The Generic Deep Geologic Disposal Safety Case presents generic information that is of use in understanding potential deep geologic disposal options (e.g., salt, shale, granite, deep borehole) in the U.S. for used nuclear fuel (UNF) from reactors and high-level radioactive waste (HLW).
This report describes RD&D activities to support a safety case for disposal of heat generating radioactive waste (used nuclear fuel, high-level nuclear waste) in a generic bedded salt repository based on interactions from March, 2013 Workshop.
Used nuclear fuel (UNF) must maintain its integrity during the storage period in such a way that it can withstand the physical forces of handling and transportation associated with restaging the fuel and transporting it to treatment or recycling facilities, or to a geologic repository.
Clay and granitic geologic rock units are potential host media for future repositories for used nuclear fuel and high level waste. This report addresses the representation of flow in these two media within numerical process (discrete fracture network) models.
The Office of Nuclear Energy has conducted a technical review and assessment of the total current inventory [~70,150 MTHM as of 2011] of domestic discharged used nuclear fuel (UNF) and estimated an amount to be considered for retention in support of research, development, demonstration, and national security interests.
A disposal concept consists of three parts: waste inventory (7 waste types examined), geologic setting (e.g., clay/shale, salt, crystalline, other sedimentary), and the engineering concept of operations (range of generic operational concepts examined; enclosed and open mode disposal concepts, thermal analysis, other).
The Used Fuel Disposition Campaign (UFDC) conducts R&D activities related to storage, transportation and disposal of used nuclear fuel and high level nuclear waste (for existing and future fuels); deep geologic disposal R&D activities are outlined and prioritized on the basis of gaps in understanding and benefit derived from R&D to narrow such gaps.
The Used Fuel Disposition Campaign will identify alternatives and conduct scientific research and technology development to enable storage, transportation, and disposal of used nuclear fuel and wastes generated by existing and future nuclear fuel cycles.
The Transportation Team identified the retrievability and subcriticality safety functions to be of primary importance to the transportation of UNF after extended storage and to transportation of high burnup fuel. The tasks performed and described herein address issues related to retrievability and subcriticality; integrity of cladding (embrittled, high burnup cladding, loads applied to cladding during transport), criticality analyses of failed UNF within transport packages, moderator exclusion concepts, stabilization of cladding with canisters for criticality control; and the need for maintaining a detailed inventory of UNF in dry storage as an ongoing activity.
Several international organizations have made significant progress in the characterization and performance evaluation of other disposal design options and host rock characteristics (clay/shale, granite), most of which were very different from those studied in the U.S. The DOE recognizes that close international collaboration is a beneficial and costeffective strategy for advancing disposal science. This report describes the active collaboration opportunities available to U.S. researchers, and presents specific cooperative research activities that have been recently initiated within DOE’s disposal research program.
The document describes the initial work on designing and developing requirements for a total system performance assessment (TSPA) model that can support preliminary safety assessments for a mined geologic repository for high-level waste (HLW) and spent nuclear fuel (SNF) in salt host rock at a generic site. A preliminary generic salt TSPA model for HLW/SNF disposal has been developed and tested for an isothermal repository in salt, for emplaced waste that is assumed to have no decay heat; for salt repositories containing heat-generating HLW/SNF, the present study develops model requirements based on features, events, and processes (FEPs) screening and proposed sensitivity analyses for heat-generating waste. These may better guide the construction of a more representative salt TSPA model.
The study summarizes the initial work on numerical modeling, simulations, and experimental results related to nuclear waste storage in a salt repository. The study reflects the project's preliminary effort at simulating the fluid flow and heat transport processes, before treating the fully coupled thermal-mechanical-hydrologic-chemical (TMHC) coupled processes in the future.
The natural barrier system (NBS) is an integral part of a geologic nuclear waste repository. The report describes progress in development of an integrated modeling framework that can be used for systematically analyzing the performance of a natural barrier system and identifying key factors that control the performance. This framework is designed as an integrated tool for prioritization and programmatic decisions.
