Abstract
The French sodium cooled nuclear prototype ASTRID should be built by 2020 at the earliest, while taking account "Generation IV" criteria; innovative requirements are a long operational life-time (60 years) and a better efficiency (around 40%) implying higher temperatures; thus an improved selection of materials is needed. The good behaviour of AISI316L(N), up to 550℃, must be confirmed; therefore pipes and tubes of French dismantled reactors Phenix and Superphenix should be characterized. Residual stresses of components should be better estimated in order to avoid delayed cracking. Further experiences and CALPHAD computations should be carried out concerning ageing in penalizing conditions. Owing to creep under irradiation issue, conventional materials and chromium ODS steels will both be assessed for fuel wrapping and cladding. The disruptions in steam generator tubes should be minimized and controlled; the design and geometry of steam generators must be chosen before defining the corresponding materials. Owing to its thermal behaviour, Modified 9Cr1Mo may be used if it's proven that it withstands penalizing conditions in presence of sodium; we must check whether it is compatible with austenitic steels in the same circuit. New thermal and mechanical treatments, appropriate manufacturing processes may improve the chosen materials.
