Validation of a pin-based screening methodology for the investigation of pellet-clad interaction during load-follow operation

In this work we investigated the effect of PWR load-follow operation on fuel failure risk. PWR1, an unnamed commercial reactor which performed load-follow power maneuvers in cycle 21, was modeled using VERA-CS. The linear heat rate and coolant temperature calculated by VERA-CS during the maneuvers were used as boundary conditions for BISON fuel performance calculations. Using the maximum hoop stress as the indicator of fuel failure risk, the different load-follow power maneuvers were compared to the initial start-up ramp. In order to determine the effect load-follow operation has on the fuel failure risk, different characteristics of the maneuvers were compared, e.g the magnitude of the decrease in power, hold period, and the presence of intermediate power steps. No correlations were observed between the characteristics and the resulting maximum clad hoop stress. In order to reduce the number of fuel performance calculations required to determine the safety of subsequent load-follow power maneuver, a pin-based screening method was developed. By selecting the top 1000 fuel rods selected during the screening process, the BISON predicted limiting fuel pin for each maneuver was captured.