B.M. Butcher

Bio: B.M. Butcher is an academic researcher from Sandia National Laboratories. The author has contributed to research in topics: Waste Isolation Pilot Plant & Waste disposal. The author has an hindex of 2, co-authored 2 publications receiving 11 citations.

The advantages of a salt/bentonite backfill for Waste Isolation Pilot Plant disposal rooms

Abstract: This paper concludes that a 70/30 wt % salt/bentonite mixture is preferable to pure crushed salt as backfill for disposal rooms in the Waste Isolation Pilot Plant. The Waste Isolation Pilot Plant, near Carlsbad, NM, is designed to be the first mined geologic repository for the safe disposal of transuranic (TRU) radioactive waste generated by DOE defense programs since 1970. The repository is located about 655 m below the land surface in an extensive bedded salt formation. This report examines the performance of two backfill materials with regard to various selection criteria, such as the need for low permeability after closure, chemical stability, strength, ease of emplacement, and sorption potential for brine and radionuclides. Both salt and salt/bentonite are expected to consolidate to a state of permeability {le} 10{sup {minus}18} m{sup 2} that is adequate for satisfying regulations for nuclear repositories. The results of finite-element calculations that were used to arrive at this conclusion will be described. The real advantage of the salt/bentonite. backfill depends, therefore, on bentonite`s potential for sorbing brine and radionuclides. Estimates of the impact of these properties on backfill performance are presented.

Mechanical Analyses of Wipp Disposal Rooms Backfilled with Either Crushed Salt or Crushed Salt-Bentonite

Abstract: 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.

Permeability of WIPP Salt During Damage Evolution and Healing

Abstract: The presence of damage in the form of microcracks can increase the permeability of salt. In this paper, an analytical formulation of the permeability of damaged rock salt is presented for both initially intact and porous conditions. The analysis shows that permeability is related to the connected (i.e., gas accessible) volumetric strain and porosity according to two different power-laws, which may be summed to give the overall behavior of a porous salt with damage. This relationship was incorporated into a constitutive model, known as the Multimechanism Deformation Coupled Fracture (MDCF) model, which has been formulated to describe the inelastic flow behavior of rock salt due to coupled creep, damage, and healing. The extended model was used to calculate the permeability of rock salt from the Waste Isolation Pilot Plant (WIPP) site under conditions where damage evolved with stress over a time period. Permeability changes resulting from both damage development under deviatoric stresses and damage healing under hydrostatic pressures were considered. The calculated results were compared against experimental data from the literature, which indicated that permeability in damaged intact WIPP salt depends on the magnitude of the gas accessible volumetric strain and not on the total volumetric strain. Consequently, the permeability of WIPP salt is significantly affected by the kinetics of crack closure, but shows little dependence on the kinetics of crack removal by sintering.

Bentonite as a waste isolation pilot plant shaft sealing material

Abstract: Current designs of the shaft sealing system for the Waste Isolation Pilot Plant (WIPP) propose using bentonite as a primary sealing component. The shaft sealing designs anticipate that compacted bentonite sealing components can perform through the 10,000-year regulatory period and beyond. To evaluate the acceptability of bentonite as a sealing material for the WIPP, this report identifies references that deal with the properties and characteristics of bentonite that may affect its behavior in the WIPP environment. This report reviews published studies that discuss using bentonite as sealing material for nuclear waste disposal, environmental restoration, toxic and chemical waste disposal, landfill liners, and applications in the petroleum industry. This report identifies the physical and chemical properties, stability and seal construction technologies of bentonite seals in shafts, especially in a saline brine environment. This report focuses on permeability, swelling pressure, strength, stiffness, longevity, and densification properties of bentonites.

Coupled multiphase flow and closure analysis of repository response to waste-generated gas at the Waste Isolation Pilot Plant (WIPP)

Abstract: A long-term assessment of the Waste Isolation Pilot Plant (WIPP) repository performance must consider the impact of gas generation resulting from the corrosion and microbial degradation of the emplaced waste. A multiphase fluid flow code, TOUGH2/EOS8, was adapted to model the processes of gas generation, disposal room creep closure, and multiphase (brine and gas) fluid flow, as well as the coupling between the three processes. System response to gas generation was simulated with a single, isolated disposal room surrounded by homogeneous halite containing two anhydrite interbeds, one above and one below the room. The interbeds were assumed to have flow connections to the room through high-permeability, excavation-induced fractures. System behavior was evaluated by tracking four performance measures: (1) peak room pressure; (2) maximum brine volume in the room; (3) total mass of gas expelled from the room; and (4) the maximum gas migration distance in an interbed. Baseline simulations used current best estimates of system parameters, selected through an evaluation of available data, to predict system response to gas generation under best-estimate conditions. Sensitivity simulations quantified the effects of parameter uncertainty by evaluating the change in the performance measures in response to parameter variations. In the sensitivity simulations, a single parameter value was varied to its minimum and maximum values, representative of the extreme expected values, with all other parameters held at best-estimate values. Sensitivity simulations identified the following parameters as important to gas expulsion and migration away from a disposal room: interbed porosity; interbed permeability; gas-generation potential; halite permeability; and interbed threshold pressure. Simulations also showed that the inclusion of interbed fracturing and a disturbed rock zone had a significant impact on system performance.

Laboratory assessment of compressive strength and permeabilty of crushed salt during consolidation

Abstract: THAI) ..................................................................................................... I ABSTRACT (ENGLISH) ............................................................................................. II ACKNOWLEDGEMENTS .........................................................................................III TABLE OF CONTENTS ............................................................................................ IV LIST OF TABLES ..................................................................................................... VII LIST OF FIGURES .................................................................................................. VIII SYMBOLS AND ABBREVIATIONS ...................................................................... XII CHAPTER