Review of the Department of Energy's Plans for Disposal of Surplus Plutonium in the Waste Isolation Pilot Plant (2020) / Chapter Skim
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Appendix C: How Salt Repositories Work
Appendix C: How Salt Repositories Work
Pages 133-139
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From page 133... ...
have been explored for implementing deep geologic disposal concepts, particularly for heatgenerating high level wastes or wastes otherwise contaminated with long-lived isotopes such as plutonium239. There has been considerable research, development, and salt repository experience extending back many decades, not only for radioactive wastes but also for the strategic stockpiling of petroleum (NRC, 1957; Hansen and Leigh, 2011; Winterle et al., 2012; von Berlepsch and Haverkamp, 2016)
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Multiple post-closure performance assessments produced using computer models (and their subsequent contribution to EPA certification of WIPP compliance) have demonstrated that in the nominal undisturbed scenario (absent human intrusion by drilling)
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Performance assessments that consider inadvertent human intrusion into the repository are referred to as the disturbed scenario. Disturbed scenario via drilling intrusion has four release mechanisms that are modeled as • Cuttings and cavings, which are the waste solids directly intersected by the drill; • Spallings, which entrain solid materials pushed into the borehole with transport to surface; • Direct brine releases, fluid that brings dissolved actinides to the surface; and • Long-term groundwater releases, wherein radionuclides reach the Culebra aquifer and move past the compliance boundary.
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From page 136... ...
A key element of the disturbed scenario is the presumption that inadvertent drilling will pass through the waste emplacement horizon and possibly intersect a pressurized brine pocket beneath the repository (see Figure C-1)
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With the potential for direct releases through inadvertent human intrusion, concerns about long-term performance shift to those aspects of the waste and/or repository design that might inhibit or promote the postulated releases through drilling such as gas generation, radionuclide solubility, panel closures, waste emplacement, drilling rates, engineered barriers, or criticality. This is one reason for the WIPP waste acceptance criteria requirement to specify the waste and waste package characteristics for each waste stream, and noting not just the radionuclide inventory, but also the waste material parameters and waste packaging materials (e.g., sludge, cellulosic, rubber, metals, cement, organic and inorganic material, complexing agents, and oxyanion mass)
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From page 138... ...
This leads to the third key aspect of WIPP: the regulatory framework is such that a greater initial inventory allows a greater radioactivity release in curies, as determined over the 10,000-year period. Historically, WIPP performance assessment results have shown little difference in calculated releases solely as a result of inventory changes (see Figure C-4)
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From page 139... ...
2014. DOE Compliance Recertification application 2014 Title 40 CFR Part 191 Subparts B and C Compliance Recertification Application 2014 for the Waste Isolation Pilot Plant.
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