Conceptual Design Study of Small 400 MWt Pb-Bi Cooled Modified Candle Burn-Up Based Long Life Fast Reactors

In this paper conceptual design study of modified CANDLE burn-up scheme based 400 MWt small long life Pb-Bi Cooled Fast Reactors with natural Uranium as Fuel Cycle Input has been performed. In this study the reactor cores are subdivided into 10 parts with equal volume in the axial directions. The natural uranium is initially put in region 1, 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, i.e. shifted the core of I’th region into I+1 region after the end of 10 years burn-up cycle. For small reactor core, it is important to apply high breeding material, so that high volume fraction of 60% fuel volume fraction nitride fuel is applied. The effective multiplication factor initially at 1.005 but then continuously increases during 10 years of burn-up. The peak power density initially about 307 W/cc but then continuously decreases to 268 at the end of 10 years burn-up cycle. Infinite multiplication factor pattern change, conversion ratio pattern change, and Pu-239 accumulation pattern change shows strong acceleration of plutonium production in the first region which is located near the 10th region. Maximum discharged burn-up is 31.2% HM.