2nd Edition
Robert J. Barish, PhD
Alpha particle-a particle emitted from an atom following one type of radioactive decay. An alpha particle is made up of two protons and two neutrons.
Astrocytoma-a type of brain tumor "some studies have found in greater proportion in pilots than in members of the general public".
Atom-the basic building block of matter. The smallest unit of matter that retains the physical and chemical properties of the material. An atom consists of a nucleus surrounded by orbiting electrons. See Element.
Atomic mass-the total number of protons and neutrons in an atom.
Atomic number-the number of protons in an atom. This is the same as the number of electrons in a neutral or nonionized atom.
Background radiation-exposure to radiation from natural ("background") sources in our environment.
Becquerel (Bq)-the unit of intensity of radioactive decay. One becquerel corresponds to one radioactive decay per second.
Beta particle-an electron emitted from an atom following certain types of radioactive decay.
Bubble detector-a device that measures neutron radiation exposure. Consists of a tube containing a special liquid that "boils" when struck by neutrons. Measurement of the areas that have "boiled" indicates the neutron dose.
CARI-6-a computer program made available by the FAA to estimate the connection between galactic cosmic ray dose and aircrew member exposures. The version that assumes a direct path between two locations is CARI-6. CARI-6M allows for the entry of flight path changes and additional altitude changes.
Coronal mass ejection––the projection into space of a part of the sun's external atmosphere, which is composed primarily of atomic hydrogen.
Cosmic radiation-radiation exposure received from the sun and stars. This is one component of our external background radiation exposure; the other component is terrestrial radiation.
Dose-a way of specifying the amount of radiation energy absorbed by a material. Units used to describe dose are gray or rad.
Equivalent dose-a quantity used to measure radiation dose based on the biological damage expected. Units used to describe equivalent dose are sievert or rem.
Effective dose-when only a portion of the body is irradiated, the risks of damage to the individual tissues and organs can be taken into account separately and a risk factor can be assigned to these individual tissues. The sum of the risk-weighted values is the effective dose.
Electromagnetic radiation-a type of radiation consisting of a combined electric and magnetic field that travels through space as pure energy with no mass. Common examples are light, radio waves, x-rays, and gamma rays.
Electron-an atomic particle found orbiting the nucleus of an atom. An electron has a small negative electrical charge.
Element-atoms with the same number of protons in their nuclei all have the same chemical properties and are all one element. Each element is thus uniquely described by the atomic number. The list of naturally occurring elements ranges from hydro- gen (with one proton) to uranium (with 92 protons).
Environmental Protection Agency (EPA)- the federal agency that develops and enforces regulations to implement environmental laws enacted by Congress.
Federal Aviation Administration (FAA)-the federal agency responsible for the regulation of civil aviation in the United States including operation of the system of air traffic control and navigation for civilian and military aircraft. Until 1967 it was called the Federal Aviation Agency.
Film badge detector-an instrument for measuring radiation exposure. Consists of a small plastic case containing x-ray film and several small pieces of metal. The film badge is sent off to a laboratory to be developed and analyzed.
Gas-filled detector-an instrument currently under development for measuring radiation dose. This detector is based on a special gas mixture; when radiation hits the gas mixture, a pulse of electricity is generated. The size of the electric pulse can be measured and indicate the type and energy of the radiation.
Gamma ray-a photon of electromagnetic radiation that may be emitted from an atomic nucleus following radioactive decay.
Genetic mutation-a change in a sperm or egg cell that is not apparent until fertilization occurs and an embryo is formed.
Gray (Gy)-the unit of radiation dose.
Ground level event-a particle event that is particularly intense so that the radiation produced has enough energy to reach the earth's surface.
Healthy worker syndrome-for occupations in which it is essential to be healthy to perform the required duties, workers in that occupation usually have a lower incidence of health problems than do members of the general public.
High-speed civil transport (HSCT)-aircraft designed to fly 1,600 miles per hour at altitudes as high as 80,000 feet.
Hormesis––a dose response to a normally toxic agent in which administration of a small quantity of the usually harmful substance is shown to have a beneficial, rather than negative, health effect, possibly by stimulating the body's natural immune system.
International Commission on Radiological Protection (ICRP)-the inter- national counterpart of the NCRP.
Ionization-the removal of an orbiting electron from an atom. The result is a positive atom (ion) formed of the remaining nucleus and other electrons, and a free electron.
Ionizing radiation-any radiation that has sufficient energy to dislodge an orbiting electron from an atom.
Irradiation-when a material (or a person) is subjected to radiation it is being irradiated.
Isotopes-different forms of the same element; they differ only in the number of neutrons in their nuclei. Many natural elements can be found in several isotopic forms.
Linear energy transfer (LET)-a measure of the ionization intensity along the track of a particle of radiation as it travels through a material. The LET is expressed as energy deposited per unit length of the track. It is conventionally given in units of kiloelectron volts per micrometer.
