Radiological emergency glossaryRadiological emergency glossary
- Acute exposure
A single, brief exposure to radiation, often lasting no more than seven days, that results in biological harm or death. This type of exposure is contrasted with longer, continuous exposure over time (chronic exposure).
A positively charged particle emitted from the nucleus of an atom during radioactive decay. Alpha radiation has low penetrating power and short range but can be harmful if it enters the body through inhalation, ingestion or open wounds.
The smallest part of an element that cannot be broken up by chemical means. The atom consists of a nucleus and one or more orbiting electrons.
A small particle ejected from a radioactive atom during decay. Beta radiation is smaller and faster than alpha radiation and can penetrate human tissue.
- Background radiation
Radiation in the natural environment to which people are exposed every day.
- Chronic exposure
Exposure to a radioactive source over a long period of time, possibly resulting in adverse health effects.
- Cosmic rays
High-energy radiation that comes from outside the Earth's atmosphere.
When radioactive material is present in any place where it is not wanted, such as on or inside structures, objects, areas, or people.
A unit of measurement that describes how much radioactivity a sample of material contains. The curie is based on the observed rate of decay of about one gram of radium, a naturally occurring radioactive metal.
The reduction or removal of contaminating radioactive material from a structure, area, object, or person by a chemical or mechanical process.
A device that is sensitive to radiation and can produce a response signal that may be measured or analyzed. A radiation detection instrument.
A general term for the quantity of radiation or energy absorbed. Rads represent the energy absorbed from the radiation in a gram of any material. The biological dose or dose equivalent is a measure of the biological damage to living tissue from the radiation exposure, and is measured in rem or sieverts.
- Dose equivalent
The product of absorbed dose in tissue multiplied by a quality factor expressed numerically in rems or sieverts.
- Dose rate
The ionizing radiation dose that is delivered per unit of time. It is often used to indicate the level of hazard from a radioactive source.
A small, portable device used to measure and record the radiation dose a person has received.
- Electromagnetic radiation
A traveling wave motion resulting from changing electric or magnetic fields. Types of electromagnetic radiation include x-rays, gamma rays, radar and radio waves.
A negatively charged particle orbiting the nucleus of an atom. Electrons determine the atom's chemical properties.
The simplest form of a chemical. A substance in which all atoms are identical.
Being exposed to ionizing radiation or to radioactive material.
- External radiation
Exposure to ionizing radiation from a radiation source located outside the body.
A type of electromagnetic radiation that is pure energy and is the most penetrating. Gamma rays are the products of nuclear decay processes.
- Geiger counter or G-M Meter
An instrument used to detect and measure radiation. It consists of a gas-filled tube containing electrodes. When ionizing radiation passes through the tube, it produces a pulse of current passes that is measured or counted.
The international system unit of absorbed dose; 1 gray = 100 rads, or an absorbed dose of 1 Joule/kilogram.
- Half life
The time it takes for one half of the atoms of a particular radioactive substance to disintegrate into another nuclear form. Measured half-lives can range from millionths of a second to billions of years.
- High-level waste
Highly radioactive material primarily in the form of spent fuel discharged from commercial nuclear power reactors.
An electrically charged atomic particle, atom or molecule.
The process by which electrons are stripped from an atom.
- Ionizing radiation
Radiation capable of producing ions or charged particles. Ionizing radiation includes alpha, beta, gamma, and X-rays.
- Internal radiation
Exposure to ionizing radiation from a radiation source that is inside the body.
Different forms of atoms of the same element. They have the same number of protons in the nucleus but a different number of neutrons.
Exposure to some form of ionizing radiation.
- Lethal dose
The radiation dose expected to cause death to an exposed population to half of those exposed within one month. A typical LD ranges from 400 to 450 rem (4 to 5 sieverts) received over a very short period of time.
- Low-level waste
Term for a variety of wastes with low levels of radioactivity. Part of the normal operations of private or government laboratories, industries, nuclear fuel cycle facilities, hospitals, and medical, educational, or research institutions that use radioactive materials generates low-level wastes.
Determining the amount of ionizing radiation or radioactive contamination present in a region for the purpose of health or environmental protection. Monitoring, also referred to as surveying, is done for air, surface, ground water, soil and sediment, personnel, and the surface of equipment.
An uncharged particle found in the nucleus of the atom.
- Non-ionizing radiation
A type of radiation, including microwaves and visible light, which does not have enough energy to remove electrons from their orbits around atoms.
An elementary particle with a positive charge located in the nucleus of an atom.
The unit of radiation absorbed dose, which is the amount of energy from any type of ionizing radiation deposited in any medium.
Energy given off by atoms in a moving or changing state. The transmission of energy through space. Radiation can take form as electromagnetic waves, such as heat, light, X-rays, or gamma rays, or streams of particles such as alpha particles, beta particles, neutrons or protons.
- Radioactive decay
Change in an atom by the spontaneous emission of alpha, beta, or gamma radiation emission or by electron capture; also known as radioactive disintegration and radioactivity. The change results in a less energetic, more stable nucleus.
The spontaneous emission of particles or high-energy radiation from the nucleus of an unstable atom.
- Radioactive materials
Any material containing radioactive atoms.
A unit that measures the effects of ionizing radiation on humans. The dose equivalent in rems is equal to the absorbed dose in rads multiplied by the quality factor of the type of radiation.
The unit measuring exposure to X-rays or gamma rays.
- Sealed source
Radioactive material or byproduct that is sealed in an impervious container designed to prevent leakage or escape of the material.
The international standard unit of dose equivalent. One Sv is equal to 100 rem.
A very high-energy form of penetrating electromagnetic radiation that has a wavelength much shorter than that of visible light. They are similar to gamma rays, but do not come from the electrons surrounding the nucleus of the atom, not the nucleus itself.