Nuclear Monitor #910

Greenpeace Asia

Unsuitable anchor bolts at ageing nuclear power plants in South Korea violate Nuclear Safety Act and require a decommissioning plan rather than a life extension review.

The Wolseong Nuclear Power Plant is located only 10km away from the epicenter of the magnitude 4.0 earthquake that occurred in Gyeongju on 30 November 2023.

An earthquake could result in cracks in the containment building due to the use of non seismic-certified anchor bolts and result in 7 radioactivity leaks or even a nuclear power plant accident.

The office of Representative Kim Seong-hwan of the Democratic Party of Korea held a press conference on 30 November 2023, revealing data on the use of unsuitable anchor bolts in domestic nuclear power plants. These data were submitted by an anonymous informant. According to the published data, non-seismic grade anchor bolts were installed in a total of 14 South Korean nuclear power plants**. Of these, 10 are ageing nuclear power plants for which the Korean government aims to extend their lifespan in the near future.

Korea is not an earthquake-safe zone. The epicentre of the magnitude 4.0 earthquake that occurred on the 30 November is only 10 km away from the Wolseong Nuclear Power Plant. An investigation by the Ministry of Public Administration and Security on active faults in the southeastern part of the Korean Peninsula published in January of this year , showed a total of seven active faults within a 32km radius of the Kori and Wolseong nuclear power plants. According to the southeastern region investigation report, three additional active faults were discovered 10-20km away from the Wolseong Nuclear Power Plant, none of which were reflected in the nuclear power plant’s seismic design. Professor Son Moon of Pusan National University, determined that the maximum earthquake magnitude of these faults is estimated to be able to be as large as between 6.5 and 7.0 . It was revealed that key safety components that ensure nuclear power plant safety did not have earthquake-resistant performance, nor did they meet design standards.

Anchor bolts are mechanical devices that are embedded in the concrete floor and walls of a nuclear power plant to secure facilities. 1) They must be made of a material required by the standards specified in the design, and 2) They must be uniform and not too short or longer than the length required in the design. 3) Design and construction must be consistent. In particular, safety-related facilities in nuclear power plants must be constructed with anchor bolts in accordance with legal design standards, and if the above construction requirements are not met, this is ground for suspension of operation or cancellation of the operating permit due to non-compliance with the design standards.

Anchor bolts installed in safety-related facilities require the so-called Q grade with verified seismic performance according to the Rules on technical standards for nuclear reactor facilities, etc. (hereinafter referred to as technical standards rules) Article 2, Paragraph 5, “Structures and systems important to safety”. Grade Q is the highest grade in the nuclear power rating scheme.

The first issue addressed in the reported data is the problem of non-seismic-grade anchor bolts installed at the pressure boundary of the containment building of Wolseong Units 1, 2, 3, and 4.

The containment building is the last barrier to prevent radioactive materials from leaking into the environment in the event of a nuclear power plant accident. Therefore, devices in the containment building must be constructed in accordance with the design standards, using anchor bolts whose seismic performance has been verified in accordance with legal standards. This is to withstand the pressure during an earthquake without causing damage to the equipment in the containment building. A review of the actual measurement data of 279 of the total 353 devices in the Wolseong Unit 3 containment building, revealed that approximately 1,300 anchor bolts installed are NSQ grade, that is, non-seismic grade. Since the entire Wolseong Nuclear Power Plant was constructed with the same design, it is likely that the remaining Wolseong Units 1, 2, and 4 containment buildings will face a similar situation.

The anonymous informant pointed out that non-seismic-grade anchor bolts do not have the ability to protect sufficiently against 8 earthquakes. They cannot withstand the load of shaking during an earthquake and that can result in damage such as cracks, protrusions, and other damage to the construction. This is of high concern, because the location where non-seismic-grade anchor bolts are currently installed is the pressure boundary of the containment building (floor, wall, dome), and in case their number exceeds 1,000, this could result large-scale cracks in the containment building. When an earthquake occurs, and equipment with non-seismic-grade anchor bolts is damaged and the reactor cannot be stopped safely, a Loss of Coolant Accident (LOCA) could occur, in which primary coolant pipes rupture, resulting in overheating and overpressure in the reactor. This could result in a nuclear power plant accident, in which a substantive amount of radioactive substances could spread through cracks in the containment building over the Korean Peninsula, including Gyeongju and Ulsan.

The installation of non-seismic-grade anchor bolts in a containment building that is a safety-grade facility according to the technical standards rules [Regulations on safety grades and specifications for nuclear reactor facilities] is in breach with nuclear power plant operation in accordance with Article 21 of the Nuclear Safety Act. Such a clear violation of the law should result in suspension of operation or cancellation of the operation license.

