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

Q

Quality factor (Q)
The modifying factor that is used to derive dose equivalent from absorbed dose. Quality factors are provided in the definition of rem below.

Quarter
A period of time equal to one-fourth of the year observed by the licensee or registrant (approximately 13 consecutive weeks), providing that the beginning of the first quarter in a year coincides with the starting date of the year and that no day is omitted or duplicated in consecutive quarters.

R

Rad
The special unit of absorbed dose. One rad is equal to an absorbed dose of 100 ergs/gram or 0.01 joule/kilogram (0.01 gray).

Radiation (ionizing radiation)
Except as otherwise defined in 15A NCAC 11 .1400 of the North Carolina Regulations for Protection Against Radiation, means alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions.

Radiation area
An area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 0.005 rem (0.05 mSv) in one hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.

Radiation dose
Refers to dose.

Radiation machine
Any device capable of producing radiation except devices which produce radiation only from radioactive material.

Radiation safety officer
One who has the knowledge and responsibility to apply appropriate radiation protection rules.

Radiation Safety Officer (for Radiography)
An individual named by the licensee or registrant who has knowledge of, responsibility for, and authority to ensure compliance with appropriate radiation protection rules, standards, and practices on behalf of the licensee or registrant and who meets the requirements of 15A NCAC 11 .0510(g) of this the North Carolina Regulations for Protection Against Radiation.

Radiation Sickness(syndrome)
The complex of symptoms characterizing the disease known as radiation injury, resulting from excessive exposure of the whole body (or large part) to ionizing radiation. The earliest of these symptoms are nausea, fatigue, vomiting, and diarrhea, which may be followed by loss of hair (epilation), hemorrhage, inflammation of the mouth and throat, and general loss of energy. In severe cases, where the radiation exposure has been relatively large, death may occur within two to four weeks. Those who survive six weeks after the receipt of a single large dose of radiation may generally be expected to recover.

Radioactive material
Any material, solid, liquid, or gas, which emits radiation spontaneously.

Radioactive waste disposal facility
Any low-level radioactive waste disposal facility, as defined in G.S. 104E-5(9c), established for the purpose of receiving low-level radioactive waste, as defined in 15A NCAC .1202, generated by another licensee for the purpose of disposal.

Radioactive waste processing facility
Any low-level radioactive waste facility, as defined in G.S. 104E-5(9b), established for the purpose of receiving waste generated by another licensee to be stored, compacted, incinerated or treated.

Radioactivity
The disintegration of unstable atomic nuclei by emission of radiation.

Radiobioassay
See bioassay

Radiographer
Any individual who performs or who, in attendance at the site where sources of radiation are being used, personally supervises industrial radiographic operations and who is responsible to the licensee or registrant for assuring compliance with the requirements of the North Carolina Regulations for Protection Against Radiation and all license or registration conditions.

Radiographer's assistant
Any individual who, under the personal supervision of a radiographer, uses sources of radiation, related handling tools, or survey instruments in industrial radiography.

Radiographic exposure device
Any instrument containing a sealed source fastened or contained therein, in which the sealed source or shielding thereof may be moved, or otherwise changed, from a shielded to unshielded position for purposes of making a radiographic exposure.  Commonly called a camera or projector.

Radium (Ra)
A radioactive metallic element with atomic number 88. As found in nature, the most common isotope has a mass number of 226. It occurs in minute quantities associated with uranium in pitchblende, carnotite, and other minerals.

Radon
An invisible, radioactive gas that occurs naturally in soil. Radon is a daughter of radium and one of the heaviest gases known

Recordable event
Means the administration of the following:

Reference man
A hypothetical aggregation of human physical and physiological characteristics arrived at by international consensus as published by the International Commission on Radiological Protection. These characteristics may be used by researchers and public health workers to standardize results of experiments and to relate biological insult to a common base.

Registrant
Any person who is registered with the agency as required by provisions of these Rules or the Act.

Registration
Registration with the agency in accordance with the North Carolina Regulations for Protection Against Radiation..

Regulations of the U.S. Dept. of Transportation
The regulations in 49 CFR Parts 100-189.

Relative Biological Effectiveness (RBE)
Is a factor expressing the relative effectiveness of radiations with differing linear-energy-transfer (LET) values, in producing a given biological effect.  This unit is now limited to use in radiobiology.

