Re: Multiple Dosimetry and Weighting Factors

[xug2@rpi.edu (George Xu)]

The footnote for the Table of organ weighting factors  in 10CFR20 refers to
the calculation of Total Effective Dose Equivalent (TEDE) which is the sum
of internal EDE and external DDE (from perosnnel dosimeter reading). It is
this TEDE that is limited to 5 rems a year, according to 10CFR20--an
important issue that is often neglected by many.   A whole body weighting
factor of one is recommended by NRC to weight the DDE.  The reason for NRC
to "invent" this whole body weighting is that the DDE tends to overestimate
the EDE as in the case of multi-badging and large angle exposure.   It opens
the door for other smaller-than-one whole body weighting factors, provided
you can justify it. 

For those who are interested in more information related to this topic,
there is paper on HPJ, and I welcome any comment.

Xu, X. G.; Reece, W. D.; Poston, J. W. A Study of the Angular Dependence
Problem in Effective Dose Equivalent Assessment. Health Physics.
68(2):214-224; 1995.

----------------------------------------------
George Xu
Assistant Professor and RSO
Rensselaer Polytechnic Institute
Troy, NY 12180
Tel: 518-276-4014
Fax: 518-276-4832
Email: xug2@rpi.edu
-----------------------------------------------

>> "For the purpose of weighting the external whole body dose (for adding
>> it to the internal dose) a single weighting factor, wr=1.0, has been
>> specified. The use of other weighting factors for external exposure will
>> be approved on a case-by-case basis until such time as specific guidance
>> is issued."
>
>Unless I am mistaken, I believe that organ dose weighting factor 
>assumes an internal exposure, and the weighting factor then equates 
>that exposure to what a uniform whole body exposure would be, from 
>the internal uptake. The caveat provided by the NRC allows a facility 
>to use a different weighting factor based on data supplied for an 
>individual case, not globally. I don't believe that this section has 
>anything to do with multiple external dosimetry what-so-ever.
>
>I will be interested in other perspectives regarding this.
>
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