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Impact of Corrections to the Spallings Volume Calculation on Waste Isolation Pilot Plant Performance Assessment [Poster]

Kicker, Dwayne C.; Herrick, Courtney G.; Zeitler, Todd Z.

The numerical code DRSPALL (from direct release spallings) is written to calculate the volume of Waste Isolation Pilot Plant solid waste subject to material failure and transport to the surface (i.e., spallings) as a result of a hypothetical future inadvertent drilling intrusion into the repository. An error in the implementation of the DRSPALL finite difference equations was discovered and documented in a software problem report in accordance with the quality assurance procedure for software requirements. This paper describes the corrections to DRSPALL and documents the impact of the new spallings data from the modified DRSPALL on previous performance assessment calculations. Updated performance assessments result in more simulations with spallings, which generally translates to an increase in spallings releases to the accessible environment. Total normalized radionuclide releases using the modified DRSPALL data were determined by forming the summation of releases across each potential release pathway, namely borehole cuttings and cavings releases, spallings releases, direct brine releases, and transport releases. Because spallings releases are not a major contributor to the total releases, the updated performance assessment calculations of overall mean complementary cumulative distribution functions for total releases are virtually unchanged. Therefore, the corrections to the spallings volume calculation did not impact Waste Isolation Pilot Plant performance assessment calculation results.

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TYPE Conference Poster YEAR 2015
OSTI

DRSPALL: Impact of the Modification of the Numerical Spallings Model on Waste Isolation Pilot Plant Performance Assessment

Kicker, Dwayne C.; Herrick, Courtney G.; Zeitler, Todd Z.; Malama, Bwalya; Rudeen, David; Gilkey, Amy P.

The numerical code DRSPALL (from direct release spallings) is written to calculate the volume of Waste Isolation Pilot Plant (WIPP) solid waste subject to material failure and transport to the surface as a result of a hypothetical future inadvertent drilling intrusion. An error in the implementation of the DRSPALL finite difference equations was discovered as documented in Software Problem Report (SPR) 13-001. The modifications to DRSPALL to correct the finite difference equations are detailed, and verification and validation testing has been completed for the modified DRSPALL code. The complementary cumulative distribution function (CCDF) of spallings releases obtained using the modified DRSPALL is higher compared to that found in previous WIPP performance assessment (PA) calculations. Compared to previous PAs, there was an increase in the number of vectors that result in a nonzero spallings volume, which generally translates to an increase in spallings releases. The overall mean CCDFs for total releases using the modified DRSPALL are virtually unchanged, thus the modification to DRSPALL did not impact WIPP PA calculation results.

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TYPE SAND Report YEAR 2015
DOIOSTI

Impact of Corrections to the Spallings Volume Calculation on Waste Isolation Pilot Plant Performance Assessment

Kicker, Dwayne C.; Herrick, Courtney G.; Zeitler, Todd Z.

The numerical code DRSPALL (from direct release spallings) is written to calculate the volume of Waste Isolation Pilot Plant solid waste subject to material failure and transport to the surface (i.e., spallings) as a result of a hypothetical future inadvertent drilling intrusion into the repository. An error in the implementation of the DRSPALL finite difference equations was discovered and documented in a software problem report in accordance with the quality assurance procedure for software requirements. This paper describes the corrections to DRSPALL and documents the impact of the new spallings data from the modified DRSPALL on previous performance assessment calculations. Updated performance assessments result in more simulations with spallings, which generally translates to an increase in spallings releases to the accessible environment. Total normalized radionuclide releases using the modified DRSPALL data were determined by forming the summation of releases across each potential release pathway, namely borehole cuttings and cavings releases, spallings releases, direct brine releases, and transport releases. Because spallings releases are not a major contributor to the total releases, the updated performance assessment calculations of overall mean complementary cumulative distribution functions for total releases are virtually unchanged. Therefore, the corrections to the spallings volume calculation did not impact Waste Isolation Pilot Plant performance assessment calculation results.

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TYPE Conference Poster YEAR 2015
OSTI

Effects of thermodynamic ensembles and mineral surfaces on interfacial water structure

Physical Chemistry Chemical Physics

Zeitler, Todd Z.; Greathouse, Jeffery A.; Cygan, Randall T.

While performing molecular dynamics simulations of water or aqueous solutions in a slab geometry, such as at mineral surfaces, it is important to match bulk water density in the diffuse region of the model system with that expected for the appropriate experimental conditions. Typically, a slab geometry represents parallel surfaces with a variable region of confined water (this region can range in size from a few Ångstroms to many tens of Ångstroms). While constant-pressure simulations usually result in appropriate density values in the bulk diffuse region removed from either surface, constant-volume simulations have also been widely used, sometimes without careful consideration of the method for determining water content. Simulations using two thermodynamic ensembles as well as two methods for calculating the water-accessible volume have been investigated for two distinct silicate surfaces - hydrophilic cristobalite (111) and hydrophobic pyrophyllite (001). In cases where NPT simulations are not feasible, a simple geometry-based treatment of the accessible volume can be sufficient to replicate bulk water density far from the surface. However, the use of the Connolly method can be more appropriate in cases where a surface is less well-defined. Specific water-surface interactions (e.g., hydrophobic repulsion) also play a role in determining water content in a confined water simulation. While reported here for planar surfaces, these results can be extended to an interface with any solvent, or to other types of surfaces and geometries. © the Owner Societies 2012.

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TYPE Conference YEAR 2012
OSTIScopus

Effects of thermodynamic ensembles and mineral surfaces on interfacial water structure

Physical Chemistry Chemical Physics

Zeitler, Todd Z.; Greathouse, Jeffery A.; Cygan, Randall T.

While performing molecular dynamics simulations of water or aqueous solutions in a slab geometry, such as at mineral surfaces, it is important to match bulk water density in the diffuse region of the model system with that expected for the appropriate experimental conditions. Typically, a slab geometry represents parallel surfaces with a variable region of confined water (this region can range in size from a few Ångstroms to many tens of Ångstroms). While constant-pressure simulations usually result in appropriate density values in the bulk diffuse region removed from either surface, constant-volume simulations have also been widely used, sometimes without careful consideration of the method for determining water content. Simulations using two thermodynamic ensembles as well as two methods for calculating the water-accessible volume have been investigated for two distinct silicate surfaces - hydrophilic cristobalite (111) and hydrophobic pyrophyllite (001). In cases where NPT simulations are not feasible, a simple geometry-based treatment of the accessible volume can be sufficient to replicate bulk water density far from the surface. However, the use of the Connolly method can be more appropriate in cases where a surface is less well-defined. Specific water-surface interactions (e.g., hydrophobic repulsion) also play a role in determining water content in a confined water simulation. While reported here for planar surfaces, these results can be extended to an interface with any solvent, or to other types of surfaces and geometries. © the Owner Societies 2012.

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TYPE Journal Article YEAR 2012
OSTIScopus
Results 51–92 of 92
Results 51–92 of 92