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)