NEW DESIGN OF A SPENT NUCLEAR FUEL SHIPPING CASK USING A DEPLETED URANIUM SHIELDING

ln anticipation of future demand for shipment of higher bumup spent nuclear fuel (SF), a higher performance shipping cask (JSU-1), with a depleted uranium (DU) gamma shield, has been designed. The cask can transport 12 PWR SF assemblies with a bumup of 45 000 MW·dft U or 32 BWR SF assemblies with a burnup of 40 000 MW ·dft U under dry conditions, its total weight, including SF, being about 100 t. Various investigations, including trial manufacture of a DU casting and confirmation of its properties, the influence of assembly accuracy and the internal defects of the DU on shielding performance, dynamic compression tests of balsa blocks, used as shock absorbers, and the economic evaluation of shipment using the JSU-1 cask were made. It was confinned that use of a DU shield in a JSU-1 cask would permit transport of a greater number of higher burnup SF assemblies safely and economically compared with existing types of casks.