Nuclear power plants will need to build secondary control centers at least 100 meters from reactor buildings to manage emergency cooling systems and radiation filter vents, according to the rules. They also stipulate tougher tsunami defenses.
All but two of Japan’s 50 reactors are idled for safety assessments after a record earthquake and subsequent tsunami on March 11, 2011, caused meltdowns and radiation leaks at Tokyo Electric Power Co.’s Fukushima plant. The NRA was set up after Fukushima to provide reviews independent of the trade and industry ministry that oversees nuclear power.
“Some plants may have to undergo large reconstruction” to meet NRA requirements, Tomoko Murakami, a nuclear analyst at the Institute of Energy Economics Japan, said by phone today. For those sites, “it may take several years before they can restart.”
A group of scientists led by Toyoshi Fuketa, the regulatory agency’s commissioner, approved the requirements today in Tokyo, said Tatsuya Taguchi, an NRA official who attended the meeting. The rules will be implemented in July after inviting public comment, according to the NRA.
Quake and Tsunami
Earlier this week, another NRA panel led by Kunihiko Shimazaki, a seismologist and agency commissioner, approved rules for assessing earthquake and tsunami risk.
Currently, power companies are required to assess geological faults using rock and earth samples from the last 120,000 to 130,000 years, or the Late Pleistocene era. The new rules require investigation of faults going back 400,000 years if study of Late Pleistocene geology is inconclusive.
The NRA is investigating quake faults under nuclear plants owned by Kansai Electric Power Co., Tohoku Electric Power Co., Japan Atomic Power Co., Hokuriku Electric Power Co. (9505), and Japan Atomic Energy Agency. The widened definition may prompt the regulator to investigate faults under other nuclear power plants, Murakami said.
Geological faults under Tokyo Electric Power Co.’s Kashiwazaki Kariwa plant, the world’s biggest, could be judged active, Kyodo News reported last week, citing the NRA’s earlier draft of the safety rules.
Restarting the Kashiwazaki Kariwa reactors is key to reviving Tokyo Electric, which was taken over by the government because costs stemming from the Fukushima disaster threatened it with bankruptcy.
On tsunami defenses, utilities must estimate tsunami risk based on the latest scientific assessments, according to rules approved by the Shimazaki panel. Tsunami defenses such as seawalls and watertight doors must be able to withstand the largest estimated tsunami, under the rules.
After Fukushima, it was revealed Tokyo Electric’s own research showed the plant could be hit by a tsunami more than 10 meters (33 feet) high, while its defensive seawall was only 5.6 meters high. The March 11 tsunami that wrecked the plant reached 13 meters.