MonoCEA GB 5/04/06 15:30 Page 3

Commissariat à l’énergie atomique e-den A monograph of the Nuclear Energy Directorate

Nuclear energy of the future: what research for which objectives?

Éditions techniques MonoCEA GB 5/04/06 15:30 Page 2

DEN monographs

A monograph of the Nuclear Energy Directorate Commissariat à l’énergie atomique, 31-33, rue de la Fédération 75752 Paris Cedex 15 Tél. : +33-1 40 56 10 00

Scientific comitee Michel Alexandre, Michel Beauvy, Georges Berthoud, Mireille Defranceschi, Gérard Ducros, Yannick Guérin, Yves Limoge, Charles Madic, Gérard Santarini, Jean-Marie Seiler, Pierre Sollogoub, Étienne Vernaz, Research Directors.

The following people participated in this work: Fanny Bazile, Patrice Bernard, Bernard Bonin, Jacques Bouchard, Jean-Claude Bouchter, Bernard Boullis, Franck Carré, Jean Cazalet, Alain Marvy, Valérie Moulin, Emmanuel Touron, Yves Terrien.

Publishing Supervisor: Philippe Pradel.

Editorial Board: Bernard Bonin (Managing Editor), Bernard Bouquin, Martine Dozol, Michel Jorda, Jean-Pierre Moncouyoux, Alain Vallée.

Administrator: Fanny Bazile.

Editor: Jean-François Parisot. Graphic concept: Pierre Finot. Cover illustration: Véronique Frouard.

Correspondence: all correspondence can be addressed to the Editor or to CEA / DEN Direction scientifique, CEA Saclay 91191 Gif-sur-Yvette Cedex. Tél. : + 33-1 69 08 16 75.

© CEA Saclay and Groupe Moniteur (Éditions du Moniteur), Paris, 2006

The information contained in this document can be freely reproduced, with the agreement of the Editorial Board and due mention of its origin. MonoCEA GB 5/04/06 15:30 Page 5

Preface

After a dazzling start in the 1950s as a promising, inexhaustible, cost-effective energy source, nuclear energy was rejected by majority opinion in several countries in North America and Western Europe three to four decades later, suddenly bringing its development to a halt.

Although the 1973 and 1979 oil crises marked the beginning of massive construction pro- grammes in the countries most heavily penalized by oil imports, and Japan in par- ticular, they were paradoxically followed by a gap in nuclear spending, first in the United States and then in Western Europe. However, more recent oil market tensions and emerg- ing concerns over non-renewable natural resources should have increased such spending.

There are surely many reasons for this pause, which can in part be explained by the acci- dents in Three Mile Island in 1979 and Chernobyl in 1986, which deeply impacted public opinion. On top of this, ecological movements and Green parties made their (highly publi- cized) fight against nuclear energy a key part of their platform.

In France, whose population, with the exception of one case, had never disputed nuclear plant construction, negative attitudes began to surface in the late 1980s concerning the nuclear waste issue. Given Andra’s growing difficulties in finding an underground laboratory site, the Government decided to suspend work in favour of a one-year moratorium and sub- mitted the issue to the OPECST (French parliamentary evaluation office for scientific and technological choices).

The Act of 30 December 1991 on nuclear waste management implemented the essence of the OPECST’s recommendations, in particular its definition of a diversified research pro- gramme and the basis for democratic discussion, thus helping calm the debate. That said, although it is now an accepted fact that long-term nuclear waste management is a neces- sity, there is still no guarantee that France will continue its electronuclear programme: for this reason, the recent energy act of 13 July 2005 merely aimed to “keep nuclear options open through 2020”.

However, this century should be marked by renewed collective awareness that our gener- ation’s energy needs cannot be met without concern for the environment and without pre- serving future generations’ rights to satisfy these same needs. This concept of sustainable development is an inevitable challenge to our society.

Today, it goes unquestioned that global warming due to increasing greenhouse gas emis- sions is a human-caused problem.The only remaining debate concerns the consequences of this climate change. Industrialized nations, which are for the most part responsible for the current situation, should feel particularly obliged to voluntarily take steps towards reducing emissions of these gases. Nuclear energy should gain considerable ground since, by nature, it does not produce this type of emissions and yet is an abundant, reliable and cost-effec- tive energy source.

The situation varies from country to country. On one hand, European countries such as Germany and Belgium have chosen to progressively stop using nuclear energy, even with- out making plans for reversibility. On the other hand, countries like China, South Korea, or,

Nuclear energy of the future: 5 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 6

closer to home, Finland, are making huge investments in developing this technology. Furthermore, according to a recent statement by President Bush, the United States has decided to launch new plant construction projects over the next ten years, picking up a process that had been on hold for over a quarter-century.

Following France’s national energy debate that took place in the first half of 2003, the par- liamentary bill on energy adopted in June 2005 established the decision to build a demon- strator EPR in preparation for the switchover when currently operating plants will be shut down.

Several signs lead us to believe that there could soon be a nuclear energy "renaissance", especially if the barrel of crude stays at or above the 70 USD mark. Nevertheless, the future of nuclear energy in our country, as in many others, will depend largely on its capacity to properly address the following two concerns: - First, its social acceptability: nuclear energy must be deployed under stringent safety and security conditions, generating as little final waste as possible, with perfect control of the waste that is produced in terms of its possible impact on human health and the environment. - Secondly, the availability of nuclear resources: it is important to guarantee a long-term supply of fuel, by preparing to resort to more economical natural systems which are less dependent on market fluctuations.

These topics are a key part of the CEA Nuclear Energy Division’s work. Indeed, this divi- sion is a major player in the research that aims to support the nuclear industry’s efforts to improve reactor safety and competitiveness, providing the Public Authorities with the ele- ments necessary for making decisions on the long-term management of nuclear waste, and, finally, developing the nuclear systems of the future, essentially fast reactors, which offer highly promising innovations in waste management and raw material use.

As a fervent partisan of sharing as much scientific and technical knowledge as possible to a broad public, I believe that this research work, which calls upon a diverse array of scien- tific disciplines often at top worldwide level, should be presented and explained in priority to anyone who would like to form their own opinion on nuclear energy. For this reason, it is with great satisfaction that I welcome the publication of these DEN monographs. Through close reading of these works, they can become an invaluable source of information for the, I hope, many readers.

I would like to thank all the researchers and engineers who, by contributing to this project, helped share their experience and knowledge.

Bernard BIGOT High Commissioner for Atomic Energy MonoCEA GB 5/04/06 15:30 Page 7

Introduction

Today energy problems are global problems. It is on the There are two conditions for this: firstly that we know how to international scale that we share resources and risks, in par- respond to public opinion concerns.Then that we are capable ticular those linked to climate changes caused by greenhouse of proposing new nuclear systems, even more effective in gas emissions. terms of safety or economy, but, above all, that will place in highest priority the sustainable development and non-pro- For this reason any new generation* of nuclear energy pro- liferation criteria. duction must be thought out based on serious projections on the international scale. But, making nuclear power acceptable is above all demonstrat- ing it “with proof”. From this point of view, the exemplary oper- Recent studies carried out by the World Energy Council or by ation of nuclear reactors for over 15 years, throughout the the International Energy Agency of the OECD provide us with world, is an invaluable advantage. The availability rates are the following trends: excellent, incidents, even minor, are decreasing and this enables public confidence to be gained. • An energy demand which will increase by 50 to 60% before 2020; In the last few years waste management has been seen as •A demand which will increase predominately in developing the main problem of nuclear power for public opinion. It alone countries; probably explains part of the defiance regarding nuclear power •Fossil energy which will continue to provide for the majority so well that it may have no future if we do not provide solutions of our needs; for it. That said, contrary to the idea often spread, technical

• Finally, in spite of national efforts, CO2 emissions which will solutions do exist… probably be greater than the Kyoto objectives. In France, as in other countries in fact, the management of less active waste and of that which has a shorter lifetime, is a reality already implemented in industrial disposal Mtep centres. It must be remembered that this repre- 16,000 sents more than 90% of the overall volume of 14,000 nuclear waste.

12,000 Renewables The question of high level and long lived waste, 10,000 Hydrogen that which, with a few percent of the volumes, con- 8,000 Nuclear centrates most of the radioactivity, remains. For 6,000 Gas this waste, the R&D employed in France, as out- lined by law, has enabled numerous results to be 4,000 Oil obtained. This R&D will allow, by the legal dead- Coal 2,000 line, in 2006, various technical solutions to be pro- 1971 1997 2010 2020

Source: AIE, World energy Outlook 2000 posed to the French Parliament for the manage-

Fig. 1. A global production of energy with 87% of fossile origin!… ment of this waste.

Our first objective is to reduce the quantity of waste produced These studies also show that beyond 2020, even more than at source. today, the environmental impacts will have to be studied with great urgency.

Nuclear energy has many advantages for being a satisfactory energy response, in the long-term, from the resources and environmental point of view. We believe that it will have in the future, its place in an energy “mix”, even more than today.

Nuclear energy of the future: 7 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 8

This involves evaluating and establishing the feasibility of This then involves, for final waste, proposing technical solu- processes enabling the waste to be separated, then the quan- tions, which enable long-term waste management, either by tity and the noxiousness to be significantly reduced: this is par- storage, or by permanent disposal. titioning* and transmutation*.The objective is to reduce the radiotoxicity of waste by a factor 100 by recycling The work carried out on conditioning* must enable processes and transmuting minor actinides. to be proposed guaranteeing sustainable containment and the possibility of reusing the waste in complete safety, within a France has already chosen to recycle plutonium. Firstly long-term storage* or deep geological formation disposal* because it is a recyclable energy material. Also, over time, it is perspective. the main element responsible for the radiotoxicity of waste. When exiting the reactor, spent fuel contains only 4% bona Finally studies are being carried out on the long-term storage fide waste and 96% and plutonium. In constant processes or on the disposal in deep geological formations progress, the processing of spent fuel, then its recycling are integrating reversibility requirements. solutions already implemented industrially in France. There again, we are starting to gather results: intact glass at In this field of recycling, the research in progress targets the 99.9% after 10,000 years, new storage concepts or even a development of new fuel assemblies which will enable pluto- new research laboratory for deep geological disposal. nium to be multiple-recycled, either in current water reactors or in EPR reactors, the deployment of which is envisaged in In France, these studies are carried out in compliance with the France.This would enable the stocks of plutonium with the cur- legal ethics and decisions which were made in 1991, in order rent reactors to be stabilized, or even reduced. to clarify by 2006 the Parliamentary and Governmental deci- sions. Once the plutonium recycled, a logical follow-up consists of partitioning then transmuting minor actinides (Np, Am and Cm) It is therefore up to the politicians to decide. But on a techni- which are, after plutonium, the main contributors of waste cal note, we will know how to deal with the small quantities of radiotoxicity.The partitioning processes, developed in the wake waste in question, and their low volumes originating from of that which is currently being carried out for plutonium, will energy production, in safe conditions, in disposal or storage enable these minor actinides to be partitioned from fission areas, for extremely long periods and assuring the traceabil- products, thus considered as the sole final waste to be vitri- ity of any necessary information. fied. As for the transmutation, its scientific feasibility is acquired, but its technical feasibility remains to be demon- strated and CEA is working on it, in an international, mainly European and American, collaboration.

The advantages of this partition- Objective: To assure waste ing/transmutation strategy are Directions selected Technical solutions Results very clear: it enables considerable 1. Conditioning Matrices and containers 1. Intact glass at 99,9 % reduction of waste radiotoxicity after 10,000 years over the long-term. Thus, if the 2. Storage • Durability 2. First storage concepts radiotoxicity of uranium used to and/or • Reversibility produce fuel is taken as a refer- 3. Disposal • Flexibility of the solutions 3. ANDRA research ence, the same level of radiotoxi- laboratory in construction city is reached: According to CEA /SACLAY, Nuclear Energy Directorate. • After several hundreds of thou- Fig. 2. A major stake… and realistic solutions. sands of years if the fuels are not reprocessed; • After 10,000 years if Pu is reprocessed/recycled according to the current solutions; At present, various waste management strategies may be • After some hundreds of years if only fission products are left implemented complementarily. Reversible direct disposal, as in the glasses and if the actinides are recycled. will be the case in the USA with Yucca Mountain, storage in view of recycling at a later date, for example to give the sys- tem flexibility, or even immediate reprocessing and recycling, as is the case in France.

From now on, the recycling of all actinides seems to be a 1. For the meaning of all technical terms, refer to the developed glossary situated at the end of work. The terms in fat accompanied with an aster- strong specification for reducing waste and proceeding toward isk send back to the glossary (pp. 103-106). [Note of the Editor.] sustainable development in nuclear energy. This criterion for

8 Introduction MonoCEA GB 5/04/06 15:30 Page 9

reducing waste is furthermore widely repeated in the defini- The CEA undertakes to work on three of them in particular: tions for the designs of nuclear systems of the future. • The sodium-cooled fast neutron concept, on which CEA Today’s challenge is imagining the nuclear systems of the already has a great deal of experience regarding reactors but future. which requires improvements regarding fuel cycles;

With a first question: what future are we talking about? The • The very high temperature gas-cooled and thermal neutron objective is to develop systems that can be deployed from the system for the production of hydrogen (VHTR); industrial point of view by 2030-2040. There are two reasons for this: firstly time is needed in order to propose truly innova- • The gas-cooled and fast neutron system (FNR-G), which tive systems. If improvements in safety and competitiveness offers a promising alternative in relation to the sodium, are expected, it is in fact technological ruptures that we are regarding both reactor and cycle. speaking of in terms of fuel, cycle and reactor core*. Then, it is the date on which the studies show an increased inflection On sodium reactors, the CEA has an important R&D pro- of a requirement to use nuclear power with in particular the gramme in partnership with countries such as Japan and response to the electricity requirement but also the production Russia. We are attempting to take advantage of the experi- of hydrogen*, the desalination* of seawater, etc. ence gained and the advantages of sodium, whilst improving the system on the difficult points. There already seems to be a convergence of opinions on the international level regarding the criteria the nuclear systems Various concepts of gas reactors were studied in the 70s-80s. of the future must meet. These criteria, which privilege sus- Since, considerable progress has been accomplished in par- tainable development, determine the order in which it will be ticular in the field of high temperature materials. Our ability to necessary to try and decide on the research priorities. obtain high temperatures, and therefore high yields, place these reactors at the forefront.

The R&D in progress concerns the materials, helium technolo- gies, and the modelling supporting the developments.

One part, mostly dedicated to the VHTRs, concerns the mate- Safety rials for the high temperatures, the exchangers and the Economy thermo-chemical cycles.

Reduction of waste The research centred on FNR-Gs will focus on the highly inno- Economy vative fuels for these reactors. of natural resources Reduction risk Nuclear energy will without a doubt play an important role in of proliferation the future in order to meet international energy requirements. This, however, presupposes that the decision-makers know

According to CEA /SACLAY, Nuclear Energy Directorate. how to find and implement the correct responses to the ques- Fig. 3. Nuclear systems of the future: the 5 basic criteria. tion of waste, and to best take account of the sustainable development criteria.

It will be necessary to innovate and redouble efforts in order to Research on this nuclear power of the future is developing propose new concepts. This is carried out in a totally new within a largely international framework. For example, ten framework which seeks to promote international cooperation, countries plus the European Union are participating in the the sharing of tasks and results, and this within the group of American Generation IV initiative. This international work has countries who believe in the future of sustainable nuclear already defined by consensus the most promising nuclear sys- power… tems and drafted a common research and development plan for these systems.

Among the six concepts which have been selected after two years of preliminary work, the majority have a closed fuel cycle* and most have a fast neutron* core. This is the result of the sustainable development, waste reduction and optimisa- tion and use of natural resources criteria.

Nuclear energy of the future: 9 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 10 MonoCEA GB 5/04/06 15:30 Page 11

The origins of current civilian nuclear power

Fifty years ago, in December 1953, right in the middle of the Ordinary water reactors, dominant cold war, the “Atoms for Peace” speech by the American species President Eisenhower before the United Nations, prompted a It is necessary to underline the industrial feedback, during deep mutation in the role of nuclear energy, until then limited these past decades, from all of these second generation reac- to military usage. The president promoted its development for tors, which currently capitalize over ten thousand years of civil and peaceful use in order to “serve the needs rather than operation: it has in particular enabled the performances of the the fears of humanity”. The following year marked the start of nuclear energy production to be demonstrated with a very the commercial generation of nuclear electricity in Russia. competitive kilowatt-hour cost in relation to that of fossil energy. These initiatives have influenced energy policies because over these past fifty years, nuclear energy has developed widely throughout the world: 440 300 reactors were in operation at the end of 2004, representing approximately 360 GWe installed in more than 30 countries.The pro- 250 portion of nuclear power in the generation

of electricity is 16% (30% in countries of the Capacity in GW 200 OECD), which also represents 7% of the primary energy. 150 The first generation of reactors includes first prototypes constructed mainly in the United States, Russia, France and Great Britain. 100 This first generation, developed in the 1950s-1960s, operated with natural ura- 50 nium as was not yet com- mercially available. This is why during this period France developed the system called 0 BWR Boiling water Heavy water Graphite-Gas Water-Graphite Fast Total Natural Uranium Graphite Gas. (HWR) GCR (Chernobyl) GW in 1990 138.7 48.0 9.9 7.2 10.7 0.61 215.1 GW in 1997 167.7 61.6 12.4 9.2 7.8 0.44 259.1 It was then the Generation II of reactors which was deployed in the 1970s to the Fig. 4. Two main types of water reactor coexist: pressurized water 1990s and which corresponded to most of the fleet currently reactors (PWR) and boiling water reactors (BWR). In the first, water in operation throughout the world. This generation arose from from the primary circuit is under high pressure, which maintains it the need occurring in the ’70s to make nuclear energy compet- below boiling point although the temperature is significantly above 100°C; in the second, the pressure is lower, and the water boils on itive and to reduce the energy dependence of certain coun- contact with the fuel. tries at a time when considerable tensions were felt on the fos- sil energy market.

This period was that of the deployment of pressurized water Overall, this industrial maturity, this satisfactory competitive- reactors (PWR) and boiling water reactors (BWR), which ness and this favourable feedback have contributed consider- together currently constitute over 85% of the global electro- ably to renewing the electricians’ confidence in nuclear energy. nuclear fleet. The ready availability of their power plants and the possibility, for some of them, to see their lifetime extended up to 50, even 60 years, strengthens this trend.

Nuclear energy of the future: 11 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 12

Plants installed

1 plant in construction Gravelines (execution orderrrr given) Units permanently Chooz shutdown (11 units) Penly

Flamanvile Paluel Cattenom

Nogent-sur-Seine Mont d’Arrée The neutrons produced by a fission Saint-Laurent- Dampierre reaction may induce new fissions of des-eaux Fessenheim other fissile nuclei present within their Belleville Chinon vicinity, and thus contribute to maintain- Reactor system ing the chain reaction. Natural Uranium Civaux Graphite-Gas Gaz-Heavy water Bugey In a PWR, the water is both a coolant Creys-Malville Saint-Alban and neutron retarder. Saint-Maurice PWR* open circuit Le Blayais cooled Cruas The water circulates across a forest of PWR closed/looped circuit cooler Tricastin fuel assemblies, long bundles of thin Marcoule zirconium alloy metal tubes, where the *Pressurised ordinary Phénix Water Reactors Golfech uranium oxide or plutonium ceramic pellets are stacked.

0 100 km This water which circulates in a very Source : EDF thick steel closed circuit, yields its calo- Fig. 5. There are 59 reactors in France, producing a capacity of 63 ries by making the water of a second- GWe. France has replaced all of its first generation “graphite gas” ary circuit boil into a steam generator. The steam thus pro- reactors with PWRs. duced will activate the turbo-alternator.

After being distributed in the turbines, the steam is condensed Given the lifetime of the reactors and the time necessary for by way of a new water circuit, itself in thermal contact with a developing new systems, water reactors will certainly remain cold source, atmosphere, river or sea. preponderant in the global nuclear fleet up to 2030, and prob- ably during all of the first half of the 21st century.

The operation of a pressurized water

A pressurized water reactor is none other than a developed γ radiation Fission product device designated to heat water, with inside the boiler a pres- sure of 150 bars and a temperature of 300°C. The principle of Fissile such a reactor is to permanently maintain fission reactions of Free atom the uranium or plutonium nuclei within an environment, called neutron Freed reactor core*. Each fission, induced by the neutrons present neutron in the core, releases energy in the order of 200 MeV*, and pro- duces two or three additional neutrons, one of which serves to maintain the chain reaction*, the others being absorbed in Fission product (the water or) the structures or lost outside of the core. γ radiation

A pressurized water reactor is from the group of reactors, Fig. 6. : under the impact of a neutron, a heavy nucleus such as uranium 235 may fission, and provide two lighter called thermal neutron, that is the high energy neutrons pro- nuclei (fission products) and a few neutrons. The reaction releases duced by the fission are slowed down by successive shocks in energy 200 million times higher than that typically called into play in an environment that is called a moderator*, in order to obtain a chemical reaction between atoms or molecules. thermal equilibrium with this environment.They therefore have a much higher probability of inducing new fissions.

12 The origins of current civilian nuclear power MonoCEA GB 5/04/06 15:30 Page 13

Fig. 7. The neutrons produced by a fission reaction may induce new fissions of other fissile nuclei present within their vicinity, and thus contribute to maintaining the chain reaction.

Primary circuit

Vapour generator Secondary circuit vapour water

Pressurizer Turbine

Cluster command mechanisms primary Generator pump

Reactor Water core supply pump Condenser Vessel

Reheater Collant water

Fig. 8. Diagram of a pressurized water reactor (PWR).

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The fuel and the fuel cycle

Fig. 10. Fuel rod for a PWR is designed to supply the power expected Plug reactor. Orifice for pressurisation from the reactor, by best using the fissile material. The design

of the fuel element must in addition allow a certain flexibility in Upper plug the reactor operation, in order to enable it to adapt to the vari- ations in power imposed by the system. This must be carried out without releasing radionuclides* from the nuclear reac- Spring tions into the reactor’s primary circuit.These constraints com- bine in fact to give the nuclear fuel leaktightness, robustness and reliability qualities. UO2 pellet Zircaloy cladding

The fuel assembly of an ordinary water reactor is always made Lower up of “fuel rods*” containing the nuclear materials, arranged plug in a square lattice array in a “structure” assuring in particular the mechanical maintenance of the rods. Control cluster

Upper The fuel rod is made up of pellets of uranium oxide or mixed end fitting uranium and plutonium oxide (diameter and height in the order of 1 cm) stacked in metal tubes (cladding* in zirconium alloy) sealed at the ends (leaktight).

Guide-tube

Mixing grid

Fuel rod

Lower end fitting

Fig. 9. UO2 fuel pellets. Fig. 11. 17 x 17 Fuel Assembly and control cluster.

The robustness and reliability of the fuel must enable a long remain leaktight in incidental or accidental situations, even at stay in the reactor (currently 4 years, with an objective of 6 the end of the fuel rod’s life. That said: years towards 2010 for French reactors). •Some fission products are gaseous: their production pro- The integrity of the cladding is very important because this is gressively increases the pressure inside the cladding; what constitutes the first barrier* between the radioactive • The chemical composition of the pellets is modified by the products and the environment. The fuel rod’s cladding must appearance of fission products and actinides;

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• The fuel ceramic swells under irradiation and imposes a The fuel is taken out of the reactor when it no longer contains stress on the cladding which contains it (pellet-cladding enough fissile nuclei in order to maintain the chain reaction interaction). (typically at the end of four years in a water reactor).

Only the odd Pu and U 235 isotopes are fissile to thermal After its stay in the reactor, the fuel no longer contains enough neutrons. The irradiation of the U 238 form of Pu. fissile material to maintain the chain reaction, but it is not nec- essarily exhausted. As shown in the diagram above, it still con- In a water reactor, a certain number of neutrons are absorbed tains a large quantity of fissile and fertile* material, which is by the water: it would therefore be impossible to maintain the important to recover. It also contains fission products and chain reaction if natural uranium, which only contains 0.7% fis- minor actinides which make it extremely radioactive and diffi- sile 235 isotope, was used for fuel. It is therefore necessary cult to handle. to enrich the uranium, up to a content of approximately 4% of U 235 (see inset). The finality of the reprocessing is double:

• Recovering the recyclable energy materials; • Separating these materials from the true waste, and condi- tioning* the latter in an inert and safe form (vitrification*).

In France, these operations are carried out in the Cogema U 238 U 235 96 plant IN La Hague. 4 Uranium 238

Uranium 235

3 REP UOX Plutonium

Pu Minor 3 actinides 2 Fission products 11U 238 5 0,1 PF 93

Fig. 12. Reactions within the standard fuel assemblies in the PWRs (45,000 MWd/t).

The combined play of fissions and neutron captures in the fuel of the water reactor may be summarized as follows (see figure below): we start with 100 uranium atoms, four of which are iso- tope 235 (fissile) and 96 isotope 238. Of the four, only one will survive, and three will undergo fission.

Fig. 14. The COGEMA reprocessing plant in La Hague, in which the Of the initial 96 U 238, three will be transformed into Pu and spent fuel reprocessing and waste conditioning operations are car- 93 will survive. Of the three Pu formed, two will undergo the fis- ried out. sion and only one will survive. In total, there will have been 3+2 = 5 fissions: only 5% of the heavy metal will therefore be consumed in a water reactor. In a fast neutron reactor*, the Most of the radiotoxicity of the spent fuel comes from pluto- schema would be very different with a greater consumption of nium.This is an additional reason for recycling it and not leav- the fertile isotope U 238. ing it in the waste.

U 470 kg Pu 5kg A.M. 0,7 kg P.F. 25 kg (94 %) (1 %) (0,15 %) (5 %) Recyclable materials Final residue

Fig. 13. Composition of a 500 kg enriched uranium assembly after its passage in a reactor.

16 The fuel and the fuel cycle MonoCEA GB 5/04/06 15:30 Page 17

Reprocessing plant Recyclable materials U

Uranium

Pu

Plutonium PF Structure Technological waste waste AM

Final waste

Vitrified Compacted Cemented residue waste waste

Fig. 15. The streams through the reprocessing plant.

The The closed fuel cycle is the one practized in France, Germany, Switzerland and Japan. The following substages are found: It is not the uranium ore directly which constitutes the nuclear • Chemical reprocessing of spent fuel in order to recover the fuel. So that the heavy nuclei can be used in a reactor, they fissile and fertile materials that it still contains, in view of recy- must follow a “fuel cycle*” which combines numerous indus- cling them; trial stages: • Recycling of the plutonium in the form of MOX* fuel (acronym • Extraction of the uranium ore; for Mixed OXide fuel); • Concentration of the ore; • Conditioning of the waste, and, in particular, vitrification of • Conversion of the uranium concentrates into gaseous ura- highly resulting from the fission; nium hexafluoride (UF6); • Final disposition of the conditioned waste. • Isotopic enrichment* of the uranium in the UF6 form, in order to increase the proportion of U 235 fissile nuclei, too low in Each cycle facility, enrichment, manufacturing, or reprocessing natural uranium; plant is dimensioned is in order to supply several dozens of • Manufacturing of the fuel (conversion of the fluoride into large reactors. enriched uranium oxide UO2, making into pellets, pellet sin- tering*, rodding, assembly of rods into bundles). Manufacture Enriched of fuel The fuel produces energy for approxi- UO2 fuel mately four years in the reactor. The uranium last stages are therefore: MOX fuel Storage New • Interim storage, under water, of the UO2 fuel spent fuel; • Management of the spent fuel. This Enrichment New MOX fuel stage differs according to what is Reactor Plutonium considered as a “closed” or “open” Conversion cycle. Recyclable Spent uranium MOX fuel The open cycle, which is not really a Spent cycle, ends by the final disposition of Natural UO fuel uranium Concentration 2 the spent fuel, therefore considered in Reprocessing block as waste*.The open cycle is cur- rently practized in the United States, Extraction Final residues Sweden, etc. minerai Permanent disposal

Fig. 16. The nuclear fuel cycle.

Nuclear energy of the future: 17 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 18

The enrichment of uranium Why recycle plutonium? MOX fuel

Today, plutonium is recycled in water reactors, PWRs and An important stage of the cycle is uranium enrichment. Isotopic partitioning is a very difficult undertaking because the isotopes BWRs which constitute the main part of the global electro- to be separated have the same chemical properties and nuclear fleet.This enables saving enriched uranium, for which almost the same physical properties. plutonium is substituted in part, and preventing the plutonium ending up in final waste or only accumulating “on shelf” after Two main enrichment techniques are industrially implemented having been partitioned during the reprocessing of spent fuel. throughout the world: This recycling is carried out in MOX fuel. The reprocessing/ Gaseous diffusion, which consists of passing uranium, in the recycling combination also enables the quantities of spent fuel gaseous UF6 form, into a porous medium by exploiting the fact stored in pools to be significantly reduced. that the light isotope diffuses a little more quickly than the heavy isotope. The elementary process enriches very little, A MOX fuel, made up of a solid solution of plutonium and ura- which obliges the operation to be repeated a great number of nium oxides, is outwardly in every way identical to the enriched times in succession in order to obtain the suitable level of enrichment. uranium fuel that it replaces.The pellets which fill the cladding have identical dimensions: only their composition and their manufacturing process change.

In the core of a water reactor, due particularly to the presence of non fissile plutonium isotopes, it is necessary to place approximately twice as much plutonium in order to obtain the energy equivalence of an assembly enriched with U 235: in order to replace the uranium enriched to 4%, a mixture con- taining approximately 8% of plutonium and 92% of depleted uranium will be necessary. At the end of its life, the MOX fuel will contain no more than approximately 4% of plutonium. There is thus a net consumption of plutonium: the use of MOX enables the increase in the plutonium inventory to be limited in the fleet of reactors.

Fig. 17. The Georges Besse enrichment plant, in Pierrelatte. The recycling of spent fuel in the form of MOX began experi- mentally in Belgium at the beginning of the 60s. It was then industrialized in this country, in Germany and in Switzerland, Expensive in energy, gaseous diffusion is currently being then in France from 1985. Today, Japan is preparing, in turn, replaced by ultracentrifugation, which consists of making the to “MOX” BWRs and PWRs, and the United States is seriously UF gas circulate in a centrifuge rotating at very high speed. 6 thinking about it. The heaviest molecules concentrate on the periphery, which enables the two isotopes to be partitioned. As each centrifuge has a low material In France, EDF decided to recycle its plutonium progressively flow rate, this tech- in some of the reactors of its fleet. The 20 MOX reactors recy- nology therefore cle all of the plutonium effectively extracted by reprocessing requires many cen- EDF fuel at the UP2-800 plant in La Hague. The “plutonium trifuges to be work- inventory” of an MOX PWR is balanced: as much plutonium is ing at the same produced in the enriched uranium fuel bundles as is con- time. sumed in the MOX bundles.

The economic profitability of MOX depends a great deal on the authorized irradiation rate, that is the overall quantity of energy that a given fuel may supply, hence the research, cur- rently carried out, which aims to increase this rate. No funda- mental obstacle opposes a long irradiation time for the MOX, because the behaviour of MOX assemblies in reactors is very similar to that of uranium fuels.

Fig. 18. A succession of centrifuges for the enrichment of uranium.

18 The fuel and the fuel cycle MonoCEA GB 5/04/06 15:30 Page 19

Radioactive waste and its current management

Origin of radioactive waste

When a neutron causes the fission of a heavy nucleus, it splits Category B: low and intermediate level (A) long lived waste into two unequal pieces. These fission fragments are rarely (several thousands of years and more). Example: the spent stable nuclei. Apart from fission products, the neutrons induce fuel rod cladding segments, after dissolution of the fuel itself the formation of actinides and activation products, originating during reprocessing. from their neutron capture by non-fissile nuclei, radioactive species that are partly found in waste. The radioactive decay Category C: long lived waste and high level waste, emitters of of these various species may be, according to the case, fast, α, β and γ radiation, release heat for several hundreds of years slow or very slow, from fractions of microseconds up to billions and remaining radioactive much longer. It concerns either of years.These various species, partitioned during reprocess- unprocessed spent fuel (four countries having renounced ing, constitute the main source of high level and long lived “reprocessing”), or glass containers from the reprocessing and waste. which incorporate fission products and minor actinides.

However, throughout the fuel cycle and during the operation of In France, rather than speak of A, B or C, ANDRA* and the the reactor, inert materials are contaminated by radionuclides Nuclear Safety authority thus classified waste, according to resulting from nuclear reactions in reactors. These are care- the system implemented for their long-term management: fully isolated and conditioned and constitute another category of waste, called “low or intermediate level”, much less radioac- tive but more abundant. In this category, waste contaminated by radionuclides but which has another origin than the elec- tro-nuclear industry and which are caused by conventional industry, research or medicine are also found.

