Leach Testing of Idaho Chemical Processing Plant Final Waste Forms

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Abstract
A number of pellets and highly durable glasses, prepared from nonradioactive simulated high-level waste calcines, have been leach tested. The leach tests were patterned on the International Atomic Energy Agency standard test and the proposed Materials Characterization Center tests. Most tests were made with static distilled water at 25, 70, 95, 250, and 350°C and in refluxing distilled water at 95°C. Leach rates were determined by analyzing the leachate by instrumental activation analysis or spectrochemical analysis and from weight loss. The leach tests were run on solid pieces of glass (cast and core-drilled cylinders and broken pieces) and on coarse ground glass. Solid pieces gave higher leach rates than ground glass. Cesium, molybdenum, sodium, and weight loss leach rates of solid pieces of glass in distilled water were comparable and varied from -7 g/cm2 day at 25°C to ∼10−1 g/cm2 day at 250°C. The leach rates in static distilled water at 95°C were lower than those in refluxing distilled water at the same temperature. Even at 25°C, sodium, cesium, and molybdenum readily leached from the porous pellets, but the pellets showed no visible attack, even at 250°C.

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