Metallic fuel for Na-cooled reactors with an extended burnup cycle

In recent years, various reactors and fuel-cycle concepts have been proposed as alternatives to the (Pu-U)O2 mixed-oxide fuel cycle. This interest has been stimulated by the need to utilize the U resources and also to contribute to the solution of the proliferation problem. To date, essentially all combinations of fuel-cycle mixes have been considered, except the denatured FBR operating on an extended burnup cycle. The basic feature of the proposed concept is a 233U-238U LMFBR using metallic fuel, enriched at the beginning of life to about 6 at.% cooled with Na, and designed to operate in such a way that, once the reactor is built, it only needs natural or depleted U as feed for the rest of the life of the reactor. The denatured breeder simply enriches the U to the level necessary to maintain criticality. Calculations show that the reactivity swing over each refueling interval, the fuel-pin performance and some safety parameters are all within current technology constraints. (author)