COBRA-SFS (Spent-Fuel Storage) thermal-hydraulic analyses of the CASTOR-1C and REA 2023 BWR storage casks containing consolidated spent fuel

Technical Report · Mon Dec 01 04:00:00 EST 1986

DOI:https://doi.org/10.2172/6967831· OSTI ID:6967831

Rector, D R; Cuta, J M; Lombardo, N J

Consolidation of spent nuclear fuel rods is being considered as one option for more efficient and compact storage of reactor spent fuel assemblies. In this concept, rods from two disassembled spent fuel assemblies will be consolidated in a space originally intended to store a single unconsolidated assembly. The thermal performance of consolidated fuel rods in dry storage, especially in multiassembly storage systems, is one of the major issues that must be addressed prior to implementation. In this study, Pacific Northwest Laboratory researchers performed thermal-hydraulic analyses for both the REA 2023 cask and the CASTOR-1C cask containing either unconsolidated or consolidated BWR spent fuel assemblies. The objective was to determine the effect of consolidating spent fuel assemblies on the temperature distributions within both types of casks. Two major conclusions resulted from this study. First, a lumping technique (combining rods and flow channels), which reduces the number of computational nodes required to model complex multiassembly geometries, could be used for both unconsolidated and consolidated rods with negligible effect on prediction accuracies. Second, with a relatively high thermal conductivity backfill gas (e.g., helium), the predicted peak fuel rod temperature in a canister of consolidated rods generating the same amount of heat as an unconsolidated assembly is essentially the same as the peak temperature in the unconsolidated assembly. In contrast, with a relatively low thermal conductivity backfill gas (e.g., nitrogen), the opposite is true and the predicted peak temperature in a consolidated canister is significantly higher than in an unconsolidated assembly. Therefore, when rods are consolidated, selection of the backfill gas is important in maintaining peak rod temperatures below allowable values for rods with relatively high decay heat generation rates.

• Research Organization: Pacific Northwest Lab., Richland, WA (USA)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 6967831
• Report Number(s): PNL-5802; ON: DE87004450
• Country of Publication: United States
• Language: English

Related Subjects

050900* -- Nuclear Fuels-- Transport
Handling
& Storage
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
C CODES
CASKS
COMPUTER CODES
CONFIGURATION
CONTAINERS
DRY STORAGE
ENERGY TRANSFER
FUEL ELEMENTS
FUEL RODS
HEAT TRANSFER
REACTOR COMPONENTS
SPENT FUEL CASKS
SPENT FUEL STORAGE
STORAGE
TEMPERATURE DISTRIBUTION