Re: Public In Vivo Iodine-131 & Tritium Urine Levels

[Charles Potter <capotte@sandia.gov>]

     I've also seen an individual contaminated with tritium pass it on to 
     his wife!
     
     "Man is not the creature of circumstances; circumstances are the 
     creature of man." --Benjamin Disraeli 
     
     C. A. Gus Potter
     Sandia National Laboratories
     Radiation Protection Internal Dosimetry Program (505) 844-2750
     capotte@sandia.gov


______________________________ Reply Separator________________________
Subject: Public In Vivo Iodine-131 & Tritium Urine Levels
Author:  gene.carbaugh@pnl.gov at hubsmtp
Date:    10/20/97 5:53 PM


The Hanford whole body counter cycles some 7,000 to 11,000 whole body 
counts in a year, mostly on Hanford workers.  Our NaI system has a 
nominal MDA of about 3.3 nCi (120 Bq) for I-131 and our germanium system 
MDA hits about 1.5 nCi (55 Bq).  We are not seeing I-131 in workers at 
these levels.  On the rare occasion when we do find it, we almost always 
find that the worker or a family member underwent some kind of 
diagnostic or therapeutic therapy.
     
The most interesting anecdote was last year when a worker was found to 
have moderate contamination on two consecutive days during exit through 
portal monitors.  The poor guy was being called on the carpet for bad 
work practices and the radcon people were getting ready to go survey his 
house, afraid that he had taken stuff home.  We did a whole body count 
on him before they left and found 24 nCi (890 Bq) of I-131.  Since we 
don't really have I-131 anymore, we posed the question of medical 
exposure:  lo and behold, his wife had just had therapeutic dosages and 
he hadn't made the connection.  We moved fast to tell radcon that if 
they decided to go ahead with home surveys to be prepared to find lots 
of non-Hanford I-131 - and start to think about how they were going to 
write that one up.  Fortunately, wise heads prevailed and the home 
survey plans (and appropriate press releases) were quickly halted.  We 
told the field radcon people they owed us a beer - but they never paid 
up.
     
Regarding tritium - we run occasional blank urine samples through our 
excreta bioassay lab as a QA check on their work.  Based on our blanks, 
the lab has an MDA of about 4.4 dpm/ml  (thats 2000 pCi/l, or 33 Bq/l), 
and an Lc of 2.5 dpm/ml  (800 pCi/l, 13 Bq/l).  Actual sample results 
are in the range of about 1 +/- 0.73 (1-sigma) dpm/ml (you do the next 
conversion). I believe these levels would be indicative of the general 
public in Eastern Washington State.
     
A few years back we did some sampling on a group of unexposed workers 
who got their workplace drinking water from an aquifer that had slight 
tritium contamination from old waste management practices.  Their levels 
showed a lognormal distribution with a geometric mean of about 3 dpm/ml.
     
A person who wears a tritium-activated luminous watch may come in one or 
two orders of magnitude higher.
     
Hope this is useful.  Feel free to e-mail or phone me if you need more 
info.
     
Gene Carbaugh, CHP
Internal Dosimetry
Pacific Northwest National Laboratory 
Richland, WA 99352
(509) 376-6632
     
e-mail:  gene.carbaugh@pnl.gov