skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Thermal and thermomechanical calculations of deep-rock nuclear waste disposal with the enhanced SANGRE code

Abstract

An attempt to model the complex thermal and mechanical phenomena occurring in the disposal of high-level nuclear wastes in rock at high power loading is described. Such processes include melting of the rock, convection of the molten material, and very high stressing of the rock mass, leading to new fracturing. Because of the phase changes and the wide temperature ranges considered, realistic models must provide for coupling of the thermal and mechanical calculations, for large deformations, and for steady-state temperature-depenent creep of the rock mass. Explicit representation of convection would be desirable, as would the ability to show fracture development and migration of fluids in cracks. Enhancements to SNAGRE consisted of: array modifications to accommodate complex variations of thermal and mechanical properties with temperature; introduction of the ability of calculate thermally induced stresses; improved management of the minimum time step and minimum temperature step to increase code efficiency; introduction of a variable heat-generation algorithm to accommodate heat decay of the nuclear materials; streamlining of the code by general editing and extensive deletion of coding used in mesh generation; and updating of the program users' manual. The enhanced LLNL version of the code was renamed LSANGRE. Phase changes were handled bymore » introducing sharp variations in the specific heat of the rock in a narrow range about the melting point. The accuracy of this procedure was tested successfully on a melting slab problem. LSANGRE replicated the results of both the analytical solution and calculations with the finite difference TRUMP code. Following enhancement and verification, a purely thermal calculation was carried to 105 years. It went beyond the extent of maximum melt and into the beginning of the cooling phase.« less

Authors:
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (USA)
OSTI Identifier:
6295079
Report Number(s):
UCRL-53394
ON: DE83011054
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; COMPUTER CODES; S CODES; GEOLOGIC DEPOSITS; THERMAL STRESSES; ROCKS; COMPUTER CALCULATIONS; HIGH-LEVEL RADIOACTIVE WASTES; MECHANICAL PROPERTIES; RADIOACTIVE WASTE DISPOSAL; TEMPERATURE EFFECTS; MANAGEMENT; MATERIALS; RADIOACTIVE MATERIALS; RADIOACTIVE WASTES; STRESSES; WASTE DISPOSAL; WASTE MANAGEMENT; WASTES; 580300* - Mineralogy, Petrology, & Rock Mechanics- (-1989); 052002 - Nuclear Fuels- Waste Disposal & Storage

Citation Formats

Heuze, F.E. Thermal and thermomechanical calculations of deep-rock nuclear waste disposal with the enhanced SANGRE code. United States: N. p., 1983. Web.
Heuze, F.E. Thermal and thermomechanical calculations of deep-rock nuclear waste disposal with the enhanced SANGRE code. United States.
Heuze, F.E. 1983. "Thermal and thermomechanical calculations of deep-rock nuclear waste disposal with the enhanced SANGRE code". United States. doi:.
@article{osti_6295079,
title = {Thermal and thermomechanical calculations of deep-rock nuclear waste disposal with the enhanced SANGRE code},
author = {Heuze, F.E.},
abstractNote = {An attempt to model the complex thermal and mechanical phenomena occurring in the disposal of high-level nuclear wastes in rock at high power loading is described. Such processes include melting of the rock, convection of the molten material, and very high stressing of the rock mass, leading to new fracturing. Because of the phase changes and the wide temperature ranges considered, realistic models must provide for coupling of the thermal and mechanical calculations, for large deformations, and for steady-state temperature-depenent creep of the rock mass. Explicit representation of convection would be desirable, as would the ability to show fracture development and migration of fluids in cracks. Enhancements to SNAGRE consisted of: array modifications to accommodate complex variations of thermal and mechanical properties with temperature; introduction of the ability of calculate thermally induced stresses; improved management of the minimum time step and minimum temperature step to increase code efficiency; introduction of a variable heat-generation algorithm to accommodate heat decay of the nuclear materials; streamlining of the code by general editing and extensive deletion of coding used in mesh generation; and updating of the program users' manual. The enhanced LLNL version of the code was renamed LSANGRE. Phase changes were handled by introducing sharp variations in the specific heat of the rock in a narrow range about the melting point. The accuracy of this procedure was tested successfully on a melting slab problem. LSANGRE replicated the results of both the analytical solution and calculations with the finite difference TRUMP code. Following enhancement and verification, a purely thermal calculation was carried to 105 years. It went beyond the extent of maximum melt and into the beginning of the cooling phase.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1983,
month = 3
}

Technical Report:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that may hold this item. Keep in mind that many technical reports are not cataloged in WorldCat.

