Radioactive Materials Branch
General Definitions used in Health Physics & Radiation Protection

H

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

Half-life, Biological
The time required for the body to eliminate one half of the material taken in by natural biological means.

Half-value, layer
The thickness of any given absorber that will reduce the intensity of a beam of radiation to one half of its initial value.

Health Physics
The science concerned with recognition, evaluation, and control of health hazards from ionizing radiation.

Health Physicist
A person who works in the area of environmental health engineering that deals with the protection of the individual and population groups against the harmful effects of ionizing and non-ionizing radiation. The health physicist is responsible for the safety aspects in the design of processes, equipment, and facilities utilizing radiation sources, so that radiation exposure to personnel will be minimized, and will at all times be within acceptable limits.

Helment
A rigid respiratory inlet covering that also provides head protection against impact and penetration.

High radiation area
An area, accessible to individuals, in which radiation levels from sources external to the body could result in an individual receiving a dose equivalent in excess of 0.1 rem (1 mSv) in one hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.

Hood
A means a respiratory inlet covering that completely covers the head and neck and may also cover portions of the shoulders and torso.

Hospital
A facility that provides as its primary functions diagnostic services and intensive medical and nursing care in the treatment of acute stages of illness.

Human use
The internal or external administration of radiation or radioactive materials to human beings.

I

Individual
Any human being.

Individual monitoring means:

Individual monitoring devices or individual monitoring equipment
Devices designed to be worn by a single individual for the assessment of dose equivalent such as film badges, thermoluminescence dosimeters (TLDs), pocket ionization chambers, and personal ("lapel") air sampling devices.

Industrial radiography
The examination of materials by nondestructive methods utilizing sources of radiation.

Inhalation class
(see "Class" defined above).

Injection Tool
A device used for controlled subsurface injection of radioactive tracer material.

Inspection
An official examination or observation to determine compliance with rules, orders, requirements and conditions of the agency or the Commission.

Internal dose
That portion of the dose equivalent received from radioactive material taken into the body.

Ion

Ionization
The process of adding one or more electrons to, or removing one or more electrons from, atoms or molecules, thereby creating ions. High temperatures, electrical discharges, or nuclear radiations can cause ionization.

Ionization Chamber
An instrument that detects and measures ionizing radiation by measuring the electrical current that flows when radiation ionizes gas in a chamber, making the gas a conductor of electricity.

Ionizing Radiation
Any radiation capable of displacing electrons from atoms or molecules, thereby producing ions.  Some examples are alpha, beta, gamma, X-rays, neutrons. High doses of ionizing radiation may produce severe skin or tissue damage.

Isotope
One of two or more atoms with the same number of protons, but different numbers of neutrons in their nuclei. Thus, carbon-12, carbon-13, and carbon-14 are isotopes of the element carbon, the number denoting the approximate atomic weights. Isotopes have very nearly the same chemical properties, but often different physical properties (for example, carbon-12 and -13 are stable, carbon-14 is radioactive).

J

Joule
The SI unit of work and energy.  It represents the work done when a force on one (1) Newton is exerted through a distance of one (1) meter. 

K

K-capture
The radioactive transformation process by which one of the extra-nuclear electrons is captured by the nucleus, and unites with an intra-nuclear proton to form a neutron and emit a neutrino.

Kilo-
A prefix that multiplies a basic unit by 1,000.

L

Lethal Dose 50/30 (LD_50/30)
The dose of radiation expected to cause death within 30 days to 50% of those exposed.   Generally accepted to range from 400 to 600 rem (4-6 Gray)received over a short period of time.

Lens Dose Equivalent or "LDE"
Applies to the external exposure of the lens of the eye and is taken as the dose equivalent at a tissue depth of 0.3 cm (300 mg/cm²)

License
Except where otherwise specified, means a license issued pursuant to Section .0300 of the North Carolina Regulations for Protection Against Radiation.

Licensee
Any person who is licensed by the agency pursuant to Section .0300 of the North Carolina Regulations for Protection Against Radiation.

Licensing state
Any state designated as such by the Conference of Radiation Control Program Directors, Inc. Unless the context clearly indicates otherwise, use of the term Agreement State in this Chapter shall be deemed to include licensing state with respect to naturally occurring and accelerator produced radioactive material (NARM).

Limits or dose limits
The permissible upper bounds of radiation doses.

Linear Energy Transfer (LET)
The measure of the linear rate of energy absorption by the absorbing medium as the ionizing radiation traversed the medium.

Logging Tool
Means a device used subsurface to perform well-logging.

Logging Supervisor
The person who provides personal supervision of the utilization of sources of radiation at the well site.

Loose-fitting facepiece
A respiratory inlet covering that is designed to form a partial seal with the face.

Lost or missing licensed radioactive material
Licensed radioactive material whose location is unknown. It includes material that has been shipped but has not reached its destination and whose location cannot be readily traced in the transportation system.

Low-level radioactive waste
Means low-level radioactive waste as defined in North Carolina General Statute 104E-5(9a) and includes naturally occurring and accelerator produced radioactive material which is not subject to regulation by the U. S. Nuclear Regulatory Commission under the Atomic Energy Act of 1954, as amended, and is suitable for land disposal under the provisions of 15A NCAC 11 .1200 "Land Disposal of Radioactive Waste."

Lung class
(see "Class" as defined above).