Nuclear Safety and Security Commission

The NSSC Approved Criticality of Kori Unit 2 During Periodic Inspection and to Conduct Power Ascension and Other Remaining Tests

- The NSSC will also approve the resumption of the Shinkori Unit 1 and 2 that had been shut down due to the typhoon “Maysak.” -

On September 28th, the Nuclear Safety and Security Commission (Chairperson Uhm Jaesik, hereinafter referred to as the "NSSC") allowed the criticality* of the Kori Unit 2, which had been undergoing a periodic inspection since February 17th.

* 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.

※ If criticality is approved, 7 remaining tests, including a core physics test, are conducted during the process of or after reaching the criticality of reactors.

During this periodic inspection, the NSSC checked the result of 89 test items to be carried out before the reactor reaches its criticality, and confirmed that the reactor can safely reach its criticality.

During this periodic inspection, the precipitation of boric acid was identified in one of the penetrations as a result of visual inspection of the lower head of the reactor, and the penetration and weld were replaced with a material highly resistant against corrosion.

Also, the recirculation pipes of auxiliary feedwater pumps which were damaged in the past have been repaired by changing the material and type of welding, and one containment pressure instrument which had been located in the non-control area was relocated into the control area.

It was confirmed as a result of non-destructive testing of the steam generator tubes that all relevant standards have been met, and foreign materials (2 tapes) detected by foreign material screening equipment were all removed.

It was also confirmed that the KHNP has completed the implementation of the measures for normal operation such as replacement of instrument transformers and support insulators, which were found to have been damaged by the typhoon “Maysak”, and removal of attached salt by cleaning.

In order to prevent salt-induced flashovers in the transformer-related facilities that were open to the outside environment, the facilities were changed into sealed facilities in the form of gas-insulated bus. It was also confirmed that the plan was to be prepared for the safe operation of the reactors under natural disaster circumstances such as preventive power cutback or shutdown.

* A flashover is a fire spark made by an instant current of electricity.

The NSSC approved the restart of the Kori Unit 2 based on the result of the periodic inspection so far and will finally confirm safety of the unit through 7 follow-up tests such as power ascension test.

Regarding the Shinkori Unit 1 and 2 which were tripped due to the typhoon “Maysak,” the NSSC plans to approve their restart on September 29th as it confirmed that the KHNP had completed identification of the cause of the reactor trip and implementation of measures for normal operation.

Investigation on Event Triggered by Typhoons Maysak and Haishen Announced

The Nuclear Safety and Security Commission (Chairperson, Uhm Jaesik, hereinafter referred to as the “NSSC”) and the Ministry of Trade, Industry and Energy (Minister Seong Yunmo, hereinafter referred to as the “MOTIE”) announced the result of the investigation on the 8 reactors – Kori Unit 1, 2, 3, 4, Shinkori Unit 1, 2, and Wolsong Unit 2, 3 – that had a problem with the off-site power system affected by the typhoons “Maysak (on September 3rd)” and “Haishen (on September 7th).”

This event occurred due to an issue in the electric transmission lines between the nuclear power plants and the external electrical substations and associated facilities. In order to clarify the cause and sequence of the off-site power loss, the NSSC and the MOTIE conducted a joint investigation that looked into even the management practices of the Korea Electric Power Corporation (hereinafter referred to as the “KEPCO”).

Outline of the event

Due to the typhoon Maysak, which landed in Busan on September 3rd, 2020, strong wind with a maximum wind speed of 32.2 m/sec blew nearby the Kori nuclear power plant (NPP), and a total of 6 reactors (Kori Unit 1, 2, 3, and 4 and Shinkori Unit 1 and 2) lost the supply of off-site power one after another at different times and their emergency diesel generators were activated. Among the reactors, 4 reactors (Kori Unit 3 and 4, and Shinkori Unit 1 and 2) that had been in normal operation were tripped.

On September 7th, 2020, strong wind with a maximum wind speed of 33.1m/sec was recorded at the Wolsong NPP site due to the typhoon “Haishen.” The turbines and generators of the Wolsong Unit 2 and 3 were tripped while the supply of off-site power was sustained. Consequently, the reactors started to operate with 60% of reactor power.

