Desain Study of Pb-Bi Cooled Fast Reactors with Natural Uranium as Fuel Cycle Input Using Special Shuffling Strategy in Radial Direction

Abstract

Design study of Pb-Bi cooled fast reactors with natural uranium as fuel cycle input using special radial shuffling strategy has been performed. The reactors utilizes UN-PUN as fuel, Eutectic Pb-Bi as coolant, and can be operated without refueling for 10 years in each batch. Reactor design optimization is performed to utilize natural uranium as fuel cycle input. This reactor subdivided into 6 regions with equal volume in radial directions. The natural uranium is initially put in region 1, and after one cycle of 10 years of burn-up it is shifted to region 2 and the region 1 is filled by fresh natural uranium fuel. This concept is basically applied to all regions. The calculation has been done by using SRAC-Citation system code and JENDL-3.2 library. The effective multiplication factor change increases monotonously during 10 years reactor operation time. There is significant power distribution change in the central part of the core during the BOC and the EOC. It is larger than that in the case of modified CANDLE case which use axial direction burning region move. The burnup level of fuel is slowly grows during the first 15 years but then grow fastly in the rest of burnup history. This pattern is a little bit different from the case of modified CANDLE burnup scheme in Axial direction in which the slow growing burnup period is relatively longer almost half of the burnup history.