Repository-Heat-Driven Hydrothermal Flow at Yucca Mountain, Part I: Modeling and Analysis

Buscheck, Thomas A.; Nitao, John J.

doi:10.13182/nt93-a34901

Cited by 62 publications

(54 citation statements)

References 9 publications

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“…As formation temperatures approach and exceed the boiling point at prevailing pressures, pore water vaporizes and a hot dry-out region develops in the vicinity of the waste emplacement tunnels. Since liquid water infiltrating down towards the repository will be subject to strong vaporization, the superheated rock zone forming above the repository may significantly reduce the possibility of water contacting the waste packages [Ramspott, 1991;Nitao et al, 1992;Wilder, 1993;Buscheck and Nitao, 1993]. The amount of infiltrating water that can reach the emplacement tunnels has significant implications for the integrity of the waste canisters and the subsequent release of contaminants.…”

Section: Motivationmentioning

confidence: 99%

TH{_}PULSE: Program for Calculating Infiltration of Episodic Liquid Fingers in Superheated Rock Fractures - Theory, User's Manual and Sample Applications

Birkhölzer¹

2002

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This report describes the code TH_PULSE developed at the Ernest Orlando Lawrence Berkeley National Laboratory (Berkeley Lab). The code handles gravity-driven flow of episodic infiltration events entering above-boiling rock-temperature regions. Such temperature conditions are expected, for example, after emplacement of heat-generating nuclear waste in underground repositories. Complex fluid-flow and heat-transfer phenomena occur, as the infiltrating water is subject to vigorous boiling from the hot rock. A new efficient semi-analytical method is presented herein that simulates such phenomena. It is assumed that flow forms in localized preferential flow paths (referred to as "fingers").The first section of this report gives the conceptual and mathematical background for the solution scheme. The second section is a user's manual for TH_PULSE, providing all information required to run the code, including a detailed description of the input and output files. In the third section, the new solution scheme is applied to several test cases. Sample simulations are performed for conditions representative of the potential nuclear waste repository at Yucca Mountain, Nevada. A brief summary is given in Section 4.-IV -INTENTIONALLY LEFT BLANK.-V -

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Section: Motivationmentioning

confidence: 99%

TH{_}PULSE: Program for Calculating Infiltration of Episodic Liquid Fingers in Superheated Rock Fractures - Theory, User's Manual and Sample Applications

Birkhölzer¹

2002

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“…Naturally Occuning nuclear reactors in the geological past [Cowan 1976 (Buscheck, Nitao, and Wilder 1993) and saturated geological environments by heat. In this context, it is important to emphasize that the concern is not that nuclear criticality occurs or that some radioactivity is added to the repository, but rather that it occurs suf%ciently o h for a time sufficient to generate significant amounts of heat.…”

Section: Avoidance Of Nuclear Criticalitymentioning

confidence: 99%

DUSCOBS - a depleted-uranium silicate backfill for transport, storage, and disposal of spent nuclear fuel

