Due to climate change, the sea water temperature is rising every year, placing eight domestic reactors at risk of halting operations within the next 10 years. If the reactors stop, it could severely impact the domestic electricity supply. The nuclear regulatory authorities and operators have decided to undertake a large-scale improvement project to reinforce nuclear facilities and raise the operational minimum, known as the 'design sea temperature'. The design sea temperature refers to the maximum temperature of seawater at which a nuclear reactor can operate safely.
The Nuclear Safety And Security Commission held a meeting on the 14th in the Seoul Namdaemun conference room to discuss the current response measures and future plans related to the increase in sea temperatures with Korea Hydro & Nuclear Power (KHNP), the operator of the reactors. KHNP has incrementally raised the limit temperatures for reactor shutdowns within safe operational limits, but will now enhance facilities to safely operate at even higher temperatures.
Currently, following improvements to the Shin-Wolsong Unit 1 and 2 facilities in Gyeongbuk Gyeongju, improvements to the Hanbit Units 1 to 6 in Jeonnam Yeonggwang are set to be completed by 2029. Long-term plans include extending this to all nuclear power plants to raise the sea temperature limits. KHNP is operating a task force to promote facility improvements in collaboration with design and supply partners.
These response measures were supplemented to reflect the implementation status since KHNP's initial report in 2022 and the recent trend of rising sea temperatures. Previously, there were criticisms in the political sphere regarding the lack of comprehensive measures reported for several years, despite the serious risks of climate change. For the reactors to operate safely, seawater must be brought in to cool the reactors. The heated water from the reactor is then returned to the sea.
As climate change continues to raise sea temperatures, cooling efficiency has decreased, increasing the risk of equipment failure. Recently, the average annual sea temperature near the Korean Peninsula has been rising by 0.087 degrees. If the seawater exceeds the design sea temperature, the power plant must halt the reactor within 6 hours and complete cooling within 36 hours.
The design sea temperature at the Shin-Hanul Unit 1 and 2 near Uljin is the lowest at 31 degrees Celsius, while the Gori Unit 2 in Busan Gijang is the highest at 36.1 degrees. According to KHNP's analysis, Shin-Wolsong Units 1 and 2 are expected to reach the design sea temperature in 2030, Hanbit Units 3 and 4 in 2031, and Hanbit Units 1, 2, 5, and 6 in 2034.
The timing for reaching the design sea temperature could be accelerated. After last year's coastal sea temperature recorded the highest since observations began, KHNP adjusted the projection times for reaching the temperature for each reactor. The Gori Unit 2, which was projected to reach it in 2087, has been moved up to 2050, 37 years earlier, while Gori Units 3 and 4 and Hanbit Units 3 and 4 are expected to be accelerated by 20 years and 9 years, respectively.
The issue is that electricity demand is increasing every year. The Ministry of Science and ICT has projected that due to extreme heat this summer, the peak electricity demand could exceed last year's record to reach up to 97.8 GW (gigawatts). To handle this, the reactors must operate continuously.
KHNP has decided to begin facility improvements for reactors expected to exceed the design sea temperature within the next 10 years. The most urgent units, Shin-Wolsong 1 and 2, will extend the heat exchanger plates to improve cooling performance and have raised the limit by 1.37 degrees. They plan to apply for an operating change permit within this month. The heat exchanger plate enhancement involves stacking thin metal plates, allowing high-temperature and low-temperature fluids to flow between them to exchange heat.
Following that, other reactors, including Hanbit Units 3 and 4, will be improved sequentially, with the goal of completing all work by 2029. The projected year for reaching limit temperatures will be re-evaluated each year to reflect the rate of rising sea temperatures, and by the end of next year, a system to predict seawater temperatures at the intake using artificial intelligence (AI) will be developed and applied to all reactors.
Choi Won-ho, the chairman of the Nuclear Safety And Security Commission, stated, "In preparation for accelerated global warming, please swiftly promote facility improvements to fundamentally resolve the issue, and ensure readiness to respond immediately when high sea temperatures are observed." He added, "The Commission will regularly inspect to ensure that the facility improvements are implemented without any setbacks."