The 316L with controlled nitrogen austenitic stainless steel is widely used in nuclear construction. The main components of Superphenix (SPX) as the main vessel, internals, intermediate heat exchangers and piping loops operating at high temperature, have been made using this grade. The RCC-MR code has gathered the feedback from the SPX construction. Later the results of European Fast Reactor R&D Programs have been integrated also in the code. Creep strain laws, cyclic and fatigue curves, and fatigue-creep interaction diagram are available in the RCC-MR database, but also it can be found specific filler metal for welding, and dedicated Reference Procurement Specifications. Today, this material, referred to as “316L with controlled nitrogen”, tabulated in RCC-MR is still relevant for current reactor projects. The Indian Fast Breeder Reactor (PFBR) uses this austenitic stainless steel and ITER has selected this alloy for the Vacuum Vessel, with a few additional requirements to comply with its own technical constraints — 316L(N) ITER Grade —. In France, the Sodium Fast Reactor Project (SFR) keeps using the 316L with controlled nitrogen for its major components in sodium with a new challenge regarding the extension of design life to 60 years and confirming its ability to be manufactured using new technologies (large forgings, automatic welding…). In this way, studies are carried out either to validate the current rules or to propose new ones. In particular, the validation of the negligible irradiation curve and the determination of a suitable thermal ageing coefficient, are under consideration, for base metal and for weldments too. Future edition of RCC-MR will include the conclusion of these works. The objective of this paper is to recall the main current data available for 316L with controlled nitrogen and to discuss the approach adopted to take into account for this grade the extension of design life.

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