Nuclear Safety and Security Commission

214th Meeting of Commission

Nuclear Safety and Security Commission (Chairperson Choi Won-ho, hereinafter referred to as ‘NSSC’) held its 214th meeting of the Commission on May 29, 2025 (Thurs), where two agenda items were deliberated and resolved.

[Deliberation/Resolution Item 1]

NSSC approved the draft modification of the nuclear fuel fabrication facility and the combustible waste disposal facility at the ARA Research Lab, as requested by the Korea Atomic Energy Research Institute (KAERI).

* A laboratory used for the research and production of nuclear fuel for the ARA research reactor (a multi-purpose small reactor)

The modifications include adjusting the thickness of the storage drums in the nuclear fuel storage facility at the ARA Research Lab, which had been overestimated due to an error in the radiation dose calculation program. The electrical capacity of the welding machines used in the nuclear fuel assembly process will also be increased. In addition, the fuel transfer pump for the emergency diesel generator will be replaced with a centrifugal pump instead of the previous gear pump. The NSSC also confirmed that these changes met the licensing requirements.

Regarding the combustible waste disposal facility, the incineration facility – which is no longer in operation – is planned to be demolished. Accordingly, references to the incineration facility will be removed from the permit documentation, and the title of the facility will be changed to ‘Decommissioning Waste Storage Facility,’ strengthening its seismic and fire resistance. The NSSC checked that the demolition plan was adequately established in accordance with relevant standards, and that the complement plan -- including seismic resistance evaluation, strengthened steel structure reflecting fire hazard analysis results, and additional fire protection equipment -- satisfies its related licensing standards.

[Deliberation/Resolution Item 2]

NSSC resolved to submit the ‘Budget Proposal and Fund Management Plans of 2026’ to the Ministry of Economy and Finance by the end of May, following Article 31 (Submission of Budget Requests) and 66 (Formulation of Draft Fund Management Plans).

The proposed general account expenditure for 2026 is 149.1 billion won. This includes funding for the safety management of environmental radiation -- encountered in daily life, R&D projects such as the development of verification technologies for the comprehensive safety regulation of small modular reactors, and operating expenses of affiliated organizations, including the Korea Institute of Nuclear Safety (KINS).

The net expenditure of the 2026 Nuclear Energy Fund (Nuclear Safety Regulation Account) is set at 127.2 billion won, managing overall safety regulation and infrastructure development for operating and under-construction nuclear power plants, radiation safety regulation and infrastructure, and surveys on the health effects of radiation.

The budget plan for 2026 will be finalized following the government budget formulation and deliberation by the National Assembly.

NPP Safety Starts with Thorough Construction Quality Management

- NSSC holds Roundtable with NPP design, manufacturing, construction companies

The Nuclear Safety and Security Commission (Chairperson Choi Wonho, hereinafter referred to as the NSSC) held a ‘Nuclear Safety Roundtable’ with companies involved in the design, manufacturing, and construction of nuclear power plants on May 28th.

This roundtable brought designers, manufacturers, and constructors together, responsible for safety-critical equipment in the construction of Shinhanul Units 3 and 4. Executives from Korea Electric Power Corporation Engineering & Construction (KEPCO E&C), Doosan Enerbility, Samshin, and other companies attended the event.

<NPP Design, Manufacturing, and Construction Companies Roundtable Overview>
󰋮 (Goal) To discuss ways to enhance safety with NPP design, manufacturing, and construction companies and gather feedback from the field
󰋮 (Date/Location) May 28 (Wed) 2025 10:00~12:20 / KEPCO E&C Headquarters (Gimcheon, Gyeongbuk)
󰋮 (Participants) About 30 people including companies for NPP design‧manufacturing‧construction, NSSC, KINS, etc.
- (Companies) KEPCO E&C – designer; BHI, Samshin, Hyosung Goodsprings, LS Cable & System – manufacturers; Doosan Enerbility, Posco Engineering and Construction, and Hyundai Engineering & Construction - Constructors
- (NSSC) Chairperson, Acting Director general of the Nuclear regulatory bureau, and Director of the Nuclear safety division, etc.
- (KINS) President, Head of Safety inspection division, Leader of Quality assurance department, etc.

At the meeting, the NSSC presented the Inspection procedures conducted during nuclear power plant construction and major cases of safety improvements. Participants shared their efforts and best practices to enhance equipment quality and construction safety. Various challenges faced in the field and suggestions for policy improvements were also discussed.

Chairperson Choi Wonho emphasized, “It is very difficult to recover from them later if issues arise during the construction phase. Therefore, a thorough quality management and safety assurance from the very beginning is of utmost importance. Please take extra care and responsibility on site to ensure safety.”

The NSSC will continue to prioritize field-oriented communication and plans to establish an effective safety regulatory system.

NSSC Starts Investigation into Loss of Power Supply Incident in Safety-class Bus at Hanul Unit 1

- Power was supplied normally to the one of two safety-class buses.

The Nuclear Safety and Security Commission (Chairperson Choi Wonho, hereinafter referred to as NSSC) received a report** from Korea Hydro and Nuclear Power (KHNP) that a circuit breaker had failed and could not supply power to a safety-class bus at the Emergency Diesel Generator*, while replacing the power transformer (power source transfer) for electric power facility maintenance at Hanul Unit 1 (located in Uljin, Gyeongbuk).

* Of the two Emergency Diesel Generators, one started up normally. However, due to a circuit breaker failure during the process of normalizing the electric power system, electricity could not be provided to a safety-class bus (May 26, 10:57 AM ~ 11:20 AM)

** KHNP made an initial verbal report around 14:15, and confirmed the incident as a reportable event at around 20:30.

Hanul Unit 1 has been under planned preventive maintenance since May 23, with the reactor shut down. Power was supplied normally to the other safety-class bus, and there was no impact on the safety of the NPP.

