Nuclear Safety and Security Commission

The 179th Meeting of the Commission Was Held

The Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter referred to as the "NSSC") held the 179th meeting of the Commission on July 13 (Thursday), 2023, where the commissioners deliberated and resolved three agenda items. 

Regarding the first item on the agenda for deliberation and resolution, the commissioners passed the「bill to modify the operating license of nuclear facilities」, applied by Korea Hydro & Nuclear Power (KHNP). This bill is about ❶ permission for the modification of the operating license for Wolsong Units 2, 3, and 4 to reflect the analysis results of accidents performed again considering the aging of equipment such as an expansion of the pressure tubes; ❷ permission for the modification of the operating license for Kori Units 3 and 4 to add the repair method of the penetration of the lower head of the reactor.

Regarding the second item on the agenda for deliberation and resolution, the commissioners passed the 「Reivew of the Second Periodic Safety Review (PSR) Report of Hanbit Units 1 and 2」, after amending some parts, to decide on safety improvement items driven from the second PSR report of Hanbit Units 1 and 2 submitted by the KHNP.

Regarding the third item on the agenda for deliberation and resolution, the commissioners adjusted and passed the revised notice of 「General Acceptance Criteria for Low- and Intermediate-Level Radioactive Waste」 on the condition that they will amend some parts of the notice for safe and rational management of radioactive mixed waste such as clarifying the definitions of radioactive mixed waste and non-radioactive harmful substances and stipulating detailed management guidelines for non-radioactive harmful substances. 

NSSC Approved Criticality of Saeul Unit 1 During Periodic Inspection and to Conduct Power Ascension and Other Remaining Tests

On July 13, the Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter referred to as the "NSSC") allowed the criticality* of the Saeul Unit 1 after periodic inspection since April 16, 2023.

* Criticality means to make nuclear fissions in the reactor occur continuously, resulting in the state where the generated neutrons are equal to the extinct neutrons, and therefore, the number of neutrons is in equilibrium.

The NSSC checked the result of 85 test items out of 97 to be carried out before the reactor reaches its criticality and confirmed that the reactor can safely reach its criticality.

The main findings and results of this periodic inspection are as follows.

It was confirmed that the adhesive anchor bolts used in the travelling band screens of Saeul Unit 1 to remove debris from seawater intakes were certified under the European Technical Approval Guidelines, not the required technical standard as was published in February by the NSSC. *

* Anchor bolts in non-conformity with technical standards were found in travelling band screens at nuclear power plants (NSSC released the news on February 21, 2023)

-  The field tests confirmed that the integrity and performance of the anchor bolts were satisfactory. In addition, after comprehensively evaluating the likelihood of failure and safety function maintenance of the travelling band screening facilities, it was checked that the nuclear power plant can be operated for at least one cycle.

※ The adhesive anchor bolts were required to meet the technical standards until the next planned overhaul in February 2023.

The damage (cracks) was caused due to the incorrect welding at the attached area of the cooling equipment (the cooling fan) of the generator while conducting the performance test (running 24 hours) for the emergency diesel generator (1 out of 2 in total), which is a part of the periodic inspection.

The damaged equipment was replaced with the new one and its integrity was checked through the performance test.

※ The cooling fan will be checked regularly in every periodic inspection in the future for cracks.

The NSSC will allow the criticality of Saeul Unit 1, based on the results of the periodic inspections so far, and will finally confirm its safety through follow-up tests (12 tests) such as a power uprate test.

NSSC Began Investigation into Automatic Activation of Auxiliary Water Pump at Kori Unit 3

The Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter referred to as the "NSSC") was notified by the Korea Hydro and Nuclear Power (hereinafter referred to as the "KHNP”) that the auxiliary water pump* at Kori Unit 3 was automatically activated at 09:55 a.m while increasing the power of the reactor** for power uprate test as part of the periodic inspection of Kori Unit 3.

* The Auxiliary Feed Water Pump is safety equipment that provides water to steam generators when main feedwater pumps break down.

** After criticality, Kori Unit 3 has been maintaining about 14% reactor power when the event occurred on June 6 (Thur).

The NSSC is figuring out the initial situations through the site office established at the nuclear power site and dispatched experts from the Korea Institute of Nuclear Safety (KINS) for investigation as the above matter falls under the category of incidents that must be reported to the NSSC according to its regulations.

It was confirmed that there are no special issues related to radiation in and outside of the nuclear power plant due to the incident.

NSSC Approved Criticality of Kori Unit 3 During Periodic Inspection and to Conduct Power Ascension and Other Remaining Tests

On July 6, the Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter referred to as the "NSSC") allowed the criticality* of Kori Unit 3 after periodic inspections started from March 28, 2023.

