Dissolution of Borosilicate Glass in the Presence of Basalt and Groundwater at 300 Bars and 100 exp 0 to 300 exp 0 C

摘要

Borosilicate glass, PNL 76-78, a simulated waste form for nuclear waste disposal, was reacted together with a Columbia River tholeiitic basalt and synthetic groundwater in modified Dickson-type rocking autoclaves. These experiments were performed to determine the suitability of disposing borosilicate glass in a nuclear waste repository located in basalt. Solutions were sampled periodically over durations of one month at 300 exp 0 C, three months at 200 exp 0 C, and seven months at 100 exp 0 C. Water:solid mass ratio was 10:1. From the observations on the solutions and solid phases it appeared that significant dissolution, reaction, and precipitation occurred at 200 exp 0 and 300 exp 0 C, but that only dissolution occurred at 100 exp 0 C. The lack of precipitation of daughter phases or reaction of solution with the basalt at 100 exp 0 C caused all elements released from the borosilicate glass to remain in solution. This is interpreted to be caused by kinetic limitations on the nucleation of daughter phases. The average dissolution rate at 100 exp 0 C was roughly 0.5 g glass per liter groundwater per square meter of glass surface per month. (ERA citation 09:019785)