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APPENDIX C GLOSSARY 10 CFR Part 61.55: Title 10, Part 61, Section 55 of the Code of Federal Regulations, Waste classification. These regulations were promulgated by the U.S. Nuclear Regulatory Commission. A/D ratio: The ratio of the activity (A) of a radiation source to the activity determined to define a threshold level of danger (D) in the International Atomic Energy Agencyâs radiation source categorization system. Absorbed dose: The quantity of ionizing radiation deposited into a material, including an organ or tissue, expressed in terms of the energy absorbed per unit mass of material. The basic unit of absorbed dose is the rad or its SI equivalent, the gray (Gy). Accelerator: A device that accelerates charged subatomic particles. Also called a particle accelerator, in the context of this report these devices are used to generate energetic beams of electrons that can be directed at an object that one wants to irradiate or at a tungsten, tantalum, or gold target, which converts the electron energy into x-rays that irradiate an object. Actinide: Any of a series of chemically similar radioactive elements with atomic numbers ranging from 89 (actinium) through 103 (lawrencium). This group includes uranium (atomic number 92), plutonium (atomic number 94), and americium (atomic number 95). Activity: The rate of decay of a radionuclide, more formally, the number of decays per time. Its SI unit is the becquerel (Bq) corresponding to one radioactive decay (disintegration) per second; its old unit, the curie (Ci), was originally defined as the activity of 1 gram of radium-226 or 3.7 Ã 1010 disintegrations per second. Acute effect: Effects in organisms manifest themselves soon after exposure to radiation and are characterized by inflammation, edema, denudation and depletion of epithelial and haemopoietic tissue, and haemorrhage. Acute radiation exposure: A radiation exposure that occurs over a relatively short period of time (e.g., seconds to hours). A chest X-ray is an acute radiation exposure. Agreement State: States that have assumed authority under Section 274b of the Atomic Energy Act to license and regulate by-product materials (radioisotopes), source materials (uranium and thorium), and certain quantities of special nuclear materials. Area-denial RDD: A radiological dispersal device (RDD) intended to contaminate an area such that the area cannot be occupied or used. Atomic number: The number of protons in the nucleus of an atom, and the number of electrons in a neutral atom. This number, sometimes referred to by the symbol Z, determines the atom's chemical element. A high-Z material has a high atomic number. 209
210 RADIATION SOURCE USE AND REPLACEMENT Becquerel (Bq): A unit of measure for activity. One becquerel is 1 disintegration (radioactive decay) per second. A gigabecquerel (GBq) is 109 Bq (1 billion becquerels) and a terabecquerel (TBq) is 1012 Bq (1 million million becquerels). Bremsstrahlung: Radiation emitted by the slowing down of light charged particles, such as the x rays produced when electrons from an accelerator are stopped in a metal target. By-product material: Defined by the Atomic Energy Act as radioactive material (except special nuclear material) yielded in or made radioactive by exposure to the radiation incident to the process of producing or using special nuclear material; and tailings or wastes produced by the extraction or concentration of uranium or thorium from any ore processed primarily for its source material content. Cancer incidence: Also known as the incidence rate. The rate of occurrence of cancer within a specified period of time per unit of population, for example, the number of cancers per year per 100,000 people. Cancer mortality: Also known as the mortality rate. The rate of death from cancer within a specified period of time per unit of population, for example, number of cancer deaths per year per 100,000 people. Carcinogenesis (induction of cancer): Manifested as a late stochastic somatic effect in the form of acute or chronic myeloid leukemia or some solid tumors, for example, in the skin, bone, lung, thyroid, or breast. Category 1 source: A radiation source that, if not managed safely or securely, could lead to the death or permanent injury of individuals in a short period of time. Category 2 source: A radiation source that, if not managed safely or securely, could lead to the death or permanent injury of individuals who may be in close proximity to the radioactive source for a longer period of time than for Category 1 sources. Category 3 source: A radiation source that, if not managed safely or securely, could lead to the permanent injury of individuals who may be in close proximity to the source for a longer period of time than Category 2 sources. Sources in Category 3 could, but are unlikely to, lead to fatalities. Chronic radiation exposures: Radiation exposures that occur over extended periods of time (e.g., months to years). Exposure to natural background is a chronic radiation exposure. Collective dose: The sum of all radiation exposures received by all members of a specified population. Compensatory measures: Measures beyond those required under existing U.S. NRC regulations. Through security orders, U.S. NRC required some licensees to implement compensatory security measures as conditions of their licenses. Curie (Ci): A unit of measure for activity equal to 3.7 Ã 1010 (37 billion) disintegrations (radioactive decays) per second. D-T reaction: See fusion. Decay product: A resultant particle from a radioactive disintegration. Depleted uranium: Uranium from which much of the uranium-235 has been removed.
