Glossary of Common Radiation Terms


Positively charged particles emitted from the nucleus of an atom. Alpha particles are relatively large, and very heavy. Due to this strong (+) charge and large mass, an alpha particle cannot penetrate far into any material. A sheet of paper or an inch of air can usually stop most alpha particles.

Background Radiation

Naturally occurring radiation is always present, it includes high energy gamma rays from the sun and outer space and alpha, beta, and gamma radiation emitted from elements in the earth.

Beta Particles

Negatively charged particles emitted from an atom. Beta particles have a mass and charge equal to that of an electron. They are very light particles (about 2,000 times less mass than a proton) and have a charge of -1. Because of their light mass and single charge, beta particles can penetrate more deeply than alpha particles. A few millimeters of aluminum will stop most beta particles.

Bq (Becquerels)

A quantity of radioactivity in which one atom is transformed per second. 1 dps (one disintegration per second).

CPM (counts per minute)

The unit of measurement usually used to measure alpha and beta radiation.

Gamma Rays

Short wavelength electromagnetic radiation higher in frequency and energy than visible and ultraviolet light. Gamma rays are emitted from the nucleus of an atom. These high energy photons are much more penetrating than alpha and beta particles.


An atomic particle, atom, or molecule that has acquired an electrical charge, either positive or negative, by gaining or losing electrons.


The process by which neutral atoms of molecules are divided into pairs of oppositely charged particles known as ions.

Ionizing Radiation

Radiation capable of producing ionization by breaking up atoms or molecules into charged particles called ions.


The emission and propagation of energy through space or through matter in the form of particles or waves.

Roentgen (rent-gen)

A basic unit of measurement of the ionization produced in air by gamma or x-rays. One Roentgen (R) is exposure to gamma or x-rays that will produce one electrostatic unit of charge in one cubic centimeter of dry air. One thousand milliroentgen (1,000 mR)= 1R.


The naturally occurring or artificially produced radioactive form of an element.


A unit of dose equivalent. 1 Sv= 100 roentgens, 10 µSv/hr = 1 milliroentgen/hr. (µSv micro-Sievert, micro is one millionth, milli is one thousandth.)


Electromagnetic radiation (photons) of higher frequency and energy than visible and ultraviolet light, usually produced by bombarding a metallic target with high speed electrons in a vacuum. X-rays are photons emitted by interactions involving orbital electrons rather than atomic nuclei. X-rays and gamma rays have the same basic characteristics. The only difference between them is their source of origin.

Other Sources


Major Uses of Radioisotopes in the United States – Ohio University Dept of Laboratory and Radiatio Safety


Americum-241 Used in many smoke detectors for homes and businesses to measure levels of toxic lead in dried paint samples, to ensure uniform thickness in rolling processes like steel and paper production, and to help determine where oil wells should be drilled.

Cadmium-109 Used to analyze metal alloys for checking stock and scrap sorting. Calcium-47 Important aid to biomedical researchers studying the cellular functions of bone formation in mammals.

Californium-252 Used to inspect airline luggage for hidden explosives, to gauge moisture content of soil in the road construction and building industries, and to measure the moisture of materials stored in soils.

Carbon-14 Major research tool. Helps in research to ensure that potential drugs are metabolized without forming harmful by-products. Used in biological research, agriculture, pollution control, and archeology.

Cesium-137 Used to treat cancerous tumors, to measure correct patient dosages of radioactive pharmaceuticals, to measure and control the liquid flow in oil pipelines, to tell researchers whether oil wells are plugged by sand, and to ensure the right fill level for packages of food, drugs, and other products. (The products in these packages do not become radioactive)

Chromium-51 Used in research in red blood cell survival studies.

Cobalt-57 Used as a tracer to diagnose pernicious anemia.

Cobalt-60 Used to sterilize surgical instruments, and to improve the safety and reliability of industrial fuel oil burners. Used in cancer treatment, food irradiation, gauges, and radiography.

Copper-67 When injected with monoclonal antibodies into a cancer patient, helps the antibodies bind to and destroy the tumor.

Curium-244 Used in mining to analyze material excavated from pits and slurries from drilling operations.

Gallium-67 Used in medical diagnosis.

Iodine-123 Widely used to diagnose thyroid disorders and other metabolic disorders including brain function.

Iodine-125 Major diagnostic tool used in clinical tests and to diagnose thyroid disorders. Also used in biomedical research.

Iodine-129 Used to check some radioactivity counters in in-vitro diagnostic testing laboratories.

Iodine-131 Used to treat thyroid disorders.

Iridium-192 Used to test the integrity of pipeline welds, boilers and aircraft parts and in brachytherapy/tumor irradiation.

Iron-55 Used to analyze electroplating solutions and to detect the presence of sulphur in the air. Used in metabolism research.

Krypton-85 Used in indicator lights in appliances such as clothes washers and dryers, stereos, and coffee makers; used to gauge the thickness of thin plastics and sheet metal, rubber, textiles and paper, and to measure dust and pollutant levels.

Nickel-63 Used to detect explosives, and in voltage regulators and current surge protectors in electronic devices, and in electron capture detectors for gas chromatographs.

Phosphorus-32 Used in molecular biology and genetics research.

Phosphorus-33 Used in molecular biology and genetics research.

Plutonium-238 Has powered more than 20 NASA spacecraft since 1972.

Polonium-210 Reduces the static charge in production of photographic film and other matierals.

Promethium-147 Used in electric blanket thermostats, and to gauge thickness of thin plastics, thin sheet metal, rubber, textile and paper.

Radium-226 Makes lighting rods more effective.

Selenium-75 Used in protein studies in life science research.

Sodium-24 Used to locate leaks in industrial pipelines, and in oil well studies.

Strontium-85 Used to study bone formation and metabolism.

Sulphur-35 Used in survey meters by schools, the military and emergency management authorities. Also used in cigarette manufacturing sensors and medical treatment.

Technetium-99m Used in genetics and molecular biology research. The most widely used radioactive pharmaceutical for diagnostic studies in nuclear medicine. Different chemical forms are used for brain, bone, liver, spleen, and kidney imaging and also for blood flow studies.

Thallium-201 Used in nuclear medicine from nuclear cardiology and tumor detection.

Thallium-204 Measures the dust and pollutant levels on filter paper, and gauges the thickness of plastics, sheet metal, rubber, textiles, and paper. Thoriated Tungsten Used in electric arc welding rods in construction, aircraft, petrochemical and food processing equipment industries. They produce easier starting, greater arc stability and less metal contamination.

Thorium-229 Helps fluorescent lights last longer.

Throium-230 Provides coloring and fluorescence in colored glazes and glassware. Tritium Major tool for biomedical research. Used in life science and drug metabolism studies to ensure the safety of potential new drugs, for self-luminous aircraft and commercial exit signs, for luminous dials, gauges and wrist watches, to produce luminous paint, and for geological prospecting and hydrology.

Uranium-234 Used in dental fixtures like crowns and dentures to provide a natural color and brightness.

Uranium-235 Fuel for nuclear power plants and naval nuclear propulsion systems, and used to produce fluorescent glassware, a variety of colored glazes, and wall tiles.

Xenon-133 Used in nuclear medicine for lung ventilation and blood flow studies.

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