U.S. Nuclear Regulatory Commission

Question 48: In 10 CFR 20.1301 (a) (2), does ". . . 0.002

rem (0.02 mSv) in any one hour" apply to the dose in any

single hour or can it apply to the average over a discrete

period of time.

Answer: The phrase "0.002 rem in any one hour" means a

cumulative dose of 0.002 rem in any period of 60

consecutive minutes regardless of the dose rates within

that 60-min. period. It does not mean a dose rate, in

units of rems per hour, obtained by averaging over a time

period greater than, or less than, one hour. (Reference:

10 CFR 20.1301 (a) (2))