United States Nuclear Regulatory Commission - Protecting People and the Environment

Health Physics Questions and Answers - Question 96

Question 96:

(a) The roentgen (R) is not defined or used in revised Part 20; however, many survey instruments and computer records show dose rates in terms of "mR/h" or "R/h." Will these survey instrument face pieces and computer forms have to be changed when revised Part 20 is implemented?

(b) Most radiation instrumentation is currently calibrated in units of roentgens rather than rads. A roentgen of x- or gamma-radiation in the energy range of 0.1 - 3 MeV produces 0.96 rad in tissue. Will these instruments need to be recalibrated to account for this difference.


(a) No. The survey instruments will not need to be changed. See Question 428 for additional information concerning the use of the unit "roentgen" and its subunits.

(b) No. It may be assumed that one roentgen equals one rem or a more accurate conversion factor may be used.

(References: 10 CFR 20.1003, 10 CFR 20.2101).

Page Last Reviewed/Updated Wednesday, December 13, 2017