Re: Skin Dose from Multiple Plane Sources

[LIPTONW@detroitedison.com]

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10CFR20.1201 says it all - or at least most of it:  "The assigned deep-dose 
equivalent or shallow-dose equivalent must be for the part of the body 
receiving the highest exposure.  The deep-dose equivalent, eye dose equivalent 
and shallow-dose equivalent may be assessed from surveys or other radiation 
measurements for the purpose of demonstrating compliance with the occupational 
dose limits, if the individual monitoring device was not in the region of 
highest potential exposure, or the results of indiviudal monitoring are 
unavailable." 
Thus, if there are multiple spots of contamination providing skin dose 
associated with one event, the reported skin dose would be the highest.  The 
reported dose for multiple events depends on how detailed your recordkeeping 
is.  If you record exactly where the exposure occurred and can demonstrate 
that the affected areas do not overlap, then only the highest need be 
reported.  If you don't keep detailed records of the exposure location, you 
must add together the highest skin dose from each event.  There is additional 
guidance in the NRC's answer to "question 176" (6th set of questions and 
answers re the new 10 CFR 20):  "...As long as it can be shown that the total 
shallow dose equivalent does not exceed 50 rem at any one location on the skin 
of the whole body there is no violation...." 
Also note 10 CFR20.1003, definition for "Shallow Dose Equivalent":  
"Shallow-dose equivalent, which applies to the external exposure of the skin 
or an extremity, is taken as the dose equivalent at a tissue depth of 0.007 
cemtimeter (7 mg/cm2) averaged over an area of 1 square centimeter." 
  


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Received: 30 Jan 1996 10:41:55                    Sent: 30 Jan 1996 09:40:52
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Subject: Skin Dose from Multiple Plane Sources
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     I am looking for a broad cross section of opinions on the following 
     subject. I have received a couple of different opinions and I also 
     have my own.  I am hoping that if enough opinions are expressed that 
     we should statistically gravitate toward the true answer (interesting 
     concept, huh?).
     
     If a person has multiple plane sources on the same organ (i.e. 
     SDE,WB), how should the dose be reported?
     
     a. Add the cumulative dose from both plane sources since they are both 
     supplying dose to the same organ (skin)
     
     b. Take the highest dose calculated of the two and use it to represent 
     the entire contamination event.
     
     c. Calculate the dose to 1 cm^2 of skin from the highest detector 
     reading (i.e. 15.5 cm^2 GM) and use it to represent the entire 
     contamination event.
     
     
     
     Please feel free to refer to existing reference documents, none of 
     which I have yet to find.  This is a serious enquiry and I would be 
     more than happy to keep statistics and references based upon responses 
     and later repost the results.  I have my own opinion, but I wouldn't 
     want to bias any of the responses.
     
     
     Glen Vickers
     HP, Nuclear Power Generation
     815-458-2801 ext. 2792
     BRZGV@ccmail.ceco.com



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