NSSC Approved Recommissioning of Kori Unit 2 following Continued Operation Approval


Completed the implementation of safety measures following the approval for continued operation

Completed the review on equipment and response strategies for accident management

Final safety confirmation through follow-up inspections, such as the power ascension test

The Nuclear Safety and Security Commission (Chairperson Choi Won-ho, hereinafter referred to as NSSC) checked the post-measures, as the continued operation of Kori Unit 2 was approved (November 13th, 2025), and its overall installation safety, and approved its criticality* on March 31st, 2026. Kori Unit 2 has conducted regular inspections since April 8th, 2023, after its design life had expired and shut down.

* A state in which a chain nuclear fission reaction continuously occurs in a reactor, resulting in the number of neutrons produced being equal to the number of neutrons that disappear, reaching an equilibrium

Kori Unit 2 is the first NPP whose continued operation was permitted after the accident management program was approved (on October 23rd, 2025). NSSC reviewed improvements, including design modifications to the accident management facilities, such as the reactor coolant external injection path, and the installation of a new facility to supply power to essential accident coping equipment. It also evaluated performance to determine whether the equipment operates as described in the accident management program, and assessed, focusing on whether accident response strategies are effective at the sites.

Moreover, 10 safety measures*, which were supposed to be completed before its recommissioning as the continued operation was approved, and cable replacement to achieve a safety margin were carried out in accordance with technical standards. Additional installation improvements following the fire risk analysis were implemented by installing fire detectors.

* Eight cases of procedure improvement, such as reinforcing the aging-related program, one case of operating environment assessment, and one case of installation improvement

In particular, Kori Unit 2 underwent a focused inspection for safety-related pumps and valves, considering that it has been shut down for a long period. It was confirmed that the test cycle and operation performance satisfied the relevant standards. The management of steam generators has been properly conducted.

Additionally, NSSC tested 94 of the 102 required items that must be completed before reaching criticality during periodic inspection, including a safety check following the replacement of a Passive Autocatalytic Recombiner (PAR)* for severe accidents and an integrity test of the steam generator tubes.

* A device to remove hydrogen that can occur during severe accidents without any additional power or operation.

NSSC approved the criticality of Kori Unit 2 based on periodic inspection results to date. Safety will be finally confirmed through follow-up tests (8), including a power ascension test. Moreover, safety equipment will be continuously reviewed even during power operation, and the emergency response system will be reinforced to ensure prompt responses to accidents and failures.