Nuclear Safety and Security Commission

NSSC Approved Criticality of Shinhanul Unit 1 During Periodic Inspection

The NSSC allowed the criticality of Shinhanul Unit 1 during the periodic inspection

- Satisfied the technical standards on major tests such as the integrated leakage rate test of

containment building

- Finally , the safety was confirmed through follow up tests such as a power uprate test.

On April 17th , the Nuclear Safety and Security Commission (Chairperson Yoo Guk hee, in short NSSC hereafter) allowed the criticality* of the Shinhanul Unit 1 which had been undergoing a periodic inspection since January 5th, 2024.

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

The NSSC checked the result of 86 out of 97 test items to be carried out before the reactor reached its criticality. Then, it confirmed that it can safely reach the criticality.

The NSSC identified the cause* of why the reactor automatically tripped on January 2nd, 2024, and reviewed whether the preventive measures against reoccurrence** were appropriate during the periodic inspection.

* A maintenance man accidentally operated an output interrupter, mistaking it for a status light, while the output interrupter's circuit produce d current to exciters was installed . It led turbines/ generators to stop their operation, and the accumulated xenon caused the reactor to shut .

** The Korea Hydro and Nuclear Power Co., Ltd. (KHNP) introduced preventive measures against against reoccurrence such as maintaining the circuit of output interrupter, improving equipment to prevent human errors, and others.

Major tests confirmed that the result satisfied the related technical standards. The tests include the integrated leakage rate test of containment building s and checks on fire protection and the conditions of safety related equipment and pumps.

The NSSC will allow the criticality of Shinhanul Unit 1 based on the results of the periodic inspection and finally confirm its safety through follow up tests (11 tests) such as a power uprate test.

NSSC Approved Resumption of Hanul Unit 6

The Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter referred to as the ‘NSSC’) completed the inspection of Hanul Unit 6 and allowed its resumption on April 15th. Hanul Unit 6 was automatically tripped on April 1st due to the low water level of the steam generators.

The inspection confirmed that it was due to the damage to signal lines that control the rotational speed of main feed water pumps in steam generators, resulting in reduced flow to steam generators.

The Korea Hydro and Nuclear Power Co., Ltd. (KHNP) completed fixing the signal lines and came up with preventive measures such as multiplexing the speed control of main feed water pumps.

The NSSC reviewed how appropriate the KHNP’s maintenance and preventive measures are and will further confirm the safety through a power ascension test and other methods.

NSSC Checked on Safety Accident Readiness of Nuclear Facilities

The NSSC checked the preparedness against safety accidents in nuclear facilities.

- Held a meeting to monitor issues related to safety, asking for the prevention of safety accidents such as fires that break out during spring seasons -

On the 3rd, chairperson Yoo Guk-hee from the Nuclear Safety and Security (‘NSSC’ in short hereafter) launched a meeting to check safety issues such as fires in nuclear facilities.

The meeting was online, and 5 site offices (Kori, Wolsong, Hanbit, Hanul, and Daejeon), the Korea Institute of Nuclear Safety (KINS), and the Korea Hydro and Nuclear Power Co., Ltd. (KHNP) participated. The fire safety results of nuclear facilities, preparedness, and prevention against safety accidents were shared at the meeting.

At the meeting, chairperson Yoo Guk-hee said, “Please carefully monitor and prepare for fires since they can affect the multiple systems of facilities. Institutes should check the sites cautiously.” 

NSSC Launched Investigation on Automatic Trip of Hanul Unit 6

The NSSC started to investigate the automatic trip of Hanul Unit 6.

The Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, ‘NSSC’ in short hereafter) received a report from the Korea Hydro and Nuclear Power (KHNP) that Hanul Unit 6 automatically tripped at 03:20 am on April 1st.

It was confirmed that Hanul Unit 6 is currently in a stable state, and there are no unusual indications from radiation monitors on the radiation levels inside and outside the site.

The Hanul site office of the NSSC has been inspecting the site's safety and will dispatch experts from the Korea Institute of Nuclear Safety (KINS) to conduct a detailed investigation of the event.

Competition for New Projects to Preemptively Prepare SMR Regulatory Framework

The NSSC held the competition to prepare the SMR regulatory framework in advance.

- 9 projects in the nuclear safety and control area, totaling a scale of 3.8 billion won.

- A presentation on new projects is planned for researchers on April 3rd.

The Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter ‘NSSC’) and Small Module Reactor Regulatory Research Promotion Team (Team leader Kim In-gu, in short, ‘Promotion Team’ hereafter) will host a competition for new projects of 2024 for 31 days from March 27th (Wednesday) to April 26th (Friday).

The project* 「technology development based on safety regulations for small-and-medium-sized nuclear reactors」 is to prepare a regulatory framework in advance for Small Modular Reactor (SMR) such as innovative SMR (i-SMR)**, checking its safety.

* This project has been implemented since 2022 to maintain the regulatory framework and develop its own regulatory technologies for the license reviews of small-and-medium-sized nuclear reactors (project period: 2022~2028).

** The relevant technologies are under development and led by the Ministry of Science and ICT and the Ministry of Trade, Industry, and Energy. The standard design approval for i-SMR will be applied to the NSSC around 2026.

The NSSC will gear up regulation requirements and verification technologies for the SMR by launching multiple new projects this year. In particular, it will conduct research effectively by integrating and interlinking research projects that proceed with ongoing planning and management while centering around the promotion team, an SMR regulatory research control tower.

New projects consist of 9 research topics, totaling 3.8 billion won. Those topics consider the design characteristics of SMR, such as an entirely passive safety system that can maintain the functions of all safety equipment without electric power for safety class and the reactivity control of a reactor core that does not use boric acid. They also include regulatory issues requiring additional safety checks because SMRs differ from large nuclear power plants.

New projects in 2024

ㅇ (Safety/7 items) ▲ Develop the regulation-based technologies to assess the safety class of structure·system·component ▲Create regulation-based technologies to evaluate system safety ▲ Design regulatory-verification-based technologies on accident analysis and nuclear core design ▲ Build regulation-based technologies which estimate risks ▲ Develop regulation-based technologies to assess the safety of integrated operation of multiple modules ▲ Create regulation-based technologies in alternate protection system and I&C ▲ Establish the regulatory basement for analyzing foreign reactor types with specific inspection guides and for international harmonization

ㅇ (Control/2 items) ▲ Research concept design and application on safeguards technologies ▲ Study examples and evaluation technologies for safety·security-related cyber security

The contest for new projects will be held for about a month, from March 27th, 2024, to April 26th, 2024. Any researcher can apply to this contest if one who belongs to the relevant industries, academics, and research institutes holds the specific qualifications*. Researchers will get down to their proposed research this May after agreements.

* Institutions and associations defined by the National Research and Development Innovation Act and Basic Research Promotion Act (Refer to application guide for new projects).

Moreover, a presentation at the Daejeon Convention Center (DCC) will be at 1 PM on April 3rd (Wednesday). It will let researchers fully understand the project called 「Technology Development based on the safety regulation regarding small-and-medium-sized nuclear reactors」 and plan projects with high performance on regulations.

The presentation will introduce the result of the research that the project requires, the project’s characteristics and systems, including the connection between projects and their regular plans, ongoing projects (verification research project), technical overview and request for proposal on new projects, method to build R&D plan, etc.

Technical overview, request for proposal, application form, and presentation description per project can be found on the websites of the Nuclear Safety and Security Commission (www.nssc.go.kr) and Korea Foundation of Nuclear Safety (www.kofons.or.kr).

Promotion team leader Kim In-gu emphasized, “The role of regulatory research is very crucial to prepare a scientific and technological basis to check the safety of new reactor type such as i-SMR.” He also added, “I would like to encourage the active interest and participation of researchers with appropriate research capacities like university degrees and technological powers when contesting for new projects.”

NSSC Launched Investigation on Automatic Trip of Wolsong Unit 3

The NSSC started to investigate the automatic trip of Wolsong Unit 3.

The Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter referred to as the ‘NSSC’) received a report from the Korea Hydro and Nuclear Power (KHNP) that Wolsong Unit 3 automatically tripped at 12:09 pm on March 19th.

It was reported that the Wolsong Unit 3 automatically tripped because the fire at the electric power system damaged the output interrupters, triggering the automatic trip of the Wolsong Unit 3.

It was confirmed that the Wolsong Unit 3 is currently in a stable state, and there are no unusual indications in the radiation levels inside and outside the site, according to radiation monitors.

The Wolsong site office of the NSSC has been inspecting the safety of the site immediately after the event (at 12:22 pm) and dispatched experts from the Korea Institute of Nuclear Safety (KINS) for a detailed investigation of the event.