Analysis of neutron spectrum modification effects on plutonium vector degradation and minor actinide production in a BWR 100% MOX

The decision to reprocess spent fuel is a fundamental aspect in the context of the optimization of nuclear material management. In France today, 17 pressurized water reactors (PWR) are partially loaded (30%) with MOX fuel : it is essential, in order to assure optimal use of plutonium, to perform analyses to achieve 100% MOX cores. Boiling water reactors (BWR) form a third of the world's nuclear power plants and can, among other types of reactors, participate in this objective: recycling research is therefore of great relevance for this type of core, as it presents specific features related to the variation of the steam fraction. In modeling of 100 % MOX BWR assemblies, several aspects are taken into account, such as the choice of plutonium content and the concentration in burnable absorbers, with a view to optimizing the level of reactivity and the power distribution. Analysis of the fine structure of the neutron flux permits describing its modification according to the variation of the void fraction in the assembly and interpreting the results with respect to plutonium degradation and the production of minor actinides. (authors)