22-10-2012, 11:54 AM
Radiation effects from Fukushima Daiichi nuclear disaster
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ABSTRACT
The radiation effects from the Fukushima Daiichi nuclear disaster are the results of release of radioactive isotopes from the crippled Fukushima Daiichi Nuclear Power Plant after the 2011 Tōhoku earthquake and tsunami. Radioactive material has been released from the Fukushima containment vessels as the result of deliberate venting to reduce gaseous pressure, deliberate discharge of coolant water into the sea, and associated uncontrolled events. Concerns about the possibility of a large scale radiation leak resulted in 20 km exclusion zone being set up around the power plant and people within the 20–30 km zone being advised to stay indoors. Later, the UK, France and some other countries told their nationals to consider leaving Tokyo, in response to fears of spreading radioactive contamination.[3] The Fukushima incident has led to trace amounts of radiation, including iodine-131 and caesium-134/137, being observed around the world (New York State, Alaska, Hawaii, Oregon, California, Montreal, and Austria).[4][5][6] Large amounts of radioactive isotopes have also been released into the Pacific Ocean.
In March 2011, Japanese officials announced that "radioactive iodine-131 exceeding safety limits for infants had been detected at 18 water-purification plants in Tokyo and five other prefectures".[7]As of July 2011, the Japanese government has been unable to control the spread of radioactive material into the nation’s food. Radioactive material has been detected in a range of produce, including spinach, tea leaves, milk, fish and beef, up to 200 miles from the nuclear plant. Inside the 12-mile evacuation zone around the plant, all farming has been abandoned.[8][9]
As of August 2011, the crippled Fukushima nuclear plant is still leaking low levels of radiation and areas surrounding it could remain uninhabitable for decades due to high radiation. It could take “more than 20 years before residents could safely return to areas with current radiation readings of 200 millisieverts per year, and a decade for areas at 100 millisieverts per year”.[10]
The incidents are rated at level 7 rating on the International Nuclear Event Scale. The total amount of iodine-131 and caesium-137 released into the atmosphere has been estimated to exceed 10% of the emissions from the 1986 Chernobyl disaster.[11][12] Frank N. von Hippel, a U.S. scientist, has estimated that the release of radioactivity is about one-tenth that from the Chernobyl disasterand the contaminated area is also about one-tenth that that of Chernobyl; he also estimates “on the order of 1,000” people will die from cancer as a result of their exposure to radiation from the Fukushima Daiichi disaster.[13] However, other experts give lower estimates of deaths due to radiation exposure and, given that the radiation exposure resulting from the accident for most people living in Fukushima is very small compared to background radiation, it may be impossible to find statistically significant evidence of increases in cancer.[14]