information about Fukushima published in English in Japanese media info publiée en anglais dans la presse japonaise
6 Juin 2013
June 6, 2013
Radiation levels have dropped by 40 percent on average in each of the four types of evacuation zones around the crippled Fukushima No. 1 nuclear power plant, the government's nuclear watchdog said.
The Nuclear Regulation Authority said June 5 it used airborne radiation measurement data to estimate variations in air dose rates over the 17-month period from November 2011 to March 2013. It is the first time that the NRA has released such estimates by zoning category.
NRA officials attributed the decrease partly to physical decay and partly to rainwater washing radioactive materials into the ocean.
The Fukushima nuclear disaster was triggered by the Great East Japan Earthquake and tsunami in March 2011.
In the "difficult-to-return zones," where evacuees are not allowed to return for at least five years counting from March 2012, the average radiation level fell from 14.5 microsieverts per hour to 8.5 microsieverts per hour. The annual dose estimates in November 2011 exceeded 100 millisieverts in 27 percent of the land area of the difficult-to-return zones, but that ratio had dropped to only 6 percent by March 2013.
The average dose rate declined from 5.7 microsieverts per hour to 3.4 microsieverts per hour in the "no-residence zones," where evacuees are expected to be able to return in a few years.
In the "zones preparing for the evacuation order to be lifted," where evacuees are expected to be able to return sooner, that figure dropped from 2.0 microsieverts per hour to 1.1 microsieverts per hour.
The average radiation level fell from 2.7 microsieverts per hour to 1.5 microsieverts per hour in the "planned evacuation zone," a high-risk zone to the northwest of the plant and outside the 20-kilometer radius that is yet to be reclassified into any of the three other categories
http://mainichi.jp/english/english/newsselect/news/20130606p2g00m0dm037000c.html
TOKYO (Kyodo) -- Areas most seriously contaminated by the 2011 Fukushima Daiichi nuclear power plant disaster saw the size of high-level radiation zones in March reduced to less than one-fourth of the level of November 2011, the Nuclear Regulation Authority said Wednesday.
About seven months after the nuclear accident occurred, zones with radiation over 19 microsieverts per hour accounted for 27 percent of the total area that has been designated as "difficult to return to for at least five years."
But the proportion of the zones dropped to 16 percent as of June 28, 2012, and to 6 percent as of March 11 this year, according to aircraft monitoring surveys.
The government is expected to use the data in its planning to enable evacuees to return to their homes following the world's worst nuclear crisis since the 1986 Chernobyl disaster.
After the Fukushima Daiichi complex achieved a stable state of cold shutdown in December 2011, the government has been reclassifying evacuation zones to places designated as "difficult-to-return," or "habitation-restricted."
The difficult-to-return zones, which are defined as areas with radiation over 50 millisieverts per year, currently total about 320 square kilometers, excluding the 3-km radius from the plant.
The NRA also decided to further revise its nuclear disaster mitigation guidelines compiled in the wake of Fukushima crisis by adding details over the preparation of iodine tablets, which help prevent thyroid cancer.
In the guidelines, people living within a 5-km radius of a nuclear power plant will be given a supply of iodine tablets so they can promptly take the pills after an accident occurs.
Local governments are asked to purchase the tablets and conduct explanatory meetings to residents before distribution. Doctors will attend the meetings to explain about the side effects, the timing of taking the pills and other precautions.
Japan currently does not have iodine formula for infants that can be distributed ahead of time, so the NRA urges in the guidelines to evacuate infants before the plant's situation reaches a stage where citizens in general are asked to flee, an official said.
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