The NSSC will dispatch an investigation team composed of experts from the Korea Institute of Nuclear Safety (KIINS) to the site to thoroughly investigate the cause behind the incident and to conduct a detailed inspection of facility safety.

NSSC Allowed Criticality of Hanul Unit 6 During Periodic Inspection

- Overhauled reactor coolant pump and confirmed the structural integrity of the containment building

- Final safety to be confirmed through follow-up inspections, including the power ascension test after achieving criticality

The Nuclear Safety and Security Commission (Chairperson Choi Wonho, hereinafter ‘NSSC’) allowed the criticality* of Hanul Unit 6 on May 20, 2025, following periodic inspections that began on March 18, 2025.

* Criticality refers to a state in a reactor where nuclear fission chain reactions occur continuously, resulting in an equilibrium in which the number of neutrons generated equals the number of neutrons consumed.

During this periodic inspection, the NSSC conducted tests on 87 out of 97 required items prior to achieving criticality and confirmed that the reactor could safely reach this state.

During the inspection period, the NSSC oversaw the replacement of the reactor coolant pump motor, leakage testing of the pump seal injection water*, verification of the structural integrity of the containment building, and replacement of the component cooling seawater system pump supports. The NSSC confirmed that all test results met the relevant technical standards.

* Cooling water injected to prevent high-pressure coolant from leaking through gaps in the reactor coolant pump shaft

Based on the results of these inspections, the NSSC has approved Hanul Unit 6 to reach criticality. Final safety will be confirmed through ten follow-up tests, including a power ascension test.

213th Meeting of Commission

The Nuclear Safety and Security Commission (Chairperson Choi Wonho, hereinafter referred to as the “NSSC”) held the 213th Meeting of the Commission in written form on Monday, May 19, 2025, to deliberate and resolve on the “Modification of Operating License of Nuclear Facilities (draft).”

Korea Hydro and Nuclear Power (hereinafter “KHNP”) requested revisions to the licensing documents for Hanbit Units 3, 4, 5, and 6, as well as the installation of new equipment for Shinwolsong Units 1 and 2. The NSSC confirmed the safety of these changes based on the technical review conducted by the Korea Institute of Nuclear Safety (KINS).

First of all, tests were conducted once again to verify the integrity of the “Reed Switch Position Transmitter (RSPT)*” in Hanbit Units 3, 4, 5, and 6, against long-term radiation exposure and earthquakes. The results confirmed that the equipment meets the requirements for its entire service life (40 years).

* A device that detects the position of control rods, which regulate reactor output, and transmits the signals.

Furthermore, the NSSC confirmed that the installation of new equipment – which injects zinc into the reactor coolant of Shinwolsong Units 1 and 2, to reduce operators’ radiation exposure by removing radioactive materials accumulated in the reactor-related facilities – meets the regulatory requirements.

This equipment was first introduced at Hanul Unit 1 in 2010 and has since been installed in a total of 15 domestic NPPs. It validated its effects and safety, so other NPPs will adopt it in sequence.

The NSSC found that these applications for operating license modification meet the regulatory requirements under the Nuclear Safety Act and granted final approval.

NSSC Announced Results of Special Inspection of Institutes Using Notifiable Radiation Generators

- Follow-up measures implemented after the radiation exposure accident at Samsung Electronics, Kiheung Site

- On-site inspections completed for 46 institutes with radiation generators

The Nuclear Safety and Security Commission (Chairperson Choi Wonho, hereinafter ‘NSSC’) announced the results of a special inspection of institutes using notifiable radiation generators. This inspection was conducted as a follow-up measure after the radiation exposure accident that occurred on May 27th, 2024, at the Samsung Electronics Kiheung Site.

This special inspection targeted 46 institutes possessing more than 30 notifiable radiation generators and was conducted from November 2024 to March 2025. The NSSC and Korea Institute of Nuclear Safety (KINS) first required each institute to conduct a self-inspection regarding the appointment of radiation safety managers, and the operational status of interlocks* and warning lights on radiation generators. These self-inspections were then verified through on-site inspections. Interlock failure was once identified as the cause of the radiation exposure at Samsung Electronics, Kiheung Site.

* A unit system that protects operators by electronically and mechanically interlocking the main functions of devices, either to limit radiation emission or to physically restrict access of radiation operators.

The special inspection results showed that training for radiation operators and oversight of radiation safety during the maintenance of radiation generators were generally carried out appropriately by radiation safety managers. All interlocks and warning lights on all radiation generators were found to be functioning normally.

However, during the on-site inspections, it was found that two institutes were using radiation generators at locations different from those originally reported, and corrective actions were taken to update their records. In addition, at 14 institutes, partial shielding materials on radiation generators (lead curtains) installed on automated equipment lines (conveyor belts) were found to be damaged, and those institutes are requested to restore these items. The NSSC plans to impose fines in due course.

The NSSC confirmed that management practices at some institutes were not sufficient and plans to supplement standards for the handling of notifiable devices.

Moreover, the NSSC will conduct annual site investigations of notifiable institutes to continuously monitor the management of these devices, even after this special inspection.

The NSSC also conducted special inspections (from October 2024 to January 2025) of 258 institutes—including universities and research institutions subject to the Laboratory Safety Act—that use notifiable radiation generators, as well as three institutes with large accelerators. The inspection confirmed that, in most cases, radiation safety managers were properly overseeing safety management. Additionally, 23 institutes with discrepancies in their reports, such as failing to report changes in radiation safety managers were required to submit updated reports, thereby completing corrective actions.