Re: H-3 in desiccant (Drierite)?

["Don_Jordan" <Don_Jordan@fpm.uchicago.edu>]

Most modern Liquid Scint. counters have a Quench Indicating Parameter (e.g.,
H number for Beckman
counters) which will provide a reasonable good estimate of the counting
efficiency for the vacuum
pump oil.  The QIP for your instrument will be explained in the manual which
cam with it.  To use the QIP sensibly you will have to have a "quench curve"
available for your machine.  This means counting a 
set of standards with the same activity but varying amounts of a quenching
agent added.  Newer instruments
will have quench curves stored in memory, and can automatically correct for
quench.  Again, check your manual.

The Drierite poses a different problem.  The short answer to your question
"Can you count drierite suspended
in cocktail." the answer is definitely no for quantitative work.  Scint.
counting only provides quantitative 
results for homogeneous samples.  For P-32, the two phase system (suspended
solids and LSC) might not 
affect efficiency greatly, but for H-3 most of the activity could be in the
solid phase and the weak 
H-3 betas cannot reach the cocktail.  

However, MgSO4 is pretty soluble in water, and will not, I believe produce a
colored solution.  So, to 
quantitatively measure the activity in the MgSO4, I would dissolve a
measured quantity in a measured 
volume of water and count a sample of that.  

As for their disposal plans, stop them before they do something silly.
Liquid scintillation samples 
containing less than 0.05 uCi of H-3 or C-14 per gram of material can be
disposed of without regard 
for the radioactivity.  (since I'm in an Agreement State, I've forgotten the
10 CFR citation) So all your LSC samples can be disposed as flammable waste
(if you are using a cheap, nasty xylene based cocktail) or as 
non-hazardous waste if you are using the newer biodegradable cocktails.  Do
not waste the gallon of xylene. 

Disposing of the contaminated oil will pose more of a problem.  I suggest
you call SEG (Scientific Ecology Group) in Oak Ridge Tenn. for advice.  A
solution of the drierite can probably be poured down the drain, 
depending on the activity & sewer release regs in your area.  

Hope this helps,   Don


Don Jordan	
The University of Chicago	
Office of Radiation Safety
Zoology Building Room 11
1101 East 57th Street
Chicago,  Illinois  60615
Tel.	773-702-6299
Fax	773-702-4008
email Don_Jordan@fpm.uchicago.edu