GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 175-4
Presentation Time: 9:05 AM


STAUFFER, Philip H.1, KUHLMAN, Kristopher L.2, BOUKHALFA, Hakim3, GUILTINAN, Eric J.1, BOURRET, Michelle4, DOZIER, Brian3, MILLER, Terry1, OTTO, Shawn5, RUTQVIST, Jonny6 and WEAVER, Douglas5, (1)EES-16, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Mailstop T003, Los Alamos, NM 87545, (2)Applied Systems Analysis & Research Dept. 6224, Sandia National Laboratories, PO Box 5800, Mail Stop 0747, Albuquerque, NM 87185, (3)Los Alamos National Laboratory, Los Alamos, NM 87545, (4)EES-16, Earth & Environmental Sciences Division, Los Alamos National Laboratory, Mailstop T003, Los Alamos, NM 87545, (5)REPOSITORY SCIENCE & OPERATIONS PROGRAM, Los Alamos National Laboratory, Carlsbad, NM 88220, (6)Energy Geosciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720

Disposition of civilian spent nuclear fuel (SNF) resulting from energy production creates heat generating waste. Numerous concepts for the management of heat generating waste have been proposed and examined internationally, including geologic disposal in salt because of its low permeability and visco-plastic deformation that causes self-repair of damage. Evaluating the safety and technical challenges of storing thermally hot waste in a salt repository is an ongoing process involving experiments and supporting numerical simulations. An experiment is underway in the underground of the Waste Isolation Pilot Plant (WIPP in Carlsbad, New Mexico, USA), to address how complex hydrogeological phenomena such as brine migration, vapor transport, and mechanical changes to the salt might be effected by the presence of a heat generating source in bedded salt.

We report results from a shakedown test in a sub-horizontal borehole in the underground at WIPP that includes a 10.2 cm diameter borehole equipped with a heater surrounded with smaller diameter boreholes instrumented with thermocouples. The central borehole contains an inflatable packer, heater, and constantly flowing nitrogen gas circulation system. In the heated borehole, nitrogen gas circulation outflows to a desiccant container where water mass is measured daily during the experiment to quantify vapor removal. Thermocouples in the nearby boreholes allow us to determine the efficiency of several heater arrangements.

Using data from the shakedown testing, we build simulations using the Los Alamos developed Finite Element Heat and Mass transfer code (FEHM) to evaluate the experimental results and determine field-scale parameters. Simulations of the experiment allow us to confirm our conceptual model and provide checks on previously measure physical properties.

Results from this experiment show that water flow into the borehole agrees with previous experimental results and results from the TOUGH-FLAC simulator. Further, the shakedown test led to a design change to better transfer energy to the rock salt using an infrared heater. Simulations also show the impact of long-term pressure drainage during the 30 years that the drift was open before the heater testing.

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