Towards a single European strategic research and innovation agenda on materials for all reactor generations through dedicated projects

The goal of the ORIENT-NM action is to produce a single European strategic vision on research and innovation concerning nuclear materials in the EU, serving all reactor generations and nuclear systems. The key in this endeavour is to focus on advanced materials science practices that, combined with digital techniques, will enable acceleration in materials development, manufacturing, supply, qualification, and monitoring, in support of nuclear energy safety, efficiency, economy and sustainability. The research agenda will be rooted in existing virtuous examples of nuclear materials science projects. Here the results of three of them are summarised, thereby covering different reactor applications and families of materials, as well as a range of advanced material research approaches. GEMMA addressed a number of key areas concerning the development and qualification of metallic structural materials for GenIV reactor conditions, focusing on austenitic steels and their compatibility with several non-aqueous coolants, their welds and the modelling of their stability under irradiation. INSPYRE was an integrated project applying a basic science approach to (U,Pu)O2 fuels, to develop physics-based models for the behaviour of nuclear fuels under irradiation and improve fuel performance codes. Modelling was also the focus of the M4F project, which brought together the fission and fusion materials communities to study the effects of localised deformation under irradiation in ferritic/martensitic steels and to develop good practices to use ion irradiation as a tool to evaluate radiation effects on materials

Effect of cationic chemical disorder on defect formation energies in uranium-plutonium mixed oxides

At the atomic scale, uranium-plutonium mixed oxides (U,Pu)O_2 are characterized by cationic chemical disorder, which entails that U and Pu cations are randomly distributed on the cation sublattice. In the present work, we study the impact of disorder on point-defect formation energies in (U,Pu)O_2 using interatomic-potential and Density Functional Theory (DFT+U) calculations. We focus on bound Schottky defects (BSD) that are among the most stable defects in these oxides. As a first step, we estimate the distance R_D around the BSD up to which the local chemical environment significantly affects their formation energy. To this end, we propose an original procedure in which the formation energy is computed for several supercells at varying levels of disorder. We conclude that the first three cation shells around the BSD have a non-negligible influence on their formation energy (R_{D} = 7.0 \{AA}). We apply then a systematic approach to compute the BSD formation energies for all the possible cation configurations on the first and second nearest neighbor shells around the BSD. We show that the formation energy can range in an interval of 0.97 eV, depending on the relative amount of U and Pu neighboring cations. Based on these results, we propose an interaction model that describes the effect of nominal and local composition on the BSD formation energy. Finally, the DFT+U benchmark calculations show a satisfactory agreement for configurations characterized by a U-rich local environment, and a larger mismatch in the case of a Pu-rich one. In summary, this work provides valuable insights on the properties of BSD defects in (U,Pu)O_2, and can represent a valid strategy to study point defect properties in disordered compounds.Comment: 33 pages, 20 figure

Materials for Sustainable Nuclear Energy: A European Strategic Research and Innovation Agenda for All Reactor Generations

Nuclear energy is presently the single major low-carbon electricity source in Europe and is overall expected to maintain (perhaps eventually even increase) its current installed power from now to 2045. Long-term operation (LTO) is a reality in essentially all nuclear European countries, even when planning to phase out. New builds are planned. Moreover, several European countries, including non-nuclear or phasing out ones, have interests in next generation nuclear systems. In this framework, materials and material science play a crucial role towards safer, more efficient, more economical and overall more sustainable nuclear energy. This paper proposes a research agenda that combines modern digital technologies with materials science practices to pursue a change of paradigm that promotes innovation, equally serving the different nuclear energy interests and positions throughout Europe. This paper chooses to overview structural and fuel materials used in current generation reactors, as well as their wider spectrum for next generation reactors, summarising the relevant issues. Next, it describes the materials science approaches that are common to any nuclear materials (including classes that are not addressed here, such as concrete, polymers and functional materials), identifying for each of them a research agenda goal. It is concluded that among these goals are the development of structured materials qualification test-beds and materials acceleration platforms (MAPs) for materials that operate under harsh conditions. Another goal is the development of multi-parameter-based approaches for materials health monitoring based on different non-destructive examination and testing (NDE&T) techniques. Hybrid models that suitably combine physics-based and data-driven approaches for materials behaviour prediction can valuably support these developments, together with the creation and population of a centralised, “smart” database for nuclear materials

Materials for Sustainable Nuclear Energy - The Strategic Research Agenda (SRA) of the Joint Programme on Nuclear Materials (JPNM) of the European Energy Research Alliance (EERA)

