Nuclear Safety History

7/27/2019 Nuclear Safety History

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Nuclear Safety Objectives

and History

A.A. 2013-2014

Nuclear safety objectives (1)

Ensure that both the siting of the plant and the plantconditions comply with adeguate principles: healthprinciples, safety principles, radioprotection principles.

The consequences on the health of the population andworkers are less severe than established limits.

The effects must be the lowest reasonably achievable(ALARA As Low As Reasonably Achievable) in all

operational conditions and in case of accident.

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Nuclear safety objectives (2)

GENERAL OBJECTIVE

Effective defences against radiological hazard are established andmaintained in order to protect individuals, society and environmentfrom harm

RADIATION PROTECTION OBJECTIVE In all operational states the radiation exposure within the plant

and outside (planned releases of radioactive materials) must bekept below prescribed limits and as low as reasonably achievable

Radiological consequences of any accident must be mitigated

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Nuclear safety objectives(3)

TECHNICAL SAFETY OBJECTIVE

All reasonably practicable measures must be taken in order toprevent accidents in nuclear plants

In case of accidents, their consequences must be mitigated

For all possible accidents taken into account in the plant design,there must be a high level of confidence that any radiologicalconsequences is minor and below prescribed limits.

The likelyhood of accidents with serious radiologicalconsequences must be extremely low

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The early years Fermis Pile

Gravity driven shutdown rods:operated by cutting a retainingrope with an axe(SCRAM = Safety Control RodAxe Man).A secondary shutdown system:buckets containing cadmiumsulphate solution, could beemptied onto the pile should theneed arise.Emergency cooling systemmissing (decay heat practicallyabsent)No containment system

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The early years

Reactors built for both military and civil purposes withoutcontainment system, located in remote sites. Not all the necessary precautions were taken

A war was in progress or just finished

The knowledge of radiation protection was not yet advanced.

Later on these first reactors were either shutdown ormodified by introducing: Closed cycle cooling of the reactor

Pressure-resistant containment

Reliable disposal of radioactive liquids (no longer stocked insimple underground metallic tanks)

The storage of spent fuel in leaking pools of water wasabandoned


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1950-1960 Since 1960s, in the West, power reactors were located in a leak-

proof and pressure-resistant vessel

Since 1950s, the Advisory Committee on Reactor Safety (ACRS)

of Atomic Energy Commission (AEC) fixed, for a non-containedreactor, an exclusion zone with a minimum radius:

3000 MWth reactor: R~ 30 km (the distance evacuated after theChernobyl accident).

An exclusion zone of this magnitude poses excessive problemsto siting.

In 1957 accident at Windscale (Cumberland, England)

In 1961 accident at the SL-1 plant (Idaho, USA).

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Windscale accident Air-cooled, graphite-moderated plutonium production reactor, without

containment While annealing the graphite moderator (slow raise of graphite

temperature to release the energy stored in the graphite as fast neutronsknocked carbon atoms out of the lattice;Wigner effect), a fire started inone of the fuel channels and quickly spread to 150 other channels.

4 days necessary to extinguish the fire by flooding the reactor with water. Cooling air was directly released to the atmosphere. Radioactive materials dispersed and deposited over England, Wales and

parts of the Northern Europe. Part of the iodine was attached to particular matter (20000-50000 Ci) and

the stack filter retained between 800 to 1000 Ci of cesium. It was estimated that 25-43% of the iodine and 17-18% of the cesium

must have escaped from the core. Iodine is a particularly dangerous element because it concentrates as it

proceeds through the biological chain and finally is stored in the body.

It was estimate that, as a result of the accident, the maximum individualthyroid dose to a child was 160 mSv


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Stationary Low-power plant No.1 (SL-1) 3MW natural circulation, highly enriched (93% U-235) boiling water

reactor at a remote military installation. Core: elements of uranium-aluminum alloy in aluminium-nickel cladding. During the recoupling of the shutdown and control rods to their drive

shafts after maintenance, the manual withdraw of the central control rodled to a severe power excursion

The steam explosion, some metal vaporisation and damage of 20% ofthe core.