Rem
The special unit of any of the quantities expressed as dose equivalent. The dose equivalent in rems is equal to the absorbed dose in rads multiplied by the quality factor (1 rem = 0.01 sievert). As used in the North Carolina Regulations for Protection Against Radiation, the quality factors for converting absorbed dose to dose equivalent are as follows:

Research and development means:

Respiratory protective device
An apparatus, such as a respirator, used to reduce the individual's intake of airborne radioactive materials.

Restricted area
An area, access to which is controlled by the licensee or registrant for purposes of protecting individuals against undue risks from exposure to radiation and radioactive materials. Restricted area does not include areas used as residential quarters, but separate rooms in a residential building may be set apart as a restricted area.

Roentgen (R)
The special unit of exposure. One roentgen equals 2.58 x 10^-4 coulombs/kilogram of air.

S

Sanitary sewerage
A system of public sewers for carrying off waste water and refuse, but excluding sewage treatment facilities, septic tanks, and leach fields owned or operated by the licensee.

Scintillation Detector
The combination of phosphor, photomultiplier tube and associated electronic circuits used to count light emissions produced in the phosphor by ionizing radiation.

Sealed source
Radioactive material that is permanently bonded, fixed or encapsulated so as to prevent release and dispersal of the radioactive material under the most severe conditions which are likely to be encountered in normal use and handling.

Shallow-dose equivalent (H_s)
As applies to the external exposure of the skin or an extremity, is taken as the dose equivalent at a tissue depth of 0.007 centimeter (7 mg/cm²) averaged over an area of one square centimeter.

SI unit
A unit of measure from the International System of Units as established by the General Conference of Weights and Measures.

Sievert
The SI unit of any of the quantities expressed as dose equivalent. The dose equivalent in sieverts is equal to the absorbed dose in grays multiplied by the quality factor (1 Sv = 100 rems).

Site boundary
That line beyond which the land or property is not owned, leased, or otherwise controlled by the licensee or registrant.

Source material means:

Source of radiation
Any radioactive material, or any device or equipment emitting or capable of producing radiation.

Special form radioactive material
Radioactive material which satisfies the following conditions:

Special nuclear material means:

Special nuclear material in quantities not sufficient to form a critical mass
Means uranium enriched in the isotope uranium-235 in quantities not exceeding 350 grams of contained uranium-235; uranium-233 in quantities not exceeding 200 grams; plutonium in quantities not exceeding 200 grams; or any combination of uranium-235, uranium enriched in uranium-235 and plutonium in accordance with the following formula: For each kind of special nuclear material, determine the ratio between the quantity of that special nuclear material and the quantity specified in the North Carolina Regulations for Protection Against Radiation for the same kind of special nuclear material. The sum of these ratios for all the kinds of special nuclear material in combination shall not exceed unity. For example, the following quantities in combination would not exceed the limitations and are within the formula, as follows:

State
The State of North Carolina.

Stochastic effects
Health effects that occur randomly and for which the probability of the effect occurring, rather than its severity, is assumed to be a linear function of dose without threshold. Hereditary effects and cancer incidence are examples of stochastic effects.

Survey
An evaluation of the radiological conditions and potential hazards incident to the production, use, transfer, release, disposal, or presence of sources of radiation. When appropriate, such an evaluation includes a physical survey of the location of sources of radiation and measurements or calculations of levels of radiation, or concentrations or quantities of radioactive material present.

T

Tenth-value Layer (TVL)
The thickness of any given absorber that will reduce the intensity of a beam of radiation to one tenth of its initial value.

Tera-
A prefix that multiplies a basic unit by 1,000,000,000,000 (1x10¹²).

Thermoluminescent Dosimeter (TLD)
A device used to measure radiation by measuring the amount of visible light emitted from a crystal in the detector when exposed to radiation.

These Rules
Chapter 11 of the North Carolina Regulations for Protection Against Radiation.

Total effective dose equivalent (TEDE)
The sum of the deep-dose equivalent (for external exposures) and the committed effective dose equivalent (for internal exposures).

Toxic or hazardous constituent of the waste
The non-radioactive content of waste which, notwithstanding the radioactive content, would be classified as "hazardous waste" as defined in 15A NCAC 13A .0102(a).

