Nuclear plant safety standards rendered useless by quake
BY TOMOOKI YASUDA STAFF WRITER
Workers rest without their masks inside this tent set up within the premises of the Fukushima No. 1 nuclear power plant. (Tokyo Electric Power Co.)
The government is being pressured to just throw out its safety standards for nuclear power plants and go back to the drawing board, in light of the March 11 Great East Japan Earthquake and tsunami that crippled the Fukushima No. 1 nuclear power plant.
Therefore, openings of new plants that are currently under construction or in the planning stages are expected to be drastically delayed.
In mid-May, Nuclear Safety Commission chairman Haruki Madarame said that the government would review current safety standards that state that it is not necessary to consider situations in which all sources of electricity are lost at a plant.
"Honestly speaking, it was found at this time that the safety standards have defects. They are apparently wrong," he said.
The government also included the review in the report it submitted to the International Atomic Energy Agency (IAEA) on June 7.
The safety standards consist of about 60 items, all of which are decided by the safety commission. They range from standards on locations and designs of nuclear power plants to basic policies on disaster prevention measures.
Electric power companies have to pass the government's examinations based on the safety standards to receive permission for construction of new power plants or expansion of their current facilities.
If the safety standards are "apparently wrong" as Madarame said, the government cannot conduct examinations. Therefore, there is a high possibility that the government cannot issue permission for new construction or expansions for the time being.
In the current nuclear crisis at the Fukushima No. 1 plant, multiple protection measures that constitute the basics to secure safety of nuclear power plants were quickly rendered useless one after another.
"In the current crisis, several abnormalities took place simultaneously. It overturned the idea that the possibility is extremely low that troubles unrelated to each other can occur at the same time," said former safety commission chairman Kazuo Sato.
For example, the current safety standards do not take into account a situation in which all sources of electricity are lost. That is because the resumption of electric power across transmission lines or repair of emergency electric sources are expected, the standards state.
In the current crisis in Fukushima, however, neither was restored.
Other safety standards were also found to be defective. The tremor that struck the Fukushima No. 1 plant was about 25 percent larger than that assumed possible under the new safety standards, which were introduced in 2006.
The tremor imagined in the 2006 safety standards had been 60 percent larger than that assumed in the previous standards. In spite of that, the new standards were still insufficient.
In the current safety standards, the evacuation areas are assumed to be those within a radius of about 10 kilometers. In the on-going crisis, however, the evacuation areas have been expanded to districts beyond 30 kilometers.
In the present crisis, the total amount of radioactive iodine released from the No. 1, No. 2 and No. 3 reactors of the Fukushima plant is about 150,000 terabecquerels. Tera is one trillion times. In the safety standards, however, the assumed maximum amount is one-hundredth of that amount or lower.
In the Fukushima crisis, nuclear fuel rods melted down and accumulated at the bottom of pressure vessels in some reactors. However, the safety standards did not address the possibility of a meltdown.
It took five years for the government to revise the safety standards to the new ones in 2006 from the start of discussions. If the government implements an all-out review of the 2006 ones, it may take much longer.