Alpha radiation damage on sintered waste glasses

The investigation project consists of two main tasks: calculation of alpha decay in waste glasses, principal features, and experimental work simulating alpha decay damage in glasses used for immobilization of radioactive wastes. We calculated, by means of the computer code ORIGIN2.1 the actinides activities caused by the high level wastes (HLW) from reprocessed pressurized heavy water reactor spent fuel, with a burn-up of 7,000 MWd/t U and a cooling time of 20 years. Based on those results, are calculated and graphically presented the mean alpha energy and the cumulative alpha events and ionization dose, per metric ton of heavy metal and per cubic centimeter of the sintered HLW glass from, as a function of the time up to 2 X 107 years. About the experimental work, that is, the irradiation of sintered samples of aluminoborosilicate glass by the utilization of B10(n, alpha)Li7 reaction, in order to simulate the alpha decay effects on the glass, we have subjected the borosilicate glass to thermal neutron irradiation in a reactor, with an accumulated fluence equivalent ro approximately 103, 104, 105 and 106 years of waste disposal. We considered the following potential effects of accumulated alpha decay: changes in the density; changes in the dissolution rates; changes in the microstructure of the sintered glass. We observed minor changes in the corrosion rates and in the microstructure. The magnitude of the density change was less than 1.0% up to the radiation exposure of 4 X 1018 reactions / cm3 and 0.6% for 3.8 X 1019 reactions / cm3. The last corresponds to the cumulative irradiation during three million years after disposal of the waste glass from the spent fuel irradiated up to 7000 MWd/t U. (author)