Two operators killed immediately; a third died within one hour. Between 5% and 15% of the total fission product inventory escaped

from the reactor vessel Less than 0.5% of the I-131 and 0.01% of the non-volatile fission

products (FP) found in the desert. Reactor building not designed specifically to contain radionuclides, FP release mitigated because the energy was released in a short time

period, the system was not pressurised and the decay heat was not toohigh to cause the core to remain molten after the accident. Therefore there was little driving force for the radionuclides release.


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1960s-1970s (1)

These accidents strongly influenced subsequent thinking onconsequences to the public.

In the West, power reactors were located in a leak-proof andpressure resistant vessel.

The whole refrigeration primary circuit was located completely insidethe containment, so that all the escaped fluid would be confined inthe containment envelope;

Design pressure of the containment for water reactors: completerelease of the primary water and part of the secondary water wereassumed.

In East Europe, these criteria were applied to a lesser degree: onlythe vessel was located within the containment; not very stringent

leak-proof characteristics of the containment. In the West, the opinions on the accident assumptions were divided. The Advisory Committee on Reactor Safety (ACRS) proposed the

use of maximum credible accidents.

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1960s-1970s (2) A number of severe accidents were postulated (although they were

deemed very unlikely).

Plant designer developed various approaches to avoid the effects ofthese postulated severe accidents:

development of engineered safety systems to prevent core melt, provision of a containment vessel to retain the radioactive products if they were

released.

Considering the maximum credible accident was extremely usefulin limiting or preventing the occurrence of severe accidents.

It was realised that the engineered safety devices might not workexactly in accordance with their design, and that failures of suchdevices could lead to serious consequences.

The word credible was added to imply that, while more severescenarios could be envisaged, they were considered so unlikely asto be deemed incredible.


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1960s-1970s (3)

A substantial number of maximum credible accidents (Design BasisAccidents - DBAs) have been defined by the Atomic Energy

Commission to establish the licensing basis for designrequirements for nuclear safety systems. The most severe DBAs is the sudden, double-ended, guillotine

break of the largest coolant pipe in the primary system of the reactor( DBA Loss Of Coolant Accident).

The blowdown of the high-pressure reactor primary coolant and theconsequent increase in containment pressure are used to establish:

the design pressure of the containment structure the requirements upon which the emergency core cooling system

(ECCS) and other engineered safety features (such as containment

sprays and cooling fans) of the plant were designed. Then double-ended pipe break LOCA became an incident that by

definition would not result in melting of the reactor core.

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1960s-1970s (4) Conservative assumptions concerning malfunctions in the safety

systems, such as a single failure consisting in the failure,simultaneous with the initiating event, of one active component ofone of the safety systems devoted to emergency safety functionsduring the accident (water injection system, reactor shutdownsystem and so on).

On one side more cautious experts supported the need for keepingthese conservative assumptions.

On the other side more optimistic people (members ofmanufacturing industries and electric utilities) maintained that theabove mentioned accident assumptions entailed a waste ofresources.

Many phenomena were still unknown: Auto-catalytic reaction of Zircaloy fuel cladding with water The swelling of the Zircaloy cladding before rupturing, preventing

the flow of cooling water Only in the 1970s experts demonstrated the possibility that the

break of a pipe could damage other nearby pipes or plantcomponents (pipe whip effect).


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1960s-1970s (5)

Control bodies stipulated that the inherent safety systems andthe resistance of plants to natural phenomena or man-made

events had to be improved. These requests of improvement (backfitting) extended the

construction times of the plants and increased their costs. The increase in costs as a consequence of the continuous

requests for plant improvements, was strongly in contrast withthe initial industrial expectations (i.e. cheapness).

