Kori Nuclear Power Plant Unit 2 has entered the final procedures for restart after its continued operation was approved. Korea Hydro & Nuclear Power Co. (KHNP) said it has completed more than 100 facility upgrades, including replacing life-expired equipment and reinforcing accident-response systems, and noted the restart could come as early as late March to early April this year.
KHNP's Kori Nuclear Power Site on the 18th in Gijang, Busan, briefed on the status of facility upgrades for Kori Unit 2, the restart plan, and disaster preparedness and response, with Chairperson Choi Won-ho of the Nuclear Safety and Security Commission and President Lim Seung-cheol of the Korea Institute of Nuclear Safety (KINS) in attendance.
Kori Unit 2 is a 685 MWe pressurized water reactor (a method that pressurizes hot water to generate steam) nuclear plant that began commercial operation in 1983, operated for 40 years, and reached the end of its design life on Apr. 8, 2023. After receiving approval for continued operation last year, it can run until Apr. 8, 2033.
Continued operation is not unique to Korea. The International Energy Agency (IEA) analyzed in January last year that, worldwide, decisions to extend the operating periods of more than 60 reactors (about 15% of all nuclear power plants) were made over the past five years. The International Atomic Energy Agency (IAEA) also said in a 2022 report that 68% of operating nuclear plants worldwide have run for more than 30 years, and about a quarter have exceeded 40 years. In particular, the United States is actively pursuing a policy to extend plant operation from 60 years to 80 years through its regulatory framework. The continued operation of Kori Unit 2 can be seen as a case advanced under this trend of long-term operation of aging nuclear plants.
At a briefing that day, Kori Nuclear Power Site Unit 1 Director Choi Dong-cheol said, "For Kori Unit 2, we carried out more than 100 facility upgrades, including about 40 essential upgrades for continued operation and about 60 in-house upgrades," and explained, "Essential upgrades included replacing life-expired equipment, stress tests, reinforcing accident-response systems, and follow-up actions on fire probabilistic risk assessment."
The core among these is reinforcing accident-response systems to implement the severe accident management plan. The severe accident management plan is a response plan that goes beyond accidents anticipated at the design stage of a nuclear plant to assume larger natural disasters, prolonged blackouts, and even severe accidents, and sets out how to cool the reactor and spent fuel and protect the containment. When Kori Unit 2 restarts, it will become the first case among domestic nuclear plants to reflect the safety measures in the severe accident management plan in actual operation.
Choi said 17 design changes to accident-response equipment were completed in the process of applying this plan in the field. First, for extreme disasters or severe accidents, a new external injection line was created so cooling water can be supplied by connecting to mobile pump trucks. Because failing to cool the reactor and the spent fuel pool can lead to a major accident, a pathway was secured to supply water from outside in an emergency. The level gauges and alarm systems were also reinforced to more accurately determine the water level in the spent fuel pool and inside the containment building.
Reinforcements to the power supply system to prepare for prolonged blackouts were also included. Mobile generator trucks of 1 MW and 3.2 MW were secured, and cables and breakers were installed so electricity can be supplied to essential equipment such as valves, mobile blowers, and air compressors.
Maintenance and testing to prepare for restart have also mostly entered the final stage. KHNP said about 4,500 of a total 4,606 checks in mechanical, electrical, and instrumentation and control fields have been completed, and 380 of 428 tests to verify system performance have also been finished. The remaining tests will proceed sequentially according to the operating mode and startup process stage. In the comprehensive safety assessment, inspections were completed for 39 aging management areas, including the reactor vessel, steam generators, and major piping, and KINS specialists reviewed the adequacy of 10 items that need to be verified at restart.
The fact that restart is imminent does not mean all preparations are complete. According to KHNP, some installations, inspections, and tests remain, and the integrated containment leak rate test is somewhat delayed from the original schedule. Additional items requiring improvement and supplementation were also identified in the special thaw-season inspection.
The restart timing for Kori Unit 2 is expected to be decided after KHNP completes the remaining procedures and a final review by the regulators. A KHNP official said, "Our goal is to complete the related tests and data submissions by dawn on the 25th," adding, "If things proceed as planned, startup may be possible on Mar. 29 after final inspections and meetings by KINS and the Nuclear Safety and Security Commission, but it could slip to early April depending on the situation."
The Nuclear Safety and Security Commission emphasized that confirming safety is just as important as the restart schedule. The Chairperson said on site, "Kori Unit 2 has been in a shutdown state for three years, received approval for continued operation, and is preparing to restart, which is significant," and added, "It is important not to rush the remaining installations, inspections, and tests, but to carry them out thoroughly." The Chairperson continued, "To raise the plant's capacity factor, there ultimately must be no failures, and to achieve that, safety must be sufficiently confirmed in advance and operation must follow procedures."