Residents evacuated from the west side of Fukushima receive a radiation scan in Nihonmatsu city in Fukushima prefecture.
Credit: AFP PHOTO / GO TAKAYAMA
PARIS: Scientists from around the world have provided a snapshot of possible scenarios for radioactive contamination from the crippled Fukushima plant in Japan, predicting that radiation will extend over the 20 km exclusion zone.
Fifty workers are still tasked with keeping cooling water flowing into the six reactors at the plant, four of which have overheated since Friday's quake. Explosions and a fire at the plant, 250 km northeast of Tokyo, have unleashed levels of radiation, forcing the operator to pull out hundreds of workers and leaving just a few dozen behind.
“The 20 km exclusion zone is part of the standard emergency response protocols which are established at every nuclear facility," said radiation physicist Steve Crossley who worked in the British nuclear industry from 1996 to 2002. "The levels which have been reported from Tokyo are of no concern, there are many places in the world where the natural background radiation levels are higher than the reported ‘elevated’ levels in Tokyo.”
Short term effects on the area
The Japanese government on said radiation posed no immediate health threat outside a 20-kilometre exclusion zone established around the plant. In Tokyo, the U.S. embassy warned American citizens living within 80 km of Fukushima to evacuate or seek shelter.
Jacques Repussard, head of France's Institute for Radiological Protection and Nuclear Safety (IRSN), said there was a radioactive plume in a zone of "several dozen kilometres" around the plant.
It will extend over a zone of several hundred kilometres "in the coming days" but have no consequences for health in Tokyo, an agglomeration of 30 million people lying 250 kilometres to the southeast, he said.
Long-term effects on the area
Scenarios are coloured by many unknowns concerning the rate and type of radioactive release. Repussard, who was speaking at a French parliamentary committee meeting, said there could eventually be a "strongly contaminated zone" extending up to 60 km around Fukushima, beyond which "there will be measurable impacts but not dramatic impacts."
Didier Champion, who overseas environment and intervention issues at the IRSN, said Fukushima would probably generate "more local impacts than were seen for Chernobyl."
"The downside is that contamination is likely to be more concentrated inside a 10- to 20- kilometre zone. The upside is less contamination over a larger area," he said.
Main sources of contamination
Longevity of highly toxic nuclear waste is a major problem. The likely contaminants from Fukushima are iodine-131 and caesium-137, with half-lives of eight days and 30 years, respectively.
The half-life is the number of years required for any amount of a radioactive element to decompose by half. Typically, such elements remain hazardous for a period 10 times their half-lives.
Radioactive iodine and caesium are carcinogenic and pose a threat to health, whether directly in the polluted air or water or indirectly through the food chain. Radioactive iodine is highly volatile and disperses easily into the air in the form of vapour plumes such as those generated by the disabled Fukushima reactors.
Contamination scenarios from Fukushima
Some glaring errors in this article." Didier Champion overseas environment". Should be oversees? Seems a bit pedantic, but I wouldn't want Cosmos to lose it's reputation as a credible source, just because an article has been rushed out. Cheers