Glossary

A

Activity

Sometimes used for radioactivity, particularly when referring to an amount of radioactivity (i.e., the number of nuclear transformations occurring in a given quantity of material per unit of time).

Alpha radiation

A particle consisting of two protons and two neutrons, given off by the radioactive decay of a number of elements, including uranium, plutonium, and radon. Alpha particles cannot penetrate a sheet of paper. However, alpha-emitting isotopes ingested into the body can be very damaging.

Aqueous decontamination

As used in this report, removal of radioactive contamination by water-based solutions of acids and other oxidizing agents along with appropriate rinses. Also referred to as chemical decontamination. To be distinguished from dry methods, such as mechanical removal of radioactive contaminants through scraping or vacuuming; and gaseous decontamination involving an agent in the gas phase that reacts with, for example, uranium, for its removal from surfaces.

Asbestosis

A disease of the lungs caused by inhalation of asbestos particles.

Assay

Analysis of a material for one or more valuable components. For example, an assay might ascertain the percentage of 235U isotope in a quantity of natural uranium.

Atomic vapor laser isotope separation (AVLIS)

An advanced enrichment technology that converts a feed material into product streams in which a selected set of isotopes has been enriched or depleted. Upon electron beam vaporization of the feed stream, desired isotopic vapors in the vapor are selectively photoionized with lasers and electrostatically withdrawn.

B

Barrier material

See diffusion barrier.

Becquerel (Bq)

Like the curie, a measure of the number of disintegrations from a radioactive material. One Bq is equal to 27 picocuries.

Beta radiation

A particle emitted in the radioactive decay of many radionuclides. A beta particle is identical with an electron. It has a short range in air and a low ability to penetrate other materials.



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--> Glossary A Activity Sometimes used for radioactivity, particularly when referring to an amount of radioactivity (i.e., the number of nuclear transformations occurring in a given quantity of material per unit of time). Alpha radiation A particle consisting of two protons and two neutrons, given off by the radioactive decay of a number of elements, including uranium, plutonium, and radon. Alpha particles cannot penetrate a sheet of paper. However, alpha-emitting isotopes ingested into the body can be very damaging. Aqueous decontamination As used in this report, removal of radioactive contamination by water-based solutions of acids and other oxidizing agents along with appropriate rinses. Also referred to as chemical decontamination. To be distinguished from dry methods, such as mechanical removal of radioactive contaminants through scraping or vacuuming; and gaseous decontamination involving an agent in the gas phase that reacts with, for example, uranium, for its removal from surfaces. Asbestosis A disease of the lungs caused by inhalation of asbestos particles. Assay Analysis of a material for one or more valuable components. For example, an assay might ascertain the percentage of 235U isotope in a quantity of natural uranium. Atomic vapor laser isotope separation (AVLIS) An advanced enrichment technology that converts a feed material into product streams in which a selected set of isotopes has been enriched or depleted. Upon electron beam vaporization of the feed stream, desired isotopic vapors in the vapor are selectively photoionized with lasers and electrostatically withdrawn. B Barrier material See diffusion barrier. Becquerel (Bq) Like the curie, a measure of the number of disintegrations from a radioactive material. One Bq is equal to 27 picocuries. Beta radiation A particle emitted in the radioactive decay of many radionuclides. A beta particle is identical with an electron. It has a short range in air and a low ability to penetrate other materials.