This Strategic Research Agenda (SRA) has been prepared by the EERA-JPNM, based on a wide consultation with the scientific and industrial community involved, to identify the research lines to be pursued in the EU to ensure that suitable structural and fuel materials are available for the design, licensing, construction and safe long-term operation of GenIV nuclear systems. Three Grand Challenges have been identified, namely: (i) Elaborate design correlations, assessment and test procedures for the structural and fuel materials that have been selected for the demonstrators under the service conditions expected; (ii) Develop physical models coupled to advanced microstructural characterization to achieve high-level understanding and predictive capability; (iii) Develop innovative materials solutions and fabrication processes of industrial application to achieve superior materials properties, to increase safety and improve efficiency and economy. For structural materials, the requirement of 60 years design lifetime for non-replaceable components is in perspective the most demanding requirement, which includes under its umbrella several issues related with the reasonable prediction of long-term degradation processes: high temperature processes (creep, fatigue, thermal ageing), compatibility with –especially- heavy liquid metal and helium coolants, and effects of low flux prolonged irradiation, with emphasis on welded components in all cases. In terms of testing, there is a need for standardization, especially for sub-size and miniature specimens. The modelling, supported by microstructural characterization, has as its main objective the development of suitable microstructure evolution models to be used as input to models for the mechanical behaviour under irradiation and at high temperature, eventually linking with fracture mechanics. Specific developments are required for coolant compatibility models, as well as for models in support of the use of charged particle irradiation for the screening of new materials solutions, such as those listed above. Concerning fuel materials, the properties and processes that govern its behaviour in pile, on which research effort is focused, are: margin to melting (establishment of phase diagrams and evolution of thermal properties), atomic transport properties and ensuing microstructural evolution, fission product (non-gaseous) and helium (gas) behaviour and transport, mechanical properties (their evolution, subsequent fragmentation and cracking, fuel-cladding mechanical interaction), and compatibility with cladding and coolant (internal cladding corrosion, chemical interactions especially in case of severe accident). These are all addressed from both an experimental and a modelling perspective. Besides the obvious need of adequate financial resources in order to address the research problems outlined in this SRA, as well as the necessary corollaries, four recommendations emerge that this document is intended to bring to the attention of stake-holders, particularly decision-makers: R1: Data from materials property measurements after exposure to relevant conditions are the essential ingredient for robust design curves and rules. Plenty of data were produced in the past that are now de facto unusable; this is either because they are covered by confidentiality or because they were not properly archived. Correct data management to guarantee availability for future re-assessment is therefore essential and should be encouraged and fostered. In particular, financially supported policies to foster data sharing and encourage old data disclosure should be implemented. R2: Some infrastructures are absolutely essential to enable the correct qualification of nuclear materials, not only irradiation facilities, but also suitable ‘hot’ cells where active materials can be safely handled and tested, nuclearized characterization techniques, loops and pools for compatibility experiments, etc. They are also crucial for education and training of young researchers and operators. These infrastructures are costly to build and maintain. Other research facilities are, on the other hand, more common and sometimes redundant. A rational and harmonised, pan-European management of infrastructures, based on joint programming, including trans-national infrastructure renewal planning and a scheme for facility sharing and exploitation, would be highly desirable and, at the end of the day, beneficial for all. R3: International cooperation with non-EU countries where research on nuclear materials is pursued can be very valuable for Europe. Quite clearly, the goals of this cooperation are in the end the same as in the case of internal European cooperation, namely coordination of activities, sharing of data, and access to infrastructures. Currently, however, the instruments available in Europe for international cooperation are not sufficiently attractive to motivate significant cooperation with non-EU researchers. Efforts should be made to improve their attractiveness and ease of access. International organisations such as OECD.NEA, IAEA, but also Euratom and JRC for the connection with GIF, have here a crucial role. R4: The nuclear materials research community in Europe is currently strongly integrated and engaged in thriving collaboration, in a bottom-up sense. This is in contrast with the inadequacy of the top-down instruments offered to make this integration efficient and functional. This SRA is largely the result of matching bottom-up research proposals with top-down strategies. The appropriate instrument to allow this community to deliver according to the SRA goals should provide the conditions to implement the agreed research agenda and to set up suitable E&T&M schemes that allow knowledge, data, and facility sharing. Since the financial support of Euratom will never be sufficient, earmarked funding from the MS dedicated to support integrated research on nuclear materials is crucial. In this sense, a co-fund instrument, such as a European Joint Programme, seems to be most suitable.JRC.G.I.4-Nuclear Reactor Safety and Emergency Preparednes

