COBRA-SFS: A thermal-hydraulic analysis code for spent fuel storage and transportation casks

Michener, T.E.; Rector, David R.; Cuta, Judith M.; Dodge, Richard E.; Enderlin, Carl W.

doi:10.2172/124912

Cited by 15 publications

(18 citation statements)

References 10 publications

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“…However, for CFD packages such as STAR-CCM+ , the size of the model needed to represent the complex geometry of a multi-assembly DSC exceeds the capability of current computer platforms. For this reason, planned future work on this project includes developing a detailed, best-estimate model of the DSC using the COBRA-SFS code (Michener, et al, 1995), to obtain realistic estimates of canister internal temperatures, including rod by rod fuel cladding temperatures and temperature distributions. Experience suggests that for steady-state calculations, the peak cladding temperatures can be expected to be within 10 degrees-F (~6 degrees-C) of the values predicted with the k-effective model.…”

Section: Fuel Effective Conductivity Modelmentioning

confidence: 99%

Thermal Modeling of NUHOMS HSM-15 and HSM-1 Storage Modules at Calvert Cliffs Nuclear Power Station ISFSI

Suffield¹,

Fort²,

Adkins³

et al. 2012

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SummaryThis report fulfills the M3 milestone M3FT-12PN0810041, "Report on Realistic Temperature Profiles", under Work Package FT-12PN081004.As part of the Used Fuel Disposition Campaign of the Department of Energy (DOE), visual inspections and temperature measurements were performed on two storage modules in the Calvert Cliffs Nuclear Power Station's Independent Spent Fuel Storage Installation (ISFSI). The inspection procedure included surface temperature measurements on one end of the DSC within the storage module. The data obtained in the inspections at Calvert Cliffs provide an opportunity to develop structural and thermal models that can yield realistic temperature predictions for actual storage systems, in contrast to conservative and bounding design basis calculations.Detailed models of the concrete storage modules to be examined were developed using STAR-CCM+ (version 7.02; CD-Adapco, 2012). The immediate purpose of this modeling effort is to obtain temperature predictions in actual storage conditions for the module, DSC, and DSC contents, including preliminary estimates of fuel cladding temperatures for the SNF. The long-term goal of this work is to obtain realistic evaluations of thermal performance of actual SNF storage systems over extended periods, which will require developing a detailed COBRA-SFS (Michener, et al., 1987) model of the DSC internals, in addition to the large system models. The approach used in this study omits many of the conservatisms and bounding assumptions normally used in design-basis and safety-basis calculations for spent fuel storage systems. The results of this study cannot be used in licensing basis evaluations of the Calvert Cliffs ISFSI, or any other spent fuel storage facility.The storage modules used for this study are HSM-1 and HSM-15 in the Calvert Cliffs Nuclear Power Station's ISFSI, each containing a 24P DSC loaded with 24 CE 14x14 spent fuel assemblies. The total decay heat load for the DSC in HSM-15 was 10.8 kW at the time of loading, and was calculated to be 7.6 kW as of June 2012. The total decay heat load for the DSC in HSM-1 was calculated to be 4.1 kW as of June 2012. The base case for thermal evaluation of the 24P DSC in HSM-15 assumed an ambient temperature of 58°F (14°C). This value was determined using historical climatology data from a National Oceanic and Atmospheric Administration (NOAA) database, and verified with annual ambient temperature data from monitoring stations at the Calvert Cliffs ISFSI. Bounding sensitivity studies on the effect of ambient air temperature were performed for two cases; a 'summer case' at 77°F based on average temperatures in July, and a 'winter case' at 35°F, based on average temperatures in January. Figure On June 27 th and 28 th , 2012, visual inspections, surface sampling, and temperature measurements were performed on HSM-1 and HSM-15 at the Calvert Cliffs Nuclear Power Station ISFSI. Due to physical constraints on the accessible regions of the DSC and considerations of worker safety, reliable temperature measuremen...

