Nuclear Safety and Security Commission

Chairperson Yoo Attended Virtual Meeting with Heads of Foreign Nuclear Regulatory Agencies

Yoo Guk-hee, Chairperson of the Nuclear Safety and Security Commission virtually attended the International Nuclear Regulators Association (INRA) for two days from May 3 to 4, and discussed measures to strengthen nuclear and radiation safety regulations with the heads of foreign nuclear regulatory agencies of nine major nuclear countries.

<Outline of the International Nuclear Regulators Association (INRA)>

◈ Name : INRA (International Nuclear Regulators Association)

◈ Members : Nine major nuclear countries (Korea, US, Canada, UK, Japan, Germany, France, Sweden and Spain)

◈ Purpose : Heads of nuclear regulatory agencies share regulatory experience in each country and discuss regulatory policies and international cooperation to strengthen nuclear safety

◈ From the latter half of 2021 to the first half of 2022, INRA is chaired by Japan

※ Each member country takes chairmanship for one year by turn and Korea took the chairmanship in 2009 and 2018.

At this meeting, the heads of nuclear regulatory agencies shared the situations and policies related to nuclear energy and discussed the issues that range from the contaminated water from the Fukushima nuclear power plant, challenges to nuclear safety regulation, organizational efficiency and ways to improve review meetings of the Convention on Nuclear Safety (CNS) and the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management (JC).

Chairperson Yoo introduced the 「3rd Comprehensive Plan on Nuclear Safety and Security (2022 to 2026) 」, for which the public actively participated in the establishment in the stage of policy establishment, and shared the enactment of the 「Act on Disclosure of Nuclear Safety Information and Communication」, which stipulates an expanded scope of nuclear safety information to be disclosed and holding of public hearings led by the regulator.

Chairperson Yoo said, “I plan to continuously attend the INRA meetings in order to ensure nuclear and radiation safety that satisfies the public expectations and build closer cooperative relationships with other regulatory agencies in major nuclear countries.”

NSSC Shares the Progress of the Second-phase Investigation of Tritium in the Wolsong Site and Future Plans

The civil team for the investigation on tritium in the Wolsong Nuclear Power Plant (led by Hong Seong-geol, a professor at the Department of Architecture of Seoul National University, hereinafter referred to as the “investigation team”) and the council to communicate current issues (led by Kim Ho-cheol, a commissioner of the Commission of the Nuclear Safety and Security Commission, hereinafter referred to as the “council”) announced the 「progress of the second-phase investigation on the tritium in the Wolsong Nuclear Power Plant (in the site) and future plans 」 , following the 「progress of the first-phase investigation and future plans,」 presented on September 10, 2021.

The background and result of the investigation is as below:

Regarding the tritium discovered* within the site of the Wolsong NPP, there was a necessity of objective investigation and transparent disclosure of information after the beginning of 2021 as the anxiety of the residents living near the site and general public was significant.

* In April 2019, tritium of the maximum concentration of 713,000 Bq/L was detected in the stagnant water in the manhole of the turbine gallery of the Wolsong Unit 3, and tritium of 28,200 Bq/L, in the observation well, WS-2, in May 2019.

Therefore, the Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee) formed an investigation team* for a scientific and objective investigation and a council** to deliver opinions on the overall investigation and monitor the progress.

* Comprised of 7 civil experts recommended by the academic organizations in the areas of geography, machinery, radiation, civil engineering, and etc.

** Comprised of 7 members – a non-standing commissioner of the NSSC Commission recommended by the government and 2 members each from local communities, civil organizations and nuclear fields

On March 30, 2021, the NSSC held a launching ceremony for the investigation team and the council and started a full investigation.

The investigation team collected all the suspicions and issues raised by the media and etc., and established and disclosed the investigation plan* after discussing and reflecting matters brought up by the council.

