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Title: Shale disposal of U.S. high-level radioactive waste.

Abstract

This report evaluates the feasibility of high-level radioactive waste disposal in shale within the United States. The U.S. has many possible clay/shale/argillite basins with positive attributes for permanent disposal. Similar geologic formations have been extensively studied by international programs with largely positive results, over significant ranges of the most important material characteristics including permeability, rheology, and sorptive potential. This report is enabled by the advanced work of the international community to establish functional and operational requirements for disposal of a range of waste forms in shale media. We develop scoping performance analyses, based on the applicable features, events, and processes identified by international investigators, to support a generic conclusion regarding post-closure safety. Requisite assumptions for these analyses include waste characteristics, disposal concepts, and important properties of the geologic formation. We then apply lessons learned from Sandia experience on the Waste Isolation Pilot Project and the Yucca Mountain Project to develop a disposal strategy should a shale repository be considered as an alternative disposal pathway in the U.S. Disposal of high-level radioactive waste in suitable shale formations is attractive because the material is essentially impermeable and self-sealing, conditions are chemically reducing, and sorption tends to prevent radionuclide transport. Vertically and laterallymore » extensive shale and clay formations exist in multiple locations in the contiguous 48 states. Thermal-hydrologic-mechanical calculations indicate that temperatures near emplaced waste packages can be maintained below boiling and will decay to within a few degrees of the ambient temperature within a few decades (or longer depending on the waste form). Construction effects, ventilation, and the thermal pulse will lead to clay dehydration and deformation, confined to an excavation disturbed zone within a few meters of the repository, that can be reasonably characterized. Within a few centuries after waste emplacement, overburden pressures will seal fractures, resaturate the dehydrated zones, and provide a repository setting that strongly limits radionuclide movement to diffusive transport. Coupled hydrogeochemical transport calculations indicate maximum extents of radionuclide transport on the order of tens to hundreds of meters, or less, in a million years. Under the conditions modeled, a shale repository could achieve total containment, with no releases to the environment in undisturbed scenarios. The performance analyses described here are based on the assumption that long-term standards for disposal in clay/shale would be identical in the key aspects, to those prescribed for existing repository programs such as Yucca Mountain. This generic repository evaluation for shale is the first developed in the United States. Previous repository considerations have emphasized salt formations and volcanic rock formations. Much of the experience gained from U.S. repository development, such as seal system design, coupled process simulation, and application of performance assessment methodology, is applied here to scoping analyses for a shale repository. A contemporary understanding of clay mineralogy and attendant chemical environments has allowed identification of the appropriate features, events, and processes to be incorporated into the analysis. Advanced multi-physics modeling provides key support for understanding the effects from coupled processes. The results of the assessment show that shale formations provide a technically advanced, scientifically sound disposal option for the U.S.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
992338
Report Number(s):
SAND2010-2843
TRN: US1007783
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; AMBIENT TEMPERATURE; GEOLOGIC FORMATIONS; HIGH-LEVEL RADIOACTIVE WASTES; MINERALOGY; PERFORMANCE; PERMEABILITY; POSITIONING; RADIOISOTOPES; SHALES; TRANSPORT; VOLCANIC ROCKS; WASTE FORMS; WASTES; YUCCA MOUNTAIN; Radioactive waste disposal.; Shale.; High level radioactive waste disposal.

