Chapter III.  Protection against External Radiation

(Cylinders for Irradiation, etc.)

Article 10.  When an employer uses X-ray equipment, as listed in item 33 of Article 13 of the Cabinet Order (hereafter called specified X-ray equipment) of those (which generate X-rays, and correspond to those other than X-ray equipment as provided by item 2 of Attached Table 2 of the Cabinet Order, the same as in the following), he shall use the irradiation cylinder or diaphragm by which the vertical angles of the irradiation areas in the form of a cone in which X-rays are stationed at its apex are made narrower than the angles necessary for actual irradiation for carrying out of radiation work, provided that this does not apply in respect to the case in which the use of the said irradiation  cylinder or diaphragm may prevent the said specified X-ray equipment from being properly employed for adequate irradiation.

2.  The employer shall make the irradiation cylinders and diaphragm provided by the preceding paragraph conform to the standards established by the Minister of Health, Labour and Welfare.

(Filtering Boards)

Article 11.  When the employer uses specified X-ray equipment, he shall use filtering boards for use in it, provided that this does not apply in respect to a case in which the use of soft X-rays is required owing to the nature of work, or a case in which there is no possibility that workers who engage in the said work may be subjected to soft X-rays.

(Measures for Fluorography)

Article 12. In carrying out fluorography by using specified X-ray equipment, the employer shall take the following measures. However, this shall not apply in the case of using specified X-ray equipment that has a shielding structure so that the whole or part of the body of the worker engaged in fluorography work does not enter the exposure field during X-ray irradiation.

(1)  With respect to the distance between the X-ray tube and the focal receiving equipment used, the X-ray radiation field shall not exceed the reception area (in case the reception area is circular and the X-ray radiation field is rectangular, the size which circumscribes the reception area).

(2)  For fluorography X-ray equipment for mass chest fluorography and specified X-ray equipment other than for medical use (hereinafter referred to as "industrial use"), the primary protection shield of the receiving equipment shall limit the free-air air-kerma at a distance of 17 cm from the possible contact surfaces of the equipment (referred to as the "air-kerma" in the next item) to 1.0 microgray or less per scan.

(3)  For fluorography X-ray equipment for mass chest fluorography and specified X-ray equipment for industrial use, box-shaped shielding shall be installed surrounding the irradiated object, and the air-kerma at a distance of 10 cm from the shielding shall be 1.0 microgray or less per scan.

2.  Notwithstanding the provisions of the preceding paragraph, the employer may not take the measures listed for any of the following items.

(1)  Pursuant to the provisions of the conditional clause in paragraph 1 of Article 15, measures specified in items 2 and 3 of the preceding paragraph in case of using specified X-ray equipment at places other than a radiation equipment room.

(2)  Measures specified in item 3 of the preceding paragraph in the event any worker engaged in fluorography work can easily be evacuated to a site as prescribed in paragraph 1 of Article 3-2.

(Measures for Direct Radioscopy)

Article 13. In carrying out direct radioscopy by using specified X-ray equipment, the employer shall take the following measures. However, this shall not apply in the case of using specified X-ray equipment that has a shielding structure so that the whole or part of the body of the worker engaged in the work of direct radioscopy does not enter the exposure field during X-ray irradiation.

(1)  The installation of equipment that makes it possible for worker engaged in direct radioscopy to stop the generation of X-rays, or be shielded from the same, from the present position of the operator.

(2)  The installation of an automatic device that will immediately open the X-ray tube circuit in the event the current to the X-ray tube exceeds twice the rated current for the tube.

(3)  With respect to the distance between the X-ray tube and the focal receiving equipment used, the X-ray radiation field shall not exceed the reception area (in case the reception area is circular and the X-ray radiation field is rectangular, the size which circumscribes the reception area).

(4)  The air-kerma rate in the air of X-rays that pass the receiving equipment in the cone (hereinafter referred to as the "air-kerma rate") shall be limited to 150 microgray/h or less at a distance of 10 cm from all possible contact surfaces of the receiving equipment in the cone in the case of specified X-ray equipment for medical use, and to 17.4 microgray/h or less at a distance of 1 m from the focal point of the X-ray tube with respect to specified X-ray equipment for industrial use, etc.

(5)  The air-kerma rate of the X-rays that pass any section that exceeds 3.0 cm from the maximum irradiation field at the time of direct radioscopy shall be limited to 150 microgray/h or less at a distance of 10 cm from all possible contact surfaces of the same section with respect to specified X-ray equipment for medical use, and to 17.4 microgray/h or less at a distance of 1 m from the focal point of the X-ray tube with respect to specified X-ray equipment for industrial use, etc.

(6)  The installation of appropriate equipment to effectively shield any surface surrounding the irradiated object from other X-rays emanating from than cone.

2.  Notwithstanding the provisions of the preceding paragraph, the employer may not take any of the following measures with respect to any of the situations described below.

