Re: Film badge/TLD results

[Sandy_Perle_at_USFPL201@email.fpl.com]

     All points made are very valid. My response was geared towards 
     determining if the processor is even viable for producing reliable 
     results. It is also imperative that the lab do blind testing to ensure 
     that the algorithm being used for "your specific lab" is adequate, 
     since the processing lab CAN and DOES use different algorithms for 
     customers compared to NVLAP testing, in some instances. I know .. 
     since I am a NVLAP assessor. Strange things do occur with processing 
     labs!! It is imperative to test your dosimetry to the appropriate 
     standards.
     
     Sandy Perle
     Supervisor Health Physics

                ___________________________ Reply Separator 
_________________________________
Subject: Film badge/TLD results
Author:  radsafe@romulus.ehs.uiuc.edu at Internet-Mail
Date:    6/27/95 5:00 PM


Yesterday, Sandy Perle wrote:


    > Anyone who is concerned with the accuracy and precision of the 
    > dosimetry processor they use, or are considering using, need only to 
    > ask them for their NVLAP Proficiency test results ANSI N13.11 (1983 or 
    > 1993 version). In addition I recommend that you ask them for the 
    > on-site assessment report that is left with the lab.  
     
    > These two items will provide enough information regarding the 
    > processor to make a valid assessment of their overall program.
     

While true in principle, one should apply a reasonable dose of salt to the
proposal "if they did well on NVLAP (or DOELAP) then your processor will give
you good results".   I'm not taking issue with the validity of the NVLAP
process or with the idea of checking your processor's results, it should just
be kept in mind that a periodic controlled test does not guarantee "good"
dosimetry results.  

A couple of things that come to  mind in this vein: 


 A processor may pass NVLAP but fail DOELAP (or vice versa)...
 Or they may not be able to pass in a certain category...
 There is nothing forcing you to qualify in a given category, even
  though you may have exposure in that category...
 A processor may even use a special algorithm for reading TLDs for the
  NVLAP test that's not routinely used for personnel badges...

Other problems may creep in, such as a systematic error that is introduced by a
calibration foul-up that doesn't get corrected until months after introduction.
Or their QA may simply not be good enough to give consistent results in the
"real world".

I have heard of a number of horror stories regarding dosimetry snafu's and seen
some interesting results from limited blind spikes I have performed myself.