Instrumentation of the thermal/structural interactions in situ tests at the Waste Isolation Pilot Plant (WIPP)

The Department of Energy has constructed the Waste Isolation Pilot Plant (WIPP) to develop the technology for the disposal of radioactive waste from defense programs. Sandia National Laboratories had the responsibility for the experimental activities at the WIPP and fielded several large-scale Thermal/Structural Interactions (TSI) in situ tests to validate techniques used to predict repository performance. The instrumentation of these tests involved the placement of over 4,200 gages including room closure gages, borehole extensometers, stress gages, borehole inclinometers, fixed reference gages, borehole strain gages, thermocouples, thermal flux meters, heater power gages, environmental gages, and ventilation gages. Most of the gages were remotely read instruments that were monitored by an automated data acquisition system, but manually read instruments were also used to provide early deformation information and to provide a redundancy of measurement for the remote gages. Instruments were selected that could operate in the harsh environment of the test rooms and that could accommodate the ranges of test room responses predicted by pretest calculations. Instruments were tested in the field prior to installation at the WIPP site and were modified to improve their performance. Other modifications were made to gages as the TSI tests progressed using knowledge gained from test maintenance. Quality assurance procedures were developed for all aspects of instrumentation including calibration, installation, and maintenance. The instrumentation performed exceptionally well and has produced a large quantity of quality information.