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Title: 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 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:
OSTI Identifier:
6295079
Report Number(s):
UCRL-53394
ON: DE83011054
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Technical Report
Research Org:
Lawrence Livermore National Lab., CA (USA)
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