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Temperature distributions from the Single Heater Test of the Yucca Mountain Project were used to determine rock-mass thermal conductivity. The Single Heater Test, located in a densely welded tuff in Alcove 5 of the Exploratory Studies Facility at Yucca Mountain, is nominally 13-m wide, 10-m deep and 5.5-m high. A centrally located, 5-m long, 4 kW electrical heater was activated for 9 months. During the heating phase and subsequent cooling phase of a similar duration, temperatures were measured hourly from more than 300 thermocouples emplaced in boreholes strategically drilled into the test block. An inverse method, that assumes a linearized system, was applied. This method minimized the sum of residuals between temperature measurements and simulations. The simulations were based on temporal and spatial superposition of a series of point sources that represented a linear heat source akin to the line-source heater in the Single Heater Test. Also the method accounted for fluctuations in the power of the central heater through the use of convolution methods. Subsequently, the derived value for rock-mass thermal conductivity was compared to values determined from several laboratory and field techniques that accounted for both matrix and lithophysal porosity. In general, agreement between the various methods was good.

Numerical calculations of disposal room configurations at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM are presented. Specifically, the behavior of either crushed salt or a crushed salt-bentonite mixture, when used as a backfill material in disposal rooms, is modeled in conjunction with the creep behavior of the surrounding intact salt. The backfill consolidation model developed at Sandia National Laboratories was implemented into the SPECTROM-32 finite element program. This model includes nonlinear elastic as well as deviatoric and volumetric creep components. Parameters for the models were determined from laboratory tests with deviatoric and hydrostatic loadings. The performance of the intact salt creep model previously implemented into SPECTROM-32 is well documented.Results from the SPECTROM-32 analyses were compared to a similar study conducted by Sandia National Laboratories using the SANCHO finite element program. The calculated deformations and stresses from the SPECTROM-32 and SANCHO analyses agree reasonably well despite differences in constitutive models and modeling methodology. These results provide estimates of the backfill consolidation through time. The trends in the backfill consolidation can then be used to estimate the permeability of the backfill and subsequent radionuclide transport.