Nuclear Safety and Security Commission

Korea-Developed Pediatric Human Body Computational Model for Radiation Dose Assessment Adopted as International Standard

- Professor Kim Chanhyung from Hanyang University and his research team developed the model as a part of an NSSC Research and Development project.

- The International Commission on Radiological Protection (ICRP) officially released the model on February 19th.

A pediatric human body computational model for radiation dose assessment, developed by a domestic research team, has been adopted as an international standard. The International Commission on Radiological Protection (ICRP) selected the model created by Professor Kim Chanhyung and his team from the Nuclear Engineering Department of Hanyang University as the next-generation international standard for human body computation models. It was officially published on February 19 2025, in ICRP Publication 156.

* The ICRP is the leading international organization in radiological protection, responsible for developing standards and guidelines on radiological safety and protection and recommending them to global society.

The harm caused by radiation exposure to the human body cannot be directly measured, so computational models are used to evaluate its effects indirectly.

Previously, voxel-based models derived from computerized tomography (CT) scans were used. This method stacks small cuboids called voxels like bricks to demonstrate a human body. However, it had some limitations, such as an unnatural representation of organ surfaces and difficulties in accurately modeling very thin and small tissues.

Professor Kim’s team addressed these issues by developing a tetrahedral mesh-based computational model. This approach provides a smoother representation of organ surfaces and an accurate depiction of very thin and small tissues. It also enables precise radiation dose assessments that consider the body shape and movement of radiation operators, as it is flexible to adjust body shape and posture.

Professor Kim’s research team is currently developing a computational model for radiation dose assessment on pregnant women, building on the success of the pediatric and adult models. The team is also working on high-performance computing codes to evaluate exposure doses during accidents and emergencies. They may also be announced to the international community through ICRP Publications if successful.

This research was supported by the Nuclear Safety and Security Commission (NSSC) under its R&D project for developing Safety Regulatory Elements and Fusion Technologies. ICRP Publication 156 is available in the ‘Publications’ section of the ICRP website (www.ICRP.org).

Allowed Criticality of Saeul Unit 1 During Periodic Inspection

- Ensured the readiness of standby diesel generators and verified compliance with fire resistance standards

- Confirmed final safety through following inspections, including power uprate tests after achieving criticality

On February 24th, the Nuclear Safety and Security Commission (Chairperson Choi Wonho, hereinafter NSSC) allowed the criticality* of Saeul Unit 1, following periodic inspections that began on December 19th, 2024.

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

The NSSC conducted tests on 79 out of 91 items required before reaching its criticality during these periodic inspections, and confirmed that the reactor could safely achieve the state.

Throughout the inspection period, the NSSC verified the maintenance compliance of emergency diesel generators and pilot-operated pressure relief valves*. Additionally, it confirmed that fire protection measures in oil storage areas and the integrity of anchor bolts for the component cooling seawater system met all relevant technical standards.

* This device prevents the pressure of reactor coolants from exceeding the design limits.

The NSSC will allow Saeul Unit 1 to achieve its criticality based on the results of inspections and confirm the final safety through 12 follow-up inspections, such as a power uprate test.

University Students Sharing Nuclear Safety Policies Through Various Media


- The second ‘Nuclear Safety (and) We (Won-An-We)’, NSSC Policy Journalism Group, officially launched

- Composed of 15 undergraduate and graduate students majoring in nuclear/radiation studies, media studies, and public administration, and more

The Nuclear Safety and Security Commission (Chairperson Choi Wonho, hereinafter referred to as the NSSC) announced the launch of the second ‘Nuclear Safety (and) We (Won-An-We)’ policy journalism group. The second ‘Won-An-We’ opening ceremony was held on February 20th at the main conference room of NSSC located in Jung-gu, Seoul, marking the start of its activities.

‘Won-An-We’ is the word combination of ‘Nuclear Safety (Won-An)’ and ‘We,’ symbolizing a shared commitment to nuclear safety and responsibilities among its members of policy journalists. Following last year’s first group of 17 students majoring in nuclear and radiation studies, this year’s second group comprises 15 undergraduate and graduate students across South Korea. They will cover NSSC policies and events through various formats tailored to public understanding.

From January 15th to February 2nd, the NSSC openly recruited candidates through social media. Applications were reviewed through a rigorous selection process, including acceptance and document screening, to finalize the second ‘Won-An-We’ members.

While the first group focused on technical expertise in nuclear and radiation, the second group embraced greater diversity in regional and academic backgrounds. It is composed of undergraduate and graduate students majoring in media studies, public administration, electrical engineering, and applied biology across the continent*.

* (Participating universities) Gachon University, Gangwon University, Gyeongsang National University, Kyungpook University, Korea University, Daegu Catholic University, Sungkyunkwan University, Soonchunghyang University, Ulsan National Institute of Science and Technology (UNIST), Inje University, Chonnam National University, and Hanyang University

This second ‘Won-An-We’ plans to showcase NSSC’s policies through blog articles as well as video content. Arim Lee from the Media & Communication Department at Korea University School said, “I am honored to have this opportunity to experience and report on NSSC policies firsthand as a member of the second ‘Won-An-We.’” “As a student majoring in media studies, I aim to create video content that is easy for everyone to understand and relate to,” she added.

Meanwhile, prior to the launch of the second group, a completion ceremony was held for the first ‘Won-An-We,’ which had been active since March 2024. Two of the groups received awards from Chairperson Choi for their outstanding work. Yoo Jina, the awardee from the Department of Nuclear Engineering at Hanyang University, shared her experience, saying, “It was meaningful to interview nuclear-related issues and have a chance to reflect on them deeply. As a student studying nuclear energy, I learned that balancing technical understanding with a socially informed perspective is crucial.”

