'I was fully aware of what would be destroyed.
I did not know what would be built out of the ruins'
Monday, April 11, 2011
Sinister seven: what Japan's new nuclear crisis rating means
April 12, 2011 - 3:23PM
A Japanese policeman wearing a protective radiation suit stands guard as his colleagues load a dead body into a van inside the deserted evacuation zone around the Fukushima Dai-ichi nuclear reactors. Photo: David Guttenfelder/AP
A magnitude-6.3 earthquake struck Japan's Fukushima prefecture at 2:07 pm, the Japan Meteorological Agency said. The earthquake had a depth of 10 kilometres, with no danger of damage from a tsunami, Bloomberg reported.
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Fire and smoke are seen at a building for sampling from seawater near No.4 reactor of the Fukushima Daiichi nuclear plant. Photo: Reuters/TEPCO
Chemistry and physics professor Stephen Lincoln, of Adelaide University, said the main worry was the food stock in the ocean, where much of the radioactive material was being released.
While one of the radioactive substances, iodine-131, had a half-life of nine days, two others - caesium-137 and the strontium-90 - could be more harmful in the long term as they had half-lives of 30 years, he said.
"[People] should not venture into the ocean [where the radioactive materials are being released]; they should not eat any fish or seaweed from the ocean.
"The living species likely to be most affected are shellfish because they are stationary whereas fish that swim may pass through the area and out again. The shellfish such as mussels, oysters and clams certainly accumulate high levels of radioactivity.
"If they can stop the leaks, then the ocean can disperse the radioactivity until it becomes no more than background."
A level seven 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.
Professor Lincoln said workers at the nuclear plant had to get the cores of the reactors continuously underwater to keep them cool, "otherwise it's going to go on and on and on unfortunately".
The cores, damaged during an earthquake and tsunami on March 11, have being releasing high radioactive substances into the atmosphere and ocean.
Japanese nuclear safety agency officials said the radiation released so far was estimated to be around 10 per cent of that from Chernobyl 25 years ago.
But they fear the total amount of radiation released in Japan may exceed Chernobyl, spokesman for plant owner Tokyo Electric Power Company (TEPCO) Junichi Matsumoto said at a news conference today.
"Basically we should be worried until they can stop the [radiation] leaks and cool the cores and the fuel rods down," Professor Lincoln said.
"And from time to time they've thought they achieved that but unfortunately something else has disturbed the situation."
Minoru Oogoda of Japan's Nuclear Industry and Safety Agency (NISA) told the Associated Press that his country had updated the severity level to seven "as the impact of radiation leaks has been widespread from the air, vegetables, tap water and the ocean".
The revision was based on cross-checking and assessments of data on leaks of radioactive iodine-131 and cesium-137, another NISA spokesman, Hidehiko Nishiyama, told AP.
"We have refrained from making announcements until we have reliable data," Mr Nishiyama said.
"The announcement is being made now because it became possible to look at and check the accumulated data assessed in two different ways," he said, referring to measurements from NISA and the Nuclear Security Council.
Professor Lincoln said much of the radiation appeared to be going into the sea rather than the atmosphere.
"I think they have assessed that the amount of radioactivity being released is similar to that of Chernobyl but it is largely being contained in water, which is going into the ocean," he said.
"The difference between Chernobyl and Fukushima is this - Chernobyl had a massive explosion and spread a large radioactive cloud over much of Europe very quickly and it looks as though the Fukushima incident is not going to do that, although there is some in the atmosphere that has been released."
Tens of thousands of residents have been evacuated from an exclusion zone covering a 20-kilometre radius from the Daiichi plant and many more living close by have been advised to stay indoors.
Yesterday, the Japanese government said it would order people to leave certain areas outside the exclusion zone due to concerns over the effect of long-term exposure to radiation, but that a uniform extension of the zone was not appropriate.
Emergency crews at the plant have battled around the clock to bring the disaster under control and yesterday, the government said the danger of a large leak of radioactive materials was becoming "significantly smaller".