Evaluation of Options for Permanent Geologic Disposal of Spent Nuclear Fuel and High-Level Radioactive Waste in Support of a Comprehensive National Nuclear Fuel Cycle Strategy, Volume I and Volume II (Appendices)

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. Relevant policy questions this study can help inform include the following: Is a “one-size-fits–all” repository a good strategic option for disposal? Do
different waste types and forms perform differently enough in different disposal concepts that they warrant different treatment? Do some disposal concepts perform significantly better with or without
specific waste types or forms? The study provides this basis by evaluating 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 U.S. Department of Energy (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, as well as regulatory considerations. Criteria and metrics for the study are necessarily qualitative, because of the complexity of the problem and the difficulty of quantifying estimates of the behavior of specific waste forms in generic disposal environments. Criteria include long- term repository performance, confidence in the bases for expected performance, operational considerations, technical readiness, the production of associated secondary wastes, and topics related to safeguarding and securing the wastes. In lieu of quantitative information about specific disposal sites and design concepts, insights are developed based on the full range of information available to the group, including detailed assessments done by previous repository programs in the U.S. and elsewhere in the world.

The scope of the waste in this study includes all existing SNF from commercial, defense, and research reactors, and SNF from reasonably foreseeable operations of existing reactors (projected to 2048). The study also includes existing HLW (e.g., vitrified HLW at Savannah River and West Valley) and waste forms projected to be generated in the future from existing process waste (e.g., projected vitrified HLW from HLW at Hanford, Savannah River and the Idaho National Laboratory). In addition, the study includes consideration of both direct disposal of waste forms that are not currently planned for disposal without further treatment (e.g., calcine waste at the Idaho National Laboratory) and alternatives to planned treatments. The study acknowledges existing plans, commitments, and requirements where applicable, but the study evaluates options for disposal based primarily on technical, rather than programmatic or regulatory constraints.

Major assumptions and considerations used in this study include the following:

• HLW and SNF considered in this study are restricted to existing materials and those materials that can be reasonably expected to be generated by existing or currently planned facilities and processes.

• The inventory of HLW and SNF is intended to include all existing materials in the U.S. requiring deep geologic isolation, and is based on the best available information.

• Technologies under consideration, including both for waste treatments and disposal concepts, are limited to those that can be deployed in the near future.

• Programmatic constraints, including legal, regulatory, and contractual requirements, are acknowledged where applicable, but are not considered in the technical evaluations, consistent with the goal of the study to provide technical input to strategic decisions. For example, the identification of wastes requiring deep geologic isolation is based on consideration of overall risk, rather than on specific U.S. legal and regulatory requirements.

• Evaluations are primarily qualitative, and are based in large part on insights from past experience in waste management and disposal programs in both the U.S. and other nations.

The set of disposal concepts used in this evaluation is the same as that identified by DOE’s Used Fuel Disposition Campaign as a primary target for further research and development. These disposal concepts are presented as a useful and representative, rather than comprehensive, set of concepts.