Health Physics Questions and Answers - Question 50

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)