OPTIMIZED SURFACE TREATMENTS AND MANUFACTURING TECHNIQUES FOR COMPONENTS OF SODIUM COOLED FAST REACTORS

摘要

The French sodium prototype ASTRID should work from 2026 ;it must satisfy the requirements of "Generation IV" with regard to lifetime, safety and efficiency;means are sought in order to optimize the ageing behavior of components. Coatings that seem favorable concerning the fuel claddings and wrappers of ASTRID must be further checked. Other surface treatments are considered for less irradiated components, in order to improve the residual stresses near the surface of metallic pieces ; if the stresses get compressive , these treated components get less brittle and "stress corrosion cracking"(SCC) may be avoided. French and Chinese establishments have developed "ultrasonic shot peening" using stainless steel balls or needles. Concurrently, US and Japanese companies have carried out "water jet peening" and nanopulse "Laser Peening" treatments; These "laser peening " treatments have already enhanced efficiently SCC and fatigue behavior of both AISI 316 pieces and 12%Cr ferrochromium blades. Laser treatments with lower power requirements improve also the behaviour of surfaces with regard to SCC, roughness or pitting corrosion Passivating chemical techniques are required too in order to stabilize the protective chromine layer at the surface of metallic pieces. Peening and passivating techniques should be combined in the future.