Conceptual design study of Hyb-WT as fusion–fission hybrid reactor for waste transmutation

•Conceptual design study of fusion-fission hybrid reactor for waste transmutation.•MCNPX and MONTEBURNS are compared for transmutation performance of WT-Hyb.•Detailed neutronic performance of final optimized Hyb-WT design is analyzed.•A new tube-in-duct core design is implemented and compared with pin type design.•Study shows many aspects of hybrid reactor even though scope was limited to neutronic analysis.

This study proposes a conceptual design of a hybrid reactor for waste transmutation (Hyb-WT). The design of Hyb-WT is based on a low-power tokamak (less than 150 MWt) and an annular ring-shaped reactor core with metal fuel (TRU 60 w/o, Zr 40 w/o) and a fission product (FP) zone. The computational code systems MONTEBURNS and MCNPX2.6 are investigated for their suitability in evaluating the performance of Hyb-WT. The overall design performance of the proposed reactor is determined by considering pin-type and tube-in-duct core designs. The objective of such consideration is to explore the possibilities for enhanced transmutation with reduced wall loading from fusion neutrons and reduced transuranic (TRU) inventory. TRU and FP depletion is analyzed by calculating waste transmutation ratio, mass burned per full power year (in units of kg/fpy), and support ratio. The radio toxicity analysis of TRUs and FPs is performed by calculating the percentage of toxicity reduction in TRU and FP over a burn cycle.