[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Public Dose



While the asserted basis for the App B numbers is 50 mrem the Table 2
discussion as noted below is ambiguous.  As I understand the current
interpretation the factor of 300 which is divided among (as noted in the rule)
   50  - to related to .1 rem
    3  - to account for exposure time and inhalation rate
    2  - to adjust for age
in effect applies that factor of 2 to the limit adjustment to bring it to
50 mrem.  I believe there was explict discussion somewhere along the line
that admitted that an age based adjustment was not justified (but don't ask
me to find it!).

But the submersion type DAC's do not have this adjustment so they are based
on 100 mrem.
Hence the dose implication of a Table 2 exposure depends on the nature of
the nuclide.
So the bad news is that life is not simple.
The good news is that it does not make any difference.  The EPA study of
NRC licensees documented that no licensee was generating Public Doses in
excess of 1 mrem.  So all this fine print relates to issues analgous to the
number of angels dancing on the head of a pin (unless of course your
inspector is concerned about factors of 2 at small fractions of the limits
like one of mine was).

Bill Lipton wrote.......
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.   
 
*********
And Sandy replied.....
I also expect that if there is such a case where an individual can be 
exposed to the doses above, the regulatory bodies would probably 
have a few things to say, if the faciloity insists that these 
individuals are "members of the public" and not considered as 
occupational workers.

**** I agree with the first part, but keep in mind that it is not the level
or nature of the exposure that determines the 'occupational' status but the
'assigned duties'.  So in theory such an exposure could be Public Dose.
Disclaimer:  the above are the personal musings of the author, and do not
represent any past, present, or future position of NIST, the U.S. government,
or anyone else who might think that they are in a position of authority. 
Lester Slaback, Jr.  [Lester.Slaback@NIST.GOV] 
NBSR Health Physics 
Center for Neutron Research 
NIST
100 Bureau Dr.  STOP 3543 
Gaithersburg, MD  20899-3543 
301 975-5810 
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html