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

General Definitions used in Health Physics & Radiation Protection

Radioactive Materials Section

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 Radiation Protection.

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 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).

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.

Daughter Products
Isotopes that are formed by the radioactive decay of some other isotope. In the case of radium-226, for example, there are 10 successive daughter products, ending in the stable isotope lead-206.

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.

Declared pregnant woman
A woman who has voluntarily informed the licensee, in writing, of her pregnancy and the estimated date of conception. The declaration remains in effect until the declared pregnant woman withdraws the declaration in writing or is no longer pregnant.

Decontamination
The reduction or removal of contaminating radioactive material from a structure, area, object, or person. Decontamination may be accomplished by:

Decommission
To remove (as a facility) safely from service and reduce residual radioactivity to a level that permits release of the property for unrestricted use and termination of the license.

Deep-dose equivalent (H_d)
As it applies to external whole-body exposure, is the dose equivalent at a tissue depth of one cm (1000 mg/cm²).

Depleted uranium
The source material uranium in which the isotope uranium-235 is less than 0.711 weight percent of the total uranium present. Depleted uranium does not include special nuclear material.

Derived air concentration (DAC)
The concentration of a given radionuclide in air which, if breathed by the reference man for a working year of 2,000 hours under conditions of light work (inhalation rate 1.2 cubic meters of air per hour), results in an intake of ALI. DAC values are given in Table 1, Column 3, of Appendix B to 10 CFR �� 20.1001 - 20.2041).

Derived air concentration-hour (DAC-hour)
The product of the concentration of radioactive material in air (expressed as a fraction or multiple of the derived air concentration for each radionuclide) and the time of exposure to that radionuclide, in hours. A licensee may take 2,000 DAC-hours to represent one ALI, equivalent to a committed effective dose equivalent of five rems (0.05 Sv).

Diagnostic clinical procedures manual
A collection of written procedures governing the use of radioactive material that describes each method by which the licensee performs diagnostic clinical procedures and includes other instructions and precautions. Each diagnostic clinical procedure including but not limited in content to the radiopharmaceutical, dosage and route of administration, shall be approved by an authorized user prior to inclusion in the manual. The radiation safety officer shall ensure that the manual includes the approved written procedure for all diagnostic clinical procedures performed at the facility.

Dose (or radiation dose)
A generic term that means absorbed dose, dose equivalent, effective dose equivalent, committed dose equivalent, effective dose equivalent, or total effective dose equivalent, as defined in other areas in the North Carolina Regulations for Protection Against Radiation.

Dose equivalent (H_T)
The product of the absorbed dose in tissue, quality factor, and all other necessary modifying factors at the location of interest. The units of dose equivalent are the rem and sievert (Sv).

Dosimeter
A portable instrument for measuring and registering the total accumulated dose to ionizing radiation

Dosimetry processor
An individual or an organization that processes and evaluates individual monitoring equipment in order to determine the radiation dose delivered to the equipment.

Effective dose equivalent (H_E)
The sum of the products of the dose equivalent to the organ or tissue (H_T) and the weighting factors (w_T) applicable to each of the body organs or tissues that are irradiated (H_E = w_TH_T).

Effective Half-life
The time required for the amount of a radioactive element deposited in a living organism to be diminished 50% as a result of the combined action of radioactive decay and biological elimination.

Electromagnetic Radiation
A traveling wave motion resulting from changing electric or magnetic fields. Familiar electromagnetic radiation range from X-rays (and gamma rays) of short wavelength, through the ultraviolet, visible, and infrared regions, to radar and radio waves of relatively long wavelength. All electromagnetic radiations travel in a vacuum with the velocity of light.

Electron
An elementary particle with a negative charge and a mass 1/1837 that of the proton. Electrons surround the positively charged nucleus and determine the chemical properties of the atom.

Embryo/fetus
The developing human organism from conception until the time of birth.

Entrance (or access) point
Any location through which an individual could gain access to radiation areas or to a source of radiation. This includes entry or exit portals of sufficient size to permit human entry, irrespective of their intended use.

Equipment services
The selling, installation, rebuilding, conversion, repair, inspection, testing, survey or calibration of equipment which can affect compliance with 15A NCAC 11 by a licensee or registrant.

Erg
Is the unit of work done by a force of one (1) dyne acting through a distance of one (1) centimeter. The unit of the erg is expressed as 1 gm-cm²/sec². There are 1 x 10⁷ ergs per Joule.

Exposure head
A device that locates the gamma radiography sealed source in the selected working position. Commonly called a source stop.

External dose
That portion of the dose equivalent received from radiation sources outside the body.

Extremity
Hand, elbow, arm, arm below the elbow, foot, knee, or leg below the knee.

Film Badge
A pack of photographic film used for measurement of radiation exposure for personnel monitoring purposes. The badge may contain two or three films of differing sensitivities, and it may contain a filter that shields part of the film from certain types of radiation.

Field examination
A demonstration of practical application of principles learned in the classroom that shall include use of all appropriate equipment and procedures.

Gamma Ray
High-energy, short wavelength, electromagnetic radiation (a packet of energy) emitted from the nucleus. Gamma radiation frequently accompanies alpha and beta emissions and always accompanies fission. Gamma rays are very penetrating and are best stopped or shielded by dense materials, such as lead or uranium. Gamma rays are similar to X-rays.

Generally applicable environmental radiation standards
Standards issued by the U.S. Environmental Protection Agency (EPA) under the authority of the Atomic Energy Act of 1954 (42 U.S.C. 2D11 et seq;), as amended, that impose limits on radiation exposures or levels, or concentrations or quantities of radioactive material, in the general environment outside the boundaries of locations under the control of persons possessing or using sources of radiation.

Geiger-Mueller Counter
A radiation detection and measuring instrument. It consists of a gas-filled tube containing electrodes, between which there is an electrical voltage, but no current flowing. When ionizing radiation passes through the tube, a short, intense pulse of current passes from the negative electrode to the positive electrode and is measured or counted. The number of pulses per second measures the intensity of the radiation field. It was named for Hans Geiger and W. Mueller, who invented it in the 1920's. It is sometimes called simply a Geiger counter or a G-M counter.

Gray (Gy)
The SI unit of absorbed dose. One gray is equal to an absorbed dose of one joule/kilogram (100 rads).

	1) Treating the surface to remove or decrease the contamination.
	2) Letting the material stand so that the radioactivity is decreased as a result of natural decay.
	3) Covering the contamination to shield or attenuate the radiation emitted.