Ministry of Health, Labour and Welfare


15 April 2015
Radiation Employer Dose Registration Center
Radiation Effects Association

Office for Radiation Protection of Workers
Industrial Health Division
Occupational Safety and Health Department
Labour Standards Bureau
Ministry of Health, Labour and Welfare

Director’s Office for Decontamination
Environment Management Bureau
Ministry of the Environment

Press Release

Statistics on Radiation Exposure Doses of Decontamination Workers and Other Items Have Been Announced

Recently, statistics on the radiation exposure doses of decontamination workers and other items registered during the period from 2011 to 2014 in the system of registration and management of radiation exposure doses for decontamination and related works (operated by the Radiation Effects Association) were compiled and announced to the general public.


[System of registration and management of radiation exposure doses for decontamination and related works]
Employers of decontamination workers are required by law (1) to conduct radiation control activities and to preserve radiation exposure dose records and other information of the decontamination workers (2) . As a private measure for ensuring observation of the law, the system was established by employers and other involved parties who have entered into decontamination work contracts to register and control radiation exposure doses of individual workers with this Radiation Effects Association acting as a registration center. This system started operation on 15 November 2013.


(Note 1)    The Ordinance on Prevention of Ionizing Radiation Hazard at Works to Decontaminate Soil and Wastes Contaminated by Radioactive Materials Resulting from the Great East Japan Earthquake and Related Works (Ordinance of the Ministry of Health, Labour and Welfare, 2011 No. 152, hereafter referred to as "Ionizing Radiation Ordinance for Decontamination") and the Ordinance on Prevention of Ionizing Radiation Hazards (Ordinance of the Ministry of Labour, 1972 No. 41, hereafter referred to as "Ionizing Radiation Ordinance").

(Note 2)    Workers who are engaged in "decontamination work and related works" and "works under the designated dose rate" defined in the Ionizing Radiation Ordinance for Decontamination, and "disposal works of accident-derived waste, etc." defined in the Ionizing Radiation Ordinance.


Overview of statistics of exposure doses registered in the system of registration and management of radiation exposure doses for decontamination and related works.


The statistics below show the total numbers of workers, dose distribution, and mean doses based on the exposure doses registered by 30 March 2015 by the employers (3) of decontamination workers in the special decontamination areas.


1    Quarterly dose distribution (preliminary figures) (Tables 1-1, 1-2, 1-3, 1-4)
The numbers of workers tended to increase quarterly. The mean dose was the highest (0.8 mSv) for the period of January–March 2012, and then remained almost steady at 0.2 mSv-0.3 mSv after October–December 2012.
  • (1) 2011; The numbers of workers ranged from 2 to 1,212 persons, and their mean doses were 0.0 - 0.2 mSv.
  • (2) 2012; The numbers of workers ranged from 1,589 to 6,286 persons, and their mean doses were 0.1-0.8 mSv.
  • (3) 2013; The numbers of workers ranged from 6,715 to 14,710 persons, and their mean doses were 0.2-0.3 mSv.
  • (4) 2014; The numbers of workers ranged from 10,576 to 17,988 persons, and their mean doses were 0.2-0.3 mSv.


2    Dose distribution by age (4) (Tables 2-1, 2-2)
The distributions of numbers of workers by age had peaks for work age groups of 55-59 and 60-64 in both 2012 and 2013; however the mean doses were almost the same at about 0.5 mSv irrespective of the age.
With regard to the dose distribution according to calendar years, the percentage of workers whose dose exceeded 5 mSv decreased from 1.5% in 2012 to 0.2% in 2013 while the percentage of workers whose dose exceeded 1 mSv increased from 9.7% in 2012 to 14.6% in 2013.
  • (1) The total number of workers was 11,058 in 2012 (Mean dose: 0.5 mSv; Max. dose: 13.9 mSv)
  • (2) The total number of workers was 20,564 in 2013 (Mean dose: 0.5 mSv; Max. dose: 6.7 mSv).


3    Dose distribution by gender of workers (4) (Tables 3-1, 3-2)
The percentages of female workers to male workers were low, being 2.4% in 2012 and 2.6% in 2013, and the mean doses were slightly lower for female workers than for male workers.
  • (1) 2012; Among 11,058 workers in total, the number of male workers was 10,794 (97.6% of the total number; Mean dose: 0.5 mSv; Max. dose: 13.9 mSv), and the number of female workers was 264 (2.4% of the total number; Mean dose: 0.2 mSv; Max. dose: 1.4 mSv).
  • (2) 2013; Among 20,564 workers in total, the number of male workers was 20,030 (97.4% of the total number; Mean dose: 0.5 mSv; Max. dose: 6.7 mSv), and the number of female workers was 534 (2.6% of the number; Mean dose: 0.4 mSv; Max. dose: 2.9 mSv).


4    Dose distribution by the number of the engaged projects (4) (Tables 4-1, 4-2)
  • (1) The percentage of workers who were engaged in two or more projects increased from 8.4% in 2012 to 24.0% in 2013. The maximum number of projects that any workers had been engaged in was five.
  • (2) The mean doses tended to increase with the number of engaged projects. The highest doses were observed in the workers who had been engaged in five projects; 2.2 mSv in 2012, and 1.4 mSv in 2013.


5    Dose distribution by the number of the engaged projects during the statutory five years
(Evaluated period: 2012-2013) (4) (Table 5)
  • (1) According to the data in 2012-2013, the percentage of the workers who were engaged in two or more projects was 22.9%, and the maximum was seven projects.
  • (2) The mean doses tended to increase with the number of the engaged projects. The highest dose was 2.6 mSv for the workers who had been engaged in six projects.


6    Dose distribution by areas (5) (Tables 6-1, 6-2, 6-3)
The numbers of workers increased in 2013 by a factor of six to eleven compared to the numbers in 2012. The largest increase was seen in the southern part (Zone C).
The mean doses were 1 mSv or less in both 2012 and 2013, and for all areas. The largest mean dose was 0.8 mSv in Zone A in 2012.
In 2013, the number of workers was the largest in the southern part (Zone C) and the mean doses were 1 mSv or less for all areas. The highest mean dose was seen in Zone A.
  • (1) 2011 (only in the special decontamination areas); The numbers of workers ranged from 226 to 530, and their mean doses were 0.1-0.3 mSv.
  • (2) 2012 (only in the special decontamination areas); The numbers of workers ranged from 2,578 to 5,501, and their mean doses were 0.2-0.8 mSv.
  • (3) 2013 (only in the special decontamination areas); The numbers of workers ranged from 5,547 to 9,337, and their mean doses were 0.4-0.7 mSv.


(Note 3)    The employers who are involved in the treatment of accident-derived waste both in the special decontamination area and outside of the special decontamination area were included in these statistics.

(Note 4)    The doses before the date of enforcement of the Ionizing Radiation Ordinance for Decontamination (1 January 2012) are handled assuming that these are due to exposure to radiation on 1 January 2012, according to the guidelines on decontamination and related works, so that it would be a conservative evaluation. It should be noted that the data in 2014 are not fixed yet.

(Note 5)    The employers who are involved in the treatment of accident-derived waste both in the special decontamination area and outside of the special decontamination area were included in these statistics.

Attachment

Statistics of Radiation Exposure Doses of Decontamination Workers and Other Items PDF 1,432KB

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