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Title: Experiments and Modeling in Support of Generic Salt Repository Science

Abstract

Salt is an attractive material for the disposition of heat generating nuclear waste (HGNW) because of its self-sealing, viscoplastic, and reconsolidation properties (Hansen and Leigh, 2012). The rate at which salt consolidates and the properties of the consolidated salt depend on the composition of the salt, including its content in accessory minerals and moisture, and the temperature under which consolidation occurs. Physicochemical processes, such as mineral hydration/dehydration salt dissolution and precipitation play a significant role in defining the rate of salt structure changes. Understanding the behavior of these complex processes is paramount when considering safe design for disposal of heat-generating nuclear waste (HGNW) in salt formations, so experimentation and modeling is underway to characterize these processes. This report presents experiments and simulations in support of the DOE-NE Used Fuel Disposition Campaign (UFDC) for development of drift-scale, in-situ field testing of HGNW in salt formations.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1340950
Report Number(s):
LA-UR-16-27329
TRN: US1701834
DOE Contract Number:
AC52-06NA25396
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; SALTS; RADIOACTIVE WASTES; TESTING; RADIOACTIVE WASTES DISPOSAL; Earth Sciences

Citation Formats

Bourret, Suzanne Michelle, Stauffer, Philip H., Weaver, Douglas James, Caporuscio, Florie Andre, Otto, Shawn, Boukhalfa, Hakim, Jordan, Amy B., Chu, Shaoping, Zyvoloski, George Anthony, and Johnson, Peter Jacob. Experiments and Modeling in Support of Generic Salt Repository Science. United States: N. p., 2017. Web. doi:10.2172/1340950.
Bourret, Suzanne Michelle, Stauffer, Philip H., Weaver, Douglas James, Caporuscio, Florie Andre, Otto, Shawn, Boukhalfa, Hakim, Jordan, Amy B., Chu, Shaoping, Zyvoloski, George Anthony, & Johnson, Peter Jacob. Experiments and Modeling in Support of Generic Salt Repository Science. United States. doi:10.2172/1340950.
Bourret, Suzanne Michelle, Stauffer, Philip H., Weaver, Douglas James, Caporuscio, Florie Andre, Otto, Shawn, Boukhalfa, Hakim, Jordan, Amy B., Chu, Shaoping, Zyvoloski, George Anthony, and Johnson, Peter Jacob. Thu . "Experiments and Modeling in Support of Generic Salt Repository Science". United States. doi:10.2172/1340950. https://www.osti.gov/servlets/purl/1340950.
@article{osti_1340950,
title = {Experiments and Modeling in Support of Generic Salt Repository Science},
author = {Bourret, Suzanne Michelle and Stauffer, Philip H. and Weaver, Douglas James and Caporuscio, Florie Andre and Otto, Shawn and Boukhalfa, Hakim and Jordan, Amy B. and Chu, Shaoping and Zyvoloski, George Anthony and Johnson, Peter Jacob},
abstractNote = {Salt is an attractive material for the disposition of heat generating nuclear waste (HGNW) because of its self-sealing, viscoplastic, and reconsolidation properties (Hansen and Leigh, 2012). The rate at which salt consolidates and the properties of the consolidated salt depend on the composition of the salt, including its content in accessory minerals and moisture, and the temperature under which consolidation occurs. Physicochemical processes, such as mineral hydration/dehydration salt dissolution and precipitation play a significant role in defining the rate of salt structure changes. Understanding the behavior of these complex processes is paramount when considering safe design for disposal of heat-generating nuclear waste (HGNW) in salt formations, so experimentation and modeling is underway to characterize these processes. This report presents experiments and simulations in support of the DOE-NE Used Fuel Disposition Campaign (UFDC) for development of drift-scale, in-situ field testing of HGNW in salt formations.},
doi = {10.2172/1340950},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jan 19 00:00:00 EST 2017},
month = {Thu Jan 19 00:00:00 EST 2017}
}

Technical Report:

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  • An example case is presented for testing analytical thermal models. The example case represents thermal analysis of a generic repository in bedded salt at 500 m depth. The analysis is part of the study reported in Matteo et al. (2016). Ambient average ground surface temperature of 15°C, and a natural geothermal gradient of 25°C/km, were assumed to calculate temperature at the near field. For generic salt repository concept crushed salt backfill is assumed. For the semi-analytical analysis crushed salt thermal conductivity of 0.57 W/m-K was used. With time the crushed salt is expected to consolidate into intact salt. In thismore » study a backfill thermal conductivity of 3.2 W/m-K (same as intact) is used for sensitivity analysis. Decay heat data for SRS glass is given in Table 1. The rest of the parameter values are shown below. Results of peak temperatures at the waste package surface are given in Table 2.« less
  • The thermomechanical response of a generic bedded salt stratigraphy accommodating a spent fuel repository at a depth of 610 m in a relatively thin salt bed is investigated. The thermal density at waste emplacement was assumed to be 14.8 W/m/sup 2/ (60 kW/acre). Emphasis is placed on rock mass properties, elastic and thermal anisotropy (within the shale layers), and structural discontinuities defined as preferred planes of weakness. No attempt is made to include long-term effects of geologic actions, chemical processes, groundwater, and pore water. The rock mass is assumed to contain pre-existing joints and fissures. Therefore, the stratigraphy encompassing themore » repository (excluding the salt beds) was assumed to be incapable of supporting tensile stresses. Thermoelastic/plastic response of the various sedimentary formations is considered for the intact rock mass and several orientations of preferred planes of weakness. The results indicate an intact buffer zone between the upper strata and the repository approximately 450 m thick, which underwent no irreversible deformation. Contained plastic deformation was observed below the repository along preferred planes of weakness dipping at 60 and 120 degrees. The structural response of this generic bedded salt stratigraphy does not appear to be detrimental to the overall waste containment in the repository.« less
  • This report illustrates an approach to quantitatively document the degree of technical conservatism incorporated into the design of a hypothetical geologic waste isolation system in a generic bedded salt stratigraphy. The report develops performance constraints for the critical barriers within each subsystem and for the system as a whole. The interface between integrity and loss of function is quantitatively defined for each performance constraint. A conservative margin is applied to this interface to arrive at a design basis. The waste isolation system design is then analyzed to ensure that the design bases are met for the effective lifetimes of eachmore » barrier. This approach enables the reader to scrutinize both the methodology and the design to determine for himself in the degreeof technical conservatism incorporated into the waste isolation design.« less
  • In the case of repositories in salt, adsorption/desorption reactions with salt are expected to be minimal. If solubility-controlling solids of radionuclides are present in the waste or can form in the engineered barrier system, the upper concentration limits of radionuclides that can be leached from the wastes will be solubility-limited but independent of the release scenarios, hydrologic transport characteristics, and adsorption/desorption reactions. The available thermochemical data show that most of the radioactive elements, such as actinides, that are of concern over long repository storage times form solubility-controlling solids. Therefore, it should be possible to set upper limits on the concentrationsmore » of these radioactive elements that can be leached from wastes disposed of in salt repositories. To set upper limits, data are needed for solid phases that form readily, have low solubilities, and either are present in wastes (spent fuel, waste glasses, etc.) or can form readily in the geologic environment. Factors that would lower the maximum concentrations in leachates include an increase in the crystallinity of amorphous precipitates, the presence of crystalline solids in the wastes, and the formation of solid solutions of the actinides. 11 refs.« less