GLOSSARY 211 Deterministic health effect: A tissue reaction that increases in severity with increasing dose, usually above a threshold dose, in affected individuals (organ dysfunction, fibrosis, lens opacification, blood changes, and decrease in sperm count). These are events caused by damage to populations of cells, hence the presence of a threshold dose. Dose: See Radiation dose. Dose rate: See Radiation dose rate. Effective dose: The equivalent dose averaged over all organs that accounts for the varying sensitivity of different organs and tissues to the biological effects of ionizing radiation. The effective dose has the same units as the equivalent dose. Equivalent dose: The absorbed dose averaged over the organ or tissue of interest multiplied by a radiation-weighting factor, wR, to account for the differences in biological detriment (harm) to an organ that result from differences in radiation type and energy for the same physical dose received by the organ. The SI unit of equivalent dose is sievert (Sv); the old unit is the rem. For x rays, gamma rays, and electrons, wR is 1; for protons, it is 5, for alpha particles, 20; and for neutrons, it ranges from 5 to 20 depending on neutron energy. Exposure: A metric based on the ability of photons to ionize air. Its old unit roentgen (R) is defined as charge of 2.58 Ã 10-4 C produced per kilogram of air. The SI unit of exposure is 2.58 Ã 10-4 C per kilogram of air. External exposure: An exposure received from a source of ionizing radiation outside of the body (NCRP, 2001). External cost: A cost from an action or economic transaction that is not included in the monetary cost of the activity or transaction and therefore is borne by parties not directly involved in the transaction. Fission: The splitting of a nucleus into at least two fragments, accompanied by the release of neutrons and energy. Fission of a nucleus may be initiated by absorption of a neutron or, in some materials such as californium-252, can happen spontaneously. Fusion: The joining together of two or more nuclei. The most commonly used fusion reaction is the deuterium-tritium reaction, also called the D-T reaction. Gamma ray: High-energy electromagnetic radiation. In this report, radiation emitted by decay of a radionuclide is always referred to as gamma radiation to distinguish it from radiation from an x-ray generator. Genetic or hereditary effects are radiation-induced mutations to an individualâs genes and DNA that can contribute to the birth of defective descendants. Graft versus host disease (GVHD): A rare but usually fatal complication of transfusion in which functional donor immune cells (T lymphocytes) attack the recipientâs tissues and the recipientâs immune system is unable to eliminate the donor lymphocytes. Greater-than-Class-C waste: Radioactive waste that contains concentrations of certain radionuclides above the Class C limits in 10 CFR Â§ 61.55. Ground shine: Radiation exposure from material deposited on the ground. Half-life: The time during which one-half of a given quantity of a radionuclide undergoes radioactive decay.
212 RADIATION SOURCE USE AND REPLACEMENT Half thickness: The thickness of a slab material that reduces by half the intensity of radiation incident on one side of the slab. Hazard: A potential source of a negative consequence or harm. High-Z material: See atomic number. Hydrocarbon: In the context of this report, oil or natural gas. Irradiation: Exposure to radiation. Increased Controls: A set of security measures required by the U.S. Nuclear Regulatory Commission of Category 1 and 2 radiation source or device licensees. Ingestion: Uptake of a material into the body via the digestive tract. Inhalation: Uptake of a material into the body via the respiratory tract. Internal exposure: An exposure received from a source of ionizing radiation inside of the body (NCRP, 2001). Ionizing radiation: Radiation that is sufficiently energetic to ionize the matter (i.e., remove electrons from the atoms) through which it moves. Late effects of radiation: Delayed effects such as fibrosis, atrophy, ulceration, stenosis, or obstruction of the intestine. Late effects may be generic and caused by absorption of radiation directly in the target tissue, or consequential to acute damage in overlying tissues such as mucosa or the epidermis. Latent cancer: Cancerous lesions in a living organism that have not yet progressed to a stage to be detectable. Lethal damage: Radiation damage to mammalian cells is divided into three categories: Lethal Damage is irreversible, irreparable, and leads to cell death. Sublethal damage to cells can be repaired in hours unless additional sublethal damage is added that eventually leads to lethal damage. Potentially lethal damage to cells can be manipulated by repair when cells are allowed to remain in a nondividing state. Natural background radiation: Radiation that exists naturally in the environment. It includes cosmic and solar radiation, radiation from radioactive materials present in rocks and soil, and radioactivity that is inhaled or ingested. Nondestructive testing (NDT): Testing that does not destroy the object under examination. Offsite Source Recovery Project: An effort by the National Nuclear Security Administration to recover and secure radiation sources that may pose a danger to public health, safety, and security. The project is run by Los Alamos National Laboratory. Panoramic irradiator: An irradiation device that does not have shielding built into the device. In such devices, the sources must be housed in thick, shielded structures. Radiation dose: The quantity of radiation energy deposited in an object or medium divided by the mass of the object or medium. The radiation dose of interest in this report is ionizing radiation. Ionizing radiation doses can be expressed as an absorbed dose, equivalent dose, or effective dose. Its SI unit, gray (Gy), is defined as 1 joule (J) of energy absorbed per kilogram of absorbing medium; its old unit is the rad defined as 100 erg of energy absorbed per gram of absorbing medium.
