United States Nuclear Regulatory Commission - Protecting People and the Environment

U.S. Nuclear Regulatory Commission

Question 50: Does the footnote to 10 CFR 20.1203 mean that

DAC-hours, and not measurements of external dose (using

personal dosimeters), should be used for determining worker

exposures to noble gases?

Answer: No, as clarified in draft Regulatory Guide 8.N8,

the preferred method of determining worker exposure to

noble gases is by radiation dose measurements using

personnel dosimeters. However, such dosimeters may not be

capable of measuring the skin dose resulting from certain

noble gas radionuclides that emit weak beta radiation

(e.g., Xe-133 and Xe-133m). In such cases it is necessary

to calculate the skin dose using measurements of the

concentrations of these noble gases to which the workers

were exposed. (Reference: 10 CFR 20.1203 Footnote)

Page Last Reviewed/Updated Thursday, March 29, 2012