Investigation Result

At NPP stations, reactors generate heat energy which rotates turbines to generate electricity. The electricity is transmitted to outside substations through transmission facilities. At the same time, the NPP stations receive power from the external power source through transmission facilities for the operation of safety-essential facilities such as reactor coolant system.

In the case of Kori Unit 1, 2, 3, 4 and Wolsong Unit 2, 3, salt carried by the strong wind at the time of the typhoon was attached to the instrument transformers which measure electrical quantities generated from the nuclear power plants, causing flashovers*. It led to the opening of the breaker in the switchyard, which was the beginning of the event. The Kori Unit 1, 2, 3, and 4 lost the supply of off-site power and their emergency diesel generators were automatically activated.

* A flashover is a fire spark made by an instant current of electricity.

In particular, in the case of Kori Unit 3 and 4, on September 4th and 5th, the days after the typhoon passed by, the power of the standby auxiliary transformers was cut off due to flashovers caused by the salt attached to them at the time of the typhoon and the emergency diesel generators were activated.

In the case of Shinkori Unit 1 and 2, the jumper cables that transmit electricity from the nuclear power plant to the 765kV transmission tower approached near the steel tower structure due to strong wind, causing flashovers. It led to the loss of off-site power, then the reactor trips and activation of the emergency diesel generators.

On the other hand, a few cases involving salt-induced flashovers in and gust-caused falling of parts from the transmission and transformation facilities were found in the jurisdiction of the KEPCO near the nuclear power plants. However, the failure records of the facilities indicated as a result of analysis that they were irrelevant of the reactor trips.

Future plan

Unlike nuclear power plants in which transformer accessories are sealed in the form of gas-insulated bus (GIB), flashovers caused by salt occurred in transformer-related facilities that are open to the outside environment. To prevent recurrence in the future, therefore, it is planned to minimize the part exposed to the outside environment, including main transformers, standby transformers, and instrument transformers of the Kori Unit 2 to 4, the Wolsong Unit 2 to 4, and Hanbit Unit 1 and 2, by sealing the facilities.

In addition, in consideration of the range that natural disasters such as typhoon can affect, a plan will be prepared to safely operate nuclear power plants such as preventive power cutback or shutdown.

Regarding the KEPCO’s management practices, it is planned to replace insulators with salt-resistant materials and improve the safety of electric facilities by considering geographical and seasonal characteristics.

When the Korea Hydro Nuclear Power's measures for normal operation, such as replacement of damaged parts and removal of salt, are completed, the NSSC will thoroughly check the measures and, only when the measures are satisfactory, allow the resumption of the nuclear power plants. The NSSC will also continue to check the implementation status of the plan to prevent recurrence, such as preparing relevant procedures that include the transmission facility management program.

Talc (raw material for baby powder) is not a radioactive material.

On September 24th, Money Today released an article titled “800,000 tons of radioactive raw materials for baby powder imported unguarded without inspection,” and argued approximately 800,000 tons of talc, classified as an item with radioactivity above the standard value in the past, was imported and distributed in the market without inspection.

About this article, the NSSC explains:

Talcum powder is not a raw material that generally emits radiation, and so far, there has been no case of detecting the material emitting radiation in excess of the standard by air and port radiation monitors.

However, radiation from stone powder was detected at Incheon Port in 2017, and some internet portal sites show stone powder as talc powder as a result of searching, which may cause misunderstandings. As a result of the analysis, it was presumed to be monazite and that NSSC immediately ordered to return the power.

* In the data submitted by the NSSC to the National Assembly (to Congressman Cho Jeongsik), only stone powder was written in English without Korean name, and in some portal sites, stone powder is searched as talcum powder.

