The thermal integrity of spent nuclear fuels has to be maintained during their long-term dry storage. The detailed temperature distributions of spent fuel assemblies are essential for evaluating the integrity of their dry storage systems. In this study, a subchannel analysis model was developed for a canister of a single fuel assembly using the COBRA-SFS code. The thermal parameters affecting the peak cladding temperature (PCT) of the spent fuel assembly were identified, and sensitivity analyses were performed based on these parameters. The subchannel analysis results indicated the presence of a recirculation flow, based on natural convection, between the fuel assembly and downcomer region. The sensitivity analysis of the thermal parameters indicated that the PCT was affected by the emissivity of the fuel cladding and basket, convective heat transfer coefficient, and thermal conductivity of the fluid. However, the effects of the wall friction factor of the canister, form loss coefficient of the grid spacers, and thermal conductivities of the solid materials, on the PCT were predominantly ignored.

1. Introduction
2. Overview of Thermal Test Equipment
3. Subchannel Analysis of a Single FuelAssembly
    3.1 Subchannel Analysis Modeling
    3.2 Subchannel Analysis Results for a SingleFuel Assembly
4. Sensitivity Analysis of Thermal ParametersAffecting the Peak Cladding Temperature
    4.1 Sensitivity Analysis of Surface Emissivity
    4.2 Sensitivity Analysis of Convective HeatTransfer Coefficients
    4.3 Sensitivity Analysis of Flow ResistanceCoefficients
    4.4 Sensitivity Analysis of Thermal Conductivities
5. Conclusions
Conflict of Interest
Acknowledegments
Nomenclatures

• Ju-Chan Lee(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea) Corresponding Author
• Doyun Kim(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea)
• Seung-Hwan Yu(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea)
• Sungho Ko(Chungnam National University, 99, Daehak-ro, Yuseong-gu, Daejeon 34134, Republic of Korea)