IMPROVEMENT OF INPUT PARAMETERS FOR THE ESTIMATION OF FUEL ROD TEMPERATURE IN DRY TRANSPORT CASK

A typical PWR spent fuel bundle has a 17x 17 rod array, and an analysis requires a very long computation time and a vast amount of memory. Therefore, we applied the lumped fuel bundle analysis approach with the homogenized method to estimate the fuel cladding temperature efficiently. Thermal analysis results for lumped fuel bundles showed an excessive radiative heat transfer, and we applied an emissivity modification factor to compensate for this radiation effect. The value of the factor decreased as the number of the rods in the homogenized array decreased. For the lumped 8x8 array, the best emissivity modification factor was shown to be 0.40. The rod emissivity of 0.8 is generally recommended to be used in COBRA-SFS[D. R. Rector et al.] calculations. Therefore, we can use the modified rod emissivity of 0.32 for lumped 8x8 array. There are good agreements between the results from lumped 8x8 array bundle and the results from real 17x17 array bundle. By homogenization, we can increase the computational speed substantially, as well as reduce the requirements on computer memory and space.