PCI ANALYSIS ON A VENDOR-RECOMMENDED FUEL PRECONDITIONING GUIDELINE FOR PWR FUEL RODS IN KOREA

摘要

Pellet Cladding Interaction (PCI) analysis of a vendor-recommended reactor power ramp rate has been performed for PWR fuel rods using FALCON fuel performance code. Fuel conditioning guideline, in other words, reactor startup ramp rate, was determined by a fuel vendor to mitigate the PCI leading to fuel rod failures during reactor power maneuver. Though reactor startup/restart ramp rate was established decades ago, it has not been updated while the fuel design and materials have been remarkably improved. The FALCON developed by EPRI is a computer code that models best estimate LWR fuel rod thermo mechanical performance under steady state and transient conditions. In this paper, an analytical evaluation performed to assess the technical basis for PWR startup ramp rate restrictions will be summarized. The power history used in these analyses was obtained from a nuclear design report and core follow calculations for typical PWR fuel rods in Korea. Numerous parametric studies varying threshold power and ramp rate were conducted to suggest an optimum startup ramp rate. This analysis can help nuclear utility not only to manage power maneuvering by ensuring that a stress driven by PCI doesn't exceed a threshold that could lead to fuel failures but also to provide the technical justification to propose less restrictive power ramp rate.