Fast breeder reactor core concept for heterogeneous minor actinide loading

非均質マイナーアクチニド装荷のための高速増殖炉炉心概念

大木 繁夫 ; 永沼 正行  ; 大久保 努; 田中 健哉

Oki, Shigeo; Naganuma, Masayuki; Okubo, Tsutomu; Tanaka, Kenya

As an alternative method to the homogeneous minor actinide (MA) recycling in fast breeder reactors, a heterogeneous MA loading core concept using a highly concentrated americium (Am)-containing fuel (Am target) is proposed. The Am content (with a small amount of curium) in the heavy metal is assumed to range from 10 to 20 wt% in accordance with the target development scope. A mixed oxide fuel that contains uranium, plutonium, and neptunium is chosen as the base material of the target, so that the targets can generate a level of power equivalent to that of the driver fuels. It was found that a ring-shaped arrangement of Am targets between the inner and outer core regions exhibits a favorable MA transmutation performance without any significant deterioration in the core neutronic characteristics, in comparison with those of a reference homogeneous MA loading case. It should be noted that the Am targets in this loading arrangement can contribute to the suppression of the core power distribution change along with burnup. A series of core designs, including core neutronics, thermal hydraulics, and fuel integrity evaluations, was also carried out for a representative Am target loading case. The design feasibility of the heterogeneous target loading core has been enhanced.