Chairperson Choi Wonho said, “Thanks to your efforts to present NSSC policies in a friendly and accessible way over the past year, we could have strengthened our connection with the public.” He encouraged the group by adding, “With greater diversity in regions and academic backgrounds, this year, I look forward to seeing the fruitful outcomes from the second ‘Won-An-We.’”

NSSC Launched Roundtable for Non-light Water Type SMR Developers

- First official meeting between regulators and developers regarding non-light water type small modular reactors

- Ongoing communication to prepare for a safety regulatory system

The Nuclear Safety and Security Commission (Chairperson Choi Wonho, hereinafter referred to as the NSSC) held a Nuclear Safety Roundtable with non-light water type* SMR developers on February 17.

* Unlike the ‘light-water reactor type,’ which uses water as a coolant for reactors, this type utilizes coolants other than water (helium, etc.).

This Roundtable marked the first official communication between the NSSC and non-light water type SMR developers. It aimed to gather diverse opinions of developers from industries and research institutes leading the development of non-light water type SMRs and incorporating these insights into regulations.

<Nuclear Safety Roundtable Summary>
󰋮(Purpose) To gather opinions to share development progress and gather opinions for regulatory preparation with non-light water type SMR developers
󰋮(Date/Place) Feb 17, 2025(Mon) 14:00~15:30 / Frasers Place Namdaemun (Jung-gu, Seoul) Namdaemun Room
󰋮(Participants) Approximately 20 attendees, including non-light water type SMR regulators
- (Regulatory Bodies) Nuclear Safety and Security Commission, Korea Institute of Nuclear Safety(KINS), Korea Institute of Nuclear Nonproliferation and Control(KINAC), Regulatory Research Management Agency for SMRs
- (Developers) Korea Atomic Energy Research Institute (KAERI), Industries (Hyundai E&C, Samsung Heavy Industries, etc.)

Globally, enhanced safety compared to light-water reactors has led to the development of 46 non-light water type SMRs, including Xe-100 (a high-temperature gas-cooled reactor) by U.S.-based X-energy. KAERI and Korean industries are actively developing various non-light water-type SMRs such as high-temperature gas-cooled reactors and molten salt reactors.

During the Roundtable, developers presented the characteristics of reactor types under development and outlined future plans. They also requested swift improvements to the current safety regulation system, which is primarily focused on large-scale light-water reactors.

Chairperson Choi emphasized, “Close communication between the regulatory bodies and developers is crucial during the process of preparing regulations for non-light water type SMRs. The NSSC will establish a system to ensure ongoing communication between regulators and developers and continue efforts in this regard.”

“We will reflect diverse opinions shared during today’s discussion on the regulatory preparation status and plans into the regulatory framework for non-light water type SMRs,” Chairperson Choi added.

NSSC Having Closer Communication with Residents Nearby NPPs


- Launched a meeting for communication with the heads of the Nuclear Safety Council from seven areas

Chairperson Choi Wonho of the Nuclear Safety and Security Commission (hereinafter referred to as the ‘NSSC’) held a meeting for communication with the heads of the Nuclear Safety Council (hereinafter referred to as the ‘Council’) from seven areas across the nation at Daejeon on February 14.

<Summary of Nuclear Safety Council>
󰋮 (Purpose) The NSSC installed and operated councils in seven areas* near NPPs to communicate more effectively with residents.
* Kori (Gijang), Saeul (Ulju), Wolsong (Gyeongju), Hanbit (Yeonggwang/Gochang), Hanul (Uljin), and Daejeon

󰋮 (Background) Article 13 (Installation of Nuclear Safety Council) of the Nuclear Safety Information Disclosure and Communication Act (implemented on July 24, 2022)
󰋮 (Composition) Regional resident representatives, government employees from local governments, local council members, experts, etc. (seven areas, about 170 people in total)

This meeting was prepared to hear fresh opinions from regions closely related to nuclear safety and strengthen communication after new presidents for each council were appointed at the end of last year.

Chairperson Choi expressed gratitude to the council for playing an important role in promoting communication and safety of regional residents and urged them to maintain steady interest in current nuclear safety issues.

“The NSSC will continue efforts to enhance trust in nuclear safety by actively communicating with various stakeholders, including members of the Nuclear Safety Council,” Chairperson Choi stated.

NSSC Appointed Non-standing Commissioner

- Professor Lee Kangkun from the Geoenvironmental Department, Seoul National University

The Nuclear Safety and Security Commission (Chairperson Choi Wonho, hereinafter NSSC) announced that Professor Lee Kangkun from Seoul National University was appointed as a non-standing commissioner on February 14, 2025.

Commissioner Lee is an expert in geology and seismology. He has served as the head of the Government Research Commission on the Pohang Earthquake, President of the Korea Society of Soil and Groundwater Environment, and President of the Korean Geological Society. Currently, he is a professor in the Geoenvironment Department at Seoul National University.

NSSC Non-standing Commissioners deliberate and resolve agenda items stipulated by the Act regarding nuclear safety. The term lasts for 3 years.

* Article 12 of the Act on the Establishment and Operation of the Nuclear Safety and Security Commission (Matters subject to Deliberation and Resolution by the Commission)

The NSSC consists of a total of 9 Commissioners including 2 standing commissioners (Chairperson and Secretary General) and 7 non-standing commissioners (3 recommended by the Chairperson and 4 recommended by the National Assembly), according to the Act on the Establishment and Operation of the Nuclear Safety and Security Commission.