5 July 2013
Office for Radiation Protection of Workers
Industrial Health Division
Occupational Safety and Health Department
Labour Standards Bureau
Office for Radiation Protection of Workers
Industrial Health Division
Occupational Safety and Health Department
Labour Standards Bureau
Press Release
Results of Re-evaluation of Committed Dose of Emergency Workers ¹
at the TEPCO Fukushima Daiichi Nuclear Power Plant
| 1. | The Ministry of Health, Labour and Welfare (MHLW) has noticed that there were significant discrepancies between internal dose assessments of emergency workers made by TEPCO and those reported by primary contractors, doses which were reported to MHLW in April 2013. MHLW conducted a re-evaluation of internal dose assessments from May 2013, and concluded that some of the internal dose assessments should be adjusted. The overview of the re-evaluation is as follows. |
Overview of Re-evaluation of Internal Dose Assessments
1 Purpose and Principle
| (1) | MHLW made a comparison between internal dose assessments made by TEPCO and those by primary contractors, and investigated causes of the discrepancies; and readjusted the committed doses as necessary. | |
| (2) | In carrying out the re-evaluation, MHLW has promoted standardization of methodologies of internal dose assessments to avoid underestimates of doses as much as reasonably achievable. |
| 2 | Readjustment of committed doses of 479 workers (2.5% of the 20,000 emergency workers) |
| (1) |
Readjustment of committed doses based on the standardized method
|
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| (2) |
Correction of miscalculated committed doses (29 workers)
|
| 2. |
MHLW has demanded that TEPCO and primary contractors employ the standardized methodologies for
internal dose
assessments; all parties were strictly instructed to prevent the recurrence of miscalculations
and errors related
to internal dose assessments.
Furthermore, in accordance with the readjusted committed dose, MHLW will carry out the health care of the emergency workers based on the MHLW Minister’s guidelines. |
Supplemental Data
(1) Increased number of emergency workers who were exposed at 50mSv to 100mSv
- 12 workers at 2 contractors (1.7% increase compared with 723 workers prior to the readjustment)
- Range: 3.2mSv to 36.2mSv (internal dose), average 13.4mSv
- Range of readjusted effective doses from 51.4mSv to 65.19mSv
- Reason: Changes of intake date and intake scenario
(2) Increased number of emergency workers who were exposed at more than 100mSv
- 6 workers (3 at TEPCO and 3 at contractors) (3.6% increase compared with 167 workers prior to the readjustment)
- Range: 7.39mSv to 48.91mSv (internal dose), average 21.3mSv
- Range of readjusted effective doses from 101.83mSv to 148.78mSv
- Reason: Change of intake date
1 This refers to workers for whom the emergency exposure dose limits (100mSv: current limit, 250mSv: 14 March to 16 December 2011 limit) were applied.
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