It is not true that experts are excluded from the planning of the third Nuclear Safety Comprehensive Plan

On September 24th, Hankook Economy released an article titled “Moon’s administration leaves the safety of nuclear power plants in the hands of laymen.” The article argued that nuclear safety cannot be handled by the general public but the administration plans to form a public panel with laymen that would decide on the grand plan for nuclear safety. It also claimed that experts led the composition of the first and second Comprehensive Plans, but they are to be excluded from the third planning.

About the article, the NSSC explains:

It is not true that experts are excluded from the process of establishing the third Comprehensive Plan.

The general public will not perform the operation or safety verification of nuclear facilities but plays a role in proposing visions and policy directions for nuclear safety through discussion.

Strategic tasks and detailed plans to make these suggestions concrete are prepared through discussion of the experts from academia, the Korea Institute of Nuclear Safety, the Korea Institute of Nuclear Non-proliferation and Control, Korea Atomic Energy Research Institute, the KHNP and etc.

In fact, measures to technically supplement the suggestions, such as “strengthening the vent system of the nuclear reactor containment vessels” which the article mentioned, will be prepared by experts through discussion during the process of establishing detailed plans.

In addition, the “citizen reporters’ group participated by students” will not participate in discussions on the establishment of the Comprehensive Plan, but will play a role in notifying the public of the planning process through social media.

The Third Nuclear Safety Comprehensive Plan (2022 to 2026) To Be Established With Direct Participation of the Public

- The NSSC begins recruiting citizens for a public panel that will provide insight on visions and policies of nuclear safety. –

On September 23rd, the Nuclear Safety and Security Commission (Chairperson, Uhm Jaesik, hereinafter referred to as the “NSSC”) and the Korea Foundation of Nuclear Safety (President Kim Hyejeong) announced that they would invite members of the public to the establishment process of the 「third Nuclear Safety Comprehensive Plan (for five years from 2022 to 2026) 」 by forming a public panel in order to implement nuclear safety policies the public envisions.

The Comprehensive Plan is the highest-level legal plan of which establishment is required by the Nuclear Safety Act. The third plan will cover 5 years from 2022, during which the NSSC will implement policies based on the plan.

The public panel will be composed of 200 people: 120 from general public, 50 from stakeholders’ groups, such as residents living in nuclear power plant areas and experts, and 30 citizen reporters.

Among 120 members from the general public who will give insight on the vision and policy directions of nuclear safety, 80 will be randomly selected in consideration of population ratios and the remaining 40 will be selected through this open recruitment process.

Anyone who holds interest in nuclear safety is eligible for application and can apply at the Nuclear Safety Public Panel Portal (http://ourplan.nssc.go.kr) from September 23rd to October 6th.

The public panel will provide insight on the vision, policy directions, and major strategic tasks in two stages.

In the first stage, 120 members from the general public will draw up the vision and policy directions of nuclear safety through discussion process by the end of November.

* Actual schedule may be changed according to the COVID-19 situations.

In the second stage, based on the vision and policy directions drawn up through discussions of 120 people, experts and stakeholders, including residents living in nuclear power plant areas and associated organizations, will go thorough discussions by each sector and finally deliver major strategic tasks by the first half of next year.

The NSSC will establish detailed plans to embody the vision and policy directions suggested by the public panel and elicit opinions about the plans from the public panel, general public and associated organizations. After the approval of the commissioners, the Comprehensive Plan will be finally set.

Chairperson Uhm Jaesik said, “Nuclear safety is closely tied with public safety, but there has been some difficulties that blocked the access of the public as nuclear is an area of technical expertise.” He also said, “The NSSC is planning to fully support the members from the public in terms of technical knowledge so that they do not have any inconveniences participating in discussions.” He lastly asked for people’s interest and participation.

From 2021, Lifetime Cumulative Radiation Doses of Radiation Workers to Be Collectively Managed

-The NSSC passed the bill to revise the “Enforcement Rules of the Nuclear Safety Act” to establish a new system for integrated and linked management of radiation dose data among ministries

- It is expected to resolve the issues of keeping the radiation dose data by each relevant ministry; reduction, omission, and loss of records; and loss and misuse of dosimeters.