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--> Blending The combining of materials of different uranium enrichment levels to yield an enrichment level somewhere in between. C Carcinogen(ic) A substance that produces or incites cancer. Cascade A connected series of enrichment components (converters), with the material from one being passed to another for further enrichment. Cell A configuration of up to 12 diffusion stages. Characterization An information-gathering process usually involving measurement or sampling and analysis of contaminants present. Chemical decontamination In this report, used synonymously with aqueous decontamination to refer to the decontamination of materials by reaction of radioactive contaminants with chemicals in aqueous solution. Chlorofluorocarbon (CFC) Any of a group of compounds that contain carbon, chlorine, fluorine, and sometimes hydrogen used as refrigerants, cleaning solvents, and aerosol propellants. Class III low-level waste Radioactive waste that will not result in an off-site dose to the public of more than 100 millirem per year. Class I low-level waste Radioactive waste that will not result in an off-site dose to the public of more than 10 millirem per year. Cleanup Actions taken to deal with a release or threatened release of hazardous substances that could affect public health and/or the environment. Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) A federal law, enacted in 1980, that governs the cleanup of hazardous, toxic, and radioactive substances. The act and its amendments created a trust fund, commonly known as Superfund, to finance the investigation and cleanup of abandoned and uncontrolled hazardous waste sites. Contingency In cost estimates, an estimated potential percent increase in cost of a given project resulting from unforeseen events or causes. Converter A cascade component containing the barrier material. Gaseous uranium hexafluoride is pumped into the converters in a cascade via piping and associated compressors and pumps, where it is enriched slightly after passing through the barrier material. Criticality In a nuclear criticality event, an assemblage of enriched uranium results in a self-sustaining chain reaction generating large amounts of heat, radioactive fission products, and gamma and neutron radiation. Usually a nuclear criticality event is self-limiting because the energy release disrupts the geometric configuration of the enriched material

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--> that caused the criticality. If the assemblage reforms again, another criticality event will occur. Hence, criticality events can be pulsed events. The burst of neutrons that occurs during such an event can be lethal to anyone exposed. Criticality prevention Approaches, either technical or administrative, to prevent the occurrence of criticality events. Curie (Ci) A unit of radioactivity that represents the amount of radioactivity associated with one gram (0.032 ounce) of radium. If a sample of radioactive material exhibits one curie of radioactivity, it is emitting radiation at the rate of 3.7 million times a second or 3.7 million disintegrations per second. One becquerel (Bq) is equal to 27 picocuries (billionths of a curie). D Daughter product, radioactive progeny, decay daughter A nuclide formed by the radioactive decay of another nuclide, known in this context as the parent. Decommissioning Retirement of a nuclear facility, including decontamination and/or dismantlement. Often used synonymously with decontamination and decommissioning (D&D). Decontamination Removal of unwanted radioactive or hazardous contamination by a chemical or mechanical process. Decontamination factor (DF) The original amount of radionuclide (A o) divided by the final amount (Af). In some cases, decontamination effectiveness is reported in terms of percentage of contamination removed. De minimis That level of contamination below which regulatory control is not required. Depleted uranium (hexafluoride) The byproduct of the uranium enrichment process. Uranium that in the process of enrichment has been stripped of most of the 235U it once contained, so that it has more 238U than natural uranium. Depleted uranium is used in some parts of nuclear weapons and as a raw material for plutonium production. Large quantities of depleted uranium hexafluoride (DUF6) are stored at the uranium enrichment sites. Diffusion barrier The porous, tube-like material housed in the converters that is used to separate uranium isotopes of different molecular weights (e.g., 235U from 238U) by virtue of their different diffusion rates. E Electrical raceway Localized areas of buildings containing electrical wires and cables. End state In this report, the final state to be achieved at a site through D&D. Also referred to as end point. Enrichment The process of increasing the concentration of one isotope of a given element (in the case of uranium, increasing the concentration of 235U).

