Evaluation of Glass as a Matrix for Solidification of Savannah River Plant Waste. Nonradioactive and Tracer Studies.

摘要

One option for long-term management of Savannah River Plant high-activity waste is solidification and storage in a retrievable surface storage facility to be located on the plantsite. This study demonstrated that SRP waste can be incorporated into a borosilicate glass at 1150exp 0 C. Tests with simulated waste indicate that alkaline sludge stored in SRP waste tanks can be solidified in borosilicate glass containing up to 45wt. percent sludge. For melting at 1150exp 0 C,the optimum glass mixture is 52.5wt. percent SiO sub 2 , 10.0percent B sub 2 O sub 3 , 22.5percent Na sub 2 O, 5.0percent CaO,and 10.0percent TiO sub 2 . Aluminum increases glass melt viscosity and can limit the amount of sludge solidified. Sulfate has limited solubility;above 0.8to 1.0wt. percent sulfate, a separate,water-soluble,cesium-rich phase is formed. During melting,approximately 0.5percent of the cesium, 10to 50percent of the ruthenium,and all of the mercury present in the glass mixture are volatilized. At 25exp 0 C,initial leachabilities for both exp 137Cs and exp 85Sr are approximately 10exp -6 g/(cm exp 2 -day) and both decrease to approximately 10exp -8 g/(cm exp 2 -day) after 40days. Gamma irradiation to 10exp 10rads and alpha decay in the glass matrix do not significantly affect the glass waste forms. Devitrification of waste glasses occurs near 600exp 0 C,but leachability is increased by only a factor of approximately 3.