Cement-based materials for C-14 reactor waste disposal

C-14 is of particular concern in CANDU reactor waste because of its long half-life and correspondingly longer term isolation. Since both carbonate and bicarbonate exhibit high mobility in natural soil and rock media, work has been underway at Ontario Hydro to evaluate the effectiveness of cement-based materials to attenuate and contain C-14 in a reactor waste repository. Because of their highly alkaline character, cement-based materials undergo carbonation by reaction with carbon dioxide yielding stable carbonation products. It is this unique carbonation property that was investigated in the study to evaluate the effectiveness of cement-based materials as a geochemical sink for C-14. Specifically this paper deals with the attenuation and immobilization of C-14 in cement-based grout backfill and waste form, respectively