Re: Re[2]: Tritium Dose Conversion Factor Confusion

[welch@CEBAF.GOV (welch)]

Ok, I've got to ask the inevitable stupid question, so that someone can flex
their brain a little - 

Earlier Emil said,

>- I should indicate TODE instead CEDE. Although an external dose 
>(rem) will be less for tritium because of it's low energy of beta's, 
>compare to an internal dose. It would lead to different quality 
>factors for internal and external doses.
>
>The tritium has very distinguishing beta's because of their very low 
>energy. This leads to the higher biological effect form small(low)
>energetic beta's with respect to their energy, SINCE TRITIUM IN THE 
>BODY, compare to more(high) energetic beta's with the same respect to 
>their energy. 
>Or higher conversion factor form the absorbed dose to 
>the dose equivalent for low beta's compare to high beta's. 
>For the external dose I would think there should be an opposite 
>relation.

Here's the question:

In the real world, can one even get an external dose from tritium?  Seems
like once you put 7gm/cm^2 absorber in the way (I haven't done the
calculation), it would pretty much be nill.  How many orders of magnitude
smaller than the internal dose must the external dose be before you say it's
inconsequential?  If you have enough H-3 in direct contact with your skin to
cause any measurable or reportable dose, it seems to me you would have a
real mess on your hands (from an internal dose standpoint).  

Again, this is only a common sense "thought game", not result of any
experience, or calculations.

Keith Welch
CEBAF
welch@cebaf.gov
KW