Exposure data wrong for 16,000 in Fukushima


Fukushima Prefecture and the National Institute of Radiological Sciences have said they erroneously estimated the radiation exposure of 16,118 people in a survey covering the first four months after the outbreak of the March 2011 disaster at the Fukushima No. 1 nuclear plant.

Among the roughly 420,000 people authorities have so far finished compiling data on, recalculations show 12,469 received higher doses and 3,649 lower doses than previously estimated.

The margins for revisions range from plus 0.4 millisievert to minus 0.2 millisievert. As a result of the revisions, it was learned that some people were exposed to more than 1 millisievert — the annual limit set by the government for ordinary citizens.

People polled were asked to answer in detail where they were between March 12 and July 11, 2011.

Based on their whereabouts, the institute estimated their cumulative amount of external exposure by adding up daily radiation levels measured at their locations over the four months.

Used as reference were actual radiation readings at a number of monitoring posts in the prefecture as well as projections of the spread of radioactive substances by the SPEEDI computer simulation system.

But in some cases, the dates in the survey failed to match those in the reference data.

  • williambanzai7

    Isn’t it interesting that the estimates are always predominantly low ball?


    • Andrew Stuart Jonson Daniels

      The margin is pretty negligible. The difference is about the difference you can get from living in one area or another from normal background radiation.

      • SF99

        Exposure to any additional radiation is never negligible.

        All and any radiation can be a potential source of cancer or DNA damage.

      • Starviking

        And and if the risk of the additional radiation causing cancer is very low, then the additional exposure is negligible.

      • Andrew Stuart Jonson Daniels

        no, thats utterly untrue. We get radiation all day long nonstop, we also get radiation from eating bananas, potatoes and many other things. None of this harms us. Radiation at a low level causes no damage at all. Your cells are designed to deal with low levels of radiation below 100 mSV. Below this level causes zero damage at all, It has no link to cancer at all, not even at 1 in a million rate. Its actually zero, not a tiny fraction.
        I know credible people have repeated “any amount of radiation of dangerous” as information but it has no grounding at all in science.

    • Starviking

      Not really, if the date error resulted in swapping a later date, and so lower radiation reading, with an earlier one then the low ball estimate is entirely understandable.

  • Alan Remick

    Why is this even news? There were insignificant errors in only 20,000 of
    420,000 cases. That’s less than 5%. Statistically, I would say they did
    pretty good.

    And, one millisievert is insignificant anyway.