* (Investigation areas) ① Integrity of the nuclear spent fuel pool and water barrier structures, and whether there has been a gamma nuclide leak, ② Cause of the tritium of high concentrations in the turbine gallery, ③ Cause of gamma nuclide detection in the sediment on the floor of the turbine gallery of the Unit 1, ④ Analysis of the trends of the measured values from the observation wells in the site and cause, ⑤ Whether there has been a leak into the outside environment

The investigation team has been conducting an investigation by each area through document review, on-site inspection and review meetings. In the meantime, the council has been observing the on-site inspections and monitoring the activities of the investigation team.

※ (Activities done until the presentation of the first phase investigation) 12 meetings of the investigation team & 8 meetings of the council (including 3 joint meetings); documents requested 339 times; 30 on-site investigations (3 full investigations) and etc. (till September 9, 2021)

※ (Activities done until the presentation of the second phase investigation) 19 meetings of the investigation team & 10 meetings of the council (including 6 joint meetings); documents requested 69 times; 29 on-site investigations (1 full investigations) and etc. (from September 10, 2021 to April 29, 2022)

The result by each area so far is as below:

[The integrity of the spent fuel bay and cut-off structures, and whether gamma nuclides have leaked]

❶ Integrity of cut-off structures such as the walls of the spent fuel bay (SFB) and internal epoxy liners

The investigation team conducted underwater photography to check the integrity of the epoxy liners applied to the inner walls and floors of the Wolsong Units 1-4 SFB, and the deterioration conditions such as swelling and cracking of the surface of the epoxy liners at the bottom were found*.

Following the request of the NSSC, the Korea Hydro and Nuclear Power has been conducting an extended inspection on the epoxy liners at the bottom of the Units 1 to 4 (from November 2021 to October 2022)

It was confirmed that there had been leaks (from October to December, 2021)* from the slab, particularly, the parts that were repaired in 1997, on the southern side of the SFB of the Unit 1.

* After excavation in the area (in July, 2021), leakage started around October and repair of the area was completed (in December)

As a result of analyzing whether the cracks in the SFB wall were caused by expansion/contraction caused by external loads and temperature changes due to the excavation, it was judged that the possibility is low.

The cracks are thought to have occurred during the curing of the poured concrete at the time of construction, and therefore, the investigation team checked the area through coring* and found a deep crack.

* Coring is conducted to collect and inspect a part of concrete in a cylindrical shape to identify cracks in concrete

As a result of coring, it was confirmed that the water proof performance of the concrete at the time of construction was low, so there is a possibility of leakage through the concrete medium.

As repairs of existing crack only have a partial effect and leakage occurs through internal cracks, continuous leakage management* is required.

* Leakage for SFB is managed through cut-off structures such as cut-off barriers, cut-off walls, perforated pipes, water tanks, and etc.

< Structural diagram of the SFB of the Unit 1 (the area repaired in 1997 and the location of coring) >

The load applied to the rebar in the area due to the vertical crack of the SFB wall of the Unit 1 is 60% of the rebar strength, and therefore, safety is considered to be secured. Due to the internal cracks in the walls, however, the rebar was exposed to hydrogen over a long time, and it is necessary to carry out an inspection on corrosion.

It is necessary to restore the water proof function in consideration of the possibility of leakage from the SFB walls of the Unit 1, and to check the bonding of the cut sides of the cut-off barriers removed during excavation work and water proof performance

The Korea Hydro and Nuclear Power has selected a new material for cut-off barriers and is conducting a performance test to check bonding characteristics with the existing barriers, and the investigation team is checking the testing process.

❷ To estimate the amount leaked from the SFB*, a model water tank was installed on the upper part of the SFB of the Wolsong Units 1 to 4 and a simulation test to calculate the evaporation amount is being carried out ** (since March 28, 2022)

* In case of water leakage from the SFB wall, the water gathers into the SFB water tank along the perforated pipe installed on the barriers.

** When the SFB replenished amount minus evaporated amount equals leaked amount, approximate leakage can be calculated if the evaporation amount is known and the replenishment amount data is secured.