Short lived Long lived The various categories Very low level VLL Disposal at Morvilliers Secured for of radioactive waste (Aube) since 2003 mine tailings

For its daily management, radioactive waste is Low level LL Centre de stockage Dedicated disposal de l’Aube under review classified according to two criteria: • The level of activity*, that is the intensity of Intermediate level IL “A” waste “B” waste the radiation that it emits, which conditions High level HL “C” waste “C” waste the importance of protections to be estab- lished, in order to protect ourselves from radioactivity; • The radioactive half-life* of the products contained, which What quantities? enable the duration of its potential harmfulness to be defined. In France, where three quarters of electricity is nevertheless Thus in general three categories of radioactive waste are dis- produced by nuclear energy, the quantities concerned repre- tinguished. sent less than 1 kg of radioactive waste per inhabitant and per year, that is 0.04% of the industrial waste (2,500 kg/inhab- Category A: low and intermediate level short lived waste itant/year). This quantity is distributed as follows: (radioactive half-life less than 30 years). Its radioactivity (β and γ) will be reduced to a level comparable with natural radioac- • 900 grams of “A” waste, which however only contains tivity between now and 300 years. It may come from power 5% of the overall radioactivity; stations and fuel cycle plants, but also from hospitals, labora- •90 grams of “B” waste; tories, industry, etc. •10 grams of “C” type.

Nuclear energy of the future: 19 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 20

The annual production of “B” and “C” waste, from the repro- cessing in La Hague of spent fuel from French reactors, is in the order of 700 m3 per year, of which less than 200 m3/year for glass. “B” and “C” waste is currently stored in La Hague (but the waste from the reprocessing of foreign fuel is sent back to its owners).

The ultimate future of long lived waste (“B” and “C”)

A seemingly necessary solution From the beginning of nuclear power up to the 80s, most spe- cialists shared a common vision of the final management, the Source: ANDRA. disposal of highly radioactive waste in deep geological strata: Fig. 19. The centre de stockage de l’Aube, for category “A” waste (short lived). in order to permanently isolate it from the human environment (today known as the biosphere), it would be buried in a leak- tight way, deep enough, in a fairly stable geological stratum, The overall production of A waste (packages included) is isolated by judiciously arranged “engineered barriers”. Under 3 approximately 15,000 m /year, a volume which regularly these conditions, the time necessary for the radionuclides con- decreases thanks to the efforts of the producers. After condi- tained in the waste to migrate up to the surface, after corro- tioning, the packages are sent to the Centre de Stockage de sion of the packages by ground water, would largely exceed l’Aube (CSA). ANDRA stacks these packages in reinforced the time necessary for the radioactivity to decay and return to concrete cells which, after filling and packing out the spaces a natural radioactivity level. with gravel or mortar, are sealed with a concrete slab and coated with a waterproofing polymer. Lastly, a leaktight cover Almost all of the countries equipped with reactors have stud- will be placed and the site covered with a few metres of earth. ied variants of this same solution, according to the geologi- 3 The overall capacity of the CSA is 1 million m , which, at the cal nature of their subsoil and the respective qualities of the current rate of production of this waste, assures it an operation stratum envisaged: salt, clay, granite, basalt, etc. Throughout at least until 2050. the entire world, approximately fifteen underground laborato- ries have been installed to study on site the characteristics of the stratum which would host the waste and the behaviour of the geological barrier. The m3 /t main topics of study concerned and still con- 3.5 cern the mechanical resistance of rocks, the Conditioned 3 spent fuel network of faults, the physical chemistry and the flow rate of the ground water, the mech-

2.5 Bitumines anisms and the degradation kinetics of the packages, etc. 2 Reduction technological Technological However, in spite of this research, no long waste waste 1.5 lived and high level waste disposal has Bituminisation stop yet been implemented in the Western 1 Structural 2 Compacting waste world . In France, a law enacted on the 30 commissioned 0.5 December 1991 prescribed the continuation Glass of research on the long-term management of 0 long lived and high level radioactive waste. Design 1991 1995 2003 Fuel disposal values values values values in status (estimation)

Fig. 20. The volume of conditioned waste regularly decreases thanks to the efforts of producers.

2. A deep disposal site of long lived intermediate military waste was opened and commissioned in the USA, in 1999 on the WIPP site (New Mexico).

20 Radioactive waste and its current management MonoCEA GB 5/04/06 15:30 Page 21

The steering of the research relating to lines 1 and 3 is entrusted to CEA, that of the research for line 2 is a matter for ANDRA.

Line 1 programmes have permitted the defini- tion and experimentation on the laboratory scale of enhanced partitioning processes, as well as a certain number of experimental demonstra- Fig. 21. Storage of vitrified waste on the COGEMA site at La Hague. tions of the physical feasibility of the transmuta- tion of certain long lived radionuclides. Partitioning/transmutation offers the prospect of This research has mobilized the entire French nuclear scien- considerably reducing the quantities to be disposed of, and tific community and takes advantage of internationally accu- therefore the cost of disposal, but final waste will always mulated knowledge. It is declined according to three main remain.This leads to the belief that geological disposal will be points: necessary.

• Line 1 concerns the methods of enhanced partitioning of Research on disposal results in the digging of an underground waste from very long lived radionuclides and the possibilities laboratory in a clay formation in the Parisian Region, on the of their transmutation by nuclear reactions into shorter lived Bure site, at the edge of Meuse and Haute-Marne, under species, or even, ideally, stable nuclides*.The reprocessing Andra’s responsibility. CEA is also associated with this of spent fuel is a mandatory prerequisite for any partitioning/ research, in the capacity of main contractor or service provider transmutation; for some experiments.

• Line 2 concerns geological disposal and involves the con- Studies on the long-term conditioning of waste are being con- struction of underground laboratories to study on site the for- tinued, with a large knowledge base between disposal and mations presumed as favourable; storage.

• Line 3 concentrates on the conditioning of waste in view of A Commission Nationale d’Évaluation (CNE) – National enabling, if necessary, its storage in complete safety over Evaluation Commission –, consisting of experts appointed by long periods. the government, follows the progress of this research and reports annually to the Parliament and the Government.

In 2006, at the end of these 15 years of research and accord- ing to their results, the national representation will once again take hold of the subject and will make the necessary decisions. Line Enhanced partitioning Line Conditioning 1 3 and storage

Line Reversible disposal 2

Fig. 22. The three main lines of research on waste management.

Nuclear energy of the future: 21 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 22 MonoCEA GB 5/04/06 15:30 Page 23

The decommissioning and dismantling of nuclear installations

The issues long timeframe enables radioactive decay and therefore eas- ier protection of the workers who proceed with the deconstruc- Nuclear installations, whatever their nature – laboratories, con- tion operations. It also facilitates the storage then the final dis- trol or production plants, experimental or electricity producing posal of the radioactive waste. reactors, radioactive waste reprocessing installations, etc. – have a limited operating time. When their nuclear installations become old, many countries are led to shut down operation, Decommissioning-dismantling: decommission them and dismantle them. The end of life of a one of CEA’s important issues nuclear installation may be caused by the completion of exper- imental programmes planned in the installation, the obsoles- A historical player in nuclear research in France, the CEA must cence of materials and processes, economic (optimization of manage the heritage of the past. It first involves the recovery means, cost of maintenance) or safety and security (change in work and conditioning of old waste. CEA also has numerous the regulations) considerations. installations of various types to dismantle in its own centres. Cleanup and dismantling actions from now on constitute one Decommissioning and dismantling* (D-D) aims to enable of the important requirements of CEA’s policy. the partial or total liberation of a nuclear site. Since the beginning of 2002, the part of the actions that can Three stages may be distinguished for the decommissioning be attributed to “catching up with the past” is covered by a ded- of a nuclear installation: the permanent closure, the deconta- icated fund taken from CEA’s participation in the group. mination-dismantling, then the demolition and liberation of the In particular, this concerns the management of old waste (the site. production of which is prior to 1992), spent fuel and useless radioactive sources, the dismantling of installations placed in In the case of a reactor, the spent fuel is removed from the permanent shutdown, the cleaning up of the environment, the core and stored or reprocessed. The circuits are drained, the construction of service installations and the manufacturing of operating systems switched off and the openings to the exte- transportation packaging relating to these actions. The use of rior locked and sealed. The containment atmosphere is the dedicated fund is controlled by a Monitoring Committee, checked and the access to this containment is restricted; mon- whose members represent in particular CEA’s sponsoring itoring systems are installed. In general, permanent closure departments. intervenes very shortly after the permanent shutdown of the reactor. The R&D requirements in the nuclear field and the orientations taken in order to meet them lead CEA to grouping the major- Then the decontamination of the surfaces of the buildings and ity of the experimental nuclear installations in operation in the material takes place. Decontamination techniques serve and Marcoule in the not so distant future (in the to reduce the installation’s radioactivity, to clean up the metals order of 10 years). The number of installations to be treated and the concrete in the aim of facilitating the access to the (approximately thirty installations from 2001 to 2010) means work areas and the handling of the elements and material to that CEA’s decommissioning-dismantling programme is very be dismantled, to enable the cutting work and to meet the stan- large in volume. dards regulating the evacuation of waste. All of the operating equipment is dismantled and, after checking its residual In 2012, CEA will have completed the dismantling and radioac- radioactivity, recycled or temporarily stored. Only the reactor’s tive cleanup of the Fontenay-aux-Roses site and in 2015 that structures, in particular, the vessel and its protective shielding, of the Grenoble site installations. are left on site. Only the LECI* hot laboratory, for the programmes concerning To finish, in a third stage, all of the remaining materials and materials and structures, and the Orphée reactor, for basic the installation itself will be dismantled then the site decom- research programmes, will remain in Saclay. missioned and liberated for other uses. In some cases, a very long timeframe may pass, which may reach several decades after the shutdown of the installation, up to this final stage.This

Nuclear energy of the future: 23 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 24

Cadarache, which will group between now and ten years a large part of the experimental nuclear installations, must be able to manage all of the waste produced on the site locally and offer its capabilities to other Centres, for waste which is not their own. It is therefore at Cadarache that investment efforts regarding service installations are concentrated.

The decommissioning-dismantling: an important emerging market Photo STMI.

Decommissioning practices are realizing their full potential and © may be considered from now on as a controlled phase of a Fig. 24. Institut national des radioéléments – nuclear installation’s life cycle. Fleurus/Belgium: decontamination by gel of the C2 cell (XEMO I chain). Final status. A few figures illustrate the scope of the commercial D-D issues: more than 500 nuclear power plants have already been constructed and operated throughout the world, among which 108 were decommissioned in January 2005. In addition to the Existing and future technologies power plants, there are also plants connected to the manufac- turing of fuel and reprocessing of spent fuel, a part of which Dismantling techniques already exist and installation design has already been or will soon be decommissioned. and decommissioning projects benefit from large amounts of feedback. As a general indication of the overall level of the D-D costs, the United States regulating body demands that operators In general, decontamination techniques call upon chemical, have at least 164 million dollars (2000 value) in order to mechanical or thermal processes, or a combination of these. decommission and dismantle a conventional pressurised In order to decontaminate concrete or metal surfaces, the very water reactor. high-speed projection of dry ice granules and the use of chem- ical gels or decontaminating foams are used for example. The average age of nuclear power plants in OECD countries is approximately fifteen years, in relation to an average effec- Dismantling calls upon cutting techniques for metal or concrete tive lifetime of at least 30 years. The decommissioning rate structures. Mechanical (such as sawing or high pressure water should peak around 2015. jet) or thermal (plasma torch) processes are used for example.

France is characterized by the large number (six) of graphite- Radiological measurement techniques are used to address gas reactors which have been shut down, and by the number the inventory of radioactive stocks in the installation, sort the of R&D and demonstration power plants currently shut down. materials and waste according to their category, and to take the necessary provisions to protect the workers.

Dismantling uses various techniques: removable shielding, temporary airlocks and cells, mobile filtering and ventilation systems, special clothing, ventilated protective suits and masks.

Dismantling also uses lifting and handling equipment, and makes extensive use of remote control techniques: remote handlers, semi-automatic tools enabling the employees to work at a cer- tain distance from the sources of radiation.

Fig. 23. Projection of pressurized foam.

24 The decommissioning and dismantling of nuclear installations MonoCEA GB 5/04/06 15:30 Page 25

Decommissioning-dismantling feedback

Numerous nuclear installations have already been success- fully decommissioned and dismantled. Here is the list of instal- lations dismantled or in the process of dismantling in France:

•Power reactors - The Monts d’Arrée power plant (EL4). - Natural uranium graphite gas (NUGG) system reactors. - The Chooz A D reactor (Ardennes ). - The Superphénix reactor. he EDF media library/Antoine GONIN. ©T • Research reactors Fig. 25. Cutting an auxiliary boiler in a ventilated flame resistant suit. Dismantling of the Brennilis’ EL4 power plant. - The reactor. - The Harmonie reactor. - The Mélusine and Siloé reactor. - The Strasbourg University reactor.

Dismantling waste • CEA laboratories and workshops The dismantling of nuclear installations produces a large quan- - The AT1 pilot reprocessing workshop. tity of waste, mainly of low level. The European Commission - The caesium 137 and strontium 90 source manufactur- estimates that the decommissioning of an “average” nuclear ing workshop (ELAN IIB). power plant produces up to 10,000 m3 of radioactive waste. - The enriched uranium reprocessing workshops (ATUE). Concrete and other construction materials only containing a - The fuel assembly cutting laboratory (LDAC). very low radioactivity represent, in volume, the main part of - The plutonium chemistry laboratory (LCPu). this waste. - The plutonium based fuel laboratory. - The Saturne accelerator. The effective management and evacuation of radioactive - The Saclay linear accelerator (ALS). waste is an essential condition of the success of the D-D of nuclear installations and represents the main part of the over- all cost (in the order of 60%, or installations together, accord- • The other installations ing to a German estimate). - The FBFC plant at Pierrelatte. - The irradiator of the Société normande de conserve et The large quantity of dismantling waste containing only very stérilisation (SNCS). small concentrations of radionuclides requires special care in the reduction to the minimum of the constraints linked to their The assessment of the operations carried out show that until evacuation as radioactive waste. This leads to “waste zoning” now, only small research reactors have been the subject of a of the installation being carefully carried out, by accurately total dismantling with complete deconstruction of the build- defining the border between conventional waste areas and ings. Medium-sized reactors (G1, G2, G3, EL3, Rapsodie) radioactive waste areas. have only been subjected to partial dismantling, due to the absence of associated waste (graphite, sodium) disposal sys- Dismantling waste currently has, in France, a specific disposal tems. Several laboratories, workshops or pilot plants have centre (VLL centre, Very Low Level) in Morvilliers. been completely dismantled. Finally, an ore reprocessing installation, which produced almost 10,000 tonnes of uranium in metal and oxide form, as well as *, was completely dismantled.

The analysis of these operations leads to the observation that the dismantling of reactors and fuel manufacturing installations (hot cells and plutonium laboratories) is considerably shorter than that of installations involving chemistry (ore processing, reprocessing) and contaminated by fission products. It has

Nuclear energy of the future: 25 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 26

been noted on the operations carried out that the volumes of waste generated, of a few hundreds to several thousands of m3, can be properly managed.

Dismantlings in progress at CEA are good examples. The experience which will thus be acquired on small or medium- sized installations will certainly be very useful for the disman- tling of large nuclear power plants or certain plants of the front or back-end of the civilian nuclear cycle. MonoCEA GB 5/04/06 15:30 Page 27

Nuclear safety and security

Nuclear power and environment The design, construction and operation of nuclear installa- tions must take account of the safety requirements, and their Radioactivity is found throughout the environment. But most impact on Mankind and the Environment must be controlled. of this radioactivity is of natural origin. It comes from cosmic It is an essential link for the public’s acceptance of nuclear rays, radon* from minerals from the earth and exhaled into energy. the air that we breath, terrestrial radiation coming from the iso- topes from the uranium and thorium chains present in the ground, and carbon 14 and potassium 40 present in our organ- The risks associated with nuclear ism and in our food. However, we also find in certain compart- power are perceived by the public ments of the environment, artificial radioactive isotopes, orig- as important inating from the atmospheric nuclear tests carried out during the Cold War, fallout from Chernobyl, and finally, for a very The acceptance of the nuclear risk poses a problem for soci- small part, from industrial nuclear activities. ety. In the medical field, the risk is accepted because it is bal- anced with estimated benefits. This is rarely the case when In normal operation, the environmental impact of nuclear one becomes interested in energy production. That said, the installations is low: power plant emissions (tritium) are barely 3 French Académie nationale de médecine observed that “the detectable (and yet, we know how to detect radioactivity at most serious health risk is a lack of energy (link between very low levels, but natural radioactivity easily masks the health status and energy expenditure in developing countries, human induced contribution); emissions from the La Hague health consequences from supply shortages, etc.)” and rec- reprocessing plant are much higher and much easier to detect4 ommends “maintaining the nuclear system in so far as it (iodine 129 and tritium are discharged into the sea, krypton proves to have the lowest impact per kWh produced in rela- and tritium into the atmosphere).They also include a chemical tion to the systems using fossil fuels, biomasses or the incin- discharge element (nitrates, marginal compared to the “agri- eration* of waste, or even when it is compared to wind and cultural” contribution). However, the effects of dilutions and dis- photovoltaic energies”. persion in marine or atmospheric environments render the radioactive contribution from the plant insignificant compared The comparison of factual data between nuclear risks, other to the natural contribution a few kilometres away from the industrial risks, risks arising from other human activities (trans- installation. port, tobacco, etc.), natural risks, etc. is instructive. But con- cerns regarding accidents, long lived waste and the impact on All radionuclides do not behave in the same way.Their behav- future generations cannot simply be dissipated.The perception iour depends on their chemical properties. In most cases, a of risks is eminently subjective; those that result from choice dispersion and dilution of the contaminants is observed. In oth- (e.g. rock-climbing), and those which result from equipment ers, conversely, a concentration in certain compartments of imposed by the community (nuclear power plants) are not per- the biosphere is observed. Reconcentration phenomena may ceived in the same way. be of biological origin (case of caesium in mushrooms) or have any physical or chemical cause (contamination* marks The acceptance of nuclear power by the society passes in any observed in Mercantour are caused by runoff phenomena). case by a permanent communication and transparency effort (in particular regarding accidents and incidents), and by the independence of a strong supervisory authority for operators.

4. The La Hague reprocessing plant discharged in 1997 approximately 12,000 terabecquerels (Tera = x 1012, ie multiplied by a million of millions) 3. Report concluding a colloquium held on June 25th, 2003 on the rela- in the form of liquid waste (11,900 TBq of tritium and 1.8 TBq of iodine 129) tionship between health and the energy choices. and 300,000 terabecquerels in gaseous form (mainly krypton 85).

Nuclear energy of the future: 27 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 28

(decree of March 2001) for public expo- Atmospheric sure. As a guide, the average natural fallouts Atmosphere Inhalation (aerosols) irradiation is 2.5 mSv/year, but it is nec- essary to specify that the abovemen-

External tioned dose limits concern doses in exposure Rain addition to human activity.

Gaseous Bathing – emissions Water sports In comparison to natural doses, the Ingestion Rain Milk dosimetric impact of nuclear installa- Foliage Plantations tions is low. A nuclear power plant dis- Drinking water charges into the environment ten times Ingestion Ground deposit Stream Watering less radioactivity than a coal or fuel Infiltrations power plant of the same power: the col- Toward drinking water Fish lective dose is between 1.6 and 2.6 Algae Shellfish man-sievert per gigawatt-year for a Liquid effluents Sediment nuclear power plant, compared to 20 for Ground waters a coal power plant. The impact of cycle plants (reprocessing, mines) is much Atmospheric diffusion Hydrological/ Marine diffusion greater: according to the last report transfers hydrogeological diffusion transfers transfers from the Nord-Cotentin Commission, the dose induced by discharges from Fig. 26. The analysis of the transfer of radioactive contaminants into the La Hague plant on the most the biosphere is the subject of radioecology*. Different compart- exposed population is 0.06 milliSievert per year, that is 20 ments of the biosphere are considered: soils, lakes, rivers, atmos- phere, plants, animals and humans. times less than the dose caused by natural radioactivity.

If the effect of high doses resulting from serious accidental sit- Nuclear power and health risks uations is well-known, the problem of low doses of radiation remains a subject of biological and medical research (relation- We are all exposed to natural radioactivity, and the effects of ship between the risk and the dose, threshold effect), with an radioactivity on the organism are no different depending on epidemiological section. The same goes for the hereditary whether the radioactivity is of natural or artificial origin. effects of radiation.

The control of the exposure to radiation is the subject of radi- ation protection. Current French regulation imposes a dose* limit of 20 milliSievert (mSv)* over 12 consecutive months (decree of March 2003) for worker exposure, and 1 mSv/year

Scale of risk relating to effective annual dose Major health risk

Medical origin (diagnostic needs) Artificial origin Aerial tests + 1000 mSv/year 400 AND Chernobyl Nuclear industry Reminder: Significant 20 mSv workers’ limit health risk Nuclear tests (0,08) Chernobyl (0,002) 1 mSv public limit Medical origin (0,4) Nuclear industry (0,0002) + 100 mSv/year 40 AND

Low health risk Cosmic rays (0,4) + 20 mSv/year Range of natural 10 mSv/year + 10 mSv/year 4 AND Terrestrial exposure Ingestion (0,3) gamma rays the most Insignificant (0,5) often Inhalation (1,2) AND* 2,5 mSv/year health risk encountered 1 mSv/year -1 mSv/year External Cosmic rays zero or practically Normal no health risk Natural exposure Terrestrial gamma rays situation -µSv/year origin Internal Inhalation (mainly radon) *AND = average natural dose

exposure Ingestion Source: Clefs CEA, n° toxicology”. “Chemical and radiological 48, summer 2003,

Source: UNSCEAR 2000 Fig. 28. Scale corresponding to the levels of exposure and health Fig. 27. Components of the annual radioactive dose (in mSv). effects.

28 Nuclear safety and security MonoCEA GB 5/04/06 15:30 Page 29

Safety and demonstration of safety low-up of actions, equipment or procedures, grouped in levels each one of which has the purpose of pre-empting degrada- In the nuclear industry as in any human activity, zero risk does tions likely to lead to the next level and to limiting the conse- not exist. The objectives of the safety procedure is therefore quences of the failure of the preceding level) in relation to not to entirely eliminate the risks associated with nuclear activ- aggressions that may affect the safety functions. This is gen- ities. In a less ambitious but more realistic way, it is to pre-empt erally assured by the redundancy and the diversity of barriers the risks of accident, and to mitigate their consequences in the (successive and leaktight multiple-barrier system). Several hypothesis where the accident would nevertheless occur.The means of stopping the chain reaction, redundant and diversi- notion of safety is taken into account very early on, as of the fied residual power evacuation systems, several barriers installations’ design phase.The specificity of the nuclear indus- between the radioactive products and the environment, thus try arises from the use of radioactive materials, which are likely exist. It is endeavoured to make these various means as inde- to be dispersed into the environment or even to affect the pendent as possible from one another, and to plan for each of human being, and which are at the origin of ionising radiations them permanent or periodical monitoring used to guarantee with multiple effects (irradiation, thermal energy, radiolysis, their availability. etc.).

Risk analysis is the subject of a Containment conventional procedure: (3rd barrier) •Technical analysis of the instal- lation’s safety and reliability; Sprinkling •Evaluation of the risks linked to device

the dispersion of radioactive or Sand filter Control chemical materials (impact on bars Pressurizer mankind and the environ- Steam ment), and to the exposure of generator workers and the public to radi- ation (this is the entire field of radiation protection); Primary • Risk management, comprizing circuit both compliancy with the regu- (2nd barrier) lations relating to radiation pro- tection and the development of Vessel nd decontamination processes for (2 barrier) Core – fuel soils and sites contaminated (cladding: following an accident. 1st barrier) Pump

French regulation mainly The three safety functions for reactors requires deterministic calcula- • Control of the chain reaction tions (incidents or accidents are •Evacuation at any moment of the energy produced in the core, production postulated). With the safety which continues at the level of a few % after stopping the chain reaction (we objectives defined, possible fail- then speak of residual power). • Containment of radioactivity, the main part of this relating to the fission prod- ures are imagined, which may ucts formed in the fuel. be of external or internal origin, (earthquake, fire, power cut, Fig. 29. The three containment barriers of a PWR. pump shutdown, etc.), the behaviour of the installation is simulated, and it is made sure that the consequences are Increasingly, this approach is completed by a probabilistic acceptable. All of the difficulty resides in the exhaustiveness safety assessment (PSA), which aims to evaluate the prob- of the list of scenarios envisaged. A set of principles, concepts ability of the barriers’ destruction, the associated radioactive and methods has been developed, both at the design stage, waste and the consequences on the surrounding population. and at the construction or operation stage. Thus defence in- Here we come up against the difficulty of assessing the prob- depth* consists of interposing several “lines of defence” (fol- ability of extremely rare events. Thanks to the probabilistic safety studies carried out in the years which followed the Three Mile Island (United States) accident, operators have made pro- visions having effectively reduced the probability of a core melting* accident by factor 10 to 100.

Nuclear energy of the future: 29 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 30

Another point of view is the acknowledgment of the human Risks linked to nuclear proliferation factor as a progress point of safety, and this from the design stage up to the dismantling, cleanup and waste management The issue consists of developing civil uses of nuclear energy, phases of nuclear installations.The analysis of significant inci- without thereby lessening the world’s safety by enabling cer- dents and accidents shows, in effect, that a significant part of tain countries or organisations to equip themselves more eas- 7 errors likely to have an impact on the safety of the installations ily with nuclear weapons . The corresponding risks must be is linked to activities other than the conduct in control rooms examined from two angles… (maintenance, tests, loading operations). The technical means that can be used INES gravity scale to acquire fissile material needed for the construction of a bomb The easiest means of acquiring the necessary material for 7. Major Accidents constructing a bomb is the enrichment of uranium. A shortcut (Chernobyl type ) consists of recovering highly enriched uranium used in fuels for 6. Accidents having limited consequences around the site research reactors: this is why the Americans have decided to 5. Accidents presenting risks outside place an embargo on fuel enriched by more than 20%, a rule of the site (T.M.I. type) generally applied today (there are however a few exceptions). 4. Accidents on the installations A more difficult means is that implemented by the United (Tokaï Mura type) Kingdom and France in the 1950s: to produce plutonium in 3. Incidents affecting safety reactors “burning” natural uranium at very low irradiation lev- 2. Incidents likely to develop later els, enabling military quality plutonium to be produced. The 1. Operating anomaly extraction of plutonium requires complex reprocessing instal- lations. Large power reactors using enriched uranium are poorly suited to the production of military plutonium, because it would be necessary to very greatly limit the irradiation of the Fig. 30. The INES gravity scale* of nuclear incidents or accidents. fuel and to reprocess it. This would not be impossible, but this Between 1995 and 2005, the French electro-nuclear fleet was the would be a large-scale, very expensive and difficult to hide subject of thousands of level 1 incident declarations, of approximately operation. forty level 2 incidents, and no higher level incident or accident.

The technical means and control policies Feedback constitutes a major element in the progression of The keystone of the battle against nuclear proliferation is the the nuclear installation safety culture. The systematic record- Non-Proliferation Treaty (NPT), signed by most countries (but ing and analysis of incidents, and all the more so, of accidents not all). The signatory countries commit to accepting control (Three Mile Island, Chernobyl, Tokaï-Mura5) must enable the by the International Atomic Energy Agency of their nuclear operation and the safety to be improved. But serious accidents installations and fissile materials in their possession (only 5 are generally and fortunately few, which does not enable them permanent members of the UN Security Council8, who already to be analyzed reliably by the existing mathematical tools. It is had nuclear weapons in 1968, maintain the right to not submit therefore important to pay attention to incidents as well as to their military programmes to international control). The con- near incidents, defined as events which could have led to an trols led by the IAEA are without a doubt difficult when they accident, or even to events in which human intervention has concern small installations such as small uranium enrichment enabled a potential incident to be caught in time. Equally units. On the other hand, they are effective for large fuel repro- nuclear operators have undertaken to exchange their best cessing installations and power reactors. More worrying is the practices and to inform each other regarding any significant case of countries who have not signed the NPT or who decide incident, within the World Association of Nuclear Operators to leave it. But the corresponding risks of proliferation are not (WANO); the safety authorities of various countries have also directly linked to the civilian use of nuclear energy. The few established close relationships which were lacking prior to the countries which have developed their own nuclear weapons ; and the IAEA6 has had adopted by all of have moreover done it via specific means, and not by hijack- the nuclear countries a set of common safety rules and prin- ing civilian installations. ciples. 7. Only the risks of nuclear weapon proliferation are mentioned here. “Dirty” bombs, associating radionuclides with a chemical explosive, pres- ent very real risks, but it would be infinitely easier for terrorists to seize 5. Three Mile Island (USA), the 28th of March 1979; Chernobyl (ex-USSR), industrial or medical radioactive sources, currently used and less pro- the 26th of April 1986; Tokaï Mura (Japan), the 30th of September 1999 tected than fissile materials from the nuclear industry. (Note of the Editor). 8. Representing the United Kingdom, United States of America, France, 6. International Agency for Atomic Energy. China and Russia (Note of the Editor).

30 Nuclear safety and security MonoCEA GB 5/04/06 15:30 Page 31

Risks linked to terrorist attacks • The beginning of disposal coincides with the beginning of the second period, when it is no longer necessary to cool the This subject is frequently talked about, more particularly since waste. The radioactivity of fission products decreases to a the 11 September 2001 attacks. Generally, nuclear installa- low value, and it is the actinides present (neptunium, ameri- tions figure among the international installations which are the cium and in the glass, neptunium, americium, curium best protected against terrorist risks, due to both their mas- and plutonium in the spent fuel) which release the heat.This sive and stocky character, and the in-depth defence provisions release determines the dimensions, both of the waste pack- mentioned above. ages (the thermal load of each package being limited) and of the disposal site (the thermal load per unit of surface Risks linked to the transportation area being limited).

of nuclear materials •In the third period, which lasts several tens of thousands of Nuclear materials are subjected to many transformations: con- years, even 100,000 years, the main part of the radiotoxicity version, enrichment, manufacturing of fuel, irradiation in reac- inventory of waste comes from minor actinides* (for the tors, reprocessing, etc., all operations generally carried out in main part, in glass, neptunium and, at the beginning of this different locations, which require a great deal of transporta- period, americium and curium) and plutonium when the lat- tion*, by rail, road, air or sea. ter is incorporated into it (case of spent fuel). The potential radiotoxicity* of waste only becomes lower than that of the Approximately 300,000 radioactive material packages are original uranium ore towards the end of this period. In transported each year in France for the requirements of indus- between, the safety of a geological disposal site must be try, the medical sector and scientific research, which repre- assured above all via the containment of the waste placed in sents less than 2% of all dangerous material packages trans- disposal containers, themselves surrounded by engineered ported. barriers; the geological barrier only intervenes in the case of failure of the latter. The work in progress on the containers, The tonnages to be transported are low, which does not the engineered barriers and in underground laboratories exempt us from taking precautions in order to limit the risk of aims to validate the safety analyses relating to this period. dissemination of radioactivity during these transportations. There are four types of risks linked to transportation: irradia- •Beyond 100,000 to 200,000 years, the safety analysis con- tion, contamination, criticality concerning the protection of siders that close containment is lost and that it is therefore people, property and the environment, theft or hijacking con- the geological barrier which plays the main role of protection. cerning the safety of materials. A large number of behaviour models over a very long term of these radionuclides, carried out in various countries and An important part of the precautions concerns the robustness compared in international programmes, have concluded that of the containers. No major accident due to transportation is to the doses received by man would amount to low fractions of be deplored from the beginning of the nuclear era. those attributable to natural radioactivity.

During the first two periods, the problems posed will mainly be Risks linked to the disposal national. They concern the security and safety of the storage of nuclear waste or the passive safety of the disposal.

