CASK

To provide a cask that has a structure enabling prevention of movement of a neutron shield material while ensuring a thermal expansion allowance of the neutron shield material, and an air gap for mitigating pressure increase caused by generated gas.SOLUTION: A cask 100 comprises: a bottomed cylindrical container main body 1 that stores a radioactive substance; and a lid (a secondary lid 3) that is detachably attached to an opening part of the container main body 1, in which in the lid, an outer periphery part of the container main body 1, and a bottom part of the container main body 1, neutron shield members (8 to 10) and cover members (5 to 7) covering the neutron shield member are respectively installed. In an air gap between the neutron shield material and the cover member in at least any of the lid, the outer periphery part and the bottom part, a spacer member (a pipe 11) is installed so as to position the neutron shield material on an inward side of the container main body 1.SELECTED DRAWING: Figure 1 【課題】中性子遮蔽材の熱膨張代および発生ガスによる圧力上昇緩和のための空隙を確保しつつも、中性子遮蔽材の移動を防止することができる構造のキャスクを提供すること。【解決手段】放射性物質を収納する有底筒形状の容器本体１と、容器本体１の開口部に着脱可能に取り付けられる蓋（二次蓋３）と、を備え、前記蓋、容器本体１の外周部、および容器本体１の底部に、それぞれ、中性子遮蔽材（８〜１０）および当該中性子遮蔽材を覆うカバー部材（５〜７）が設置されているキャスク１００であって、前記蓋、前記外周部、および前記底部のうちの少なくともいずれかの、中性子遮蔽材とカバー部材との間の空隙に、容器本体１の内方側に中性子遮蔽材を位置決めするためのスペーサ部材（パイプ１１）が設置される。【選択図】図１