Generic Repository Concepts and Thermal Analysis for Advanced Fuel Cycles
- Sandia National Laboratories (SNL)
- Lawrence Livermore National Laboratory (LLNL)
- Savannah River National Laboratory (SRNL)
- ORNL
The current posture of the used nuclear fuel management program in the U.S. following termination of the Yucca Mountain Project, is to pursue research and development (R&D) of generic (i.e., non-site specific) technologies for storage, transportation and disposal. Disposal R&D is directed toward understanding and demonstrating the performance of reference geologic disposal concepts selected to represent the current state-of-the-art in geologic disposal. One of the principal constraints on waste packaging and emplacement in a geologic repository is management of the waste-generated heat. This paper describes the selection of reference disposal concepts, and thermal management strategies for waste from advanced fuel cycles. A geologic disposal concept for spent nuclear fuel (SNF) or high-level waste (HLW) consists of three components: waste inventory, geologic setting, and concept of operations. A set of reference geologic disposal concepts has been developed by the U.S. Department of Energy (DOE) Used Fuel Disposition Campaign, for crystalline rock, clay/shale, bedded salt, and deep borehole (crystalline basement) geologic settings. We performed thermal analysis of these concepts using waste inventory cases representing a range of advanced fuel cycles. Concepts of operation consisting of emplacement mode, repository layout, and engineered barrier descriptions, were selected based on international progress and previous experience in the U.S. repository program. All of the disposal concepts selected for this study use enclosed emplacement modes, whereby waste packages are in direct contact with encapsulating engineered or natural materials. The encapsulating materials (typically clay-based or rock salt) have low intrinsic permeability and plastic rheology that closes voids so that low permeability is maintained. Uniformly low permeability also contributes to chemically reducing conditions common in soft clay, shale, and salt formations. Enclosed modes are associated with temperature constraints that limit changes to the encapsulating materials, and they generally have less capacity to dissipate heat from the waste package and its immediate surroundings than open modes such as that proposed for a repository at Yucca Mountain, Nevada. Open emplacement modes can be ventilated for many years prior to permanent closure of the repository, limiting peak temperatures both before and after closure, and combining storage and disposal functions in the same facility. Open emplacement modes may be practically limited to unsaturated host formations, unless emplacement tunnels are effectively sealed everywhere prior to repository closure. Thermal analysis of disposal concepts and waste inventory cases has identified important relationships between waste package size and capacity, and the duration of surface decay storage needed to meet temperature constraints. For example, the choice of salt as the host medium expedites the schedule for geologic disposal by approximately 50 yr (other factors held constant) thereby reducing future reliance on surface decay storage. Rock salt has greater thermal conductivity and stability at higher temperatures than other media considered. Alternatively, the choice of salt permits the use of significantly larger waste packages for SNF. The following sections describe the selection of reference waste inventories, geologic settings, and concepts of operation, and summarize the results from the thermal analysis.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1042872
- Resource Relation:
- Conference: Waste Management Symposia Conference, Phoenix, AZ, USA, 20120226, 20120301
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
BOREHOLES
CAPACITY
CLOSURES
DECAY
FUEL CYCLE
IGNEOUS ROCKS
METAMORPHIC ROCKS
NUCLEAR FUELS
PERMEABILITY
PLASTICS
POSITIONING
RHEOLOGY
SALT DEPOSITS
STORAGE
THERMAL ANALYSIS
THERMAL CONDUCTIVITY
WASTE MANAGEMENT
WASTES
YUCCA MOUNTAIN