Dose Statistical Data Based on the Information Registered with the System of Registration and Management of Radiation Exposure Doses for Decontamination and Related Work (2021)
Radiation Dose Registration Center
1. Release of statistical data
The Radiation Dose Registration Center of the Radiation Effects Association (“RADREC” below) assigns and registers an individualized registration number (personal identification number) in RADREC to each worker engaged in decontamination and related work who works in areas of primary contractors that join the System of Registration and Management of Radiation Exposure Doses for Decontamination and Related Work (“Decontamination Registration and Management System” below); RADREC then carries out systematic regulatory control over the workers’ radiation exposure doses; even if workers move to different areas to engage in other decontamination and related work, the system allows RADREC to know each worker’s dose correctly, because the primary contractors who join the Decontamination Registration and Management System register workers’ doses at all sites.

Based on the registration information, RADREC has released the statistical data that represent the radiation control status for workers engaged in radiation work such as decontamination and related tasks.

The statistics below are based on the dose data of decontamination and related work conducted during 2021 and registered in the Decontamination Registration and Management System.

2. Data compilation method
The statistical data, based on doses of workers engaged in decontamination and related work carried out by primary contractors that have joined the Decontamination Registration and Management System, are compiled by RADREC.
(1) These statistical data are based on registered data provided by the primary contractors that carried out decontamination work and the like in the special decontamination area (decontamination of soil and related work, work for collecting waste, etc. and work for handling designated contaminated soil and waste), work under a designated dose rate, and work for disposing nuclear accident-derived waste both inside and outside the special decontamination area as of 16 May 2022.
(2) The compiled doses are the effective doses, i.e., the total of both external exposure and internal exposure doses.
(3) The statistical data for Dose Distribution by Age of Workers for Decontamination and Related Work, etc., Dose Distribution by Gender of Workers for Decontamination and Related Work, etc., Dose Distribution by Number of Engaged Projects in One Year and Traditional Dose Distribution by Number of Engaged Projects in the Last Five 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, doses before the date of enforcement of that ordinance (1 January 2012) are handled assuming that these are due to exposure to radiation on 1 January 2012, according to the guidelines for applying the ordinance.
(4) It should be noted that Dose Distribution by Area was not handled according to the procedure specified in the guidelines above; rather, it is shown as the actual dose in 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 Work and Guideline on Prevention of Radiation Hazards for Workers Engaged in Work under a Designated Dose Rate
【Dose limits for decontamination and related work】
The exposure dose limit for workers is set at 100 millisieverts (mSv) over five years and 50 mSv in one year. The dose limit for female workers (excluding those who indicate no possibility of pregnancy and those who are pregnant) is strictly set at 5 mSv over Four months. “Five years” refers to the statutory period that started on 1 January 2012 and will be renewed every subsequent five years.

3．Definition of terminology
(1) Ionization Radiation Ordinance The Ordinance on Prevention of Ionizing Radiation Hazards. .
(2)
 Ionization Radiation Ordinance for Decontamination Ordinance on Prevention of Ionizing Radiation Hazards at Works to Decontaminate Soil and Waste Contaminated by Radioactive Materials Resulting from the Great East Japan Earthquake and Related Works． the Great East Japan Earthquake and Related Works
(3) Decontamination Workers Workers who are engaged in “decontamination works and related works” and Workers who are engaged in decontamination and related work who operate under the designated dose rate as defined in the Ionization Radiation Ordinance for Decontamination and disposal work of accident-derived waste, etc., as defined in the Ionizing Radiation Ordinance.
(4) Quarterly Exposure Dose Exposure doses (preliminary values) of decontamination workers recorded in RADREC accumulated in each quarterly period of a calendar year （1 January to 31 December）.
(5) Annual Exposure Dose Exposure doses of decontamination workers recorded in RADREC accumulated in a calendar year （1 January to 31 December）.
(6) Five-year Exposure Dose Exposure doses accumulated in the statutory five-year period to ensure that long-term dose limits are observed. The first period started on 1 January 2012, with exposure doses accumulating every subsequent five years. Dose data for the present five-year period have been compiled from 2017 to 2021 inclusive.
(7) Number of Engaged Projects in a Year The number of projects that the workers for decontamination and related work were engaged in during the period of statistical data compilation (2021). Even if a worker was engaged in radiation work at one decontamination project several times in a given year, that counted as only one project.
Even if a worker was engaged in radiation work at one decontamination project in several times in a year, that counted as only one project.
(8) Number of Engaged Projects in Five Years The number of projects that workers for decontamination and related work were engaged in during the period of statistical data compilation (2017 to 2021 inclusive). Even if a worker was engaged in radiation work at one decontamination project several times in this period, that counted as only one project.
Even if a worker was engaged in radiation work of one decontamination project in several times in this period, that counted as only one project.
List of statistical data of doses
１．Dose Distribution by Age of Workers for Decontamination and Related Work ｛2021｝ (Table)
２．Dose Distribution by Age of Workers for Decontamination and Related Work ｛2021｝ (Figure)
３．Dose Distribution by Gender of Workers for Decontamination and Related Work｛2021｝ (Table)
４．Dose Distribution by Number of Engaged Projects in One Year｛2021｝ (Table)
５．Dose Distribution by Number of Engaged Projects in One Year ｛2021｝ (Figure)
６．Traditional Dose Distribution by Number of Engaged Projects in the Last Four Years｛2017-2021｝ (Table)
７．Dose Distribution by Area ｛2021｝ (Table)
８．Dose Distribution by Area ｛2021｝ (Figure)

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