Prediction of nuclear materials behavior for reactors life-span extension towards a multi-scale approach dedicated to microstructure and mechanical properties of irradiated materials
Résumé
In the nuclear field, in-core materials used in fission reactors are subjected to severe conditions due to thermal, irradiation, mechanical and chemical solicitations. The investigation of the behavior and durability of metallic alloys under such conditions requires an understanding of many mechanisms (physical, chemical) with a multi-physics/multi-scale approach. The life-span prediction and extension of current PWRs are an important concern from an economical and a safety point of view. Such predictions rely on material ageing studies of key components (pressure vessel, internals). For the 3rd and forthcoming 4th generation reactors, an accurate understanding of ageing mechanisms is needed to reduce the degree of uncertainty in the prediction of temperature and neutron effects. Multi-scale approaches have an advantage over standard engineering approaches, because they are less reliant on empirical models. The main challenge is to understand how neutron irradiation-induced primary damage will impact the main components' long-term macroscopic mechanical response. Multi-scale tools require the development of models at each scale, which need to be experimentally validated and linked. Over the past few years, the CEA developed the MATIX_P platform dedicated to multi-physics/multi-scale numerical simulation for the prediction of the hardening of PWR RPV bainitic steel and the irradiation-creep of F-M steels for a SFR demonstrator. The MATIX_P platform is presented with a focus on coupled studies between clusters dynamics (CD), dislocation dynamics (DD) and non-linear mechanical simulation. Emphasis will be put on the linking of codes CRESCENDO, a CD code using chemical rate equations to compute the evolution of nanostructures induced by irradiation; NUMODIS, a DD code dedicated to materials plastic deformation, based on dislocations behavior; and the AMITEX_FFTP tool, an FFT solver for non-linear mechanical simulations for 3D computation of polycristalline aggregates mechanical behavior. Examples of results obtained for the computation of irradiated materials micromechanical properties will be provided.
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