Attention has been focused for a decade on the risks linked to Over a longer term, the accumulation of radionuclides in the storage (temporary by definition) and to the disposal (perma- disposal sites, however, should be considered as a legacy to nent or reversible) of high level and (or) long lived nuclear the planet’s future generations9. The waste-related environ- waste. mental risk may be considerable if it is badly managed (exam- ple of certain former Soviet sites such as Chelyabinsk). If they Technically, four periods are to be considered: are well-managed, the impact of the waste will probably be minimal, local and delayed. No demonstration of safety could •For several decades (a century in the case of the storage of ever be provided directly, due to the time scales at stake. The MOX spent fuel), nuclear waste is characterized by a very role of science must probably be a little more modest: build high level of radioactivity originating from both relatively short lived fission products and actinides (curium in glass, curium

and plutonium 241 in spent fuel). In parallel, there is a heat 9. Final nuclear waste stored in well selected locations and carbon gas release which requires cooling; here we are in the field of emissions should not be placed on the same level. For nuclear waste the industrial techniques currently used in the storage of high risks will remain local because they would only concern at any moment the geographical neighbourhood of the disposal site, therefore in any case level waste. only a limited number of people, whereas carbon gas emissions are not controlled and their effects concern the planet’s overall climate.

Nuclear energy of the future: 31 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 32

confidence, via a corroborating stream of indications showing that all of the mishaps likely to affect the disposal have been envisaged including their consequences, etc. In short, that the latter is a robust and controlled design.

Building confidence

Controlling risks is not only technical and scientific: it also has a strong social component.The confidence building procedure must not stop once the conviction of experts is acquired. It is then necessary to pass from scientific uncertainty to the nego- tiation of the risk. Nuclear safety calls on political decisions made democratically, that is with the opinion of citizens, whose intellectual logic is different from that of scientists. Scientists and citizens have a lot to say to each other! MonoCEA GB 5/04/06 15:30 Page 33

Energy in the world

have to compete with synthetic fuels manufactured from coal, Since the discovery of fire, human development has been the reserves of which are still significant.The use of hydrogen accompanied by increased energy consumption. Still today the alone, without passing by a fuel cell is also a channel which level of energy consumption in general, electricity consumption must not be neglected, for land vehicles but also air or mar- in particular, are indicators – fairly rough – of development. itime vehicles.

A particular form of energy: electricity Toe / year 9 Electricity occupies a growing part in the energy consump- Transport tion of all of the developed countries, due to its privileged use 8 in the lighting, information and communication fields, and Industriy + agriculture 7 thanks to specific advantages linked to its flexibility of use in 6 Domestique + tertiaire engines and switches. Electricity is a clean energy in the phases of transportation, distribution, and end use: no pollu- 5 Food tion, and no greenhouse gases, with the exception of ozone. 4 It is also clean in the production phase, if it is produced via 3 nuclear, hydraulic, solar or wind power. 2 Apart from these advantages, electricity has a significant 1 weakness: it can practically not be stored, except in minimal 0 quantities and at a high costs in accumulators. It can be stored indirectly (pumping stations, flywheels), but this remains mar- th century th century Prehistory Antiquity XVIII XX United-Statesth century ginal. Therefore it is necessary to produce it at any moment XX - 30 000 years according to the immediate demand: the absolute example of - 2 700 / - 1700 years “tight flow”! Fig. 31. The various uses of energy, during the ages, expressed in “tonne of oil equivalent” (toe) per year and per person. The consequence of the difficulty of storing electricity: if the net- work is powered by an intermittent and random source, which is the case of many renewable energies, it is necessary to plan in reserve an equivalent power source ready to replace it. Energy use

The habitat represents approximately a third of the human The international consumption energy consumption. This sector is likely to progress a great deal: the massive use of thermal solar energy would enable of primary energy production of a large part of hot running water and residential It is fairly certain that energy consumption will increase in the and service sector heating. Unfortunately, the very slow rate of next fifty years due to the increase in the world population and habitat renewal is slowing down the progress which might be the increase in the standard of living in developing countries. carried out in this energy sector. Fossil fuels (coal, oil and gas) will still be dominant. The pro- duction of oil should, between now and around ten to twenty Transportation represents a large part of the global energy years, first peak then decrease. As requirements are increas- consumption, and a major source of pollution. In this sector, ing, the question will be to know how to fill this lack by more liquid hydrocarbons seem difficult to replace in the short term, environmentally friendly energy sources. The problem is not even though hybrid vehicles, combining a thermal engine and to oppose energy sources, but to find the best use for each an electric engine powered by batteries, have already started one of them in order to reach the most effective energy mix. to see the day fairly quickly. Hydrogen and fuel cells will reach their full potential probably in a more distant future and will

Nuclear energy of the future: 33 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 34

Units This average of 2.3 toe/year per person hides a very large regional disparity, which reflects the great North-South divi- It is important to specify at which stage of use energy is sion in terms of development: whereas an American con- counted. When the assessment is made at source (coal mine, sumes 8 toe every year, a European or a Japanese person oil well, hydraulic dam, etc.) we speak of primary energy, makes do with 4 toe, and an Indian citizen lives with only 0.4 which is what we will do in the rest of this text. Useful or final toe per year. energy can also be counted. Due to the yields from transforma- tion and various losses, almost three times more primary energy is needed than useful energy, directly linked to the service sought. Energy consumption per inhabitant (TOE) When we talk about the energy consumption of the country, we generally count it in tonne oil equivalent (toe). India 0,2 Approximately, 1 tonne of coal equals 0.667 toe and 1 MWh of China 0,7 gas equals 0.077 toe. Emerging countries 0,8

Things become complicated when it involves expressing in toe World 1,6 the energy produced by a “primary” electricity source, which Japan 3,9 does not come from the conversion of a fossil fuel (hydraulic, France 4,0 nuclear, wind electricity, etc.). In 2002, France rallied to the Germany 4,1 International Energy Agency conventions: EU 3,8 • The nuclear (or geothermal) MWh “equals” 0.26 toe, quan- United States 8,1

tity of oil that it would be necessary to burn to produce one 0 246810 MWh in a thermal power plant.

Fig. 33. Can these inequalities last?

Today, the Earth’s inhabitants consume on average 2.3 toe per person each year, which leads to a cumulated annual Distribution per source consumption of primary energy, all sources together, of 9 bil- lion toe, 9 Gtoe/year. The table below provides the distribution of the world energy consumption between the various primary sources, in 2000, according to the International Energy Agency:

Gtoe / year Source Million toe % 50 World population in billions 12 A Solid fuel 2,341 25.7 10 Oil 3,700 40.7 40 8

6 Gas 2,100 23.1 B 30 4 Nuclear 676 7.4 2 Hydroelectric 226 2.5 0 C New Renewable Energies (NRE) 51 0.6 20 1850 1900 1950 2000 2050 2100 Total (commercial) 9,015 100

10

Coal 0 1850 1900 1950 2000 2050 2100 Oil

A: Steady growth Gas B: Average growth C: Eco-friendly growth

Source: 1998. “Global Energy Perspectives”, Etude IIASA/WEC Nuclear Fig. 32. The world’s population approached half a billion individuals Hydroelectric at the beginning of the christian era. It reached a billion towards the th middle of the 19 century then, by a fantastic acceleration of demog- NRE raphy, the current figure of 6 billion in only 150 years. The world population is now increasing at a more moderate rate, but, at the present rate, we will without a doubt reach 10 billion during this Fig. 34. The world energy consumption between the various primary century. sources.

34 Energy in the world MonoCEA GB 5/04/06 15:30 Page 35

It can be seen that fossil fuels amount to 90% of the commer- The rate of discovering new exploitable oil fields has cial primary energy used on the planet, and still over 80% if decreased since the 60s, which implies a rapid exhaustion of non-commercial energy is taken into account. The figures conventional resources if the current rate of consumption is speak for themselves: there is no way that the increase in the maintained. contribution of new renewable energies (NRE) can alone cover the increase in requirements – or replace nuclear power as Thanks to new discoveries and also a better recovery of oil on wished by certain people. In any case, not in the decades to site, it should be possible to exploit much larger resources.The come. latter will nevertheless be much more expensive than those recovered today. By lowering the costs, technical progress Even if the OECD countries made spectacular strides in should enable the development of deep sea production and increasing energy efficiency, the requirements of developing the exploitation of very deep deposits. Beyond that, the countries are such that the energy consumption could not resources in non-conventional oil, and in particular, the extra increase less quickly than the population itself. All the more heavy crudes, asphaltic sands and kerogen shale are consid- because the OECD countries and those of the former USSR erable. have now stabilized, and the 4 billion human beings which will increase the world population during this century will originate Natural gas from current developing countries. In order to face these gigan- tic requirements, we will not have too much of all of the The proportion of natural gas in the world’s energy inventory energy sources that mankind knows how to master! continues to increase, given its advantages: lower impact on the environment than coal or oil (no dust, better efficiency for the generation of electricity with combined cycles, turbines, Fossil energies etc.), its flexibility of use, the importance of its reserves greater than that of oil (it currently represents more than 60 years of The proportion of fossil energies should remain largely pre- consumption at the current rate). There are also considerable ponderant in future decades. It should represent, according to reserves of methane hydrates (without a doubt more than dou- the International Energy Agency, 90% of the commercial ble the quantities of fossil fuels which are yet to be exploited) energy supply by 2030, hydrocarbons (oil and gas) represent- that are trapped at the bottom of the sea or permanently in ing approximately 65%. frozen ground. We still however do not know how to recover the latter technically. There are also uncertainties regarding Oil the energy efficiency and the economic cost of this recovery. The proven reserves of oil currently represent approximately around forty years of production at its current rate of consump- Coal tion. Coal, after a period of decline, may return in force, given the importance of its reserves, which represent several centuries of consumption at the current rate, in particular by implement- ing gasification systems, which enable it to be used in a cleaner way. A good illustration of this is the “Futuregen” proj- ect, which was started in the United States of America in order to lead to the industrial demonstration of a system of electric- Annual discover ity production from “clean coal” with sequestering of CO2. Burgan Ghawar Smooth on 5 years Zuana Production

Gach Saran Tia Juana

Fig. 35. The rate of discovery of new exploitable oil fields has decreased since the 60s, which implies a rapid exhaustion of con- ventional resources if the current rate of consumption is maintained.

Nuclear energy of the future: 35 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 36

Fossil energies, CO2 and climate The relative contribution change of the various sources of electricity

In the future, we must be able to answer to two major ques- to the production of Greenhouse tions: how to best manage the finite reserves of fossil fuels and Gases (GHG) how, moreover, to respond to the risks of climate change, by Among the various figures of the literature, here are the results restricting greenhouse gas emissions.The increase in the con- from the LCA (Life Cycle Analysis, ISO 14040 standard) car- tent of these gases in the atmosphere is due, without doubt, ried out by EDF, in CO2 gram equivalent per electric kilowatt to human activities, and mainly to the use of fossil fuels, coal, hour: oil and gas. If the phenomenon is not controlled very quickly, the global climate of the planet will be affected for a long time, System Operation Remaining Total with potentially catastrophic effects. life cycle g/kWhe Coal 600 MWe 892 111 1003 Fuel-oil 839 149 988 Gas (turbine combustion) 844 68 912 Past and future concentrations of CO2 in the atmosphere Diesel 726 159 895

Projections Hydraulic pumping 127 5 132 Direct measurements ppm Ice core data Photovoltaic/solar 0 97 97 1000 1000 Hydroelectric 0 5 5 900 900

800 800 Nuclear 0 5 5

700 700 Wind 0 3 3

600 600

500 500

400 400 As seen, it is not entirely true to say that nuclear, hydraulic or

300 300 wind power does not produce any greenhouse gases,

200 200 because the construction of power plants, dams or windmills

100 100 requires concrete and steel, the production of which itself releases GHGs. But their contribution remains truly marginal! 0 0 1000 1200 1400 1600 1800 2000 2100

st Fig. 36. The concentrations of CO2 expected during the 21 century Renewable energies are two to four times that of the pre-industrial era. The history of humanity is dominated by the use of renewable energy, because the latter started to be used when humans

The sequestering of CO2 is an actively pursued avenue of discovered fire, approximately 500,000 years ago. Renewable research. The options which seem to be the most interesting resources are immense; the most abundant, solar radiation, 17 are those which consist of storing CO2 in exhausted hydrocar- represents 7.2 10 kWh annually, that is to say more than bon deposits or in deep aquifers10.Work is yet to be carried out 5,000 times the entire global consumption of primary energy. in order to reduce the costs, which are currently in the order of But these resources are generally intermittent and many € 50-100 per tonne of CO2 avoided, and to ensure the long- require disposal in order to respond to the demand of modern term security and longevity of the disposal site. Various societies, where the consumer wants energy when and where demonstration projects are in progress or planned (Sleipner, he needs it and not when it is available. The biomass and the Weyburn, In Salah, etc. deposit). Importance R&D pro- accumulation of water in reservoirs represents an energy stor- grammes have also been undertaken, in particular on the age which improves availability, and geothermy diffuses a heat

European level. However the capture and disposal of CO2 may flux fairly continuously. only provide a partial response to the problem posed: indeed, this solution can only currently be envisaged in large scale In comparison to modern resources, often highly concen- static systems, which excludes it from the transportation and trated, renewable resources have the disadvantage of a low habitat sectors which represent a very large part of the emis- density; therefore they must rather be transformed there where sions. A possible way out would be a large-scale use of hydro- nature delivers them. Finally, even though the resource is free,

gen produced without CO2 emission, but this cannot be envis- the cost of many renewables is still too high in relation to other aged in the short-term. energy sources.This is mainly due to the additional investment costs for conversion systems.These additional costs resulting either from the too low density of energy, or from the market 10. Permeable rocks with a high water content (Note of the Editor). which is still too little developed, or from the technology which

36 Energy in the world MonoCEA GB 5/04/06 15:30 Page 37

has not yet reached its asymptote of minimal cost. The limita- The short and medium-term avenues are energy savings, the tion of non-renewable resources and their impact on the envi- replacement of coal by natural gas, the development of renew- ronment results in renewable energies experiencing increased able energies, and, last but not least, that of nuclear power. interest. But, at this moment in time, hydraulics for producing electricity, and biomass for producing heat, easily dominate The field of energy is a coveted field, the country which will the renewable energies market, thanks to their competitive find and develop good technologies will reap an enormous cost. They alone represent almost 20% of the primary competitive edge. It is therefore important that Europe be in resources exploited. the race for the highest international level of innovation.

A European political intent has led to supporting the mecha- nism of restricting greenhouse gas emissions; the Kyoto pro- tocol is the first step towards this. One of the aspects of this intent is secured Electricity production in Europe (in 2000) per country and per source by the European directive of the 27 September 2001. The latter specifies Billions of Kwh (gross) Billions of Kwh (gross) that the generation of electricity from 2550 renewable sources must pass from 600 13% to 22% in Europe in 2010, from 2 000 15% to 21% in France. 500

400 The energy challenge 300 The 20th century has bequeathed us a 1 000 double challenge in the field of energy: 200

•To confront the energy requirements 100 of a world population multiplied by 10 between 1750 and 2050, consuming 10 times more per inhabitant; DBEFU-K NL I S Total European Union •To control local, regional and plane- Nuclear Hydroelectric Wind Coal Gas Fuel tary pollution (climate).

It has left us the means, but mobilisa- Fig. 37. An illustration of the disparity of electric energy sources in various European countries. tion must be complete in order to rise to these challenges.

Although the increase in requirements and the aggravation of risks originates from poor countries, rich countries can and Denmark must provide their contribution: controlling energy, technology transfer, reduction of their GHG emissions. United-States

Germany The answers to be provided are not necessarily the same in every country because priorities depend on the state of UK development, the domestic resources, financial capabil- ities and the cultural context, but the challenge is to be met Japan

on a global scale because the effects on the environment are Sweden global. France

0 100 200 300

Fig. 38. The choice of energies: CO2 emissions per kWh throughout the world (gC/kWh).

Nuclear energy of the future: 37 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 38 MonoCEA GB 5/04/06 15:30 Page 39

The economy of nuclear power

The cost per kWh produced by high power water nuclear man/year for wind turbines). As its French counterpart, the reactors has been the subject of numerous studies, the most Finnish study gives the advantage to nuclear power. complete of which are probably those conducted by the French Ministry of Industry, which is based on a very important and Between 1974 and 1985, in France in particular, nuclear power well-known programme, and that carried out by the Professor enjoyed a comfortable margin of competitiveness. Then, the Tarjanne for the Finnish government and which supported its oil counter-shock very rapidly brought the price of fossil ener- recent decision to build a new reactor. gies back down to the level that they were prior to 1974, and this situation lasted until 1998, profoundly changing outlook. The DGEMP study notes that all of the nuclear power costs On the other hand, gas turbines, benefiting from technologi- are in fact taken into account, contrary to that which occurs for cal effects from the aeronautical industry, achieved spectacu- other energies: in particular the provisions for waste manage- lar progress in efficiency, unit size and thus price, whereas the ment and for the dismantling of installations.This overall cost strengthening of safety and the increase in regulations has is evaluated at approximately € 30/MWh, of the same order of somewhat increased the nuclear investment. magnitude as the internal cost of the kWh in a combined cycle gas power plant. Since 2003, the scale has once again tipped in favour of nuclear power and this trend should last and be accentuated The Finnish study compares the costs of the kWh of a 1,250 with the inexorable rise in the price of hydrocarbons, accom- MW nuclear power plant and those of fossil fuel and wind panied by the progressive growing scarcity of resources. power plants, with the conventional hypotheses regarding the lifetime of the power plants (40 years) and the availability of The evaluation of the competitiveness of nuclear energy must the installations (90% for thermal power plants, 2,200 be made over a long time period, comparable to the lifetime of nuclear plants. The comparison depends on the price per- formance of other primary energies during this time period. Cost of electricity generation For hydrocarbons, this evaluation is very uncertain.

60 Euro / MWh 50.1 What is certain is that the nuclear power costs are stable and 50 predictable.The price of uranium raw material only intervenes 39.6 10.0 for a very small part in the price of the nuclear kWh.This favor- 40 32.5 able situation protects nuclear energy from fluctuations in the 32.1 30.5 30 18.4 raw materials market. Moreover, 90% of the expenditure takes 22.8 24.1 15.8 place on the national territory, with the location corresponding 17.1 20 3.0 40.1 23.7 to the use, and with favorable consequences on the balance 7.2 8.2 6.5 of payments. 10 7.4 13.8 1.5 10.2 13.0 7.6 5.3 0 Today, existing nuclear power plants, partly amortized, consti- ELSPOT ELSPOT Nuclear Coal Gas Peat Wood Wind tute important sources of profit.

Price Price Generation cost excluding subsidies max 2000 maxi. 2001 and tax benefits On the other hand, the initial investment necessary for con- Fuel Maintenance Cost of the structing new ones is high and difficult to assemble. It will prob- and operation capital ably be necessary to resort to new financing structures in order Price in November 2001 - Interest rate = 5.0 % to finance such heavy investments in a largely deregulated Fig. 39. Cost of electricity (€/MWh) for various sources of primary economy focussed on the short-term. Evidence of feasibility energy, compared to the ELSPOT price, the Scandinavian kilowatt- is starting to emerge: for example, a consortium of Finnish hour market. The Finnish study from March 2002 concludes that paper manufacturers is financing one part of the new PWR nuclear power is the most economical energy source when power plants operate more than 6,000 hours per year. Only the internal reactor recently ordered in this country.These credit arrange- costs have been taken into account. A possible eco-tax on carbon ments must take account of the fact that the heavy investments would further improve the competitiveness of nuclear power. of the nuclear power industry, combined long-term with the

Nuclear energy of the future: 39 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 40

return on investment, makes the profitability of nuclear power €/MWh particularly sensitive to the interest rate for necessary loans. 60 53 50 46 Nuclear Gas combined Wind cycle 40 Real interest rate 5% 24.1 30.5 50 30

Real interest rate 8% 30.1 32.2 60 20 15 Real interest rate 5% € 10 6 5 and carbon tax 20/t 24.1 37.6 50 3 2 0 Fig. 40. The results of the Finnish study compare the price in € of Coal Oil Gas Bio Nuclear Solar Wind

the electric Megawatt-hour for various production modes. Two real Source: ExternE, J. March 1999. Weisse, interest rates are taken into consideration: 5 and 8%. The competi- Fig. 41. Health and environmental costs, called “external costs” for tiveness of nuclear power is indisputable for the low capitalisation various energy sources. rate (5%). Nuclear power remains competitive compared to gas up to a real interest rate of 8%, which leaves a fairly comfortable margin.

In normal operation, energy production systems impact our We will not enter into the debate here regarding the value allo- environment and our health, which should be taken into cated to plutonium, which may be considered as waste or as account if we want to compare them. For some activities, it a precious resource, according to the recycling policy chosen. concerns liquid or gaseous waste, for others it is a noise dis- Recent studies suggest that the economy of fissile material turbance or simply the degradation of a tourist site. They also permitted by the recycling of plutonium barely compensates involve possible accidents, the consequences of which must the costs associated with recycling. The elements of choice be taken into account. The “ExternE” study, carried out in col- are furthermore not only economical but also, and above all, laboration between the European Commission and the US political, because considerations regarding the radiotoxicity of Department of Energy, aims to identify and even quantify final waste, the possible continuation of the nuclear pro- external costs and profits, that is the positive or negative gramme with fast neutron reactors or the proliferation of effects of various energy systems, not taken into account in nuclear materials influences strategic choices. the direct economic assessment. It emerges from these stud- ies, carried out within a European framework, that the external costs of nuclear energy are particularly low.

40 The economy of nuclear power MonoCEA GB 5/04/06 15:30 Page 41

Nuclear power throughout the world

Several events have recently reminded us of the advantages Most countries thus currently integrate nuclear power into their of nuclear power and open new prospects to the sector… reflection on the short and medium term (up to 2020) and long term (2020 and beyond) energy policy. Firstly, there is the European Commission Green Book 11, which recognizes in nuclear power a competitive energy This is actually the case of the United States: between new source capable of responding to the double issue of the safety requirements and the replacement of aging installations, the of the energy supply and the reduction of greenhouse gases. American administration thus evaluates the number of elec- In the same way as controlling the energy demand and devel- tric power plants between 1,300 and 1,900 (that is power on oping renewable energies, nuclear power is currently recog- the order of 400 GWe) which must be installed between now nized as an essential component of a more balanced and 2020, all sources together. European energy mix, privileging energies that do not emit greenhouse gases. The availability of American nuclear power plants has spec- tacularly improved, which constitutes the main reason for the An equivalent document, the “Report of the National Energy renewal of their appeal in the United States. A large number of Policy Group”, published in the United States in May 2001, the 104 American reactors have obtained from the safety delivered a similar message. authority the extension of their operation beyond the initial expected duration, and these “second-hand” reactors are Awareness of the sharp increase of the demand for primary resold between electricians at the price of new reactors. energy throughout the world leads to the recognition that all energy sources will be necessary in order to match the Even if all of the conditions have not been met for significant needs, including nuclear power, which produces practi- investments in new nuclear power plants over the very short cally no greenhouse gases. term, the use of nuclear power for the medium-term remains unavoidable in order to satisfy part of the high demand. Several tens of GWe of nuclear origin will without doubt be necessary by this time.

18 11 4 It is in this context of vulnerability of hydrocarbon supply and 2 16 environmental constraints, that the “National Energy Policy” 27 1 4 4 6 30 4 1 13 8 report, submitted to the President of the United States in May 104 1 59 9 1 19 2001, concludes with the need to resume the development of 2 2 nuclear power in this country. At the same time, the “Nuclear 14 53 6 Power 2010” initiative was launched in order to accelerate the

2 process of granting authorisations in view of the deployment of advanced reactors from 2010.The decision-making process regarding the opening of the Yucca Mountain nuclear waste 2 2 disposal sites has been initiated with the positive vote from Congress in 2002 regarding this project, which had already Fig. 42. Nuclear power plants operating worldwide. obtained President Bush’s support.The Department of Energy (DOE) is moreover very active within the scope of the International Forum on the fourth generation. The importance of closed fuel cycles (“Advanced Fuel Cycle Initiative”) is also being largely reconsidered, beyond the past position of oppo- sition to any reprocessing. Finally, it is important to point out the propositions of research programmes from several national laboratories aiming to relaunch R&D and the related budgets.

11. Published in November 2000.

Nuclear energy of the future: 41 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 42

KOREA nuclear capacity increase + 9 GWe JAPAN by ~ 2015 nuclear capacity FINLAND increase + 21 GWe 5th reactor by 2012 FRANCE CHINA new EPR reactor USA nuclear capacity + 1500 Power Plants by increase > 30 GWe 2020 including nuclear by 2020 (> 50 GWe)

INDIA nuclear capacity increase from 2.5 to 20 GWe by 2020

Fig. 43. There are currently 34 nuclear reactors being built throughout the world, and nearly as many projected.

Russia, in spite of its economic difficulties, seeks to partici- privileged relationship with France, into a nuclear equipment pate in the global reflection on nuclear power and has taken policy with a willingness to control all of the technologies asso- several initiatives in this direction, in particular the launch of a ciated with the construction of reactors. Even though nuclear global concertation, with the IAEA, regarding nuclear power power only represents 1.5% of its capacity with 8 reactors of the future (INPRO exercise) and the vote for a law on operating commercially, China projects having by 2020 a accepting foreign nuclear waste on Russian territory enabling capacity in the order of 35 GWe of nuclear origin, that is the nuclear fuels to be offered on a lease basis. equivalent of 20 to 30 new reactors. The nuclear proportion could therefore reach 4 to 5% of the capacity, thermal and Re-establishing strong economic growth, Russia is now show- hydraulic power remaining largely in the majority. The recent ing a willingness to succeed with its civilian nuclear develop- soaring oil prices and the awareness of the energy depend- ment programme with the completion, then the commercial ence regarding exterior supplies nevertheless leaves open the commissioning of power plants, the construction of which was possibility of an acceleration of the development of the stopped following the Chernobyl accident in 1986. The coun- Chinese nuclear programme. try is also very active with its fast neutron reactor development programme. Japan, which owns little natural energetic resources, has adopted a strategy similar to France’s in the 70-80s. It already The United States and Russia are moreover making specific has 53 reactors which generate 45 GWe, ie approximately efforts, within the framework of , to con- 34% of the national electricity. Four reactors are in the process vert and use fissile materials of military origin. This has created of being built and around ten additional units are active proj- a common reflection, with a high involvement from France, ects. The next report from the Japanese Atomic Energy regarding the cycle of these materials (including in the United Commission will update the deployment projections of the States) and on reactors best suited to reach this objective. electro-nuclear fleet by 2030. The previous report took into account a need in the order of 20 new reactors between now In Asia, China, whose GDP has seen near 10% annual growth and 2030. Japan, whose population is declining, is neverthe- over the last few years, estimates the needs for new electrical less currently beset by political and institutional difficulties capacities at approximately 20 GWe per year during the next regarding nuclear power: the latter is struggling to regain pub- 20 years.This huge figure indicates how important it is for this lic confidence after numerous matters which have punctuated country to increase its production capacities. In the 1980s, the life of the sector during the last few years.The country may China launched itself, up to now within the framework of a therefore downsize its ambitious programme.

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In South Korea, 19 nuclear reactors represent approximately Italy and Austria have declared themselves against nuclear 38% of the national electricity generation. This country is cur- energy since the 1980s; in the same decade, Sweden decided rently constructing 2 nuclear reactors and is planning to to pull out of nuclear power by 2010 but up to now has shut- increase its capacities by constructing an additional 8 reactors down only one power plant; Germany decided to pull out of in the next 12 years. In the longer term, Korea, which is poor nuclear power in 2000 and Belgium in 2001; the United in energy resources, plans to double its capacity installed in Kingdom deferred the decision to renew its reactors to a later 2000. date... Conversely, in May 2003 Switzerland refused to pull out of nuclear power, and Finland ordered a PWR nuclear India, with its one billion inhabitants and in spite of its low per reactor on 18 December 2003. France has just decided to capita consumption (0.5 toe/inhab/year), already figures construct a PWR reactor on the Flamanville site. among the largest energy consumers and is faced with impor- tant energy deficits. Fourteen nuclear reactors, of low power This common absence of vision between the European Union and mainly CANDU* technology, are currently in operation and countries creates an unfavourable global political environment the Indian government hopes to increase the nuclear capac- for nuclear power, and yet this energy currently occupies an ity of the country for it to pass from approximately 3 GWe today important place in Europe: to 20 GWe between now and 2020. In order to do this, India intends to increase its production capacity partly from reac- • It contributes 35% of electricity production; tors developed locally and partly by turning to foreign partners in order to have access to light water reactors*. It should be • It represents an important industrial sector on the interna- noted that the country is actively pursuing its fast system and tional scene, for the supply in reactors (in particular those of thorium system development programme, given its national 3rd generation such as the PWR and the SWR 1000 from reserves. Areva), for operating power plants, and for the fuel cycle;

Brazil relies heavily on its hydroelectricity but has already • The European research on radioactive waste management, commissioned two PWRs, the first ordered from in particular that conducted in France since 1991, is among Westinghouse and the second from Siemens. - the most advanced in the world and from 2006 will enable a ANP is expecting the decision to complete the construction of new management strategy to be decided regarding all of the the third reactor ordered, at the time, from Siemens. The waste produced by nuclear power plants; Brazilian Ministry of Science and Technology has furthermore declared itself in favour of the development by its country of •European community R&D programmes also dedicate sig- research on . nificant resources to thermonuclear fusion.

South Africa, with 2 powerful reactors in operation, is devel- On 1st May 2004, the European Union passed from 15 to 25 oping a 100 MWe high temperature reactor, of the Pebble Bed members: thus 5 nuclear countries out of 10 joined Europe Modular Reactor (PBMR) type, in partnership with BNFL12 with 23 reactors in commercial service. The importance of (GB) and a future partner yet to be defined. This concept of these countries’ integration extends to the nuclear energy sec- small reactor, based on the German pebble technology and tor, in particular in terms of safety and waste management. cooled with helium, mainly targets a faster return on invest- The prospects of collaboration, in particular with the Czech ment than that of the PWRs and would also present the inter- Republic, Slovenia and Hungary are numerous. est of being accessible to small countries, given the smaller initial investment.The ESKOM consortium announced in 2003 Signs of renewed interest are appearing: that it was now ready to pass to the development and con- struction of a PBMR demonstration reactor. • The European Commission “Green Book”, published in 2001 concludes, of course in very cautious terms, on the need to And in Europe? reconsider the nuclear option in order to face energy supply Each European country is sovereign in the choice of its energy problems and to respect the Kyoto commitments; options, which leads to a panorama of very different options for nuclear power. Some countries make great use of nuclear • Through private investors, Finland confirmed its choice of power (nearly 80% of the French electricity generation is of construction of a fifth reactor by placing an order at the end nuclear origin; others have none at all (Ireland, Austria, of 2003 for a PWR reactor with the Areva group; Norway, Denmark, Italy). • Sweden, after closing Barsebäck 1 at the end of 1999, post- poned sine die the shutdown of its nuclear plants because they could only be replaced by a Danish electricity import (with coal) with the consequence, well perceived by public 12. British Nuclear Fuels (Note of the Editor). opinion, of acid rain. Opinion polls are currently in favour of

Nuclear energy of the future: 43 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 44

pursuing the nuclear activity in this country which 20 years ago opposed it by referendum; Lithuania France • Switzerland consulted its population by referen- Belgium Ukraine dum in May 2003 regarding popular initiatives Sweden which should have led to eventually pulling out of Bulgaria nuclear power: A quite clear refusal of renouncing Slovakia this energy emerged, even though in 1990 a mora- Switzerland torium banned the construction of any new power Hungary plant of this type; Slovenia Japan • Germany concluded a political contract, well in the Taiwan South Korea social consensus tradition of this country, to post- Germany pone the real choices to a later date, whilst protect- Finland ing the main thing, that is the operation of existing Spain power plants and thus the country’s safe supply in United-Kingdom electricity; Armenia United States • Belgium more recently turned to a similar track, Czech but changes in its political landscape could even- Canada Russia tually lead to a revision of its position and a possi- Argentina ble repeal of the law for pulling out of nuclear Romania power; South Africa Mexico • Great Britain is conscious that with the foreseen Netherlands shutdown of its ageing reactors between India now and the end of the decade and the exhaus- Brazil China tion of North Sea pools within 25 years (in 2004 Pakistan the country had just crossed its “peak oil”), the Kazakhstan electricity supply will be entirely dependent on %0 10 20 30 40 50 60 70 80 imports in the not too distant future. A re-examina- tion of the energy policy is in progress and a White Fig. 44. The nuclear proportion in global electricity generation. Book came out in 2003. The latter certainly indi-

cates a marked willingness to significantly reduce CO2 emis- sions by 2020 but did not clearly define the British position regarding the nuclear option. Coal (39 %)

Finally, in France, the Parliamentary Bill regarding energy con- Hydroelectricity (19 %) firms the major contribution of nuclear energy in the future Nuclear (16 %) national energy mix and the importance of launching the first PWR reactor in order to guarantee the renewal of the current Gas (15 %) fleet in due course. EDF has entered into the process of Oil (10 %) launching the EPR by selecting the Flamanville (Manche) site for the first reactor. Fig. 45. World electricity generation.