Citation Formats

Sassani, David Carl, Stone, Charles Michael, Hansen, Francis D, Hardin, Ernest L, Dewers, Thomas A, Martinez, Mario J, Rechard, Robert Paul, Sobolik, Steven Ronald, Freeze, Geoffrey A, Cygan, Randall Timothy, Gaither, Katherine N, Holland, John Francis, and Brady, Patrick Vane. Shale disposal of U.S. high-level radioactive waste.. United States: N. p., 2010. Web. doi:10.2172/992338.
Sassani, David Carl, Stone, Charles Michael, Hansen, Francis D, Hardin, Ernest L, Dewers, Thomas A, Martinez, Mario J, Rechard, Robert Paul, Sobolik, Steven Ronald, Freeze, Geoffrey A, Cygan, Randall Timothy, Gaither, Katherine N, Holland, John Francis, & Brady, Patrick Vane. Shale disposal of U.S. high-level radioactive waste.. United States. https://doi.org/10.2172/992338
Sassani, David Carl, Stone, Charles Michael, Hansen, Francis D, Hardin, Ernest L, Dewers, Thomas A, Martinez, Mario J, Rechard, Robert Paul, Sobolik, Steven Ronald, Freeze, Geoffrey A, Cygan, Randall Timothy, Gaither, Katherine N, Holland, John Francis, and Brady, Patrick Vane. 2010. "Shale disposal of U.S. high-level radioactive waste.". United States. https://doi.org/10.2172/992338. https://www.osti.gov/servlets/purl/992338.
@article{osti_992338,
title = {Shale disposal of U.S. high-level radioactive waste.},
author = {Sassani, David Carl and Stone, Charles Michael and Hansen, Francis D and Hardin, Ernest L and Dewers, Thomas A and Martinez, Mario J and Rechard, Robert Paul and Sobolik, Steven Ronald and Freeze, Geoffrey A and Cygan, Randall Timothy and Gaither, Katherine N and Holland, John Francis and Brady, Patrick Vane},
abstractNote = {This report evaluates the feasibility of high-level radioactive waste disposal in shale within the United States. The U.S. has many possible clay/shale/argillite basins with positive attributes for permanent disposal. Similar geologic formations have been extensively studied by international programs with largely positive results, over significant ranges of the most important material characteristics including permeability, rheology, and sorptive potential. This report is enabled by the advanced work of the international community to establish functional and operational requirements for disposal of a range of waste forms in shale media. We develop scoping performance analyses, based on the applicable features, events, and processes identified by international investigators, to support a generic conclusion regarding post-closure safety. Requisite assumptions for these analyses include waste characteristics, disposal concepts, and important properties of the geologic formation. We then apply lessons learned from Sandia experience on the Waste Isolation Pilot Project and the Yucca Mountain Project to develop a disposal strategy should a shale repository be considered as an alternative disposal pathway in the U.S. Disposal of high-level radioactive waste in suitable shale formations is attractive because the material is essentially impermeable and self-sealing, conditions are chemically reducing, and sorption tends to prevent radionuclide transport. Vertically and laterally extensive shale and clay formations exist in multiple locations in the contiguous 48 states. Thermal-hydrologic-mechanical calculations indicate that temperatures near emplaced waste packages can be maintained below boiling and will decay to within a few degrees of the ambient temperature within a few decades (or longer depending on the waste form). Construction effects, ventilation, and the thermal pulse will lead to clay dehydration and deformation, confined to an excavation disturbed zone within a few meters of the repository, that can be reasonably characterized. Within a few centuries after waste emplacement, overburden pressures will seal fractures, resaturate the dehydrated zones, and provide a repository setting that strongly limits radionuclide movement to diffusive transport. Coupled hydrogeochemical transport calculations indicate maximum extents of radionuclide transport on the order of tens to hundreds of meters, or less, in a million years. Under the conditions modeled, a shale repository could achieve total containment, with no releases to the environment in undisturbed scenarios. The performance analyses described here are based on the assumption that long-term standards for disposal in clay/shale would be identical in the key aspects, to those prescribed for existing repository programs such as Yucca Mountain. This generic repository evaluation for shale is the first developed in the United States. Previous repository considerations have emphasized salt formations and volcanic rock formations. Much of the experience gained from U.S. repository development, such as seal system design, coupled process simulation, and application of performance assessment methodology, is applied here to scoping analyses for a shale repository. A contemporary understanding of clay mineralogy and attendant chemical environments has allowed identification of the appropriate features, events, and processes to be incorporated into the analysis. Advanced multi-physics modeling provides key support for understanding the effects from coupled processes. The results of the assessment show that shale formations provide a technically advanced, scientifically sound disposal option for the U.S.},
doi = {10.2172/992338},
url = {https://www.osti.gov/biblio/992338}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat May 01 00:00:00 EDT 2010},
month = {Sat May 01 00:00:00 EDT 2010}
}