RE: TLDs as Anti-Theft Devices?

[John_Sukosky@DOM.COM]

Neill,



Thanks for the post.  In theory, if the problems you indicate are

significant, the effects would be more prominent for low dose TLD results

(i.e. < 100 mrem).  At higher doses, the control/background effect on

reported TLD dose is masked.  We've only been through one full quarter of

Take-Home TLDs (non-outage quarter predominated by low dose results) and we

just haven't seen a significant difference compared to when we required

storing of TLDs on site.  We compare accumulated Electronic Dosimeter (EPD)

results to TLD reads using the statistical analysis developed by Mike Lantz

(Palo Verde). This is a more accurate method to flag anomalous results

especially for low doses.



I agree that there may some uncertainties that are not accounted for in the

background study variability but the data thus far indicates that these

uncertainties are not significant.  In the background study we placed TLDs

covering all distinct zip codes for the entire worker population.  So

although we may not have had a set of TLDs in a shopping center, I don't

think that the background while shopping would be significantly different

than in a workers home.  It's likely that both would be in the same general

area with similar backgrounds.



Yes, the tangible problems (non-returns, etc.) you mention do exist

especially when you first start the take-home TLD practice.  But others

that have used this practice for years indicate that these problems are not

an issue after a few quarters of familiarity.



John M. Sukosky, CHP

Dominion

Surry Power Station

(757)-365-2594 (Tieline: 8-798-2594)







                                                                                                                                       

                      "Stanford Dosimetry"                                                                                             

                      <stanford@stanforddos        To:       <John_Sukosky@DOM.COM>                                                    

                      imetry.com>                  cc:       <radsafe@list.vanderbilt.edu>                                             

                                                   Subject:  RE: TLDs as Anti-Theft Devices?                                           

                      11/04/2004 08:10 PM                                                                                              

                      Please respond to                                                                                                

                      stanford                                                                                                         

                                                                                                                                       

                                                                                                                                       











The technical problem with taking them home is of course that you are

losing

the relationship between the control/background measurement, from badges on

a rack or in the lab, and the response on the worker's badge from

non-occupational exposure. Performing a background study with badges going

off-site shows the increased variability as was mentioned. But there is no

guaranteeing that a given worker's badge will be treated even as

consistently as the badges in the study. Chances are the dosimeters in the

background study weren't taken shopping for example. As all NVLAP

accredited

programs must quantify the uncertainty in the system, it would be critical

that the increased variability in the "take 'em home" policy was included.



The more tangible problems are in the dosimetry lab. Non-returns, workers

leaving badges home, then bringing them in. Maybe swapping them out on

their

dresser, or in their jackets. It takes a big effort to stop the practice,

which used to be pretty universal, but sites I have worked with that have

stopped it are much happier now, and the workers do come to accept it.



Neill Stanford, CHP

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Stanford Dosimetry LLC

www.stanforddosimetry.com

stanford@stanforddosimetry.com

360 293 9334 (voice/fax)

360 770 7778 (cell)

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