Chapter II. Controlled Area, Limit and Measurement of Dose

(Indication of a Controlled Area, etc.)

Article 3.  An employer whose business involves radiation work (hereinafter referred to as the "employer" except in the case of Article 62) shall demarcate the area (hereinafter referred to as the "controlled area") that falls under any of the following by posting a sign.

(1) The area in which the total of the effective dose due to external radiation and the effective dose due to radioactive substances in the air may exceed 1.3 mSv quarterly.

(2) The area in which the surface density of a radioactive substance may exceed one-tenth of the limit listed in the Attached Table in this ordinance.

2.  The calculation of the effective dose due to external radiation as prescribed in item 1 of the preceding paragraph shall be carried out the 1 cm dose equivalent.

3.  The calculation of the effective dose due to radioactive substances in the air as prescribed in item 1 of paragraph 1 shall be carried out by multiplying 1.3 mSv by the equivalent of one-tenth of the average limit for three months as designated by the Minister of Health, Labour and Welfare of the average concentration of radioactive substances in the air during the working hours in a week (in the event the number of working hours in a week exceeds 40 hours or is less than 40 hours, the value used shall be obtained by multiplying the average concentration of radioactive substances in the air during the number of working hours in a week by the value obtained by dividing said working hours by 40 hours; hereinafter referred to as the "weekly average concentration")

4.  The employer shall not allow persons other than those with business there to enter the controlled area.

5.  The employer shall post signs concerning the requirement to wear the radiation measuring instrument specified in paragraph 3 of Article 8, warnings concerning the handling of radioactive materials and the necessary emergency measures in the event of an accident, etc., to be taken to prevent health hazards to workers due to radiation in an easily visible location in the controlled area.

(Limit of Dose in Facilities, etc.)

Article 3-2. With respect to any radiation equipment rooms in paragraph 1 of Article 15, working rooms for handling radioactive substances in paragraph 2 of Article 22, storage facilities in paragraph 1 of Article 33 or disposal-by-storage facilities in paragraph 1 of Article 36, the employer shall limit the total of the effective dose due to external radiation and the effective dose due to radioactive substances in the air equivalent to 1 mSv or less per week at such sites that are usually entered by workers by installing shielding walls, protective screens or other shielding devices, or by installing local exhaust ventilation system or equipment which seals the emission source of gas, vapour or dust of radioactive substances.

2. The provisions of paragraph 2 of the preceding Article shall apply mutatis mutandis to the calculation of the effective dose to external radiation as prescribed in the preceding paragraph.

3. The calculation of the effective dose due to radioactive substances in the air as prescribed in paragraph 1 of this Article shall be carried out by multiplying 1mSv by the weekly average concentration limit ratio designated by the Minister of Health, Labour and Welfare under the provisions of paragraph 3 of the preceding Article.

(Dose Limit for Radiation Workers)

Article 4.  The employer shall take the necessary measures to prevent workers engaging in radiation work in the controlled area (hereinafter referred to as "radiation workers") from being subjected to an effective dose not exceeding 100 mSv during 5years and  not exceeding 50 mSv/year.

2.  Notwithstanding the provisions of the preceding paragraph, the employer shall take the necessary measures to ensure that the effective dose for the female radiation workers (excluding those who can not become pregnant and those specified by Article 6) does not exceed 5 mSv quarterly.

Article 5.  The employer shall take the necessary measures to ensure that the equivalent dose of radiation workers does not exceed 150 mSv/year for the eye lens and 500 mSv/year for the skin.

Article 6. The employer shall take the necessary measures to ensure that pregnant female radiation workers shall not be exposed to a dose that exceeds the value set in each of the following items for the period from the diagnosis of pregnancy to childbirth (hereinafter referred to as "during pregnancy"), as prescribed in the following dose classifications.

(1)  1 mSv for the effective dose due to internal exposure.

(2)  2 mSv for the equivalent dose exposure to the surface of the abdomen.

(Dose Limit in Emergency Work)

Article 7. When carrying out emergency work to protect workers from health hazards due to radiation (hereinafter referred to as "emergency work") in the event of an accident that falls under any of the items of paragraph 1 of Article 42, and in which an area as prescribed in the same paragraph is generated, notwithstanding the provisions of paragraph 1 of Article 4, and of Article 5, the employer may allow male radiation workers and female radiation workers (who can not become pregnant) to be exposed to doses that exceed the limit prescribed in such paragraphs.

