Studies of Electrical and Electromagnetic Methods for Characterizing Salt Properties at the WIPP (Waste Isolation Pilot Project) Site, New Mexico

摘要

At the Waste Isolation Pilot Project Site in southeastern New Mexico, technical and engineering issues related to the long-term storage of hazardous wastes in bedded salt are being studied. For nuclear waste repositories with both long operational periods (50 yr) and long performance assessment periods (10,000 yr), the Disturbed Rock Zone (the zone of rock in which the mechanical and hydrologic properties have changed in response to excavation; abbreviated as DRZ) is important to both operational (e.g., slab or fracture failure of the excavation) and long-term performance (e.g., seal system performance and fluid transport). Because of the large contrast in electrical conductivity between crystalline salt and salt saturated with water, it is to be expected that electrical geophysical methods may play an important role in delineating portions of the DRZ. The Colorado School of Mines, under contract to Sandia National Laboratories, has carried out experimental surveys using the direct current electrical method and two electromagnetic methods underground in the mine workings. The results suggest that the various electrical methods are effective in locating low resistivity zones in the salt, which probably represent moisture-rich zones. Furthermore, it appears that such measurements might well be further optimized in terms of survey effort and design of systems to provide a high response to small-scale conductive features in the salt. 8 refs., 16 figs.