An axially multilayered low void worth liquid-metal fast breeder reactor core concept

A new core concept with a negative sodium void reactivity coefficient has evolved. The core is composed of two core layers in the axial direction. The core layers are separated by an internal blanket, the central region of which comprises a neutron-absorbing material such as boron carbide or tantalum. Consequently, the two core layers are completely decoupled as regards neutronics, leading to an effective increase in neutron leakage from the core region when sodium is voided. This design is expected to be free from the disadvantages of a large core radius, as seen in a conventional spoiled core such as a pancake core. In this paper the design is described in detail, and its application to a 300-MW (electronic) metal fuel core and to a 450-MW (electric) minor actinide burned core is given as an example