RE: Ra, 25 mrem/y

["Frame, Paul" <FrameP@orau.gov>]

Otto Raabe wrote:

> Hence, the only way to get near 25 mrem per year from 
> 0.7 pCi/g above background levels would be to have a >vary large area and
quantity of soil contaminated to >this level so that a person might be able
to live
> totally in this contaminated micro-environment. 

Absolutely. No question here. Unfortunately this is exactly the assumption
used in the NRC's DandD  residential scenario: a family moves onto
contaminated property, builds a home there and obtains all their  food from
onsite sources(water, vegetables, fruits, milk, meet, fish etc.) RESRADs
approach is essentially the same. 

The residential scenario is not intended to be likely, just possible. I'm
not happy about it - the money spent cleaning up radium at such low levels
would be better spent elsewhere. 

Still, its not unrealistic to imagine a home being built on radium
contaminated soil. I think some 5000 residential properties were included in
UMTRA.  And when a home is built on contaminated soil, or such soil is used
as backfill, the radon levels in the home could be quite high, it wouldn't,
as you suggest, be diluted by the atmosphere.

I must disagree with the statement that radium is only responsible for a
very small fraction of the  annual 39 mrem exposure due to radionuclides in
the body. The K-40 is responsible for 18-20 mrem. Where dose the other 19-21
mrem come from? Table 7.17 in NCRP 94 attributes (to the soft tissues - so
we can forget the bone's weighting factor):
 3 uSv from Ra-226, 7 uSv from Rn-222, and 140 uSv from Pb-210 - Po-210.
This is roughly 150 uSv or 15 mrem. Not, in my book, a very small fraction
of 39. But its friday, I have other things on my mind, my reading glasses
are at home, and I might be misreading the table. 

I'm off till January. Best wishes for the holidays Otto. That also goes for
everyone else who has had the fortitude to read this far down in my post.

paul  
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html