Method for storing high level radioactive waste. In one embodiment, the invention comprises: (a) providing a body portion comprising a floor, an open top end, an inner shell forming a cavity having, an outer shell surrounding the inner shell so as to form a space therebetween, and at least one opening in the inner shell that forms a passageway from the space into a bottom of the cavity; (b) placing a canister containing high level radioactive waste into the cavity; and (c) positioning a lid having at least one outlet vent atop the inner and outer shells so as to enclose the open top end of the body portion and the at least one outlet vent forming a passageway from a top of the cavity to the ambient atmosphere; and wherein at least one inlet vent forms a passageway from an ambient atmosphere to the space.