Speaker
Description
Long-lived fission products (LLFPs) are one major factor of the radioactivity and decay heat of high level wastes produced by light water reactors. Transmutation of LLFPs into non-radioactive or short-lived nuclides is an efficient way to reduce the amount of high level waste. Earlier studies have proposed to use a part of the breeding blanket of a fusion reactor to transmute LLFPs. The earlier studies focused mainly on the amount of LLFPs that can be transmuted. Loading LLFPs in the limited space, however, affects the characteristics of the blanket system, such as a decrease of the tritium breeding ratio (TBR) and nuclear heating.
In this study, the feasibility of LLFPs transmutation using a fusion reactor was discussed. More specifically, the amounts of LLFPs transmuted, the TBR, and the nuclear heat generated were evaluated by a numerical analysis. Neutron transport and burn-up analyses were conducted by using MVP-2.0 and MVP-BURN. A simple model of LHD type helical fusion reactor FFHR-d1 was used to obtain the amount of the target nuclide reduction and the TBR. One of the target nuclides, Se-79, Zr-93, Tc-99, Pd-107, I-129, or Cs-135 were loaded into the breeding blanket. As a result, when the amount loaded was 10% of the breeding blanket volumetric ratio, the effective half-life was shorter than the decay half-life. By an evaluation using a support factor, which refers to the number of million kW class light water reactors that can be covered by the transmutation reactor in one year. For several nuclides the support factor was less than 1. This means the amount of LLFPs transmuted needs to be raised by changing conditions. Other evaluations of the TBR and amount of nuclear heat generated were conducted and the feasibility was discussed.
