RSDS include information such as the type of emitted radiation, properties of radionuclides such as decay mode, energy, half-life, ALI, DAC, etc. This information assists the user in handling radioactive materials safely while minimizing danger to public health and the environment.
RSDS data used for radiation protection calculations shall be obtained from regulatory authority documents or from reputable scientific organizations (1-3). Data for radionuclides should first be vetted through the University of Utah- Environmental Health and Safety – Radiation Safety Division. Radiation Procedures and Records (RPR), RPR-10 – Radionuclide Data 9/2013(1) before being used for regulatory compliance purposes.
Definitions
Radionuclide (4): An unstable isotope of an element that decays or disintegrates spontaneously, thereby emitting radiation. Approximately 5,000 natural and artificial radioisotopes have been identified.
Radiation (4): Alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions. Radiation, as used in 10 CFR Part 20, does not include non-ionizing radiation, such as radio- or microwaves, or visible, infrared, or ultraviolet light (see also 10 CFR 20.1003).
Activity (4): The rate of disintegration (transformation) or decay of radioactive material per unit time. The units of activity (also known as radioactivity) are the curie (Ci) and the becquerel (Bq).
Dose (4): The National Council on Radiation Protection and Measurements estimates that an average person in the United States receives a total annual dose of about 0.62 rem (620 millirem or 6.2 millisieverts) from all radiation sources, a level that has not been shown to cause humans any harm. Of this total, natural background sources of radiation—including radon and thoron gas, natural radiation from soil and rocks, radiation from space, and radiation sources that are found naturally within the human body—account for about 50 percent. Medical procedures such as computed tomography (CT) scans and nuclear medicine account for about another 48 percent. Other small contributors of exposure to the U.S. population include consumer products and activities, industrial and research uses, and occupational tasks. The maximum permissible yearly dose for a person working with or around nuclear material is 5 rem (50 millisieverts).
TEDE (4): The sum of the effective dose equivalent (for external exposures) and the committed effective dose equivalent (for internal exposures).
Half-Life (4): The time required for half the atoms of a particular radioisotope to decay into another isotope. A specific half-life is a characteristic property of each radioisotope. Measured half-lives range from millionths of a second to billions of years, depending on the stability of the nucleus. Radiological half-life is related to, but different from, the biological half-life and the effective half-life.
Isotope (4) : Two or more forms (or atomic configurations) of a given element that have identical atomic numbers (the same number of protons in their nuclei) and the same or very similar chemical properties but different atomic masses (different numbers of neutrons in their nuclei) and distinct physical properties. Thus, carbon-12, carbon-13, and carbon-14 are isotopes of the element carbon, and the numbers denote the approximate atomic masses. Among their distinct physical properties, some isotopes (known as radioisotopes) are radioactive because their nuclei emit radiation as they strive toward a more stable nuclear configuration. For example, carbon-12 and carbon-13 are stable, but carbon-14 is unstable and radioactive.
Radioactive Decay (4): The spontaneous transformation of one radionuclide into one or more decay products (also known as “daughters”). This transformation is commonly characterized by the emission of an alpha particle, a beta particle, or gamma ray photon(s) from the nucleus of the radionuclide. The rate at which these transformations take place, when a sufficient quantity of the same radionuclide is present, depends on the half-life of the radionuclide. Some radionuclides (e.g., hydrogen-3, also known as “tritium”) decay to stable daughters that are not radioactive. However, other radionuclides (e.g., uranium-238) decay to radioactive daughters (e.g., thorium-234) and may be part of a radioactive decay chain consisting of two or more radionuclides linked in a cascading series of radioactive decay.
ALI (3): means the activity of a single radionuclide (expressed in millicuries [mCi])
which, if ingested or inhaled by a single individual, would result in an effective dose equivalent equal to
that individual of a whole-body dose of 5 rem. The ALI is dependent on the route of intake. For most
laboratory purposes, involving contamination control and bioassay procedures, the ALI for ingestion is
used. Ingestion is the most common route of accidental intake of radionuclides. For gases, the
inhalation ALI is used.
DAC (2): 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 (with an inhalation rate of 1.2 cubic meters of air per hour), results in an intake of one annual limit on intake (ALI). Established DAC values are given in Table 1, Column 3, of Appendix B to Title 10, Part 20, of the Code of Federal Regulations (10 CFR Part 20), “Standards for Protection Against Radiation.”
Radiation Shielding (4): Reduction of radiation by interposing a shield of absorbing material between any radioactive source and a person, work area, or radiation-sensitive device.
Resource
(1) University of Utah- Environmental Health and Safety – Radiation Safety Division. Radiation Procedures and Records (RPR), RPR-10 – Radionuclide Data 9/2013
(2) U.S.NRC-Appendix B to Part 20—Annual Limits on Intake (ALIs) and Derived Air Concentrations (DACs) of Radionuclides for Occupational Exposure; Effluent Concentrations; Concentrations for Release to Sewerage. Accessed Online: https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-appb.html 9/25/2024
(3) Utah Department of Environmental Quality (DEQ) – Division of Waste Management and Radiation Control. R313-15: Standards for Protection Against Radiation. Accessed Online: https://adminrules.utah.gov/public/rule/R313-15/Current%20Rules? 9/26/2024
(4) U.S.NRC-NRC Library: Glossary-Accessed Online: https://www.nrc.gov/reading-rm/basic-ref/glossary.html 9/27/2024
