Patent Number: 
Section: claims

1. A cask cushioning body attached to both ends of a cask storing therein spent fuel and absorbing an impact applied to the cask, the cask cushioning body comprising:an end-surface side member in which a plurality of plates made of steel are formed at a distance between plate surfaces of the plates that face each other, and in which the plate surfaces of the plates are arranged along an end surface of the cask; anda circumferential-surface side member that forms a cylindrical body made of the steel, one end of which is connected to a periphery of the end-surface side member, and that is arranged along an end-portion outer-circumferential surface of the cask, whereinan impact absorber that absorbs the impact by deforming is provided outside of the end-surface side member and the circumferential-surface side member;the cask cushioning body is formed so that a size between an outer circumferential surface of a lid constituting the cask and an inner circumferential surface of the circumferential-surface side member is larger than a size between an outer circumferential surface of a main body of the cask to which the lid is fixed and the inner circumferential surface of the circumferential-surface side member. 2. The cask cushioning body according to claim 1, wherein the end-surface side member includes a plurality of end-surface reinforcing members provided to connect the plates to each other. 3. The cask cushioning body according to claim 1, wherein the end-surface side member includes at least one plate having an opening formed in a central portion thereof, andthe end-surface side member includes a plurality of central reinforcing members in a region between the plate with the opening and the other plates. 4. The cask cushioning body according to claim 3, wherein the impact absorber is inserted into a region surrounded by the central reinforcing members and the plate provided with the opening. 5. The cask cushioning body according to claim 1, whereinthe circumferential-surface side member includesa protruding portion in which peripheries of the plates in the end-surface side member protrude outward of the cylindrical body over an entire circumference of one end of the cylindrical body,a flange portion protruding outward over an entire circumference of other end of the cylindrical body, anda plurality of circumferential-surface reinforcing members connecting the protruding portion to the flange portion, and arranged on an outside surface of the cylindrical body. 6. The cask cushioning body according to claim 5, wherein the impact absorber is inserted into a region surrounded by the protruding portion, the flange portion, and the circumferential-surface reinforcing members. 7. The cask cushioning body according to claim 1, wherein a region of the end-surface side member in which the plates face each other covers a bolt for fixing the lid of the cask. 8. The cask cushioning body according to claim 7, the region of the end-surface side member in which the plates face each other covers an air-supply/exhaust, water-feed/drainage or pressure monitoring unit provided on the lid. 9. The cask cushioning body according to claim 1, wherein an impact absorbing material that absorbs the impact by deforming is filled in the end-surface side member between regions in which the plates face each other. 10. The cask cushioning body according to claim 1, whereinthe impact absorber is formed by a combination of a plurality of wood blocks, andthe impact absorber includesa first impact absorber group that is provided along a circumference of other end of the circumferential-surface side member, and that is made of a first material that absorbs the impact in a direction parallel to the end surface of the cask,a second impact absorber group that is provided around one end of the circumferential-surface side member, along the outer circumference of the end-surface side member, and adjacent to the first impact absorber group, and that is made of a second material that is lower in a compression strength than the first material and that absorbs the impact in the direction parallel to the end surface of the cask,a third impact absorber group that is provided in an external corner of the impact absorber along the outer circumference of the end-surface side member and adjacent to the second impact absorber group, and that is made of a third material that is lower in the compression strength than the second material and that absorbs the impact in a direction orthogonal to or inclined with respect to the end surface of the cask,a fourth impact absorber group that is provided along inner circumferences of the second and third impact absorber groups and adjacent to the second and third impact absorber groups, and that is made of the third material that absorbs the impact in the direction orthogonal to the end surface of the cask, anda fifth impact absorber group that is provided inside of a circumference of the fourth impact absorber group, and that is made of the third material that absorbs the impact in the direction parallel to the end surface of the cask. 11. The cask cushioning body according to claim 1, whereina mounting hole into which a bolt for fixing the cushioning body to the cask is inserted is provided in the impact absorber, andthe mounting hole is expandable and contractable in a depth direction of the mounting hole.