This study provides a technical basis for informing policy decisions regarding strategies for the management and permanent disposal of spent nuclear fuel (SNF) and high-level radioactive waste (HLW) in the United States requiring geologic isolation. The study evaluates potential impacts of waste forms on the feasibility and performance of representative generic concepts for geologic disposal. Participants in the study include representatives from the DOE, the U.S. Navy, several national laboratories, universities and private sector firms with expertise in a broad range of fields, including nuclear engineering, earth sciences, materials science, chemical engineering, and materials safeguards and security, and regulatory considerations. The inventory of HLW and SNF is intended to include all existing materials in the U.S. requiring deep geologic isolation, based on the best available information. Four representative disposal concepts are addressed: mined repositories in three geologic media—salt, clay/shale rocks, and crystalline (e.g., granitic) rocks—and deep borehole disposal in crystalline rocks. Waste groups are evaluated against six primary criteria for potential disposal in each of the four disposal concepts.
Selected study conclusions include: 1) deep borehole disposal option is a good option for small waste forms and provides flexibility for disposal; 2) disposal options that utilize multiple repositories are technically viable; 3) all waste forms could be accommodated in multiple disposal concepts, although with varying degrees of confidence; 4) some disposal concepts may require segregating some waste forms from each other within a single repository; 5) salt allows for more flexibility in managing high-heat waste; 6) direct disposal of commercial SNF in existing dual-purpose canisters is potentially feasible; and 7) implementation and demonstration of robust performance may be simpler for some disposal concepts than for others. All of the disposal concepts evaluated in this study have the potential to provide robust long-term isolation for specific wastes; some options may provide greater flexibility or fewer challenges than others. Additional generic and site-specific R&D is needed before any disposal options can be implemented.