Effect of power history on pellet-cladding interaction

Abstract

In this paper, the mechanical pellet-cladding interaction (PCI) is studied under various power histories. We find that the power history significantly affects possible PCI failure. PCI during the thermal transient period of power ramping occurs in such a way that crack-mouth opening increases regardless of when contact is initiated, before or during power ramping. The crack-mouth opening continues to increase further during the thermal steady state (during the power ramp). Conversely, PCI initiated either during the thermal steady-state power ramp or during the normal operation (with no power ramp) leads to decrease in crack-mouth opening. As a consequence, PCI initiated before power ramping or during the transient period of power ramping leads to high local tensile hoop stress. In contrast, PCI initiated during the thermal steady state of power ramping or during the normal operation without power ramping leads to local compressive hoop stress. In the former case, PCI failure near the crack tip might be anticipated (by either brittle failure during the transient power ramp or failure during the steady-state power ramp), whereas in the latter case, it is suppressed.