MOSCOW, August 6 (RIA Novosti) - Measures to further reduce the ongoing effects of the Fukushima Daiichi nuclear disaster include decontamination work in surrounding areas with realistic targets to lower radiation exposure doses, Japanese newspaper Yomiuri Shimbun reported.
“The government has set a long-term decontamination goal of reducing individuals’ annual radiation exposure to 1 millisievert or lower, equivalent to 0.23 microsievert or less in terms of air dosage per hour,” the newspaper reported, explaining the Japanese Environment Ministry’s plan.
The measurement of air contamination tends to vary so the ministry needs to make decontamination plans based on measurements of individuals’ radiation exposure. Measurements recently taken in Fukushima Prefecture reveal areas where air contamination exceeded by more than two times the 0.6 microsievert per hour target, and far more than the long-term goal of 1 millisievert per year, said to be an unrealistic target.
Applying air doses uniformly would be an impractical approach and relying on the 1-millisievert benchmark would inevitably delay reconstruction of the affected areas, the newspaper reported.
“The 20-millisievert limit is also set as a condition to lift evacuation orders in the aftermath of the nuclear power plant accident. But many displaced residents assume they will not be able to return home unless the exposure dose falls to 1 millisievert or lower,” the article reported.
The International Atomic Energy Agency said that an annual dose of up to 20 millisieverts is considered tolerable. Currently, the Miyakojimachi district of Tamura city is the only area surrounding the Fukushima-1 nuclear power plant to have its evacuation order lifted. Kawauchi village in Fukushima Prefecture was expected to have its evacuation order lifted in July, but was postponed due to fear that radiation doses were still too high in certain areas.
In 2011 the Japanese Environment Ministry released a plan proposing 960 square miles of land affected by the Fukushima Daiichi nuclear disaster undergo decontamination to reach an annual radiation exposure limit of 5 millisieverts.
According to Forbes magazine the average person receives roughly 2.4 millisieverts of radiation exposure a year. Radiation is emitted from many sources including cosmic rays, X-rays, brazil nuts, granite and smoking cigarettes.