Linear model-a concept used by radiation scientists to hypothesize on the unknown harmful effects of low doses of radiation exposure based on the known harmful effects of higher doses of radiation exposure. The linear model predicts that because 100 mSv of exposure would be expected to cause 4 cancer deaths in a population of 1,000 exposed people, then 10 mSv would be expected to cause cancer deaths in 4 of 10,000 people, 1 mSv would be expected to cause cancer deaths in 4 of 100,000 people.
Malignant melanoma-a type of skin cancer found in higher proportions in pilots than in the general population. Incidence of this cancer is related to exposure to the sun.
Mass number-the total number of neutrons and protons in an atom.
Maximum permissible dose (MPD)-the maximum amount of radiation people should be exposed to as recommended by the NCRP and the ICRP (called dose constraints by the latter organization).
Millisievert (mSv)-one one-thousandth of a sievert.
Molecule-for materials other than elements, the smallest unit that retains the material's physical and chemical properties is one molecule of the substance. One water molecule, for example, is made of two hydrogen atoms linked to one oxygen atom (H2O).
National Council on Radiation Protection and Measurements (NCRP)-a federal agency responsible for making recommendations for radiation protection policies.
National Oceanic and Atmospheric Administration (NOAA)-an agency of the U.S. Commerce Department, responsible for monitoring atmospheric conditions, including radiation levels.
Neutron-an atomic particle found in the nucleus of an atom. The neutron has mass but not electrical charge.
Nonstochastic effect-a radiation effect which is caused by a particular amount of radiation and for which the severity of the effect is directly related to the amount of radiation dose. See Stochastic Effect.
Nuclear Regulatory Commission (NRC)-the federal agency that regulates nuclear power, radioactive materials, radioactive waste and nuclear security.
Nucleus-the central core of an atom. It contains neutrons and protons. The nucleus is surrounded by orbiting electrons.
Particulate radiation-radiation that is in the form of particles having measurable mass. They may have electrical charge or they may be neutral. The most common particulate radiation consists of any of the three atomic particles (neutrons, pro- tons, or electrons) either singly or combined.
Photon-a single unit of electromagnetic radiation. Although this radiation behaves with wavelike properties such as reflection (it may "bounce" off of things) or refraction (it can be bent), it may also be characterized as single bundles of energy that can be detected individually, like particles. Each such bundle is an individual photon.
Proton-a particle found in the nucleus of an atom. It has mass and a positive electrical charge.
Quality factor (Q)-a number used to convert an actual dose of radiation expo- sure, expressed in gray (or rad), into a equivalent dose, expressed in sievert (or rem). Equal doses of different types of radiation will not produce the same biological effects. When dose is converted to equivalent dose(by multiplying the dose by Q), the biological damage produced by different types or energies of radiation is then comparable.
Rad-a unit of radiation dose. Since dose represents energy deposited per unit mass of material, the rad was defined as 100 erg per gram. This unit has now been replaced by the gray. 1 rad = 0.01 gray.
Radiation-the transport of energy through space. Radiation can be either particulate radiation or electromagnetic radiation.
Radioactive decay-if an atom is unstable because it has too much energy, it may become stable by throwing off one or more of its nuclear particles. This atom is said to have undergone radioactive decay.
Radioactivity-the phenomenon of radioactive decay. A sample of some material whose atoms are undergoing radioactive decay is said to be radioactive. The atoms are throwing off (radiating) particles to achieve stability. The intensity of a material's radioactivity is measured in becquerels.
Radon-a radioactive gas given off by the decay of radium, typically found in soil and bedrock. Radon is dangerous when inhaled into the lungs.
Relative biological effectiveness (RBE)-a number used to modify the dose of radiation in order to reflect the amount of biological damage that is produced when considering the interaction of that radiation with a specific material. This concept is similar to the concept of quality factor, used in radiation protection.
Rem-a unit of equivalent dose. The older unit of absorbed dose was the rad. Multiplying dose in rad by Q, the quality factor, gives equivalent dose in rem. 1 rem = 100 erg per gram. This unit has now been replaced by the sievert. 1 rem = 0.01 sievert.
Sievert (Sv)-a unit of equivalent dose.
Solar particle event-a coronal mass ejection that results in the release of high- energy particulate radiation that may reach Earth and impact the dose rate at air- liner altitudes.
Solar flare-a sporadic event in which the sun releases a flare that projects millions of miles into space.
Solar flare cycle-an 11-year cycle of increasing and then decreasing solar flare activity.
Somatic mutation-a change in a body cell that causes change in the behavior of the cell's offspring. If radiation causes a somatic mutation in a cell, it might lead to the development of cancer.
Stochastic effect-radiation effects that are statistical in nature. The probability that they will occur increases with radiation dose, but how severe the effect is not dependent on radiation dose.
Terrestrial background radiation-the portion of background radiation expo- sure that is received from our environment on Earth. The other component of our external background radiation exposure is cosmic radiation.
Threshold dose-a dose of radiation at which nonstochastic radiation effects will occur. Below this dose, nonstochastic effects will not occur.
Track-etch detector-a device for measuring neutron radiation dose. When neutrons strike the special materials in this detector, they make tiny holes along the paths they follow. Later, the holes can be enlarged by the application of an acid and then examined under a microscope to reveal neutron dose.
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