(1)  Measures prescribed under item 2 of the preceding paragraph in the event of installing a timer that keeps a running total of elapsed radioscopy time and issues a warning sound, etc., when a given length of time is exceeded during radioscopy.

(2)  Under the provisions of the conditional clause in paragraph 1 of Article 15, measures specified in items 4 through 6 of the preceding paragraph in the event of using any specified X-ray equipment at places other than a radiation equipment room.

(Posting of Notice)

Article 14.  The employer shall make up notices for the equipment or the machines listed in the left column of the following table to indicate the matters correspondingly listed in the right column of the same table according to their classifications and post each of such notices on or near the corresponding equipment or machine where the notice can be seen easily.

(Radiation Equipment Room)

Article 15.  The employer intending to install the equipment or the machines listed hereunder (hereinafter referred to as "radiation equipment") shall provide an exclusive room (hereinafter referred to as "radiation equipment room") for installation except in the cases where the radiation equipment to be installed is covered with a shield capable of restricting the 1 cm dose equivalent rate due to external radiation to 20 μ Sv/hour or less at the outside, where the radiation equipment has to be moved from one place to another for use and where installing the radiation equipment stationary in an exclusive room severely hinders the effective use of the equipment or causes substantial inconvenience for the operator of the equipment.

(1)  X-ray equipment.

(2)  Charged particle accelerator.

(3)  Equipment for removing gases from X-ray tubes or kenotron, or for inspecting these devices from which X-rays are generated.

(4)  Equipment loaded with radioactive substances.

2.  The employer shall put up notices which indicate a radiation equipment room at the entrance of the said rooms.

3.  The provision of paragraph 4 of Article 3 shall be applied with necessary modification to the radiation equipment room.

Article 16.  Deleted

(Warning Devices, etc.)

Article 17.  In the events listed hereunder, the employer shall notify the persons concerned to that effect. In notifying the said events, however, the notification shall be made by means of an automatic alarm system except in the cases where the radiation equipment has to be used in any place other than the radiation equipment room, where the X-ray equipment with the tube voltage of less than 150 kV is to be used and where the radiation equipment to be used is loaded with radioactive substances of less than 370 GBq in quantity.

(1)  When the power is supplied to the X-ray equipment or charged particle accelerator.

(2)  When the power is supplied to testing equipment for removing gases from X-ray tubes or kenotrons, or for inspecting these devices.

(3)  When radiation equipment loaded with radioactive substances is in operation to emit the radiation.

2.  The employer shall install an interlock to the entrance, where persons regularly enter from such entrance, to the radiation equipment room where the charged particle accelerator or the equipment loaded with radioactive substances of more than 111 TBq is installed.

(Entry Prohibited)

Article 18.  When the X-ray equipment (restricted to those for fluorography in the case of medical X-ray equipment) or the equipment loaded with radioactive substances has to be used at any place other than the radiation equipment room, conforming to the proviso of paragraph 1 of Article 15, the employer shall prohibit workers from entering within 5 m from the focal point of the X-ray tube or the radiation source (not including places where the effective dose due to external radiation is 1 mSv/week or less) except in the cases of the entries of the workers for the preparatory work for removing the radiation source from the radiation source container, inspection of the radiation source and other necessary work, providing that the radiation source is securely contained in the radiation source container where the radiation source container, and the shutters, if provided in the said container, have closed.

2.  The provisions of the preceding paragraph shall apply mutatis mutandis to cases in which the employer uses medical-use X-ray equipment for X-ray photography at places other than a radiation equipment room. In such a case, the term "5 m" in the paragraph shall be read as "2 m."

3.  The provisions of paragraph 2 of Article 3 shall apply mutatis mutandis to the calculation of the effective dose due to external radiation as prescribed in paragraph 1 (including cases in which the provisions of the preceding paragraph are applied; the same shall also apply in the case of the following paragraph).

4.  The employer shall put up notices which state the prohibition or stop the workers from entering into places in accordance with the provision of the paragraph 1, at the places concerned or in their vicinity.

(Measures for Transmissive Photography)

Article 18-2.  When the employer uses specified X-ray equipment or gamma-ray radiation equipment for transmissive photography (which correspond to the ones used for transmissive photography, same as in the following) at the places other than the radiation equipment rooms (excluding the case in which there is no possibility that the workers are exposed to radiation) in compliance with the proviso of paragraph 1 of Article 15, the radiation shall be emitted in a direction to the places out of which said workers enter, or measures shall be taken by which to shield the X-rays for the said radiation.

(Taking out of Radiation Sources, etc.) 

Article 18-3.  When the employer uses gamma-ray radiation equipment for transmissive photography, he shall not take radiation sources out of the radiation source containers unless he uses source carrier devices (composed of operation devices (devices which send out and wrap up wire-release), operation tubes (tubes into which the wire-releases are guided) and also transmission tubes (tubes into which the radiation sources and wire-releases are guided, same as hereinafter) to take the radiation sources out of the containers and to place the radiation sources in the said containers, same as hereinafter).

