Re: A hunting we will go!

["Richard L. Anderson" <anderson.800@osu.edu>]

David,

I agree with what Joel has said below.  However, I prefer to use a larger
probe.  I would recommend using a 2x2 or even possibly a 3x3 NaI ( Ludlum
44-10 or 44-20 ) if available.  If you do not know at what depth the Th-232
is at, you may be dealing with some very low count rates; use all the
sensitivity you can get.  One other suggestion would be to use an
instrument similar to a Ludlum-2221.  After finding the suspect area, you
can then easily set up a window on the instrument to look for the .900 -
1.000 MeV range and confirm your suspicion.  I have used a similar method
to confirm Ra-226 by looking for the Bi-214 gamma.

Rich



At 02:50 PM 4/30/98 -0500, you wrote:
>	David,
>
>	Having done similar "hunts" in the past - the first thing you need to do
(in my humble opinion) is find the stuff!  Get a high energy scintillation
probe (like a Ludlum 44-2), grid your area and start walking back and forth
"till you find it.  A high energy probe because the low energy photons
won't reach your probe if they originate at any depth and you have enough
mid-high energy photons being generated with Th-232 and its progeny. I
often let the probe sort of "dangle" (a scientific term if I ever heard
one) near the ground and slowly swing it back and forth as I slowly walk my
grid.  In a grid area (if I have a companion) I will call out the CPM
readings so as not to forget where my highest readings are/were.
>
>	Regarding the pyrophoric part - time for the asbestos under-ware (grin).
>
>	Good Luck,
>
>	Joel
>
>..
>
>At 12:24 PM 4/30/98 -0500, you wrote:
>>     Folks,
>>     
>>     For the sake of an excavation/remediation project, we are assuming 
>>     that there are 360 pounds of Th-232 buried in a waste pit full of 
>>     other contaminants.  We don't know exactly where in the pit this 
>>     material is or quite how deep.  What we do know is that it may be 
>>     pyrophoric and, we suspect, it is concentrated in one location.
>>     
>>     We would like to find this material before it finds us.  We're 
>>     thinking of using gamma spectroscopy to search for the Ac-228 .991 MeV 
>>     gammas.
>>     
>>     Any advice?  Thanks in advance!
>>     
>>     David Levy
>>     Health Physicist
>>     david.levy@fernald.gov
>>     (513) 648-3816
>>
>>
>>
>
>Joel T. Baumbaugh, MPH, MHP
>baumbaug@nosc.mil
>Radiation Safety Officer
>SSC San Diego, CA
>



Richard L. Anderson
Health Physicist
The Ohio State University
1314 Kinnear Road, Room 101
Columbus, OH  43212-1168
ph (614)292-1284
fax (614)292-7002
anderson.800@osu.edu

"You bet your Lutefisk I'm Norwegian!"