Development of Cask Basket for High Burnup and MOX Spent Fuels

At present, in Light Water Reactor the shift to high bumup of nuclear fuel is going on, and also the use of MOX fuel is planned (e.g., Ichikawa 1993). These high bumup and MOX spent fuels have higher radioactivity, higher decay heat, and higher emission of gamma-ray and neutron. So it is necessary that a new cask and cask basket be developed. The cask basket is very important to keep subcriticality of a system of spent fuels and remove decay heat. Using a single superior material which fulfills the requirements of neutron absorption, heat removal, and mechanical strength, we can design a simple basket structure and reduce costs. We investigated some structural materials which may or may not contain a high level of boron or enriched boron, such as (1) Borated stainless steel (S.S.), (2) Borated aluminum alloy, and (3) Composite material (three-layered clad plate composed of B-S.S./Cu/B-S.S. structure).