Optimized core design for small long-life gas cooled fast reactors with natural uranium-thorium-blend as fuel cycle input

Abstract

Abstract Nuclear power is the use of nuclear reactions that release nuclear energy to generate heat, which most frequently is then used in steam turbines to produce electricity. Presently, the vast majority of electricity from nuclear power is produced by nuclear fission of uranium. The alternative fuel was thorium with the key similarity is that both can absorb neutrons and transmute into fissile elements. Thorium is approximately three times as abundant as uranium in the earth’s crusts, reflecting the fact that thorium has a longer half-life. However, thorium is a fertile material that could not react spontaneously. It needs to be mixed with fissile materials such as uranium or plutonium. Optimized core design and fuel management for small long-life gas cooled fast reactors (600 MWt GCFR) has been performed. The fuel core regions are subdivided into ten parts (region-1 until region-10) with the same volume in the axial direction. The fresh natural uranium-thorium blend is initially put in region-1, after one cycle of 10 years of burn-up it is shifted to region-2 and region-1 filled by fresh natural uranium-thorium blend fuel. This concept is basically applied to all regions in axial core, i.e. shifted the core of (i) region into (i+1) region after the end of 10 years burn-up cycle. For the next cycles, we will add only natural uranium-thorium blend on region-1.The calculation results show that the composition of the fresh fuel for the optimized core consists of 60% thorium-232 and 40% natural uranium.