Definitions Relating to Ionizing Radiation

PURPOSE: This rule defines technical terms which are used throughout this chapter. PUBLISHER’S NOTE: The secretary of state has determined that the publication of the entire text of the material which is incorporated by reference as a portion of this rule would be unduly cumbersome or expensive. Therefore, the material which is so incorporated is on file with the agency who filed this rule, and with the Office of the Secretary of State. Any interested person may view this material at either agency’s headquarters or the same will be made available at the Office of the Secretary of State at a cost not to exceed actual cost of copy reproduction. The entire text of the rule is printed here. This note refers only to the incorporated by reference material. (1) Absorbed dose of any ionizing radiation is the energy imparted to matter by ionizing particles per unit mass of irradiated material at the place of interest. The unit of absorbed dose is the rad. (2) Aluminum equivalent is the thickness of aluminum affording the same attenuation, under specified conditions, as the material in question. (3) Controlled area is an area in which the occupational exposure of personnel to radiation or to radioactive material is under the supervision of an individual in charge of radiation protection. (This means that a controlled area is one that requires control of access, occupancy and working conditions for radiation protection purposes.) (4) Dead-man switch is a switch so constructed that a circuit-closing contact can only be maintained by continuous pressure by the operator. (5) Department is the Missouri Department of Health. (6) Dose, unless otherwise indicated, as used in these rules, means rem dose. (7) Effective half-life (T), in days, is— T=(Tb) × (Tr) (Tb) + (Tr) where Tb= biological half-life in days; and where Tr= physical half-life in days. (8) Excessive radiation dose is a dose of radiation in excess of the maximum permissible dose (19 CSR 20-10.040). (9) Individual is any human being. (10) Installation is a place containing one (1) or more sources of radiation. (11) Lead equivalent is the thickness of lead affording the same attenuation, under specified conditions, as the material in question. (12) Maximum permissible accumulated dose (MPAD) is the dose of radiation which, if accumulated during the lifetime of the individual, is not expected to cause observable bodily injury. (13) Maximum permissible dose (MPD) is the maximum rem dose that the body of an individual or specific parts of the body shall be permitted to receive in a stated period of time. (14) Person is any individual, partnership, association, corporation, firm, trust, estate, public or private institution, group, agency, political subdivision of this state and any legal successor, representative, agent or agency of them. (15) Personnel monitoring is the determination of the radiation dose received by an individual during the specified period. (16) Protective barrier is a barrier of attenuating materials used to reduce radiation exposure. (17) Qualified expert is an individual fitted by training and experience to perform dependable radiation surveys, to oversee radiation monitoring and to estimate the degree of radiation hazard. If the ability of a qualified expert is questioned, the department shall be the judge of his/her qualifications, in regard to which it may consider the testimony of other persons whom it deems expert. (18) Rad is the unit of absorbed dose and is equal to one hundred (100) ergs per gram. It is a measure of the energy imparted to matter by ionizing particles per unit mass of irradiated material at the place of interest. (19) Radiation is gamma rays and X-rays, alpha and beta particles, high-speed electrons, neutrons, protons, other nuclear particles and any other ionizing radiation, but not sound or radio waves or visible, infrared or ultraviolet light. (20) Radiation hazard is any condition that might result in the exposure of individuals to excessive radiation dose. (21) Radiation machine is any device that produces radiation when in operation. (22) Radioactive material is any material, solid, liquid or gas, that emits radiation spontaneously. (23) Relative biological effectiveness (RBE) is a numerical factor which is used to compare the effectiveness of absorbed dose of radiation delivered in different ways. The standard of comparison is X-ray or gamma radiation having a linear energy transfer in water of three (3) kev per micron. A list of RBE values of various kinds of radiation is given in Table 1, 19 CSR 20-10.110. (24) Rem is equal to the absorbed dose in rads multiplied by the appropriate RBE. (25) Roentgen is a unit of exposure dose of Xray or gamma radiation such that the associated corpuscular emission per 0.001293 gram of air produces, in air, ions carrying one (1) esu of quantity of electricity. (26) Sealed source is a quantity of radioactive material so enclosed as to prevent the escape of any radioactive material. (27) Source (of radiation) is a radiation machine or a quantity of radioactive materials. (28) Survey is the evaluation of actual or potential radiation or contamination hazards by or under the supervision of a qualified expert. (29) X-ray tube housing protective diagnostic-type is one that reduces the leakage radiation to a maximum of 0.10 roentgen in one (1) hour at a distance of one (1) meter from the tube target when the X-ray tube is operating at its maximum current and voltage. (30) X-ray tube housing protective therapeutic-type is a tube housing so constructed that the leakage radiation at a distance of one (1) meter from the target cannot exceed the rate of one (1) roentgen per hour and at a distance of five centimeters (5 cm) from any point on the surface of the housing accessible to the patient cannot exceed the rate of thirty (30) roentgens per hour when the tube is operated at its maximum current and voltage. (31) Useful beam is that part of radiation which passes through the window, aperture, cone or collimating device of the tube housing. (32) User is a person having administrative control over one (1) or more sources. (33) Other scientific and technical terms not specifically defined in this rule shall be used in accordance with the definitions in recommendations of the National Committee on Radiation Protection and Measurements as published in Handbooks of the National Bureau of Standards or the American Standard Association’s Glossary of Terms in Nuclear Science and Technology, with preference being in the order given. AUTHORITY: section 192.420, RSMo 1986.* This rule was previously filed as 13 CSR 5090.010. Original rule filed Nov. 9, 1964, effective Dec. 9, 1964. *Original authority: 192.420, RSMo 1963.