❸ Regarding the detection of gamma nuclides in the SFB water tank of the Unit 4 (in January, 2009), the records of maintenance and gamma nuclide detection were analyzed.

The concentration of gamma nuclides (Co-60) in the SFB tank was 5.15 Bq/L on average (from February 2015 to June 2019), but has not been detected since the repair of the SFB epoxy liner in June 2019.

* Cs-137 has been continuously undetected in the water collection tank, and will be continuously monitored in the future

[ Cause of the detection of highly-concentrated tritium in the turbine gallery]

The investigation team conducted a verification experiment to confirm whether the tritium concentration in one ton of stagnant water can be increased to the level of 713,000 Bq/L through the underwater transition of tritium in the air inside the turbine gallery at the Unit 3.

* Interchange and concentration changes of tritium in the air and tritium in liquid

The investigation team conducted verification experiments in the same location and environment as when the first stagnant water was discovered.

As the first preliminary experiment, the investigation team analyzed changes in tritium concentrations in 1-ton water under the turbine gallery manhole (#2) and 1L and 10L* of experimental water.

* The main test subject is tritium in the 1-ton water, but for concentration comparison according to quantity, they were additionally installed and analyzed.

This experiment was conducted to understand the underwater transition phenomenon and to gain experience for setting additional experimental conditions. The change in tritium concentration in the experimental water is as below:

※ As the tritium concentration in 1 ton of stagnant water was diluted with additional inflow due to 92.5 mm of rain (on Aug. 21, 2021) during the test period, the drainage was reinforced after the preliminary experiment was completed so that the same phenomenon would not repeat.

In the second main experiment, changes in the concentration of tritium in the 1-ton water and 1L, 5L, and 10L of the experimental water installed at the same location as the first preliminary experiment were analyzed. (Experiment was conducted from November 17, 2021 ~ April 13, 2022)

This experiment was conducted to verify the underwater transition of tritium inside the turbine gallery. The changes in the concentration of tritium in the experimental water are as below:

Through this experiment, it was confirmed that the tritium concentration in 1 ton of stagnant water exposed to air with an average concentration of 7.1 Bq/L for a long time can increase to more than 713,000 Bq/L.

To find the cause of the introduction of the water into the manhole #2 at the Unit 3, the investigation team is looking at the history of repairs of the structures and pipes around the manhole, precipitation, and water introduction.

NSSC Held Academic Conference for Radiation Safety Managers

The Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter referred to as the “NSSC”) held a launching conference for radiation safety managers* at Seoul Global Center on April 27 at 14:00.

* Radiation Safety Managers conduct safety management to prevent radiation workers from having radiation-incurred harms, including exposure to radiation, at radiation using institutions.

About 120 radiation safety managers from all over the country participated in this conference online and offline, sharing useful information on field practice, such as the current state of radiation safety regulations and best practices for safety management.

< Outline of 「Radiation Safety Manager Launching Conference」 >

￭ (Date/Venue) 2022.4.27.(Wed) 14:00 / International Conference Center, Seoul Global Center, Jongno-gu, Seoul

￭ (Hosted by) Nuclear Safety and Security Commission

￭ (Organized by) Korea Foundation of Nuclear Safety, Korea Nuclear Safety Academy

￭ (Main contents) Current status of radiation safety regulations, best practices for safety management, examples of radiation exposure reduction, etc.

In a congratulatory speech, Jang Bo-hyeon, Secretary General of the NSSC, said, “Radiation safety depends on radiation safety managers who manage radiation safety in the field. We hope that not only this conference but also a forum which will be held soon will be an opportunity to establish a radiation safety culture by sharing various examples and information.”

Radiation safety manager forum will have sessions for each field, such as industry, medical care, and radiographic testing, and serve as a window for information exchange to periodically share practical experiences and safety management information among radiation safety managers.

