Supplemental surveillance capsule application for the optimized power reactor, OPR1000, in Korea

Abstract

In Korea, the pressurized water reactor (PWR) is the most common nuclear power plant. Twenty-four PWRs are operating commercially or are under construction. According to the public requirements of the reactor pressure vessel (RPV) surveillance program, all PWR plants have surveillance capsules. One type of PWR, the OPR1000 nuclear power plant has a design life of 40 years. Before the plant began operation, six surveillance capsules were installed at the OPR1000 RPV inner wall in the downcomer region to obtain more accelerated embrittlement characteristics of the RPV material. However, the lead factor defined as the ratio of the fast (E > 1.0 MeV) neutron flux at the surveillance capsule to the fast neutron flux at the RPV peak fluence location had been estimated at about 1.3 for OPR1000 plants. Therefore, obtaining high-dose irradiation embrittlement data for life extension is difficult. Supplemental surveillance capsules were fabricated and installed at the Westinghouse plant, which has a relatively high lead factor to overcome the small lead factors of the OPR1000. This paper discusses the fabrication and installation of supplemental surveillance capsules and the expected withdrawal schedule based on neutron transport calculations and dosimetry evaluations. As a result, 60 years of RPV embrittlement data for OPR1000 are expected to be obtained if the supplemental capsule is irradiated at the Westinghouse capsule holder for 7 years approximately.