Patent Number: 
Section: abstract

A cask includes a cask body, an outer cylinder, a plurality of fins, and a plurality of neutron shields. The cask body has a tubular shape around a central axis and is capable of housing fuel assemblies. The outer cylinder has a tubular shape surrounding the cask body. The fins are aligned in a circumferential direction in a tubular space formed between the cask body and the outer cylinder, and connect an outer peripheral surface of the cask body and an inner peripheral surface of the outer cylinder to divide the tubular space into a plurality of divided spaces. The neutron shields contain a neutron shielding material with which the divided spaces are filled. Each neutron shield includes a void portion extending in the axial direction along the central axis. Accordingly, it is possible to reduce stress that may be exerted on the outer cylinder or other components by thermal expansion of the neutron shielding material when the fuel assemblies are housed in the cask.