Glossary of Radiation Terms
Activity – The number of nuclear disintegrations (transformations) occurring per unit time. Measured in Curies (2.2 x 1012 decays per minute or DPM) or Becquerels (1 decay per second). 1 Curie (1 Ci) = 37 Giga Becquerel (GBq).
Alpha Radiation – Charged particles emitted by a radioactive material with a mass and charge equal to a helium nucleus, consisting of 2 protons and 2 neutrons.
Authorized User – A faculty member authorized by the Radiation Safety Committee to use and possess radioactive material.
Background Radiation – The radiation emitted from naturally occurring sources such as cosmic rays and natural radioactive substances.
Becquerel (Bq) – A unit of radioactivity in the International System of Units (SI) equivalent to 1 decay per second.
Beta Radiation – Charged particles emitted by a radioactive material with a mass and charge equal to an electron.
Bremsstrahlung – Electromagnetic (X-ray) radiation generated by the interaction of charged particles with matter. Normally associated with 32P and lead.
Byproduct Material – Any radioactive material (except special nuclear material) yielded in, or made radioactive by, exposure to the radiation incident to the process of producing or utilizing special nuclear material, generally, radionuclides made in a nuclear reactor.
Cold Zone – An area inside a restricted radioactive material work area where no radioactive materials may be brought into.
Contamination – Radioactive material that has been deposited where it is not desired, and where its presence may interfere with experimental results or cause exposure to laboratory personnel.
Controlled Area – An area outside a restricted area but inside a site boundary, access to which can be limited for any reason.
Counts per Minute – The reading from a survey meter or scintillation counter not corrected for the meter (cpm) efficiency
Curie (Ci) – A unit of radioactivity equal to 2.22 x 1012 disintegrations per minute.
Decay, Radioactive – The process where an unstable atom releases charged particles and/or electromagnetic radiation (gamma or x-rays).
Disintegrations – A measure of the rate of radioactive decay per minute (dpm)
Dose – A general term denoting the quantity of radiation absorbed in a specific mass.
Dose Rate – The dose absorbed per unit time normally measured in millirem per hour (mR/hr)
Efficiency – The measure of how accurately a piece of measuring equipment (Geiger - Mueller counter or scintillation detector) can detect a specific type of radiation.
Electron Volt (eV) – A unit of energy equivalent to the amount of energy gained by an electron passing through a potential difference of 1 Volt. This measure is used to denote the amount of energy a specific particle or photon has when emitted during decay.
Film Badge – A photographic film used for the detection and measurement of radiation exposure. When used with a series of filters allows for the accurate determination of the radiation dose received by an individual. Usually is worn as a whole body monitor (body badge).
Gamma Radiation – A penetrating electromagnetic radiation generated in the nucleus during radioactive decay. It is identical to an x-ray except for its origin.
Geiger Mueller – A instrument used for the measurement and detection of radiation by using a gas-filled (GM) Counter detector.
Gray (Gy) – An SI unit of absorbed dose equal to 1 joule per kilogram. 1 Gy = 100 rad.
Half-Life – The time required for a given amount of radioactive material to reduce its activity by half through decay. Each nuclide has a unique half-life.
Half Value layer – The thickness of shielding material required to attenuate the gamma radiation emitted by 50%.
Flash Point, high – When the lowest temperature at which vapors above a volatile combustible substance ignite in air when exposed to flame is greater than 300 F.
Flash Point, low – When the lowest temperature at which vapors above a volatile combustible substance ignite in air when exposed to flame is less than 300 F.
Inverse Square Law – The intensity of radiation at a point is inversely proportional to the square of the distance from that source. For example: if the dose rate at 1 cm is 200 mR/hr then at 2 cm it would be 50 mR/hr.
Ionizing Radiation – Any electromagnetic or particulate radiation capable of producing ions when it interacts with matter.
Isotope – Nuclide having the same number of protons by differing in the number of neutrons, they have the same atomic number but different mass number.
Liquid Scintillation – A device used to count the radiation emitted by immersing a labeled sample into a Counter liquid scintillator.
RAD – The special unit of absorbed dose. One rad is equal to an absorbed dose of 100 ergs/gram or 0.01 joule/kilogram. 1 rad = 0.01 Gy
Radiation Worker – A person who through the course of their duties uses or handles radioactive material or radiation-producing equipment.
Radionuclide – A nuclide with an unstable ratio of protons and neutrons that will decay into a more stable state through the emission of radiation.
Radiotoxicity – Term referring to the potential of a radionuclide to cause damage to tissue when ingested.
REM – The special unit of any of the qualities expressed as dose equivalent. The dose equivalent in rems is equal to the absorbed dose in rads multiplied the quality factor. 1 rem = 0.01 sievert.
Restricted Area – Any area where access is limited for the purpose of protecting individuals against undue risk from exposure to radiation and/or radioactive materials.
Scintillator – A substance that absorbs radiation emitted by a radioactive material and releases the equivalent energy in visible photons that can be detected by a photodetector.
Shielding – Any material used to attenuate the radiation produced by a radioactive material. Lead, plexiglass, Lexan and concrete are common materials used.
Sievert (Sv) – The SI unit of any of the qualities expressed as dose equivalent. The dose equivalent in sieverts is equal to the absorbed dose in rads multiplied the quality factor. 1 sievert = 100 rem.
Special Nuclear Material – Plutonium, uranium-233, uranium enriched in the nuclide 233 or in the nuclide 235, and any other material that the Commission, pursuant to the provisions of section 51 of the Act, determines to be special nuclear material, but does not include source material.
TLD – A thermoluminescent dosimeter is made of a crystalline material that stores a fraction of the radiation incident on it and releases this energy in the form of visible photons when heated. TLD's are usually worn as "ring badges".
X-rays – Electromagnetic energy released by bombarding a metallic target with electrons or any electromagnetic radiation produced outside of the nucleus of an atom.
High Flash Point scintillation fluid.
Low Flash Point scintillation fluid.
The Nuclear Regulatory Commission is the branch of the federal government that regulates the use of byproduct material.
The Office of Radiation Safety
Office of Radiation Safety Staff
A committee established by medical and/or broad scope licensees to oversee the use of radioactive materials at the institution. Committee membership is approved by the NRC.
Radiation Safety Officer