A design study of Pb-Bi-cooled fast reactors with natural uranium as the fuel cycle input

Abstract

A conceptual design study of Pb-Bi-cooled fast reactors in which the fuel cycle needs only natural uranium input has been performed. In this design, the reactor cores are subdivided into several parts with the same volume. The region with natural uranium is put in the central core and the outer region is arranged with increasing plutonium content. In some cases, the region with natural uranium content can be put in the most outer part of the core. The arrangement of the plutonium content takes account of the criterion that the fuel in a certain part must be fit for fresh fuel in the next higher-enrichment region. Therefore, at the end of a long-life operation, we just need to supply natural uranium fuel to the blanket region and move to the next region. As an example using the SRAC and FI-ITB CH code systems, we have a core with a 15-20 year lifetime per subcycle.