Background Radiation: Ionizing radiation that occurs naturally in the environment, including cosmic, terrestrial and radon radiation. Also known as natural background radiation.

Becquerel (Bq): An SI unit of measure for activity. One becquerel equals 1 disintegration per second. Typically, becquerels associated with portable gauges, are expressed in billions (GBq) of a becquerel. There are 37,000,000,000 becquerels in 1 curie.

Beta particle: A high speed particle emitted from the nucleus which is identical to an electron. They can have a -1 (electron) or +1 (positron) charge and are effectively shielded by thin layers of metal or plastic. Beta particles are most hazardous when ingested. Beta particles emitted from the radioactive materials in the gauge are permanently shielded and therefore not used in the operation of the gauge.

Bill of Lading: A shipping document required whenever radioactive material is transported or shipped on public highways, waterways, cargo aircraft or rail. Must be readily visible and accessible to the driver.

Certificate of Competent Authority/IAEA Certificate/Special Form Certificate: A certificate that confirms the manufacture and encapsulation of radioactive material into an impervious container. See: Sealed Source.

Cesium 137 (Cs137): Radioactive isotope of Cesium which decays by beta emission into barium 137m, which in turn emits a photon for measuring density. Cs137 has a half-life of 30.17 years.

Chronic exposure: Exposure to a source of radiation over a longer period of time, typically greater than 24 hours.

Contamination (radioactive): Contamination means that radioactive materials are released in the form of solids, gases or liquids into the environment and contaminate people externally, internally or both.

Controlled area/zone: An area where entry, activities and exit are controlled to help ensure radiation protection and prevent the spread of contamination.

Cosmic Radiation: Radiation produced in outer space that enters the earth’s atmosphere.

Count: Electronic pulse from a radiation detector tube that indicates an ionizing event. Portable nuclear gauges use Geiger-Muller tubes to detect ionizing events.

CFR: Code of Federal Regulations

Chronic dose: A chronic dose means a person received a radiation dose over a long period of time. Example: 300mrem per year.

Chronic Radiation Exposures: Radiation exposures that occur over extended periods of time (greater than 24 hours). Exposure to natural background is a chronic radiation exposure.

Contamination: Radioactive material distributed and in contact with some person, equipment or area. Requires decontamination efforts.

Critical Mass: The minimum amount of fissile material necessary to achieve a self-sustaining nuclear chain reaction. Nuclear gauges only contain non-fissile material and are therefore not capable of creating a chain reaction.

Curie (Ci): The basic measure of radioactivity equal to an average transformation of 37 billion disintegrations per second. One curie is the approximate activity of 1 gram of radium. Named for Marie and Pierre Curie, founders of radium in 1898.

Decay (Radioactive): The decrease of radioactive material, specifically the emission of alpha and beta particles and gamma electromagnetic energy, with the passage of time.

Decontamination (Radioactive): The reduction or removal of radioactive contamination from a structure, object or person.

Detector (Radiation): A device that is sensitive to radiation and can produce a response signal suitable for measurement or analysis. A radiation survey meter.

Dirty bomb: A radiological dispersal device (RDD). A device designed to spread radioactive material by conventional explosives for malevolent purposes. The objective of such a device would be to cause social disruption and panic.

Dose/Dose Rate: The quantity of ionizing radiation deposited into a material, including an organ or tissue, expressed in the terms of the energy absorbed per unit mass of material. The basic unit of absorbed dose is the rad or its SI equivalent, the gray (Gy). The radiation dose delivered per unit of time.

Dose equivalent: A quantity used in radiation protection to place all radiation on a common scale for calculating tissue damage. Dose equivalent is the absorbed dose in grays multiplied by the quality factor. The quality factor accounts for differences in radiation effects caused by different types of ionizing radiation. The sievert is the unit used to measure dose equivalent.

Dosimeter: A small portable instrument such as a film badge or TLD for measuring and recording the total accumulated dose of ionizing radiation person receives.

Effective dose: A dosimetric quantity useful for comparing the overall health affects or irradiation of the whole body. It takes into account the absorbed doses recived by various organs and tissues and weighs them according to present knowledge of the sensitivity of each organ to radiation. It also accounts for the type of radiation and the potential for each type to inflict biological damage. The unit of effective dose is the sievert.

Electromagnetic Radiation: A traveling wave motion that results from changing electric and magnetic fields. Types of electromagnetic waves include short-wave such as x-rays & gamma to ultraviolet, visible & infrared to longer wave such as radar and radio. The gamma ray photons used in a gauge to measure density is a type of electromagnetic radiation.

Electron: Sub-atomic negatively charged particle with very low mass that orbits the nucleus.

Element: All isotopes of an atom that contain the same number of protons.

