[ RadSafe ] Looking for References on Liquid Scintillation Counting for Tritium

[Felipe Gaitan]

Gentlemen,

Thank you Alex, Franz and Bob for your response.  I'm writing to the 
list in case other people are interested but we could communicate off 
line if you prefer.

So far the consensus is that there are no definite references due to 
the fast pace of development and that the two main categories are 
high and low count rates.  So it looks like I need to give more 
details about our particular application.

We are trying to replicate an experiment done at Oak Ridge (and more 
recently at Purdue) in which the authors claim to be producing 
Tritium in deuterated acetone using acoustic cavitation.

Here is a summary of what I consider are the relevant parameters (let 
me know if you think I'm missing any):

1.  Sample liquid:  both regular and deuterated acetone.  According 
to the authors, the tritium backgrounds for regular and deuterated 
acetone are about 20 CPM and 50 CPM respectively. Deuterated acetone 
has a higher background due to tritium contamination (I assume during 
the deuteration process).  As far as I know, they have used regular 
(not super-low background) LS counters (Beckman LS6500, I believe)

2.  They measure anywhere between 2-15 CPM above background for the 
deuterated acetone (none for the other control samples including 
regular acetone)

3.  I'm aware that chemiluminescence (CL) and other types of 
luminescence can interfere with tritium measurements and I don't know 
if or how the authors compensated for it. I wouldn't be surprised if 
acoustic irradiation could excite some molecules and cause them to 
emit photons. I don't think the regular machines can compensate for 
CL when the count rate is that low (right?).  The only way I know is 
to monitor the count rate (both coincident and non-coincident) as a 
function of time.

Here are my questions:

1.  Do you know anybody measuring low levels of tritium is acetone 
samples? I'm wondering if there are particular issues with acetone.

2.  Are there techniques for eliminating CL interference at low count 
rates (a few CPM above background)?

3.  What other effects can interfere with this kind of measurements?

Thanks in advance,

Felipe

-- 
D. Felipe Gaitan, Ph.D.
Chief Scientific Officer
Impulse Devices, Inc.
13366 Grass Valley Av.  Unit H
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email: gaitan at impulsedevices.com