Pellet-Cladding Interaction Probability Assessment Model

Abstract

The main objective of the reported study was developing a method for predicting pellet-cladding interaction (PCI) failure probability in pressurized water reactor (PWR) fuel in transient conditions that would strike a balance between simplicity and accuracy, allows for straightforward implementation within a transient analysis methodology or core monitoring system, and include treatment of the most important PCI factors. The developed best estimate method relies on readily calculated/available quantities, such as nodal burn-up, local power, average cladding temperature, and pressure differential across cladding at zero burnup, uses a power increase past gap closure as a failure criterion. The method allows for calculating failure probability for a given rate of power change or establishing a rate of power change corresponding to a certain failure probability. It also provides for accuracy comparable to a fuel performance code when calculating PCI failure probability in ramp tests and offers a way to infer a safe PCI threshold from ramp test data.