Re: TLDs - False Positive Betas

["JERRY ROSEN" <ROSEN@rso.radsafe.pitt.edu>]

> Date:          Wed, 19 Jul 95 13:55:10 -0500
> Reply-to:      radsafe@romulus.ehs.uiuc.edu
> From:          Stuart Torf <torfsm@NU.COM>
> To:            Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
> Subject:       TLDs - False Positive Betas

We use a commercial service for TLD dosimetry.  Originally they used 
a two TLD systemand we had recurrent problems with false beta 
readings in clinical x ray areas.  The presumption was that low 
energy x ray scatter fields were the problem.  The individuals had no 
known contact with nuclear sources.

When the vendor switched to a 3 chip system much but not all of the problem 
disappeared.  We now code those individuals that are known to only 
work with x ray sources, so that a specific algorithm is used that 
reports only x ray exposures.  This has eliminated the problem and 
yields more accurate dosimetry.  There can be a significant shift in 
the reported dose when moving from the beta to x ray algorithms.

____________  reply separator_________________________

> 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.
> 
> 
> 
>