Symbiotic equilibrium between Sodium Fast Reactors and Pressurized Water Reactors supplied with MOX fuel

Highlights: • Simple methodology to study advanced cycle options with code precision. • Study of the symbiotic equilibrium between breeder SFR and MOX PWR. • Solutions found for various and complex reprocessing strategies. - Abstract: The symbiotic equilibrium between 1.51 GWe breeder SFR (Sodium Fast Reactors) and 1.6 GWe EPR™ (European Pressurized water Reactors) is studied. EPR™ are only supplied with MOX (Mixed OXide) fuel to avoid the use of natural uranium. The equilibrium is studied by considering the flows of plutonium. Its isotopic composition is here described by a single real number referred to as the Pu grade. Plutonium flows through both reactor types are characterized by using linear functions of the Pu grade in new fuels. These functions have been determined by fitting data from a former scenario study carried out with the COSI6 simulation software. Two different reprocessing strategies are considered. With joint reprocessing of all spent fuels, total and fissile plutonium flows balance for a unique fraction x of EPR™ in the fleet, equal to 0.2547. This x value is consistent with the results reported in the former scenario study mentioned above. When EPR™ spent fuels are used in priority to supply SFR (distinct reprocessing), x reaches 0.2582 at most. COSI6 simulations have been performed to further assess these results. The EPR™ fraction in the fleet at symbiotic equilibrium barely depends on the applied reprocessing strategy, so that the more flexible joint reprocessing constitutes the reference option in that case.