Emergency Response Sheet: A document that discusses the precautions and emergency actions pertaining to radioactive gauge during transport. An Emergency Response Sheet must be readily visible and available to the driver during transport. Similar to a Material Data Safety Sheet (MSDS).

Encapsulation/Encapsulated: The shielding that encompasses a radioactive material used in a gauge.

Exposure (Radiation): A measure of ionization in air caused by x-rays or gamma rays only. The unit of measure most often used is the roentgen.

Exposure rate: A measure of the ionization produced in air by x-rays or gamma rays per unit of time, frequently expressed in roentgens per hour.

External exposure/irradiation: An exposure received from a source of ionizing radiation outside of the body. Similar to a chest x-ray in that following exposure the individual is not radioactive. Exposure to gamma radiation from the gauge is an external exposure.

Film badge: Dosimetry monitoring device that uses photographic film to measure a person’s radiation dose.

Fissile material: Any material in which neutrons cause a fission reaction.

Fission: The splitting of a nucleus into at least two fragments, accompanied by the release of neutrons and energy. Fission of a nucleus may be initiated by absorption of a neutron or, in some materials, can happen spontaneously.

Fusion: The joining together of two or more less stable nuclei into one more stable nucleus.

Gamma ray photon radiation: High-energy electromagnetic radiation emitted from the nucleus of an atom. Gamma rays have no charge, are very penetrating and are best shielded by lead or steel. Gamma rays can cause internal and external damage. All gamma rays emitted from a given isotope have the same energy, a characteristic that enables scientists to identify which gamma emitters are present in a sample. Gamma rays penetrate tissue farther than do beta or alpha particles but leave a lower concentration of ions in their path to potentially cause cell damage. Very similar to x-rays except that x-rays originate from the outer shell of the atom. The gauge uses gamma ray photons to help measure density.

Geiger-Mueller Detector Tube (G-M tube): A gas filled tube that measures voltage pulses created by ionizing gamma radiation. Used in a gauge to determine density.

Geiger counter: A device that utilizes Geiger-Mueller tubes for detecting and measuring ionizing radiation.  Gauges use GM tubes to help measure density.

Genetic effects: Effects from radiation exposure that are seen in the offspring of the individual.

Gray (Gy): This SI unit is used to measure a quantity called absorbed dose. This relates to the amount of energy actually absorbed in some material and is used for any type of radiation and any material. It does not describe the biological effects of the different radiations. On gray is equivalent to 100 rads.

Half-life: The time during which one-half of a given quantity of a radionuclide undergoes radioactive decay into another nuclear form. A half-life can last from millionths of a second to billions of years.

Half-thickness: The thickness of a slab material that reduces by half the intensity of radiation incident on one side of the slab.

HAZ-MAT Training: Hazardous Materials training required for all individuals preparing or transporting gauges. Initial training is covered in the Gauge Safety Certification class and must be renewed every three years. APNGA promotes and recommends renewal every year.

Health Physics: A interdisciplinary science that includes elements of physics, biology, chemistry, statistics and electronic instrumentation focusing on providing information used to protect individuals from the effects of ionizing radiation.

Helium-3 Detector Tube: A helium-3 gas filled tube used to measure thermalized neutrons. Used in a gauge to determine moisture content.

IAEA: International Atomic Energy Agency.

IAEA Certificate/Certificate of Competent Authority/Special Form Certificate: A certificate that confirms the manufacture and encapsulation of radioactive material into an impervious container. See: Sealed Source.

Irradiation: Exposure to radiation.

Ingestion: Swallowing radionuclides by eating or drinking.

Inhalation: Breathing in radionuclides.

Internal exposure: An exposure received from a source of ionizing radiation inside of the body.

Inverse Square Law: The relationship that states that electromagnetic radiation intensity is inversely proportional to the square of the distance from a point source. In other words, roughly speaking, as you double your distance from a radioactive source your exposure is reduced to ¼.

Ion: A charged atom or particle. An atom that has fewer or more electrons than protons. Nuclear radiation can cause ionization.

Ionization: A process in which an atom loses or gains one or more electrons thereby forming an ion.

Ionizing radiation: Radiation that is sufficiently energetic to ionize the matter (remove electrons from the atoms thereby producing ions) through which it moves. Alpha, beta, gamma and neutron are all forms of ionizing radiation.

Irradiation: Exposure to radiation.

Isotope: A variation of a element with the same number of protons, but different number of neutrons.

Natural background radiation: Radiation that exists naturally in the environment. It includes cosmic and solar radiation, radiation radioactive materials present in rocks and soil, and radioactivity that is inhaled or ingested.

Neutron: Neutral sub-atomic particle located in the nucleus of an atom/element.

Non-Agreement State: A state under the direct rules and regulations of the NRC.