Save / Share:
  • Deep Rock Disposal Experiment No. 1 was designed to provide information about the interaction between a molten, glass-based, nuclear waste simulant and rock material. Selected samples from this experiment were examined by optical microscopy and electron probe microanalysis. Analysis of the homogenized material in the convection cell that was created in the central portion of the melt region shows that an amount of rock equal to about one-half of the original amount of waste simulant was incorporated in the melt during the experiment. Stagnant melt at the sides of the cell formed a glass with large compositional gradients. A whitemore » band separated the convected and stagnant materials. The color of the band is attributed to light scattering by small crystallites formed during cooling. Four types of crystallites grew from the melt: two oxides, a Mg--Fe borate, and a silicate. Spinel (MgO, Cr/sub 2/O/sub 3/, FeO (Fe/sub 2/O/sub 3/), and NiO) was the most common crystallite in the glass. The spinel crystallites found within the convection cell displayed skeletal morphology and oscillatory zoning which indicates growth at varying temperatures as they were carried along by convection. A single cluster of nonskeletal (Fe,Cr)/sub 2/O/sub 3/ crystallites was found at the bottom of the melt zone where convection did not occur. Mg--Fe borate crystallites grew in clusters in the central portion of the convection cell after convection ceased. A silicate similar to Fe-rich diopside (CaMgSi/sub 2/O/sub 6/) with unusual amounts of Ce/sub 2/O/sub 3/ and other heavy metal oxides formed as larger crystallites in the stagnant melt at the side of the convection cell and as many very small crystallites in the white band.« less
  • An electrically heated test of nuclear waste simulants in granitic rock was conducted to demonstrate the feasibility of the concept of deep rock nuclear waste disposal and to obtain design data. This report describes the deep rock disposal sytstems study and the design and operation of the first concept feasibility test.
  • Purpose is to provide a preliminary geotechnical data base sufficient to initiate the development of Long-Term Risk Models for salt domes, basalt, and crystalline rock. Geology, hydrology, specific sites, and potential release pathways are considered for each type. A summary table of site suitability characteristics is presented. (DLC)
  • Thermal and mechanical scoping calculations were performed to determine the responses of two different shales to the underground disposal of nuclear waste. The geometry under consideration was a three-dimensional model for waste emplacement in a conventional room-and-pillar configuration. The first medium, high-illite shale with no expandable clays, exhibits a positive and nearly linear thermal expansion with increasing temperature. The second medium, eastern Pierre shale with abundant expandable clays, however, will dehydrate and volumetrically contract several percent upon heating to the local boiling point of the pore water. Results of the thermal calculations are presented which show that only the very-near-fieldmore » rock temperatures within the boiling isotherm are highly sensitive to the rock mass thermal conductivity and, hence, the expandable clay content. The mechanical calculations for the high-illite shale show no evidence of post-excavation instability, and no change in the stress field as a result of waste emplacement. The mechanical response of the eastern Pierre shale, however, is characterized by zones of volumetric contraction and joint opening located within the boiling isotherm and resulting directly from the dehydration shrinkage.« less
  • The TOUGH code developed at Lawrence Berkeley Laboratory (LBL) is being extensively used to numerically simulate the thermal and hydrologic environment around nuclear waste packages in the unsaturated zone for the Yucca Mountain Project. At the Lawrence Livermore National Laboratory (LLNL) we have rewritten approximately 80 percent of the TOUGH code to increase its speed and incorporate new options. The geometry of many problems requires large numbers of computational elements elements in order to realistically model detailed physical phenomena, and, as a result, large amounts of computer time are needed. In order to increase the speed of the code wemore » have incorporated fast linear equation solvers, vectorization of substantial portions of code, improved automatic time stepping, and implementation of table look-up for the steam table properties. These enhancements have increased the speed of the code for typical problems by a factor of 20 on the Cray 2 computer. In addition to the increase in computational efficiency we have added several options: vapor pressure lowering; equivalent continuum treatments of fractures; energy and material volumetric, mass and flux accounting; and Stefan-Boltzmann radiative heat transfer. 5 refs.« less