This continuous process of improvement produced very safe butalso very costly and rather complicated plants, which weresubject to a series of safety features additions to a substantiallyunchanged basic design.

Up to TMI accident, not all nuclear technical experts believed thatthe adopted accident assumptions were reasonable ( some ofthem believed they were excessive).

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1960s-1970s (6) Different approaches to siting in the USA and in Western Europe. In the USA the plant siting criteria, as far as demographic aspects were

concerned, were substantially decoupled from the design features of the plant. The AEC defined a source term for the DBA-LOCA to help establish criteria for

the licensing of plant sites that considered the kinds and magnitudes of publichealth hazards for the population distribution about those sites. Thus the sourceterms for DBAs were intentionally defined to be arbitrarily (and unrealistically)

large. Although the DBA-LOCA would not result in a core melt, the source termswere defined in terms of quasi-core melt conditions. TID-14844 source term: 15%of the fission product activity was considered to be

released to the containment vessel, containing 100% of the noble gases, 50% ofthe iodine in the gaseous form and 1% of the solids in the fission productinventory.

Subsequently, one-half of the released iodine in the containment structure andall of the solid fission products were assumed to fall out, to be adsorbed ontothe internal structures of the building, or to adhere to internal reactorcomponents and, therefore, to be unavailable for release to the externalenvironment.

Reductions in the airborne iodine in accordance with the projected effectiveness

of the containment spray systems could be considered as time passed followingaccidental releases during the hypothetical accident sequence.


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1960s-1970s (7)

In the late 1960s, the TID-14844 source term was incorporated in theAEC safety guide 3 and 4, which specify the assumptions to be used in

estimating off-site consequences of the maximum credible accident. Other US site criteria were the following: existence of an exclusion zone around the plant (radius 800-1000 m),

where no dwellings or productive settlements exist and the access isunder complete control of the plant management;

existence of a low population zone around the plant (radius of roughly 5km), which could be quickly evacuated in case of accident in the plant;

radioactive product release from the core to the containmentconventionally established as a function of the plant power only.

In this approach, the decision about the adequacy of a proposed sitecould be taken only on the basis of the plant power level and, possibly,

on the specific characteristics of its fission product removal systems.

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1960s-1970s (8) Europe: the site selection criteria usually consider the site-plant

complex. If a plant with the usual safety systems could not be located on a

specific site because accident doses exceeded the reference limits,it was possible to make the plant acceptable for the same site by theimprovement of the systems for fuel integrity protection in case of

accidents. The need to take into account the specific plant features for the

evaluation of the acceptability of the site arises from the muchhigher population density.

The dose limits varied somewhat between various countries, butthey were of the order of 5 mSv (500 mrem, effective dose) to thecritical group of the population outside the exclusion zone for everycredible accident (Design Basis Accidents).

In order to evaluate the consequences of these accidents, noconventional figure for the releases is used, but conservative and

more realistic assumption were adopted. Iodine released in the containment assumed equal to the inventory

in the fuel-clad interface (i.e. 1-5% of the total core inventory)


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1970s-1980s (1) Up to the TMI accident, three other facts influenced nuclear safety

technology: defence against non-natural external events (initially accidental fall of

an aircraft, then sabotage performed by the use of an aircraft or by

explosives of various kind) the preparation of the Rasmussen report (WASH 1400) the introduction of the Quality Assurance (QA) in the design,

construction and operation of plants. Plant protection against the various effects of the impact by a fighter

aircraft (weighing about 20t) was adopted at least in Germany, Belgium,Switzerland and Italy.

No country adopted a protection against the impact of a wide-bodiedairliner of the Jumbo Jet type (weighing about 350 t), which would befar more onerous (possibly requiring the underground location ofplants).

It was calculated that the protection against a fighter aircraft includedthe protection against the fall of a large airliner too if the impact takesplace with less damaging characteristics (lower speed of impact).

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1970s-1980s (2)

By the 1974, nuclear technology had advanced.

