There is a strong diversity of innovative projects. Forinstance, under the GEN IV label, we find six differentconcepts Sodium Fast Reactor, Lead Fast Reactor, Gas FastReactor, Very High Temperature Reactor (Gas), SupercriticalWater Reactor and Molten Salt Reactor.This diversity and the innovative characteristic are inopposition with a codification status, as code and standards arebased on the recognized industrial feedback. By definition, nocode exists for a real innovative system.Existing codes have thus to be adapted or completed tocover the special features of a new concept. Such a process hasbeen engaged for the AFCEN's RCC-MRx Code (Design andConstruction Rules for Mechanical Components in hightemperaturestructures, experimental reactors and fusionreactors) to adapt this code to the GEN IV reactors new needsfor many years now. In this frame, it appears that there is aparticular expectation on how to proceed to introduce a new material in the code.