Bentonite in nuclear waste disposal: A review of research in support of the Basalt Waste Isolation Project

摘要: Abstract The Basalt Waste Isolation Project is investigating the feasibility and safety of a high-level nuclear waste repository in Columbia River basalts. A mixture crushed basalt sodium bentonite under investigation as packing material around individual containers. 75:25 basalt/bentonite mixture, with density 2.1 g/cm3, BWIP reference material. hydraulic conductivity highly compacted ranges from 4 to 7·10−13 cm/s, while that 1–4·10−10 cm/s. diffusion coefficient for water mixtures approximately 2·10−5 cm2/s at 90°C. swelling pressure conditions expected be less than 2.5 MPa. thermal range 0.3–1.6 W/mK. Bentonite subjected dry heating nearly year undergoes only reversible dehydration temperatures 370°C. Under hydrothermal montmorillonite minor ion exchange 200°C, but significant dissolution reprecipitation 300°C. Basalt/bentonite undergo small-scale mesostasis 150°C. At 300°C higher, in-situ alteration partial illitization occur. Water vapor greater 200°C irreversibly degrades ability bentonite. Sodium shows no evidence damage high gamma doses. Extremely doses alpha radiation can lead structural clay. Initial corrosion rates steel copper contact saturated are several tens micrometers per year. Such sensitive local temperature, moisture, redox conditions, formation magnetite clay-rich surface coatings. strongly sorbs Sr, Cs Am solution, efficient sorber U Np. Sorption by dependent on state, large sorption capacities reported U, Np Tc reducing conditions. Desorption Np, Se much initial sorption. radionuclides colloidal may have effect package performance.