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Appendix G Glossary 6-day curies: The number of curies present in a shipment of Mo-99 6 days after it leaves a producerâs facilities. 6-day curies per week: The number of 6-day curies supplied in a week. Barns: A unit of measure of the fission cross section; 1 barn = 1 Ã 10â24 cm2. Becquerel (Bq): The SI derived unit of radioactivity, one Becquerel is equal to one radioactive disintegration per second. Breakthrough: The contamination of Mo-99 in the Tc-99m eluted from the column of a technetium generator that occurs after prolonged use. Brownfield conversion: Conversion within an existing processing facility or an unused facility with hot cells. Calandria: A sealed drum-shaped vessel that contains the heavy-water moderator for the reactor. This vessel is penetrated by a series of horizontal fuel channels and vertical channels for control rods. Casting: The process of melting a metal and pouring into a mold. Cold rolling: Process in which metal sheets are rolled at room temperature to maintain the metalâs original crystalline structure. Cold testing: Testing conducted without the use of radioactive material. Curie (Ci): A unit of radioactivity, defined as 1 Ci = 3.7 Ã 1010 decays per second. 196
APPENDIX G 197 Direct-use material: Material that is directly usable in nuclear weapons. Such materials include highly enriched uranium (HEU) and separated plutonium. Dissolution: The process of putting a material into solution. Downblend: Dilution of HEU with depleted uranium or natural uranium to convert it into low enriched uranium (LEU). Drug master file (DMF): A document submitted to the Food and Drug Administration (FDA) by a Mo-99 producer describing the facility in which the Mo-99 is made; the production process itself, including any raw materials used in production; and product test methods, specifications, stability, and release criteria that may be used as a source of information when FDA approval is sought. Eluting: Recovering an isotope (Tc-99m) by passing a saline solution through the alumina column of the generator. Enriched uranium: Uranium with a higher concentration of the U-235 isotope than found naturally. Enrichment: Process used to increase the concentration of the uranium-235 (U-235) isotope in a material relative to U-238. Fission: Process whereby a large atomic nucleus (such as uranium) is split into two (and sometimes three) smaller nuclei. Fission cross-section: Probability that a nucleus will capture a neutron and fission, usually expressed in barns. Fission fragments: Smaller atomic fragments resulting from fission of a large nucleus. Formula quantities: Special nuclear material in strategic quantities. For HEU this quantity is greater than 5 kg. Greater-Than-Class-C waste: Radioactive waste that contains concentrations of certain radionuclides above the Class C limits in 10 CFR Â§61.55. Greenfield construction: Construction of new facilities for producing and/or processing Mo-99. Half-life: The time required for a quantity of radioactive material to decay to half of its initial value. High-level waste: Highly radioactive materials containing fission products and transuranic elements produced as a byproduct of the reactions that occur inside nuclear reactors. Highly enriched uranium: Uranium enriched to concentrations greater than or equal to 20 percent by weight of U-235. Hot cell: Shielded workspace for working with highly radioactive materials.
198 APPENDIX G Hot rolling: Heating metal above its recrystalization temperature before rolling it to form sheets. Isomeric transition: Radioactive decay process in which the nucleus of a metastable isotope has an elevated energy state and releases this energy by emitting a gamma ray. Large-scale producer: Producers of Mo-99 who supply more than 1000 6-day curies of Mo-99 per week to the market on a routine basis. Low enriched uranium: Uranium enriched to concentrations less than 20 percent by weight of U-235. Medical isotopes: Class of radioactive isotopes (radioisotopes) that have unstable nuclei and emit radiation. This radiation is used for medical imaging and treatment. Neutron capture: Process involving the capture of neutrons by an atomic nucleus to form a heavier nucleus. Neutron flux: Measure of the intensity of neutron radiation, defined as the number of neutrons crossing a unit area of a square centimeter in one second (neutrons/cm2-s). New drug application (NDA): A written application to the Food and Drug Administration seeking approval to sell a pharmaceutical in the United States. Perfusion: Delivery of arterial blood to biological tissue. Perfusion reserve: Capacity of flow through a blood vessel system in an organ under a stress or stimulus. Regional producers: Producers who supply Mo-99 for indigenous or regional use in less than large-scale quantities. Significant quantity: Approximate quantity of material from which the possibility of manufacturing a nuclear explosive device (i.e., a device that can achieve a prompt critical mass) cannot be excluded. Special nuclear materials: Fissile material or material that is capable of sustaining a chain reaction of nuclear fission. It includes plutonium and uranium enriched in the isotopes U-233 or U-235. Stenosis: Abnormal narrowing of a blood vessel. Supplemental new drug application (sNDA): Additional written documentaÂ tion submitted for approval by the FDA when a producer makes major changes to the process or raw materials it uses to make a pharmaceutical.
APPENDIX G 199 Target: Material containing U-235 that is designed to be irradiated in a nuclear reactor. Target cladding: Target encapsulation of aluminum or stainless steel that serves to protect the chemically reactive uranium metal or alloy and to contain the fission products produced during irradiation. Target meat: Uranium-bearing material in the target. Tc-99m kits: Chemicals (e.g., pharmaceutical agent, chelating compound, and saline solution) used to formulate a radiopharmaceutical to which Tc-99m is added. Technetium generator: Device used to store Mo-99 and extract its decay product Tc-99m. Technetium generator curies: Calibrated quantity of Mo-99 based on the number of curies that are contained in the generator on the day of or day after its delivery to the radiopharmacy, hospital, or clinic. Thermal neutron: Low-energy neutron of about 0.025 electron volts at room temperature. Tracer testing: Evaluation of the separations methods and processing of targets using very small amounts of radioactive material.