Nondestructive testing: Testing that does not destroy the object under examination.

Non-ionizing radiation: Having lower energy and longer wavelengths than ionizing radiation it is not strong enough to affect the structure of atoms, but it is strong enough to heat tissue and cause harmful biological effects. Examples are radio waves, microwaves, visible light and infrared.

Notice to Employees Poster: A required information poster that must be available/posted for all employees of a company using gauges. This poster can be obtained from the licensing agency.

NRC: Nuclear Regulatory Commission. Federal licensing and regulatory body that oversees the use of radioactive materials in the United States.

Nuclear energy: The heat energy produced by the process of nuclear fission within a nuclear reactor or by radioactive decay.

Nuclear reactor: A device in which a controlled , self-sustaining nuclear chain reaction can be maintained with the use of cooling to remove generated heat.

Nucleus: The central part of an atom that contains the neutrons and protons. The nucleus is the heaviest part of the atom.

Penetrating radiation: Radiation that can penetrate the skin and reach internal organs and tissues. Photons (x-rays & gamma rays) and neutrons are penetrating radiations. Alpha and beta particles are not considered penetrating radiation.

Photon: A discrete packet of pure electromagnetic energy that, when interacting at the molecular or atomic level, acts more like a particle rather than an energy wave. Photons have no mass and travel at the speed of light. Gamma rays and x-rays are photons.

Placards/Placarding: Radioactive lll labels that must be used displayed on the outside of a vehicle for higher quantity devices. Moisture density gauges are Radioactive ll and therefore do not require placarding. DO NOT PLACARD A VEHICLE that is transporting a moisture density gauge as those covered by this website.

Proton: A small positively charged particle found in the nucleus. The number of protons in a given atom determines the chemical identity of the element.

Quality Assurance: Planned and systematic actions necessary to provide adequate confidence that a facility, structure, system or component will perform satisfactorily and safely in service.

Quality Control: Actions necessary to control and verify that a material, process or product meets specified requirements.

Quality Factor (QF): A numerical factor describing the average effectiveness of a particular type or energy of radiation in producing biological effects on humans. The multiplier assigned to a given type of radiation. Multiply the Q x rad to determine rem. A factor that converts the absorbed dose (rad or gray) to biological damage/dose equivalent (rems).

Rad (radiation absorbed dose): A basic unit of absorbed dose that measures the energy absorbed by the body. It does not describe the biological effects of different radiations. One rad equals the dose delivered to an object of 100 ergs of energy per gram of material. It is being replaced by the gray (Gy), which is equivalent to 100 rad.

Radiation: Energy in transit in the form of high speed particles and electromagnetic waves. Electromagnetic waves, including visible light, radio, television, ultra violet (UV) and microwaves, are all types of radiation that do not cause ionizations of atoms because they do not carry enough energy to separate molecules or remove electrons form atoms. These are all forms of non-ionizing radiation. Ionizing radiation is a very high energy form of electromagnetic radiation that has enough energy to remove tightly bound electrons from their orbits around atoms. Alpha, beta, gamma ray and neutron radiation are all ionizing radiation.

Radiation dose: The quantity of radiation energy deposited into an object or medium, divided by the mass of the object or medium. The radiation dose is ionizing radiation. Ionizing radiation doses can be expressed as an absorbed dose, equivalent dose, or effective dose. The basic unit of absorbed dose is the rad or its SI equivalent, the gray (Gy).

Radiation exposure: The act of being exposed to radiation. Also referred to as irradiation. Formally in radiation detection and measurement, radiation exposure is related to the ability of photons to ionize air.

Radiation sickness: See Acute Radiation Syndrome (ARS).

Radiation source: Radioactive material packaged to use the radiation it emits.

Radiation warning symbol: A universally recognized magenta or black trefoil on a yellow background that must be displayed where radioactive materials are present or where certain doses of radiation could be received.

Radioactive: Elements that are unstable and transform spontaneously (decay) through the emission of ionizing radiation, a process known as radioactive decay.

Radioactive contamination: Radioactive material distributed and in contact with some person, equipment or area. Requires decontamination efforts.

Radioactive decay: The spontaneous disintegration of the nucleus of an atom.

Radioactive material: Any material that contains radioactive atoms.

Radioactivity: Process of spontaneous transformation/breakdown of the nucleus, generally with the emission of alpha or beta particles, usually accompanied by gamma rays. This process is described as decay of the atom.

Radiography: The use of radiation to create images of a subject, especially the internal features of a subject. An example of medical radiography is a dental x-ray. Industrial radiography includes x-rays of pipes and reinforced concrete construction.

Radioisotope: Isotopes of an element that have an unstable nucleus.

Radiological: Related to radioactive materials or radiation. The radiological sciences focus on the measurement and effects of radiation.

