Spurrious TLD results

["Tony LaMastra" <alamastra@enter.net>]

Hi all:

A couple of postings have been made concerning this topic.   Back in the
1970's and early 1980's when I was an employee of Bethlehem Steel, we had
our own TLD program and read about 1000 dosimeters a month.   It was
occasionally noted that a dosimeter would show a dose (anywhere from 10 -15
to a few hundred millirem) when it was known that the dosimeter was never
issued or exposed to our radiation sources.   Since we had an active
industrial radiography program where doses ranged from 50 to 200 millirem
per month, one thought was accidental incomplete annealing, or dosimeters
used for calibration.   Since we used loose TLD, this was always a concern.
  However, even after segregating all TLD, we would still get an occasional
"odd ball" that could not be explained.   This has happened even with a
commercial supplier.   I have concluded that it is probably due to
non-ionizing radiation stimulated electrons being elevated in energy and
caught in the energy traps, or the release of electron energy upon heating
of the crystal.   We even tried handling the TLD in subdued light, but it
didn't solve the problem.   The rate of occurrence was around  1 in 1000.  
 My technician attributed it to the "queertrons" running around in the TLD
crystal.   Their those things that cause electronic products to not work,
until you take the device to the repair shop, at which point it works
perfectly.


Tony LaMastra
alamastra@enter.net
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