SNF DISPOSAL CONCEPTS FOR SMALL AND LARGE WASTE PACKAGES

摘要

Important thermal constraints for mined geologic disposal are to limit degradation of engineered materials close to waste packages, and to limit thermal damage to host rock. Measures available to limit temperatures include: 1) selecting host rock with superior thermal properties, 2) decay storage before emplacement, 3) preclosure repository ventilation, 4) smaller waste packages, and 5) larger package and drift spacings. This study has investigated these measures and produced a set of reference disposal concepts that can be used to guide the geologic disposal R&D program, and logistical planning for waste disposal. While any of these reference concepts could deliver safe long-term waste isolation, use of the enclosed modes (popular internationally) would require small waste packages (e.g., 4-PWR size), while disposal of larger packages (12-PWR up to 32-PWR sizes) could require either salt media or emplacement in hard rock. One exception is that larger packages could be disposed of in sedimentary rock (e.g., clay or shale) with active ventilation for 200 yr or longer. These results are being addressed by ongoing R&D to investigate temperature sensitivities for natural and engineered materials, and to evaluate specific concepts for disposal of larger packages.