Re: Spurrious TLD results

["Sandy Perle" <sandyfl@earthlink.net>]

My response was eliminated since one line started with the word 
"from". I didn't know that the term from would eliminate the text, 
unless it was in the first line...  Sorry about that!

Tony LaMastra said:

> 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.

As observed from Tony's comments, it is obvious that when loose 
chips are used for dosimetry, the chain-of-custody is not possible, 
whereby an individual chip correction factor can be applied, unless 
each chip is marked in some way. Unless the entire batch of chips 
re-evaluated, and those that exceed a specific criteria value, there 
will be variability within the results. Of course this would not explain 
unexpected doses of 50 mrem.

I do not agree that these unexplained doses can be attributed to 
non-ionizing radiation. In all of my years, dating back to 1971, I 
have never seen a LiF, LiBO, CaF or CaSO TL element respond in 
any fashion, to non-ionizing radiation.

Since Tony was talking about the early '70s, I assume there were 
no glow curves collected. If they were, evaluation of the glow curve 
could provide a lot of information regarding the readout and heating 
characteristics of the dosimeter. It could very well be some oil, 
powder or other foreign object was on the chip, on the hot finger, 
etc. Without a glow curve, there is little that can be done in an 
analysis. The reader itself could have had a voltage spike, since 
the TL readout is highly dependent on clean voltage.

We have come a long way since 1971. Variability does still occur.. 
However, with the knowledge gained over the last 30 odd years, 
better assessments can be made. 

I concur with all postings that state that the facility where the 
badges were worn, they should take an active role in monitoring 
their dosimetry results, regardless of who did the processing. Only 
the facility knows how they expected the individual to wear the 
badge, and in what environment and under what conditions it was 
exposed. All the processor can do is to state categorically, that 
the dose reported is an accurate assessment as to WHAT was on 
the dosimeter. The processor can not say say whether or not it 
was actually worn while it was exposed, or how it was exposed.

------------------
Sandy Perle
Technical Director
ICN Dosimetry Division
ICN Plaza
3300 Hyland Avenue
Costa Mesa, CA 92626
Office: (800) 548-5100 x2306 
Fax:    (714) 668-3149
  
sandyfl@earthlink.net
sperle@icnpharm.com

ICN Dosimetry Website:
http://www.dosimetry.com

Personal Website:
http://www.geocities.com/CapeCanaveral/1205

"The object of opening the mind, as of opening 
the mouth, is to close it again on something solid"
              - G. K. Chesterton -

The opinions expressed are solely, absolutely, positively, definitely those of the author, and NOT my employer
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