RMS - General definitions concerning health physics and radiation protection A-C

General Definitions used in Health Physics & Radiation Protection

Radioactive Materials Branch

Absorbed dose
The energy imparted by ionizing radiation per unit mass of irradiated material. The units of absorbed dose are the rad and the gray (Gy).

Absorption
The process by which the number of particles or photons entering a body of matter is reduced by interaction with matter. Also the process in which energy is absorbed from the particles or photons even if the number is not reduced.

Accelerator produced material
Any material made radioactive by use of a particle accelerator.

Activity
The rate of disintegration (transformation) or decay of radioactive material. The units of activity are the curie (Ci) and the becquerel (Bq).

Agency
The North Carolina Department of Environment and Natural Resources, Division of Environmental Health, Radiation Protection Section.

Agreement State
Any state with which the United States Nuclear Regulatory Commission has entered into an effective agreement under Subsection 274b. of the Atomic Energy Act of 1954, as amended (73 Stat. 689).

Airborne radioactive material
Any radioactive material dispersed in the air in the form of dusts, fumes, particulates, mists, vapors, or gases.

Airborne radioactivity area
A room, enclosure, or area in which airborne radioactive materials, composed wholly or partly of licensed radioactive material, exist in concentrations: (a) in excess of the derived air concentrations (DACs) specified in Appendix B to 10 CFR �� 20.1001 - 20.2401, or (b) to such a degree that an individual present in the area without respiratory protective equipment could exceed, during the hours an individual is present in a week, an intake of 0.6 percent of the annual limit on intake (ALI) or 12 DAC-hours.

Air-purifying respirator
A respirator with an air-purifying filter, cartridge, or canister that removes specific air contaminants by passing ambient air through the air-purifying element.

Air Sampling
The collection of samples of air to measure the radioactivity or to detect the presence of radioactive material, particulate matter, or chemical pollutants in the air.

ALARA
Acronym for "As Low As is Reasonably Achievable." Means making every reasonable effort to maintain exposures to radiation as far below the dose limits in 15A NCAC 11 as is practical consistent with the purpose for which the licensed or registered activity is undertaken, taking into account the state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of sources of radiation in the public interest.

Alpha Particle
A positively charged particle ejected spontaneously from the nuclei of some radioactive elements. It has low penetrating power and a short range. The most energetic alpha particle will generally fail to penetrate the dead layers of cells covering the skin. Alphas are hazardous when an alpha-emitting isotope is inside the body.

Annual limit on intake (ALI)
The derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year. ALI is the smaller value of intake of a given radionuclide in a effective dose equivalent of five rems (0.05 Sv) or a committed dose equivalent of 50 rems (0.5 Sv) to any individual organ or tissue. (ALI values for intake by ingestion and by inhalation of selected radionuclides are given in Table 1, Columns 1 and 2, of Appendix B to 10 CFR �� 20.1001 - 20.2401).

Assigned protection factor (APF)
The expected workplace level of respiratory protection that would be provided by a properly functioning respirator or a class of respirators to properly fitted and trained users. APF can be divided into the ambient airborne concentrations to estimate inhaled air concentrations.

Associated equipment
Equipment used in conjunction with a radiographic exposure device to make radiographic exposures that drives, guides or comes in contact with the sealed source or radiation machines.

Atom
The smallest particle of an element that cannot be divided or broken up by chemical means. It consists of a central core of protons and neutrons, called the nucleus. Electrons revolve in orbits in the region surrounding the nucleus.

Atomic Energy Commission (AEC)
Federal agency created in 1946 to manage the development, use, and control of nuclear energy for military and civilian application. Abolished by the Energy Reorganization Act of 1974 and succeeded by the Energy Research and Development Administration (now part of the U.S. Department of Energy) and the U.S. Nuclear Regulatory Commission.

Authorized representative
An employee of the agency, or an individual outside the agency when the individual is specifically so designated by the agency under Rule .0112 of 15A NCAC 11.

Authorized user
An individual who is authorized by license or registration condition to use a source of radiation.

Background radiation
Radiation from cosmic sources; naturally occurring radioactive materials, including radon (except as a decay product of source or special nuclear material); and global fallout as it exists in the environment from the testing of nuclear explosive devices. "Background radiation" does not include sources of radiation regulated by the agency.

Becquerel
The SI unit of radioactivity. One becquerel is equal to one disintegration per second (s^-1).

Beta
A charged particle emitted from a nucleus during radioactive decay, with a mass equal to 1/1837 that of a proton. A negatively charged beta particle is identical to an electron. A positively charged beta particle is called a positron. Large amounts of beta radiation may cause skin burns, and beta emitters are harmful if they enter the body. Beta particles may be stopped by thin sheets of metal or plastic.

Bioassay (or radiobioassay)
The determination of kinds, quantities or concentrations, and, in some cases, the locations of radioactive material in the human body, whether by direct measurement (in vivo counting) or by analysis and evaluation of materials excreted or removed from the human body.

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.

Cabinet radiography using radiation machines
Industrial radiography using radiation machines, which is conducted in an enclosed, interlocked cabinet, such that the radiation machine will not operate unless all openings are securely closed, and which cabinet is so shielded that every location on the exterior meets conditions for an unrestricted area as specified in Rule .1611 of the North Carolina Regulations for Protection Against Radiation.

Calibration
The adjustment, as necessary, of a measuring device such that it responds within the required range and accuracy to known values of input.

Charged Particle
An ion. An elementary particle carrying a positive or negative electric charge.

Class (or lung class or inhalation class)
A classification scheme for inhaled material according to its rate of clearance from the pulmonary region of the lung. Materials are classified as D, W, or Y, which applies to a range of clearance half-times as follows:

CLASSIFICATION OF INHALED MATERIAL
Class	Clearance half-time
Class D (Day)	less than 10 days
Class W (Weeks)	10 days to 100 days
Class Y (Years)	greater than 100 days

Collective dose
The sum of the individual doses received in a given period of time by a specified population from exposure to a specified source of radiation.

Collimator
A device used to limit the size, shape, and direction of the primary radiation beam.

Committed dose equivalent (H_T,50)
The dose equivalent to organs or tissues of reference (T) that will be received from an intake of radioactive material by an individual during the 50-year period following the intake.

Committed effective dose equivalent (H_E,50)
The sum of the products of the weighting factors applicable to each of the body organs or tissues that are irradiated and the committed dose equivalent to these organs or tissues (H_E,50 = w_TH_T,50).

Constraint (dose constraint)
A value above which specified licensee actions are required.

Control device
The control cable, the protective sheath and control drive mechanism used to move the sealed source from the shielded position in the radiographic device or camera to an unshielded position outside the device for the purpose of making a radiographic exposure. Commonly called a crank-out.

Controlled area
An area, outside of a restricted area but inside the site boundary, access to which can be limited by the licensee or registrant for any reason.

Cosmic Radiation
Penetrating ionizing radiation, both particulate and electromagnetic, originating in outer space. Secondary cosmic rays, formed by interactions in the earth's atmosphere, account for about 45 to 50 millirems of the 360 millirems background radiation that an average individual receives in a year.

Critical Group
Means the group of individuals reasonably expected to receive the greatest exposure to residual radioactivity for any applicable set of circumstances.

Curie
The special unit of radioactivity. One curie is equal to 3.7 x 10¹⁰ disintegrations per second = 3.7 x 10¹⁰ becquerels = 2.22 X 10¹² disintegrations per minute.