Possible to try to make a realistic estimate of the probabilitiesand consequences of nuclear power plant accidents that might

proceed beyond DBA limits to core melt. This was attempted by Rasmussen and his collaborators in the

Reactor Safety Study (RSS) (NRC,1975).

The RSS study team outlined logical sequences of accidentalsteps that could lead to the release of radioactive material,usually as result of a core melt.

They attempted to assign probabilities to each step of thesequence. When available, historical data were used as basesfor the projected probabilities; otherwise, engineering judgement

took their place.


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1970s-1980s (3) Before the RSS, it was widely assumed that only the DBAss could

lead to core melt and release of appreciable radioactivity. RSS showed that many more such sequences exist; in total the

probabilities of their occurrence exceeded that of the DBA.

These sequences include small pipe breaks and various transient-initiated events. Models of the physical processes were developed to assess the

magnitude and timing of the release, transport and deposition of theradioactive materials from the core through the primary system andthe containment to the environment.

Consequence models were also developed to evaluate the dispersalof radioactivity into the atmosphere so as to estimate the risks, thuscoupling the probability and the health effect consequences ofvarious accidents.

The RSS, published in 1975, was the first study that included allconceivable accidents and also less probable scenarios, such as thecatastrophic explosion of a reactor pressure vessel and an estimateof the probability of each scenario.

It was a trend-setter in nuclear power safety analysis.

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1970s-1980s (4)

As a result, RSS has been criticised and extended. Because of the many criticisms of RSS and the uncertainties inherent in

Probabilistic Risk Assessment (the probability data concerning the mostunlikely phenomena are scarce or even absent, given the impossibilityof studying these phenomena experimentally and the scarcity of

applicable real-life data), the methodology was not used before 1979 forreactor design, reactor operator training, or for regulation. Nobody could support the validity of the absolute quantitative risk

evaluations contained in it. At the same time, the validity of this study is universally acknowledged. Rasmussen report and similar studies are possible judgement

instruments in the nuclear safety field, but they cannot be used alone. Sound engineering evaluations, based on operating experience and on

research results are the necessary complement to the probabilisticevaluations.

After TMI accident, severe accidents (those accidents more serious

than those up then considered credible) were included in the designconsiderations for the nuclear plants.


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TMI accident - 1979 In March 1979, during a rather frequent plant transient, a valve on top of the

pressurizer of the TMI plant remained stuck open. Continuous loss of coolant, void reactor pressure vessel and full pressurizer.

It was believed that the RSS methodology was completely wrong because it had notpredicted that type of accident.

That particular sequence (TMLQ) was evaluated for the Surry plant to have afrequency of once in 105 years. If the RSS procedure had been applied to a Babcockand Wilcox reactor like TMI-2, the frequency would have predicted a frequency ofonce in 300 years.

The difference stemmed from: The pressure relief valve settings caused the valve to be released before the reactor

scram. The steam generator (of the once-through type) had a small heat capacity and dried

out in ten minutes, compared with a time of about an hour calculated U-tube SG.

The actual values of the probabilities and frequencies calculated in the reactor safetystudy may not be correct , but, if the methodology had been applied to the reactor atTMI, the plant specific scenario might have been noted, modifications might havebeen made, and the accident perhaps avoided.

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From TMI accident to Chernobyl (1)

This realization led to a general acceptance of the methodology ofProbabilistic Risk Assessment.

TMI accident completely changed the attitude of the industry towards safety

in all OECD countries. The provision of safety features previously considered to be pointless by

some was acknowledged as valid in the light of the possibility ofunforeseeable events.

Organizations were created for the exchange of information on operationalevents at nuclear plants and for the promotion of excellence in the nuclearsafety field.

Long lists of lessons learned were prepared and a three Mile IslandAction Plan was compiled, which contained a large number of specific

provisions against the possible repetition of similar accidents in the future. To implement them, an amount of money ranging between several millions

dollars and several ten millions dollars was spent for each plant .


