Safety analysis of nitride fuels in cores dedicated to waste transmutation

We have investigated safety characteristics of nitride fuels in critical and sub-critical cores dedicated to waste transmutation. It is shown that decomposition of actinide nitrides followed by escape of nitrogen gas from the core will not lead to positive reactivity feedback, provided that a) 15N enriched nitrogen is used, and b) pin pitches are sufficiently large. Hence the reason for nitride fuels not being licensed for use in Phenix is not valid in the context of P and T, where use of 15N enriched nitrogen in nitride fuel fabrication is a prerequisite, and neutron economy is much less constrained than in FBRs. Consequently, the main safety concerns related to use of nitride fuels can be eliminated by proper core and fuel design. (author)