In this context favourable to a rebirth of nuclear power throughout the world, the current objective is to enhance all of the European potential in the development of future • Research issues to develop the key technologies for sus- nuclear systems, with a just return of the profits to come. tainable nuclear power, an issue which presumes a willing- ness from political and industrial players to continue invest- This objective implies the different types of issues for which ing in the R&D for the nuclear power of the future; research laboratories and their industrial partners are prepar- ing themselves: • Industrial issues to enhance the experience acquired in the previous development of prototype reactors or advanced processes regarding the fuel cycle and to commercialize it;

44 Nuclear power throughout the world MonoCEA GB 5/04/06 15:30 Page 45

• Industrial issues also to be recorded in international con- sortiums called upon to market the systems of the future;

• Also issues of development training in international co- operation, which would lead to sharing R&D whilst research- ing the reduction effects of national efforts by synergies, and co-financing opportunities for large research tools or proto- type installations. MonoCEA GB 5/04/06 15:30 Page 46

Nuclear power: the main avenues of research

•To support the current nuclear industry;

•To provide effective and acceptable solutions to the problem of long-lived and high level waste management, and to better understand the impact of nuclear activities on humans and the environment;

•To design and evaluate new generations of nuclear systems (reactors and cycles).

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The near future: research supporting the existing nuclear power

The nuclear industry has reached its full potential. However, For electricians it involves increasing the overall efficiency of the margins of competitiveness can still be improved: its nuclear fleet in order to be competitive in an open market:

• By improving the profitability of the fleet through more effi- • By increasing the burn-up rate* of fuel assemblies; cient use of nuclear fuel; • By extending the irradiation campaigns; • By extending the lifetime of existing reactors.The global fleet of reactors is aging rather well, and many electricians • By reducing the number of assemblies on each reloading throughout the world envisage operating these existing reac- (flexibility of the reloadings); tors longer than the lifetime for which they were initially designed. It is still necessary to obtain authorisations, and • By reducing the operating constraints, in particular during for this, demonstrate that the aging of reactor components is transient periods imposed by the monitoring of grid loading foreseeable and controlled; (these transient periods in fact test the fuel, and the devel- opment of a fuel capable of resisting rapid changes in reac- •By preparing the replacement of the fleet of current PWR tor speed is an important issue); reactors with evolutionary third generation reactors, endowed with an improved efficiency and a (further) increased level of • By controlling the equilibrium of the fuel cycle over the entire safety13. fleet, a policy of matching the reprocessing – recycling flux.

These three avenues of improvement for the near future R&D objectives and challenges regarding require R&D. CEA takes on a large part, in close partnership PWR fuel with the French nuclear industrialists, Areva and EDF. The maximum irradiation (average per assembly) is currently 52 GWd/t whereas it was 33 GWd/t in the 80s. This important Using nuclear fuel more efficiently increase was obtained mainly thanks to:

Industrial issues •A better knowledge (associated with comprehension and At the time of the start up of the programme for the construc- modelling) of the behaviour of the fuel in irradiation provided tion of PWR power plants for electricity production, in the 70s, by the R&D and the feedback from standard or experimen- one of the arguments put forward (apart from the energy inde- tal fuel irradiated in PWR cores, enabling optimised dimen- pendence) was linked to the relatively low cost of the fuel sioning; cycle. Indeed, the fuel cycle proportion in the cost of the kWh (30% including the “upstream” and “downstream” sections of •Progress on fuels themselves (cladding material, pellet, the cycle), did not bring about particular optimisation efforts importance of the fuel ceramic microstructure). At present, for the fuel performances. the burnup rate is restricted by the strength of the cladding (the fuel is removed from the reactor before the cladding Today, given the updated economic reports between the vari- breaks, or rather, before it risks breaking in incidental situa- ous energy production systems, there are important produc- tions). tivity gains to be achieved thanks to nuclear fuel and to its management means. With the objective of reaching burnup rates exceeding 70 GWd/t within the next decade, a certain number of devel- opments and/or confirmations are necessary.These develop- ments concern numerous, often combined, phenomena (cor- rosion of the cladding, internal pressure, mechanical behaviour of the assembly and rods in incidental and acciden- tal situations, etc.). 13. Third generation reactors will be dealt with in the following chapter.

Nuclear energy of the future: 47 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 48

CEA, in close collaboration with its industrial partners, has set retaining fission gases. It has been recently demonstrated up R&D programmes regarding fuel, based on its experimen- that the use of additives introduced into the oxide powder tal means and on its expert capacity. prior to sintering enables the homogeneity to be improved and the size of the surrounding grains to be significantly increased, two important conditions for minimising its R&D programmes regarding fuel gaseous release under irradiation. The current irradiation Responding to industrial needs experiments in progress on these new ceramics will enable In the short and medium-term, the R&D needs expressed by the gain obtained in burnup rate to be quantified. The exper- industrialists require a follow-up or even an increase in R&D iments mainly consist of instrumented irradiations (for an efforts in the following fields: example in the Osiris reactor in Saclay), followed or not by thermal annealing associated to measurements of the fis- • The behaviour and reliability of the mechanical structures of sion gas release (in hot laboratories, for example fuel assemblies for high burnup rates.The progress targeted LECA/STAR in Cadarache). Post experimental examinations consists of a reduction of the mechanical wear and tear of use the following conventional tools: electron microscopy, rods thanks to a better control of their vibratory behaviour in microprobe, mass spectrometry of secondary ions, with the the reactor core. They undergo particular tests carried out in particularity that the corresponding devices are adapted for representative situations (temperature conditions, pressure, the examination of highly radioactive objects; chemistry and geometry of the reactor cores). These tests, carried out on the CEA/Cadarache Hermès installation serve • In the field of cladding, even with current materials or in to validate the modelling and simulation of the behaviour of process of deployment (such as the zirconium-niobium M5 assemblies, and to demonstrate that the main phenomena alloy), the behaviour of the claddings in more demanding at stake are understood and controlled; conditions (high temperature oxidation with steam, hydrida- tion, fragilisation, etc.) must be explored further particularly • One of the R&D objectives in particular regarding MOX fuel for the safety demonstrations of new modes of fuel manage- is to increase its competitiveness by increasing its burn-up ment; rate. The aim is to produce a ceramic capable of effectively

MIC02F1

Addition of Cr2O3 before dilution

MIC0F1

MIC03F1

Addition of Cr2O3 during dilution

Fig. 46. Microstructural analysis of advanced MOX fuel ceramics.The photo opposite compares the local content in plutonium of the MOX pellets sintered respectively with and without chromium additive. The second are much more homogenous.

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• By 2010, the qualification of a fuel much less sensitive to the pellet-cladding interaction is a main objective of the EPR proj- Burn-up rate ect, in particular in order to improve the reactor’s perform- 70,000 MWd/t ances, simplify its design and to minimise the constraints HTC (900 / 1,300)

linked to the monitoring of the power grid loading. 62,000 MWd/t Galice (1,300)

Oxide 52,000 MWd/t thickness (µm) Cyclades (900) Gemmes (1,300) 120 47,000 MWd/t Alcade (N4) Garance (900) 100 39,000 MWd/t 80

60 1990 1995 2000 2005 2010 2015 Zy4 40 Year

20 M5 Fig. 48. Changes in core management involves research on the 0 behaviour of fuel with high burn-up rates. 010000 20000 30000 40 000 50000 60000 70 000 Progress carried out on the strength of the cladding enables much Burn-up higher burn-up rates and a better use of the fuel to be envisaged. Thanks to this type of progress and to this “small steps” policy, the Fig. 47. Example of current progress regarding the fuel cladding: the burn-up rate of nuclear fuel passed from 39 GWd/t to 52 GWd/t zirconium alloys used for the cladding are subjected, in the presence in ten years and progress is still going on: 70 GWd/t is targeted in of water, to corrosion which tends to spiral out of control as the oxide 2010. layer grows, which limits the time that the fuel stays in the reactor and the temperature of the fuel and coolant. Recent progress in the composition of cladding alloys enables corrosion to be considerably reduced and these limitations to be postponed.

In order to carry out these studies correctly, CEA possesses “heavy” facilities: the LECA and LEFCA laboratories enable experimental fuel elements to be manufactured; the Osiris reactor (Saclay) enables the irradiation; the PELECI (Saclay), LECA (Cadarache) and ATALANTE* (Marcoule) hot cells enable these irradiated elements to be analyzed.

Some of these heavy facilities are recent, others are aging. This is the case of the Osiris reactor, which must be replaced by 2014 with a powerful and multipurpose research reactor intended to cover most of the European experimental irradia- tion needs: the *.

Fig. 49 and 50. The Osiris reactor. Experiments on fuel mainly con- sist of irradiations in experimental reactors such as Osiris. These are long experiments, they are intended to validate the modelling, and to provide confidence in its predictive capabilities. They also serve to qualify advanced fuels, prior to their use on an industrial scale.

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Ventilation chimney

“Electronic-control” building Hot cells hall

Orisis reactor Isis reactor

“Crown” building Isis laboratories

Offices Cooling towers

Waste containers

Fig. 50.

Another objective for CEA is to upgrade R&D methods, in par- ticular in the sectors where heavy experimentation is widely used. This involves either taking best advantage of the entire experimentation or substituting it, where possible, with a more analytical experimentation based on a more cognitive approach of phenomena and sizes which govern them. This must be done in complementarity with modelling develop- ment.

Fig. 51 et 52. The future Jules Horowitz reactor should diverge in Fig. 53. The Atalante facility, in Marcoule. Cadarache in 2014.

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Developing modelling and simulation Extending the lifetime of existing reactors CEA has modelling tools and continues to develop calculation codes, continuously improving the predictions on the behav- Planned initially to last for approximately forty years, nuclear iour of reactors and of their components. Apart from the power plants age rather well, as the feedback on the global Cathare thermal-hydraulic* code, the future EDF/CEA fleet shows.That said, nuclear power plants see their profitabil- Descartes (neutronics*), Neptune (thermal-hydraulic) and ity increase considerably once the initial investment is amor- Pléiades (fuel) platforms must be mentioned. tized. The extension of the lifetime of reactors is therefore a major issue for electricians. This is why many nuclear opera- The fuel modelling effort consists of extending the field of valid- tors throughout the world are currently requesting that their ity of fuel behaviour models and to assure their qualification country’s Safety Authority authorize extension of their facilities’ by a specific experimentation.This field in particular covers the lifetime.The French fleet of reactors is younger than the world modelling of the thermomechanical behaviour of the rod, the average, but EDF also wishes to extend the lifetime of its reac- description of the microscopic mechanisms of the fission gas tors. It is still necessary to demonstrate that the system’s safety release on the microstructure level, the pellet-cladding inter- is preserved. action and the irradiation-induced swelling. All of these mod- els are introduced in the Pléiades software application co- The extension of nuclear power plants’ lifetime requires a very developed by CEA and its industrial partners. good knowledge and very good mastery of the aging mecha- nisms of all of their components. It is also necessary to have reliable diagnosis and control means. CEA carries out research in these two fields.

The aging mechanism of a nuclear reactor’s components are very diverse. Some such as material fatigue, corrosion under stress, corrosion-erosion, and wear and tear by friction are absolutely conventional and are found in many other installa- tions or industrial objects. Other mechanisms are more nuclear specific, in particular the fragilisation and swelling of steels due to irradiation and corrosion due to radiation.The various mech- anisms do not act in isolation: it is their combined action which contributes to accelerating the aging of a nuclear power plant’s components, and which is to be controlled.

The aging of the power plant’s components The vessel* of the primary circuit of water reactors is one of the elements presumed to being non-replaceable. It consti- tutes part of the second containment barrier: its mechanical strength must be kept, even in accidental conditions. It is also the subject of a specific lifetime monitoring and evaluation pro- gramme.Thus, on each ten-year visit, EDF presents the Safety Authority with a vessel maintenance file justifying its ability to fulfill this safety function for the next ten years. Fig. 54. Modelling of the pellet-clad interaction. Subject to irradiation, the fuel ceramic pellet tends to swell, due to The main phenomenon of vessel aging is of course linked to disorders of the crystal lattice caused by the irradiation, and due to irradiation damages: The main influencing factors are the interstitial atoms generated by the nuclear reactions (in particular fis- degree of irradiation of the vessel and the loadings sustained sion gases). This swelling, combined with pressures inside and out- side of the zirconium alloy cladding, places the latter under stress. It during power transients. is important to correctly model these stresses and their evolution in time, in order to control the risk of breaking the cladding and releas- The operator minimises the irradiation* of the vessel by using ing radioactivity into the primary circuit of the reactor. fuel loading plans optimised from the neutronic point of view. Knowledge of the condition of the vessel material, in particu- lar on the internal side is essential because existing defects may, depending on their size, favour the propagation of cracks. Experimentally, the irradiation of the vessel is monitored by means of dose measurements on test specimens. Also, the

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vessel’s condition is checked by ultrasounds, which enable the The aging of replaceable components size of the defects linked to cold fissuring and those resulting from intergranular deco- CEA does not carry out specific programmes on the aging of hesions caused by heat- all of the replaceable components from reactors. However, ing to be detected and given their importance, some components are the subject of evaluated. special attention. This is the case of steam generator tubes, the rupture of which may have serious consequences. The The CEA is deeply R&D programmes carried out at CEA concern non-destruc- involved in a large R&D tive testing methods applicable to these tubes, and the two programme which accom- main aging mechanisms identified: corrosion under stress and panies this programme on wear and tear by friction due to flow-induced vibrations. the vessel’s lifetime. It cov- ers the main influencing The vessel internal components are also the subject of spe- factors regarding the eval- cial attention, with the study of the hardening of steels due to uation of the vessel’s irradiation, and the corrosion under stress accelerated by irra- strength and its lifetime. diation. R&D programmes on the subject result, in particular, in the irradiation of internal materials in fast neutron reactors. The main R&D pro- Fig. 55. Vessel defect inspection gramme concerns the The wear and tear of control clusters, cluster guides and con- machine. physical criteria justify- trol mechanisms has been noted on the fleet, and is also ing the strength of ves- closely monitored. The mechanism identified is tribo-corro- sels. Apart from the evaluation of the fluence* sustained by sion, which associates wear and tear and passivation – depas- the vessel, the programme comprizes amongst other things: sivation cycle of the oxidized metal surfaces. This programme • Irradiations of steel test specimens in experimental reactor associating the physical chemistry and the mechanics must vessels (Osiris); lead to the understanding of these phenomena, their model- • The development of methods for the determination of ling and the production of rules to evaluate the aging and the mechanical properties; control cluster replacement policy. • The development of advanced methods in fracture mechan- ics (probabilistic methods), aiming to better evaluate avail- In conclusion, it is important to specify that the calculation able margins of resistance. methods in solid mechanics, in particular in the field of frac- ture mechanics, have made such progress following the com- The monitoring of the condition of the vessel material via puter and digital revolution (finite element analysis) that we are non-destructive testing methods is the subject of R&D actions, currently better equipped to predict the detailed behaviour of in particular regarding the improvement and the qualification the installation without having to resort to unfavourable sim- of the ultrasonic processes implemented. plistic hypotheses. If, at the present time, we find ourselves able to foresee a longer component lifetime, it is largely due The operating return from reactors shows a few aging phe- to the modern techniques of digital computing. nomena that must be taken into account in order to be able to assure the lifetime of the containment. It constitutes the last barrier for the retention of radioactive materials in the event of a serious accident. In order to justify an increase in the lifetime of the containment, it is necessary to show that it would still play its role in an accidental situation. The various aging phe- nomena observed or envisaged are corrosion of the internal metallic skin and the degradation of the concrete containment, by fissuring or corrosion of the reinforcements. CEA con- tributes via its R&D programmes to the improvement of knowl- edge regarding these subjects.

52 The near future: research supporting the existing nuclear power MonoCEA GB 5/04/06 15:30 Page 53

Preparing the replacement of current reactors with more efficient and safer 3rd generation reactors

Firstly let’s briefly recall the various generations of reactors quantity and the long-term harmfulness of final waste, condi- since the 50s: tioned in order to ensure safe and sustainable containment of the radionuclides. The first UP1 reprocessing plant in Marcoule, for the reprocessing of GGR fuels, was commis- The first generation of reactors sioned in 1958, followed by the UP1 plant in La Hague in 1966, The first generation of reactors was strongly influenced by fuel itself equipped in 1976 with a new workshop (HAO) for the cycle constraints, particularly in the 50s and 60s, with the reprocessing of pressurized water reactor fuel. They are now absence of uranium enrichment industrial technology, and on replaced by the two UP3 (1989) and UP2-800 (1994) plants in the other hand with the willingness of some nations to equip La Hague. MOX fuel manufacturing installations have likewise themselves with a nuclear deterrence tool requiring the pro- been developed and commissioned: CFCa Cadarache (1968- duction of fissile materials. In this context, reactors had to be 2003), Dessel in Belgium (MOX fuels produced from 1986) able to operate with natural uranium (non-enriched, requiring and Melox in Marcoule (1995). the use of moderators such as graphite or heavy water*.This is why family of Natural Uranium Gas-Graphite reactors The second generation of reactors (GGR), was developed in France.Three reactors, intended for producing plutonium (G1, G2 and G3) were created first, then The second generation of reactors which corresponds to the six others intended for generating electricity (Saint-Laurent14, majority of the global fleet currently in operation originated Bugey15 and Chinon 16). from the need to render nuclear energy more competitive and from the willingness to reduce the level of energy dependency CEA was very strongly involved in the development of this sys- of certain countries at a time where a great deal of tension on tem, in the capacity of process supplier. The Magnox type the fossil energy market was being felt. The production of fis- reactors in Great Britain belong to the same generation.These sile materials for defence purposes was no longer a priority, reactors presented interesting characteristics (thermodynamic enriched uranium produced by gaseous diffusion was com- efficiency, optimised use of uranium in the reactor core, etc.), mercially available ( plant in France). This period was but also limitations linked to the technology of these types of that of the deployment of water reactors, pressurized water reactors, in view of development on a much larger scale: high reactors PWR and boiling water reactors BWR, which consti- investment cost, difficulty in improving the safety and the tute more than 85% of the current global electro-nuclear fleet extrapolation to a much higher capacity, which penalized their of approximately 450 reactors. economic performances as compared to light water reactors. Industrial feedback from the last few decades has enabled This first phase saw a rise in concerns developed relating to economical as well as environmental performances of the pro- the fuel cycle, regarding both the rational and sustainable use duction of nuclear energy to be demonstrated, with a highly of natural resources (recycling of energy materials, in particu- competitive cost of the nuclear kWh in relation to that of fossil lar plutonium) and the question of waste management. This energies and a continuous reduction of waste and effluents, led to the development of processes and installations for the well below the authorized limits. The cumulated operation of back-end of the fuel cycle: reprocessing of spent fuel, recy- more than 10,000 reactor-years proves the industrial maturity cling of plutonium. From the beginning, France thus adopted of this technology. the fuel cycle based on reprocessing-recycling, enabling on the one hand a better use of resources, by recycling plutonium in the reactors, and on the other hand, the reduction in the

14. Municipality of Saint-Laurent-Nouan (Loir-et-Cher). Nuclear power sta- tion on the Loire (Note of the Editor). 15. Municipality of Saint-Vulbas (Ain). [Note of the Editor.] 16. Indre-et-Loire (Note of the Editor).

Nuclear energy of the future: 53 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 54

The third generation The types of 3rd generation reactors

The third generation represents the most advanced con- •Advanced water pressurized reactors structible industrial state-of-the-art. It involves reactors known AP 600, AP 1000, APR1400, APWR+, EPR as “evolutionary”: They benefit from the feedback and the industrial maturity of second generation water reactors, whilst • Advanced boiling water reactors integrating the most advanced specifications in terms of safety, ABWR II, ESBWR, HC-BWR, SWR-1000 knowing that the second generation already shows a very high • Advanced heavy water reactors level of safety. ACR-700 (Advanced CANDU Reactor 700)

• Small and medium power integrated reactors rd 3 generation reactors are the subject of a large international CAREM, IMR, IRIS, SMART offer. These reactors are already being constructed in partic- ular in Asia, but also in Finland and soon in France • Modular high temperature gas reactors GT-MHR, PBMR

Renewal at 50,000 MW spread over 30 years (2020-2050)

Rate of nuclear construction: 1,667 MW/year

70 000

60 000

50 000 Extension beyond 40 years 40 000 Generation 4 Current fleet 30 000 40 years lifetime Installed power (MWe) Installed power

20 000

Generation 3+ 10 000

0 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060

Average fleet lifetime: 48 years

Fig. 56. The renewal schedule of the French nuclear reactor fleet, as The schedule envisaged for the EPR deployment in France is as currently envisaged by EDF. follows: The operator will without a doubt wish to extend the lifetime of the existing reactors as much as reasonably and legally possible. It is 2005 Decision for an EPR demonstrator planned to start the replacement of one part of the fleet “in bevel” as 2003-6 Regulatory authorisation process and preparation of 2020 in order to smooth out the financial effort, firstly with third, for construction then fourth generation reactors. 2007-2011 Construction and commissioning of the EPR demonstrator France is extensively equipped with nuclear power and its fleet of 2012-2014 Acquisition of the operating feedback (minimum 3 years) reactors is relatively young.Yet, the construction of a demonstration 2015 Decision to construct an EPR series (number and rate EPR has just been decided. Why is this step being taken now? The to be defined) development of a new system is a long-drawn-out operation: in order 2020 Commissioning of the first reactor of the series to introduce third generation reactors in 2020, it is necessary to 2021... Commissioning of the following reactors order an EPR prototype now.

54 Preparing the replacement of current reactors with more efficient and safer 3rd generation reactors MonoCEA GB 5/04/06 15:30 Page 55

CEA is associated with the EPR*, pressurized water reactor, •A technical lifetime of 60 years, compared to 40 years in gen- prototype studies which represent the fruit of approximately eral for current power plants. The reactor should be able to 10 years of collaboration between Framatome and Siemens. operate for 40 years without important rejuvenating opera- The two industrialists designed a reactor which uses the best tions; of the technologies from French N4 and German KONVOI reactors. • Reduced operating costs: increased availability approaching 92% compared to 82% today, partly due to shorter shut- downs for reloading (in the order of 16 days) and to design Industrial issues choices (simplified maintenance of components is made pos- The EPR meets two main objectives: sible during operation with the aid of the redundancy of safety circuits), reduction of the collective radiation doses for the •To make nuclear energy more competitive in relation to fos- maintenance staff (0.5 compared to 1 m.Sv/year currently); sil energies; •To further strengthen the reactor safety. • An optimised construction time (approximately 57 months);

• Strengthened safety combined with a more forgiving system regarding possible control Containment designed Molten core () to resist a hydrogen retention device faults, a significantly improved explosion in the event of an accident in-depth defence regarding the resistance to possible serious accidents (core fusion). The Heat evacuation benefits provided by this system strengthened safety results in the non-necessity of evacuating populations, even in the event of a serious accident.

4 independent areas R&D objectives for the redundant Water tank safety systems and challenges

The EPR enables optimised Fig. 57. The EPR project: a pressurized water reactor design which reactor operation management takes into account a large amount of feedback from second genera- and a higher degree of flexibility tion PWRs, with increased safety requirements. of use of the fuel resulting directly in a better competitiveness. In terms of safety, an important effort has been carried out in order to minimize the consequences of possible core melting accidents thus contributing to better public acceptance.These two topics relating to the fuel and the safety are still important Main characteristics of the EPR R&D challenges in order to improve the concept and make it yet more competitive. In the near future, CEA will mainly inter- The characteristics of the EPR, enacted by an omnipresent vene in the field of physics and core management and in the concern to improve performances and economy, may be sum- field of safety. marized as follows: •A net electrical capacity of approximately 1,600 MWe (com- pared with 1,450 MWe of the N4), well-suited for regions with many well-linked power grids.This increase in capacity down- Core physics and EPR core management scales the costs per KWh; EPR reactor cores are made of the same standard fuel ele- • An energy efficiency of approximately 36% (10% better than ments as pressurized water reactors.They mainly differ in size, reactors from the previous generation) mainly due to a slightly lower fuel rating and a more economical fuel man- increase in performances of steam generators and turbines; agement in fissile material. •A possible use of various types of fuel (UOX* or MOX, or even 100% MOX) thus allowing a flexible and more econom- ical management of resources and waste (15% reduction of the quantity of uranium needed to produce the same quan- tity of electricity);

Nuclear energy of the future: 55 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 56

CP1 – CP2 P4 – P’4 N4 EPR Heavy reflector Electric power 900 MW 1,300 MW 1,450 MW 1,600 MW Water Core thermal power 2,785 MW 3,817 MW 4,250 MW 4,450 MW Type of assembly 17*17 17*17 17*17 17*17 Number of fuel rods per assembly 264 264 264 265 Fuel rod height (m) 4 4.3 4.3 4.6

Number of assemblies 157 193 205 241 Core Average linear power density (kW/m) 18.4 18.9 19.8 16.3 envelope Water New 1 cycle 2 cycles A heavy reflector, made of a steel plate surrounding the core, 3 cycles enables a better neutonic economy. Thus the core is more Fig. 58. Positioning the UOX fuel bundles in the reactive and will require a lesser investment in fissile material EPR core. in order to produce the same quantity of energy.This gain also shows in cycle length. MOX management modes The heavy reflector also enables a reduction of the high The benchmark management modes for the use of MOX fuel energy neutron flux* on the vessel. This reduction of fluence are 50% MOX hybrid modes with renewal by a quarter of the authorizes as of today a vessel lifetime of 60 years. UOX bundles and by a third of the MOX bundles. The length of the cycles is 18 months, the respective burnup rate reached An experimental as well as theoretical R&D programme is by these two types of fuels are 60 and 55 GWd/t. required to increase the accuracy of the industrial calculation schemas and save the maximum amount of fuel. In parallel, The fuel management modes in the reactor are chosen to it is also necessary to further qualify the “neutron transport cal- save fuel, by guaranteeing reactor shutdown times as short as culations” of the fluence on the vessel. possible, by assuring a long lifetime to the various reactor com- ponents, all this in compliance with safety rules. These man- The large size of the EPR’s core requires three-dimensional agement modes therefore result in a complex optimisation, the calculation methods with local reconstruction of the power. result of which narrowly depends on the characteristics and They require a specific qualification from the neutronic point performances of the fuel and the components of the core itself. of view (for the accurate evaluation of strong gradients of neu- The continuous improvement of these performances already tron flux in the fuel bundles), and from the thermal-hydraulic leads to innovative management modes being researched for point of view (in order to correctly evaluate the local develop- the EPR reactor. ment of the moderation by the water which causes the neu- tron transient. Apart from the conventional studies carried out and necessary for the neutronic qualification of the desired burnup rate cal- culation schemas, which consist of: • Analysing the isotopic composition of the irradiated rods; EPR fuel management modes •Evaluating by oscillation in the Minerve reactor the integral UOX managements cross sections in order to evaluate the uncertainty of the cal- For UOX cores, the standard management mode projects a culation schemas and to minimise it; stay time of the fuel in the reactor of 72 months, with renewal • Optimising and validating the neutronic calculation schemas of a quarter of the fuel every 18 months, the final burnup rate for these burnup rates; being 60 GWd/t. The specific design of the EPR core requires a certain num- ber of additional qualification elements.

This core can accomodate various reflector concepts and exact evaluations of their influence are carried out there as much on the core’s neutronic properties, as on the fission dis- tributions in the core’s rods, in particular in the periphery. In addition, this programme must enable the measurement of the neutron flux and in particular fast neutrons beyond the core in order to be able to validate the calculation of the vessel’s flu- ence.

56 Preparing the replacement of current reactors with more efficient and safer 3rd generation reactors MonoCEA GB 5/04/06 15:30 Page 57

To study the accidents which must inevitably be taken into The fuel without PCI account with the new core managements and new fuels (for A main objective is to eliminate the constraints due to the class example, rupture of steam piping system) thermal-hydraulic- 2 “PCI” (pellet-clad interaction) by 2010. Candidate products neutronic-fuel coupled calculations are necessary.These stud- exist (in particular the UOX fuel doped with chromium). Three ies are carried out with the current calculation codes, Cathare study points were retained: and Flica for the thermal-hydraulics, Meteor for the fuel and Cronos for the neutronics. For the future (by 2010), these • The implementation of irradiation tests in more demanding analyses will be conducted more easily with the calculation transient operating conditions (power transients simulating tools in process of co-development by CEA and its industrial the load monitoring) for the qualification of the fuel; partners: Neptune for the thermal-hydraulics, Descartes for the neutronics and Pléiades for the fuel, tools integrated into a • The 3D fine modelling aiming to obtain a better understand- unique software platform. ing of the PCI phenomenon. A relevant physical modelling must enable the evaluation of the damage leading to the cladding’s loss of integrity, the impact of the design’s devel- opments, and the impact of the operating and transient his- tory;

• The “1.5D” “industrial” modelling copied both on the tests and on the above calculations.

The EPR’s safety The evaluation of the consequences of a serious accident on the EPR is placed within the framework of the in-depth defence safety procedure and the joint recommendations issued by the French and German Safety Authorities published in 1993. The procedure established as of the design studies according to a deterministic method complemented by prob- abilistic studies targeted the following objectives: Fig. 59. Over the past approximately twenty years, CEA, EDF, IRSN 17 and Framatome-ANP 18 have developed the Cathare acci- • Elimination in practice of the accidental conditions which may dental thermal-hydraulics code. This tool enables any type of acci- lead to important discharges of fission products in the short- dent that may occur on light water reactors to be simulated. More term; particularly, the Cathare code presents a wide validation field for PWR accidents; it is used intensively in France by industrialists and the Safety Authority for all of the case studies relating to the safety • Elimination of the need to displace the population in serious and control of reactors. With reference to the development of the accident situations, without the emergency evacuation of the EPR, the code was used as a benchmark tool for the design and for close neighbourhood and without long-term restriction for the accident studies. consumption of food products.

In serious accident situations on the EPR, the abovemen- For the EPR, primary coolant loss accidents of the large break tioned objectives may be obtained using a strategy enabling type (APRP-GB) are in principle excluded by design; indeed, the integrity of the containment to be assured. The strategy leak detection devices on the primary piping enable them to be mainly relies on the possibility of reliably depressurizing the avoided. primary circuit, on the establishment of hydrogen recombin- ers in the containment, on the installation of a double-wall con- In serious accident situations with important degradation of tainment with filtration in order to reduce the risks of radiation the reactor’s core, the mixture of molten materials (corium) leakage and finally on the design of a corium catcher respon- would eventually attack the bottom of the vessels and could sible for assuring stabilisation of the corium over the long term. pierce the wall. In order to collect and stabilize the corium over the long-term, a “spreading” type of retention device has been

17. Institute for nuclear radioprotection and safety (Note of the Editor). 18. Framatome ANP stems from merging of the nuclear activities of Framatome and Siemens. Framatome ANP has built more than 90 reac- tors, more than one third of the world’s nuclear capacity (Note of the Editor).

Nuclear energy of the future: 57 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 58

planned underneath the vessel (Figure opposite).This corium catcher system is an innovation with respect to current reac- tors. It should be noted that numerous studies in the fields of high temperature metallurgy, physical chemistry of materials and rheology* were conducted in France and Germany in order to design and test the EPR’s retention device.

The EPR’s corium catcher

Sacrificial material Protective layer:

Spreading compartment Sacrificial material

-7.80m

Melt Melt plug Basemat cooling Zirconia layer discharge channel

Fig. 60. Framatome ANP has designed a corium catcher outside of door. In order to deal with the long-term situation, it is necessary to the vessel based on a concept of spreading over a large surface be able to evacuate the residual power (in the order of 35 MW) for a area with long-term cooling and stabilization of the corium. The corium mass of approximately 200 tonnes. The cooling efficiency - in retention device is located in a dedicated compartment in the con- the upper part thanks to the corium flooding, and in the lower part tainment so as not to sustain important stress during the vessel’s thanks to the metal cooling structure - will enable all of the corium to rupture. This compartment is separated from the reactor pit by a melt be stabilized within a few hours and solidified within a few days.

