Caesium fallout from Fukushima rivals Chernobyl
by Debora MacKenzie
29 March 2011
Radioactive caesium and iodine has been deposited in northern Japan far from the Fukushima Daiichi nuclear plant, at levels that were considered highly contaminated after Chernobyl.
The readings were taken by the Japanese science ministry, MEXT, and reveal high levels of caesium-137 and iodine-131 outside the 30-kilometre evacuation zone, mostly to the north-north-west.
Iodine-131, with a half-life of eight days, should disappear in a matter of weeks. The bigger worry concerns caesium-137, which has a half-life of 30 years and could pose a health threat for far longer. Just how serious that will be depends on where it lands, and whether remediation measures are possible.
The US Department of Energy has been surveying the area with an airborne gamma radiation detector. It reports that most of the “elevated readings” are within 40 kilometres of the plant, but that “an area of greater radiation extending north-west… may be of interest to public safety officials”.