Permeability of Natural Rock Salt from the Waste Isolation Pilot Plant (WIPP) During Damage Evolution and Healing

Abstract

The U. S. Department of Energy has developed the Waste Isolation Pilot Plant (WIPP) in the bedded salt of southeastern New Mexico to demonstrate the safe disposal of radioactive transuranic wastes. Four vertical shafts provide access to the underground workings located at a depth of about 660 meters. These shafts connect the underground facility to the surface and potentially provide communication between lithologic units, so they will be sealed to limit both the release of hazardous waste from and fluid flow into the repository. The seal design must consider the potential for fluid flow through a disturbed rock zone (DRZ) that develops in the salt near the shafts. The D E , which forms initially during excavation and then evolves with time, is expected to have higher permeability than the native salt. The closure of the shaft openings (ie., through salt creep) will compress the seals, thereby inducing a compressive back-stress on the DRZ. This back-stress is expected to arrest the evolution of the D E , and with time will promote healing of damage. This paper presents laboratory data from tertiary creep and hydrostatic compression tests designed to characterize damage evolution and healing in WIPP salt. Healing is quantified in terms of permanent reduction in permeability, and the data are used to estimate healing times based on considerations of firstorder kinetics.

The disturbed rock zone at the Waste Isolation Pilot Plant.

“…In laboratory tests Costin and Wawersik (1980), Brodsky (1990) and Pfeifle and Hurtado (1998) have shown that the damage evolution process in salt is reversible through crack closure and healing. In the Costin and Wawersik study, a series of short-rod fracture toughness strength tests were performed to determine the tensile load required to initiate and propagate fractures in WIPP salt.…”

Influence of Stress Rate on Rheology – An Experimental Study on Rocksalt of Simla Himalaya, India

“…Hansen and Carter (1984) have carried out deformational experiments on very dry rocksalt from Avery Island Louisiana at elevated temperature and pressure both in constant stress mode and constant strain rate (Handin et al, 1986). Peach (1996), and Pfeifle and Hurtado (1998) have focused on the permeability of rocksalt under deformation. have proposed models which account for induced anisotropy.…”

Evaluating Micrometeorological Estimates of Groundwater Discharge from Great Basin Desert Playas

“…Hydraulic conductivities of playa sediments are better known than ET g rates because desert playas are comprised of fine‐grained sediments and salts. Hydraulic conductivities of clay and salt are uncensored values well established from the literature (Czarnecki ; Pfeifle and Hurtado ; Garcia et al ; Huntington et al ). Simulated ET g rates from the DIXIE‐HYDK and DEATH‐HYDK models likely are more representative of actual ET g from the BSP and SEP ET units than the micrometeorological measurements.…”

“…Evaporation of unmeasured and unaccounted surface water inputs likely biased high BREB ET g rates from the BSP and SEP. Isolating the groundwater component of measured evaporation from BSP and SEP was complicated by surface water inundation during flooding events in 1998and 2001. DeMeo et al (2003 attempted to correct the measurement record for flooding periods based on indirect evidence; however, no attempt was made to account for changes in groundwater storage from infiltrating flood waters in either the unsaturated or saturated zone.…”