RE: Lantern mantles

["Jim F. Herrold" <Herrold@UWYO.EDU>]

OK, no one has referred back to the ANSI standard yet, so I'll step in. The
standard says calibration should be performed with national or derived
standards, but it doesn't specify this for the performance check sources.
They should just provide radiation of the same type as the calibration
sources, unless (1) the source instrument geometry is well understood or
reproduced, or (2) the instrument response to this radiation is well
understood and is not critically dependent on instrument adjustment. Using a
gamma source to check beta detection instruments is all right, but obviously
not for instruments that detect neutrons. ANSI is not in the regulations,
but we have adopted it in our license.

We use the 1 microcurie Cs-137 button sources. People did not want them
attached to the instruments, but we have found that it is very hard to keep
track of all those button sources and make sure people use them. Attaching
the source would remind the users to use them periodically and make it
easier to find the sources when we calibrate annually. (You have to write
the check source reading on the instrument) What's a mother to do? Education
is the key, even if you use bits of lantern mantle attached with duct tape.

Hope this helps.

Jim Herrold, Radiation Safety Officer
herrold@uwyo.edu

University of Wyoming
Environmental Health & Safety
303 Merica Hall
Laramie, WY 82071-3413

(307) 766-3277


> ----------
> From: 	David Krueger[SMTP:dkrueger@icnpharm.com]
> Sent: 	Monday, September 21, 1998 11:23 AM
> To: 	Multiple recipients of list
> Subject: 	Re: Lantern mantles
> 
> Mike Dupray wrote:
> I beleive you are all making a mistake. Use of lantern mantles is only
> good
> for demo's and shows. You cannot properly performance test an instrument
> with an uncalibrated source. You need to prove that the calibration of the
> instrument is still good. The only way to do it right is to use a
> traceable
> standard(s) and test each scale to mid scale. Anything else tells you
> nothing except that the needle moves when exposed to radiation.
> 
> 
> My response is that a check source only need to be long lived so that its
> radioactivity is not going to change over the period that it will be used.
> If an instrument is properly calibrated with traceable sources and its
> response to any check source (traceable or not) is documented, then
> continuing to use that source to verify that the instrument responds in
> the
> same way (gives the same reading consistantly) would appear to be all that
> is necessary. Otherwise, Mike's suggestion basically ends up calibrating
> the instrument every time it is used.
> 
> Dave Krueger, CHP
> dkrueger@icnpharm.com
> 
> 
> ************************************************************************
> The RADSAFE Frequently Asked Questions list, archives and subscription
> information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
> 
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html