Using basic research to improve the simulation of MOX fuel behaviour

International audienceNuclear fuel constitutes an essential component of the performance and safety of nuclear reactors. It is composed of complex materials with specific properties and is subjected under irradiation to a large number of diverse but interconnected phenomena. A better understanding of the properties of fuel materials and of the mechanisms underlying their changes under irradiation is key to the development of more accurate and predictive codes for the simulation of fuel elements. An efficient approach to improve the understanding of fuel behaviour is to complement the examination of neutron-irradiated materials by a basic research approach combining separate effect experiments on model, surrogate or ion-irradiated materials and multiscale modelling from the atomic to the mesoscopic scale. We will present the approach developed on (U,Pu)O2 fuels in the INSPYRE H2020 project and illustrate the results obtained on significant operational issues and on the development of constitutive laws for the behaviour of nuclear fuels.INSPYRE has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 754329. This project is part of the research activities portfolio of the Joint Programme on Nuclear Materials

Behaviour and Properties of Nuclear Fuels

Nuclear reactor fuel is probably one of the most complex materials in modern technology. This is due to a variety of reasons. First of all, the chemistry of the fuel materials is complex. In compounds the actinide elements such as uranium and plutonium exhibit various oxidation states depending on the thermodynamic conditions with concomitant charge compensation taking place through lattice defects (vacancies or interstitials), often without substantially changing the crystal structure but strongly affecting the material properties. In this chapter, the physical and material properties of nuclear fuel and its behaviour are discussed from experimental and theoretical point of view,JRC.G.I.3-Nuclear Fuel Safet

Development and application of an interatomic potential for the investigation of mixed oxide compounds containing Americium

International audienceAmericium is a chemical element produced by neutron capture in nuclear reactors, whose strong radiotoxicity is a major issue for the management of nuclear waste. One solution envisaged to reduce the amount of americium in the waste is to separate it from the other elements present in the fuel after its stay in the reactor and to re-irradiate in order to transform it into a less radiotoxic element thanks to a transmutation reaction. [1].This requires, among other things, a very good knowledge of the thermodynamic properties of the Am bearing oxides in order to control the process of manufacturing fuels containing this element and to predict the phases formed under irradiation as a function of the composition and the temperature.Atomic scale modelling, and in particular, methods using empirical interatomic potentials, is a suitable tool for the calculation of thermodynamic properties to complement experimental characterizations. It requires, however, precise potentials describing the interactions between atoms. A formalism adapted to actinide oxides is that of the n-body potential developed by Cooper, Rushton and Grimes (CRG) for many simple oxides, including UO2, AmO2, PuO2 [2,3] and for the (U,Th)O2 [4] and (U,Pu)O2 mixed oxide [5].We parameterized a potential for Americium with the oxidation state + III in the CRG formalism and validated it against available experimental data. The potential was then applied to determine thermodynamic properties of (U,Am)O2 as a function of Am content and/or temperature, in particular enthalpy increments, heat capacity and melting temperatures.References1 Report on sustainable radioactive-waste-management (2012): http://www.cea.fr/english/Documents/corporate-publications/report-sustainable-radioactive-waste-management.pdf 2 M.W.D. Cooper, M.J.D. Rushton, R.W. Grimes, J. Phys.: Condens. Matter 26, 105401 (2014) 3 Potential Model for Actinide Oxides and their Solid Solutions, http://abulafia.mt.ic.ac.uk/potentials/actinides/v1.2/index.html 4 M.W.D. Cooper, S.T. Murphy, P.C.M. Fossati, M.J.D Rushton, R.W. Grimes, Proc. R. Soc. Lond. A Math. Phys. Sci. 470, 20140427(2014)5 C. Takoukam-Takoundjou, E. Bourasseau, M. J. D. Rushton, V. Lachet, J. Phys.: Condens. Matter 32, 505702 (2020

Towards a single European strategic research and innovation agenda on materials for all reactor generations through dedicated projects

The goal of the ORIENT-NM action is to produce a single European strategic vision on research and innovation concerning nuclear materials in the EU, serving all reactor generations and nuclear systems. The key in this endeavour is to focus on advanced materials science practices that, combined with digital techniques, will enable acceleration in materials development, manufacturing, supply, qualification, and monitoring, in support of nuclear energy safety, efficiency, economy and sustainability. The research agenda will be rooted in existing virtuous examples of nuclear materials science projects. Here the results of three of them are summarised, thereby covering different reactor applications and families of materials, as well as a range of advanced material research approaches. GEMMA addressed a number of key areas concerning the development and qualification of metallic structural materials for GenIV reactor conditions, focusing on austenitic steels and their compatibility with several non-aqueous coolants, their welds and the modelling of their stability under irradiation. INSPYRE was an integrated project applying a basic science approach to (U,Pu)O2 fuels, to develop physics-based models for the behaviour of nuclear fuels under irradiation and improve fuel performance codes. Modelling was also the focus of the M4F project, which brought together the fission and fusion materials communities to study the effects of localised deformation under irradiation in ferritic/martensitic steels and to develop good practices to use ion irradiation as a tool to evaluate radiation effects on materials