The second issue covered in the reported data is that inappropriate anchor bolts were installed in safety-related equipment of 13 domestic nuclear power plants.

According to the data revealed at the press conference at the National Assembly, there are a total of 1,830 safety-related devices in the 13 operational nuclear power plants in Korea, and the number of anchor bolts is approximately 12,000. Among these, there are about 1,000 anchor bolts that do not meet the anchor length required in the design.

In addition, since these devices all fall under safety classification, the anchor bolt material used and required by the design has to be in accordance with legal standards. However, it was alleged that there are approximately 3,300 anchors of unconfirmed material. In particular, since safety-related devices carry a large load, high-strength anchor bolts (A449, A325) should be used, while the data allege that approximately 7,074 low-strength anchor bolts (A307, A36) were installed. The plant operator, Korea Hydro & Nuclear Power, should evaluate these data, the used material and operability, and it must be investigated whether unsuitable anchor material has been used.

The Korean Nuclear Safety and Security Commission (NSSC) and Korea Hydro & Nuclear Power (KHNP) have always maintained the position that ‘there is no problem with safety’ in respect to various allegations such as corruption at nuclear power plant parts, counterfeit reports, and containment building voids that have been disclosed through reports over the past 10 years. However, this anchor bolt problem is on a different level. To illustrate this, Shin Hanul Unit 2, which began test operation last September, had to replace all anchor bolts that did not meet the permit standards. The problem is that in the case of an operating nuclear power plant, chances for additional construction or re-construction of anchor bolts are very limited because of interference with other facilities, and in particular, re construction of the containment building will not be possible. The current anchor bolt problem furthermore does not meet life extension screening criteria.

KHNP’s failure to discover, report, and disclose nonconformities that did not meet design standards is a violation of the Nuclear Safety Act.

Anchor bolts that do not meet the design standards installed in all the containment buildings of the Wolseong Nuclear Power 9 Plant and in the 13 units of other operational nuclear power plants require corrective action in accordance with Article 83 of the Technical Standards Rules. Article 15-3 of the Nuclear Safety Act stipulates KHNP’s obligation to report nonconformities, and the level of punishment for failure to report, or false reporting in accordance with Article 117, Paragraph 7 is also specified.

According to the report, the Korea Institute of Nuclear Safety (KINS) and the Nuclear Safety and Security Commission became aware of the difference between anchor bolt construction and design standards as early as 2015. All reported data were created in 2017 and 2018, but the Nuclear Safety and Security Commission started a related audit only in 2021. KHNP furthermore should post nonconformities on the Open Nuclear Power Plant Operation Information website. However, the position on the two issues above is not yet public. No corrective action or improvement has been taken for nonconformities to date.

The Nuclear Safety and Security Commission completed a specific audit related to radioactive material leakage and anchor bolts from the Wolseong Nuclear Power Plant’s spent nuclear fuel storage tank and waste resin storage tank in January 2023, but has not yet disclosed the results. The Nuclear Safety and Security Commission can order corrective action in accordance with Article 98 of the Nuclear Safety Act, is obliged to have KHNP report and disclose nonconformities to the public and has the obligation to determine whether cancellation or suspension of the operating license is warranted in accordance with Article 24 of the Nuclear Safety Act, and take action. It is alleged that the Nuclear Safety and Security Commission has not taken any regulatory action as mentioned above even though it was aware of the problems several years ago. If this is confirmed to be intentional, it would constitute a crime of negligence of duty under the Criminal Act (Article 122). If Korea’s nuclear power plant monopoly operators and regulatory agencies indeed were hiding the fact that about 4,000 anchor bolts without earthquake resistance were installed in an ageing nuclear power plant containment building in an area where large-scale earthquakes can occur, the people involved and responsible should be punished appropriately.

Greenpeace East Asia campaigner Mari Chang said, “The problem of inadequate anchor bolts in 14 domestic nuclear power plants as well as the leakage of radioactive materials from the Wolseong Nuclear Power Plant is conclusive evidence of disastrous failure and a moral hazard to the Korean nuclear regulatory agency and nuclear power plant operators,” adding, “It does not meet the operating permit standards.” “For ageing nuclear power plants, the goal should be safe decommissioning, not life extension,” she pointed out. She added, “We will further review these violations of the Nuclear Safety Act and the Criminal Act and report our findings to citizens, nuclear power plant regulators, and Korea Hydro & Nuclear Power.”

**A total of 14 ageing nuclear power plants where non-conforming anchor bolts were discovered. •Installation of non-seismic-grade anchors in containment buildings: Wolseong Units 1, 2, 3, and 4 •13 operational nuclear power plants: Wolseong Units 2, 3, and 4, Kori Units 3 and 4, Hanbit Units 1, 2, 3, and 4, and Hanul Units 1, 2, 3, and 4.