58 Preparing the replacement of current reactors with more efficient and safer 3rd generation reactors MonoCEA GB 5/04/06 15:30 Page 59

Research regarding waste management

Several lessons are currently Whereas large volumes of short lived radioactive waste confirmed are currently managed industrially in surface disposal sites, the long-term management of long-lived high level radioactive • The very nature of final radioactive waste, which cannot be waste is the subject of important research in the countries gen- recycled or reused, depends on the available technology: the erating nuclear electricity in significant quantities, such as final waste in 30 years may differ from that produced today. France, Japan and the United States. What should be done Thus B and C (glass) waste, already produced, is final waste with this waste has remained a conflicting question for many for our generation. Eventually, it will without a doubt be pos- years. Yet, scientific knowledge is advancing and technical sible to further reduce the radiotoxicity* of vitrified C waste solutions are taking shape. Nevertheless, science and tech- by eliminating some of the radionuclides (minor actinides) nology largely interfere with the social dimensions of the prob- that it still contains today. This is the subject of the research lem posed. People’s fears remain strong and difficult to on enhanced partitioning and transmutation.The elimination appease, especially when the danger persists on time scales of these radionuclides would also reduce their thermal power. which defy common comprehension. In addition, the geopolit- Nevertheless it will be necessary to be able to make them ical context, the energy crisis which has followed and the fears disappear by transmutation if a net gain in the radiotoxic of consequences of climate warming open ideological debates inventory is to be produced. Prior to becoming an industrial regarding the energy choices to be made and the very nature practice, these technologies require complementary of the economic development to be privileged for a sustain- research and development in order to enable their integra- able exploitation of the planet’s resources. Nuclear energy and tion into a viable economic contex; radioactive waste management play a large part in these debates. •A permanent host location must also be found for the final waste. Deep geological disposal seems to be the only very What is the future for this long lived radioactive waste? In long-term management solution where the safety measures France, the Bataille Act, voted in 1991, clearly posed this ques- do not require continuous control by the society. An interna- tion to the scientific community by requiring that all options be tional consensus was established on this question, agreed examined, and by proposing several research avenues. on by the International Atomic Energy Agency (IAEA), the Nuclear Energy Agency (NEA) or the Organisation for Economic Co-operation and Development (OECD). No other What are the results of these efforts equivalent solution has appeared, neither in France, nor else- and what prospects do they offer? where in the world;

The orientations of this research are mainly concerned with •A geological disposal facility will always be a rare, therefore reducing the volume and dangerousness of the waste by sort- expensive, resource. It should be used as effectively as pos- ing and recycling. These are the same principles as those sible, by further reducing the volume and the thermal power retained for the management of other household and industrial of the final waste which will be stored, two parameters which waste. They have been implemented for several decades with largely condition its capacity, therefore its utilisation period, the industrial reprocessing of spent fuel in La Hague, which and its cost. The reprocessing of spent fuel, practiced in enables energy materials that can be upgraded, such as pluto- France, is already going in this direction because it enables nium and uranium to be recycled. Can we do better? This is the the extraction of uranium representing more than 90% of its question posed to scientists. mass, and the recycling of plutonium, the highest contributor to its overall radiotoxicity; The radioactivity of waste, which for some may persist for long periods, requires the use of effective containment systems as • Therefore, the American AFCI (Advanced Fuel Cycle long as the danger subsists. The cost of these diverse meas- Initiative) initiative is exemplary. After twenty years of efforts ures, evaluated by the yardstick of their effectiveness, will of leading to the decision of creating the spent fuel disposal site course have a decisive impact with regard to decisions and to of Yucca Mountain, the Americans are now considering the the schedule which will be implemented resulting from the law. optimization of its usage, and therefore the very nature of the objects which will be placed there;

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• In addition, waste conditioning studies will be continued by uncertainties associated with long timescales.This option will researching an even better containment and a volume only be practicable when we have the ability to separate and reduced as much as possible. The space thus saved in the transmute radionuclides. disposal site will help to make the industrial practice of increased spent fuel reprocessing profitable; Enhanced partitioning: what are the consequences regarding long-term waste management?

The issue of enhanced partitioning, that is the additional extraction of radionuclides other than plutonium and uranium, is the reduction of the radiotoxicity of the future high-level waste.

Figures 63 and 64 illustrate the decrease in radiotoxicity of UOX spent fuel as a function of time, as well as the relative contribution of each category of radionuclide to the overall radiotoxicity.

Fig. 61. The underground laboratory operated in Bure by the French National Radioactive Waste Management Agency (ANDRA). 108 Sv / tonne 6

Crest 5 U North portal Other South portal 4

Main tunnel 3 Pu (ESF) Storage 2 gallery

1 PF Emplacement Drift 0 1 10 100 1 000 10 000 100 000 1 000 000 Time in years

Waste package Drip shield Fig. 63. Radiotoxicity of spent fuel.

108 Sv / tonne 1 Other 0,9 Fig. 62. The concept of the underground disposal site at Yucca 0,8 U Mountain (Nevada), developed by the United States Department 0,7 of Energy. Am 0,6 Np 0,5 Pu 0,4 0,3 0,2 • The safety of the disposal site relies on its capacity to con- PF 0,1 tain radionuclides in geological formation until their radioac- 0 tivity has sufficiently decayed. Finally, the demonstration of 1 10 100 1 000 10 000 100 000 1 000 000 the safety of a disposal site will rely on the firm conviction of Time in years the correct operation of the installation. Studies must be pur- Fig. 64. Distribution of contributions to the spent fuel radiotoxicity. sued in order to better understand the evolution of the waste packages in disposal situations over time and the migration of radionuclides into the geosphere. Eventually, removing from the vitrified waste packages the long lived radionuclides which contribute the most to their long-term radioactivity, will significantly reduce the time during which they remain dan- gerous and will also have the effect of reducing the scientific

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Plutonium* contributes approximately 50% of the initial Also the final purpose of the partitioning should be specified, radiotoxicity and 90% one hundred years later. Thus, as soon that is the method of eliminating partitioned radionuclides. as the spent fuel has been processed, that is, the plutonium Which radioelements should be partitioned and which parti- (with uranium) that it contains has been extracted, the resid- tioning modalities should be retained: should radioelements ual radiotoxicity remains dominated by that of the fission prod- be partitioned separately or as a group? Which purity and ucts (FPs) and of curium over approximately one hundred which chemical form must be given to the partitioned elements years and, over a longer time frame, by that of other minor in order to meet the constraints of the following stages leading actinides (MAs) (americium and neptunium). to their recycling and/or their permanent elimination? What consequences can be expected on the design of the geolog- The FPs and MAs are currently all incorporated into vitrified ical repository site, its cost and its long-term containment per- waste resulting from the reprocessing of spent fuel. A follow- formances? The answers to these questions are of course ing stage would therefore consist of only including FPs in linked to the future of partitioned elements. The last stages of future C waste. development may include an industrial process pre-control phase. The figure 65 shows the comparison of the decrease in radiotoxicity of the materials respectively contained in a spent Apart from minor actinides, partitioning studies have con- fuel assembly, in a vitrified package produced today (MAs and cerned a selection of FPs (iodine, technetium and caesium). FPs) and in a vitrified package from which the minor actinides Some FPs, which are much less radiotoxic than MAs, show would have been eliminated (thus only containing FPs). particular mobility in the geosphere. Their lifetime, very long for some, such as isotope 129 of iodine, may pose the threat of a return to the biosphere in the very long term. 10,000 However, the potential damage of these low radioactive radionuclides is very 1,000 low, which currently authorizes the dis- charging of iodine into the sea. 100 Spent fuel ALARA* type criteria should guide 10 (Pu + MAs + FPs) future decisions regarding the matter.

1 Relative radioactivity Enhanced partitioning must therefore Glass without MAs Conventional glass (FPs only) (MAs + FPs) mainly concern minor actinides in order 0.1 10 100 1,000 10,000 100,000 1 000,000 to reduce the radiotoxic source term. Time (years) Beyond aqueous method processes, Fig. 65. Decrease in the relative radiotoxicity as a function of time. studies of processes based on pyro- (The radiotoxicity of the glass or spent fuel is estimated here in chemical techniques must be compre- relation to that of the uranium which produced it.) hensively pursued. The latter effectively present a potential advantage in terms of compactness. Partitioning is obtained in one pass and may concern highly radioactive spent fuel. Enhanced partitioning studies19 currently concern the minor These characteristics make up a technique which, if these actinides americium, curium and neptunium. For the hydromet- advantages were confirmed in regard to the disadvantages allurgical method, they are at the technical demonstration (corrosion, partitioning efficiency, etc.) and if it reached an stage and already deal with a significant quantity of spent fuel industrial development stage, could take its place in an inte- (approximately 15 kg placed in solution). The process steps grated cycle on the reactor site, thus avoiding the transporta- retained for the enhanced partitioning are largely based on tion of radioactive materials over long distances. However, it industrial knowledge regarding the Purex process used in La is advisable to pay close attention to the secondary waste, Hague. A first technical and economical evaluation of an salts and technological waste, which may result.The combina- enhanced partitioning workshop will provide clarification on tion of pyrochemical and hydrometallurgical processes may the technical modalities and economical conditions of use of also be envisaged. such a process.

This technical demonstration alone will, however, not be suffi- cient to enable the industrial application of the process.

19. See infra, p. 67, the chapter entitled “The fuel cycle of future nuclear systems”.

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Processes for the partitioning of radionuclides The potential of various reactor systems for transmutation has been studied. It emerges that only the fast spectrum reactors, Plutonium recycling is already an important stage for reducing or systems combining a sub-critical* core reactor with an the radiotoxicity of spent fuel. accelerator (ADS, Accelerator Driven System* 20) would enable transmutation efficiency to be obtained creating a real Beyond that, removing minor actinides from vitrified waste pro- duced today would enable their radiotoxicity and their thermal difference in radiotoxic inventory. Nevertheless, transmutation power to be further reduced. The recovery of minor actinides remains a very complex and certainly expensive operation, may be a step toward their elimination by transmutation. The which cannot be applied to all radionuclides. consequences on all of the steps of the fuel cycle must be carefully evaluated. Major technological questions are posed.Their resolution may only be envisaged in the context of the sustainable develop- Hydrometallurgical processes may be preferred, because ment of nuclear energy and the development of new nuclear they are better known. However, the potential of pyrochemi- energy production systems of the fourth generation. cal processes must continue to be examined. These questions concern all of the stages of future cycles: Nevertheless the question remains of knowing at which moment to begin the enhanced partitioning method, in coordi- nation with the opening of reactor transmutation possibilities. • Which fuel and which waste reprocessing and recycling Finally the net radiotoxic inventory which would result from processes to use? implementing enhanced partitioning must be established. The economy of the process must also be specified in an • What types of reactors? To date, it is admitted that a fast neu- ALARA context. tron reactor is the most performant tool for obtaining the transmutations of the elements envisaged.

• What is the economic impact for the entire cycle?

The transmutation of partitioned The Generation IV fast reactor route would enable the gener- elements: future cycles ation of electric energy and a better use of the natural resource “uranium” in the future by converting uranium 238 into a fissile Transmutation is the operation by which highly radiotoxic element, via neutron capture. radioelements are transformed into other elements with reduced or zero radiotoxicity. An ADS, dedicated to transmutation and generating no elec- tricity, would be a more expensive and even more complex The research carried out for more than 10 years provides machine because it involves the coupling and the stable and numerous clarifications and in effect confirms the possibility of reliable operation of two sophisticated components: a high reducing the radiotoxic inventory present in spent fuel. But this intensity accelerator and a sub-critical reactor core. can only take place at the cost of important technological and financial efforts, concerning all of the nuclear fuel cycle plants The time scale for implementing these new systems could be and reactors, if a significant net gain in the radiotoxic inven- between approximately 30 and 40 years according to the tory is to be recorded. means that are attributed to them.

How useful would it be to transmute MAs if the disposal facil- The continuation of transmutation studies will be carried out ity reaches its currently calculated containment performances? using experimental irradiations of various materials in fast Transmutation, in such a context, could appear as an addi- reactor cores (Phénix* reactor), and on progressively increas- tional measure of safety in the eventuality of a premature loss ing quantities. It is on the international level that they may of the disposal site’s containment. progress the best by sharing experimental means, in France, Japan and Russia. Transmutation, implemented in this way, will lead to final waste which it will be necessary to dispose of. All elements are not The studies of scenarios will enable the best possible techno- easy to transmute and the multiple recycling of plutonium and logical combinations to be identified in view of optimizing mate- minor actinides, according to the scenario envisaged, could rial inventories. lead to the production of increased quantities in minor actinides, of which in particular, curium. This highly radioac- tive and very hot element poses management problems which remain yet to be solved.

20. See infra, p. 95, the chapter entitled: “Other avenues for the distant future: thorium cycle, hybrid systems, fusion”.

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acterised by the emission of a thermal power in the order of two kilowatts on the date of their production;

• Standard compacted waste packages (SCWP) contain long lived intermedi- ate level waste. It mainly concerns metallic elements of the structure of spent fuel bundles (tubes, braces, grids);

• Long lived intermediate level techno- logical waste packages, cemented because not compactable, represent- ing only 0.1% of the initial activity.

Fig. 66. The Phénix fast reactor on the Marcoule site (Gard).

The transmutation of minor actinides

The transmutation of minor actinides could enable the reduc- tion of the radiotoxicity of radioactive waste produced as of the advent of 4th generation fast reactors, around 2030 to 2040.

Prior to their implementation, many technological deadlocks must be removed regarding their design, their fuel (type and manufacturing and reprocessing technologies), their nuclear materials inventory (recycling of radiotoxic materials), their safety and their economy.

Fast reactors would enable the use of large stocks of depleted and/or reprocessed uranium, thus conserving the natural resource.

There are even more technological deadlocks to be removed for the ADS.

Fig. 67. Standard vitrified Fig. 68. Standard compacted waste container (SVWC). waste container (SCWC). The conditioning of waste and the long-term behaviour of the packages

The conditioning of B and C radioactive waste, originating from the reprocessing of spent fuel, has been carried out continu- ously according to the industrial standards approved by the Safety Authority, since the commissioning of the UP3 facility in La Hague. It gives the waste a physical and chemical stabil- ity which prevents its dispersion into the environment. At the end of the chain, it leads to the production of packages enabling the waste to be easily handled.

Three types of waste packages are currently standardized: Fig. 69. Bitumined waste Fig. 70. Technological waste package. package. • Standard vitrified waste packages (SVWP) contain the quasi- totality of the initial radioactivity of spent fuel. They are char-

Nuclear energy of the future: 63 what research for which objectives? MonoCEA GB 5/04/06 15:30 Page 64

The oldest C waste, originating from the industrial cycle or alteration in question to be identified. Studies still in progress from research, was, either stored whilst awaiting its vitrifica- aim to better determine the moment from which radionuclides tion, or already packaged in glass; B waste was transformed may start to disperse outside of the package into the rock of in forms different from current standards, in cement or bitumi- the geological formation, then into the geosphere, to then nous packaging matrices. reach the biosphere.

For most of this old waste, producers have already specified While the French strategy consists of reprocessing spent fuel, the benchmark strategies that they intend to follow in order to studies on the long-term behaviour of spent fuel have never- condition them. R&D actions are carried out on the benchmark theless been carried out in the hypothesis of long-term storage conditioning. This is for example the case of STE3 sludges in or even geological disposal. According to the decisions which La Hague, for which COGEMA plans to use a bituminous will be taken at the end of the 15 year-period prescribed by packaging, suitable for the specificities of these sludges. the French law, these studies could be stopped or redirected to very specific aspects. For existing packages industrially produced according to cur- rent standards, the research aims above all to evaluate their The research on the conditioning and long-term behaviour of durability, or more generally their long-term behaviour, in stor- waste packages must be continued in order to accompany age and then disposal conditions.The results of these studies technological developments, as for example the increase in thus contribute to the evaluation of the long-term containment the burnup rate of spent fuel envisaged by EDF, which will performances of radioactive waste management modes, and result in modifications of the type and quantity of radionuclides therefore the safety of the latter. which are found in vitrified waste.

The quality of the conditioning carried out contributes to delay- Finally, new conditioning matrices have been studied in order ing the moment from which radionuclides start to migrate out to contain over long periods elements that are difficult to trans- of the package. Behaviour studies are thus interested in all of mute and/or elements that are particularly mobile in geologi- the packages and most particularly in vitrified waste packages. cal disposal conditions. It will be advisable to evaluate the rel- evance of their implementation regarding the particular risk The durability of vitrified waste packages has been studied for that they may help to reduce and the overall cost that this over twenty years. It will continue to retain attention because implementation could represent. Nothing to date lets presume this package contains the highest radioactive inventory. Glass that such an option must in principle be retained. is currently the most durable material (matrix) used industri- ally in order to host and immobilize a large inventory of highly radioactive radionuclides. Its behaviour over a few hundreds of years in storage conditions poses no problems. Over a much longer term and in geological disposal conditions, stud- ies have already enabled the mechanisms and kinetics of

Grain boundaries 14 C +Mo, Tc, Ru, Rh, Pd 129 I 135 Cs 137 Cs 79 Se Fractures 99 Tc Cladding-pellet gap Gap 90 Sr Inter-pellet gap 36 Cl Closed porosity

Matrix Actinides Fission products (98 %)

14 Zr cladding C 93 Zr 36 Cl

Fig. 71. Glass casting in the laboratory at Fig. 72. Simplified diagram of the microstructure of spent fuel and the Marcoule (Gard). location of the various radionuclides.

64 Research regarding waste management MonoCEA GB 5/04/06 15:31 Page 65

The containment of the radioactive materials accessing information at any moment regarding the packages which are stored there. The conditioning of waste consists in the production of pack- ages which assure the containment of the radioactive materi- In future, the studies will concern rather the way of best mas- als and makes their handling possible. tering the durability of the concrete and materials used in the storage installations. The research on conditioning and the long-term behaviour of waste packages remains open, in order to accompany the If in 2006 the decision was made to engage means in view of technological developments in progress (increase in burnup the creation of a geological repository site, it would then be rates, etc.) or the decisions expected by the Bataille act dead- line in 2006. advisable to optimise the thermal management of the thermo- geneous packages, which put a strain on the cost of such an The relevance of using conditioning specific to a given element installation. It will be necessary to accurately evaluate conse- must be evaluated. quences of a prolonged storage of these packages, enabling their cooling in economical conditions, prior to their permanent Studies on the long-term behaviour of packages, in particular disposal and to then determine the temperature acceptable by of glass packages in disposal situation, must be continued in the host rock, once the site is known. order to confirm the demonstration of safety of geological dis- posal. Finally, according to the actinide partitioning modalities which could be envisaged, it would be advisable to continue the stud- ies on the storage of grouped or partitioned radioactive mate- rials, for example in the case of curium, in order to assess its feasibility and to evaluate its consequences on the fuel cycle.

Model pit for spent -40 m fuel storage

Room 2 8m Room 3

6m

31 m 8,3 m

Fig. 73. Upper part of the storage wells of the CASCAD installation in Cadarache (Bouches-du-Rhône). Fig. 74. Galatée: a demonstration gallery of sub-surface storage suit- able for the long-term, recently constructed on the CEA’s Marcoule site. This 40 metre long structure, with 8 m by 8 m cross-section, shows the components of such a warehouse and the logistics of con- Storage: a pending solution tainer handling. It will be used for thermal experiments in view of the validation of the behaviour models and codes of a concrete structure The most radiotoxic types of radioactive waste, B and C, are subjected to operating hazards, such as the loss of cooling. all stored to date in industrial installations operated by waste producers pending a final destination.

These installations operate without particular difficulties and their projected lifetime is approximately fifty years, with possi- ble extensions beyond this limit.

The studies on long-term storage, carried out within the frame- work of the 1991 act, have identified factors limiting the life- time of such installations, in particular the alteration of con- crete and the corrosion of metals. The risk of neglect by the society remains the intrinsic weakness of such an installation the safety of which, medium and long-term, relies on continu- ous monitoring and maintenance, and on the possibility of Fig. 75. The Galatée facility viewed from outside.

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The storage

Storage is the management mode which makes it possible to await the arranging of an outlet for the final waste.

The durability of the concrete and materials used in the ware- houses, which limits their lifetime, may be the subject of com- plementary studies.

The heat released by some packages puts a strain on the cost of the disposal site. The optimisation of the thermal manage- ment of these packages, is therefore to be undertaken as soon as the disposal site is known.

The issues and the feasibility of the storage of materials orig- inating from an enhanced reprocessing of spent fuel must be evaluated.

Fig. 76. The Galatée facility viewed from inside.

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The fuel cycle of future nuclear systems

The design of the processes involved in the fuel cycle relies or closed cycles with deployment of fast neutron reactors), the on two main determining elements: firstly the choice of a mat- evolution of the quantities of residual heavy nuclei on the one ter management strategy (which must evidently be consis- hand (which is an indicator of resources called into the dis- tent with the capacity of the fleet of reactors to use this matter posal site), and the natural uranium requirements on the other efficiently), and then the fuel object itself (its type, its compo- hand. It is established in an obvious way that the most sition, its morphology): fuel is the backbone of the cycle and its enhanced recycling options are the most effective regarding choice is closely linked to that of processes, involved in its fab- the various components of the sustainability criterion: rication and processing. • The upgrading of the energy potential of uranium 238 and Reflections carried out on 4th generation systems are currently the multiple-recycling of plutonium in fast neutron reactors is still very plentiful, as much for reactors as for their fuels, for of course the key factor for the preservation of resources21; which highly diverse configurations may be envisaged: oxides, carbides, nitrides, in the form of pins, particles, filaments, or • The recycling of plutonium and minor actinides essentially even molten actinide salts. Such a profusion is at this stage contributes to minimizing the residual inventory in fissile absolutely normal, and even fortunate, but does not enable nuclei, the potential noxiousness of waste and also its long- exact orientations to be made for the processes to be imple- term thermogenous character. mented; it will actually be the cycle studies associated with each of these concepts which may and must help decide on The first and main central idea for the cycle thus emerges from the choices in terms of fuel. these reports: sustainable nuclear-power seems to require a recurrent and enhanced recycling of actinides. However, the On the other hand, concerning the matter management strat- egy, a few main orientation elements are already emerging from the reflections of the last few years on the international Worldwide spent fuel level, in particular within the framework of the “Generation IV” Forum. The main expectations and conclusions which seem 700 LWR once through to come out at this stage regarding the research directions to 600 be privileged (also raising numerous questions, which cur- rently remain open) are summarized below. 500

(thousand tonnes) 400 Which material management 300 LWR + fast reactor strategy? 200 100 The criteria which frame the reflection are those which are essential for nuclear systems of the future: sustainability, eco- metal mass Heavy 0 nomic efficiency, safety, are the three main aspects by the yard- 2000 2020 2040 2060 2080 2100 stick of which the forum community has chosen to evaluate the Year various concepts that can be envisaged. Even though the fuel cycle must consider these three issues, the most important Fig. 77a et 77 b. Prospective elements. one is certainly the issue of “sustainability”, whether it con- Water reactors rapidly consume fissile resources and accumulate cerns the preservation of natural resources, the minimisation actinides. Fast reactors do not present these defects. of the environmental impact or the resistance regarding the risks of proliferation.

This becomes quite apparent when reading the graphs in 21. For an explanation of the capacity of fast reactor for efficiently con- Figure 77, presented during the forum’s work. These graphs suming fertile materials such as uranium 238 and therefore for using the indicate for various scenarios (open cycle and water reactors, heavy metal resources, as well as possible, see infra p. 75, the chapter entitled: “On the origin of species (of reactors): systems and generations”.

Nuclear energy of the future: 67 what research for which objectives? MonoCEA GB 5/04/06 15:31 Page 68

Worldwide uranium resource utilization • The importance of retaining compact technologies, in order to reduce investment costs; this aspect becomes important 50 if one choses decentralized processing options, with repro- LWR once through cessing and recycling on the same sites as the reactors. 40 These options avoid the transportation of large quantities of Fast spent fuel but lead to an increased number of plants with reactors (millions tonnes) 30 introduced lower capacities; 2050

20 Speculative resources • Finally, the necessity to favour implementation of “clean” technologies, that is minimising as much as is reasonably 10 Known Fast reactors possible the effluents discharged and the (secondary) tech- introduced 2030 resources nological waste generated 22.

Cumulative natural U Cumulative 0 2000 2020 2040 2060 2080 2100 Year Which recycling processes?

Fig. 77 b. Prospective elements. The worlwide utilization of uranium Again in this field, the reflection may seem plentiful; as indi- resources depends on the type of reactors and fuel cycle, and on cated above, the choice of a cycle process depends on that of when they are put into use. a fuel, and it is obviously too soon to decide on precise options. But in order to orient or frame the reflections, a few general ideas mainly originating from industrial feedback or prospects options remain open regarding recycling scenarios, regarding offered by the advances in research may be brought up. the boundaries of all of the elements to be considered among the transplutonium elements (according to their inventory, their The selective recovery of actinides by use of their physical properties, their impact, the difficulties that their recycling may properties does not seem currently to be taking off as antici- entail); but the general outline seems clearly traced and leads pated in some respects. If indeed the objectives of a partition- to the block diagram in Figure 78. ing of the actinides from all of the fission products is consid- ered, it in fact involves partitioning the heaviest nuclei from the others: this evidence has however not given rise up to now to the enhanced exploration of concepts based on “field effects”

Uranium for spent fuel reprocessing processes.The aim of generalized Actinides recycling of all of the actinides may give fresh impetus to the PF research in this field, but the technological jump will most cer- tainly be significant.

Reactor(s) Therfore, the current reflection is mainly centred around the

Processing potential of “chemical” processes, usually distributed between hydrometallurgical (“aqueous” method) or pyrometallurgi- cal (“dry” method) processes.

The first have to their credit impressive industrial feedback: Fig. 78. Block diagram of the fast reactor cycle. They make use of a mature technology. As shown by the results obtained with the PUREX process implemented in the

This first point being defined, other orientations then emerge from the reflections carried out. Perhaps less obvious or less unanimous, they seem to say a lot about the questions posed: 22. Here we are mainly interested in the management of materials origi- nating from a uranium fuel cycle. The hypothesis of deploying systems bringing thorium into play has been approached during expert meetings • The importance of a grouped management of recycled within the framework of the “Generation IV” forum: in spite of the poten- actinides, which avoids the recovery of isolated fissile iso- tial interests of such systems in some respects (abundance of natural resources, lower generation of radiotoxic heavy nuclei), those do not seem topes.This seems to make the recycling process more resist- to be put forward for the next generation of reactors (with the exception of ant to proliferation (by reducing both the “strategic value” of the options studied of molten salt reactors, for which thermal spectrum breeding with thorium 232 can be envisaged); this essentially relies on the materials for the applications concerned, and their the sustainability of the uranium resources in the hypothesis of an upgrad- “accessibility” thanks to the presence of highly radioactive ing of uranium 238, on the privileged options of recycling all of the heavy nuclei, which reduce the question of the long-term radiotoxicity of the nuclei).This also goes in the direction of improved economic residues, and also on the impact of the accumulated experience regard- efficiency, by simplifying the matter management processes; ing the uranium system.

68 The fuel cycle of future nuclear systems MonoCEA GB 5/04/06 15:31 Page 69

La Hague plant, hydrometallurgical processes procure very high partitioning performances (recovery rate and purification factor of recycled materials) whilst resulting in a low flux of gen- +– – erated technological waste. Cadmium Spent fuel Solid liquid cathode cathode In addition, they appear to offer a large potential to adapt (to fuel characteristics, but also to recycling specifications, as shown in the studies recently carried out on the complemen- Active tary partitioning of minor actinides). They also display undeni- metals able residual progress margins (in particular for increasing U Pu compactness, thus reducing the cost of their implementation). Rare earths They therefore seem to be the benchmark method for the Noble metals development of “advanced” cycle concepts for the fourth gen- Molten salt eration of reactors.

Cadmium Pyrometallurgical processes are currently presented as the main alternative to “aqueous” processes, and are the subject of a renewed development effort on the international level.The Fig. 79. The Argonne pyrochemical an process consists of electroly- generic principle of such processes consists of placing ele- sis in molten salt medium, with partitioning of the elements on the ments to be partitioned in solution in a bath of molten salts various components of the electrolyser. (chlorides, fluorides, etc.) at high temperatures (in the order of several hundreds of degrees Celsius), and then of operating the partitioning of the species of interest via diverse techniques such as extraction via molten metals, electrolysis, or selective Which lines of action for research? precipitation.The interest of this type of process mainly resides in the high solubilisation potential of ionic liquids (in order to Apart from highly diverse exploratory research, which may be dissolve refractory compounds), in the low radiosensitivity of carried out on concepts radically removed from the existing the inorganic salts used (which would enable the “on-line” ones, a few large research avenues are taking shape relating reprocessing of fuels to be envisaged as of their unloading), in to the two main previously mentioned concepts. their compactness (few successive transformation stages can lead to a recyclable product), as well as in the best aptitudes Concerning the hydrometallurgical processes, efforts are presumed for a joint management of the actinides. It is pre- orientated towards the following points: sented moreover as the unavoidable, “natural” process, of online reprocessing of liquid fuels from molten salt reactors. • Firstly, adapting the current process to the characteris- tics of new fuels: this will mainly concern the dissolution of The Argonne 23 (see Figure 79) and Dimitrovgrad teams have the fuel. The reagents and conventional dissolution condi- carried out important developments on such concepts, respec- tions may prove to be unsuitable for certain “advanced” com- tively for the reprocessing of metallic or oxide fuels, up to the pounds. Earlier work carried out on uranium, carbide or creation of pilot installations on which demonstration cam- nitride show however that for such compounds, a quantitative paigns have been carried out. However at this stage strong dissolution is accessible by using the conventional reagent uncertainties remain, the most noticeable concerning the level of the Purex process (nitric acid), and that only minor adjust- of partitioning performances (in particular the actinide recov- ments are to be researched in order to optimize the operat- ery rate) and the implementation on an industrial scale of the ing conditions; technology (secondary waste generated, particularly given the aggressiveness of the operating environments and condi- • The second point resides in the adjustment of the tions). processes in order to enable a grouped management of the actinides: it involves researching the means of extract- ing all of the actinides (major and minor) from the dissolution solution in order to then develop the compound to be recy- cled; this includes the development of molecular architec- tures and appropriate process diagrams, in the continuation of the work carried out during the last decade on “enhanced partitioning” processes; the outline of such a concept, called GANEX, has recently been proposed by CEA (see Figure 23. Argonne National Laboratory. This American research body is super- 80): in a preliminary stage, it is proposed to extract, the main vized by the university of Chicago, for the department of the Energy of the USA (DOE). part of the uranium contained in the spent fuel, then, in a sec-

Nuclear energy of the future: 69 what research for which objectives? MonoCEA GB 5/04/06 15:31 Page 70

ond stage, to partition jointly the plutonium and minor metals for the main part). Encouraged by the potential advan- actinides (neptunium, americium, curium) by implementing tages of these concepts, exploratory studies, laboratory stud- an adapted version of the DIAMEX-SANEX process devel- ies and technological developments have currently been initi- oped within the framework of the studies carried out pursuant ated or revived by various research teams. The results which to line 1 of the December 1991 law; an effort to integrate the will be produced in the next few years will be essential in order recovery and remanufacturing operations for this grouped to best identify their potential, best apprehend the difficult management of actinides to be recycled seems to be, in the points and to orient the following phases of their development. same order of ideas, an orientation to retain; There is still a long way to go before reaching the technical and industrial maturity of such processes. •An important objective also resides in the development of the formulation of extracting agents, in order to increase Independently from the process implemented, the strategic their resistance regarding radiolysis phenomena; this orientations retained for fuels of the future raise a certain num- would offer the possibility of reprocessing barely “cooled” fuel; ber of questions, the relevance and intensity of which will depend finally on the options which will be fixed, but which • Finally, the technologies and their implementation con- already have to be considered at this stage. Below, non- stitute a determining research avenue to increase the com- exhaustively, a few examples: pactness of the processes, whether they concern single tech- nologies (where remarkable progress margins have already • The concern for a “close” retention of fission products in reac- been obtained with the development of liquid/low stay time tor fuel, which leads to cladding or elaborated encapsulation liquid contactors) or their integration (advances in the field of devices being envisaged (particle fuels for example) may online control seem to be important factors for the simplifica- modify the accessibility of the materials to be recycled dur- tion of industrial workshop architecture). ing reprocessing stages; new objects, new materials must be associated with suitable destructuration concepts;

• These matrix materials must obviously be managed: accord- ing to their abundance and the nature of the destructuration

Irradiated processes, their presence may increase the complexity of fuel recycling operations;

Actinides Dissolution • The option of an “integral” recycling of actinides certainly to be recycled leads to final waste with reduced toxicity. In counterpart, it entails a “hotter” recycled fuel, which will require remote oper- Preliminary U U partitioning ated remanufacturing processes; U + Pu + MA

Coextraction Disextraction Disextraction •Particular attention is to be paid to the management of cycle An + Ln An Ln effluents for some fuel options (carbon-14 with nitride fuels FP Ln for example) or installation options (liquid discharges obvi- ously entail more constraints for a recycling option on the reactor sites); Waste

• According to some experts, one could also try to reduce the Fig. 80. A grouped actinide extraction concept: GANEX. costs of final waste disposal by removing particularly ther- mogenous fission products (Caesium 137, Strontium 90, see Fig. 81) from the waste.This option adds some complexity to In the field of pyrochemical processes, the main objective of the processing operations, but could take advantage of the the research to be carried out resides in the confirmation of additional freedom that intermediate storage may provide. It the potential of such concepts for industrial spent fuel deserves at least some studies, in the general framework of recycling operations. Although absolutely significant devel- the optimization of the back-end of the fuel cycle. opments and experiments have been carried out over a long period of time, few results currently concern the recovery of plutonium and, all the more so, minor actinides, and also the management of spent salts. A great number of avenues cur- rently remain open, concerning both the choice of reactional media (fluorides or chlorides, but also “room temperature” ionic liquids, which are currently experiencing important growth), and that of technologies (electrolysis or extraction by molten

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Residual power (W/TWhe)

10,000.0 Pu (reproc. at 4 years) Am (reproc. at 4 years) Cm (reproc. at 4 years) 1,000.0 Fission product Cs Sr 100.0

10.0

1.0

0.1 10 100 1,000 10,000 100,000 Cooling time (years)

Fig. 81. Contribution of the various radionuclides with the residual power released by spent fuel (UOX, 55 GW.j/t).