* Criticality means to make nuclear fissions in the reactor occur continuously, resulting in the state where the generated neutrons are equal to the extinct neutrons, and therefore, the number of neutrons is in equilibrium.

The NSSC confirmed that the criticality of the nuclear reactor can be safely achieved as a result of inspecting 79 items out of 89 items to be performed before criticality during the periodic inspection.

The followings are the primary discoveries and outcomes from the periodic inspections.

It was confirmed that localized corrosion damage (precipitation of boric acid of 1g) of the guide tubes (two out of fifty in total), through which the measurement equipment moves for the purpose of the internal monitoring of the reactor, was appropriately repaired, meeting the required technical standards.

- The cause of damage was due to the reaction between the coolant and the small number of foreign substances inside the stainless steel used for the guide pipes and the safety will be checked through continuous management such as the inspection of the guide pipes and the internal cleaning work at every future periodic inspection. 

Then, it was also confirmed that the non-destructive inspection of the tubes of the steam generators was properly performed, and one foreign substance (welding slag) found during the internal inspection of the steam generator was removed. 

In addition, regarding the automatic trip of Kori Unit 3* that occurred in December, 2022, the safety of the replaced cables was reconfirmed (partial discharge testing of cables, etc) as no defection was found and met the required standards of electricity.

* Kori Unt 3 automatically tripped as a ground fault had occurred at the connection of the generator excitation transformer cable. (December 22, 2022)

Furthermore, the NSSC checked its’s recent modification approvals*: the modification of the air conditioning equipment in the main control room and the replacement of the speed indication system being employed in the turbine-driven auxiliary feed water, etc. The agency confirmed that they were all properly done.

* Operating license modification to change the method of the core thermocouple sealing devices (at the 167th Meeting of the Commission on November 30, 2022), operating license modification to change the air conditioning equipment in main control room (at the 174h Meeting of the Commission on April 13, 2023), and operating license modification to upgrade of the speed indication system being employed in the turbine-driven auxiliary feed water (at the 178th Meeting of the Commission on June 8, 2023)

The NSSC will allow the criticality of Kori Unit 3, based on the results of the periodic inspections so far, and will finally confirm the safety through follow-up tests (10 tests) such as a power uprate test.

NSSC to Investigate the Reactor Coolant Leakage at Hanbit Unit 5

The Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter referred to as the “NSSC”) was reported by the Korea Hydro Nuclear Power that there was a leakage of the reactor coolant in the safety injection line in reactor containment buildings at Hanbit Unit 5 during the planned overhaul.

At the moment, the regional site office is investigating the early onset of the situation and since the above matter fall under the category of incidents that must be reported to the NSSC according to its regulations, experts from the Korea Institute of Nuclear Safety will be dispatched to investigate the cause of the leakage.

So far, it was confirmed that Hanbit Unit 5 has no special issues such as radiation leakage to the outside.

NSSC hosted “The 2023 Forum for Radiation Safety Managers” for the First Half of the Year

- About 150 radiation safety managers across the country attended the forum and shared information

- Pyeongtaek Campus of Samsung Electronics presented the best practices for hiring safety managers

- The forum serves as a window for information exchanges on a regular basis through discussions in each field and local meetings

The Nuclear Safety and Security Commission(Chairperson Yoo Guk-hee, hereinafter referred to as the “NSSC”) held the 2023 Conference for Radiation Safety Managers for the first half of the year at Courtyard Seoul Namdaemun on June 27 (Tuesday) at 14:00.

Radiation Safety Managers conduct safety management at the working site of radiation using institutions to prevent radiation workers from having radiation-incurred harm, including exposure to radiation at the working site, and contribute to the safety culture taking root.

About 150 radiation safety managers from all over the country participated in this conference online and offline, sharing useful information on field practice through various programs, such as a presentation on the best practices for safety management and where to place main focus of regulation and what is the future direction, as well as a panel discussion on the governance of radiation safety.In particular, the Pyeongtaek Campus of Samsung Electronics received a big round of applause by presenting its best practices of hiring safety managers who have the supervisors' license for radioactive isotope handling (SRI license) even though the company has reported the use of radiation and the cases where radiation devices are safely used through its own systematic management system.

In a video containing a congratulatory speech, Lim Seung-cheol, Secretary General of the NSSC, said, “The NSSC will put radiation safety at its top priority. However,we will listen to the voices of radiation safety managers working on-site to lift up unnecessary regulations.

Radiation Safety Manager Forum has sessions for each field, such as industry, medical care, and radiographic testing as well as local meetings and serve as a window for information exchange to periodically share practical experiences and safety management information among radiation safety managers.