Alpha.particle (a particle) Average dose.......... Background radiation Beta particle (B particle).. Biological model....... Body burden....... Controlled area.. Critical organ... Curie, the (c.)--. Millicurie (mc.) – Microcurie (uc.) Micromicrocurie (μμc.) Megacurie (Mc.) APPENDIX 16 GLOSSARY Helium nucleus; i.e., a close combination of two neutrons and two protons, and therefore positively charged. Alpha particles are emitted from the nuclei of certain radioactive elements. The arithmetic mean radiation dose. The average may be taken with respect to time, number of people, location, etc. Radiation which is extraneous to that originating from a particular source under study. The term also is sometimes used to denote radiation from naturally occurring sources. (See Natural background radiation.) Swiftly moving electrons or positrons, and therefore negatively or positively charged respectively, when emitted by radioactive substances. A mathematical expression or other scheme which is devised to represent the functioning and interrelationship of biological processes. The amount of a specified radioactive material or the summation of the amounts of various radioactive materials in a person's body at the time of interest. The context usually clarifies which meaning is intended. (See Maximum permissible body burden, Organ burden.) A defined 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 implies that a controlled area is one that requires control of access, occupancy, and working conditions for radiation protection purposes.) An organ or tissue most affected by ionizing radiations from the deposition of a specified internal emitter or from external sources. The essentiality of the organ and its sensitivity to ionizing radiations are considered in determining the critical organ. Measure of the activity (rate of disintegration or decay) of a radioactive substance. More specifically, that quantity of a radioactive nuclide decaying at a rate of 3.7× 1010 atoms per second or 2.2×1012 atoms per minute. One-thousandth of a curie. One-millionth of a curie. One-millionth of a microcurie, or one-million millionth of a curie. One million curies. Dose___ Dose-effect relationship............ Dosimeter.. Exposure.. Accidental.... Environmental_ External... Internal... Localized... Medical... Nonoccupational__ Occupational........ Whole Body. Gamma rays (y rays) Half-life... GLOSSARY--Continued The dictionary definition is not appropriate in radiation protection. Definitive practice requires that the term be used in such combining forms as radiation dose, absorbed dose, whole body dose, partial body dose, etc.. Where the context has established the specific meaning intended, it is common practice to use the term "dose" without repeating the modifier. Comprehensive discussion of the use of the term "dose" is contained in such reference documents as MDDC-1100 and CRUSP-1.1 (See Radiation dose.) The magnitude of a specific biological effect, expressed as a function of the radiation dose producing it. It is frequently repre sented as a curve described as a doseeffect curve, dose-effect response curve, or dose response curve. Any of several devices used for measuring dose and dose rate from various ionizing radiations. Often used in the sense of being made subject to the action of radiation. Unplanned, unintended exposure to ionizing radiations. A short-term, planned exposure to ionizing radiations in excess of long-term maximum permissible limits as a result of unusual circumstances. Exposure to natural and artificially produced sources of ionizing radiation beyond the boundaries of the controlled area. The exposure of body tissues to ionizing radiations originating from sources outside the body. The exposure of body tissues to ionizing The exposure to ionizing radiations of a small Exposure of individuals to ionizing radiations Exposure of an individual to ionizing radiations by reason of his work. Literally, the exposure to the whole body. Electromagnetic waves of very short wavelengths produced during the disintegration of radioactive elements. The time taken for the activity or for the total number of atoms-of a radioactive nuclide to decay or disintegrate to one-half of the initial value. 1 Cantril, S. T., and Parker, H. M. "The Tolerance Dose," MDDC-1100. Argonne National Laboratory, Jan. 5, 1945. Parker, H. M. "Some Background Information on the Development of Dose Units,” ́ORUSP-1. American College of Radiology. November 1955. Half-life-Continued Effective half-life_ GLOSSARY-Continued By analogy, the time taken for the total number of atoms of a nuclide to be reduced to one-half of the initial value by biological removal processes (of the body). Radioactive decay is not involved. By analogy and combination, the time taken for the total number of atoms of a radioactive nuclide to be reduced to one-half of the initial value by combined radioactive decay and biological removal processes from the body. Average life or mean life............... A particular atom can decay now, later, or Isotopes.. 1 Internal emitters. Natural background radiation___ Neutron.... Fast neutron___ Slow neutron_-_ Thermal neutron Nuclide 3 NOTE.U235 is a nuclide. never. The average or mean life expectancy of a number of the same radionuclides is a definite quantity, however, and is equal to 1.4 times the half-life. Atoms of the same element, i.e., having the same atomic number, but of differing atomic weight are called isotopes of that element. The isotopes of an element are almost identical in chemical properties, and in all physical properties except those determined by the mass of the atom. The different isotopes of an element contain different numbers of neutrons in their nuclei. Nearly all elements found in nature are mixtures of several isotopes. Radionuclides contained within the body. An atom or aggregate of atoms, which is not electrically neutral, viz, negative ion, positive ion. In certain circumstances an electron may be described as a "negative ion." Ionizing radiations from naturally occurring radionuclides as they exist in nature plus cosmic radiation. An uncharged nuclear particle of approximately the same mass as a proton. A neutron having an energy between 10 Kev. and 10 Mev. A neutron of low energy. The upper limit of energy is often taken as 1 ev. A neutron in termal equilibrium with its surroundings. At 15° C., the mean energy is about 0.025 ev. An atom of a particular species; that is, characterized by an atomic number and an atomic weight. Uranium as it occurs naturally consists pri marily of two nuclides, 92U235 and 92U238, which together bear the relationship of isotopes. Organ burden... Organ dose Per-capita dose_ The quantity of a radionuclide in a particular The radiation dose received by a particular A nuclear particle of unit mass number hav- Radiation (ionizing). Rad Rep.-- Roentgen, the (r.) GLOSSARY-Continued Radiation capable of producing ions in a medium. Examples are X- and gamma rays, alpha and beta radiation, and cosmic radiations are examples of ionizing radiation. The unit of absorbed dose (of radiation) in An older unit, now replaced by the rad. NOTE. The absorbed dose (in tissue) expressed in rad, multiplied by the RBE (q.v.) for the type of radiation concerned, gives the biologically effective dose in rem. Relative biological effectiveness (RBE). Radiation effect.. Clinical.. Congenital... Somatic_ Radioactivity.. Radionuclide. Strontium unit (SU). Working limit__ For Defined in the note above. For X- and A response or change induced by exposure A change of sufficient magnitude that it can be recognized by a trained observer or measured by laboratory tests. A change which affects the foetus and exists at the time of birth. A change in a reproductive cell which would alter the characteristics of an individual produced from the affected cell or which causes a mutation that is inheritable by subsequent generations. A change produced in any tissue which alters the normal body processes of the irradiated individual. The property or process whereby certain elements or nuclides spontaneously emit particles and/or gamma rays by the disintegration of the nuclei of their atoms. A radioactive nuclide. ex A hypothetical individual characterized by |