- The revised act will come into force in 2021 after passing through inquiry of opinions of other related agencies, pre-announcement of legislation (on October 2020), and review by the Ministry of Government Legislation.

The Nuclear Safety and Security Commission (Chairperson, Uhm Jaesik, hereinafter referred to as the “NSSC”) discussed and passed the ｢bill to revise the “Enforcement Rules and Notice of the Nuclear Safety Act｣ at the 125th meeting of the commissioners held on the September 11th to ensure that the cumulative lifetime radiation doses of radiation workers in the medical field can be accurately and systematically managed.

The purposes of the revision is to create a legal basis for safeguarding radiation workers by integrating and sharing the data of radiation doses of radiation workers managed and kept by a few ministries according to such laws as the “Nuclear Safety Act,” the “Medical Act,” and the “Veterinarians Act,” and by managing the data on a continual basis even when a worker moves to another job.

The radiation dose data of radiation workers is a measure of the level of radiation they received during work, and is an important indicator for their health and safety that must be kept in accumulation and managed for each individual throughout one’s life. In order to protect radiation workers, the government mandated wearing personal dosimeters and mandatorily reporting doses at each work as prescribed by law, and keeps each person’s data as a national record.

However, in the medical field, radiation zones are licensed according to relevant laws, such as the ｢Nuclear Safety Act｣ and ｢Medical Act｣, according to the purpose of each zone*. If multiple laws are applied, several dosimeters must be prepared for each law and worn in turn, and the data must be separately reported to each responsible ministry.

* For example, an X-ray imaging room in hospital A is subject to the Medical Act, but an isotope treatment room in the same hospital is subject to the Nuclear Safety Act.

This has been the reason for the distortion of the data on total radiation doses due to the separate management of the data of individual employees having overlapping work, loss of previous data when a worker moves to another agency under another jurisdiction, and complaints of difficulties in using multiple dosimeters.

This revision of the Enforcement Rules is part of a plan jointly prepared by three ministries - the Nuclear Safety and Security Commission, the Ministry of Health and Welfare, and Ministry of Agriculture, Food and Rural Affairs - through several discussions and consultations to resolve these issues.

By preparing the basis for mutual recognition of radiation dose data in accordance with the laws and regulations belonging to other ministries, the total amount of individual doses can be conveniently and accurately managed with a single dosimeter, and previous records can be submitted even when retiring from an institution subject to the laws under other ministries so that the data can be managed cumulatively throughout life.

In addition, when a radiation dose of workers is detected above a certain level, the three ministries plan to keep cooperating at the working level such as launching a joint investigation.

Chairperson Uhm Jaesik said, “With this revision, it is expected to more systematically protect workers from radiation,” and “the NSSC plans to operate an efficient radiation dose management system centered on workers through continuous cooperation with other ministries and proactive administration.”

This revised bill is scheduled to go through procedures such as inquiry of opinions of related organizations and a pre-announcement of legislation in the future with the aim of being implemented in 2021, and the Ministry of Health and Welfare and Ministry of Agriculture, Food and Rural Affairs will also start revision of the regulations under each agency.

<Case 1> A worker who is subject to two or more laws at one institution

In case of simultaneous access to Area A (ex. X-ray room) subject to the Medical Act and Area B (ex. Isotope Treatment Unit) subject to the Nuclear Safety Act, each dosimeter for each area must be carried and when a worker enters another area, he or she must replace the dosimeter under the current law.

☞ It is possible that the total radiation dose of an individual is divided and recorded to two separate dosimeters, thus reduced in amount, and then reported. Or, they may wear only one dosimeter and the radiation doses reported to both agencies are added up in duplication.

<Case 2> A Worker who has moved to another job under another jurisdiction

If a worker who was working in a veterinary hospital (applied by the Veterinarians Act) moves to a medical institution subject to the Nuclear Safety Act, a new dosimeter must be worn in accordance with the Nuclear Safety Act.

☞ After leaving a previous job, only the radiation dose according to the Nuclear Safety Act is reported without past record, so the accumulated personal radiation dose is inaccurately tracked.