In-Reactor Performance of an Advanced PWR Fuel, PLUS7, for OPR1000s in Korea

Abstract

An advanced Pressurized Water Reactor (PWR) Fuel, PLUS7, for Optimized Power Reactors (OPR1000s) in Korea has been developed to achieve peak rod average burnup of 72GWD/MTU, overpower margin increase of 10% with respect to a reference fuel used in the OPR1000s, fuel integrity maintenance even with 0.3 g of seismic load, zero defect against debris, and grid-to-rod fretting wear. All the mechanical and thermal hydraulic performances of PLUS7 had been verified through a wide spectrum of out-of-pile verification tests, whereas the burnup-dependent performances have been verified through in-reactor verification tests of four PLUS7 Lead Test Assemblies (LTAs) in one of the OPR1000s. During each refueling outage period, burnup-dependent parameters were measured, which include fuel assembly, fuel rod and spacer grid dimensional changes, fuel assembly bow and twist, fuel rod bow, and fuel rod oxide layer thickness. Based on the measured data, it is said that the PLUS7 fuel will maintain integrity at least up to a peak rod average burnup of 58 GWD/MTU. In addition, from the coolant activity analyses and ultrasonic tests, the PLUS7 fuel was found to be free from any fuel damage including debris-induced and grid-to-rod fretting-wear-induced fuel failures. This successful in-reactor operation of the PLUS7 LTAs has made the Korea Nuclear Fuel (KNF) initiate the supply of PLUS7 fuel on a region basis for all OPR1000s from the year 2006.