One year after Fukushima, contamination is "chronic and perennial"

Le Monde.fr with AFP | 02.28.2012

A year after the disaster that hit Japanese nuclear plant in Fukushima, radioactive contamination has decreased sharply but is now "chronic and sustained," said Tuesday the Institute of Radiation Protection and Nuclear Safety French (IRSN), which publishes a report based on reports of its teams and the data provided by Japan. Estimates are still preliminary, conducted by IRSN since the disaster, discharges of radioactive iodine in the atmosphere reached 408 million billion becquerels, an impressive figure but still ten times lower than that of the explosion of the Chernobyl plant in 1986. These iodines have a "half life" very short, ie half its radioactivity decreases rapidly (from hours to eight days depending on the type of iodine) and they mostly represented a risk to the environment and health during the first weeks after the accident.

98% of the initial radioactivity of cesium-137 IN THE ENVIRONMENT

But the three reactors rugged and hydrogen explosions in the buildings of the plant also produced large quantities of radioactive cesium in the lifetime much longer: 58 million billion becquerels, or about three times less than Chernobyl. Cesium-137 has a half life of thirty years, it remains today 98% of its initial radioactivity in the environment, a rate that will still be 81% in 2020, said Didier Champion, director of the crisis at the IRSN . "The initial contamination related to the accident has declined substantially. That does not mean that there are more, far from it. Today, for many years, we are in a state of chronic contamination of the environment and sustainable ", says Mr. Champion. "There are risks of chronic exposure to low doses but one that can accumulate over time if we do not take care," he adds, stressing the need to follow the contamination of a number of foods such as fruits, milk, mushrooms, game and fish.

UNCERTAINTIES IN POPULATION EXPOSURE

A total of approximately 24,000 km2 of Japanese contaminated by cesium-137, only 600 km2 today exceed the threshold of 600,000 becquerels per m2, estimated IRSN. "A contamination level equal relative areas in Japan are much lower than in contaminated areas around Chernobyl, which is explained by the fact that much of the waste [...] was dispersed in over the Pacific, "according to this assessment. However, there are contaminated land in "leopard spots" up to 250 km away from the center, with "hot spots" associated with highly localized accumulation of radioactive deposits by rainfall and runoff. As for health effects, no direct victim of the nuclear accident has so far been reported, but many uncertainties remain concerning the potential exposure of populations but also on the doses received by employees of the operator of the Central, Tepco, and relief on the spot.

Source (in French) : Le Monde

投稿日:2012-05-09