Tokyo Electric Power Co. prepared to inject nitrogen into reactors to avoid a possible explosion at its stricken nuclear power plant after succeeding in stopping highly radioactive water leaking into the sea.
The utility, known as Tepco, was set to start feeding the gas into the Fukushima Dai-Ichi No. 1 reactor container vessel around 1 a.m. today, according to a press briefing in Tokyo late yesterday. Tepco will later pump the gas into the Nos. 2 and 3 reactors to purge hydrogen and oxygen, which can interact and cause an explosion.
There’s no immediate danger of a hydrogen explosion, Hidehiko Nishiyama, an official at the Nuclear and Industrial Safety Agency, said yesterday. Accumulation of hydrogen in the days after the March 11 earthquake and tsunami triggered three blasts at the station, damaging reactor buildings and releasing radiation into the air.
“It’s a bit like locking the stable door after the horse has bolted, but it’s a sensible thing to do,” said Tony Roulstone, an atomic engineer who directs the University of Cambridge’s masters program in nuclear energy. Tepco needs to ensure there is no oxygen left in the reactor, and “it’s not a simple thing,” he said.
Engineers used sodium-silicate to stop the release of highly radioactive water near the No. 2 reactor, the utility said yesterday. Tepco has previously tried plugging the leak with materials including concrete, sawdust, newsprint and absorbent polymer used in diapers.
The country’s nuclear safety agency said water may be leaking from another part of the station, which has six reactors and is about 220 kilometers (137 miles) from Tokyo.
“This isn’t a situation where we can be relaxed at all,” Chief Cabinet Secretary Yukio Edano told reporters yesterday.
Tepco has been pouring water to cool the reactors and spent fuel after the March 11 disaster knocked out backup generators and cooling systems, creating the worst nuclear crisis since Chernobyl.
The measures being taken to stabilize the reactors are posing new threats as filling reactor containment vessels with water makes them vulnerable to rupturing when aftershocks occur, the New York Times reported, citing a confidential March 26 report prepared by U.S. Nuclear Regulatory Commission engineers sent to assist the Japanese government. Explosions may occur as hydrogen and oxygen are released from the water, according to the report, the Times said.
Tepco stock fell 6.9 percent to 337 yen, a record low, on the Tokyo Stock Exchange yesterday. About 303 million shares were traded, the most on record. The stock is down 84 percent since the day before Japan was struck by the magnitude-9 earthquake, the country’s strongest on record.
The company’s 1.155 percent bonds due in Sept. 2020 fell yesterday and were yielding 3.8 percent, or 2.56 percentage points more than government bonds of similar maturity. The bonds were yielding about 0.13 percentage points more than government debt before the earthquake hit.
The utility began dumping 11.5 million liters (3 million gallons) of water with low levels of radiation into the sea on April 3. Tepco said yesterday that 7 million liters of such water has been discharged.
Officials from Ibaraki on April 5 detected fish contaminated with higher-than-acceptable levels of Cesium, the first discovery of tainted seafood in Japan after the station was damaged.
Exposure to Cesium-137, among the isotopes Tepco says were released from the plant, increases the risk of cancer, according to the U.S. Environmental Protection Agency.
The risk to people from the deliberate discharge at the Fukushima plant is low, according to the Vienna-based International Atomic Energy Agency.
The level of radioactive iodine in seawater sampled near the No. 2 reactor April 5 fell to 280,000 times the amount allowed by regulators, Tepco said. Samples taken on April 2 at the same location found 7.5 million times the permitted amount.
About 60,000 tons of contaminated water lies in basements and trenches outside reactor Nos. 1, 2 and 3, Takeo Iwamoto, a company spokesman, said April 5. Tokyo Electric plans to pump half of that to a waste-treatment facility and the rest to tanks and floating storage vessels, he said.
Japan has also asked Russia to send a ship capable of processing nuclear waste.
The number of dead and missing following the earthquake and tsunami was at 27,631 at 8 p.m. local time yesterday, according to the National Police Agency.