In the near future the Defense Waste Processing Facility (DWPF) at the Savannah River Site (SRS) will begin stabilizing high-level radioactive waste using borosilicate glass. The molten waste glass will be poured into stainless steel canisters which, after cooling, will be sealed shut to produce the canistered waste forms. Following interim storage at SRS, the glass-filled canisters will be shipped to an appropriate geologic repository for final disposal. As a result of radioactive decay in the waste, the glasses will absorb large doses of alpha, beta, gamma, neutron, and alpha recoil radiation which raises issues regarding the stability of the canistered waste forms. Thermal analysis testing revealed slight weight changes, which were a function of gamma irradiation, in a highly reduced DWPF simulated waste glass. Transmission electron microscopy (TEM) was performed on these glasses to see if the weight change corresponded to microstructural variations. TEM analyses showed that no microstructural changes were attributable to gamma irradiation. Exposure of the samples to the electron beam in the TEM did result in some changes in the glass microstructures in some cases. These changes were likely due to localized heating of the glass due to interactions with the transmitted electrons.
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