Pertinent information concerning the Fukushima Dai-ichi NPS accident
Radioactive exposure
Review of radiation exposures

The status of radiation doses from the accident to the end of December, 2011 for the workers engaged in emergency work at Fukushima Dai-ichi NPS is that there were approximately 19,600 people who entered the site and were exposed to approximately 11.55 mSv on average. There were 167 workers exceeding 100 mSv. Among them six workers exceeded 250 mSv of a dose limit.

TEPCO has been evaluating exposures dose of the workers continuously Periodic updates are available for downloading from TEPCOfs web site at http://www.tepco.co.jp/en/press/corp-com/release/index-e.html.

Example of radiation exposure

 On March 24, 2011
It was confirmed that two out of three workers involved in work for laying electric cables on the first and basement floors of the turbine building of Unit 3 had radioactive materials attached to their leg skin when stepping into puddles of radioactive water wearing low-cut shoes. It has been reported that there was exposure exceeding 170mSv by this work.
Although TEPCO decontaminated their exposed skin, it was decided that there was a possibility of beta ray burns, and the two workers were transported to Fukushima Medical University Hospital.
On March 25, 2011 all three workers including the two that were exposed to the puddle were transported to an independent administrative institution, the National Institute of Radiological Sciences (NIRS). Immediately after their arrival, NIRS performed checkups, etc.
The workers were also re-examined on April 11, 2011 for follow-ups and it was confirmed that these three workers were not suffering any health issues.

 On April 27, 2011
TEPCO has confirmed that the effective exposure dose from January 1st, 2011 to March of a female employee who has been in the restoration work after the accident is about 18 mSv, which is in excess of statutory dose limits of 5 mSv over a period of 3 months. Moreover, some of the people engaged in work were not designated as radiation workers.
For this reason, NISA gave a strict warning to TEPCO, and instructed it to investigate the cause of the exposure, to develop measures to prevent any recurrence, to verify the management system for radiation control in Fukushima Dai-ichi NPS, and to develop appropriate countermeasures based on their findings.
On May 1, 2011 it was confirmed that other one female worker was also exposed by about 7.5 mSv which exceeds the dose limit.
With regard to the female employees, TEPCO has confirmed by a medical diagnosis that there is no impact on her health.

 Radiation exposure exceeding 250mSv
Six persons of Tokyo Electric power Company were exposed in the Fukushima Nuclear Accident exceeding 250mSv of a dose limit immediately after the accident (Max. 678.8mSv). They are shift operators and members of maintenance team and were working at the Main Control Room etc. The followings are assumed to be causes for their intake of radioactive materials. Medical diagnosis was conducted by medical expert, and no medical impact was observed.
(1)Under the rapidly developing situation, it was extremely difficult to take appropriate measures like choosing, wearing and distributing appropriate mask.
(2)In order to bring the extraordinary situation under control, workers had to work for a long time in Main Control Room. Therefore, they had to eat in Main Control Room (room for night shift).
(3)As for the worker wearing glasses, there was a space between the mask and temple arm of the glasses.
(4)Some workers were working near the emergency door at Main Control Room (door to the outside), the area that was assumed to have had high density of aerial radioactive substances. Therefore, it was not possible to response to the unforeseeable event such as the explosion at roof part of reactor building for Unit 1.
(5)Some workers made small space between their face and mask for a while to have air to remove their fog on the glasses in order to perform the work safely.