Radiological dispersal device (RDD): Also known as a dirty bomb. A device to spread radioactive material for malevolent purposes. The objective of such a device would be to cause social disruption and panic.

Radioisotope: A radioactive/unstable isotope that undergoes spontaneous transformation, emitting radiation.

Radionuclide: An atom with an unstable nucleus which undergoes radioactive decay. A radioactive nuclide.

Radium: A naturally occurring radioactive material (NORM) formed by the decay of uranium and thorium. It occurs at low levels in virtually all rock, soil, water, plants and animals. Radon is a decay product of radium.

Radon: A naturally occurring radioactive gas found in rock, soil and water throughout the United States. Radon is the largest source of exposure to people from naturally occurring radiation.

Reciprocity: The act of one licensing agency honoring the license of another agency. Companies desiring to use their gauges outside of their own state must notify and receive permission to carry the gauge into another state. License holders in a NRC regulated state can use their gauges in another NRC state without obtaining reciprocity permission. License holders in an Agreement State may also need to obtain reciprocity before entering a NRC regulated area such as a military installation.

Regulations: The rules and requirements of a license. All license holders must maintain, review and update a copy of the regulations from their regulatory agency.

REM (Roentgen equivalent, man): The special unit of dose equivalent. Not all radiation has the same biological effect, even for the same amount of absorbed dose. The dose equivalent in rem is equal to the absorbed dose in rad multiplied by the quality factor that accounts for the biological effect of the radiation. (1 rem = 0.01 sievert). This relates the absorbed dose in human tissue to the effective biological damage of the radiation. To determine the equivalent dose (in rem) you multiply the absorbed dose (rad) times the quality factor (Q).

RQ – Reportable Quantity: An EPA designation that establishes thresholds for quantities of radioactive materials used in gauges. An RQ designation must appear on the Type A Package Label and shipping papers for gauges that contain Am241 in excess of 10mCi. All moisture density gauges exceed this limit and must therefore show the designation.

Roentgen: A unit of measure to exposure to gamma and x-rays. It is that amount of gamma or x-rays required to produce ions carrying 1 electrostatic unit of electrical charge in 1 cubic centimeter of dry air under standard conditions. Named for Wilhelm Roentgen, discoverer of x-rays in 1895.

Safety: Prevention of damage, human error and other inadvertent acts that result in accidental radiation exposure.

Sealed source: A radioactive source, sealed in an impervious container that has sufficient mechanical strength to prevent contact with and dispersion of the radioactive material under the conditions of use and wear for which it was designed. May be classified “Special Form” on shipping papers and packages.

Security: Prevention of theft, sabotage and other malevolent acts involving radiation sources.

Shielding: Any effective material between a radiation source and a potentially exposed person that reduces exposure.

SI: International System of Units, also known as the metric system.

Sievert (Sv): The sievert is a SI unit used to derive a quantity called dose equivalent or equivalent dose. This relates the absorbed dose in human tissue to the effective biological damage of the radiation. Not all radiation has the same biological effect, even for the same amount of absorbed dose. To determine equivalent dose (Sv), you multiply absorbed dose (Gy) by a quality factor (Q) that is unique to the type of incident radiation. One sievert (sv) is equivalent to 100rem.

Somatic health effects: The harm that an exposed individual suffers during their lifetime such as radiation induced cancer or sterility. Does not include later generation genetic effects.

Special Form Certificate: A certificate that confirms the manufacture and encapsulation of radioactive material into an impervious container. See: Sealed Source.

Special form radioactive material: Defined in 10 CFR Part 71 as radioactive material that exists as a single solid piece or is encapsulated material that meets certain other requirements.

Stable nucleus: The nucleus of an atom in which forces among its particles are balanced.

Stochastic effect: An effect regardless of dose that assumes there is always some small probability of adverse effects. The effect increases with dose. Cancer is a stochastic effect.

Survey meter: A device used to detect and measure the presence of ionizing radiation.

TEDE – Total Effective Dose Equivalent: The sum of effective dose equivalent from external radiation and the committed effective dose inhaled and ingested radioactive material. Quoted in units of rem.

Terrestrial radiation: Radiation emitted by naturally occurring radioactive materials in the earth. Examples: Uranium, thorium & radon.

TLD: Thermoluminescent Dosimeter. Personnel dosimetry used to measure radiation dose.

Total Body Radiation Syndrome: The response of an organism to acute total body radiation exposure to all organs constituting the organism.

Total Effective Dose Equivalent (TEDE): See TEDE

Transuranic: Pertaining to elements with atomic numbers higher than uranium (92).

Type A Package: The approved case that the gauge must be stored and shipped in.

Type A Package Label: A label that indicates the type of case used to store and ship the gauge.