Studies of the setting of engineered barrier configuration utilized in geologic disposal, 1; Dissolution life-time of vitrified waste glass

Oe, Toshiaki*; Wakasugi, Keiichiro

The report estimates the life-time of the waste glass dissolution in the geologic disposal environment. The overall safety report on the geologic disposal in Japan showed very short life-time of approximately 70,000 years under pessimistic assumptions ignoring the temperature decrease due to radioactive decay and dissolution rate reduction due to surface shrinkage. These factors are physically established phenomena and may not be excluded. The dissolution models including these factors of temperature and surface area decreases are discussed and used for re-evaluation. Three fracture models are presented for evaluating the surface area decreases; a single plate, monotonic spheres, spheres having power-law distribution. All models have the same initial volume as the waste glass block for mass conservation and the total surface areas are 10 times higher than the initial pristine block because of the fracture development during production. The results indicate the retention time of 50% of initial mass exceed 100,000 years even by different fracture models and the dissolution life-times are expected for 260,000700,000 years depending on models. These results imply more strong isolation capability of the waste glass than that estimated in the overall safety report.