Design research of small long life CANDLE fast reactor

The feasibility of a small long life fast reactor with CANDLE burn-up concept was investigated. It was found that a core with 1.0 m radius and 2.0 m length can bring about CANDLE burn-up with nitride (enriched N-15) natural uranium as fresh fuel. Lead–Bismuth is used as coolant. From equilibrium analysis, we obtained the burn-up velocity, output power distribution, core temperature distribution, etc. The burn-up velocity is less than 1.0 cm/year, which easily permits a long core life design. The averaged core discharged fuel burn-up is about 40%. For better understanding of the effect of the coolant to fuel volume ratio, comparison was made among five cases. In these cases the coolant channel radii were different from one case to another, while fuel pin pitch was fixed. Comparisons were also made with a fixed coolant channel radius and different fuel pin pitches. A simulation of core operation is implemented and the results show that the present design can establish the long time steady CANDLE burn-up successfully without a burn-up control mechanism.