Re: Asking for opinions -Reply

[Neon John <johngd@bellsouth.net>]

Robert Denne wrote:

> The plant I worked used electronic dosimetry which was within an amazing
> 2-5% of the TLD reading.  Any good dosimetry program should question
> discrepancies outside this range and medical administrations or contact with
> medical admins would be a great question to ask.
> 
> We should also warn them not to store their TLD's next to their smoke
> detectors.  Just kidding.  Please, no response on that comment.

About 10 years ago I had a case referred to me by the local
emergency management agency.  A local chiropractor (no snickers) had
just started a personal dosimetry program and for the first three
months had a consistent 80-90 mREM reported from Landauer.  She was
afraid that something was wrong with her X-ray machine (A valid fear
since it looked like it might have ballasted the Mayflower!) A quick
look at the report showed high energy radiation not possible from
her machine.  I surveyed her X-ray machine anyway, to find no
problem.  I then did a careful survey of her very old concrete block
building that had always had some sort of medical practice in it.  I
was expecting to find an old radium seed or something similar
squirreled away in the walls.  Nothing.  The initial Q&A established
that she left her TLD at the office at night.  At that point, it was
time to walk through everything she did during the day.  Everything
looked ordinary until she prepared to leave.  She hung her smock
with her TLD attached at the collar on a peg that sat less than 6"
below an AC intake duct.  The duct had air filters attached to the
face.  A contact measurement sent my RM-14/pancake probe off-scale
on the 2 lower ranges.  A quick spectroscopy look at a sample of the
filter showed radon daughters.  Her TLD was being dosed by the
buildup on that filter.  I suggested she move her coat hook and
change the filters occasionally and if that sort of thing bothered
her, to get a radon survey done.  The next month the reported dose
was background.

Of course, that low a dose is not reportable BUT.  If a facility is
counting man-REM a low dose like that across a large population of
workers racks up the man-REMs rapidly.  I've asked HPs at sites I've
worked where they allowed workers to carry dosimetry home about this
but never got an answer any deeper than "it's policy".  Certainly
made me not put any faith in collective dose reporting.

John
-- 
John De Armond
johngdSPAMNOT@bellsouth.net
RDS Inc.
Cleveland, TN
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