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The concepts of Defence in Depthand of Safety Culturewerereinforced.

The Defence in Depth initiative is a concept meaning that many,mutually independent, levels of defence against initiation andprogression of accidents are created. The various levels includephysical barriers (fuel cladding, primary system, containment, etc.).

Safety Culture: the set of convictions, knowledge and behaviour inwhich safety is placed at the highest level in the scale of values .

As a result many countries gave attention to severe accidents. A severe accident is defined as one exceeding in severity the DBAs,

which are those against which plant safety systems are designed insuch a way that:

core does not exceed the limits of irreversible damage of the fuel(1200C maximum, 17% local oxidation of the cladding); external releases do not exceed the maximum tolerable ones,

according to the national criteria in force.

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Severe accident according to IAEA: accident conditions moresevere than a design basis accident and involving significantcore degradation.

All the OECD countries agreed on the need of studying andimplementing severe accident management technique on theirplants.

Examples of typical equipment and procedures for severeaccidents are the following:

portable electric generators, transportable from the plant toanother on the same site or on a different site;

procedures to supply electric energy to the essential loads, incase of total loss of electric power;

procedures for the voluntary depressurization of the primary

system in case of loss of the high pressure emergency injectionsystem, and so on.


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From TMI accident to Chernobyl (4) By the 1980s, all the plants in the OECD area were equipped with Severe

Accident Management Plans. Some countries (France, Switzerland and Germany) have installed filtered

containment venting systems to prevent the rupture of the containment in

case of a severe accident. In Italy, a set of criteria was developed:

95-0.1%. criterion, according to which, by the installation of appropriatesystems (filtered venting system) a release of iodine higher than 0.1% of thecore inventory could be avoided with a probability higher than 95%.

Preventative system for the voluntary depressurization of the primarysystem in PWRs and for the passive injection of water into the primarysystem for about 10 hours.

This core rescue system (CRS) could decrease the core melt probabilityby a factor of at least 10. The system was proposed as a modification ofthe design chosen for the Italian Unified Nuclear Design, but it was not

considered necessary by the designers at that time. A few years later, the designers applied it, to the passive reactor AP600 and

to a German reactor design. The voluntary primary system depressurizationhas subsequently been adopted by all the more modern PWR designs, suchas the European Pressurised Reactor (EPR).

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Chernobyl Accident There were two primary causes of the Chernobyl tragedy:

The plant had been designed with excessive optimism as far as safety wasconcerned.

In some operating conditions (low power, low steam content in the pressuretubes) the reactor was very unstable: an increase in power or a loss of coolantcaused reactivity insertions

With completely extracted control rods (a situation forbidden byoperational procedures), the potential instability was more severe

. The operators were working in a condition of frantic hurry for various

reasons.

The leakproof and pressure resistant containment did not include asignificant portion of the reactor itself: the fuel channel heads werein a normal industrial building.

A complete uncontained accident, therefore, happened.


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General lesson to be learned (1)

No weak point compromising safety must

be left in a plant.

Human errors will succeed in finding weakpoints and will cause disasters andfatalities.

Experience indicates that accident

possibility must be seriously consideredduring all the phases of the life of anuclear plant.

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General lesson to be learned (2)

Chernobyl reactors were not well known in the western world. The pertinent information was kept confidential because this

reactor (RBMK) could potentially be used for plutoniumproduction.

Copies of a safety analysis of an RBMK reactor (performed someyears before the accident) were circulated among the expertsonly after the accident: it concluded that this reactor did not meetthe safety standards in use in the Western world.

The Chernobyl accident had not much to teach the Westernnuclear safety engineers, but it was not possible to convince thepublic that such an accident could only happen in that specificdesign of reactor.

In Italy some political parties exploited the evident fear generated

in the population and led the country towards the immediate andsudden dismissal of the nuclear source.


