Japan says it is stepping up efforts to cool overheating fuel at the tsunami-hit Fukushima Daiichi nuclear plant yesterday.
Water cannon and six fire engines and were sent in the evening to spray the plant’s No 3 reactor. But afterwards radiation emissions rose from 3,700 microsieverts per hour to 4,000 per hour, the Kyodo news agency quoted Tokyo Electric Power (Tepco) as saying.
An earlier attempt in which military helicopters dropped thousands of litres of water on the plant also appeared to have failed, reports the Guardian.
The confirmed death toll from Friday’s 9.0 magnitude quake, which triggered the tsunami, has risen above 5,400.
Police say about 9,500 people are still missing, reports BBC.
IAEA official Graham Andrew told reporters in Vienna that the situation at Fukushima had not deteriorated, but could yet do so.
“We could say it’s reasonably stable at the moment compared to yesterday,” he said.
Washington and other foreign capitals have expressed growing alarm about radiation leaking from the plant, severely damaged by a magnitude 9.0 earthquake and tsunami a week ago that triggered a series of destructive explosions which compromised the nuclear reactors and spent fuel storage tanks.
Yukiya Amano, head of the Vienna-based International Atomic Energy Agency (IAEA), was due back in his homeland later on Friday with an international team of experts after earlier complaining about a lack of information from Japanese authorities on the crisis.
Even if Tepco manages to connect the power, it is not clear the pumps will work as they may have been damaged by the natural disaster or subsequent explosions. Work has been slowed by the need to frequently monitor radiation levels to protect workers.
US officials took pains not to criticize Japan’s government, but Washington’s actions indicated a divide with its close ally about the perilousness of the world’s worst nuclear accident since the Chernobyl disaster in 1986.
Mr Andrew said reactor 4, which was inactive but being used to store spent fuel rods, was still a “major safety concern” and that water levels were also falling in the cooling pools of reactors 5 and 6.
But he said there had been no rise in radiation in Tokyo and that levels remained far below those dangerous to human health.
The head of the IAEA, Yukiya Amano, is en route to Tokyo to be briefed by Japanese officials.
Despite assurances, the streets of the capital – including its popular Ginza retail district – remain unusually empty, with many people continuing to stay at home or leaving the capital.
Japan’s military CH-47 Chinook helicopters began spraying tonnes of seawater on reactors 3 and 4 at Fukushima, 220km from Tokyo, at 0948 local time (0048 GMT), officials said.
The aircraft dumped four loads before leaving the site in order to minimise the crews’ exposure to radiation. On Wednesday, the helicopters were forced to abort a similar operation amid concerns over high radiation levels.
The BBC’s Chris Hogg in Tokyo says the helicopters can carry an enormous amount of water but given the high winds it is difficult to know whether it has been dropped accurately.
Video footage suggests the attempts were not very successful, with most of the water falling outside the target buildings.
Later military lorries on the ground joined in with water cannon, dousing reactor 3.
Initially police crews had tried to spray the reactor but were forced to withdraw because they would have been exposed to high radiation levels. The military vehicles, unlike those of the police, are built to allow personnel to remain inside, Japan’s NHK TV reported.
The US-made reactors at Fukushima are coming under close scrutiny as experts point to flaws in their original design and the lack of a safety feature that the nuclear industry is only now starting to address.
Five of the six reactors at Fukushima No 1 nuclear plant are so-called Mark 1 boiling water reactor (BWR) models, developed by General Electric in the 1960s and installed in Japan in the 1970s.
In the 1970s, criticism amplified that the Mark 1’s concrete containment shield, which surrounds the reactor vessel, was vulnerable to explosion caused by a buildup of hydrogen gas if the reactor overheated.
The original design “did not take into account the dynamic loads that could be experienced with a loss of coolant,” Dale Bridenbaugh, who quit as a GE engineer in 1975 over the alleged problem, told ABC News on Wednesday.
Blasts attributed to hydrogen have occurred at four of the Fukushima units, and the containment vessels at the No 2 and No 3 reactors have reportedly been damaged but not apparently ruptured, reports AFP.
A partial meltdown of the fuel rods has occurred in the No 1, 2 and 3 reactors but the information from Fukushima — while sketchy — indicates the steel shells surrounding the reactors themselves have not been breached, say French safety agencies.
Michael Tetuan, spokesman for GE Hitachi Nuclear Energy, the current GE unit developing and selling nuclear plant technology, said there were 32 Mark 1 installations in the world, in addition to 23 in the United States.
The US Nuclear Regulatory Commission (NRC) ordered US operators to retrofit Mark 1 plants in the 1980s to strengthen the containment vessel, he said.
“We shared that with our customers overseas … but I can’t tell you if they did indeed retrofit,” he said.
“We understand that all of the BWR Mark 1 containment units at Fukushima Daiichi also addressed these issues and implemented modifications in accordance with Japanese regulatory requirements.”
Questions are also being asked about another aspect of the Mark 1 design, namely the location of cooling tanks which hold highly radioactive spent fuel rods.
They are placed outside the protection of the containment vessel.
These pools are now the source of intense anxiety in Fukushima, because pumps designed to circulate and top up the water that cools the immersed rods failed in the tsunami generated in the quake.
In Paris, Olivier Gupta, deputy director general of France’s Institute for Radiological Protection and Nuclear Safety (IRSN), said the location of the fuel-rod pools outside the containment vessel was common to “many nuclear reactors, including in France.”
COOLING POOL RAN DRY?
The top US nuclear regulator said the cooling pool for spent fuel rods at the complex’s reactor No 4 may have run dry and another was leaking, Reuters reports.
Gregory Jaczko, head of the US Nuclear Regulatory Commission, told a congressional hearing that radiation levels around the cooling pool were extremely high, posing deadly risks for workers still toiling in the wreckage of the power plant.
“It would be very difficult for emergency workers to get near the reactors. The doses they could experience would potentially be lethal doses in a very short period of time,” he said in Washington