Chapter I.  General Provisions

(Basic Principle of Prevention of Ionizing Radiation Hazards)

Article 1.  The employer shall endeavour to minimize the exposure of workers to ionizing radiation as low as possible.

(Definition, etc.)

Article 2.  "Ionizing radiation" (hereafter called "radiation") as set forth by this Ordinance shall be defined as the following particulate rays and electromagnetic waves:

(1)  Alpha-rays, deuteron-rays and proton-rays

(2)  Beta-rays and electron-rays

(3)  Neutron-rays

(4)  Gamma-rays and X-rays

2.  In this ministerial ordinance, "radioactive substances" shall be defined as radioactive isotopes (hereinafter referred to as "radioisotopes"), their compounds and the substances containing the radioisotopes which fall under any one of the following categories, except those in a solid state with a concentration of 74 Bq/g or less and those in a hermetically sealed state with a volume of 3.7 MBq or less.

(1)  Radioactive substances with one kind of radioisotope: Any substance falling within one of the categories given in the left column of the following table and in quantity equal to or exceeding the quantity given in the right column of the same table corresponding to the category concerned.

(2)  Radioactive substances comprising two or more kinds of radioisotopes: Those which respectively come within the categories given in the left column of the table in the preceding item and in quantities the sum of the respective ratios of which to the quantities corresponding to their respective categories given in the right column of the same table is 1 or more.

3.  The types of "radiation work" provided for by this Ordinance correspond to those listed in Attached Table 2 of the Enforcement Order of Industrial Safety and Health Law (hereafter called "the Cabinet Order").

4.  The "radioactive substances" as established by the Ministry of Health, Labour and Welfare Ordinance based on item 4 of Attached Table 2 of the Cabinet Order correspond to those provided in paragraph 2.