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--> Entombment The encasement of radioactive materials in concrete or other structural materials sufficiently strong and structurally long-lived to ensure retention of the radioactivity until it has decayed to levels that permit restricted release of the site. Environmental restoration The cleanup process for a site designed to ensure that risks to the environment or human health are eliminated or reduced to levels approved by the regulatory agencies. F Federal Facilities Compliance Act of 1992 (FFCA) A federal law requiring all federal facilities and installations to adhere to the requirements of environmental protection regulations. Feed (stream) In this report, the uranium hexafluoride gas fed into the gaseous diffusion plant cascades for enrichment. Fission The splitting or breaking apart of the nucleus of a heavy atom like uranium or plutonium, usually caused by the absorption of a neutron. Large amounts of energy and one or more neutrons are released when an atom fissions. Fixed contamination Radioactive contamination that is not easily removed by casual contact or by washing or wiping. Free release Acceptable for use by the public without restriction. Freon® One of a class of chlorinated fluorocarbon heat transfer fluids. Friable asbestos Asbestos that is easily crumbled, thus releasing fibers into the air. Asbestos that is not easily crumbled is referred to as nonfriable. Fuel reprocessing Chemical dissolution and separation of uranium and plutonium from the associated fission products found in irradiated nuclear reactor fuel. Full-time equivalent (FTE) Numeric equivalent, in person hours or salary, of one full-time employee. Concept used for budgetary purposes. G Gamma radiation High-energy, penetrating electromagnetic radiation emitted in the radioactive decay of many radionuclides. Gamma rays are thus similar to x rays. Gas centrifuge process A method of isotope separation in which heavy gaseous atoms or molecules are separated from light ones by centrifugal force and an induced counter-current flow in the swirling gas. Gaseous decontamination In this report, removal of uranium deposits by fluorination using chlorine trifluoride gas, often at elevated temperatures. Gaseous diffusion A method of isotope separation based on the fact that gas atoms or molecules with different masses will diffuse through a porous barrier (or membrane) at

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--> different rates. The method is used to separate 235U from 238U. It requires large plants and significant amounts of electric power. Glovebox A sealed box used to handle some radioactive materials with gloves attached to access ports in the wall. Often filled with an inert gas and fitted with a filtered ventilation system. Greenfield Status achieved in returning a formerly contaminated site to free-release conditions, typically to a grassy field devoid of all buildings, former structures, and chemical or radioactive contamination. Grit blasting Decontamination of surfaces with abrasives, such as sand, propelled by high-pressure air. H Half-life The time required for half of the original radioactive nuclei in a sample of an isotope to undergo radioactive decay. Hanford Site A 570-square-mile federal government-owned reservation in the desert of southeast Washington State. Established in 1942 as part of the Manhattan Project, the Hanford Site has had the chief mission of producing plutonium for use in nuclear weapons. Hanford is home to nine production reactors and four chemical separation plants. Hazardous substance/hazardous waste Any material that poses a threat to public health or the environment as defined by the Resource Conservation and Recovery Act and the Comprehensive Environmental Response, Compensation and Liability Act. High-assay decontamination facility The facility assumed to be built in the D&D cost estimates of Ebasco Environmental and TLG Engineering to disassemble and decontaminate equipment contaminated with highly enriched uranium. High-level radioactive waste Highly radioactive material, containing fission products, or traces of uranium, plutonium, or other transuranic elements, which results from chemical reprocessing of spent fuel and irradiated targets. Highly enriched uranium Uranium in which the percentage of 235U nuclei has been increased from the natural level of 0.71 percent to some level greater than 20 percent. I Indirect costs Costs of a project other than direct labor and materials. Interim storage Storage operations for which monitoring and human control are provided and final disposition is expected. Concepts for interim storage include bulk and compartmented storage of solid, liquid, and gaseous wastes. Ion exchange (resin) A chemical process involving the absorption or desorption of various chemical ions in a solution onto a solid material, usually a plastic or resin. The process

