Natural alteration of 6Li alumino-silicate glass

[摘要] Understanding the chemical durability of neutron shielding materials is necessary when assessing their long-term service potential. In this study, the chemical durability of a Li-6 enriched neutron shielding glass that has been exposed to natural, near-operational conditions is assessed by Prompt Gamma Activation Analysis (PGAA) and Neutron Depth Profiling (NDP). These non-destructive, nuclear analysis techniques are sensitive to Li-6, and PGAA is uniquely able to detect H in low quantities in solids. It was determined that the enriched alumino-silicate glass can alter within 2 months of exposure to the natural environment. This exposure resulted in an average surface alteration layer thickness of approximate to 22 mu m. The alteration layer contained approximate to 47% less Li-6 than the bulk glass. Alternatively, a 3 years exposed sample of the glass had a surface alteration depth of approximate to 30 mu m and Li-6 depletion levels in the alteration layer were between 47% and 75% less Li-6 than the bulk glass. When the alteration layer on the 3 years sample was removed, the H content of the glass's surface was nearly eliminated. This sample also showed variable Li concentrations throughout the alteration volume, which contrasts with near static Li concentration in the alteration volume of the 2 months sample. From these findings it was determined that the depletion in Li at the surface of the glass will not affect the glass's neutron shielding properties, but it may change the mechanical stability of the glass's surface and, due to increased H content in the alteration layer, make it an inappropriate material for the lining of certain neutron analysis instruments. Published by Elsevier B.V.

[发布日期] 2018-12-15