Spent fuel cask and basket used for the cask

A basket is disposed at the inside of a hollow cask main body. Partition members are disposed at the inside of an outer cylinder in the basket, and lattice-like fuel assembly containment spaces are formed by the partition members. The partition members are made of composite steel plates each comprising a metal plate of excellent heat conductivity such as copper, aluminum or nickel, bonded at both surfaces thereof, with boron-incorporated stainless steel plate or stainless steel plate. This enables to provide satisfactory absorbing performance for neutrons irradiated from spent fuel assemblies contained in the inside, mechanical strength and corrosion resistance, as well as provide sufficient heat dissipating performance by the metal plates of excellent heat conductivity of the composite steel plates. (T.N.)