Author: Desislava Georgieva
Published On: 11/08/2023

Today marks the 19th anniversary of the most serious nuclear power plant accident in Japan since that at the Fukushima nuclear power plant. The accident at the Mihama nuclear power plant, 320 km west of Tokyo on the island of Honshu, occurred on 9 August 2004. The turbine of the third reactor released a powerful steam at a temperature of about 200 degrees Celsius. There were 200 employees in the reactor building at the time of the accident. Five died and 18 others received serious burns. Authorities officially report that no traces of leaking radioactive material have been found.

The fallen pipe was made of black steel, which corrodes easily. The real problem was the thickness of its wall, which was originally 10 mm and needed to be no more than 4.7 mm thick to work safely. However, it eroded to 1.4 to 1.5 mm. For such a disastrous situation to occur, an error was made either at the engineering design stage where the phenomenon of corrosion was ignored or during a routine inspection. Major inspections of nuclear power plants are usually carried out every 10 years. This means that in the 28-year period of activity up to the time of the accident, the reactors should have been subject to at least two major inspections. According to unconfirmed reports, this tube has not been inspected once since the reactor was commissioned.

An opinion poll conducted seven years after the Mihama accident shows that 74 per cent of Japanese support the idea of phasing out the nuclear plant. However, two years ago, the crippled third reactor at the Mihama nuclear power plant was officially restarted. It is the oldest reactor (1976) to be brought into operation after the disastrous accident at Fukushima. Energy experts warn that history could repeat itself. The local population is also worried. By comparison, the Fukushima plant was commissioned in 1971 and its reactors were 40 years old at the time of the meltdown on 11 March 2011, when, under the influence of unforeseen natural cataclysms, the plant failed and caused the deaths of nearly 20,000 people in north-eastern Japan.

Mihama’s owners managed to extend the reactor’s life by investing 165 billion yen ($1.51 billion) in repairing infrastructure, electronics, replacing cables and seals according to the latest safety standards imposed after the Fukushima disaster, which are resistant to high temperatures in accidents and fire. By law, 40-year-old reactors can be refurbished and, if approved by a committee, operate for an additional 20 years. The reactors at Mikhama have been shut down for more than a decade, and now their life has been extended to 2036.

atsujiro Suzuki, a former vice chairman of the Japanese government’s Atomic Energy Commission, tells Reuters he has doubts about the approval process for restarting the reactor at the Mihama nuclear plant. “It seems that the industry and the government have learned nothing from Fukushima,” Suzuki says.