Immobilization of high-level nuclear reactor wastes in SYNROC: A current appraisal

摘要: Abstract A detailed investigation has been made of the comparative abilities SYNROC and borosilicate glasses to immobilize high level nuclear wastes for extremely long periods time when buried in geological repositories. Under dynamic leaching conditions (glasses tend dissolve quasicongruently whereas dissolution minerals is highly incongruent. Loss low valence cations (e.g., Ca, Ba, Cs) from near-surface regions titanate results surface films consisting dominantly titanium dioxide. Because extreme insolubility TiO2 water, these protect further hence leach rates fall off drastically with time, commonly by 2 orders-of-magnitude after 10–30 days (undersaturated) leaching. In sharp contrast, leachability a typical glass (PNL 76-68) remains constant under same conditions. incongruent mechanisms, different elements can vary factors several hundred. Thus, it impossible describe any single, characteristic value at given temperature. Detailed studies have behaviour glass, quasidynamic water 95 200°C. After relatively short (10–30 days) 95°C leachabilities cesium, calcium uranium are smaller than those 500, 2500, 100,000, respectively. Strontium barium similar rare earths trivalent actinides expected be intermediate between Ca U. Less extensive data obtained 200°C show that differences greater 95°C. Results individual consistent measurements on bulk samples. Taken together, demonstrate more resistant glass. The effects radiation damage also investigated. amount alpha particle irradiation which would received during decay radwaste safe levels causes only minor structural changes zirconolite perovskite hosts a-emitting actinide elements. Tracer behaved as closed systems U, Th, Pb daughter products despite suffering doses 10 times intense achieved contained levels. Experimental their exposure large doses. superior resistance elevated temperatures will make possible bury geologic repositories within few years reprocessing, thereby avoiding necessity prolonged storage supervision. It should about three weight HLW calcine volume now envisaged