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Beznau nuclear power plant in northern Switzerland in 2012, after 53 years of operation.
December 9, 2022
The draft action guidelines for the utilization of nuclear power plants, which were discussed at the METI’s experts’ meeting on December 8, would maintain the current restriction on the operating period and allow operation beyond the “maximum 60 years,” with a view to eliminating the limit in the future. However, there is not a single example in the world of a nuclear power plant that has operated for more than 60 years. In Japan, there has been a string of troubles due to equipment deterioration, and the Nuclear Regulation Authority is having a hard time regulating this “unexplored area. （The Nuclear Regulation Authority of Japan is having a hard time regulating this “unexplored area.)
A thin piece of iron rust (triangle in the center) stuck in a pipe (bottom right) inside the steam generator at the Takahama Unit 4 nuclear power plant in Fukui Prefecture (courtesy of Kansai Electric Power Co.).
According to the International Atomic Energy Agency (IAEA), the longest operating period of a nuclear power plant in the world, including those that have already been decommissioned, is 53 years and one month for India’s Tarapur reactors Nos. 1 and 2. All four reactors are still in operation.
Like Japan, the U.S. has a 40-year operating period, but if a plant passes a regulatory review, it can be extended for 20 years, and there is no limit to the number of extensions. In the U.K. and France, there is no upper limit to the operating period, and a review is required every 10 years.
However, many nuclear power plants were designed and built with a 40-year service life in mind. As nuclear power plants age, maintenance and management costs become higher, and many operators are likely to choose decommissioning over long-term operation.
Even nuclear power plants in Japan that are less than 40 years old are experiencing problems due to deterioration.
Since 2018, KEPCO’s Takahama Units 3 and 4 (Fukui Prefecture), which have been in operation for 37 years, have experienced a series of troubles in which flakes of iron rust have accumulated in the steam generators connected to the reactors over many years of operation, hitting and damaging pipes. The problem was confirmed six times during regular inspections and recurred even after the steam generators were cleaned.
Even more serious are inspection leaks. In 2004, at Mihama Unit 3, which had been in operation for less than 30 years, a pipe that had been omitted from the inspection list and never checked became thin and broke due to age-related deterioration, spewing hot water and steam that killed five people and seriously injured six others.
At TEPCO’s Kashiwazaki Kariwa Nuclear Power Station in Niigata Prefecture, it was discovered in October of this year that the piping in the turbine building of Unit 7, which was shut down shortly after the Fukushima Daiichi nuclear accident, had not been inspected in 11 years and had developed holes due to corrosion.
Hiromitsu Ino, professor emeritus of metallurgy and materials science at the University of Tokyo, said, “Ultrasonic inspection to check the deterioration status is difficult to measure behind the pipes. If deterioration progresses due to long-term operation, the risk of inspection leakage increases, leading to a serious accident,” he warned.
The Regulatory Commission, which examines whether or not to extend operation from the aspect of safety, has been unable to begin considering concrete measures on how to regulate nuclear power plants that are over 60 years old.
A major hurdle is the lack of data on how reactors actually deteriorate. The way of understanding the degree of deterioration differs from that of the U.S., which is ahead of the U.S. in the examination of operation extensions. Shinsuke Yamanaka, the chairman of the committee, said at a press conference, “The period beyond 60 years is an unknown area. We need to create Japan’s own rules,” he said, acknowledging the difficulty of the study.
While the regulations remain unclear, only the mechanism to make it possible to exceed 60 years is moving ahead. Mr. Ino emphasizes. Japan has many earthquakes and a high population density. The situation is different from other countries. Nuclear power plants should be operated for 40 years, which is the design guideline.”
https://www.tokyo-np.co.jp/article/218838.
