Korea Hydro & Nuclear Power (KHNP) has halted operations at unit 4 of the Kori nuclear facility as it awaits a government ruling on extending the service life of reactors past 40 years, World Nuclear News reports. Units 2 and 3 had previously been taken offline after reaching that threshold.

Unit 4's operational permit ended on August 6. The 1001 MWe pressurised water reactor, active since April 1986, had achieved five uninterrupted operational cycles—totalling 2,059 days—before its licence expired. Over four decades, it supplied around 277.3bn kilowatt-hours, enough to meet the electricity needs of Busan residents for roughly 12.7 years.

KHNP has applied to continue unit 4’s operations, citing the reactor’s solid safety and technology track record. A safety review was submitted to the Nuclear Safety and Security Commission (NSSC) in September 2022, followed by a completed public consultation on its environmental impact in July 2023. The formal request to alter the unit’s operating status was filed that November.

Plant Director Lee Sang-wook stressed the importance of continuing reactor operations to ensure energy security and meet climate targets, pledging strict safety standards and facility upgrades.

The South Korean government is evaluating the option of allowing nuclear units to run for an extra decade beyond their original design life, as permitted under national regulations.

KHNP previously deactivated unit 2 in April 2023 and unit 3 in September 2024. Unit 1, shut permanently in 2017, marked the country’s first reactor to begin decommissioning. Its dismantling was approved by regulators in June 2025.