Characteristic X-ray: X-rays that are characteristic of the element in which they are produced.
Their emission results from the rearrangement of electrons in the shells of excited atoms.
Contamination: Undesired (e.g., radioactive or hazardous) material that is deposited on the
surface of, or internally ingrained into, structures or equipment, or that is mixed with another
Radioactive Contamination: A radioactive substance dispersed in materials or places
where it is undesirable.
Fixed Contamination: Radioactivity remaining on a surface after repeated
decontamination attempts fail to significantly reduce the contamination level.
Removable Contamination: That fraction of the radioactive contamination present on a
surface that can be transferred to a swipe tab by rubbing with moderate pressure.
Surface Contamination: The deposition and attachment of radioactive materials to a
surface, also the resulting deposit.
Continuous Air Monitor (CAM): Instrument that continuously samples and measures the levels of
airborne radioactive materials on a "real time" basis and has alarm capabilities at preset levels.
Controlled Area: Any area to which access is managed to protect individuals from exposure to
radiation and/or radioactive materials.
Curie: The unit of activity equal to a rate of 3.7 X 1010 nuclear disintegrations per second.
Decontamination: The reduction or removal of contaminating radioactive material from a
structure, area, object, or person. Decontamination may be accomplished by treating the surface
to remove or decrease the contamination, or by letting the material stand so that the radioactivity
is decreased as a result of natural decay.
Derived Air Concentration (DAC): The airborne concentration that equals the ALI divided by the
volume of air breathed by an average worker for a working year of 2,000 hours (assuming a
breathing volume of 2400 m3). For the radionuclides listed in Appendix C of 10 CFR 835, the air
immersion DACs were calculated for a continuous, non-shielded exposure via immersion in a
semi-infinite atmospheric cloud. The value is based upon the derived airborne concentration
found in Table 1 of the U.S. Environmental Protection Agency's Federal Guidance Report No. 11,
Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for
Inhalation, Submersion, and Ingestion, published September 1988. This document is available
from the National Technical Information Service, Springfield, VA.
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