a canister apparatus , basket apparatus and combinations thereof for transporting and / or storing high level radioactive waste , such as spent nuclear fuel . the canister apparatus comprises a cavity for receiving the spent nuclear fuel that is surrounded by two independent gas - tight containment boundaries . the structures that form the two independent gas - tight containment boundaries are in substantially continuous surface contact with one another , thereby facilitating sufficient heat removal from the cavity . in another aspect , the invention is a basket apparatus having a plurality of disk - like grates arranged in a stacked and spaced arrangement so that the cells of the disk - like grates are aligned . in still another aspect , the invention can be a basket apparatus having a disk - like grate having a ring - like structure encompassing a gridwork of beams specially arranged to achieve a unique cell configuration .