The feasibility of 100% mixed-oxide (MOX) fuel recycling in a standard pressurized water reactor (PWR) is explored. The plutonium neutronic specificity is analyzed and compared with uranium. The objective is to identify the generic aspects that could lead to current PWR design modifications. The plutonium isotopic composition was taken as a parameter.

Accidents dealing with a change of the moderator density are of particular interest (especially considering that control worth is significantly reduced with MOX fuel). Study of core global draining leads to the following conclusion: Only very poor quality plutonium fuel (low fissile content) cannot be used in a 900-MW(electric) PWR because of a positive global draining reactivity effect. Study of the cooling accident (increase of moderator density) proves that the spurious opening of a secondary side valve is the most penalizing scenario in the case of MOX fuel utilization. The core reactivity was controlled in this study by 57 control rod clusters made of B4C rods having a 90% 10B content and a hafnium clad. The hypothetical return to criticality depends on plutonium isotopic composition. But the core is kept subcritical for all isotopic compositions provided an increase of the soluble boron 10B content up to a value of 40%. No major obstacle to the 100% MOX 900-MW(electric) PWR feasibility was found.