Re: RADSAFE digest 3137

[Holloway3@aol.com]

Norm Cohen writes:

<< 1. It is impossible to calculate Sr-89 levels in teeth - the half life is
 only 50 days. >>

Norm,

The 50 day half-life of Sr-89 does not of itself make it impossible to 
measure Sr-89 in teeth.  It is not uncommon to measure a radionuclide after 
it has decayed through several half-lives.  Sr-89 was commonly measured in 
enviromental samples (such as milk) during the days of atmospheric weapons 
testing fallout.  If a child is exposed to large quantities of Sr-89 prior to 
shedding his tooth, it is likely that some of it could be detected in teeth.  
The fact that there have been no reports of Sr-89 in teeth suggests that the 
exposure to Sr-89 is nil, rather than than that the 50 day half-life makes it 
impossible to measure.  If the tooth fairy project really wants to show 
exposure from nuclear power plants, then they should be trying to prove the 
presence of Sr-89 in teeth, rather than ignoring it.  Sr-89 is being produced 
continually in an operating reactor and if a plant is emitting substantial 
Sr-90 as the Tooth Fairy project claims, then Sr-89 activity could be present 
in substantial amounts.  It should be possible to detect any appreciable 
amount of Sr-89 in teeth up to 200 days after collection if it was there 
originally.  That is 4 half-lives.   Please give this note to your contacts 
at the Tooth Fairy project and ask them for comment.  In an operating 
reactor, there should be a certain ratio of Sr-89 activity compared to Sr-90 
activity.  I don't know what that ratio is but perhaps someone can tell us.  
In the debris from a nuclear weapon, if my memory is correct, the ratio is 
very high, with there being much more Sr-89 activity than Sr-90 activity.  
Sr-89 is an indicator of a recent fission event, while the long half-life of 
Sr-90 makes its origin highly uncertain. My guess is that the Tooth Fairy 
Project, if it is able to measure Sr-90 accurately, will only be measuring 
old Sr-90 from atmospheric testing.  It will be interesting to see how the 
Tooth Fairy managers propose to distinguish between fallout Sr-90 and that 
from a reactor.  

R. Holloway
Nevada Technical Associates, Inc. 
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