Volume reduction and plutonium recovery: their place in alpha waste management

Solid combustible plutonium contaminated materials are largely produced by mixed oxide PuO2/UO2 fuel preparation and fuel element fabrication. The following processes to reduce the volume of the waste by combustion of all organic compounds but also to provide the means of extracting high percentage of the plutonium were studied: low temperature two stage incineration and Pu-recovery from ashes; incineration in molten salt; acid digestion; and cryogenic crushing and leaching. These processes will be able to reduce the volume of the waste by up to 95% and extract up to 98% of the plutonium contaminant. Their application promises to: a) minimise the waste which needs to be kept in engineered storage and ultimately reduce the required repository capacity and hence the cost of disposal dramatically; b) avoid the risk of storing wastes that are inflammable and release gases from radiolysis and natural decomposition/fermentation; c) produce residues, which can readily be fixed in a ceramic or vitrous matrix, but for which cement, bitumen or polymer resins may well suffice; and d) reduce the long term risk of disposal by recovering most of the Pu-fuel for recycling