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Section: Fuel Effective Conductivity Modelmentioning

confidence: 99%

Thermal Modeling of NUHOMS HSM-15 and HSM-1 Storage Modules at Calvert Cliffs Nuclear Power Station ISFSI

Suffield¹,

Fort²,

Adkins³

et al. 2012

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“…The COBRA-SFS modeling capabilities and the conservation equations are described briefly in the following subsections. For a detailed description of the derivation of the conservation equations, and the assumptions and approximations used in the code, refer to the primary documentation of Cycle 2 (Michener et al 1995).…”

Section: Cobra-sfs Code Descriptionmentioning

confidence: 99%

“…This geometry is illustrated in Figure 2.1, which shows the subchannel in relation to the assembly. This approach can also be generalized to apply to large regions of the flow field, wherein a single channel can represent a large number of individual subchannels in a fuel rod array, or large open regions that do not contain fuel rods within a storage cask (refer to Michener et al 1995; specifically, Part Il-User Guide, for a more complete discussion).…”

Section: Modeling Capabilitiesmentioning

confidence: 99%

“…The cask body is of forged steel surrounded by a resin layer for neutron shielding and has a steel outer shell. The overall (a) Electrically heated bundles modeling intact PWR fuel in a square canister; refer to the Cycle 2 release document (Michener et al 1995 Decay heat rates in the fuel rods for the duration of the tests were calculated using ORIGEN2 (Croff 1980). The average power per assembly was approximately 850 kW, and the predicted power at the start of testing was 20.6 kW.…”

Section: Tn24p(b) Cask Transientmentioning

confidence: 99%

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Verification and validation of COBRA-SFS transient analysis capability

Rector¹,

Michener²,

Cuta³

1998

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“…The influence of load pattern on the thermal performance of the cask was also determined through analysis using the COBRA-SFS code (Michener et al 1995). The extensive program of cask heat transfer carried out under the Commercial Spent Fuel Management (CSFM) Program demonstrated the reliability of the COBRA-SFS code in predicting the heat transfer capabilities of spent fuel storage casks.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Effect of Fuel Assembly Loading Patterns on Thermal and Shielding Performance of a Spent Fuel Storage/Transportation Cask

Cuta¹,

Jenquin²,

McKinnon³

2001

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Executive SummaryThe licensing of spent fuel storage casks is generally based on conservative analyses that assume a storage system uniformly loaded with design basis fuel. The design basis fuel typically assumes a maximum assembly enrichment, maximum burnup, and minimum cooling time. These conditions set the maximum decay heat loads and radioactive source terms for the design. Recognizing that reactor spent fuel pools hold spent fuel with an array of initial enrichments, burnups, and cooling times, this study was performed to evaluate the effect of load pattern on peak cladding temperature and cask surface dose rate.In 1991, DOE pursued a cooperative program with the Sacramento Municipal Utility District (SMUD). Part of the cooperative program was to demonstrate the effect of cask loading on the thermal and shielding performance of a cask containing spent nuclear fuel. At the time the cooperative agreement was established between DOE and SMUD, SMUD had fuel with cooling times ranging from 5 to 17 years, burnups of 8 to 38 GWd/MTU, and enrichments of 2.01 to 3.43% at its Rancho Seco nuclear power plant. It was thought that there was enough variability in the fuel to determine the effect of load pattern on dose rates. The effect of load pattern on the thermal performance of the casks was to be determined analytically using a computer code that had been validated extensively. With the termination of the DOE/SMUD cooperative agreement prior to cask loading, an analytical method was chosen to determine the effect of load pattern on dose rates. The codes were validated using data generated in other DOE cooperative efforts.The cask used in the analysis was similar to the TN-24P spent fuel storage cask. The TN-24P spent fuel storage cask is designed to hold 24 spent fuel assemblies with a total heat load of 24 kW. The cask body is forged steel surrounded by a resin layer for neutron shielding and a steel outer shell. The overall cask length is 16 ft (5.0 m), and the outer diameter is 7. The influence of load pattern on the thermal performance of the cask was determined through analysis with the COBRA-SFS code. The same COBRA-SFS model previously developed for analyzing the TN-24P cask was used in this parametric study. Three radial power distributions were considered. Each load pattern had an average decay heat output of 1 kW per fuel assembly for a total output of 24 kW from the fully loaded cask. Seventeen different load patterns were selected, and three backfill conditions were considered for each load pattern. The backfill media selected were helium, nitrogen, and vacuum. Except for the backfill medium and the radial power distribution, nothing was changed in the COBRA-SFS input between cases. This combination of load patterns and backfill gases provided a total of 51 runs in the test matrix.iv

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COBRA-SFS: A thermal-hydraulic analysis code for spent fuel storage and transportation casks

Cited by 15 publications

References 10 publications

Thermal Modeling of NUHOMS HSM-15 and HSM-1 Storage Modules at Calvert Cliffs Nuclear Power Station ISFSI

Thermal Modeling of NUHOMS HSM-15 and HSM-1 Storage Modules at Calvert Cliffs Nuclear Power Station ISFSI

Verification and validation of COBRA-SFS transient analysis capability

Evaluation of Effect of Fuel Assembly Loading Patterns on Thermal and Shielding Performance of a Spent Fuel Storage/Transportation Cask

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