2.  Notwithstanding the provision of the preceding paragraph, the employer may take out the radiation source from the container using a remote controller other than the radiation source carrier devices when using gamma-ray radiation equipment for transmissive photography inside radiation equipment room.

Article 18-4.  When the employer uses gamma-ray radiation equipment with the source carrier devices, he shall comply with the provisions as given below.

(1)  The movement of the said transmission tubes shall be made after the radiation sources have been placed securely in the said radiation source containers, and after the shutters, if provided in the said radiation source containers, have closed properly.

(2)  The employer shall make the angles of the apex of the cone formed by X-rays radiated narrower than those necessary for the purpose of the actual radiation with the said equipment, and make the exposure rate of gamma rays, which are radiated covering areas other than those covered by the said cone, minimized by means of collimators, etc., provided that this does not apply in respect to the case in which the purposes or aims of the said equipment are markedly hindered when using the said collimators, etc.

(Periodical Voluntary Inspection)

Article 18-5.  The employer shall make voluntary inspection of gamma-ray radiation equipment for transmissive photography periodically at least once a month in terms of the items as given below, provided that this does not apply in respect to the case in which the said equipment not used for periods of time which are longer than a month is not required to be inspected for the said period of time.

(1)  The presence or absence of abnormalities in the shutters of radiation source container and devices thereby to open and shut the said containers, and also in the shutters.

(2)  The presence or absence of abnormalities in the devices thereby to fasten the holder of radiation sources.

(3)  For those that have source carrier devices, the presence or absence of abnormalities in the connecting portion between said devices and the radiation source container.

(4)  The presence or absence of abnormalities in the source carrier devices and in the remote-control devices thereby to adjust the locations of radiation sources, if provided.

2. The employer shall make inspection of the equipment, as set forth in the proviso of the preceding paragraph in terms of each of the items of the same paragraph, before resuming the use of this equipment.

Article 18-6.  The employer shall make voluntary inspection of the gamma-ray radiation equipment used for transmissive photography periodically at least once every six months in terms of the presence or absence of abnormalities in the performance thereby to shield the radiation source containers, provided that this does not apply in respect to cases in which the equipment which has not been used for periods of time which are longer than six months is not required to be subjected to the said inspection for the said periods of time.

2.  The employer shall make voluntary inspection of the equipment as set forth in the proviso of preceding paragraph in terms of the presence or absence of abnormalities in the performance thereby to shield radiation source containers before resuming the use of this equipment.

(Recording)

Article 18-7.  When the employer carries out voluntary inspection as stated in the preceding two Articles, he shall record the items as given below and shall keep the record in custody for the period of three years.

(1)  Date of inspection.

(2)  Method of inspection.

(3)  Parts of equipment inspected.

(4)  Results of inspection.

(5)  Names of those who carry out the inspection.

(6)  The contents of measures such as repair, etc., if taken on the basis of the results of the said inspection.

(Checkup)

Article 18-8.  When the employer first uses gamma-ray radiation equipment for transmissive photography, when the employer repairs or improves the said equipment after the said equipment has been dismantled, or when the employer replaces previous radiation sources by new ones, he shall make a checkup in terms of each item of paragraph 1 of Article 18-5 and of the presence or absence of abnormalities in the performance thereby to shield the radiation source containers.

(Repair, etc.)

Article 18-9.  When the employer has periodic voluntary inspection as provided by Article 18-5 or Article 18-6 or a checkup as set forth in the preceding Article, he shall quickly make the repair of abnormalities, if found, or assume other measures for countering the abnormalities.

(Placement of Radiation Sources)

Article 18-10.  When the employer has workers engage in work to place the radiation sources into their containers or the other containers in the case in which there occur the accidents set forth in item 4 of paragraph 1 of Article 42, he shall assume measures thereby to shield the said radiation sources and shall also have the workers use forceps, etc., to provide proper distance between the said workers and the radiation sources.

(Checkup of Radiation Sources) 

Article 19.  When the employer uses the equipment provided with radioactive substances by moving them, he shall make a checkup, using radiation measuring instruments, in terms of whether the radiation sources has been lost or is missing, leaking out, or spilling out, and also of whether radiation sources are securely placed in the radiation source containers, if provided in the said devices, and also of whether the shutters, if provided in the radiation source containers, are securely closed immediately just after the said equipment have been used, and also when they are put into the storage place after the daily work.

2.  In a case in which confirmation is made of a loss or missing, leakage or spilling of radiation sources, radiation sources being not placed securely in the radiation source containers, and the non-or half-closure of shutters of the radiation source containers, the employer shall look for the lost or missing radiation sources, repair the said container, or assume measures necessary for prevention of health impairment of the workers concerned.

Articles 20 and 21. (Deleted)