Radiation terms and definitions 1-Activation
The process of making a radioisotope by bombarding a stable element with neutrons, protons, or other types of radiation.
Radiation terms and definitions 2-Agreement State
A state that has signed an agreement with the Nuclear Regulatory Commission under which the state regulates the use of byproduct, source, and small quantities of special nuclear material within that state.
Radiation terms and definitions 3-Air Sampling
The collection of samples to detect the presence of, and/or to measure the quantity of volatile or solid radioactive material, nonradioactive particulate matter, or various chemical pollutants in the air.
Radiation terms and definitions 4-Airborne Radioactivity Area
A room, enclosure, or area in which airborne radioactive materials, composed wholly or partly of licensed material, exist. It exists in concentrations that (1) Exceed the derived air concentration limits or (2) Would result in an individual present in the area without respiratory protection exceeding, during the hours the individual is present in the area, 0.6 percent of the annual limit on intake or 12 derived air concentration-hours.
Radiation terms and definitions 5-Alara
Acronym for "As Low As Reasonably Achievable." It means making every reasonable effort to maintain exposures to ionizing radiation as far below the dose limits as practical. Be consistent with the purpose for which the licensed activity is undertaken, taking into account the state of technology, the economics of improvements in relation to state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations. These means are in relation to utilization of nuclear energy and licensed materials in the public interest.
Radiation terms and definitions 6-Alpha Particle
A positively charged particle ejected spontaneously from the nuclei of some radioactive elements. It is identical to a helium nucleus that has a mass number of 4 and an electric charge of +2. It has low penetrating power and a short range (a few centimeters in air). The most energetic alpha particle will generally fail to penetrate the dead layers of cells covering the skin and can be easily stopped by a sheet of paper. Alpha particles represent much more of a health risk when emitted by radionuclides deposited inside the body.
Radiation terms and definitions 7-Annual Limit on Intake (ALI)
The derived limit for the permissible amount of radioactive material taken into the body of an adult radiation worker by inhalation or ingestion in a year. The ALI is the smaller value of intake of a given radionuclide in a year by the reference man that would result in either a committed effective dose equivalent of 5 rems (0.05 sievert) or a committed dose equivalent of 50 rems (0.5 sievert) to any individual organ or tissue.
Radiation terms and definitions 8-Atom
The smallest particle of an element that cannot be divided or broken up by chemical means. It consists of a central core of protons and neutrons, called the nucleus. Electrons revolve in orbits in the region surrounding the nucleus.
Radiation terms and definitions 9-Atomic Energy
Energy released in nuclear reactions. Of particular interest is the energy released when a neutron initiates the breaking up or fissioning of an atom's nucleus into smaller pieces (fission), or when two nuclei are joined together at millions of degrees of heat (fusion). It is more correctly called nuclear energy.
Radiation terms and definitions 10-Atomic Energy Commission
A federal agency created in 1946 to manage the development, use, and control of nuclear energy for military and civilian applications. Abolished by the Energy Reorganization Act of 1974 and succeeded by the Energy Research and Development Administration (now part of the US Department of Energy) and the US Nuclear Regulatory Commission.
Radiation terms and definitions 11-Atomic Number
The number of positively charged protons in the nucleus of an atom.
Radiation terms and definitions 12-Attenuation
Attenuation is the process by which the number of particles or photons entering a body of matter is reduced by absorption and scattering.
Radiation terms and definitions 13-Background Radiation
Radiation from cosmic sources; naturally occurring radioactive materials, including radon (except as a decay product of source or special nuclear material), and global fallout as it exists in the environment from the testing of nuclear explosive devices. It does not include radiation from source, byproduct, or special nuclear materials regulated by the Nuclear Regulatory Commission. The typically quoted average individual exposure from background radiation is 360 millirems per year.
Radiation terms and definitions 14-Becquerel (Bq)
The unit of radioactive decay equal to one disintegration per second. The Becquerel is the basic unit of radioactivity used in the international system of radiation units, referred to as the "SI" units. 37 billion (3.7×1010) becquerels=1 curie (Ci).
Radiation terms and definitions 15-Beta Particle
A charged particle emitted from a nucleus during radioactive decay, with a mass equal to 1/1837 that of a proton. A negatively charged beta particle is identical to an electron. A positively charged beta particle is called a positron. Exposure to large amounts of beta radiation from external sources may cause skin burns (erythema). Beta emitters can also be harmful if they enter the body. Thin sheets of metal or plastic may stop beta particles.
Radiation terms and definitions 16-Bioassay
The determination of kinds, quantities, or concentrations and, in some cases, the locations of radioactive material in the human body, whether by direct measurement (in vivo counting) or by analysis and evaluation of materials excreted or removed (in vitro) from the human body
Radiation terms and definitions 17-Biological half-life
The time required for a biological system, such as that of a human, to eliminate, by natural processes, half of the amount of a substance (such as a radioactive material) that has entered it.
Radiation terms and definitions 18-Buildup Factor
The factor by which the total value of the quantity being assessed at the point of interest exceeds the value associated with only primary radiation. The total value includes secondary radiations especially scattered radiation. The buildup factor is most commonly used for ionizing photons and may apply to various quantities—e.g., dose kerma, fluence.
Radiation terms and definitions 19-Byproduct
Byproduct is (1) any 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 (as in a reactor); and (2) the tailings or wastes produced by the extraction or concentration of uranium or thorium from ore.
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