Cycle Power Characteristics of the NPP Krsko Fuel

Influence of the assemblies' cycle power distribution on the grid-to-rod fretting wear is examined for the NPP Krsko fuel. Average power ratios between the loading cycles and radial burnup gradients are calculated. It is assumed that these factors could contribute to the formation of the grid-to-rod gap, which can results in the grid-to-rod fretting damages to the rod cladding. Results of the fuel assemblies with confirmed grid-to-rod fretting wear are compared with other non leaking assemblies to determine, if there is a particular pattern in the power distribution that can contribute to the grid-to-rod fretting. Although all leaking fuel assemblies were located near the core baffle and operated at relatively low power in the last cycle, no other significant correlation between the power and burnup distribution and the grid-to-rod fretting wear could be confirmed.(author).