Treatment and recycling of spent nuclear fuel (2008)

Subsequent to its in-reactor dwell time, spent fuel still contains large amounts of materials that are recoverable, for value-added energy purposes (uranium, plutonium),  together with fission products, and minor actinides, these making up the residues from nuclear reactions. The treatment and recycling of spent nuclear fuel, as implemented in France, entail that such materials be chemically partitioned. The development of the process involved, and its deployment on an industrial scale stand as a high achievement of French science, and technology. Treatment and recycling allow both a satisfactory management of nuclear waste to be implemented, and subsantial savi,ngs, in terms of fissile material. Bolstered of late as it has been, due to spectacularly skyrocketing uranium prices, this strategy is bound to become indispensable, with the advent of the next generation of fast reactors. This monograph surveys the chemical process used for spent fuel treatment, and its variants, both current, and future. It outlines currently ongoing investigations, setting out the challenges involved, and recent results obtained by CEA.

Nuclear industry has taken care very early of the future of its waste.  This has resulted in proven processes, such as intermediate-level  waste cementation, and minor-actinide and fission-products solutions vitrification. Waste conditionning is but one step in the waste management process from waste generation to the final site. Yet, this a key step, undoubtely, for how waste is conditioned stronly depends upan what is planned for the waste ulterior fate. Similarly, how much reliable the waste package  behavior can be in the long term is a basic factor in waste storage and disposal. France’s leading role in waste conditioning is a major  asset likely to be used not only in the international, industrial context, but also for the better social acceptability, as it shows the public that technical solutions do exist to address this concern.  The monograph gives an overview of state of knowledge in nuclear waste conditionning, and describes research work under way, highlighting the related challenges and the CEA’s recent advances.

Fuel is one of the essential components in a nuclear reactor. It is within that fuel that nuclear reactions take place, i.e. fission of heavy atoms, uranium and plutonium. Fuel is at the core of the reactor, but equally at the core of the nuclear system as a whole. Fuel design and properties influence reactor behavior, performance, and safety. Even though it only accounts for a small part of the cost per kilowatt-hour of power provided by current nuclear power plants, good utilization of fuel is a major economic issue. Major advances have yet to be achieved, to ensure longer in –reactor dwell-time, thus enabling fuel to yield more energy, and improve ruggedness. Aside from economics, and safety, such strategic issues as use of plutonium, conservation of ressources, and nuclear waste management have to be addressed, and true technological challenges arise. This monograph surveys current knowledge regarding in-reactor behavior, operating limits, and avenues for R&D. It also provides illustrations of ongoing research work, setting out a few noteworthy results recently achieved.

Research reactors are necessary basis for nuclear energy development and evolution. These reactors are those which paved the way to nuclear energy use, with the divergence of the first atomic pile CP-1 in 1942 at Chicago, and then, as early as the liberation, the divergence of the French atomic puile ZOÉ in 1948 at Fort de Châtillon. For they so demonstrated the ability to generate and control nuclear chain reaction, which was then a major technological innovation, indeed. Since that time, they have kept on with their contribution, making it possible to measure neutron characteristics of reactors cores, investigate materials and fuels behavior under irradiation, study the consequences of accident situations, validate new concepts as well as prototypes, and ensure teaching and operator training on actuel nuclear facilities. In addition, research reactors are also implemented to meet research needs in Basic Physics to investigate  matter’s structure, as well as in various areas of industrial applications. Furthermore, they stand as an unrivaled tool to produce radionuclides for medical uses such as diagnosis and radiation therapy. This diversity of uses is echoed by a very wide variety of facilities, together with activities often performed within an international framework, and relating not only to reactor design and operation, but also to programs developed in these reactors.

Neutronics (or neutron physics) is the study of neutron paths through matter, of conditions for a chain reaction, and of alterations in matter's composition induced ny nuclear reactions. It makes it possible to design and operate nuclear reactors and fuel cycle facilities. Using data from the quantum world (i.e., interactions between neutrons and atomic nuclei) to compute quantities such as a reactor's power, neutronics fills a gap between the microscopic and the macroscopic worlds. Due its multiscale character it works on time, space  and energy scales extending over more than a dozen orders of magnitude. Born in 1932 with neutron discovery, neutronics is a fully mature science which however keeps evolving: for the steady increase in computer power upsets computaional methods, questions experiment's status, and broadens the outlooks of numerical simulation. One of the current challenges is coupling neutronics with thermal-hydraulics and thermal-mechanics so as to simulate reactor behavior. This monograph gives an overview of neutronics referring to both research and applications, and highlights some outstanding results recently obtained.

Sodium-cooled nuclear reactors (2014)

The first nuclear reactor that generated electric power, in 1951, was a liquid metal-cooled fast neutron reactor. In the following years nineteen fast neutron reactors using sodium as coolant were constructed, first as research nuclear reactors, and then as power reactors. This monograph describes that history as well as the operating experience feedback gained with those reactors, among which the three French reactors RAPSODIE, PHÉNIX and SUPERPHÉNIX: design, materials, measurements, instrumentation, in-service inspection, components, operating experience reviews, etc. The design principles of this reactor type are also detailled, highlighting their significant potential assets: the ability to burn all of the uranium fed to it, which would ensure world power supply for thousands of years; the ability to recycle all of the plutonium and uranium arising from the spent fuel treatment, thereby closing the cycle, which would minimize ultimate waste. Today two high-power sodium-cooled fast reactors are being constructed, one in India, and the other in Russia, and a number of projects are under study, among which the ASTRID project in France. This Monograph reviews the status of these developments in 2013. The deployement of this promising technology is slowed down, espececially due to overcost in constructing these reactors in contrast with the water reactor type. The perspectives of this deployment are analyzed in a technico-economic chapter, in relation to the uranium resource evolution.

Nuclear materials - Structural Materials Modeling and simulation (2019)

Materials are the key (or showstopper) of broad areas of industry, and, more specifically, of nuclear industry. The safety and operating time of nuclear reactors, and the feasibility of fuel cycle operations are dependent on the materials used. Nuclear materials are harshly treated, indeed, as they are exposed to loading due to mechanical, thermal, chemical and radioactive conditions. The latter often act in synergy (stress corrosion, irradiation creep…). The first three types of loading are “classic”, but the last one (irradiation) is specific of nuclear materials. With the purpose of guiding the design of these materials, and predicting their behavior, modeling and simulation tools have become indispensable. So a wide range of modeling tools has been developed, from the atomic to the macroscopic scale. These models have to be interconnected, and validated by experiments with well-defined targets, so as to make sure that the involved phenomena are well controlled. These experiments are first conducted onmodelmaterials of simple structure and composition, before dealing with the more complex case of real materials subjected to multiple stresses. Such is the scientific approach described in thisMonograph. The reader will find in it a simple description of modeling methods for materials under irradiation, and of related experimental methods, as well as a few recent highlights.