Re: TLDs - False Positive Betas

[Sandy_Perle_at_USFPL201@email.fpl.com]

     Stu:
     
     NU uses the thin chip for beta assessment. I have seen these chips 
     crumble and chip after a short time of wear when out in the field. 
     While one would expect that even the cracked chips will release the 
     same total amount of light for the Harshaw 8000 reader to detect and 
     convert to response, I suggest that the problem you have is the ECF is 
     no longer valid.
     
     My question to you would be how often do you perform ECF 
     verifications? My lab routinely verifies 1000 TLDs monthly, which 
     includes a subset of the QC TLDs used during the period under review. 
     This verifies that the lab badges and field badges are statistically 
     equivalent.
     
     Mentioned earlier was whether or not you are trending the data on 
     Control Charts. We do, using Shewart Control Charts. IF you are able 
     to anneal the TLDs below your admin. limits, it would still be prudent 
     to plot the data, paying close attention to the standard deviation as 
     well.
     
     My guess is that the problem IS NOT low energy x-rays, since you 
     should have enough data to dispel that, from chemistry samples, and, 
     gamma spec analysis around your plant. I also assume that you would be 
     aware of changes that would affect the energy spectra around your 
     site, and if you don't, that is a more serious issue that needs to be 
     resolved.
     
     If you would like to discuss further, please contact me at (407) 
     694-4219.
     
     Sandy Perle
     Supervisor Health Physics
     Florida Power and Light Company


______________________________ Reply Separator _________________________________
Subject: TLDs - False Positive Betas
Author:  radsafe@romulus.ehs.uiuc.edu at Internet-Mail
Date:    7/19/95 1:54 PM


Has anyone experienced "false positive" beta responses with 
their TLDs? We  have performed glow curve analyses on these 
responses which say that there is a real beta response but 
our TLD users say that there is no beta. Any comments?  

Thanx

Stu Torf
torfsm@nu.com
RP section
Northeast Utilities
203-665-5814

P.S - whatever the standard disclaimers are, they apply.