GLOSSARY 213 Radiation dose rate: The quantity of ionizing radiation absorbed by a medium per unit mass of the medium per unit time. Radiation exposure: The act of being exposed to radiation. Also referred to as irradiation. Formally in radiation detection and measurement, radiation exposure is related to the ability of photons to ionize air. Radiation source: Radioactive material packaged to use the radiation it emits. Radioactive: Elements that are unstable and transform spontaneously (i.e., decay) through the emission of ionizing radiation, a process known as radioactive decay. Radioactive decay: See Radioactive. Radiography: The use of radiation to create images of a subject, especially the internal features of a subject. Medical radiography is familiar from routine dental examinations. Industrial radiography is a form of nondestructive testing for aircraft wings, pipes, turbines, reinforced concrete construction, and other applications. Radiological dispersal device (RDD): A device used to spread radioactive material for malevolent purposes. The objective of such a device might be to cause social disruption (panic, evacuation), acute physical harm, the potential for physical harm from chronic exposure, and/or economic damage. An area-denial RDD is one intended to cause contamination that prevents occupation of the contaminated area for an extended period of time. Radiological exposure device (RED): A device used to cause direct radiation exposure for malevolent purposes. Radionuclide: An atom with an unstable nucleus, which undergoes radioactive decay. Radiotherapy: Treatment of disease with ionizing radiation. Radiosurgery: Focal irradiation techniques that use multiple, non-coplanar radiation beams to deliver a prescribed dose of radiation to a lesions, primarily in the brain. Resuspension inhalation: Inhalation of radioactive materials that were deposited onto the ground and later resuspended in air. Risk: As used in this report, the potential for an adverse effect from the accidental or intentional misuse of a radiation source. This potential can be estimated quantitatively if answers to the following three questions can be obtained: (1) What can go wrong? (2) How likely is it that something will go wrong? And (3) What are the consequences? Risk can be expressed in absolute terms or in comparison to other types of risks. Safety: In the context of this report, concerning prevention of failure, damage, human error, and other inadvertent acts involving radiation sources that could result in accidental radiation exposures. Safety risks: In the context of this report, risks that arise from exposures of people to radiation as a direct result of accidents involving radiation sources. Security: In the context of this report, concerning protection against theft, sabotage, and other malevolent acts involving radiation sources.
214 RADIATION SOURCE USE AND REPLACEMENT Self-contained irradiator: âAn irradiator in which the sealed source(s) is completely contained in a dry container constructed of solid materials, the sealed source(s) is shielded at all times, and human access to the sealed source(s) and the volume(s) undergoing irradiation is not physically possible in its designed configuration,â according to the American National Standards Institute (ANSI) Standard N433.1, âSafe Design and Use of Self-Contained, Dry Source Storage Gamma Irradiators (Category I).â Also called a self-shielded irradiator. SI: International System of Units (from the French SystÃ¨me International d'UnitÃ©s), also sometimes referred to as the metric system. Social cost: Costs to society, including direct and indirect costs paid as money and undesirable effects that are not readily monetized.. Societal risk: All risks that affect society, including the health and safety risks and social risks discussed in this report. Solubility: The ability of a substance to dissolve in water or, more generally, in a solvent. Somatic health effect: The harm that exposed individuals suffer during their lifetime, such as radiation-induced cancers (carcinogenesis), sterility, opacification of the eye lens, and life shortening. Special form radioactive material. Defined in 10 CFR Part 71 as radioactive material that exists as a single solid piece or is encapsulated material that meets certain other requirements. SPWLA: Society of Petrophysicists and Well Log Analysts. Stochastic effect: One in which the probability of occurrence increases with increasing dose but the severity in affected individuals does not depend on the dose (radiation carcinogenesis and genetic effects). There is no threshold dose for effects that are truly stochastic, because these effects arise in single cells and it is assumed that there is always some small probability of the effect occurring no matter how small the radiation dose is. Total Body Radiation syndrome: The response of an organism to acute total body radiation exposure is influenced by the combined response to radiation of all organs constituting the organism. Depending on the actual total body dose above 1 Gy, the response is described as a specific radiation syndrome: â¢ Bone marrow syndrome: 1 Gy < Dose < 10 Gy. â¢ Gastrointestinal syndrome: 10 Gy < Dose < 100 Gy. â¢ Central nervous system syndrome: Dose > 100 Gy. Transuranic waste: Radioactive waste containing long-lived radioactive transuranic elements (elements with atomic numbers greater than 92) such as plutonium in concentrations greater than 100 nanocuries per gram. Ultrasonics: The use of high-intensity acoustic energy for materials examination. Vitrification: A process for immobilizing radioactive material in glass matrixes. Well logging: The practice of measuring the properties of the geologic strata through which a well has been drilled and recording the results as a function of depth.
GLOSSARY 215 X-ray: High-energy electromagnetic radiation. In this report, radiation emitted by a machine such as an x-ray tube or an electron accelerator with a high-Z target is always referred to as x-ray radiation to distinguish it from radiation from decay of a radionuclide.