Development of metallic fuel for fast reactor

Most fuel types of the earliest fast breeder reactors were focused on metallic fuels composed of U, Pu or U-Pu alloys. Experiences in-core indicate that the swelling of metallic fuels is so severe that the cladding begins to fail at a low burnup, moreover the solidus temperature of uranium or uranium-plutonium fuel and eutectic temperature with stainless steel cladding materials are low and made it impractical to use metallic fuels in a commercial reactor. The paper reviews development of metallic fuels of fast reactors and ways to solve main problems of it, and then gives the improved and feasible design options for metallic fuels. Meanwhile the early and later irradiation experiences of metallic fuels were summarized, including the limits of burnup which had been demonstrated. (authors)