Keywords: CANDLE, natural uranium, burn-up levels, effective multiplication factors, core radius, core axial width, radial reflector width, axial reflector width, lead bismuth cooling, fast reactors, fuel enrichment, fuel reprocessing, nuclear power plants, NPP, nuclear energy, nuclear power
Design study of long-life Pb-Bi cooled fast reactor with natural uranium as fuel cycle input using modified CANDLE burn-up scheme
This paper reports a conceptual design study of Pb-Bi cooled fast reactors with a fuel cycle that needs only natural uranium input. In this design, the CANDLE burn-up strategy is slightly modified by introducing discrete regions. The reactor cores are subdivided into several parts with the same volume in the axial directions. The natural uranium is initially put in region 1, after one cycle of ten years of burn-up it is shifted to region 2 and region 1 is filled with fresh natural uranium fuel. This concept is applied to all regions. From the parametric survey results, the region shuffling scheme and fuel volume fraction have large effect on the criticality of the core. Also, by putting regions 1 and 2 near region 10, we get some significant gain in effective multiplication factors. Core radius, core axial width, radial reflector width and axial reflector width have some impact on the initial effective multiplication factor value, but not as great.