Kori Nuclear Power Plant Unit 2 in Gijang, Busan, which had halted operations after reaching the end of its design life, has begun procedures to restart after about three years. The Nuclear Safety and Security Commission allowed the reactor to go critical after reviewing periodic inspections conducted during the extended shutdown and subsequent safety measures.
The Nuclear Safety and Security Commission said on the 31st that it approved criticality for Unit 2 at Kori. Unit 2 has been undergoing periodic inspections since Apr. 8, 2023. Criticality refers to a state in which the number of neutrons is in equilibrium as a sustained chain reaction of nuclear fission is stably maintained inside the reactor. Once it reaches this stage, the reactor can be operated under control.
Kori Unit 2 received approval for continued operation in November last year from the Nuclear Safety and Security Commission. Since then, the Nuclear Safety and Security Commission additionally verified follow-up facility measures and the securing of safety, and based on this issued the approval to restart.
In particular, Kori Unit 2 is meaningful as the first nuclear plant to receive approval for continued operation after approval of an accident management plan. The Nuclear Safety and Security Commission said it focused on whether design changes to accident management facilities—such as external injection lines for reactor coolant—were appropriately reflected, and whether new facilities to supply power to key equipment needed for accident response were properly incorporated.
In addition, it checked performance to see whether related equipment actually operates normally under the accident management plan, and confirmed whether response strategies prepared for emergencies function effectively in the field.
It was also found that 10 safety measures that must be completed before restart following approval for continued operation were carried out in accordance with technical standards. The Nuclear Safety and Security Commission said that facility improvements based on fire risk analysis results—including cable replacement work and the installation of new fire detectors—were all completed.
Given the long suspension of operations, focused inspections were conducted on pumps and valves directly linked to safety. The management status of the steam generator was also confirmed to be at an appropriate level. In addition, safety inspections related to the replacement of passive autocatalytic hydrogen recombiners (PARs) for severe accident preparedness were carried out.
The Nuclear Safety and Security Commission said it inspected all 94 items that must be checked before criticality out of the 102 items subject to this periodic inspection, and concluded that reactor criticality could be achieved safely.
The Nuclear Safety and Security Commission said it plans to continue verifying safety through follow-up inspections, including power ascension testing. It also said that even after power operation begins, it will continuously check whether major safety equipment operates normally and will strengthen its emergency response system to enable immediate action in the event of an accident or malfunction.