Ministry of Health, Labour and Welfare

Ministry of Health, Labour and Welfare

Overview of the Guidelines on Prevention of Radiation Hazards for Workers Engaged in Works under a Designated Dose Rate
(Labour Standards Bureau Notification No.0615-6, 15 June 2012)

(Note) Refer to "the Guidelines on the Prevention of Radiation Hazards for Workers Engaged in Decontamination Works" (Labour Standards Bureau Notification No.1222-6, issued on 22 December 2011) for decontamination works (*).

(*) It includes (a) works of decontamination, etc., (b) collection, transportation, or storage of the contaminated waste or removed soil (exceeding10,000Bq/kg of radioactive cesium), and (c) handling (excluding the soil decontamination and waste collection) of the designated contaminated soil and wastes (contaminated soil and wastes exceeding10,000Bq/kg of radioactive cesium), in the special decontamination areas and intensive contamination survey areas specified in the Act on Special Measures Concerning the Handling of Radioactive Pollution.


  1. Scope of application

    Works under a designated dose rate refer to the operations conducted in the special decontamination areas and intensive contamination survey areas specified in the Act on Special Measures Concerning the Handling of Radioactive Pollution, excluding decontamination works in locations where the average ambient dose rate exceeds 2.5μSv/h. The following items should be considered when applying these guidelines.

    • a) Works conducted indoors such as manufacturing are not subject to works under a designated dose rate if the average ambient dose rate inside the work sites is 2.5μSv/h or less even when the average ambient dose rate outside exceeds 2.5μSv/h.

    • b) Driving, loading, and unloading vehicles are considered as works under a designated dose rate only when: (i) the loading and unloading site (excluding loading operations concerning recovery efforts of local infrastructure) is in the location where the average ambient dose rate exceeds 2.5μSv/h, and workers are expected to stay at the site for over 40 hours per month to perform the loading and unloading operations, or (ii) conveyance of loads used for recovery efforts, especially those loads indispensable to rebuilding local infrastructure (e.g., construction machinery, construction materials, soil, and gravel) takes place at sites where the average ambient dose rate exceeds 2.5μSv/h.
      Note that only passing through the site where the average ambient dose rate exceeds 2.5μSv/h should not be subject to works under a designated dose rate because the stay duration is limited to a brief period.

    • c) The areas where the average ambient dose rate may exceed 2.5μSv/h due to the controlled radiation source such as an X-ray apparatus should be considered as the radiation controlled area specified in Paragraph 1, Article 3 of the Ionizing Radiation Ordinance.

  2. General Principles

    • (1) The employers of workers who are engaged in works under a designated dose rate should make every effort to minimize the ionizing radiation exposure to their workers.

    • (2) The employers, when implementing the works under a designated dose rate, should give top priority to minimizing radiation exposure to their workers (hereinafter referred to as the "workers under a designated dose rate") and strive to ensure that appropriate measures such as decontamination are taken at their work sites before commencing work.

      In light of the International Commission on Radiological Protection (ICRP) principles of justification, and considering the fact that the workers in manufacturing and business industries tend to receive higher radiation exposure doses from long working hours, and the urgency of their work is not necessarily pressing , employers should be required to minimize the radiation dose of their work sites and surrounding areas to the less than 2.5μSv/h level by decontamination in advance so that employees will be able to work in conditions without the need for radiation exposure dose control in principle.

  3. Workers subject to the radiation exposure dose control and the management of radiation exposure dose measurements

    • (1) The employers of workers under designated dose rate shall measure external exposure radiation doses of workers with personal dosimeters when assigning them to the operations.

    • (2) Given the difficulties in controlling radiation exposure doses for individual proprietors and self-employed workers, employers should enforce appropriate measures, such as decontamination, and prevent individual proprietors and self-employed workers from engaging in the works under a designated dose rate.

      • a. Individual proprietors or self-employed workers who are obliged to conduct works under a designated dose rate should be considered as workers engaged in works under a designated dose rate, and the present guidelines should be applied.

      • b. Volunteers should work at sites where the average ambient dose rate is 2.5μSv/h (approximately 5mSv/y when working 40 hours per week for 52 weeks) or less, and frequencies of their works should be limited to several dozen times (days) per year so that their effective exposure doses do not exceed 1mSv/y.

    • (3) The radiation exposure dose limits of workers should be 50mSv per year and 100mSv per 5 years. (It should be noted that the exposure dose limits for fertile female workers should be 5mSv per three months, and 2mSv on the abdominal surface for pregnant workers.)