To summarize...

The orientations outlined for the nuclear systems of the future The magnitude of the field of research to be carried out shows give considerable importance to the fuel cycle operations (in all the interest of an organized international cooperation, such particular regarding the range of materials to be recycled).We as is currently being established within the “Generation IV” shall have to process new fuels, in a probably reinforced field Forum. of economical and environmental constraints. This multiple challenge calls for innovations and must be dealt with as a Finally, as was reported during the forum’s expert meetings, it whole: the entire chain of reactors, fuel and cycle, must is necessary to take into consideration the fact that the deploy- progress coherently. ment of 4th generation reactors may only intervene progres- sively, and that the 21st century fleet will present a large com- Two large avenues currently seem to be preferred: firstly ponent of water reactors, the cycle installations of which will hydrometallurgical processes, strengthened by consistent also have to manage spent fuel, in order to produce final waste industrial feedback which attests their potential, and which still compliant with the specifications and criteria which will prevail, appear to have important margins of adaptation and progress; and in order to supply new generation reactors: this “symbi- and then the pyrometallurgical processes, promising in some otic” character of the fleet will also constitute important input respects, but the potential of which are to be further explored. data for future choices.

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Uranium resources

The element uranium the RAR reserves currently estimated. Of these 2 million, only a part has been consumed in civilian reactors, leaving on the Uranium is the heaviest of the natural elements remaining on order of 1.2 million tonnes of depleted uranium with approxi- 24 Earth . Natural uranium mainly consists of two isotopes: U 235 mately 0.3% of U 235 which can be considered as a strategic and U 238. reserve for the future. At the current rate of consumption (approximately 60,000 tonnes per year), “cheap” reserves Isotope Period (years) Current relative abundance on earth should last between 50 and 100 years. Beyond this horizon, (in % U total) the millions of tonnes of uranium contained in phosphates and 235 713 millions 0.72 the billions of tonnes contained in the water of the oceans (the 238 4.47 billions 99.275 content is 3 parts per million) could be exploited.

In reality, the future of the “uranium” resources will depend a This isotopic composition of natural uranium is found every- great deal on the fuel cycle of the reactors which use them. where on Earth25, no physical or chemical process having led Uranium is used quite unefficiently in water reactors: the to a significant separation of the two isotopes. extraction of approximately 200 g of natural uranium is neces- sary in order to obtain the fission of 1 gram of material in this Uranium enters into the composition of at least two hundred type of reactor. If one continues to use uranium in “open cycle” minerals, and its average content in the earth’s crust is approx- light water reactors, the uranium reserves may seem modest imately 3 grams per tonne. It is present in practically all of the in relation to those of fossil fuels. However, a single recycling, rocks of the Earth’s crust, with particular concentrations in notion without significance for fossil fuels, already significantly phosphates, certain igneous rocks or in the vicinity of oxida- increases the scope of the resources. In parallel, the use of tion-reduction boundaries in sedimentary rocks. Uranium is fast neutron reactors would enable the energy potential of the generally extracted from the subsurface by conventional uranium to be better used by efficiently consuming the fertile hydrometallurgical and mining techniques. isotope U 238 in a closed fuel cycle26. With these nuclear sys- tems, the resources would no longer be a matter of concern. Uranium resources

Today, most of the uranium produced in the world comes from Canada, followed by Australia and Nigeria. Large deposits of high-grade ore are yet to be to be exploited in Australia and Canada. Global reasonably assured resources (RAR), that can be recovered at a cost lower than $80/kg uranium, amount to approximately 2.5 million tonnes. Of course, resources depend on the price that one agrees to pay in order to recover them: thus, RAR resources that can be recovered for less than $130 per kg of uranium are estimated at 3.3 million tonnes.

How vast are these reserves? By way of comparison, 2 mil- lion tonnes of uranium have been produced since the begin- ning of the nuclear power industry, that is a quantity close to

Fig. 82. An open-cut uranium mine. 24. Tiny quantities of “natural” plutonium are found in uranium ore. This plutonium is formed by absorption of neutrons produced by the sponta- neous fission of uranium, 25. With the exception of the Oklo deposit, where natural nuclear reac- 26. See supra and infra, pp. 67 and 75, the chapters entitled: “The fuel tions took place which consumed uranium 235 and disrupted the isotopic cycle of future nuclear systems” and “The origin of species (of reac- composition of the remaining uranium. tors)…”.

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Unit: Billion of toe

Spain 3.1 France Russia (0.3 %) 12.5 140.9 (0.5 %) Kazakhstan Canada Algeria (5.6 %) 26.0 436.6 326.4 (17.4 %) (13.0 %) (1.8 %) Ukraine 42.6 (1.7 %) Mongolia 61.6 (2.5 %)

United States 106.0 (4.2 %) Australia Nigeria 607.0 71.1 (24.2 %) (2.8 %)

Brazil 162.0 (6.5 %) Gabon 4.8 (0.2 %)

Other Namibia South Africa 123.4 149.3 232.9 (4.9 %) (6.0 %) (9.3 %)

World total: 2,506.2 billion tonnes (excluding Chile et China) Source: Energy observatory at CEA/DES and IEA/OECD

Fig. 83. Proven global reserves of uranium* (1.1.1999). * Reasonable resources assured recoverable for less than $ 80/kg U.

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On the origin of species (of reactors): systems and generations

« If any species does not become modified and improved in a correspon- ding degree with its competitors, it will • In slow neutron or “thermal” reactors, the neutrons are soon be exterminated. » slowed down by successive collisions on the light nuclei of a

Charles DARWIN, On the Origin of Species by moderator material. The main moderator materials used are Means of Natural Selection, 1859. ordinary water, heavy water (D2O) and graphite. As slow neu- trons have large interaction probabilities with the material, this type of reactor may operate with a fuel little enriched with fissile nuclei (natural uranium may even possibly be suffi- Nuclear reactor design begins by the layout in the reactor cient), but only a small part of the energy from the fuel’s core of fissile and fertile materials constituting the fuel, a heavy nuclei is exploited. A lot of these heavy nuclei are coolant used to evacuate the heat produced by the fission transmuted by neutron capture in actinides that will be found reactions, a moderator (possibly) which slows down neutrons, present in the waste; and a neutron absorber to control the chain reaction. Several options are possible for each of these elements, and, while all •In fast neutron reactors (FR), the neutrons are not slowed of the combinations are not viable, many types of reactor can down in the reactor, and they more or less keep the energy be envisaged. that they had during their production by fission. Their inter- action probabilities with the material are low, this is why fast neutron reactors must have a high neutron flux, and contain Fissile and fertile materials a lot of fissile material. On the other hand, in this field of neu- The most commonly used fissile nucleus in current reactors is tron energy, fission reactions are favoured in relation to par- U 235, a single “natural” fissile isotope. Other fissile nuclei that asite (capture) reactions: Fissile material is used much bet- can be used are the odd plutonium isotopes Pu 239 and ter than in a thermal neutron reactor. FRs are potential Pu 241, produced by neutron irradiation of the fertile isotope burners of actinides, the latter being fissile with fast neutrons. U 238. The mixture of fissile and fertile isotopes in the core enables the operating time of the core to be increased, since the disappearance of fissile nuclei by fission is partially com- pensated (or totally if the reactor is a breeder reactor*) by the Fission Capture formation of new fertile nuclei via neutron capture on the fer- 1e6 1e5 tile nuclei. 1e4 1,000 100 Coolant 10

Cross section (barns) 1 Many choices are possible for the coolant fluid: heavy water, 0.1 0.01 Slow neutrons Fast neutrons ordinary water, gas (helium, CO2), liquid metals, etc. The 0.001 coolant may circulate directly from the core to the turbine or 1e-4 exchange heat with a secondary circuit.The choice of coolant 1e-5 has a great importance in the reactor’s technology, and large 1e-5 1e-40.001 0.01 0.1 1 10 100 1,000 1e4 1e5 1e6 1e7

systems are often classified according to it. Neutron energy (eV)

Fig. 84. The fissile and capture cross-section* of uranium 235 as a Moderator function of the energy of the neutron highlights two main fields: that of slow neutrons, where the interaction probabilities of the neutron Another fundamental choice is that of the mean energy, or with the uranium nuclei are high, and that of fast neutrons, where the mean speed of the neutrons in the core. The choice between cross-sections are much smaller. fast neutrons and slow neutrons thus determines two main groups:

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Current reactor families RBMK graphite - water reactors In the 1950s and 1960s, practically all nuclear reactor types It was this type of reactor which caused the Chernobyl acci- were envisaged, designed and even built! Following this bee- dent. The graphite moderator is penetrated by zirconium alloy hive of creativity, “natural” selection ensured the survival of a pressure tubes in which the boiling water circulates in order to reduced number of families. cool the slightly enriched uranium fuel. This type of reactor is unstable in its design in certain operating domains, which makes it vulnerable to human error.The complete shutdown of Gas reactors this reactor family is programmed. Graphite-gas reactors enable the use of natural uranium.They developed in many countries (United Kingdom, France, Japan, Spain, Italy) until the United States, which up to the end of the 1950s maintained the monopoly on enrichment, agreed to export enriched uranium. From then on, all of these countries progressively abandoned this technology in order to switch to the light water reactor type.The last was the United Kingdom, which started its first water reactor in 1995, and is the only one to keep reactors of this type in operation today.

Fig. 86. A RBMK reactor (unit no. 4 at Chernobyl).

CANDU heavy water reactors

Fig.85. 1st to 2nd generation reactors: the large NUGG reactor (shut In this type of reactor, the fuel is cooled by the circulation of down) and the small PWRs (in service) which succeeded it can be heavy water in the pressure tubes. The heavy water modera- seen on the Bugey site. tor absorbs very little of the neutrons, which enables this type of reactor to use natural uranium. This specificity may attract countries wishing to free themselves of uranium enrichment. Ordinary water reactors The Canadians exported CANDUs to many countries (India, With 86% of the fleet in operation and 79% of constructions in Pakistan, Romania, Korea, China). progress throughout the world, ordinary (or “light”) water reac- tors represent the worldwide dominant species of nuclear The systems of tomorrow reactors. Even if water reactors are currently dominant, several types of PWRs, and their Soviet version, the VVER, are the most com- reactor have specific advantages that may one day compete mon.They are robust, reliable, and display continued progress with them: in terms of availability, burnup rate, cycle time, ability to follow fluctuations of the power grid and collective dose to operators.

Boiling water reactors (BWR), which represent approximately High temperature reactors (HTR) a third of the capacity of PWRs, have also seen significant HTRs are thermal neutron reactors, moderated by a large development, but have been slightly hindered by a few teething mass of graphite and cooled by helium circulation.They use an defects. Today, in Japan, the last orders have exclusively con- original fuel, the “coated particle” initially designed in England. cerned boiling reactors. This fuel, made from carbon and ceramic enables high refrac-

76 On the origin of species (of reactors): systems and generations MonoCEA GB 5/04/06 15:31 Page 77

tory cores to be made, operating at high temperatures, which In thermal spectrum reactors, actinides often capture neutrons offers the possibility of high efficiency thermodynamic cycles. without fissioning, which leads to the formation of heavier and The great freedom offered to the designer via the particle fuel heavier nuclei, all radioactive, which put a strain on the neutron makes this type of reactor suitable for accommodating a large inventory of the reactor and is found in waste. variety of fuel cycles. In fast spectrum reactors, capture and fission coexist for all of Several HTR prototypes have been developed in the United the actinides, which offers the possibility of balancing their States and in Germany. Made attractive by the recent progress inventory. in gas turbines, they are currently studied in the form of small modular reactors cooled by a helium circuit coupled directly to Still by way of comparison, a typical UOX-PWR (1GWe) 16 kg a turbine. With their large thermal inertia, HTRs are particu- of minor actinides. The recycling of Pu in the MOX form larly safe, which may permit their safety systems to be simpli- enables the Pu inventory to be stabilized, but the minor fied; their excellent thermodynamic efficiency should make it actinides are not burned and build up. A FNR replenisher of possible to amortize their investment cost rapidly, a cost which the same power can consume the minor actinides that it pro- is still high due to their low power density. duces 27 (see the block diagram of the FNR fuel cycle in chap- ter N). With this type of system, nuclear power may therefore gain in cleanliness. Fast neutron reactors (FR) The only FRs on which we have significant feedback are the The great advantage of fast neutron reactors resides in their ones cooled by liquid sodium.This is an excellent coolant, not ability to produce as much or more fissile material than they very corrosive for stainless steels when it is pure, but which consume. Fast neutron breeder reactors may therefore, via spontaneously ignites with air and reacts quickly with water. successive recycling, use the quasi-totality of the energy con- tained in the uranium, one hundred times more than an ordi- The Russians are studying FR models cooled with molten nary water reactor. lead, whereas the French are reopening, the helium-cooled FRs file after shutdown of the Superphénix 28.

The investment cost of FRs is much higher than that of PWRs e° with the same capacity. FRs therefore only have a chance to emerge if – or when – their specific quality, fissile material U 238 U239 Np239 Pu239 economy, becomes a key factor of success. n 23.5 min 2.35 Tage e° In a more distant future

Fig. 87. Formation of a plutonium 239 (fissile) nucleus via capture of To complete the list of possible future reactors, it is finally nec- a neutron on uranium 238 (non-fissile). essary to mention the molten salt reactors and the “ADS” The fission of a nucleus produces several neutrons. Only one of (Accelerator Driven Systems), hybrid reactors coupled with a these neutrons is necessary to maintain the chain reaction. The proton accelerator. Nuclear technology is young, and there is other neutrons may form other fissile nuclei via capture on uranium no lack of ideas to adapt it to new global requirements in terms 238 in order to form plutonium 239. With a replenisher or breeder reactor, as much or more fissile material can be produced than con- of energy and environment. What is certain, is that sustain- sumed. able nuclear power will only exist within the framework of a The fissile material therefore plays the role of a catalyser, constantly responsible radioactive waste management and fissile and fer- regenerated during its consumption. With this type of reactor, it is the tile material recycling strategy. fertile material U 238, which is in fact finally consumed.

By way of comparison, a typical UOX-PWR (1GWe) needs 110 t of natural uranium per year and produces 0.25 t of plu- tonium per year.A FNR replenisher of the same power would need 15 to 20 t of Pu (constantly regenerated), and would consume only approximately 1 to 2 tonnes of natural ura- nium per year. FNRs may even operate using the large stock of depleted uranium currently unused by the water reactor fleet. FNRs therefore solve the problem of resources.

27. See supra, p. 68, the block diagram of the fast reactor cycle. 28. In Creys-Malville (Isère).

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SCWR MSR VHTR GFR FNR FNR 2040 Na Pb Tomorrow EPR

2005 BWR Today (Boiling water Civilian SGHWR PWR CANDU reactor) (Steam AGR HTR generating) RBMK Naval (graphite propulsion WPu moderator and FR ADS MSR 1986 water coolant) (Fast (Molten Chernobyl WPu neutron salt) reactor) Magnox (Graphite-gas reactor)

1973 1st oil shock WPu

Naval PWR + fuel 1960 reprocessing U enriched Blossoming Heavy water Graphite

Gen.I Gen.II Gen.III Gen.IV reactors of the reactor reactors moderator concept reactors

1942 The beginning The nuclear reactor phylum Fermi Joliot-Curie

Fig. 88. The phylogenetic tree of nuclear reactors. But the selection criteria are changing, the world is evolving. Brief description of the main branches of the tree: reactors may Other species are emerging. The six concepts retained by the Gen operate with natural uranium or enriched uranium, but the use of nat- IV are at the top of the tree. Will they all be developed? ural uranium restricts the choice of coolants to graphite and heavy water. The use of enriched U offers almost all possible choices of • WPu: Military plutonigenous reactor. coolants and moderators. Some combinations are more fortunate •SGHWR: Heavy water reactors supplying industrial heat than others: the water coolant has had a lot of success, because it is (Steam Generating Heavy Water Reactor). also a good moderator. Water reactors (PWR and BWR) constitute •AGR: Graphite-gas reactors (Advanced Gas-cooled Reactor). most of the contingency of generations II (current) and III (near • (V)HTR: (Very) High Temperature Reactor. future) reactors. • SCWR: Super Critical Water Reactor. The combination of a graphite moderator and a gas coolant paves • ADS: Hybrid spallation-fission system (Accelerator-Driven System). the way to high temperature reactors. • FR: Fast Reactor. The branches of fast neutron reactors are still little developed. • MSR: (). Only certain species of nuclear reactor have survived. Some branches are extinct or in the process of becoming extinct: NUGGs for economic competitiveness reasons, for safety reasons.

78 On the origin of species (of reactors): systems and generations MonoCEA GB 5/04/06 15:31 Page 79

Systems of the future

Advanced reactors Current reactors First creations

Generation I

UNGG Generation II CHOOZ PWR 900 Generation III PWR 1300 N4 EPR Generation IV

Fig. 89. The nuclear generations calendar.

Petite histoire des générations nucléaires

• The first generation of reactors saw the day feedback and industrial maturity of second genera- when the industrial technology of uranium enrich- tion reactors, whilst integrating even more ment was not yet developed. Reactors had to be advanced specifications in terms of safety. able to operate with natural uranium (non- enriched), hence the use of moderators absorbing • Finally the development of the fourth generation very few neutrons, such as graphite or heavy water. has as from now been engaged, within an interna- This is why the field, called Natural Uranium tional framework and with the objective of bringing Graphite Gas (NUGG), was developed in France. these new systems to technical maturity, with the prospect of industrial deployment by 2030.The pur- • The second generation of reactors, deployed in pose of these systems is to respond to the issues the 70s to 90s, constituted most of the global fleet of sustainable energy production, with a long-term currently in operation. This period was that of pres- vision, and in particular, to minimise radioactive surized water reactors PWRs and boiling water waste and to better use natural resources of fuel, reactors BWRs. The cumulated operation of more as well as to meet new energy requirements: not than 10,000 years-reactors on the global level only the generation of electricity, but also hydrogen proves the industrial maturity and the economic for transportation and drinking water via the desali- competitiveness of this technology. The fleet of 58 nation of seawater. pressurized water reactors that France has belongs to this second generation. These systems present significant evolutions and technological innovations (they can be called “rev- • The third generation represents the most olutionary”) which require approximately twenty advanced industrial state-of-the-art. It concerns so- years of development called “evolutionary” reactors which benefit from the

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Nuclear systems of the future: an international framework for the development of a new generation of nuclear systems

The Generation IV International Forum France United Kingdom

The objectives targeted for the systems of the future, as well Canada as the choice of key technologies to achieve them, are the sub- European Union ject of a very active international cooperation, in particular USA within the framework of the Generation IV Forum. Members Switzerland Taking stock of the risks of shortages and medium-term energy Brazil of the dependence, the American government has committed itself Generation IV to an effort to revive the means of generating electricity. In the international field of nuclear energy, this results in two complementary Japan actions: Argentina

• The first is purely American, and intends to facilitate the con- South Korea struction of new reactors in the United States in the short term (2010); it concerns the Nuclear power 2010 (NP 2010) South Africa programme. An ad hoc group, the Near Team Deployment Group (NTDG), has evaluated the reactors likely to be con- Fig. 90. Nuclear systems of the future: highly international R&D. structed between now and 2010, has identified the possible problems to be solved on the technical, regulatory or admin- Methodology of the choice of technological istrative level, and has proposed actions facilitating the short- orientations term deployment of these third generation nuclear reactors;

• The second is the Generation IV International Forum. Its Three steps have already been taken: founding principle is the recognition of the advantages of nuclear energy by the ten member countries. This energy • The evaluation of designs proposed by the participating could meet the growing energy needs throughout the world, countries, according to a highly codified methodology (this in a procedure for sustainable development and prevention of task was carried out between April 2001 and April 2002); the risks of climate change. This principle is recorded in the Forum’s charter, and it is embodied by the commitment of an • The selection of a small number of leading technological con- international R&D to define, develop and enable the deploy- cepts judged as particularly promising during the evaluation ment of 4th generation nuclear systems by 2030. The mem- (task carried out in May 2002); ber countries of the Generation IV International Forum are Argentina, Brazil, Canada, France, Japan, the Korean • The elaboration of a development plan for these technologies, Republic 29, South Africa, Switzerland, the United Kingdom, published in October 2002, preparing a later phase of interna- Switzerland, the United States and the European Union. tional cooperation (main objective of the Forum from 2003). Other countries or international instances may also eventu- ally join this research effort. Straightaway, a clear agreement was affirmed among the par- ticipants on the main objectives of the Generation IV pro- gramme and on the procedure. Four main objectives (“goal areas”) were defined in order to characterize the systems of the future. They must be:

• Sustainable: this means saving natural resources and respecting the environment (by minimising the production of waste in terms of long-term radiotoxicity, and by optimally 29. South Korea. using natural fuel resources);

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• Economical: from the point of view of the investment cost technical groups’ activity and assured the integration of the per kWe installed, the fuel cost, the operating cost of the results in the documents of the various stages and in the final installation and, consequently, the production cost of the summary. kWh, which must be competitive in relation to that of other energy sources; The choices made within the Forum

• Safe and reliable: with ongoing research in relation to cur- Six nuclear systems were selected, which may enable notable rent reactors, and by eliminating the need to evacuate the pop- advances on the abovementioned criteria. These systems ulation outside of the site as much as possible whatever the enable applications other than electricity production, such as cause and the gravity of the accident inside the power plant; the generation of hydrogen or seawater desalination.

• Resistant regarding the risks of proliferation, and easily The diversity of needs to be covered and the international con- protected against external aggressions. texts explain that we do not end up with only a Generation IV system, but with a few of the most promising system designs, Approximately one hundred engineers and scientists have par- on which the Forum R&D member countries are now concen- ticipated in the first phase of the Forum’s work. For each system trating. considered (e.g. water, gas, liquid metal reactors) technical groups have been made responsible for the evaluation of the various concepts proposed in relation to the objectives and cri- Identity cards of the selected teria retained, and these groups were also responsible for the systems elaboration of R&D plans for the concepts finally selected. The The selection operated in the Generation IV initiative shows evaluation methodology was developed and refined by a spe- several important lessons: cific workgroup which reduced the four main progress objec- tives mentioned above to approximately thirty basic criteria. • In the choices retained the most discriminating criteria were those of sustainable development. The range of evaluations Transverse technical groups identified the necessary develop- on the economical or safety aspects turned out to be much ments in the field of fuel, the cycle procedures, the materials, more narrow. This results in a majority of fast spectrum and and the safety of the energy products for the various systems closed cycle systems; considered by the Forum. A coordination group led all of the • The most innovative concepts find themselves penalised by great uncertainties regarding their definition and regarding the possibility of removing technological difficulties for a pro- Five basic criteria duction between now and 2040. In this class of nuclear sys- tems, the final choice falls on the molten salt reactor, interest- ing for the management of actinides and the deployment of Saving Economy the thorium cycle; natural resources • The grouping into groups of reactors – homogenous from the Safety Extracting the energy performances and R&D requirements point of view – proved from fissile material efficiently to be important because it enabled the R&D knowledge Reduction bases to be taken into account and recommendations Reducing of the production around important federal policies to be structured. By way of the risk of waste example, the gas-cooled group of reactors (RCG), comprizes of proliferation Recycling Burning plutonium and transmuting an important research knowledge base regarding high tem- with an integrated minor actinides perature materials, helium circuits, and conversion by gas fuel cycle turbine. In addition, different variants are being studied for various market niches: very high temperature reactors for the Fig. 91. The criteria retained for the selection of nuclear systems mass production of hydrogen, specialized reactors for burn- of the future differ in their name and in their hierarchy from those ing actinides, fast neutron spectrum version and integral retained for first and second generation reactors. recycling for sustainable ; Here, all of the criteria were placed on the table, and debated in the greatest transparency.They are all of purely civilian inspiration, and shared by the international community. • The various gas reactors (GFR, VHTR) translate the recog- The profitability and economy criteria of the resources (important for nition of the interest for this coolant with, in particular, the industrialists) remain important. More innovative, the safety, waste possibility that it offers for developing an upgradeable range reduction (important for the public) and reduction of proliferation risks of systems based on this technology. (important for politicians) criteria are explicitly mentioned.

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SFR: “improved sodium” intermediate unit power of 150-500 MWe • the second, characterized by a repro- cessing of mixed oxide fuel (MOX), cor- responds to a reactor with high unit Steam generator power, between 500 and 1,200 MWe (reactor associated with PUREX repro- cessing). Cold plenum Turbine Generator The SFR presents very good natural resources usage and actinide manage- Hot plenum ment properties. It was evaluated as hav- Control rods Electrical ing good safety characteristics. power The oxide fuel system may be ready for Condenser industrial deployment as of 2015. Heat exchanger Several SFR prototypes exist throughout the world, in Japan (Joyo, Monju), Russia Heat sink (BN600), and France (Phénix). Primary Pump sodium The main research issues concern the (Hot) Secondary sodium integral recycling of actinides (fuels com- prizing actinides are radioactive, therefore Pump Pump complicated to manufacture); the in serv- Core ice inspection (sodium is not transparent); Primary sodium safety (passive safety procedures are (Cold) being studied); the reduction of the invest- ment cost (this type of reactor is still expensive). The changing of the water of

the secondary fluid for supercritical CO2 is Fig. 92. SFR: “improved sodium”. material in the core, this type of reactor also being studied, because it may enable This system includes a fast spectrum may operate for a very long time without the safety to be improved, whilst allowing reactor associated with a closed cycle intervention on the reactor core. the elimination of the intermediate sodium enabling the recycling of all of the Two main options are envisaged: circuit, if the chemical sodium-CO2 inter- actinides and the regeneration of pluto- • the first, associated with a reprocessing actions proves to be less violent than nium. Due to the regeneration of fissile of metal fuel, leads to a reactor with an sodium-water interactions.

Fig. 93. LFR: “a lead concept”. LFR: “a lead concept” This system comprizes a fast neu- tron reactor associated with a closed fuel cycle, enabling optimal use of the uranium. Electrical Several benchmark systems have Generator power been maintained in the selection. The unit powers go from 50-100 Header MWe, for the so-called “battery” con- cepts, up to 1,200 MWe, including the modular concepts from 300-400 U-tube heat Turbine exchanger MWe. The “battery” concepts have a modules long-term fuel management (10 to Recuperator 30 years). The fuels may be either Reactor metal, or of the nitride type, and module/fuel enable the recycling of all actinides. cartridge Compressor (removable) The main technological deadlock of the system concerns corrosion by Heat sink liquid lead. Coolant module

Intercooler Pre-cooler Coolant Compressor Reactor core

Reactor

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Fig. 94. SCWR: “water, but supercritical” SCWR: “water, but supercritical” Two fuel cycles are envisaged for the SCWR, which correspond to two different Control versions of the system: a thermal spec- rods trum reactor associated with an open fuel Supercritical water cycle and a fast spectrum reactor com- bined with a closed cycle for recycling all the actinides. Both options have an identi- cal operating point in supercritical water: pressure of 25 MPa and core outlet tem- Electrical perature of 550° C enabling a thermody- Turbine Generator power namic efficiency of 44%. The unit power of the benchmark system is 1,700 MWe. The SCWR was evaluated as having high

potential for economic competitiveness. Reactor core The main research issue concerns corro- sion by water, in particular accelerated in Condenser relation to current water reactors due to a much higher operating temperature. Reactor

Heat sink

Pump

VHTR: “making hydrogen with helium?” Fig. 95. VHTR: “making hydrogen with helium?” The VHTR is a gas-cooled system associ- Control ated with a thermal spectrum core and an rods Graphite reactor open fuel cycle. The particularity of the core Pump VHTR is its operation at very high tempera- tures (>1,000° C) to supply the necessary heat for water decomposition processes by Graphite reflector thermal chemical cycle (iodine/sulphur) or high temperature electrolysis. The VHTR is dedicated specifically to the production of hydrogen, even if it must also enable the generation of electricity (alone or in co-generation). Water The benchmark system has a unit power of 600 MWth and uses helium as a

Blower coolant. The core is made up of prismatic Oxygen blocks or pebbles. Important research topics for the develop- Heat sink ment of this system concern high temper- Reactor Helium ature materials and the development of coolant Hydrogen hydrogen mass production technologies. Heat Hydrogen production exchanger plant

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Fig. 96. GFR: “fast gas” GFR: “fast gas” The GFR is a fast spectrum system enabling the homogenous recycling of actinides whilst maintaining a regeneration gain greater than 1. The benchmark con- Generator Electrical cept is a helium-cooled once through reac- power tor with high efficiency (48%). The evacua- tion of the residual power in the event of Helium depressurisation implements natural con- vection. The power density in the core is Turbine determined in order to limit the transient temperature of the fuel to 1,600° C. The innovative fuel is designed to retain fission products (for a temperature lower than the limit of 1,600° C), and to avoid their release in accident situations. The recycling of spent fuel is envisaged on the same site as Recuperator

the reactor either via a pyrochemical Reactor core process or via a hydrometallurgical process. The GFR is the most performant concept in terms of natural resource usage and reduction of long-term waste. It is located in the technological gas line, com- plementing thermal spectrum concepts, GT-MHR30 , PBMR31 and VHTR. Heat sink Heat sink The main research topics associated to the Reactor Intercooler Pre-cooler development of the GFR concern the reac- Control tor materials, which must be able to resist rods both high temperatures and strong neutron Compressor irradiations. The most important issue is the development of a dense and refractory fuel.

MSR: “a 2 in 1 system” Fig. 97. MSR: “a 2 in 1 system” The MSR is an epithermal spectrum sys- tem with the highly original implementa- tion of a molten salt solution used both as Control rods fuel (liquid) and coolant. The regeneration of the fissile material is possible with an Coolant salt optional uranium-thorium cycle. The MSR Reactor Generator Electrical integrates in its design an online recycling Purified salt power Heat of fuel, and thus offers the opportunity of exchanger grouping on the same site electricity gen- erating reactor and its reprocessing plant. Turbine The salt retained for the benchmark con- cepts (unit power of 1,000 MWe) is a sodium, zirconium and actinide fluoride. Recuperator Pump The spectrum moderation is obtained in Chemical the core by the presence of graphite processing plant blocks crossed by the fuel salt. The MSR Freeze comprizes an intermediate fluoride salt plug circuit and a tertiary water or helium cir- Heat sink Pump cuit for the generation of electricity. This

Pre-cooler system was evaluated as having relatively good safety and non-proliferation charac- teristics. Emergency dump tanks The most important research issue con- cerns the development of the online Intercooler Compressor molten salt fuel recycling technology.

30. GT-MHR : Gas-Turbine Modular High Temperature Reactor. 31. PBMR : Pebble Bed Modular Reactor.

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The second stage of work from the Forum is the international What research for the nuclear co-operation phase to consolidate systems feasibility by systems of the future? removing technological deadlocks and validating their perform- ances. It is currently being established and France is playing Research on nuclear systems of the future must be based on a very active role. The systems, whose feasibility is to be con- a quality modelling. The basic physical phenomena are firmed, will enter into a validation phase of their technical and mostly well-known, which does not signify that their modelling economic performances. is easy!