NSSC Start to Investigation Automatic Trip of Hanaro Research Reactor

The Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter referred to as the “NSSC”) announced that the NSSCw as briefed by the Korea Atomic Energy and Research Institution (KAERI) that its research reactor, Hanaro, had automatically tripped on April 25 at 16:42. The NSSC dispatched an investigation team to the site to investigate detailed causes.

This event reportedly happened as there had been an abnormal condition in the hydrogen pressure of cold neutron source testing facilities*, which led to trip signals.

* Equipment for decelerating using liquid hydrogen to use neutrons produced in nuclear reactors for research

Currently, the Hanaro reactor is in the stable state with normal operation of the coolant pumps, and it was confirmed that there has been no radiation effect as no warnings or abnormal signs went off at the radiation monitors.

The NSSC will look into the causes of the trip of the Hanaro reactor in detail through the investigation team and thoroughly review the plan to prevent recurrence.

The 156th Meeting of the Commission Was Held

- Bills, including the revision of the Nuclear Safety Act, were deliberated and passed. -

The Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter referred to as the NSSC) held the 156th Meeting of the Commission on April 22, 2022 to deliberate and decide on two agenda items.

As for the first agenda item, the commissioners passed the bill to modify the Nuclear Safety Act, following the request from the Ministry of Legislation for cooperation in the revision of laws and regulations to make disqualification categories in the Nuclear Safety Act more reasonable. With this amendment, no additional disqualification period will be imposed after restoration or reinstatement of a license in the case where the license or approval was revoked for the reason of legal capacity (a person under the age of 18 or under the guardianship of an adult) or bankruptcy.

※ The second agenda item, applied by the Korea Atomic Energy Research Institute (KAERI), the 「bill to permit the nuclear fuel processing business of the KAERI (Ara Research Building)」 will be re-discussed at a later meeting for further review.

As for the third agenda item, the commissioners passed the 「bill to modify the construction permit and operating license of nuclear facilities」, applied by the Koea Hydro and Nuclear Power. This will allow ➊the modification of the construction permit to change piping and instrumentation diagram of Component Cooling Water System of the Shinkori Units 5 and 6, and ➋ the operating license to change the pressure and temperature limits of the reactor coolant system of the Kori Unit 2.

NSSC Orderd Homeferry Korea to Recall “Sofa Bed”

The Nuclear Safety and Security Commission (Chairperson Yoo Guk-hee, hereinafter referred to as the “NSSC”) ordered Homeferry Korea Co., Ltd. to recall one kind of its sofa beds as it was confirmed that the product is defective under the Act on Protective Action Guidelines against Radiation in the Natural Environment.

* Model Name: Living Hip Tilt Folding Sofa Bed (Brown)

The NSSC conducted an on-site investigation and product safety evaluation of Homeferry Korea, and the results are as below:

Homeferry Korea imported three kinds of 3,841 sofa beds from China from April 2019 to September 2021 and sold 3,656 pieces.

As a result of analyzing radioactive substances contained in the products, it was confirmed that the annual dose of one kind of 1,012 products was 2.19 mSv, which was in excess of the safety standard (allowable annual dose is 1 mSv) applied to processed products under Act on Protective Action Guidelines against Radiation in the Natural Environment, and the NSSC ordered the company to recall the products.

In addition, some of these products were imported even after the enforcement of Act on Protective Action Guidelines against Radiation in the Natural Environment (July 16, 2019), which prohibits the use of raw materials* in products that are used and worn in close contact with body, and therefore it was confirmed that the regulation was also violated.

* Legal standards applicable to raw materials (exceeded radioactive concentration, 0.1Bq/g, and quantity, 100,000Bq)

Furthermore, the NSSC recommended the company to recall 2,829 products of the other 2 types, which are similar products, and Homeferry Korea is currently collecting* back all imported and sold sofa beds.

* As of the end of March of 2022, 296 out of 3,841 items have been collected

The NSSC plans to further strengthen the inspection of related products, including defective-product finding surveys, in order to eradicate cases where radioactive raw materials are used in the products that are used in close contact with body.