For Tohoku Electric Power, which restarted Unit 2 of the Onagawa (Miyagi Prefecture) Nuclear Power Plant on the 29th, it will be the first time in 13 years since the Great East Japan Earthquake that it has operated a nuclear power plant . Almost 40% of employees on site have no driving experience, and there is concern about how to respond to emergencies. In addition, it is located on the coast of Sanriku, which is said to have many natural disasters, and the reactor is a type of boiling water, the same as the Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Plant, which was cause of the accident. There are many obstacles waiting to drive. (Rokuki Arai, Hazuki Yamashita)
◆13 years since the earthquake, there is a generational change in the field
“The issue of human resource development related to long-term shutdowns requires soft measures such as operator training.”
Shinsuke Yamanaka, chairman of the Nuclear Regulatory Authority, answered this at a press conference on the 23rd when asked about his concerns about the restart.
Nuclear Regulatory Authority Chairman Shinsuke Yamanaka (Photo taken on September 4)
At the time of the Great East Japan Earthquake of March 11, 2011, Units 1 and 3 of the Onagawa Nuclear Power Plant were operating. Unit 2, which was under routine inspection, had just restarted about 40 minutes before the accident, but all three units narrowly avoided a serious accident.
Three and a half years have passed since then, and the generation of site operators has changed. According to Tohoku Electric Power, as of April this year, 200 (39%) of the 517 technical employees working in the nuclear power plant had no operational experience, and 51 (36%) of the 140 were directly involved employee to work. they are said to be inexperienced. A representative from Tohoku Electric Power Co. explains, “We try to increase their experience by guiding veteran workers to young workers in the field and sending them to nuclear power plants in Japan and the United States.”
◆Heian, Edo, Meiji, Showa…Frequent large tsunamis
The Sanriku coast, where the Onagawa nuclear power plant was built, has historically been considered at high risk from natural disasters such as earthquakes and tsunamis. The distance from the epicenter of the Great East Japan Earthquake was about 180 km southwest of Fukushima Daiichi, and Onagawa was the nearest nuclear power plant about 130 km northwest.
Onagawa nuclear power station (photographed in 2011)
In the past, large tsunamis hit the area many times, including the Jogan tsunami (869) during the Heian period, the Keicho Sanriku earthquake (1611) during the Edo period, the Meiji Sanriku tsunami (1896), and the Showa Sanriku tsunami (1933).
As a result, while some nuclear power plants only take about a year to complete, the NRA took six years and two months to review the Onagawa No. 1 nuclear power plant. Chairman Yamanaka explained, “We did a careful review because this is a nuclear power plant that has experienced a major earthquake and has the potential to generate a major tsunami.”
◆ Boiling water reactor like Fukushima Daiichi
In addition, the Onagawa No. 1 nuclear reactor is a boiling water type reactor. 2, just like the Fukushima Daiichi reactor No. 1, and the memory of the accident will never be erased. The 12 nuclear power plants restarted so far are a type of pressurized water. The boiling water type has a simpler structure than the pressure water type, but because the steam produced in the reactor turns the turbine directly, the turbine can become contaminated and is said to be difficult to manage.
Masashi Goto, a former Toshiba nuclear reactor designer who worked on the Onagawa Unit 3 reactor, said, “The earthquake reduced the rigidity of the Unit 2 building (which indicates its resistance to deformation).” “There is a lot of damage to the concrete foundation. I’m also concerned about damage to the turbine,” he said.
He said, “The boiling water type has a small restricted vessel, and the pressure increases suddenly in the event of an accident. On the other hand, the pressure water type has the disadvantage that the temperature and pressure are high and the heart melting. It happens when there is no such thing. It’s the same for both types.”
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