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Re: RADSAFE digest 3385 (extremity dose)

Glen Vickers wrote:

"How would a finger tip badge work?  Wouldn't you lose the sense of touch,
drop your container, and then require skin dose calcs?"

The Vinten fingertip dosimeter was (is?) basically a glove
finger with a thin layer of powdered TLD material (LiF?)
at the end, under a thin layer of plastic (0.07 mm I 
think).  It was not much more obtrusive than wearing 
an extra glove layer on the finger in question.

It was able to measure not only fingertip dose but beta dose 
with decent accuracy since the plastic overlay and the 
dosimeter layer were both so thin.  The commercially
available rings that I've seen have relatively thick 
plastic/paper overlay (~25-75 mg/cm^2) and thick TLD chips,
both of which contribute to under-estimation of shallow
dose from betas unless you can characterize the radiation
field reliably enough to apply some specific calibration
factor (such as for Sr/Y-90, Tl-204 etc).  

Also, thanks to Roger Moroney for sharing his experiences.
As we prepared to review our operations for problems with
under-measured extremity dose, we came up with a list of
risk factors to help prioritize what areas to look at:

groups with higher ring badge readings
manual operations (vs automation)
physically small sources
repetitive operations
elevated activity levels
high energy beta emitters, even at sub mCi levels
high activity concentrations
contamination control problems
individuals with higher ring readings than co-workers
groups under time pressure to complete work

Although we haven't seen any major problems, there have
been a disappointing number of poor practices observed.  
Almost all of these poor practices could be quickly fixed.
We will be reviewing this topic at our annual refresher
training next month.  As Roger said, unless you're only
handling tritium, don't assume you don't have any issues.


Regards,

John R. Laferriere, CHP
DuPont Pharmaceuticals Co.
Medical Imaging Division
john.r.laferriere@dupontpharma.com
(978) 671-8316   fax (978) 671-8149
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