According to the degree of innovation of the system, all this Fortunately, the progress of computer tools enables ambitious work should lead to sufficient technical maturity between 2015 modelling to be envisaged. A new generation of calculation and 2025. It should enable important industrial deployments codes is in the process of development in order to describe by 2040. the behaviour of nuclear systems: these software platforms use a “multiscale” (from microscopy to macroscopy) and multi- disciplinary (taking into account the interactions between neu- tronics and thermohydraulics, for example) approach.

In reactors of the future, the materials in general and the fuel in particular will be subjected to severe conditions, due to the high temperatures envisaged in certain reactor concepts, and

International initiatives complementing the Generation IV International Forum

INPRO The European MICANET and HTR-TN networks In 2000, the International Atomic Energy Agency (IAEA) The objective of the European MICANET network launched the INPRO project (International Project on (MICHELANGELO Network) is to develop a European R&D Innovative Nuclear Reactors and Fuel Cycles), which aims to strategy in the field of innovative systems and to contribute in promote the development of innovative nuclear systems defining projects from the 6th European R&D Framework enabling future energy requirements to be met whilst respect- Programme in relation to the Generation IV Forum’s activity to ing the objectives of economic competitiveness, safety, respect enable exchanges best serving the interests of European play- for the environment, resistance to proliferation, and acceptance ers.The HTR-TN network is more specifically dedicated to gas- by the public. cooled systems.

The importance of this project is to accompany and comple- Bilateral cooperations ment technological developments, such as those carried out The bilateral cooperation actions with the United States, Japan within the framework of the Generation IV Forum, there where and Russia were redefined in 2001 with the aim of preserving IAEA may have a specific contribution, for example by enabling a growing place for joint studies and developments regarding the participation of numerous countries, in particular develop- the gas reactor technology, the extrapolation of this technol- ing countries not yet using nuclear energy but interested in ogy to fast neutrons, and the development of fuel reprocessing benefiting from it, or thanks to its effectiveness in non-prolifer- and remanufacturing processes, with integral recycling of ation and international controls. actinides.

Firstly (phase 1), the technical objectives of the project are: The cooperation with the United States carried out since 2002 to work with five common joint-financed projects on these top- •To determine, over a very large basis, the needs and objec- ics (NERI-International actions within the framework of the tives of countries, given the diversity of their situation, and to CEA-DOE cooperation). Eventually, four of these projects may specify how innovative nuclear systems may contribute to integrate Generation IV cooperation. meeting them;

•To define the criteria and methodologies for the analysis and The cooperation with JNC (Japan Nuclear Cycle Development comparison of various innovative reactor concepts. Institute) enables the comparison between the gas-cooled and sodium-cooled fast neutron reactors to be extended, as well Secondly (phase 2), the Agency envisages that the project may as the sharing with JAERI of certain technological develop- extend the definition of the criteria and the evaluation method- ments (fuels, materials) and experimentation possibilities on ology in order to help member countries of the Agency in their their experimental helium-cooled HTTR reactor. own analysis of nuclear systems that best meet their needs. Different from the Generation IV Forum, the purpose of the project is not to carry out technical R&D actions or to develop innovative reactors and systems.

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caused by irradiation by the high flux of 2000 2010 2020 2030 2040 2050 2060 2070 2080 fast neutrons. Corrosion is in general accelerated at high temperatures, and Ganex on spent this topic represents a research subject LWR fuel (MOX et UOX) in itself. Irradiation damages caused U in the materials by fast neutrons are Gen. II qualitatively different from those caused Pu

by slow neutrons, because of the pos- Recycling Pu (U) of the Pu in Gen. sibility that the former have of produc- U III the LWR (MOX) ing nuclear reactions. Refractory alloys and ceramics, solid or composite, are U, Pu, AM good candidates for nuclear applica- tions. These materials have recently Recycling of the Pu Global recycling of the actinides and MA of the LWRs Gen. IV in Gen IV fast reactor made spectacular progress and are in Gen IV fast reactors applied in numerous industrial fields, but their adaptation to nuclear needs U, Pu, AM will require work. Fig. 99. The succession of fuel cycles associated with the genera- tions of reactors. One of the major barriers for the devel- Currently, the plutonium from PWRs is recycled in MOX form. opment of nuclear systems of the future is the fuel itself, which In 2020, generation IV PWRs will continue to exist, but the Pu that must combine mechanical and thermal resistance character- they produce will be burned (partially, but more efficiently) by the istics under irradiation, whilst complying with the constraints generation III reactors deployed at this time. The minor actinides pro- linked to neutronics which severely restrict the geometry and duced by this mixed Gen II - Gen III fleet may be partitioned and stored. the materials that can be used. For example, one of the great- In 2040, the first generation IV reactors will be deployed, and will est challenges in the production of a gas-cooled fast reactor burn the Pu which will have been placed in reserve for their start-up, will be to design a dense and refractory fuel. in addition to the minor actinides accumulated earlier. The uranium complement necessary for the operation of these reactors may be Gen IV concepts are not only nuclear reactors: they are supplied by currently stored depleted uranium. Around 2050, these “Gen IV” reactors should be able to operate by designed to operate with a well determined fuel cycle. The recycling the totality of their actinides. reprocessing-recycling of fuel depends a great deal on the nature of the fuel, and on the reactor that can consume it.This is why we do not speak of an isolated “reactor”, but rather “sys- tem” to encompass the reactor and the reprocessing-recycling Sodium-cooled reactors: of its fuel. Consequently, the partitioning, storage and trans- an expertise which remains mutation of nuclear materials involved in these cycles will on the agenda remain important research topics. The objective of maintaining and upgrading the expertise is applicable in particular to sodium-cooled fast reactors, on which France has acquired a major technological advance in Local approach terms of R&D, experimentation of the fracture Physical metallurgy and industrial developments. Materials Thanks to the knowledge Digital R.E.V. acquired during the development mesoscope (representative elementary of the Phénix and Superphénix Discrete Polycristalline volume) Dislocation aggregate reactors and the EFR project, Dynamics CEA masters all of the aspects of Grain the sodium-cooled fast reactor system: Dislocations Structure mechanics • The creation of installations Atomic Mechanical metallurgy clusters since the experimental Rap- sodie reactor (40 MWth) up to Atoms the industrial Phénix (563 MWth) and Superphénix (3,000 Fig. 98. Example of multiscale simulation, applied to materials. MWth) prototypes;

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• Industrial mastery of the main stages of the fuel cycle: One of the developments that can be envisaged for sodium- - manufacturing of uranium and plutonium based fuels, cooled reactors consists of replacing the water of the second- - reprocessing of spent fuel with a 1981demonstration of ary circuit by another fluid less likely to react chemically with Phénix’s ability to use the plutonium that it produced itself sodium. The case of a secondary circuit using supercritical

during a previous cycle; CO2 is currently being explored in detail at CEA. Would we know how to make an FNR-Na with a secondary circuit using

• Experience of the good in service behaviour of a large range supercritical CO2? What would be its advantages and its dis- of structure materials (mainly steels). advantages in relation to a secondary circuit with water, in terms of safety, and efficiency? Such an experience is used within the framework of the research on waste management, because the Phénix reactor is currently used successfully for a series of experiments on Gas-cooled reactors (GCR): actinide transmutation. a preferred development point

Within the framework of the Generation IV International This expertise is also upgraded via international cooperation, Forum, France has expressed a preferential interest for mainly with Japan and the United States, within the Generation advanced very high temperature gas-cooled (VHTR) systems IV Forum, as well as with Russia. One of the main challenges and for fast neutron systems with integral actinide recycling of this jointly carried out research is to provide sodium-cooled (GFR). It will also accompany developments regarding the fast FRs with a good level of economic competitiveness, by mak- neutron and sodium-cooled system (SFR). The very good ing them more compact, and therefore cheaper on investment. positioning of gas reactors in the final evaluation, and therefore CEA is also working on the SMFR, sodium-cooled modular the recognition of the interest for this concept by the fast reactor concept with the Argonne laboratory and the Generation IV Forum, backs up the decision made by CEA in Japanese research institute JNC. This reactor has the partic- 2000 to extend its research on this topic. ularity of modest power and a very long stay time of the fuel in the reactor.

Fig. 100. Reactor hall of the Phénix power plant. Established on the edge of the Rhône, an integral part of the Marcoule nuclear site, Phénix is a sodium fast neutron reactor. Its first divergence* took place in 1973 and the first kilowatt-hours delivered on the grid in July 1974. The last few years have been marked by important renovation works. The experimental programme mainly concerns actinide transmuta- tion, but the experience acquired also benefits the research on nuclear systems of the future.

88 Nuclear systems of the future: an international framework for the development of a new generation of nuclear systems MonoCEA GB 5/04/06 15:31 Page 89

Gas-cooled reactors

Gas-cooled reactors are currently experiencing renewed • The use of a finely divided fuel made up of coated particles interest due to their high operating temperature, which enables which gives it much higher burnup rate capacities, and opens a high efficiency energy conversion cycle, and nuclear energy the possibility of using different nuclear matter. uses other than the generation of electricity. In their thermal spectrum version, construction of industrial- scale reactors are possible in the medium-term. These reac- HTRs and other main systems tors present recognized safety characteristics, as well as a HTR BWR PWR FNR great deal of flexibility in the choice of fuel cycle.This is permit- Unit power 200-1,000 1,100 1,450 1,200 ted via the association of three essential specificities: a partic- type (MWe) ularly confining particle fuel, a coolant, chemically inert helium Efficiency (%) 48 33 33 41 (He), and finally, the exceptional physical properties of graphite Coolant He eau eau Na as a moderator and structure material. Pressure (bar) 50-70 70 155 1-4 In their fast spectrum version, which is still on the drawing Inlet T (° C) 400 278 290 400 board, they offer the additional prospects of energy upgrade of Outlet T (° C) 750-950 287 325 550 natural uranium resources, within the framework of the fuel Moderator graphite water water without cycle reducing final waste and the risk of proliferation. Power density (MW/m3) 2-7 50 100 250 The relevance of this choice as a main avenue of research and Burn-up rate development has been validated by the member countries of (GWd/t) 100-800 30 60 100-200 the Generation IV International Forum, who have retained two of the systems proposed by CEA (the VHTR and the GFR), from the most promising progress concepts for the next few decades 32. The most recent ideas of modular design for HTRs further strengthen their attractiveness from the point of view of safety, Thermal spectrum gas-cooled economy and the possibilities of deployment. The use of gas reactors turbines finally enables a once through energy conversion cycle (Brayton cycle), to be envisaged, improving the efficiency The thermal spectrum High Temperature Reactor (HTR) con- and the compactness of the installation. These are the rea- cept differs notably from the other gas-cooled thermal neutron sons which contribute to the renewed interest in this system. reactors which have been developed in the past: MAGNOX and AGR in Great Britain, and NUGG in France. Particle fuel In relation to these concepts, HTRs differ by: The progress carried out in industry on gas turbines and high • The use of the He coolant enabling access to high tempera- temperature materials has paved the way for HTRs with once tures (≈ 850° C), hence a much greater thermodynamic effi- through cycles, offering new prospects for increasing the ther- ciency; modynamic efficiency of the energy conversion system. In addition, significant advances in the technology of heat exchangers and magnetic bearings currently enable more compact, cleaner and safer gas power plants to be designed.

All of these elements are originally modular HTR concepts, which illustrate the industrial projects, such as the GT-MHR designed by General Atomics, the PBMR developed by Eskom 32. The DEN no. 1 monograph (to be published in 2006) will be entirely in South Africa or the Antares project from Framatome-ANP. dedicated to gas-cooled reactors.

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Current trends for the HTR system are therefore to be consid- ered:

• Modular reactors with unit power in the 100 to 300 MWe range;

• Operating in once through cycle according to the Brayton cycle;

• Enabling the evacuation of the residual power to be assured passively and without using coolant fluid.

The very high temperature reactor (VHTR)

Beyond the medium-term future, mentioned above regarding the HTR, the gas-cooled reactor system has the ability to develop towards even higher temperatures, with at stake a Fig. 101. The use of particle fuel constitutes the main innovation of considerably improved energy conversion efficiency. HTRs.

The kernel of fissile material (UO2, PuO2, UC, etc.) is surrounded by several successive layers (porous or dense pyrocarbon, SiC), used to assure the protection of the fissile kernel, and the containment of fission products. The whole thing is refractory (not metal) and highly resistant, which enables this fuel to be forced to very high tempera- Enhancement of nuclear heat utilization tures and very high burnup rates. Light water ractor This fuel has already been used successfully in the past. It is still Steam temperature: ≈ 300° C capable of performance progress, by a judicious choice of coating Steam cycle 300° C materials (all have not been explored, in particular, the replacement of the SiC layer by ZrC paves the way to very high temperatures, in the order of 1,000° C). CEA is currently equipping itself with a pilot- Thermal Power installation for manufacturing this type of particle fuel (GAÏA installa- efficiency 35 % generation tion, in Cadarache). Loss

30° C High temperature gas-cooled reactor Gas temperature: 1,000° C ≈ 950° C Cogeneration 600° C Hydrogen production Loss Thermal efficiency 70 % 30° C Power Process generation heat

250° C

Fig. 103. Thermal energy is converted a lot better, if it is produced at high temperatures. With a PWR: 2 GWth are discharged to produce 1 GWe; With a VHTR: only 1 GWth would be discharged to produce the same electric power. But this type of reactor also enables the cogen- eration of hydrogen and industrial heat to be carried out, which may bring the global conversion efficiency to approximately 70%.

In addition, high temperatures pave the way for other nuclear Fig. 102. The ANTARES project from Framatome-ANP has a capac- ity of 600 MWth. It uses helium at 850/1,000° C with an intermediate energy industrial applications, in particular the production of heat exchanger, and has a wide range of applications. hydrogen.

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Transmission of electricity VHTR

Heat

CO2 Electricity

Electrolysis Hydrogen

Industrial Thermochemical storage cycle, e.g. lodine/sulphur Distribution

Methane Energy, reforming heat

Hydrogen vehicle H2O

CO2 CO2 sequestration

Fig. 104. Future nuclear systems may produce both electricity and hydrogen.

To produce hydrogen from nuclear (and price) that such a production would entail, the abovemen- energy ? tioned schema does not solve the problem of pollution. It is recognized that the only hydrogen mass production methods The preoccupations linked to climate change, combined with emitting no greenhouse gas are the high temperature electrol- important progress carried out recently on fuel cells, makes ysis and the thermochemical partitioning of water from electric- the use of hydrogen as a clean energy vector more interesting ity and nuclear heat. The production of hydrogen by thermo- than ever. The American government has identified hydrogen chemical method may be carried out in many ways. One of the as an essential element for the future economy, both for indus- ways preferred by numerous research laboratories is the I-S trial needs such as the hydrogenation of heavy oils into light process, thus baptized because it makes the two reagents, fuels, or as transportation fuel. iodine and sulphur intervene (without consuming them). The process involves the decomposition of sulphuric acid, a stage However, hydrogen is not a primary energy and must be pro- at which the efficiency is highly dependent on the tempera- duced, either by electrolysis or thermochemical dissociation ture. A desired efficiency of 50% requires a temperature of of water. The high temperatures which may be reached in 900°C on the process level, that is approximately 1,000° C for nuclear reactors position gas-cooled reactors remarkably well the coolant exiting the core. In practice, only a gas-cooled for hydrogen mass production applications. reactor has the possibility of meeting this requirement. It is from the latter that the main characteristics of the very high Currently, the very large majority of the global production of temperature reactor follow. hydrogen comes from reforming natural gas:

Q+ CH4 + 2 H2O → CO2 + 4 H2, which produces a lot of CO2, both in the chemical reaction and in the calorific contribution to the endothermic reaction.

The United States projects a quadrupling of its hydrogen con- sumption between now and 2017 to 10 million tonnes per year. Clearly, apart from the strong increase in gas consumption

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O2 H2

H SO HI T~850° C2 4 T ~ 450° C Decomposition Decomposition

Materials It involves finding and developing mate-

H2 SO4 H2O HI rials able to resist both high neutron flu- Heat Distillation Distillation ence and high temperatures. The research concerns refractory alloys, ceramics, and cermet and cercer com- posites. Bunsen reaction T~120° C Helium technology,

16H2O+9I2+SO2 → (H2SO4+4H2O)+(2HI+10H2O+8I2) components, equipment First generation gas reactors use CO Fig. 105. Diagram of the thermochemical cycle of hydrogen produc- 2 tion via the iodine-sulphur process. as a coolant fluid, and helium has been little used in nuclear power. Current research concerns tribology in helium, gas purification tech- niques, heat exchangers, pumps, turbines, as well as thermo- dynamic schemas enabling the best energy efficiency to be What research for the VHTR? obtained from a helium-cooled reactor.

The development of the VHTR will not be easy. Admittedly, the German AVR reactor has already reached core outlet temper- atures greater than 950° C. But above this temperature, tech- nological ruptures become necessary. The main avenues of Helium technological loop (Helite) research are listed hereafter:

Calculation tools and methods: • Materials • Helium technology HTR or VHTR cores present both a random geometry and het- • Component tests erogeneities on very diverse size scales. These two charac- • Equipment tests teristics require an adaptation of the neutron calculation tools: one of the channels pursued is the development of Monte Test section 1,000° C Carlo type neutron calculation methods. Heating Cooler 1,000° C 1,000° C On the other hand, in gas reactors with once through cycle, the thermohydraulics of the core is strongly coupled with that Test section 500° C

of the turbomachine: any change in the operation of one has 600° C repercussions on the operation of the other. These couplings 500° C Recuperator must be taken into account and modelled in order to assure 200° C control of the thermohydraulic behaviour of the system. Cooler Compressor

Fuel technology 100° C

The fuel is one of the deadlocks of gas reactors. For the VHTR, HPC above all it involves finding a refractory fuel. Even if they (1 MW, Q ≈ 0,4 kg / s, T< 950° C, P > 7MPa) remain yet to be qualified, solutions already exist with UCO for the fuel and ZrC for the cladding material. Fig. 106. Example of research carried out for the development of the VHTR: CEA develops the test benches and loops for testing the main components and equipment associated with helium technology.

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The gas-cooled fast reactor (GFR) of fissile material with a good resistance to high temperatures and to irradiation by fast neutrons. Several fuel concepts are In a long-term perspective aiming to meet the sustainability currently being studied at CEA: a dispersed fuel, in which the requirement, the Gen IV forum has retained the gas-cooled fissile compound is presented in the form of grains or millimet- fast reactor as a particularly interesting system.The latter must ric sticks dispersed within a “containing” matrix assuring the succeed in conciliating both the advantages of high tempera- function of 1st barrier just like the PyC/SiC coatings of the HTR ture gas reactors with those, known, of fast neutron reactors particle; a fuel rod type concept with leaktight ceramic cladding (optimal use of resources, reduction of waste production, is also being evaluated. transmutation of actinides). In addition, the specifications of the integrated cycle would reduce the risks of proliferation. Towards a European demonstrator The reactors proposed will be based on the helium technol- of 4th generation gas-cooled reactor ogy developed for the HTR and VHTR projects. Their speci- ficities are the fuel and its cycle, and the safety of the reactor. With the High Temperature Engineering Test Reactor (HTTR, Their fuel cycle is at odds with the existing one because it is 30 MWth) which has been exploited since 1998 by JAERI, proposed to not partition U and Pu, and also to not partition Japan currently has the most efficient test means on very high major actinides (U, Pu) from minor actinides (Np, Am, Cm). temperature nuclear technologies, and on the nuclear produc- The core’s design (without blanket) will target the iso-genera- tion of hydrogen.The United States is preparing a first demon- tion of plutonium and a non-proliferating cycle maintained only stration of the production of hydrogen by thermochemical by the provision of depleted uranium. decomposition or electrochemical decomposition of water in the Next Generation Nuclear Plant (NGNP, 600 MWth) project The first studies have enabled the image of fuel for a gas fast on the national Laboratory site at Idaho. South Korea and reactor to be outlined. The latter must combine a high density China are mentioning similar projects around 2020.

> Fast neutrons GFR > Integral recycling of the actinides

R&D • Fuel for fast neutron core VHTR • Cycle processes • Safety systems R&D • VHT resistant materials HTR •Intermediate R&D heat exchanger •Particle fuel • ZrC coated fuel • Materials •H2 production • He circuit technology • Calculation systems • Fuel cycle

Fig. 107. High temperature gas reactors are already relatively mature, and may be deployed in “3+” Generation. These reactors may then develop towards even higher temperatures (VHTR), and/or towards a fast spectrum (GFR).

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In this context, and given the industrial issues associated with The REDT enables the upgrade of the wide experience the very high temperature and nuclear production of hydrogen acquired in Europe on the high temperature reactor systems, technologies, CEA is studying a Study and Technological and strengthens the position of European industrialists in the Development Reactor (REDT) at the Cadarache Centre, aim- international competition to market reactors from this system ing to demonstrate the technological principles of the GFR. around 2020.

The main development stages of the REDT may be: The REDT could be considered as the main element of a European test platform for key technologies for the VHTR and •A first operating phase at 850-950°C with a thermal neutron the GFR, as well as for the various high temperature heat core aiming to demonstrate the European mastery of applications. The purpose of this platform would be to supply updated HTR technologies and of high temperature heat the necessary experimental conditions for the studies regard- conversion processes for various applications: electricity, pro- ing the high thermodynamic efficiency cycles for the generation duction of hydrogen by thermochemical cycle or high tem- of electricity and the development of cogeneration processes. perature electrolysis. Other applications may eventually com- The platform would also enable the qualification of compo- plete the range of demonstrations possible: gasification of nents for the conversion of energy (turbines, heat exchangers), the biomass or desalination of seawater; and the study of processes for the production of hydrogen, gasification of the biomass and desalination of seawater. •A second operating phase, around 2020, with a fast neutron core aiming to demonstrate the operating principles and spe- The pre-project studies for this platform would come into the cific technologies of the GFR (the fuel in particular), thus framework of the 7th European research and development repeating the initial objectives of the REDT. framework programme as of 2007.

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Other avenues for the distant future: thorium cycle, hybrid systems, fusion

The thorium cycle •A serious doubt remains on the possibility of using highly enriched U 233; if an enrichment greater than 20% were pro- Thorium (Th 232) is a fertile material which is abundant in hibited for non-proliferation reasons, a significant quantity of nature. By absorbing a neutron and then by radioactive decay, actinides would be found in the uranium-thorium cycle; it produces Pa 233 then U 233, a fissile isotope. The latter is interesting, because its fission generates slightly more neu- • The long-term radiotoxicity (1,000 years and beyond) of trons than that of U 235 or Pu 239 in a thermal spectrum. In waste is dominated by residual U 233 and by several the 50s, these different reasons have led to interest in the radionuclides: Pa 231, U 232, U 234, Np 237. In most of the U 233-thorium cycle; fuels were manufactured and used in var- cases studied, beyond 104 to 105 years, uranium-thorium ious reactors, of which the American Shippingport experimen- cycles lead to a radiotoxic inventory which may be much tal PWR, the Fort St. Vrain HTR and the German THTR. higher than that of uranium-plutonium cycles. At that time, however, the radiotoxicity will have greatly decayed; Unfortunately, the emission of high energy (2.6 MeV) γ radia- tion by Tl 208 formed in recycled U 233-thorium fuels poses •A fast U 233-thorium reactor would be a good incinerator of serious radiation protection problems in fuel manufacturing minor actinides, but the benefits from the point of view of installations; this disadvantage is one of the reasons why the radiotoxic inventory of buried waste would not be significant 33 uranium-plutonium system is preferred (the main reason beyond 105 years; being that it would be necessary in any case to start a thorium system with the only fissile material existing in nature, U 235; • Conversely, the heat release from actinides produced in tho- the thorium system, as opposed to the uranium system, may rium-based cycles is much lower than in uranium-based therefore not be developed alone). cycles; the result of this is that the “thermal” dimensioning of the disposal is only defined by the residual power of the fis- During the last few years, the thorium system has been the sion products. By contrast, the uranium-plutonium fuel cycle subject of a new study, both because this system produces is handicapped by actinides with high thermal release much fewer transuranium elements* and because robotics (curium and, to a lesser extent, americium); and remote handling have made considerable progress, per- haps limiting the disadvantages linked with γ radiation. The • Once the thorium is extracted from the mine, the daughter results of these studies are summarized below: radionuclides which remain in the mine tailings decay very quickly, at the rate of the period of 5.7 years from their top • The best use of thorium is in molten salt thermal neutron series, Ra 228; it follows that, as opposed to uranium mine reactors, which allow a reduced inventory in fissile material tailings, the thorium mine tailings do not pose a real long- and which are just as favourable on the resources level as term problem. on the waste level (reduction of the production of U 232 source of Tl 208, of the reprocessing losses, of the conse- The thorium based systems are therefore similar to uranium quences of accidental discharges, of the final waste); how- systems, as regards fission products and the quantities of ever it does not enable doing without U 235 or Pu in order to actinides in the very long-term; they are important for the “ther- start the cycle and thus does not completely eliminate minor mal” dimensioning of disposal, but present certain disadvan- actinides; tages for the remanufacturing of solid fuels after reprocessing (but the problem is the same for GEN IV cycles with integral •A Th-Pu cycle in a fast neutron reactor (critical or sub-critical) recycling of the actinides, because it will be necessary to enables twice as much plutonium to be consumed as a U- remanufacture the fuel also by remote handling). Their main Pu cycle (thanks to the absence of U 238), and large quan- interest resides in the increasing of resources; interest with a tities of U 233 to be produced; once started, the U 233-tho- very distant timescale if fast spectrum uranium systems rium cycle may be self-sustained; develop normally, with closer timescales, in the opposite case. Under certain conditions, they would enable a reduction of the quantities of minor actinides produced. The thermal load of 33. This disadvantage only exists in the manufacturing of solid fuel; it is “drowned” in the highly radioactive background of a reprocessing instal- glass could be diminished, with a subsequent reduction of the lation integrated near to a molten salt reactor. needs in interim storage and disposal area.

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In such a scenario, where the failure of fast spectrum systems Sub-critical reactor would be postulated, thorium may only find its place in a ther- Fission mal spectrum system capable of being self-sustained: the most attractive is the molten salt fuel system.The nuclear sys- Accelerator tem would therefore be as follows: Spallation target

•A fleet of water reactors producing plutonium; Protons 1 GeV 10-100 mA •A fleet of thermal neutron molten salt reactors, started with Neutrons plutonium produced in the former. Transmutation

The thermal neutron molten salt reactors therefore seem to be an alternative to fast spectrum reactors from the point of Fig. 108. Principle of the ADS (Accelerator Driven System), or view of a sustainable development of nuclear power. “hybrid reactors”. Consequently, this would require implementing two reprocess- ing processes, one by the aqueous method for water reactors, and the other one by the pyrochemical method for molten salt The principle of the ADS is simple: accelerated protons hit a reactors. target located in the middle of the reactor’s core and produce the additional neutrons needed to complement the neutron The thorium based systems therefore present some clear balance of a sub-critical reactor core. The production of neu- advantages and disadvantages. The result of this is that it is trons is carried out by the spallation process. The maintaining unlikely that they develop unless enormous amounts of fertile of neutron balance in the reactor is assured by controlling the materials are required in the future. beam’s intensity.

Accelerator-driven systems Although the principle is conceptually simple, if they are con- for the transmutation of waste structed, the ADS will be technologically and operationally complex installations. The generation of electricity in a nuclear reactor is accompa- nied by the creation of heavy isotopes (“transuranium ele- In an industrial ADS system comprizing a ~1 GWth reactor, ments”, heavier than uranium), some of which are radioactive the associated proton accelerator must be of a very high over long periods of time. Among them, plutonium has an power (beam of protons with a power able to reach a few tens important energy potential, and France has chosen to extract of megawatts: energy of ~1 GeV, optimal for the production of it from spent fuels in order to recycle it in the fleet’s reactors neutrons, intensity of one to a few tens of mA, according to the (MOX fuel). Other transuranium elements, mainly neptunium chosen sub-criticality). Moreover, in order to avoid a too high (Np), americium (Am), and curium (Cm) isotopes constitute a number of power excursions, which would shorten the life of proportion of the high level and long lived waste (HLLL). the reactor, the authorized number of undesired acceleration shutdowns is very low (a few breakdowns per year). The reli- As seen above, the isotopes of these minor actinides Np, Am ability requirement, unusual in the normal use of accelerators and Cm are transmutable in a fast reactor. However, it is diffi- by physicists, is a major challenge for constructors. Only lin- cult to introduce high proportions of minor actinides in the fuel ear accelerators should be able to supply proton beams with of critical reactors, for neutronic reasons linked to the low pro- such performances, as the intensity of cyclotrons seems lim- portion of delayed neutrons and to the low Doppler effect asso- ited to a few mA. ciated with these isotopes. For the transmutation of minor actinides, another approach consists of using, reactors oper- In order to produce a maximum number of neutrons, the spal- ating in subcritical mode driven by accelerators: the ADS lation target will consist of a heavy element (rich in neutrons). (“Accelerator Driven Systems”), also known as “hybrid reac- The proton beam will be completely stopped in this target, tors”. In these systems, the neutron balance of the reactor which will therefore dissipate the totality of the beam power. requires an external contribution of neutrons: the sub-critical- The designing of these targets, probably liquid (lead or lead- ity margin thus introduced (a few percent) would enable the bismuth), is an important technological challenge: the strength use of fuels loaded with a high actinide content under satis- of the entrance window crossed by the proton beam and sub- factory conditions of safety.Therefore fleets of “double strata” jected to high irradiation stresses, is essential, because it con- reactors can be envisaged: for the French fleet, an assembly stitutes a barrier between the accelerator’s vacuum and the of a few ADSs would assure the transmutation of minor reactor; the evacuation of the heat produced by the beam and actinides produced in the main fleet of electricity generating the corrosion of the target’s shell by liquid metals are also reactors operating with U-Pu fuel. important technological issues.

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Oxford, in the United Kingdom). n Although of lesser power and reliability

p (1 GeV) than those envisaged in the industrial ∆ n π π ADS, these installations have supplied interesting feedback. Other installations

n are being prepared (the SNS neutron p source at Oak Ridge (United States), Intra-nuclear cascade Excited nucleus that of J-PARC at KEK, near Tokyo, Evaporation Japan, where experiments on transmu- α d tation are planned).

α ADS feasibility studies are now well advanced. Work has been carried out on the national level, at CEA and in a γ CEA-CNRS collaboration, and on the n European level, under the aegis of the γ Spallation residue γ Fission products Technical Working Group (TWG) and α, β, γ decay within the framework of the 5th and now, 6th RDFP European projects. Fig. 109. Spallation mechanisms. Industrialists have participed exten- sively in this work.

The reactor of an ADS will also be highly innovative.The trans- In the CEA-CNRS collaboration, zero power experiments have fer of the beam onto a reactor core target and the dissipation been carried out at Cadarache on the critical Masurca mock- of the power produced require a very different design to that up (CEA-Cadarache) and a high-intensity proton injector is in of a conventional reactor, in particular as regards the safety the process of being constructed at CEA-Saclay. barriers (it seems difficult to encompass the entire accelerator in a containment). Two significant steps could be taken within the framework of the 6th European Research Program: the completion of a The designing of fuels incorporating large proportions of demonstration experiment consisting of coupling a proton actinides must call into play highly innovative concepts into accelerator to a reactor for the first time and the production by play, both out of the reactor (strong γ activity and neutrons) a group of European laboratories of a fairly detailed pre-proj- and in the reactor (behaviour fairly unknown). Long stay times ect of a significant power demonstrator. in the reactor are necessary in order to destroy a significant proportion of minor actinides and, at the same time, actinides To date, no complete economic study of the ADS concept with a higher atomic number are produced. The technological exists, in particular because the fundamental choices regard- problems linked to the behaviour in reactors of such fuels, to ing its elements (accelerator, spallation target, reactor type) their manufacturing, to the permanent disposal of spent fuels are yet to be made. However, it is certain that the cost of an or to their reprocessing and possible reconditioning for re-irra- ADS would be considerably higher than that of a critical reac- diation, are highly complex and will require a great deal of tor because, to the almost identical reactor cost, it is neces- R&D. sary to add those of the accelerator and the target. Finally, the ADS safety studies will be important because they must validate an innovative design but also the new mode, of The future of ADS is conditioned, firstly, by a decision regard- driving reactors with accelerators. ing the continuation of the studies and establishment of the partitioning-transmutation on an international level. Secondly, No ADS has been constructed yet since the first studies in the if the HLLL waste management mode by partitioning/transmu- ’50s concerning the use of accelerators in order to obtain an tation is adopted, the two transmutation techniques, in critical exterior supply of neutrons in a fission reactor. reactor or in sub-critical reactor (ADS) will have to be dealt with, regarding the technological and economical aspects. However, linear proton accelerators and spallation neutron production targets have been constructed for other purposes 34 In any case, it will not be possible to deploy ADS on an indus- than that of the transmutation of nuclear waste (mainly trial scale before a few decades, as they still require a very LANCSE at Los Alamos, in the United States, and ISIS, near important R&D and demonstration effort.