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After Chernobyl (1) Nuclear plant design evolved by successive additions and had

become too complicated. It was useful to think to simpler systems, based on concepts of

passive rather than active safety.

Accidents should have modest consequences beyond the exclusionzone of the plant and should require small emergency plans,especially concerning the quick evacuation of the population.

The concept of the passive safety meant the use of systems basedon simple physical laws (safety injection systems on water reactorswhich use, as a motive force, gravity instead of pumps).

AP600 adopted this principle, a voluntary fast depressurisationsystem of the primary circuit and the provision of a water reservoir atan elevated position with respect to the reactor vessel.

Passive cooling of the containment was also incorporated in thedesign.

The rating of 600 MWe was initially chosen on the basis of a pollamong the US utilities, but a weak point of this concept has alwaysbeen the reduced power and its consequent bad scale economy.

In 2004 NRC approved the design of the AP1000.

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After Chernobyl (2)

In the French-German EPR of approximately 1400MWe, the passive safety has been adopted with ahigher degree of caution but with a strong tendencytowards the reduction of emergency plans.

Many precautions against severe accidents havebeen taken: molten core containment structures, core catchers,

multiple devices for the quick recombination of hydrogen,

voluntary primary system depressurization, etc.

New concept based on passive safety under study(Generation IV)


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Innovative nuclear applications -1

Innovative reactor concepts for:

energy production

reduction of nuclear wastes

EVOLUTIVE REACTORS

Reactor designs stronglybased on the existingreactor fleet (Gen II-Gen III

systems) with improvedcharacteristics for whatconcerns safety and fuelutilization

INNOVATIVE REACTORS

Reactor designs adoptingdifferent concepts withrespect to the existing fleet,

devised to largelyovercome present reactorsunder several points ofview

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Generation IV


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Evolutive reactors

EPR (European Pressurized Reactor, or Evolutive

Pressurized Reactor) Same idea ad PWR

Improved safety features, with an increased complexity ofthe plant itself

AP1000

Again, a PWR

More in the direction of simplification + passive safetyfeatures

http://www.ap1000.westinghousenuclear.com/

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Innovative Reactors

Generation IV International Forum (GIF):is a cooperative international endeavor

organized to carry out the research anddevelopment (R&D) needed to establish thefeasibility and performance capabilities of thenext generation nuclear energy systems.


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Generation IV Int. Forum Members

Argentina, Brazil, Canada, France, Japan,

the Republic of Korea, the Republic of SouthAfrica, the United Kingdom and the UnitedStates signed the GIF Charter in July 2001.

Subsequently, it was signed by Switzerland(2002), Euratom (2003), and the Peoples

Republic of China and the RussianFederation (both in 2006).

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Generation IV

The goals adopted by GIF provided the basis foridentifying and selecting six nuclear energy systemsfor further development.

The six selected systems employ a variety of reactor,energy conversion and fuel cycle technologies.

thermal and fast neutron spectra, closed and open fuelcycles and a wide range of reactor sizessizes fromfrom veryvery smallsmalltoto veryvery largelarge.

Generation IV systems were expected to becomeavailable for commercial introduction in the periodbetween 2015 and 2030 or beyond.


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Gen IV Safety & Reliability (1)

Excel in safety and reliability

Have a very low likelihood and degree of reactorcore damage

Eliminate the needEliminate the need for offsite emergency response

This requirement has got even larger relevance afterthe Fukushima events, since: an accident sequence may be more complex, or lasting-in-

time than foreseen;

the impossibility of actuating countermeasures properly (orin due time) must be accounted for, even in case of aperfect implementation of the nuclear safety culture(education, training and preparedness of the operators).

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Gen IV Safety & Reliability (2)

Cyber attack to a nuclear facility (happened in Iran) Possible introduction of errors in logic and in the decisions

of the operator, as a result of incorrect information

While we cannot eliminate the concept of risk, wemust limit it to the utility owing the plant.

