Year
1995
Abstract
The high content of Na2O in Hanford Site low-level tank wastes, averaging about 80 wt% on an oxide basis, necessitates the development of durable high-sodium glasses. Pacific Northwest Laboratory (PNL) is providing glass formulation support for this program. Glass development entails testing many glasses in a short time; it is not practical to perform long-term durability tests on every glass. The current approach on chemical durability focuses on a suite of short-term laboratory tests such as dynamic single-pass flow-through (SPFT) tests, static product consistency tests (PCI), and vapor hydration tests. The preliminary results from the three types of tests are quite different, but each provides insight into the glass corrosion process. The PCT data showed that at the same alumina, silica, and sodium levels the glass durability order for different glass systems is: Boron-only > Mixture > Calcium-only, while the opposite order is observed in SPFT tests. The order for vapor hydration tests is: Boron-only > Mixture = Calcium-only. Understanding of the glass durability order requires knowledge of the glass corrosion mechanism under specific test conditions. Integration of the three types of tests used in this program provides a more nearly complete picture of glass corrosion progress and the needed confidence for a glass optimization program. The 7-day PCT tests may provide one of the best means for preliminary screening of glass compositions within short development time. The results are relevant to long-term (or final stage corrosion) durability, as assessed by vapor hydration tests.