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In order to qualify nuclear waste forms for disposal in geological repositories, waste glass producers must adequately describe the properties of the glass. One of the most important of these properties is chemical durability (resistance to leaching). An approach for characterizing the chemical durability of a producer's waste glass form must take into account that the composition of the glass will vary during production. Thus, leach testing performed as part of the characterization effort must investigate the range of glasses that are likely to be produced. Also, the approach must account for the fact that only a limited number of compositional variations can be tested and that the leach test results will be subject to uncertainty. A statistical approach that satisfies these goals is presented. The statistical approach for characterizing the chemical durability of waste glasses in a specified compositional region involves the following steps: defining the compositional region of anticipated production glass, selecting a test matrix of compositions via computer-aided experimental design techniques, leach testing, empirical modeling of the leach test results, investigating glass component effects, and using statistical confidence statements to describe chemical durability over the compositional region. These steps are illustrated using the results of work performed at Pacific Northwest Laboratory for West Valley Nuclear Services. |