This report summarizes research activities on engineered barrier system (EBS) model integration with the generic disposal system model (GDSM), and used fuel degradation and radionuclide mobilization (RM) in support of the EBS evaluation and tool development within the UFD campaign.
This roadmap is intended to advance deep borehole disposal (DBD) from its current conceptual status to potential future deployment as a disposal system for spent nuclear fuel (SNF) and high-level waste (HLW). The objectives of the DBD RD&D roadmap include providing the technical basis for fielding a DBD demonstration project, defining the scientific research activities associated with site characterization and postclosure safety, and defining the engineering demonstration activities associated with deep borehole drilling, completion, and surrogate waste canister emplacement.
Clay/shale has been considered as potential host rock for geological disposal of high-level radioactive waste throughout the world. Coupled thermal, hydrological, mechanical, and chemical (THMC) processes have a significant impact on the long-term safety of a clay repository. This report documents results from three R&D activities: (1) implementation and validation of constitutive relationships, (2) development of a discrete fracture network (DFN) model for investigating coupled processes in the excavation damaged zone, and (3) development of a THM model for the Full-Scale Emplacement Experiment tests at Mont Terri, Switzerland, for the purpose of model validation. One major goal is to provide a better understanding of the evolution of the excavation damage zone in clay repositories.
While both wet and dry storage have been shown to be safe options for storing UNF, the focus of the program is on dry storage of commercial UNF at reactor or centralized locations. This report focuses on the knowledge gaps concerning extended storage identified in numerous domestic and international investigations and provides the UFDC’s gap description, any alternate gap descriptions, the rankings by the various organizations, evaluation of the priority assignment, and UFDC-recommended action based on the comparison.
Development and implementation of future advanced fuel cycles including those that recycle fuel materials, use advanced fuels different from current fuels, or partition and transmute actinide radionuclides, will impact the waste management system. The UFD Campaign can reasonably conclude that advanced fuel cycles, in combination with partitioning and transmutation, which remove actinides, will not materially alter the performance, the spread in dose results around the mean, the modeling effort to include significant features, events, and processes (FEPs) in the performance assessment, or the characterization of uncertainty associated with a geologic disposal system in the regulatory environment of the US.
The United States (U.S.) currently utilizes a once-through fuel cycle where used nuclear fuel is stored onsite in either wet pools or in dry storage systems with ultimate disposal envisioned in a deep mined geologic repository. This report provides an estimate of potential waste inventory and waste form characteristics for the DOE UNF and HLW and a variety of commercial fuel cycle alternatives in order to support subsequent system-level evaluations of disposal system performance.
The report is intended to help assess and establish the technical basis for extended long‐term storage and transportation of used nuclear fuel. It provides: 1) an overview of the ISFSI license renewal process based on 10 CFR 72 and the guidance provided in NUREG‐1927; 2) definitions and terms for structures and components in DCSSs, materials, environments, aging effects, and aging mechanisms; 3) TLAAs and AMPs, respectively, that have been developed for managing aging effects on the SSCs important to safety in the dry cask storage system designs; and 4) AMPs and TLAAs for the SSCs that ar
The report presents information related to the development of a fundamental understanding of disposal-system performance in a range of environments for potential wastes that could arise from future nuclear fuel cycle alternatives. It addresses selected aspects of the development of computational modeling capability for the performance of storage and disposal options. Topics include radionuclide interaction with geomedia, colloid-facilitated radionuclide transport (Pu colloids), interaction between iodide (accumulate in the interlayer regions of clay minerals) and a suite of clay minerals
The assessment of generic EBS concepts and design optimization to harbor various disposal configurations and waste types needs advanced approaches and methods to analyze barrier performance. The report addresses: 1) Overview of the importance of THMC processes to barrier performance, and international collaborations; 2) THMC processes in clay barriers; 3) experimental studies of clay stability and clay-metal interactions at high temperatures and pressures; 4) thermodynamic modeling and database development; 5) Molecular Dynamics (MD) study of clay hydration at ambient and elevated temperatures; and 6) coupled thermal-mechanical (TM) and thermo-hydrological (TH) modeling in salt.