Re: Re[2]: Low energy x-ray (8 kev) survey meter

[Joel Baumbaugh <baumbaug@nosc.mil>]

	Well, I think that, perhaps, we have beaten this subject into the ground...I'll answer your specific questions and then let this one go...


>Have you often found leaks with your scintillator that were missed with the GM?  

	About 50% of the time (outside of the enclosure) Inside a G.M. is usually sufficient for "big" leaks.

>How signficant were they? 

	From an "exposure rate" viewpoint "outside" of the enclosure they were NOT significant.  Although 	"Posted" TLDs have upon occasion shown some exposure at CRT stations or other traffic areas.

>Were they at all significant at a distance of a few feet (where an enclosure would be)?

	Again, no.......  Except (yes there's always an "except") when you are dealing with the matter of "prudence".  

	If I have a hand-held scintillation probe in my hand and I am standing in an area where researchers will be standing/sitting (sometimes for hours at a time) and my meter is reading 10 - 50,000 CPM (or more) at 10% efficiency - we're talking about a H___ of a lot of photons "PER SQUARE INCH" passing through one's body.  If you look at a simple chart showing Energy Absorption per coulomb per kilogram like in Cember 2nd Ed, pg 144 you can see that the absorption of x-rays in bone (a LOT of stem cells in bone) at these lower energies is pretty high.  I personally have a lot of respect for low keV x/gamma ray photons for just this very reason.

	What I may not have made clear before is that I work for a facility that does research in a LOT of different fields.  Often, this requires that the machine not be operated in its original configuration due to the size or composition of the materials being examined.  This requires that I examine Rube-Golberg type experimental apparatus prior to the machine being turned on and at various times during operation being as many of the factory safeguards have been altered or completely removed!  Over the years, this has made me VERY gun-shy.  Often, researchers just want to get results - the fact that they may be exposing themselves and others to a "little bit" of x-ray exposure is of little or no concern to them - its a "publish-or-perish world out there in academia.
	
	Enough said.  I think that (in most cases) with a little thought, that a careful survey with a pancake G.M. will yield sufficient results to protect the researchers.  I just "personally" think that in "my opinion" - I get a little clearer picture of where my researchers are able to sit/stand/work with little or no exposure from their machine.

	BTW - thank you all for agreeing to disagree so nicely.


	Maybe a nickels worth today...(grin)


	Joel Baumbaugh
	baumbaug@nosc.mil

Joel T. Baumbaugh, MPH, MHP
baumbaug@nosc.mil
Radiation Safety Officer
SSC San Diego, CA


	NOTE:	The contents of this message have not been reviewed, nor approved by the Federal Government, the U.S. Navy, my bosses or my wife... My wife keeps complaining I never listen to her...or something like that.



	If we are what we eat; I guess I'm cheap, fast, and easy.