34. The ADS could also be a precious tool as a neutron source for tech- nological radiation tests of various materials and, in particular, fuels.

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Thermonuclear fusion

Potentially, fusion energy is one of the most interesting primary energy sources, because:

• There are no reserve problems (it consumes deuterium and lithium used to produce tritium; these elements are abundant in nature);

• The fusion reaction does not produce any high level and long-lived radioactive waste;

• Fusion does not induce greenhouse gas effects (no produc-

tion of CO2);

•A fusion reactor is intrinsically safe (immediate disappear- ance of plasma in the event of malfunction; no “nuclear mate- rial”).

But the industrial application of * is still faced with major technological challenges which will require inten- Fig. 110. Two possible magnetic configurations to confine the sive R&D prior to arriving at the electricity generation installa- plasma: cylindrical and toroidal. In both cases, the D and T ions tion construction stage. propagate along the field lines. The toroidal configuration is the basis of most installations. Several fusion reactions of light nuclei may be used in princi- ple to produce energy. In practice, the only reaction to have a sufficiently low energy to be considered is the nuclear fusion reaction between the nuclei of two hydrogen isotopes, deu- terium (D) and tritium (T):

D + T → 4He (the “α”; 3.5 MeV) + n (14.1 MeV)

This reaction can only be produced if the deuterium and tri- tium isotopes are completely ionised, otherwise atom-atom or atom-ion collisions, much more probable than nuclear fusion, prevent the nuclei from fusing. In the case of complete ionisa- tion and as of a few tens of keV of kinetic energy of D and T, this reaction is produced with a significant probability by “tun- nel effect”. It can therefore be used to produce energy, if it has been possible to maintain the D and T nuclei in interaction, that is, if the plasma formed by the deuterium, tritium and elec- trons from the ionisation has been kept confined and suffi- ciently “hot”.

Two possible methods are offered to assure the confinement:

• Magnetic confinement, by which the plasma’s particles Fig. 111. Combinations of coils in a to produce the mag- netic field confinement of plasma. (charged) are maintained confined in a finite space by a suit- able magnetic field configuration; In magnetic confinement systems, the most developed being • Inertial confinement, which in fact involves a compression- the “tokamak” type, the heating of plasma (that is maintaining heating of a D-T mix by pulses from laser beams or conver- the kinetic energy of the D and T nuclei at a value high enough gent pulsed particle beams; fusion is produced and lasts as for fusion to occur) takes place in many ways: long as the compression is sufficient, the process is repro- duced on each pulse. transfer of the energy from α particles from the fusion reaction to the D+T plasma; ohmic heating induced by the plasma’s

98 Other avenues for the distant future: thorium cycle, hybrid systems, fusion MonoCEA GB 5/04/06 15:31 Page 99

electric current; heating by high frequency electromagnetic waves or heating by neutral particle injection. s) -3

m Ignition The state-of-the-art on fusion by magnetic con- 20 (10 E

finement τ So that fusion can be used as an energy source, it is neces- ITER sary that the energy produced by the fusion be greater than

that injected to heat and maintain the plasma (Q = Pfus/Pext >1). This system, called “breakeven” is expressed by a constraint of the type: Lawson parameter;Lawson n.

n. τE > f (T)

where n is the density of plasma, τE the confinement time and T its temperature.

Considerable progress has been made in the last few decades on the fulfillment of this criterion. By way of example, the Tore- Supra installation in Cadarache now produces plasmas con- fined over several minutes, and the European JET installation, in Culham, England, is close to meeting this Q>1 constraint. Central ion temperature (keV)

Many technological problems, however, are yet to be solved Fig. 112. Performances reached by existing or project installations, in prior to envisaging the construction of an industrial installation, the “Lawson vs. temperature parameter” diagram. It will be noted that in which the α particles produced by the reaction would be suf- ITER* is located at the limit of the ignition zone (a α particles from ficient to heat the plasma. These technological problems are the fusion will assure 2/3 of the plasma’s heating). of three orders:

• The toughness of the materials in contact with the plasma:

• The minimisation of the activation of the blanket materials: In an industrial system, the first lining must evacuate a very high power density (it may locally exceed 20 MW/m2), support The neutrons interacting with the walls cause the appearance the very high neutron fluxes which will cross it in order to go of radioactive elements, via nuclear reactions. The choice of into the tritigenous blankets and enable the evacuation of a the composition of the blanket materials must be such that it large quantity of gaseous helium originating from the fusion minimises, in level and in time, the production of the reactivity reaction.The development, in the 80s, of the “divertor”, a spe- induced. cial magnetic configuration making it possible to better man- age the fluxes to be evacuated from the plasma, has con- Inertial confinement-heating only seems possible with pho- tributed a great deal to the progress accomplished during the ton beams (lasers) or heavy ions, but, even in this case, the last two decades. scientific and technical problems to be solved do not enable an industrial-scale implementation in a foreseeable future. • The production of tritium in the lithium tritigenous blankets:

In such systems, the neutrons, originating from the fusion The ITER project and nuclear fusion reaction continuously produce the tritium consumed in the outlook plasma, by interaction with the lithium blankets (“tritigenous blankets”), thus avoiding the storage and handling of this The purpose of the global ITER nuclear fusion experimental radioactive element. The overall quantity of tritium present in reactor project is to scientifically and technically demonstrate an industrial type installation is therefore only a few grams. that it is possible to use fusion to produce energy. The part- However, tritium diffuses easily and the control of its diffusion ners are the European Union, Russia, Japan, the United is an important safety aspect. States, China and South Korea.

The installation (Fig. 113) will be of the tokamak type.With size and performances similar to the industrial reactors envisaged (Q = 10, heating of the plasma to 66% by α particles), it will

Nuclear energy of the future: 99 what research for which objectives? MonoCEA GB 5/04/06 15:31 Page 100

enable the research which is still necessary on materials and the operation of a fusion reactor to be carried out in a realistic configuration.

The Cadarache site was retained to host this €4.5 bn installa- tion. The construction time is 12 years and ITER should be operated during approximately twenty years.

If the results gathered and the studies of materials confirm the scientific and technological possibility of using nuclear fusion for the production of energy, an industrial production reactor prototype, studied in parallel to the ITER operation, could then be constructed. Even then, the road leading to the industrial exploitation of nuclear fusion will be long, because the eco- nomic competitiveness of this mode of energy production still remains to be demonstrated.

Central solenoid Blanket element

Toroidal field coils Vacuum chamber

Poloidal field Cryostat coils Heating of the plasma

Divertor

Support columns Cryopump

Fig. 113. Diagram of the ITER installation, global scientific and technical validation project for the use of fusion for the production of energy.

100 Other avenues for the distant future: thorium cycle, hybrid systems, fusion MonoCEA GB 5/04/06 15:31 Page 101

Conclusion

The world of nuclear power is rapidly evolving and the In the long term, radical progress can be expected, even rup- prospects of increasing the global fleet are being confirmed. tures associated with the development and the emergence of Nuclear energy is currently recognized by most organisations new types of nuclear reactors, that can be used for electricity issuing energy projections for future decades (International production as well as for other applications, hence the impor- Energy Agency, World Energy Council) as an available, reli- tance of the research on innovative reactors. These reac- able and environmentally friendly energy source because it tors cannot be studied in isolation.They are indissociable from does not emit polluting or greenhouse gases. Nuclear power their fuel cycle. Moreover, nuclear power will only be sustain- has its place fully in the global energy mix. able if nuclear materials are recycled: given its importance, research on reprocessing-recycling must be continued. France which has succeeded in one of the most ambitious CEA is commited to research programmes on future nuclear nuclear development programmes, can now promote the systems, with international collaborations in which it plays a choice of its energy policy to the exterior by showing its advan- leading role: firstly the Generation IV International Forum, tages. which has retained six concepts for the long-term R&D, four of which are “closed cycle”. Other collaborations include However large obstacles must be mentioned: nuclear power European programmes and projects carried out bilaterally with is not recognized by the Kyoto agreements as eligible for the United States, Japan, Russia and China. financing mechanisms aiming to limit greenhouse gas emis- sions. Although the future development of nuclear power The waste issue warrants close attention because it repre- seems assured in Asia, in spite of that, it will largely depend on sents a particularly sensitive point in the eyes of the public democratic debate in the West. Removing these obstacles opinion and political power. Research in progress has already requires a better acceptance of civilian nuclear power in the produced technical solutions to partitioning, conditioning and eyes of the public and its political representatives.This implies storing waste under good safety conditions. In view of a polit- that industrialists and scientists must build confidence, in a ical decision on the implementation of these solutions, French long and continuous process, where all mistakes, particularly law prescribes carrying out research on all possible meth- in the field of safety, must be avoided. ods of waste management.

All in all, nuclear energy is a young energy: it is only 50 years More generally, development must not only be an escape into old! It has come a long way since its birth, but the prospects the future, it must also properly finish up old operations: this of progress are still very great. is the aim of research on dismantling, decontamination and clean-up. In the short-term, continuous development progress can be expected, and existing systems will benefit from it: this is the For all of this research, time and means are needed. aim of the research supporting current industrial nuclear power. This research concerns the reactor safety and the The CEA is backed by a solid nuclear industry, in particular improvement of competitiveness, particularly by extending the AREVA and EDF, which have legitimate ambitions on the lifetime of power plants, but also by increasing the fuel burnup global energy market. This is an important advantage which rate. A lot of incremental research is being carried out in part- should enable CEA to highlight the results from its research. nership with industry, in a not very spectacular way, because in nuclear R&D, time constants are very long, and significant The world of research is evolving. Science in the 19th century scientific results are not obtained every week. This R&D car- and in the first half of the 20th century was dominated by ried out in partnership with industrialists is an integral part of geniuses; then came the time of laboratories, but that time has the quality of the French nuclear offer. In an internationalized also past. Now is the time for international networks and struc- market such as that of nuclear power today, it constitutes one tures. CEA must therefore adjust to these new conditions, by of its main and recognized advantages. integrating its R&D effort into international cooperation, on the European level within the framework of research programme, and on the global level in the existing networks, as for exam- ple the Generation IV Forum. An international consensus on

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the strategic and technical choices for the nuclear power of the future would present the interest of considerably increasing the credibility of the solutions proposed in the eyes of the pub- lic opinion and decision makers.

In this stimulating overview, the CEA and its Nuclear Energy Division is monitoring developments in the world of nuclear power. Every year it receives in its laboratories approximately fifty foreign employees, mainly from China, Russia and Japan and also transfers engineers to these countries. It participates in the IAEA work on safety and non-proliferation, as well as in that of OECD/NEA in technical, economical and social fields.

On the international scale, the Nuclear Energy Division is devoted to the ambition of contributing to the peaceful and sus- tainable development of this energy.

102 Conclusion MonoCEA GB 5/04/06 15:31 Page 103

Glossary - index

Activity: number of disintegrations per unit of time within a Chain reaction: a string of nuclear fissions* during which radionuclide or a mixture of radionuclides. It is expressed in bec- released neutrons* produce new fissions, in turn generating new querels (Bq), which corresponds to one decay per second. 19, 59, neutrons producing new fissions and so on. 63, 97. Cladding: envelope surrounding the fuel material, designed to ADS: “Accelerator Driven System”, hybrid reactor coupling a sub- maintain its position in the reactor core, and to ensure its isolation. critical reactor core with a high energy proton accelerator.The lat- 15, 16, 18, 19, 29, 47, 49, 51, 57, 64. ter supplies the additional neutrons necessary to maintain the Climate change: see chapter “Energy in the world”. 33. chain reaction thanks to spallation reactions. 62, 63, 77, 78, 96, 97, 98. Conditioning (waste): operation by which nuclear waste is put in a stable and durable form. 8, 16, 17, 21, 23, 60, 63-65, 97. ALARA: “As Low As Reasonably Achievable”. General manage- ment principle relating to radiation protection that consists in min- Control cluster: see *. imising radioactive emissions or doses as much as is reasonably possible, given economic and social constraints. 61, 62. Control rod: rod or collection of connected mobile shafts contain- ing matter that absorbs neutrons and that, according to its position ANDRA: Agence nationale pour la gestion des déchets radioac- in the nuclear reactor core, influences its reactivity. tifs.The French national agency for radioactive waste management. Coolant: fluid (gas or liquid) used for extracting the heat produced ATALANTE: see chapters “The near future: research supporting by fissions*. In a pressurized water reactor*, water plays the the existing nuclear power” and “Research regarding waste man- role of both a coolant and a moderator*. 9, 12, 49, 75, 77, 78, 82- agement”. 49, 50. 93. Atom: the basic unit of matter. It is made up of a nucleus (itself Contamination: undesirable presence of a radioactive substance made up of neutrons and protons) around which electrons gravi- in contact with a surface or inside an environment. 23, 24, 27, 29, tate. 12, 16, 43, 51, 87, 98. 31. Atomic number: a number assigned to each element according Core: region of a nuclear reactor in which a to Mendeleev’s classification. It is equal to the number of protons can occur. 9, 12, 13, 18, 23, 29, 30, 47-49, 53, 55, 56-58, 62, 75, 77, in the nucleus of an atom of the element in question. 83-85, 91-94, 96. Barn: unit used to measure a nuclear cross section. Core melting: nuclear accident during which the nuclear fuel is (1 barn = 10-24 cm2). 75. heated to such extent that it melts.The resulting corrosive magma (the corium*) gathers at the bottom of the reactor vessel, where Barriers: in a nuclear reactor, all physical elements that isolate it can cause further damage to the reactor. 30, 55. fuel radionuclides* from the environment. In a pressurized water reactor*, it relates successively to the cladding of the fuel element, Corium: mixture of molten materials resulting from the acciden- the shell of the primary circuit (including the vessel) and the reac- tal fusion of a nuclear reactor core. 55, 57, 58. tor containment. 20, 29, 30, 32, 97. Critical: an assembly of material containing fissile matter can be Binding energy: the energy required to extract a particle from a qualified as critical when the number of neutrons* emitted by fis- physical system, for instance a nucleus. sion* is equal to the number of neutrons disappearing by absorp- tion and leakage. In this case, the number of fissions observed (BWR): reactors in which water is boiled during successive intervals of time remains constant. Criticality* directly in the core. 11, 18, 53, 76, 78, 79, 89. is the expression of an exact equilibrium between the production Breeder reactor/breeder: a reactor that produces more fissile* of neutrons by fission and disappearances by absorption or leak- fuel than it consumes. New fissile nuclei are created by fission age. 29, 62, 96-98. neutron* capture by fertile* nuclei (non-fissile under the action of Cross section: measure of the probability of interaction of a par- thermal neutrons*) after several radioactive decays*. 12, 75, 77. ticle with a target-nucleus, expressed in barns (1 barn = 10-24 cm2). Burn-up: see Specific burn-up*. The cross section measures the probability that a given reaction will occur between incident particles (neutrons for example) and a Burn-up rate: in the literal sense, it corresponds to the percent- target (uranium nuclei for example). In nuclear reactors, we mainly age of heavy atoms (uranium and plutonium) that underwent fis- distinguish reactions caused by neutrons: fission, capture, and sion* for a given duration. It is commonly used to evaluate the elastic scattering. 75. quantity of thermal energy per unit of fissile* matter mass obtained in a reactor between fuel loading and unloading and is Daughter product: nuclide formed from the spontaneous decay expressed in megawatt days per tonne (MW·d/t). of a radioactive nuclide. Calculation software: the grouping of the simplified representa- Decommissioning: group of administrative and regulatory oper- tion (modelling) of a system or a process in software, in the form ations to either file a nuclear installation in a lower category or to of coded mathematical expressions in order to simulate it. delete the initial filing. 23, 25.

Nuclear energy of the future: 103 what research for which objectives? MonoCEA GB 5/04/06 15:31 Page 104

Defence in-depth: see chapter “Nuclear safety and security”.27. Fissile (nucleus): nucleus which can undergo fission* by neu- tron* absorption. However, the fissile nucleus does not undergo Desalination (of sea water). 9, 79, 82, 94. fission, the composite nucleus formed after neutron capture does. Disintegration: transformation of an unstable nucleus into a sta- 13, 15, 16, 17, 18, 30, 62, 67, 75-77, 83, 85, 95. ble or unstable nucleus during which the number and the nature Fission: the splitting of a heavy nucleus in two, accompanied by of the nucleons are modified. neutron emission, radiation, and high energy release. 12, 13, 16, Dismantling: group of technical operations that lead a nuclear 19, 75, 77. installation to a chosen level of decommissioning*. 23-26, 30, 39, Fission products: nuclides* generated either directly by nuclear 101. fission*, or indirectly by the decay of fission fragments. 12, 15, 16, Disposal facility (of nuclear waste): underground installation in 19, 61, 64, 70, 71. which nuclear waste is disposed of, without prospect of retrieval. Fluence: dose unit used to quantify material irradiation.The num- Retrieval would be possible in the case of a reversible storage*. ber of particles (neutrons) arriving per unit of surface area during Divergence: start-up of the chain reaction* process in a reactor. irradiation. 52, 56, 57, 92. 88. Fuel: matter containing the fissile nuclei which maintain the chain Dose (absorbed): quantity of energy absorbed locally per unit of reaction* in the core of a nuclear reactor. 8, 15-18, 47-52, 56, 57, 67- material mass (inert or live). It is expressed in grays* (Gy): 1 gray 71. corresponds to 1 joule of energy absorbed per kilogram of material. Fuel cycle: all steps followed by the fuel from extraction of the ore Dose (effective): the sum of the weighted equivalent doses deliv- to waste disposal to the possible recycling of material in the reac- ered to the organs of a living body by internal or external irradia- tor. 9, 17, 19, 43, 45, 47, 53, 62, 65, 67, 73, 74, 77, 84, 87-89, 93, 101. tion.The unit of effective dose is the Sievert (Sv). For example, the Fuel rods: a small diameter tube closed at both ends, making up average annual dose received yearly from natural origins (soil, the core of a nuclear reactor, containing fissile, fertile or absorbent cosmic rays…) is of the order of 2 milliSievert (mSv). matter. When it contains fissile matter, the fuel rod is a fuel ele- Dose (equivalent): in living organisms, the effects of a given ment*. 15, 17, 19, 48, 51, 56, 57, 93. absorbed dose* depend on the nature of the radiation (x, , , ). α β γ Generation (of nuclear reactors). 7, 11, 53, 68, 69, 79. In order to take these differences into account, one uses a multi- plicative factor to calculate an equivalent dose. GIF or Gen IV: international collaboration for the development of nuclear systems of the 4th generation. 78, 93, 96. Dose (radioactive): see chapter “Nuclear safety and security”.27. Glove box: containment in which material can be manipulated Economy of nuclear power. 39. while isolated from the operator. Handling takes place using gloves Electronvolt (eV): unit of energy used in nuclear physics, 1 eV = fixed in a leaktight way to openings provided in the wall of the con- 1.6·10-19 joule. tainment. Generally, it is set to partial vacuum to contain radioac- tive substances. Enrichment: a process which, in the case of uranium, enables isotope 235 concentration to be increased using various meth- Gray: unit of absorbed radioactive dose, corresponding to the ods (gaseous diffusion, ultracentrifugation, selective excitation by absorption of 1 joule of energy per kilogram of matter. laser) in relation to isotope 238 predominant in natural uranium. 17, GWe: electric power provided by a power plant. 18, 30, 31, 41, 53, 76, 79, 95. GWth: thermal power provided by the same power plant. Epithermal neutrons: neutrons located in the 10 eV* to 20 keV energy range, approximately, and with a speed greater than that Heavy nuclei: denomination given to isotopes* of elements with of thermal neutrons*. proton numbers (atomic number) greater than or equal to 80. All of the actinides and their daughter products are in this group. 17, EPR: European Pressurized Reactor. See chapter “Preparing the 67, 68, 75. replacement of current reactors with more efficient and safer 3rd generation reactors”. 53. Heavy water: deuterium oxide (D2O). 11, 12, 53, 54, 75, 76, 78, 79. Fast neutrons: neutrons released during fission, moving at very Hot Cell: highly shielded cell of a hot laboratory in which high level high speeds (20,000 km/s).Their energy is in the order of 2 million substances are handled using remote manipulator arms. electronvolts*. 6, 9, 16, 40, 42, 52, 57, 62, 75, 76-78, 83, 86-88, 93- Hybrid system: system that combines a spallation neutron* 95. source with a subcritical* reactor for the transmutation* of Fast neutron reactors (FR): reactors without moderators* in nuclear waste or for energy production. 78. which the majority of fissions are generated by the high energy neu- Hydrogen. 9, 33, 36, 55, 57, 79, 82, 84, 90-92, 94, 98. trons* produced by fission*, with as little slowdown as possible. 16, 62, 68, 76, 78, 83, 88, 89, 95. Incineration (of Nuclear waste*): destruction of actinides, espe- cially minor actinides*, in nuclear reactors through fission* and Fertile: a matter whose nuclei yield fissile* nuclei when they neutron* capture. 27 absorb neutrons, for example, uranium 238 which leads to pluto- nium 239. Matter is called sterile* if the contrary is true. 16, 17, 67, INES scale: scale of gravity of nuclear incidents and accidents. 74, 75, 77, 93, 95, 96. 30. FIMA: (Fission per Initial Metallic Atom). The FIMA is a combus- Ionising radiation: radiation capable of producing ions when it tion rate unit for nuclear fuel, expressed in terms of the proportion passes through matter. of fissions made in a population of heavy metal atoms. Irradiation: a living organism’s or a material substance’s expo- sure to radiation.

104 Glossary - index MonoCEA GB 5/04/06 15:31 Page 105

Isotopes: forms of the same chemical element whose nuclei have Nuclide: a nuclear type characterized by its number of protons Z, an identical number of protons and a different number of neutrons. its number of neutrons* N and its mass number A, equal to the 16, 18, 27, 73, 75, 96, 98. sum of the number of protons and neutrons (A = Z + N); Radionuclide*:a radioactive isotope*, sometimes also called a ITER: prototype reactor for the study of nuclear fusion, developed radioisotope. in the frame of an international collaboration. See chapter “Other avenues for the distant future: thorium cycle, hybrid systems, Package: a kit made up of packing for transport, storage and/or fusion”. 99, 100. disposal and of specified radioactive* material contents. 20, 31, 60, 61, 63-66. LECI: Laboratoire d’Études des Combustibles Irradiés (Irradiated Fuel Studies Laboratory) at CEA Saclay. 23. Partitioning: chemical process used to separate the elements contained in spent fuel.The PUREX process isolates uranium and Light water: ordinary water as opposed to heavy water. 43, 53, plutonium ; other more advanced processes (DIAMEX, SANEX, 57, 67, 68, 73, 76, 87, 90. GANEX) are under study, in order to separate actinides from lan- Light water reactors (LWR): a family of reactors in which ordi- thanides, or actinides from each other. 8, 21, 59-62, 68-70, 87. nary water is used both as a coolant and as a moderator.The fam- Phénix: prototype of sodium-cooled, fast neutron reactor. See ily of LWRs includes pressurized water reactors* and boiling chapter “Nuclear systems of the future: an international framework water reactors*. 87, 90. for the development of a new generation of nuclear systems”. 62, MeV: mega electron-volt. This unit of energy is generally used to 63, 83, 88. express the energy released through nuclear reactions. 1 MeV Plutonium: element formed by neutron capture on uranium nuclei corresponds to 1.6 10-13 Joules. in the core of nuclear reactors. Plutonium can be recycled in Minor actinides: heavy nuclei formed in a reactor by successive nuclear reactors, for example in the form of MOX* fuel, because capture of neutrons* from the fuel’s nuclei. These isotopes* are its odd isotopes are fissile*. 8, 12, 15-18, 30, 31, 40, 48, 59-62, 67, mainly neptunium (237), americium (241, 243) and curium (243, 70, 75, 77, 83, 87. 244, 245). 8, 16, 19, 31, 59, 61-63, 67, 69, 70, 77, 87, 93, 95-97. Poisons (Neutronic*): elements with a high neutron* capture Moderator: material formed of light nuclei which slow down the capacity, used to fully or partially compensate for excess reactiv- neutrons by elastic scattering. It must capture as few as possible ity* in fissile* environments. Four natural elements have notable so as not to “waste” the neutrons and be sufficiently dense to neutron-absorbing properties: (thanks to its isotope* B 10), ensure an effective slowing down of the neutrons. 12, 53, 75, 76, 78, cadmium, and gadolinium (thanks to its isotopes Gd 155 79, 89. and Gd 157). Some are called “consumable” because they disap- pear progressively during reactor combustion. Some fission prod- MOX (Mixed OXides): mixture of uranium (natural or depleted) ucts* are neutron poisons because they absorb neutrons. and plutonium oxides. 17, 18, 31, 41, 48, 53, 55, 56, 77, 83, 87, 96. Poisoning (nuclear fuel): the phenomenon of neutron capture Neutron: a fundamental electrically neutral particle, whose mass by certain fission products that build up during irradiation (xenon -27 is 1.675·10 kg.This nucleon* was discovered in 1932 by British 135, samarium 149, etc.), which deteriorate the neutron bal- physicist James Chadwick. Neutrons and protons constitute the ance*. atom’s nucleus. Neutrons can provoke fission* reactions in fis- sile* nuclei. This energy is used in nuclear reactors. Potential radiotoxicity (of a certain amount of radionuclides, in waste for example). Potential radiotoxicity, defined as the product Neutron balance: the result of neutron productions and losses in of the radionuclide inventory through the dose “ingestion” factor of a reactor. those radionuclides, is an indicator of the power to harm of this Neutron flux: the number of neutrons crossing a unit surface area quantity of radionuclides in an accident situation. 31, 59. per unit of time. 56, 57, 75, 87, 99. Pressurized water reactor (PWR): reactors in which heat is Neutronics: the study of neutrons*’ path in fissile* and non-fis- transferred from the core to the heat exchanger via the water kept sile environments and the reactions they provoke in matter, in par- under high pressure in the primary circuit to keep it from boiling. ticular in nuclear reactors in terms of multiplication, establishment 79, 87, 89, 90, 95. and control of the chain reaction*. 51, 52, 56, 57, 86, 87, 92, 96. Primary energy: see chapter “Energy in the world”. 33. Neutron spectrum: energy distribution of the neutron* population Processing (of spent fuel): chemical process used to separate present in the reactor core. recyclable nuclides in the spent fuel. The rest is then considered Nuclear fusion: a nuclear reaction in which two light nuclei bind as a waste and receives an appropriate conditioning. (See together to form a heavier nucleus. 98, 100. Vitrification*.) 8, 16, 17, 59, 68, 78. Nuclear system: possible means of constructing nuclear reac- Proliferation: uncontrolled dissemination of the military nuclear tors capable of functioning under satisfactory safety and economic technologies, or of the nuclear matter used by those technologies. conditions, defined mainly through (1) the fuel type, (2) neutron 7, 9, 30, 31, 40, 41, 67, 68, 82, 85, 86, 89, 93, 95, 102. energy involved in the chain reaction, (3) moderator and coolant Radioactive half-life: period after which half the radioactive* type. atoms initially present have disintegrated. 19. Nucleons: particles that make up an atom’s nucleus, i.e. protons Radioactivity: property of certain natural and artificial elements and neutrons*, which are linked together by the strong interac- to spontaneously emit alpha and beta particles or gamma radia- tion that causes nucleus cohesion. tion.This term more generally designates the emission of radiation accompanying the decay* of an unstable element or fission*. 7, 9, 20, 23, 25, 27-29, 31, 32, 51, 59-61, 63, 70, 100.

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Radioecology: study of the transfer of radionuclides into the bios- Thermal-hydraulics: a branch of physics dedicated to heat trans- phere. 28. fers and fluid mechanics. 51, 56, 57, 86, 92. Radionuclide: radioactive isotope (see Nuclide*). Thermal neutrons: also known as slow (or thermalized) neu- trons*, neutrons in thermal equilibrium with the material in which Radionuclide inventory: quantity of fission products and they move at a speed in the order of 2 to 3 km/s. Their energy is actinides contained in irradiated fuel, generally expressed in lower than 1 electronvolt*. 9, 12, 16, 76, 77, 89, 94-96. Bq/gMLi or in g/tMLi (Becquerels or grams per tonne of initial heavy metals). These quantities depend on the type of fuel and Thorium: this heavy element, abundant in nature, could be used the irradiation conditions (combustion rate, etc.). for nuclear energy production. Its isotope Th 232 is fertile and has a fuel cycle analogue to the U 238 fuel cycle. 95. Radon: a radioactive gas resulting from decaying uranium and thorium present in the Earth’s crust. 27, 28. TOE: unit of energy corresponding to a Tonne of Oil Equivalent. Reactivity: deviation from unity of the ratio of the number of neu- Transmutation: transformation of an isotope* into another, more trons produced by fission and the number of neutrons lost in a specifically that of a long-lived radioactive isotope into a short-lived reactor core. In a reactor, reactivity is zero when it is critical*, pos- or a stable isotope* through a nuclear reaction (neutron* cap- itive if it is supercritical* and negative if it is sub-critical*. ture, fission*). 8, 21, 59, 62, 63, 87, 88, 96-98. Reactor CANDU: reactor cooled and moderated by heavy water. Transport (of nuclear matter): see chapter “Nuclear safety and CANDU reactors can use fuel made of natural uranium. 43, 54, security”. 27. 76, 78. Transuranium elements: all of the elements whose atomic num- Reactor Jules Horowitz (JHR): see chapter “The near future: ber is greater than that of uranium.These heavy nuclei result from research supporting the existing nuclear power”. 49. uranium through neutron* capture or radioactive decay* and not from fission*, and can be divided into seven isotope* families: Reactor RBMK: reactor with a water coolant and a graphite mod- uranium, neptunium, plutonium, americium, curium, berkelium and erator.This type of reactor was involved in the Chernobyl accident. californium. 95, 96. 76. UOX: standard fuel for light water reactors* made from uranium Recycling: Re-use in reactor of nuclear matter produced by the oxide enriched* in uranium 235. 16, 55-57, 60, 71, 77, 87. processing* of spent fuel. 8, 9, 17, 18, 40, 53, 59, 61, 62, 63, 67-71, 77, 83-88, 93, 96, 101. Vessel: receptacle containing the core of the reactor and its coolant fluid*. 13, 23, 29, 51, 52, 56, 57, 58. Resources (in uranium): see chapter “Uranium resources”. 73. Vitrification: operation which consists in incorporating waste in a Rheology: branch of mechanics which studies the behaviour of glass melt to give them a stable conditioning under the form of materials under stress situation. 58. storable waste packages. 16, 17, 64. Risk: see chapter “Nuclear safety and security”. 27. Waste (nuclear): unusable residue, result of the utilization of Safety (nuclear): measures taken to mitigate the danger associ- nuclear energy. 7, 9, 16, 17, 19-21, 25, 31, 46, 59-66, 82, 101. ated to nuclear activities or installations, by measuring and control- Zircaloy: an alloy of zirconium and one or several other metals ling the associated risk. 19, 32, 57. (tin, iron, chromium, nickel, niobium) that is particularly resistant Simulation: see chapter “The near future: research supporting from a mechanical and chemical point of view. It is used for fuel the existing nuclear power”. 47. cladding in light water reactors. 15. Sintering: operation which consists in soldering the grains of a metal or ceramic compacted powder, by heating this powder below its melting temperature. 17, 48. Spallation: a nuclear reaction involving a target heavy nucleus and a particle, most often a high energy proton. Through succes- sive reactions, a beam of these particles can produce a large num- ber of neutrons*, among others. A one-billion electronvolt proton projected on a lead target can generate 25-30 neutrons. 78, 96-98. Specific burn-up (or burn-up or combustion rate): total energy released per unit of mass in a nuclear fuel. Generally expressed in megawatt x day per tonne. Stability valley: line of the stable isotopes in a diagram represent- ing nuclides according to their number of protons and neutrons. Storage (of nuclear waste): installation in which nuclear waste packages are stored, with the prospect of an ulterior retrieval. 21, 23, 31, 32, 64-66, 71, 87, 96. Sub-critical: a system is qualified as sub-critical when the num- ber of neutrons* emitted by fission is lower than the number of neutrons disappearing by absorption and by leakage. In this case, the number of fissions observed during successive time intervals decreases. 62, 95, 96, 98.

106 Glossary - index