      When the employers assign workers, who are engaged in radiation work or decontamination work in nuclear power plants and other sites, to works under a designated dose rate, they should ensure that the total effective exposure doses received by the workers during radiation work, decontamination work, and works under a designated dose rate do not exceed the limits stated above. If radiation exposure doses received from 1 January 2012 to 30 June 2012 are recorded, then those doses should be added to the exposure doses measured after 1 July 2012 to determine the value of radiation exposure used for radiation control.

    • (4) The employers of workers under a designated dose rate should investigate the exposure history of workers at the time of employment or transfer. If the worker had the exposure history, confirm the location, nature of work, duration, and other details concerning radiation exposure by referring to their exposure dose records issued by the previous employers. If they do not have the records, direct them to request reissuing of their records to the previous employers in order to manage radiation exposure doses specified in (3).

    • (5) The records of workers’ radiation exposure doses should be preserved for 30 years. The records can be transferred to the designated organizations after being kept for five years or when the workers engaged in decontamination works, etc. terminated employment. The employers should notify workers about their radiation exposure dose records.

    • (6) The employers of workers under a designated dose rate should issue copies of the records described in (5) to their workers when they terminate employment or when employers terminate their businesses.

    • (7) In order to appropriately manage radiation exposure control of fixed-term contract workers and temporary workers, the employers of workers under a designated dose rate are required to adhere to the following guidelines:

      • a. The employers should determine and record their radiation exposure doses every month when staffing fixed-term contract workers or temporary workers for a fixed period of less than three months.

      • b. At the end of contract periods, the employers should determine the total effective exposure doses received by these workers by combining all doses received during their contract periods and issue the copies of their records to these workers.

  4. Measures for reducing radiation exposure

    • (1) The employers who provide works under a designated dose rate should measure and record the results of the average ambient dose rate of their work sites prior to commencing work, and every two weeks thereafter as long as the sites are in their use.
    • (2) The employers of workers under a designated dose rate should promptly provide appropriate health services and consultation by medical doctors to their workers:(1)when workers accidentally inhaled or ingested radioactive materials derived from the nuclear accident or (2)when workers cannot reduce their levels of contamination to less than 40Bq/cm2 by washing themselves.

  5. Worker Education

    • (1) The employers of workers under a designated dose rate should provide the special education programs intended to enhance workers’ knowledge and understanding in the following areas:

      • a. The effect of ionizing radiation on human bodies and the methods of controlling radiation exposure doses
      • b. Radiation measurement methods
      • c. Relevant laws and regulations

    • (2) Ideally, the same special education programs should be provided to individual proprietors or self-employed workers, and volunteer workers.

    • (3) It is recommended that the contractee of the works under a designated dose rate ensures before placing the order that the needed number of workers who completed the special education programs can be secured by the commencement of the work.

  6. Healthcare measures

    • (1) The employers of workers under a designated dose rate should provide general medical examination to their full-time workers at the time of employment and once every year thereafter on a regular basis.

    • (2) The employers of workers engaged in decontamination works, etc. should create personal medical examination card and preserve the records for five years. The records can be transferred to the designated organization after being kept for five years or when the workers terminate employment.

  7. Safety and health control system

    • (1) The primary contractors who conduct works under a designated dose rate should appoint a radiation administrator who is responsible for unitary management including the duty of overseeing radiation exposure to workers who are affiliated with related subcontractors.

    • (2) The employers of workers engaged in works under a designated dose rate should appoint health managers or safety and health promoters, based on the size of work sites. These managers and promoters are expected to oversee technical issues associated with measuring radiation doses, recording the measurement results, educating the workers and healthcare measures. The appointment of health managers or safety and health promoters is recommended even to work sites where the number of workers is less than 10.

      Regardless the size of their work sites, employers should appoint a radiation manager who is responsible for measuring radiation exposure doses and recording the results of measurements.

    • (3) The employers of workers under a designated dose rate should take the following measures when assigning workers engaged in emergency work at the TEPCO Fukushima Daiichi Nuclear Power Plant to the works under a designated dose rate.

      • a. The employers should submit the following documents to the Industrial Health Division of the Ministry of Health, Labour, and Welfare as stipulated in Article 59-2 of the Ordinance on Prevention of Ionizing Radiation Hazards (hereafter referred to as the “Ionizing Radiation Ordinance”):
          (i) the copies of the personal medical examination cards described in 6 (1) above without delay after the medical examination
          (ii) the "status report on radiation dose control for the designated emergency worker" (Form No.3 of the Ionizing Radiation Ordinance) at the end of every three months

      • b. Provide health guidance and necessary examinations to workers who received radiation exposure doses exceeding 50mSv during emergency work in accordance with the "Guidelines on Maintaining and Improving Health of Emergency Workers at the TEPCO Fukushima Daiichi Nuclear Power Plant" (Public Notice No.5, 2011).

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