Forsberg¹,

Pope²,

Ashline³

et al. 1995

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This report has been reproduced directly from the best available copy. Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Table A1 ABSTRACTA Depleted Uranium Silicate Container Backfill System (DUSCOBS) is proposed that would use small, isotopicallydepleted uranium silicate glass beads as a backfill material inside storage, tramport, and repository waste packages containing spent nuclear fuel (SNF). The uranium silicate glass beads would fill all void space inside the package including the coolant channels inside SNF assemblies.Based on preliminary analysis, the following benefits have been identified. DUSCOBS improves repository waste package performance by three mechanisms. First, it reduces the radionuclide releases fiom SNF when water enters the waste package by creating a local uranium silicate saturated groundwater environment that suppresses (a) the dissolution andlor transformation of uranium dioxide fuel pellets and, hence, (b) the release of radionuclides incorporated into the SNF pellets. Second, the potential for long-term nuclear criticality is reduced by isotopic exchange of enriched uranium in SNF with the depleted uranium (DV) in the glass. Third, the backfill reduces radiation interactions bemeen SNF and the local environment (package and local geology) and thus reduces generation of hydrogen, acids, and other chemicals ;that degrade the waste package system. In addition, the DUSCOBS improves the integrity of the package by acting as a packing material and ensures criticality control for the package during SNF storage and transport. Finally, DUSCOBS provides a potential method to dispose of significant quantities of excess DU from uranium enrichment plants at potential economic savings. DUSCOBS is a new concept. Consequently, the concept has not been optimized or demonstrated in laboratow experiments. xi EXECUTIVE SUMMARY INTRODUCTIONIt is proposed that small, depleted uranium silicate @US) glass beads be used as a backfill material inside storage, transport, and repository waste packages containing light-water reactor (LW) spent nuclear fuel (SNF). The use of DUS glass beads has the potential to improve repository performance, improve SNF transport and storage, dispose of excess depleted uranium (DU), and reduce system costs. A mechanical description of the Depleted Uranium Silicate Container Backfill System (DUSCOBS) is provided followed by descriptions of how DUSCOBS performs its functions. DUSCOBS is a new concept. This report is a first description of DUSCOBS, its potential advantages, and the associated uncertainties.For the study herein, DUSCOBS was applied to the proposed U.S. Department of Energy (DOE) multipurpose canister (MPC) system. The MPC is an inner container for SNF storage containers, transport casks, and geological disposal packages. DUSCOBS is applicable to (1) alternative MPC designs and (2) other SNF transport, storage, and repository systems. MECHAMCAL DESCRIPTIONThe multipurpose canister (MPC) or waste package would first be loaded w...

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“…The two primary modes of water contact on the WP are (1) Regardless of whether mobile liquid water is present, ambient RH at the repository horizon…”

Section: Introductionmentioning

confidence: 99%

“…The localized dryout (LD) approach achieves these effects by maintaining a large temperature difference between the WP and the drift wall. The LD approach uses close axial WP spacing (generating a high line-heat load) in widely spaced drifts and an AML (~50-60 MTU/acre) that (1) is low enough that the boiling zones do not coalesce between drifts, thereby limiting condensate buildup above the drifts, and (2) l i m i t s far-field temperature rise. Higher lineal mass loadings (LML), wider drift spacings, and older spent nuclear fuel (SNF) increase the range of AMLs amenable to the LD approach.…”

mentioning

confidence: 99%

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Localized Dryout: an Approach for Managing the Thermal-Hydrological Effects of Decay Heat at Yucca Mountain

1995

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For a nuclear waste repository in the unsaturated zone at Yucca Mountain, there are two thermal loading approaches to using decay heat constructively-that is, to substantially reduce relative humidity and liquid flow near waste packages for a considerable time, and thereby limit waste package degradation and radionuclide dissolution and release. “Extended dryout” achieves these effects with a thermal load high enough to generate large-scale (coalesced) rock dryout. “Localized dryout”(which uses wide drift spacing and a thermal load too low for coalesced dryout) achieves them by maintaining a large temperature difference between the waste package and drift wail; this is done with close waste package spacing (generating a high line-heat load) and/or low-thermal-conductivity backfill in the drift. Backfill can greatly reduce relative humidity on the waste package in both the localized and extended dryout approaches. Besides using decay heat constructively, localized dryout reduces the possibility that far-field temperature rise and condensate buildup above the drifts might adversely affect waste isolation.

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Repository-Heat-Driven Hydrothermal Flow at Yucca Mountain, Part I: Modeling and Analysis

Cited by 62 publications

References 9 publications

TH{_}PULSE: Program for Calculating Infiltration of Episodic Liquid Fingers in Superheated Rock Fractures - Theory, User's Manual and Sample Applications

TH{_}PULSE: Program for Calculating Infiltration of Episodic Liquid Fingers in Superheated Rock Fractures - Theory, User's Manual and Sample Applications

DUSCOBS - a depleted-uranium silicate backfill for transport, storage, and disposal of spent nuclear fuel

Localized Dryout: an Approach for Managing the Thermal-Hydrological Effects of Decay Heat at Yucca Mountain

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