Concept of a fast breeder reactor to transmute MAs and LLFPs

The long-term issues of nuclear power systems are the effective use of uranium resources and the reduction of radioactive waste. Important radioactive wastes are minor actinides (MAs: ²³⁷Np, ²⁴¹Am, ²⁴³Am, etc.) and long-lived fission products (LLFPs: ¹²⁹I, ⁹⁹Tc, ⁷⁹Se, etc.). The purpose of this study was to show a concept that can simultaneously achieve the breeding of fissile materials and the transmutation of MAs and LLFPs in one fast reactor. Transmutation was carried out by loading innovative Duplex-type MA fuel in the core region and LLFP-containing moderator in the first layer of the radial blanket. Breeding was achieved in the core and axial blanket. As a result, it was clarified that in this fast breeder reactor, a breeding ratio of approximately 1.1 was obtained, and MAs and LLFPs achieved a support ratio of 1 or more. The transmutation rate was 10.3%/y for ²³⁷Np, 14.1%/y for ²⁴¹Am, 9.9%/y for ²⁴³Am, 1.6%/y for ¹²⁹I, 0.75%/y for ⁹⁹Tc, and 4%/y for ⁷⁹Se. By simultaneously breeding fissile materials and transmuting MAs and LLFPs in one fast reactor, it will be possible to solve the long-term issues of the nuclear power reactor system, such as securing nuclear fuel resources and reducing radioactive waste.