The Nuclear Safety and Security Commission allowed the restart of Hanul Unit 5 after completing a regular inspection.
The Nuclear Safety and Security Commission said it conducted a regular inspection of Hanul Unit 5 starting on Feb. 26 and allowed criticality on the 10th, judging that the reactor could reach criticality safely.
Criticality refers to a state in which a nuclear fission chain reaction is sustained stably inside a reactor. It is a key step required for a reactor to raise power again, and once criticality is allowed, the reactor can proceed to the restart phase.
In this regular inspection, 87 of the 97 total inspection items that must be verified before criticality were checked. The Nuclear Safety and Security Commission explained that the results confirmed Hanul Unit 5 could proceed to reactor criticality safely.
A reinspection was also conducted into cases where an instrument maintenance company violated calibration procedures identified during the inspection. Korea Hydro & Nuclear Power Co. (KHNP) rechecked the entire testing and calibration process for about 7,600 instruments, and the Nuclear Safety and Security Commission determined that this reconfirmation procedure was carried out appropriately.
In addition, some cases were found where the actual field installation did not match drawings for certain expansion anchor bolts that secure safety-grade equipment. There were 12 cases in total, including the use of a different type of anchor bolt than specified in drawings at the mounting base of the reactor building air monitor. However, the relevant technical standards were found to be met. Accordingly, follow-up actions such as replacing anchor bolts and reviewing allowable loads were taken, and the Nuclear Safety and Security Commission also verified whether those measures were carried out appropriately.
Based on the results of the regular inspection so far, the Nuclear Safety and Security Commission allowed Hanul Unit 5 to enter the restart phase. Going forward, it plans to confirm final safety through the remaining 10 follow-up tests, including a power ascension test.