Tokyo Electric Power Co said a tank that leaked highly radioactive water at its damaged Fukushima nuclear plant is one of three that had been dismantled and moved, adding it has yet to determine if that caused the seepage.
The tanks, which were relocated because of ground subsidence at their initial site, were filled and tested for leaks after being reassembled, Noriyuki Imaizumi, an official at the utility who briefed reporters, said in Tokyo on Aug. 24.
Last week’s spillage escalated into the biggest crisis at the wrecked plant since the March 2011 disaster. The alarm was raised after at least 300 metric tons of water leaked, prompting the government to demand strengthening of tanks storing more than 300,000 tons of irradiated water — a volume growing by 400 tons a day as the tanks are filled with water pumped from under the plant’s damaged reactors.
Tepco, as the utility is known, is “going from crisis to crisis,” Michael Friedlander, who has 13 years of experience running nuclear power plants in the U.S., said Aug. 23 in an interview in Hong Kong with Bloomberg TV. “Two years on, managing water should be given more priority.”
Tepco has increased the rate of its inspections and has said that no further leaks of contaminated water have been found. The inspection of about 300 tanks similar in design to the unit that leaked did reveal two separate radiation hot-spots on the seams of two tanks, which the company can’t explain, it said.
‘We don’t know’
“At the moment, we don’t know why radiation was detected,” spokesman Hiroki Kawamata said. No water was found at the hot-spots and water levels in the tanks hadn’t dropped noticeably, he said.
“Investigation will be needed to determine whether or not the detection of radiation means water leaked,” Hirofumi Shibata, an official at the trade ministry’s nuclear accident response office, said on Aug. 23. “Tanks will need to be strengthened.”
Japan’s Nuclear Regulation Authority instructed Tepco to identify the cause of the leak, which was reported on Aug. 20, and present measures to prevent leaks from other tanks, Hideka Morimoto, deputy secretary general at the agency, said last week. It also wants to know how Tepco will remove contaminated soil.
Tepco was careless in its monitoring of the storage tanks and failed to keep records of its inspections, NRA Commissioner Toyoshi Fuketa said after a visit to the plant on Aug. 23, Reuters reported. Fuketa also expressed concern that pipes connecting the tanks may leak, Kyodo News reported.
Stage 3
The regulator rates the accident as a 3 on the 7-stage International Nuclear and Radiological Event Scale or INES, denoting a “serious incident.” The tank has been pumped dry and the water stored.
NRA Chairman Shunichi Tanaka called the possibility of other leaky tanks “the biggest concern” at a press conference on Aug. 21.
Tepco stores about 400 tons of water a day at the plant after using it to cool the reactors that melted down as a result of the March 2011 earthquake and tsunami. The more than 1,000 tanks on-site can hold 390,000 tons of water, according to Kaoru Suzuki, a Tepco spokeswoman. About 330,000 tons of that capacity had been used as of Aug. 13.
The Fukushima station has become “a massive tank farm,” Friedlander said. “That can’t be. It’s subject to earthquakes, it’s subject to natural disasters, it’s subject to leaks. That represents a very clear and present danger to the plant site and to the people working there.”
