Scenario of a Symbiotic Nuclear Fleet Composed of PWRs and SFRs

Abstract

Plutonium recycling has two main advantages: to reduce natural uranium consumption by using plutonium as a resource and to limit the area necessary for geological storage. Unfortunately, the requirement to have a negative void coefficient in PWRs (Pressurized Water Reactors) is not compatible with low quality plutonium, forbidding plutonium multi-recycling in such reactors. On the other hand, Sodium Fast Reactors (SFRs) are very good candidates to multi-recycle plutonium, improving its isotopic quality. In France, CEA is developing a new concept of SFRs relevant with GEN IV demands. In this situation, it can be helpful for a utility to study a symbiotic fleet taking advantage of SFRs’ ability to multi-recycle plutonium and keeping a large part of PWRs and the large operating experience associated. Symbiotic nuclear fleet scenarios presented in this study, done in the French fleet context, assume that the plutonium of spent PWR-MOX fuel is reprocessed and loaded in SFRs. Plutonium extracted from spent UOX fuel and spent SFR-MOX fuel is then used to make MOX fuel for PWRs. Thus, all the plutonium produced is re-injected in the fuel cycle and burnt to produce power.The simulations of the scenarios have been carried out using the EDF R&D fuel cycle simulation code TIRELIRE-STRATEGIE. The use of such a code is essential since the composition of the fleet, the fluxes of plutonium and the isotopic vectors are interdependent.The composition of the fleet at equilibrium and the transition phases necessary to reach this state are presented in this article. Compared to a plutonium mono-recycling fleet, these scenarios show that significant natural uranium savings as well as a great reduction of the transuranium elements masses sent to geological storage can be achieved by installing only a small amount of SFRs. However, we also draw attention to the fact that recycling plutonium from spent PWR-MOX fuel in SFRs is not sufficient to obtain a suitable plutonium quality for PWRs. The plutonium quality of spent SFR-MOX fuel in these scenarios leads to a plutonium content in fresh PWR-MOX fuel that exceeds 12 % (for a targeted burn-up of 46 GWd/t). Two options have been studied to overcome this difficulty: decreasing the burn-up of PWR-MOX fuel to decrease the plutonium content loaded or adding radial fertile blankets to SFRs to produce plutonium with a good quality.© 2012 ASME