimisation of the planned operation of a single source. The threshold for optimisation has been set at the basic safety objective of 20 μSv/y for any person off the site receiving doses from sources of ionising radiation originating on the site. This is a level below which the risk is negligible in comparison with other risks people are exposed to in their daily lives.

IAEA has suggested dose criteria for sources or practices below which doses and associated practices may be exempted from regulatory control. One of the criteria is that the dose should be less than 10 μSv/y per practice. The statutory guidance to the EA states that where the prospective dose to the most exposed group of members of the public from discharges from a site at its current maximum annual discharges is below 10 μSv/y, the EA should not seek to reduce further the maximum annual discharges that are in place, provided that the holder of the permit or authorisation applies and continues to apply BAT.

The publication of statutory guidance to the EA could allow the adoption of 10 μSv/y as the threshold which applies in England and Wales. This would lead to 10 μSv/y being adopted in England and Wales and 20 μSv/y in Scotland and Northern Ireland as the threshold below which the dose assessment process does not require further refinement. 10 μSv/y and 20 μSv/y can be considered to be broadly equivalent for the purposes of the principle in Reference[18] and 20 μSv/y has been retained to ensure consistency across the UK in Reference[18].

The UK HPR1000 adopts an assumption of a single unit design as described in the GDA scope of Reference [20]. Therefore, the applicable dose constraint and threshold

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for optimisation are 0.3 mSv/y and 20 μSv/y, respectively.

The dose criteria including their application to prospective dose assessments are summarised in T-7.9-2.

The annual dose to the representative person for the UK HPR1000 was calculated in Sub-chapter 7.7. The total dose to the representative person is 24.5 μSv/y, which is just over the threshold for optimisation of 20 μSv/y, but significantly below the single source constraint of 0.3 mSv/y.

UK HPR1000 GDA Pre-Construction Environmental Report Chapter 7 Radiological Assessment


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T-7.9-1 Summary of Radiological Protection Criteria for Public Exposure

Criteria Quantity

Doses to be Included in Assessments Against Criteria

Source of Radiation for Site Considered Other Sources of Radiation (Excluding

Medical and Natural Historical Discharges

Future Discharges

Future Direct Radiation

Historical Discharges

Future Discharges


Dose limit (effective dose)

1 mSv/y √ √ √ √ √ √

Dose limit for the skin (equivalent dose)

50 mSv/y averaged over any area of 1 cm2

√ √ √ √

Dose limit for lens of the eye (equivalent

dose) 15 mSv/y √ √ √ √

Site constraint (effective dose)

0.5 mSv/y √

Source constraint (effective dose)

0.3 mSv/y (max) √ √

Investigation level for Generalised Derived

Constraint (GDC)

30% of GDC or 0.1 mSv/y

√

Threshold of optimisation (effective

dose) 20 μSv/y √ √



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Criteria Quantity

Doses to be Included in Assessments Against Criteria

Source of Radiation for Site Considered Other Sources of Radiation (Excluding

Medical and Natural Historical Discharges

Future Discharges


Historical Discharges

Future Discharges


Potentially ‘of no regulatory concern’

(effective dose) ≤10 μSv/y √ √

T-7.9-2 Dose Criteria and Their Application in Prospective Dose Assessments

Effective dose criteria

Dose quantity

Application to prospective dose assessments

Purpose of assessment Applicable to GDA

Dose limit 1 mSv/y

One or more future discharges is planned and the radioactivity will combine with the residues of past discharges from one or more sources and direct radiation.

To show that total doses from one or more past and present and future sources will not exceed dose limit.

No This criterion includes the residues of past discharges from one or more sources and direct radiation.

Site constraint 0.5 mSv/y

Future discharges from the planned operation of more than one source where the sources are on sites that are adjacent. Direct radiation is not included.

To assist optimisation of the planned operation of sources where the sources are under separate control but located close together.

No The criterion includes sources on the adjacent site.



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Dose quantity



Source constraint 0.3 mSv/y

Upper constraint on future discharges and direct radiation from the planned operation of a single source. Dose assessment should be refined until it is considered to be sufficiently realistic or falls below 0.02 mSv/y

To assist constrained optimisation of the planned operation of a single source. Provide a realistic assessment of doses to act as an input to the optimisation process.

Yes This criterion considers a single source as assessed in the GDA process.

Between threshold of optimisation

and source constraint

20 μSv/y to 0.3 mSv/y

Future discharges and direct radiation from the planned operation of a single source. Dose assessment should be refined until it is considered to be sufficiently realistic or the assessed dose falls below 0.02 mSv/y

To assist constrained optimisation of the planned operation of a single source. Provide a realistic assessment of doses to act as an input to the optimisation process.


Level of dose below which the dose assessment

requires no further work.

20 μSv/y

Future discharges and direct radiation from the planned operation of a single source. If doses are below this threshold, the dose assessment need not be refined further.

To assist constrained optimisation of the planned operation of a single source. Doses sufficiently low to be used as an input to the optimisation process without further refinement.




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Dose quantity



Level of dose below which the dose assessment

requires no further work.

10 μSv

Documents

UK Protective Marking: UK HPR1000...the BSSD (2013) was revised in Reference [13] to reflect the requirements in the 2007 recommendations of the ICRP in Reference [14]. The EPR16,