Korean RPV Surveillance Programs

In Korea, surveillance tests of pressurized water reactor (PWR) vessels are mandatory, and six surveillance capsules are generally installed on each reactor vessel during its construction stage. Three to five capsules are tested within the original design lifetime depending on the changes in their mechanical properties. The surveillance test results indicate that all beltline materials, except the circumferential weld of Kori-1, meet the Charpy screening criteria for irradiation embrittlement. The Linde 80 flux high-copper weld was subjected to a detailed safety margin analysis using fracture mechanics testing and analysis methods. Based on the J-R and Master Curve test results, an equivalent safety margin of the Kori-1 reactor vessel was demonstrated for continued operation beyond its design lifetime. Ex-vessel neutron dosimetry (EVND) programs are conducted for the PWRs whose in-vessel surveillance capsules have all been withdrawn for testing or storage. However, in Korea, EVND programs have been implemented for all operating PWRs to complement the long intervals between in-vessel surveillance capsule tests and to improve the reliability of the surveillance program. The accuracy of neutron exposure calculations was sufficiently good for both in- and ex-vessel dosimetry systems per the requirements in U.S. Nuclear Regulatory Commission Regulatory Guide 1.190.