The effects of whatever event occurring must beconfined into the plant, without involving its barriers,as if the plant were pre-sheltered from itsconstruction.


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Gen IV Sustainability

Generate energy sustainably,

and promote long-term availabilityof nuclear fuel

Minimize nuclear wasteMinimize nuclear wasteand reduce the long term stewardship burden

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Gen IV - Proliferation Resistance &

Physical Protection

Be a very unattractive route for diversion or

theft of weapons-usable materials.

Provide increased physical protection againstacts of terrorism


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Economics

Have a life cycle cost advantage over other

energy sources

Have a level of financial risk comparable toother energy projects

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Nuclear Energy Economics (1)

Nuclear energy programmes imply long-termcommitments from policy makers and investors, sofinancial risks and future liabilities arising from nuclear

activities deserve careful consideration.

Nuclear power plants are capital-intensive, but have lowand stable marginal production costs.

Investment typically represents some 60% of the totalgeneration cost of nuclear electricity. The capital cost ofa 1 GWe nuclear unit is roughly US$ 2 billion.

It takes a long time (two decades) to amortise the capitalinvested in a nuclear power plant.


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Once built, nuclear plants have rather low fuel andoperating costs.

The cost of uranium represents only some 5% of the costof electricity from nuclear plants: rises in the cost ofuranium have little impact on the total cost of electricity.

Because of the high energy density of nuclear fuel, nuclearenergy requires a very small flow of energy materials andmakes small demands on the natural resource base andthe environment

The large size of uranium resources and their balancedgeopolitical distribution worldwide ensure long-termsecurity of supply.

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Economically recoverable uranium resources are largeenough to cover demand for many decades at current

rates of consumption. Advanced fuel cycles (fissile material recycling) could

allow the resource base to be further extended by afactor of sixty or more.

A significant proportion of nuclear energy cost isdue to safety features designed to prevent nuclearworkers and the public from receiving radiation doses in

excess of permitted levels


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Nuclear Energy Economics (4) The production and use of electricity creates costs

external to traditional accounting practices: damages tohuman health and the environment.

Those external costs are supported by society as awhole, now or in the future.

Within a sustainable development framework, socialand environmental costs for present and futuregenerations must be taken into account.

Economists are looking for ways of valuing these costsand incorporating them into prices, i.e. internalising theexternalities.

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Stringent environmental and safety regulations.

Future financial liabilities arise from the need to coverthe costs of decommissioning nuclear facilities anddisposing of long-lived radioactive waste. The industryand governments must establish and guaranteeadequate funds for these liabilities.

The production and use of electricity creates costsexternal to traditional accounting practices: damages tohuman health and the environment.

Those external costs are supported by society as awhole, now or in the future.

External costs of long-lived radioactive waste disposaland plant decommissioning must be considered


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Assessments of competitiveness should be based upon

comparisons of full costs to society of a product or aservice.

Within a sustainable development framework, socialand environmental costs for present and futuregenerations must be taken into account.

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The need to run the plant at a high rate of utilisation for many yearsbefore the investment is paid back raises financial risks associatednot only with potential technical failures, but also with uncertainties

about the stability of regulation and the growth of market demand.

The relative competitiveness of alternative options for electricitygeneration depends strongly on the discount rate used to calculatecost estimates.

With a 5% discount rate, nuclear power plants that would be builttoday would compete favourably with alternatives in many countries,

but with a 10% discount rate gas-fired power plants would be thewinner nearly everywhere.


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High discount rates enhance the competitiveness of technologiesthat are not capital-intensive, such as gas turbines.

Low discount rates, which reflect a preference for a future consistentwith sustainable development goals, favour capital-intensivetechnologies such as nuclear power and renewable energy sources.

The nuclear industry sector requires a comprehensive infrastructure,a high level of technical and managerial knowhow, that contributesto increasing human capital assets. Therefore the nuclear industrysector brings macroeconomic and social benefits

Documents

Nuclear Safety History