Glossary of Terms

A heavy particle emitted from the nucleus of an atom. It consists of two protons and two neutrons, which is identical to the nucleus of a helium atom without orbital electrons. These heavy charged particles lose their energy very rapidly in matter. Thus, they are easily shielded by paper or the surface layer of skin. Alpha particles are only hazardous when they are internally deposited.

ALARA

Acronym for "As Low As Reasonably Achievable." It means making every reasonable effort to maintain exposures to ionizing radiation as far below the dose limits as practical. Be consistent with the purpose for which the licensed activity is undertaken, taking into account the state of technology, the economics of improvements in relation to state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations. These means are in relation to utilization of nuclear energy and licensed materials in the public interest.

Analyte

The specific radioisotope measured in a radiochemical analysis. For example, tritium, Sr-90, and U-238 are analytes.

Background Radiation

Radiation that occurs naturally in the environment. Background radiation consists of cosmic radiation from outer space, radiation from the radioactive elements in rocks and soil, and radiation from radon and its decay products in the air we breathe.

Baseline Samples

Environmental samples taken in areas unlikely to be affected by any facilities handling radioactive materials.

Becquerel

A unit, in the International System of Units (SI), of measurement of radioactivity equal to one transformation per second.

Beta Particle

A high-speed particle emitted from the nucleus, which is identical to an electron. They can have a –1 or +1 charge and are effectively shielded by thin layers of metal or plastic. Beta particles are generally only hazardous when they are internally deposited.

CFR

Code of Federal Regulations

Curie

The basic unit of activity. A quantity of any radionuclide that undergoes an average transformation rate of 37 billion transformations per second. One curie is the approximate activity of 1 gram of radium. Named for Marie and Pierre Curie, who discovered radium in 1898.

Decay, Radioactive

The decrease in the amount of any radioactive material with the passage of time, due to the spontaneous emission from the atomic nuclei of either alpha or beta particles, often accompanied by gamma radiation.

Detection Level

The minimum amount of a substance that can be measured with a 95% confidence that the analytical result is greater than zero.

Dose

A generic term that means absorbed dose, equivalent dose, effective dose, committed equivalent dose, committed effective dose, or total effective dose.

DWS

Drinking Water Standard

Fallout

Radioactive materials that are released into the earth’s atmosphere following a nuclear explosion or atmospheric release and eventually fall to earth.

Gamma Ray

Electromagnetic waves or photons emitted from the nucleus of an atom. They have no charge and are best shielded by thick layers of lead or steel. Gamma energy may cause an external or internal radiation hazard. (X-rays are similar to gamma radiation but originate from the outer shell of the atom instead of the nucleus).

Gross Alpha / Gross Beta

A screening test that reports alpha particle activity in a sample. The test is not intended to identify specific radioisotopes. The tests are primarily used to evaluate trends. In addition, screening tests are used to determine if further radioisotope specific analysis is necessary; and if radioisotope analyses has been carried out, to determine if the activities from specific radioisotopes account for all of the activity found in the screening test.

Half-life

The time in which half the atoms of a particular radioactive substance disintegrate to another nuclear form. Measured half-lives vary from millionths of a second to billions of years. Also called physical half-life.

ICRP

International Commission on Radiation Protection

Ionizing Radiation

Any radiation capable of displacing electrons from atoms or molecules, thereby producing ions. Examples: alpha, beta, gamma, x-rays, and neutrons.

Isotope

One of two or more atoms with the same number of protons, but different numbers of neutrons, in the nuclei.

Lower Limit of Detection (LLD)

The smallest amount or concentration of a radioactive element that can be reliably detected in a sample.

NCRP

National Council for Radiation Protection

Quality Assurance

All those 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

A component of Quality Assurance; comprises all those actions necessary to control and verify that a material, process, or product meets specified requirements.

Quality Factor (Q)

A numerical factor assigned to describe the average effectiveness of a particular kind (and sometimes energy) of radiation in producing biological effects on humans.

Rad

The special unit of absorbed dose. It is a measure of the energy absorbed per mass of material. One rad is equal to an absorbed dose of 0.01 J kg-1 (1 rad = 0.01 gray).

Radioactivity

The process of undergoing spontaneous transformation of the nucleus, generally with the emission of alpha or beta particles, often accompanied by gamma rays. The term is also used to designate radioactive materials.

Radioisotope

A radioactive isotope; i.e., an unstable isotope that undergoes spontaneous transformation, emitting radiation. Approximately 2500 natural and artificial radioisotopes have been identified.

Radionuclide

A radioactive nuclide.

Rem

The special unit of dose equivalent. The dose equivalent in rem is equal to the absorbed dose in rad multiplied by a quality factor that accounts for the biological effect of the radiation. (1 rem = 0.01 sievert).

Replicate Sample

Two or more samples from one location that are analyzed by the same laboratory.

Roentgen

A unit of exposure to ionizing radiation. 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 after Wilhelm Roentgen, German scientist who discovered x-rays in 1895.

Split Sample

A sample from one location that is divided into two samples and analyzed by different laboratories.

TLD

Thermoluminescent Dosimeters

WAC

Washington Administrative Code

X-ray

Electromagnetic waves or photons emitted from the outer shell of the atom instead of the nucleus. They have no charge and are best shielded by thick layers of lead or steel. X-ray energy may cause an external or internal radiation hazard.