Storage system for radioactive nuclear waste with pressure surge protection

An unventilated wet cask for storing nuclear waste fuel comprising:

• a longitudinal axis;
• a cask body comprising a removable lid assembly at a top end, a base at a bottom end, and a circumferential wall extending along the longitudinal axis between the lid assembly and the base, the cask body forming a hermetically sealed internal cavity configured for holding spent nuclear fuel submerged in an inventory of water inside the internal cavity;
• the wall comprising an inner shell, an outer shell, and an intermediate shell;
• an inner annular space defined between the inner shell and intermediate shell;
• an outer annular space defined between the intermediate shell and outer shell, radially spaced between the inner and outer shells;
• a plurality of circumferentially spaced apart inner radial ribs extending between the inner shell and the intermediate shell in the inner annular space;
• a plurality of circumferentially spaced apart outer radial ribs extending between the intermediate shell and the outer shell in the outer annular space;
• wherein the inner shell, outer shell, intermediate shell, inner radial ribs, and outer radial ribs are formed of thermally conductive materials which are coupled together to collectively define a thermal heat removal path operable to draw heat emitted by the spent nuclear fuel outwards to the outer shell which is exposed to an ambient environment which defines a heat sink.