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--> is used to separate and purify chemicals, such as fission products and in adjusting the "hardness" of water (i.e., water softening). Isotope Different forms of an element that have the same atomic number but different atomic weights due to the differences in the number of neutrons contained in the atomic nucleus. Different isotopes of an element may exhibit distinctly different radioactive behaviors or be nonradioactive. L Loose/smearable contamination Radioactive contamination that is easily removed on casual contact or by washing or wiping. Low-assay decontamination facility The new decontamination facility assumed to be built in the cost estimates of Ebasco Environmental and TLG Engineering. This facility was postulated to disassemble and decontaminate equipment contaminated with low-enriched uranium. Low-enriched uranium Uranium in which the percentage of 235U nuclei has been increased from the natural level of 0.71 percent up to as much as 20 percent, usually to 3 to 5 percent. Low-enriched uranium can sustain a chain reaction when suitably moderated and is used as fuel in light-water reactors. Low-level radioactive waste Radioactive waste not classified as high-level radioactive waste, transuranic waste, spent nuclear fuel or byproduct material, and acceptable for disposal in a licensed land disposal facility. Typically, discarded radioactive materials such as rags, construction rubble, and glass are only slightly or moderately contaminated. M Mechanical decontamination Removal of contaminants by physical means, such as scraping, rubbing, or vacuuming. If conducted under dry conditions, the chance of a criticality event in the case of enriched uranium is low. Wet mechanical removal can also be used, such as water jets with an abrasive added. Melt refining Use of high temperature to liquefy metal and separate its contaminants into a slag layer. Mixed waste Waste that contains both chemically hazardous and radioactive materials. Moderator A material (usually water, heavy water, or graphite) that slows neutrons, thereby increasing their chances of fissioning fissile material. N National Priorities List (NPL) The Environmental Protection Agency's list of the most serious hazardous waste sites in the country, based on the site's score from the EPA Hazard Ranking System. The list is updated yearly. National Environmental Policy Act (NEPA) A federal law, enacted in 1970, that requires the federal government to consider in its decision-making processes the environmental impacts of, and alternatives to, major proposed actions.

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--> Natural uranium Uranium that has been extracted from natural ore. It is comprised of 99.3 percent 238U, 0.71 percent 235U, and traces of 234U. Neutron A massive, uncharged particle that is part of an atom's nucleus. Uranium and plutonium atoms fission when they absorb neutrons. Human-made elements can be manufactured by bombarding other elements with neutrons in nuclear reactors. Nevada Test Site (NTS) A 1,350-square-mile area of the southern Nevada desert, about 65 miles northwest of Las Vegas, that has been the site of most of the U.S. underground and atmospheric nuclear explosive tests since it opened in 1951. Nuclide A species of atom characterized by its mass number, atomic number, and nuclear energy state, provided that the mean life in that state is long enough to be observable. O Oak Ridge Reservation A 58-square-mile reservation near Knoxville, Tennessee. Oak Ridge was established as part of the Manhattan Project in 1942 to produce enriched uranium. Today it is the location of the K-25 site (the shutdown gaseous diffusion plant), the Y-12 plant, and the Oak Ridge National Laboratory. P Permanent storage Disposal of radioactive waste so that only negligible risk to the public remains. Typical permanent storage is via land burial. Prompt dismantlement Near-term removal of the equipment, structures, and hazardous and radioactive substances from a site so as not to endanger future occupants. Purge cascade A portion of the enrichment cascade used to remove gaseous contaminants such as low-atomic-weight gases. R Radiological contamination The presence of radionuclides in quantities greater than free-release levels. Radioactive waste A solid, liquid, or gaseous material that contains radioactive materials in quantities greater than free-release levels. Rem (roentgen equivalent man) The special unit of any of the quantities expressed as dose equivalent. The dose equivalent in rem is equal to the absorbed dose in rad multiplied by the quantity factor. Typically, guidelines for exposure are given in a number of rems or millirems (mrem) over a given period of time such as a year. Remedial action, remediation The construction or implementation of corrective actions at a site, such as the environmental restoration program at the plant. Resource Conservation and Recovery Act (RCRA) A federal law enacted in 1976 to address the treatment, storage, and disposal of hazardous waste. Restricted use Remediation of a site to other than free-release levels. Restricted release of a site requires engineered and administrative controls to ensure public safety.

