PCI Risk Assessment Model

The main objective of the reported study was developing a method for predicting PCI failure risk in PWR fuel during Condition 2 transients that would strike a balance between simplicity and accuracy, allow for straightforward implementation within a transient analysis methodology or core monitoring system, and include treatment of the most important PCI factors. The developed method has the following features: 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, replaces a bounding method with a best estimate one. It allows calculating failure risk for a given ramp power or establishing a ramp power corresponding to a certain failure probability, when relevant uncertainties are considered, provides for accuracy comparable to a fuel performance code in calculating PCI failure risk in ramp tests representative of Condition 2 transients, offers a way to infer the safe threshold from ramp test data.