Leaching fully radioactive SRP nuclear waste glass in tuff groundwater in stainless steel vessels

Abstract

SRP glass containing actual radioactive waste was leached in static tests at 90{sup 0}C in a tuffaceous groundwater (J-13 water at pH {similar_to}7.4) at a SA/V ratio of 100m{sup -1} in 316 stainless steel vessels. Tests were performed for time periods up to 134 days. Normalized mass losses were calculated for {sup 137}Cs, {sup 90}Sr, and {sup 238}Pu. The {sup 137}Cs in the leachate appeared to reach a steady value of {similar_to}3 g/m{sup 2}, corresponding to a steady-state concentration of only 1.0 ppB for total cesium. The mass losses based on {sup 90}Sr and {sup 238}Pu appearing in solution were low (<0.3 and <0.01, respectively) because of their low solubilities. However, significant amounts of these radionuclides had deposited on the steel vessel while the amount of deposited {sup 137}Cs was negligible. During the leach tests, the pH changed <0.4 unit and the only significant effect of radiolysis was reduction of NO{sub 3}{sup -} ions in solution to NO{sub 2}{sup -}. When compared to earlier tests, the results confirm that leach rates in the earlier tests with radioactive glass in Teflon vessels were high due to radiolysis of the Teflon. The results also indicate that radioactive and nonradioactive glasses of comparable composition and surface finish leach essentially identically. 12 refs., 3 figs., 4 tabs.