Type A quantity
A quantity of radioactive material, the aggregate radioactivity of which does not exceed A₁ for special form radioactive material or A₂ for normal form radioactive material, where A₁ and A₂ are given in Rule .0113 of the North Carolina Regulations for Protection Against Radiation or may be determined by procedures described in Rule .0113 of the North Carolina Regulations for Protection Against Radiation. All quantities of radioactive material greater than a Type A quantity are Type B.

Type B quantity
A quantity of radioactive material that exceeds Type A quantities

U

Unrefined and unprocessed ore
Ore in its natural form prior to any processing, such as grinding, roasting, beneficiating, or refining.

Unrestricted area
An area, access to which is neither limited nor controlled by the licensee or registrant.

Uranium
The last of the naturally occurring elements in the periodic table, Uranium is radioactive.  There are 14 known isotopes, with U-238 being the most abundant (99%).  

V

Very high radiation area
An area, accessible to individuals, in which radiation levels could result in an individual receiving an absorbed dose in excess of 500 rads (5 grays) in one hour at one meter from a radiation source or from any surface that the radiation penetrates. At very high doses received at high dose rates, units of absorbed dose (e.g., rads and grays) are appropriate, rather than units of dose equivalent (e.g., rems and sieverts).

W

Waste
Means low-level radioactive waste as defined in G.S. 104E-5(9a) and includes licensed 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, except as defined differently in Rule .1202 of this Chapter.

Waste, Class A
Is defined in Rule .1650 of the North Carolina Regulations for Protection Against Radiation.

Waste, Class B
Is defined in Rule .1650 of the North Carolina Regulations for Protection Against Radiation.

Waste, Class C
Is defined in Rule .1650 of the North Carolina Regulations for Protection Against Radiation.

Week
Seven consecutive days starting on Sunday.

Weighting factor ( w_T) for an organ or tissue (T)
The proportion of the risk of stochastic effects resulting from irradiation of that organ or tissue to the total risk of stochastic effects when the whole body is irradiated uniformly. For calculating the effective dose equivalent, the values of w_T are:

Whole body
For purposes of external exposure, whole body means the head, trunk (including male gonads), arms above the elbow, or legs above the knee.

Worker
An individual engaged in work under a license or registration issued by the agency and controlled by a licensee or registrant, but does not include the licensee or registrant.

Working level (WL)
Any combination of short-lived radon daughters (for radon-222: polonium-218, lead-214, bismuth-214, and polonium-214; and for radon-220: polonium-216, lead-212, bismuth-212, and polonium-212) in one liter of air that will result in the ultimate emission of 1.3 x 10⁵ MeV of potential alpha particle energy.

Working level month (WLM)
An exposure to one working level for 170 hours.

Written directive
An order in writing for a specific patient, dated and signed by an authorized user prior to the administration of a radiopharmaceutical or radiation from a licensed source, except as specified in Sub-item (e) of this definition, containing the following information:

X

X-ray
Penetrating electromagnetic radiation (photon) having a wavelength that is much shorter than that of visible light. These rays are usually produced by excitation of the electron field around certain nuclei. In nuclear reactions, it is customary to refer to photons originating in the nucleus as gamma rays, and to those originating in the electron field of the atom as X-rays. These rays are sometimes called roentgen rays after their discoverer, W.K. Roentgen.

X-ray diffraction
The primary beam from the target of the x-ray tube passes through a collimator and strikes the sample, which diffracts it in a characteristic manner.  This diffraction pattern in measured with a photographic film or a radiation counter.  Primarily used in analytical work.

X-Ray fluorescence
When a sample is irradiated by X-rays at or above the K-shell binding energy, photoelectric absorption will induce characteristic X-ray emissions from the sample.

Y

Year
The period of time beginning in January used to determine compliance with the provisions of Section .1600 of the North Carolina Regulations for Protection Against Radiation. The licensee or registrant may change the starting date of the year used to determine compliance by the licensee or registrant provided that the change is made at the beginning of the year and that no day is omitted or duplicated in consecutive years.

Z

Zinc Sulfide Scintillator
One of the older inorganic scintillators, its main use is in the detection of alpha particle and heavy ion detection.  This type of instrument played a key role in Rutherford's experiments, in which alpha particle interactions on a scintillation screen were visually observed through a low power microscope.

NCDENR .  Division of Radiation Protection .  1645 Mail Service Center, Raleigh, NC 27699-1645 . Voice: (919)-571-4141 .  Facsimile: (919) 571-4148 . Questions/Comments?