Tokyo Electric Power Co. began dumping radioactive water from its crippled Fukushima Dai-Ichi nuclear station into the sea so that it would have a place to store more highly contaminated water.
The government approved the discharge so that Tepco, as the utility is known, can drain turbine buildings for the Nos. 2 and 3 reactors of water so radioactive it burned workers, the chief cabinet secretary said.
“We didn’t have any other alternatives,” Yukio Edano told reporters in Tokyo. “This is a measure we had to take to secure safety.”
Tepco has been battling to restart cooling pumps that were knocked out by a March 11 quake and tsunami, resulting in a partial meltdown of some of the plant’s six reactors. Tokyo Electric plans to release 11,500 tons of water containing radioactive iodine levels about 100 times the regulatory limit.
“Until they get rid of that water they can’t get in there to sort out the pumps,” Robin Grimes, a professor of materials physics at Imperial College in London, said by telephone. “If they’re going against regulatory guidelines, that’s definitely not something you’d want to do unless you had very little choice. It’s the least worst option.”
Tepco will discharge 10,000 tons (2.6 million gallons) of water from its waste treatment facility and another 1,500 tons accumulated in pits outside reactor Nos. 5 and 6, said Masateru Araki, a company spokesman.
Filtering radiation from the water would take too long and its release will help protect equipment in the buildings housing the reactors, Junichi Matsumoto, a Tepco spokesman, said at a news conference streamed over the Internet.
The potential additional radiation dose to a person eating seaweed or seafood caught near the plant every day for a year would be 0.6 millisievert, the International Atomic Energy Agency said in a statement. That compares to 0.85 millsievert from a year of exposure to granite that comprises the U.S. Capitol, according to the U.S. Army Corps of Engineers.
Radioactive iodine in seawater near the plant was 630 times the regulatory limit, Tepco said in a statement. The sample was taken 330 meters south of a water discharge.
The company released the information after being ordered by Japan’s Nuclear and Industrial Safety Agency to reevaluate radiation data after publishing errors.
Specialists from sensor manufacturers will follow procedures used by other utilities to determine the radioactivity of air in the plant, the spilled water, and the ocean nearby, the company said today in a statement on its website.
Plugging a Crack
Tepco had been struggling to stop contaminated water from reactor No. 2 from leaking into the ocean through a conduit used to take in seawater.
The company first tried to plug a crack in a power-cable storage pit near the reactor by filling it with concrete on April 2, and yesterday attempted to clog it with a mix of sawdust, newspaper and absorbent polymer used in baby diapers.
The utility plans to build an undersea silt barrier to stop the leak of radioactive fluids and help contain toxic water within the conduit, Hidehiko Nishiyama, Japan’s spokesman on nuclear safety, said in Tokyo yesterday.
“A silt fence ensures that mud down deep doesn’t seep through,” Nishiyama said. The barrier may take “several days” to install.
Threat Not Severe
A silt fence is usually used to filter dirt and solid impurities in rivers and seas during construction, said Yoshinori Hashimoto, a spokesman at Maeda Kosen Co., which makes industrial materials made from fiber, including the barriers. They are also used at the seawater intake gate of nuclear power plants, he said, adding that neither Tepco nor the government has approached the company to place an order.
The leak itself may not pose a severe threat, said Kathryn Higley, professor of nuclear engineering and radiation health physics at Oregon State University.
“You’re likely to have a footprint in the soil and the sands and sediments as that material leaks out, but the impact is likely to be pretty minimal,” Higley said yesterday in a telephone interview. “Even if it does get out into that marine environment, that area around there has been pretty badly torn up, so there’s not a lot of life to be impacting.”
Tepco and government officials met Jeffrey Immelt, chief executive officer of General Electric Co., to discuss technical support to contain the crisis at the Fukushima reactors that are based on the U.S. company’s design.
Fairfield, Connecticut-based GE has offered technical assistance and help through its venture with Hitachi Ltd. Immelt met with Tepco officials including Chairman Tsunehisa Katsumata yesterday and Trade Minister Banri Kaieda yesterday.
GE will offer gas turbines to ease energy shortages in the Tokyo region, Immelt told reporters after meeting Kaieda.