Nuclear disaster now on par with Chernobyl*
April 12, 2011
Japan has raised the severity level of its nuclear crisis to seven to put it on a par with the Chernobyl accident 25 years ago as engineers battled a fire at the Fukushima Daiichi nuclear power plant.
Japan had previously assessed the accident at level five, the same level as the Three Mile Island accident in the United States in 1979.
Meanwhile, another major aftershock rocked eastern Japan today, swaying buildings in central Tokyo and closing runways at Narita, Japan's main international airport.
Japan's Nuclear Industry and Safety Agency (NISA), the country's nuclear safety watchdog, told national broadcaster NHK that it raised the crisis level to seven as the damaged facilities at the plant were continuing to release large amounts of radioactive substances.
Japan said this reflected the initial severity of the crisis and not the current situation.
"This is a preliminary assessment, and is subject to finalisation by the International Atomic Energy Agency," an NISA official said.
But nuclear industry specialist Murray Jennex, an associate professor at San Diego State University in California, told Reuters the comparison with Chernobyl was wrong.
"It's nowhere near that level. Chernobyl was terrible - it blew and they had no containment, and they were stuck. [Japan's] containment has been holding, the only thing that hasn't is the fuel pool that caught fire," he said.
A level 7 incident entails a major release of radiation with widespread health and environmental effects, while a five-rated event is a limited release of radioactive material, with several deaths from radiation, according to the International Atomic Energy Agency.
The scale is designed so the severity of an event is about 10 times greater for each increase in level.
Tokyo Electric Power Co (TEPCO), the operator of the crippled nuclear plant, which is 240 kilometres north of Tokyo, said that a fire that broke out at damaged reactor No.4 had been put out.
TEPCO said the fire had no impact on radiation levels around the plant or on the plant's cooling systems.
The Australian dollar dipped against the yen and the greenback as a result of the fire.
News of the fire came only minutes after a 6.3 aftershock struck off the coast of Chiba, 77 kilometres north-west of Tokyo. Kyodo said Narita Airport closed runways for checks but later resumed flights.
An aftershock measuring 6.6 hit Fukushima prefecture yesterday evening, temporarily cutting power and forcing workers to evacuate the nuclear plant.
NISA said the Fukusihima aftershock, which killed one man and knocked out power to 220,000 households, did not damage the nuclear plant.
There have been hundreds of aftershocks since March 11 when a massive 9 magnitude earthquake and 15-metre tsunami hit north-east Japan, plunging the country into its worst crisis since World War II.
Nearly 28,000 Japanese are dead or missing and the world's third-largest economy is reeling from power blackouts, factory closures and cuts to supply lines.
The International Nuclear and Radiological Event Scale (INES), published by the International Atomic Energy Agency, ranks nuclear incidents by severity from one to a maximum of seven.
Kyodo said the government's Nuclear Safety Commission had estimated that, at one stage, the amount of radioactive material released from the reactors had reached 10,000 terabequerels per hour of radioactive iodine 131 for several hours, which would classify the incident as a major accident according to the INES scale.
Kyodo did not say when the big increase in radiation had happened but quoted the commission as saying the release had since fallen to under one terabecquerel per hour.
The commission also released a preliminary calculation for the cumulative amount of external exposure to radiation, saying it exceeded the yearly limit of one millisieverts in areas extending more than 60 kilometres to the north-west of the plant and about 40 kilometres to the south-south-west.
"It has been obvious all along this was a seven. There are three reactors that are not being cooled [No. 1, 2 and 3] and four fuel pools, too [No. 1, 2, 3, and 4]," said Arnie Gundersen, a 29-year veteran of the nuclear industry who worked on reactors similar to those at Daiichi and who is now chief engineer at Fairewinds Associates of Burlington, Vermont.
He said that means there were at least seven cores or pools that had been in difficulty. He noted that, at Chernobyl, it was only one reactor that created the problem.
A spokesman for NISA said he was unaware of any move by the government to raise the level.
Radioactive water
The March 11 tsunami, the largest recorded in quake-prone Japan, crippling the reactors' cooling systems.
Engineers at the plant said they were no closer to restoring the plant's cooling system, which is critical in bringing down the temperature of overheated fuel rods and in bringing the six reactors under control.
TEPCO said yesterday it had stopped the discharge of low-level radioactive water into the sea that have drawn complaints from neighbouring China and South Korea.
It has already pumped 10,400 tonnes of low-level radioactive water into the ocean to free storage capacity for highly contaminated water from the reactors.
In a desperate move to cool the highly radioactive fuel rods, TEPCO has pumped water on to reactors, some of which have experienced partial meltdown.
But the strategy has hindered moves to restore the plant's internal cooling system as engineers have had to focus on how to store 60,000 tonnes of contaminated water.
Engineers are also pumping nitrogen into reactors to counter a build-up of hydrogen and prevent another explosion sending more radiation into the air, but they say the risk of such a dramatic event has lowered significantly since March 11.
Evacuation zone widens
Because of accumulated radiation contamination, the government is encouraging people to leave certain areas beyond its 20-kilometre exclusion zone around the plant. Thousands of people could be affected by the move.
TEPCO President Masataka Shimizu visited the area yesterday for the first time since the disaster. He had all but vanished from public view apart from a brief apology shortly after the crisis began and has spent some of the time since in hospital.
"I would like to deeply apologise again for causing physical and psychological hardships to people of Fukushima prefecture and near the nuclear plant," he said, grim-faced.
Dressed in a blue work jacket, he bowed his head for a moment of silence with other TEPCO officials at 2.46pm, exactly a calendar month after the earthquake hit.
* Url:http://www.smh.com.au/environment/nuclear-disaster-now-on-par-with-chernobyl-20110412-1dbpa.html#ixzz1JiOA7KRV
