The Nuclear Safety and Security Commission allowed the restart of Saeul Nuclear Power Plant Unit 2 in Ulju, Ulsan, on Dec. 18, after it entered planned preventive maintenance at the end of September. This measure is the first case among domestic nuclear power plants where "continuous inspection," which combines inspections during operation, has been applied.
Continuous inspection is a system that departs from the existing method of completely shutting down a nuclear plant for checks and allows the status of major equipment to be verified during operation. By separating the periodic inspections that were conducted only during planned preventive maintenance into inspections during operation, the aim is to reduce downtime and identify equipment abnormalities at an early stage. Starting with Saeul Unit 2, which is currently in pilot application, it will be expanded to all domestic nuclear power plants from 2027.
From May last year to September this year, Saeul Unit 2 conducted operation inspections that included in-operation tests of major equipment such as safety-related pumps and valves and checks on the adequacy of radioactive waste treatment. In the subsequent maintenance inspection, damage to the emergency diesel generator cooling fan was found and replaced, and of the 522 stud anchors in the primary component cooling seawater system, two did not meet the standards and were reworked.
Meanwhile, the Nuclear Safety and Security Commission also approved the restart of Shin-Hanul Unit 1 in Uljin, North Gyeongsang, on the same day. Shin-Hanul Unit 1 entered a periodic inspection at the end of August and carried out the replacement of the shaft sealing device of the reactor coolant pump, pipe inspections related to a piping leakage case at Shin-Hanul Unit 2, and replacement of safety-grade uninterruptible power supply equipment. In addition, as a result of checking various items, including the severe accident response system, it was confirmed that all related technical standards were met.
Meanwhile, due to differences in operation and maintenance methods by plant, there was some variation in downtime, and in a simple comparison with Saeul Unit 2, the downtime of Shin-Hanul Unit 1 was found to be more than a month longer.
The Nuclear Safety and Security Commission said, "We will continue to verify safety through follow-up inspections, including power ascension tests."