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--> Risk assessment An evaluation performed as part of a remedial investigation to assess conditions at a cleanup site and determine the risk posed to public health and/or the environment. Risk profile The spatial and temporal distribution of risk to a particular population group. Rollup Additional costs of a project, such as indirect costs, contingency funds, and profits, which when added to direct costs yield the total cost of a project. S Safeguards Technical and inspection measures for verifying that nuclear materials are not being diverted to other inappropriate uses. Safe storage Those actions required to place and maintain a nuclear facility in such a condition that future risk to public safety from the facility is within acceptable bounds and that the facility can be safely stored for as long a time as desired. Scabbling A mechanical, multiple-hammer chipping method of removing layers of contaminated concrete. Scavenger gas A gas, typically chlorine trifluoride, used to react with and remove uranium contamination. Separative work unit (SWU) A measure of the effort required in an enrichment facility to separate uranium of a given 235U content into two fractions; one with a higher percentage and one with a lower percentage of 235U. The unit of separative work is the kilogram separative work unit (kg SWU), or separative work unit (SWU). The initial material is called the feed. The fraction with a higher proportion of 235U is called the product; the other is called the tails. Consider a feed of F kilograms to be divided into an enriched stream of P kilograms and a depleted stream of W kilograms. The separative work is given by: where V is the value function, (2x-1) ln[x/(1-x)], with x the mole fraction of 235U in the associated product or feed stream. Special nuclear material (SNM) Defined as plutonium, 233U, or uranium enriched in either 233U or 235U isotopes. These materials are categorized into "low strategic significance," "moderate strategic significance," and "strategic," depending upon the quantities present and the enrichment levels of the materials, as defined in Chapter 10, Code of Federal Regulations, Part 70 (10 CFR 70). Rules governing the control of such materials are also presented in 10 CFR 70. Stage The basic building block of a gaseous diffusion plant cascade, which is composed of a converter, compressor, motor, control valve, and associated piping. Stakeholder A person or group with a vested interest in the outcome of a decision.

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--> State and Tribal Government Working Group A national stakeholder group representing the interests of state and tribal governments. Superfund A term commonly used to refer to the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). Surface contamination Radioactive and/or hazardous material above free-release levels adhering to the surface of an object. Surveillance and maintenance (S&M) Those activities necessary to ensure that a site remains in a safe condition, including periodic inspection and monitoring of the site and prevention of access to radioactive materials left on the site. Switchyard A collection of electrical components used to control and condition electrical power (as for the gaseous diffusion plants). T Tails The name given to depleted uranium hexafluoride (UF6) after the enrichment process takes place. The depleted UF6, which has an enrichment level less than 0.71 percent, is composed mostly of 238 U and small amounts of the 235U isotopes. Technetium-99 A human-made radioactive element produced during nuclear fission. Toxic Substances Control Act (TSCA) A federal law, enacted in 1976 to protect human health and the environment from unreasonable risk caused by exposure to the manufacturing, distribution, use, or disposal of substances containing toxic chemicals. Toxic(ological) Relating to harmful effects of a substance on the human body through physical contact, ingestion, or inhalation. Transite A building material used at the gaseous diffusion plants that is composed of a mixture of cement and asbestos. Transuranic All elements with atomic numbers greater than uranium on the periodic table. All transuranic elements are human made. Tumulus An artificial mound or engineered enclosure. U Unit cost factor The cost of labor and materials necessary to perform a given task once. Unrestricted use See free-release. Uranium hexafluoride (UF6) A volatile compound of uranium and fluorine, UF6 is a solid at atmospheric pressure and room temperature but can be transformed into gas by heating. UF6 gas (alone, or in combination with hydrogen or helium) is the feedstock in most uranium enrichment processes and is sometimes produced as an intermediate product in the process of purifying yellowcake (an intermediate product of uranium mining and drilling) to produce uranium oxide.

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--> Uranium Mill Tailings Radiation Control Act of 1978 The law requiring the U.S. Department of Energy to remediate some 24 inactive uranium processing sites and 5,000 vicinity properties. Uranium oxide (U3O8) The most common oxide of uranium found in typical ores. U3O8 is extracted from the ore during the milling process. The ore typically contains only 0.1 percent U3O8; yellowcake, the product of the milling process, contains about 80 percent U3O8. V Volumetric contamination Hazardous or radioactive materials that are distributed throughout the volume of otherwise uncontaminated matter. W Weapons-grade Uranium containing over 90 percent of the fissile isotope 235U. Y Y-12 A plant in Oak Ridge, Tennessee, built for the Manhattan Project to enrich uranium using calutrons. Today, this plant produces and stores components made of enriched and depleted uranium and lithium for thermonuclear weapons.