Laboratory testing of glasses for Lockheed Idaho Technology Co. - fiscal year 1994 report

The purpose of this project is to measure the intermediate and long-term durability of vitrified waste forms developed by Lockheed Idaho Technology Co. (LITCO) for the immobilization of calcined radioactive wastes at Idaho National Engineering Laboratory. Two vitreous materials referred to as Formula 127 and Formula 532, have been subjected to accelerated durability tests to measure their long-term performance. Formula 127 consists of a glass matrix containing 5-10 vol % fluorite (CaF{sub 2}) as a primary crystalline phase. It shows low releases of glass components to solution in 7-, 28-, 70-, and 140-day Product Consistency Tests performed at 2000 m{sup -1} at 90{degrees}C. In these tests, release rates for glass-forming components were similar to those found for durable waste glasses. The Ca and F released by the glass as it corrodes appear to reprecipitate as fluorite. Formula 532 consists of a glass matrix containing 5-10 vol % of an Al-Si-rich primary crystalline phase. The release rates for components other than aluminum are relatively low, but aluminum is released at a much higher rate than is typical for durable waste glasses. Secondary crystalline phases form relatively early during the corrosion of Formula 532 and appear to consist almost entirely of the Al-Si-rich primary phase (or a crystal with the same Al:Si ratio) and a sodium-bearing zeolite. Future test results are expected to highlight the relative importance of primary and secondary crystalline phases to the rate of corrosion of Formula 127 and Formula 532