2. In the event of any procedures under the preceding paragraph, the exposure dose during any such emergency work shall not exceed the value set in the following items as prescribed for each of the classifications below.

(1) 100 mSv for the effective dose.

(2) 300 mSv for the equivalent dose exposure to the eye lens.

(3) 1 mSv for the equivalent dose exposure to the skin.

3.  The provision of the preceding paragraph shall be applied to  male workers and female workers (who can not become pregnant) who engage in emergency work.

(Measurement of Dose)

Article 8.  The employer shall measure the dose equivalent due to external exposure and the dose due to internal exposure in the controlled area for radiation workers, emergency workers and workers who enter the controlled area temporarily.

2.  The dose due to external exposure provided for in the preceding paragraph shall be measured by the unit of 1 cm dose equivalent and 70 μm dose equivalent (in case of neutron radiation, 1 cm dose equivalent), providing that the measurement carried out using the radiation measuring instrument attached to the parts of the body specified in item 3 of the following paragraph in accordance with the provisions of the same paragraph shall be made by the unit of 70 μm dose equivalent.

3.  The measurement of the dose due to external exposure provided for in paragraph 1 shall be made by attaching radiation measuring instrument to the parts of the body designated in the following items, providing that the dose may be calculated based on the dose equivalent rate measured by a radiation measuring instrument where measurement using radiation measuring instrument is extremely difficult, and also the same may be determined by calculation only where the application of the former method is also extremely difficult.

(1)  Chest for male workers and female workers who can not become pregnant, and abdominal area for other female workers.

(2)  Part most likely to be exposed to radiation out of the head, neck, chest, upper arm, abdominal area and thigh (excluding cases where the parts most likely to be exposed to radiation for male workers and female workers who can not become pregnant are the chest and upper arm and cases where the same for other female workers are the abdominal area and the thigh).

(3)  Part most likely to be exposed to radiation (excluding neutron-rays), providing that such part is other than the head, neck, chest, upper arm, abdominal area and thigh.

4.  The measurement of the dose due to internal exposure under the provisions of paragraph 1 shall be conducted at least quarterly (at least monthly for female workers, whose effective dose exposure may exceed 1.7 mSv in any single month (except for female workers who can not become pregnant) and female workers during pregnancy), for workers who enter sections of the controlled area where there is a possibility of taking in radioactive substances either by inhalation or oral. However, in case said person mistakenly intakes a radioactive substances either by inhalation or oral, the measurement shall be conducted as soon as possible after such intake either by inhalation or oral.

5.  In measuring the dose due to internal exposure under the provisions of paragraph 1, the measured value shall be determined by the method designated by the Minister of Health, Labour and Welfare.

6.  Radiation workers, emergency workers and workers who enter the controlled area temporarily shall wear radiation measuring instrument , except for cases specified in the proviso of paragraph 3.

(Checking and Recording Measurement of Dose Results)

Article 9.  The employer shall check the results of the measurement of the dose due to external exposure under the provisions of paragraph 1 of the preceding Article daily for those workers who are suspected to be exposed to radiation exceeding 1 mSv/day in terms of the 1 cm dose equivalent.

2.  The employer shall calculate and record the dose of radiation exposure for radiation workers listed in each of the following items without delay by using the methods designated by the Minister of Health, Labour and Welfare on the basis of the measurement and/or calculation results under the provisions of paragraphs 3 or 5 of the preceding Article, and keep such records for at least 30 years. This provision shall not apply in the event an employer turns over such records to an organization designated by the Minister of Health, Labour and Welfare, after keeping them for a period of 5 years.

(1)  Quarterly, annual and 5-year totals of the effective dose for male workers and female workers (who can not become pregnant) (quarterly and annual totals of the effective dose for workers whose effective dose did not exceed 20m Sv/year in the past five years).

(2)  Monthly, quarterly and annual totals of the effective dose for female workers (except those who can not become pregnant) (quarterly and monthly totals for those with no possibility of exceeding an effective dose of 1.7 mSv per month).

(3)  Quarterly and annual totals of the tissue dose equivalent by human tissue.

(4) Monthly and the during-pregnancy totals of the effective dose due to internal exposure and the equivalent dose exposure to the abdomen of female workers during pregnancy.

3.  The employer shall, without delay, inform each radiation workers of the dose specified in each item of the preceding paragraph based on the records under the provisions of the preceding paragraph.