Ministry of Health, Labour and Welfare


Producing and Offering Graphic Presentations of Dose Statistical Data Based on the Information Registered with the System of Registration and Management of Radiation Exposure Doses for Decontamination and Related Works (2014)

Radiation Dose Registration Center

1.Release of statistics

The Radiation Dose Registration Center of the Radiation Effects Association (hereinafter referred to as the Radiation Dose Registration Center “RADREC”) assigns and registers a registration number (personal identification number) in “RADREC” to each worker engaged in decontamination and related works, etc. who works at work areas of employers of decontamination and related works that join the System of Registration and Management of Radiation Exposure Doses for Decontamination and Related Works (hereinafter referred to as “Decontamination Registration and Management System”), and then performs the systematic registration control over radiation exposure doses of the workers (hereinafter referred to as “dose”). Thereby, even if workers for decontamination and related works, etc. move to different work areas to engage in other decontamination and related works, the system allows RADREC to know each worker’s dose correctly because the employers who join the decontamination registration and management system have registered workers’ doses at all work sites.

Based on the registered data, RADREC has released statistical data that represent the radiation control status for workers engaged in decontamination and related works, etc. at the work areas of decontamination and related works.

The released statistics below are those based on the dose data of the decontamination and related works etc. conducted during 2014 which were registered into the decontamination registration and management system.

Please visit the RADREC website where quarterly dose distributions can be seen as preliminary figures, in addition to the statistics of the doses shown here.

2.Data compilation method

The statistics are those of doses of the workers for decontamination and related works, etc. in work areas of decontamination and related works of the employers of decontamination and related works that have joined the “Decontamination Registration and Management System”, compiled by the RADREC.

(1)
These statistics are based on registered data provided by employers engaged in decontamination works etc. in the special decontamination areas as of 8 June 2015 (“decontamination of soil and related works”, “works for collecting wastes, etc. ” and “works for handling designated contaminated soil and wastes”), works under a designated dose rate, and works to dispose of the accident-derived wastes and othersinside and outside of the special decontamination areas.
(2)
The compiled doses are the effective doses which are the total of the external exposure dose and the internal exposure dose.
(3)
The compiled radiation exposure doses in each of the categories “dose distribution of the workers for decontamination and related works, etc. by age”, “dose distribution of the workers for decontamination and related works, etc. by gender”, “dose distribution of the workers for decontamination and related works, etc. by number of engaged project in a year”, and “transitional dose distribution of the workers for decontamination and related works, etc. by number of engaged projects in the latest three years” correspond to the annual dose limit and five-year dose limit specified in the Ionizing Radiation Ordinance for Decontamination. In compiling these radiation exposure doses, in accordance with the procedure to handle doses for controlling the exposure dose limits (i.e., exposure doses during the period from 11 March 2011 to 31 December 2011 shall be summed as exposed dose on 1 January 2012)* specified in the guidelines for applying the Ionizing Radiation Ordinance for Decontamination issued from the Ministry of Health, Labour and Welfare, these doses were summed to those in 2012.
It should be noted that “the doses of the workers for decontamination and related works, etc. by area” were not handled according to the procedure specified in the guidelines above but shown as the actual dose of each year because it is not related to the annual or five-year exposure dose limit control specified in the guidelines above.
*
“Guideline on Prevention of Radiation Hazards for Workers Engaged in Decontamination and Related Works” and “Guideline on Prevention of Radiation Hazards for Workers Engaged in Works under a Designated Dose Rate”
(4)
Included in the compilation are dose data registered into the decontamination registration and management system during the year of concern (From 1 January to 31 December of the year) among those registered at the time of compilation.
Annual exposure doses:
Exposure doses of workers engaged in decontamination and related works, etc. accumulated in a calendar year (from 1 January to 31 December of the year).
Five-year exposure doses:
Exposure doses accumulated for the statutory five-year period to control the five-year exposure dose limit. The period started on 1 January 2012 and the exposure doses will be accumulated every subsequent five years.
Transitional doses:
Exposure doses accumulated up to the end of each year during the five-year period stipulated in the law.(Here, the exposure doses of 3 years in 2012, 2013, and 2014 were totaled.)
(5)
“Maximum exposure dose”, “total exposure dose”, “ mean exposure dose” and “%” were calculated by rounding to one decimal place. This procedure may result in the totals in the table not matching up or the total percent values not being 100.
(6)
The ages of the workers engaged in decontamination and related works, etc. in the statistics of 2014 were based on the Western style of calculating age as of 31 December 2014.
(7)
The data were compiled based on the registration number in RADREC (the personal identification number). Except in the dose distribution by area, exposure doses were accumulated by name for the compiled term (annual and five-year periods) in the statistics. For the dose distribution by area, doses were accumulated by name for each area, and thus in the case where a worker was engaged in work in two areas in a year, the worker was counted as two persons.
(8)
(8) The number of engaged projects in a year shows the number of projects where workers for decontamination and related works, etc. were engaged during the period (calendar year) when the statistical data were compiled.

3.Exposure dose limits for workers for decontamination and related works, etc.

The exposure dose limit for workers for decontamination and related works, etc. is set at 100 mSv per five years and 50 mSv per one year. The dose limit for female workers (excluding those who are diagnosed with no possibility of pregnancy, and those who are pregnant) is set at 5 mSv over 3 months as well as the above mentioned dose limit conditions.

[Definition of terminologies]

(1)
Workers for decontamination and related works, etc.: Workers engaged in decontamination and related works, workers engaged in works under a designated dose rate, and workers who are engaged in the disposal of accident-derived wastes and others.
(2)
Employers of workers engaged in decontamination and related works: Employers who assign workers to decontamination and related works, works under a designated dose rate, or disposal of accident-derived wastes and others.
(3)
Ionizing Radiation Ordinance for Decontamination: Ordinance on Prevention of Ionizing Radiation Hazards at Works to Decontaminate Soil and Wastes Contaminated by Radioactive Materials Resulting from the Great East Japan Earthquake and Related Works (Ordinance No. 152 of MHLW, 2011)

4.Statistics of doses in 2014

1.
Dose Distribution of Workers for Decontamination and Related Works, etc. by Age (2014) (Table)
2.
Dose Distribution of Workers for Decontamination and Related Works, etc. by Age (2014) (Figure)
3.
Dose Distribution of Workers for Decontamination and Related Works, etc. by Gender (2014) (Table)
4.
Dose Distribution of Workers for Decontamination and Related Works, etc. by Number of Engaged Projects in a Year (2014) (Table)
5.
Dose Distribution of Workers for Decontamination and Related Works, etc. by Number of Engaged Projects in a Year (2014) (Figure)
6.
Transitional Dose Distribution of Workers for Decontamination and Related Works, etc. by Number of Engaged Projects in the Latest Three Years (2012-2014) (Table)
7.
Dose Distribution of Workers for Decontamination and Related Works, etc. by Area (2014) (Table)
8.
Dose Distribution of Workers for Decontamination and Related Works, etc. by Area (2014) (Figure)

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