Calibration Sources Wanted

[fbronson@canberra.com]

Hello RadSafers

We have developed a new instrument for field quantitative gamma spectroscopy.  
It is called ISOCS, for InSitu Object Counting System.  It is fundamentally a 
portable shielded/collimated Ge gamma spectroscopy system.  But one of it's new 
features is a Mathematical Efficiency Calibration Software.  This allows the 
user to develop energy-efficiency curves for a wide range of sample sizes, 
locations, and energies, without radioactive sources.  The software is designed 
to work for very small samples and very very large ones [e.g. large ISO 
containers, B-25 boxes, 55 gallon drums, 10000 gallon tanks, pipes, 
well-logging, ... ];  basically any defined object from 50 keV to 7000 keV, and 
any location within a 100 meter diameter sphere around the detector.  

With claims like that, our customers are asking for proof that it really 
works.  That is the purpose of this query.  Do any of you know the existence of 
large well characterized and documented multiple energy gamma calibration 
sources?  Desired are B-25 boxes, ISO containers, pipe sources, large flat 
surfaces, large and thick sources simulating soil contamination, calibrated 
well-logging holes, large tanks filled with calibration sources, etc.    The 
ones we have found so far at some well-respected government facilities don't 
have much of pedigree; while they are probably OK, they aren't very useful as 
reference sources.  

We have already gathered about 60 such comparisons from sources used here to 
characterize and calibrate our waste assay products, and from some concrete 
calibration pads in Germany, and from many MCNP computations.  But we can use 
more.  In general, we find the software agrees quite well with the MCNP 
computations and with "normal-sized" radioactive sources, but for large 
radioactive sources sometimes not as well.  After analysis, most of these 
"problems" have been due to the calibration source not being quite as well 
known as originally thought.  Making good quality large sized radioactive 
sources is not an easy tasks.  We think that the calibration software is 
probably more accurate.  

So, if any of you have sources, or contacts that might know of good quality 
large sized multi-energy gamma calibration sources that we can visit with our 
instrument, and borrow a few photons that are otherwise going to waste, please 
let me know. 

Also, if anyone wants information about the ISOCS instrument, or the 
mathematical calibration software, send me a reply.

thanks for reading this far.  

Frazier Bronson CHP
Canberra
Meriden CT USA