A spent nuclear fuel storage bridge comprising either a stationary or mobile structure supported from the walls of a spent nuclear fuel storage pool. The structure may have either a pivotally mounted or non-pivotally mounted lower basket or cage portion which occupies a region of the vertical space between the pool water surface and the existing pool floor supported fuel storage racks. Using the bridge, at least a ten-foot deep barrier of biological shield water and at least a two-foot space between the top of the existing racks and the bottom of the bridge can be maintained in a storage pool of typical geometrics and dimensions. By limiting the height of the basket portion of the bridge, up to a three-foot space beneath the biological shield water may be provided to accommodate underwater horizontal transference of spent fuel storage canisters to and from the bridge. The width of the basket portion is determined by the spent fuel length and the resulting storage canister length. Horizontally positioned fuel canisters are stacked vertically within a frame structure or thermal spacer assembly carried internally of the bridge for providing longitudinal and lateral support of the canisters and permitting cooling of the canisters. Also provided are novel fuel storage canister constructions and handling apparatus therefor.