Re: Question on Public Limits

[LIPTONW@dteenergy.com]

It's difficult to answer a hypothetical question such as this, but I'll try, 
with a few assumptions.  The "radioactive material" that would be within the 
scope of 10CFR20.1301 would be either:  (1) direct radiation exposure from 
sources within the licensee's restricted area, or (2) radiation exposure due 
to gaseous or liquid effluents released from the licensee's restricted area.
 
It is not credible that source (1) would result in skin dose with no deep 
dose.  The limits for effluents would depend on the method the licensee 
chooses to demonstrate compliance, as specified in 10CFR20.1302.  The 2 
choices are:  (1) showing that the TEDE is within the limit - It seems that, 
theoretically, a licensee could choose this method and then ignore skin
dose, 
since TEDE is limited to the deep dose equivalent and the committed
effective 
dose equivalent.  (2) limiting doses to 2 mrem/hr and 50 mrem/yr from
external 
sources AND maintaining effluent concentrations within Table 2 of Appendix B 
at the boundary.  There may be cases where choosing method (1) would result
in 
higher release limits.  In practical terms, however, I can't see the NRC 
allowing this.   
 
While I'm on the topic, it's worthwhile noting that there seems to be a 
contradiction in the basis for the "effluent concentrations" in Table 2 of 
Appendix B.  The first paragraph of the basis for Table 2 states that, "The 
concentration values given in Columns 1 and 2 of Table 2 are equivalent to
the 
radionuclide concentrations which, if inhaled or ingested continuously over 
the course of a year, would produce a total effective dose equivalent of
0.05 
rem..."  However, the third paragraph of this basis states:  "The air 
concentration values listed in Table 2, Column 1, were derived by one of two 
methods.  For those radionuclides for which the stochastic limit is
governing, 
the occupational stochastic inhalation ALI was divided by 2.4 E9 ml,
relating 
the inhalation ALI to the DAC...and then divided by a factor of 300.  The 
factor of 300 includes the following components:  a factor of 50 to relate
the 
5 rem annual occupational dose limit to the >>>0.1 rem<<< [emphasis is mine] 
limit for members of the public ..."  Thus, in fact the effluent 
concentrations seem to be based on a public dose of 100 mrems/yr for the 
critical age groups.  Thus, if the licensee chose method 2 to demonstrate 
compliance, he could actually expose the critical individuals in the public
to 
150 mrems/yr - 50 mrems external plus 100 mrems CEDE.   
 
Maybe, someone from the NRC could explain this - I can't.   
 
The opinions expressed are strictly mine. 
It's not about dose, it's about trust. 
 
Bill Lipton 
liptonw@dteenergy.com 
 
You wrote: 
 
>10 CFR 20.1301 states that the TEDE to members of the public must not
exceed 
>100 millirem in a year.  If a member of the public can come in contact with 
>radioactive material that delivers a dose of 20 millirem a week to the skin 
>(shallow dose at 7 mg/cm^2) can I apply the weighting factors (listed in 
>20.1003 as remainder in this case) to the dose to find the TEDE , 
 
>OR should I adhere to a dose that is 1/50 of the occupational limits (1000 
>mrem is 1/50 of the skin limit of 50 rem) 
 
>OR does the 100 mrem limit apply regardless (seems it shouldn't since it is 
>TEDE) 
 
>OR am I totally missing something? 
 
>Thank you for your help 
>Tom Johnson 
>tjohnson@radtrain.com 
 

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