Thermal and thermomechanical calculations of deep-rock nuclear waste disposal with the enhanced SANGRE code
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.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6295079
- Report Number(s):
- UCRL-53394; ON: DE83011054
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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