Spent fuel cask

In a spent fuel cask, buffer members having an earthquake proof performance are disposed at the lower surface of a support structural members. In addition, buffer members having an earthquake proof performance are disposed between a basket support and a cask main body. Further, a spring support mechanism is disposed in the inside of the basket. Alternatively, a damper having viscous resistance is disposed. Since the acceleration exerted on spent fuels in the main body of the spent fuel cask and spent fuels in the cask is reduced during earthquakes or during transportation, the collision of the spent fuels and the basket is prevented, or even if they should collide, the colliding force is moderated. Upon occurrence of earthquakes or during transportation of spent fuel cask and operation of a crane for the spent fuel cask, the collision of the spent fuels contained in the spent fuel cask and the basket can be prevented, or the colliding force by the collision can be moderated, to improve the integrity. (N.H.)