Re: Spurrious TLD results

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

Sandy:

We did collect glow curves.    Since we stopped doing our own dosimetry,
these were filed.   I'll try to locate them.   If I do, I will be back in
touch to see what I might look for on the glow curve.    You're correct in
that there was no way to track chain of custody.   Just before we stopped
analyzing our own, we had gotten identified cards and were about to start
using those in the program.    It would have been easier to track
individual dosimeters to see if a particular card was causing a problem.

Thanks,

Tony LaMastra
alamastra@enter.net



----------
> From: Sandy Perle <sandyfl@earthlink.net>
> To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
> Subject: Re: Spurrious TLD results
> Date: Friday, September 11, 1998 5:30 PM
> 
> 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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