United States Nuclear Regulatory Commission - Protecting People and the Environment

U.S. Nuclear Regulatory Commission

Question 106: (a) Are there no limits on airborne

radioactivity concentrations in the controlled area, other

than de facto limits for public dose to keep dose rates

less than 2 mrem in an hour? (b) Would stack effluents

creating temporary airborne radioactivity concentrations

greater than DAC levels in the controlled areas be allowed,

as long as the public dose criteria of 10 CFR 20.1301 are

met? (c) It appears that these areas would not need to be

"posted" or controlled, since there are not any 10 CFR Part

20 airborne radioactivity concentration limits for

controlled areas. Is this correct?

Answer: (a) There are no limits on concentrations of

airborne radioactive materials in controlled areas that are

expressed in terms of concentrations. However, both the

occupational dose limits (for individuals who receive an

occupational dose in a controlled area) and the dose limits

for an individual member of the public (when in a

controlled area) indirectly limit the concentrations of

radioactive material in controlled areas. Note that for

members of the public the 100 mrem in a year limit applies.

The 2 mrem in an hour limit does not apply in a controlled

area. This limit applies only in an unrestricted area.

(b) Yes.

(c) There may be "airborne radioactivity areas" within

controlled areas that need to be posted. See the answer to

Question 27. (Reference: 10 CFR 20.1301, 10 CFR 20.1201)

Page Last Reviewed/Updated Thursday, March 29, 2012