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Press Releases 2013

Press Release (Jul 05, 2013)Revisions in "Exposure Dose Distribution" Following Reconfirmation Work on Internal Exposere Doses at Fukushima Daiichi Nuclear Power Station

We so far have been evaluating the exposure doses of the workers at Fukushima Daiichi Nuclear Power Station by evaluating the exposure doses of our employees and aggregating the evaluation results obtained from the respective contractor companies. The results of such evaluation are not only subimitted at each month end to the Ministry of Health, Labour and Welfare (MHLW) but also announced publicly.

With regard to the evaluation results in terms of internal exposure dose, it was found out that results obtained through calculation and elvaluation based on data owned by TEPCO differ from results (adopted values) obtained through evaluation based on detailed surveys conducted by the respective cooperative companies. Accordingly, MHLW carried out reconfirmation on the validities of the data and the internal exposure dose evaluation methods.

The reconfirmation work carried out by MHLW on the internal exposere doses was completed recently, and data revised based on the revision instructions given by MHLW to the contractor companies were submitted to us. Today (July 5, 2013), we submitted to MHLW the exposure dose distribution tables reflecting the thus revised data. (Attachment 1)

In addition, these revisions to the internal exposure doses necessitate revisions to the Reports on Radiation Control for the fiscal years 2010 and 2011, which were already submitted. Today, we reported the Nuclear Regulation Authority about the necessary revisions.

32 TEPCO employees are included among people whose internal exposure doses were revised this time. These TEPCO workers are people whose internal exposure dose evaluation was finalized at the relatively early stage. In accordance with the latest instructions from MHLW, evaluation of the internal exposure doses of these people was changed to evaluation in which radioacvtive material intake of each person is supposed to have been acute intake occurred on the day when the person started working. Further, the nuclides covered by the evaluation were revised.(Attachment 2)

We have not found significant internal intakes since October 2011. However, if any significant internal intake is found, we will refer to the instructions from MHLW, and cooperate with the cooperative companies in their evaluation work as we have done, so that we will further enhance the radiation control at Fukushima Daiichi Nuclear Power Station.

1. Revaluation results of internal exposure dose (PDF 11.1KB)PDF
2. Revisions in Internal Exposure Dose Evaluation of TEPCO Workers (PDF 22.4KB)PDF
3. Method of internal dose estimations for workers at Fukushima Daiichi Nuclear Power Station (PDF 330KB)PDF
3-1. New version of 2/Aug/2011 document for easier comprehension (Posted on January 7, 2014) (PDF 654KB)PDF

Attachment 1 and 2 are available only in Japanese. We apologize for the inconvenience this may cause.

On Aug 7, 2013, some parts in the document (Attachment 3) were revised for expression improvement.

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