Enriched tritium analysis

[Gary Schroeder <schroede@mail.sep.bnl.gov>]

Cheryl Baker said:

>I was recently asked by my supervisor to explore the possibility of doing
>enriched tritium analysis.  I confess total ignorance and am hoping to get
some
>information through RADSAFE.  First of all, why would anyone need to see such
>low levels of tritium, what information is gained?  Is there a reference
for the
>technique?  What equipment would be needed and what might the startup
costs be? 
>We do standard tritium analysis and have a Packard LS counter. Is anything
more
>elaborate needed?  

Cheryl, I think you've already provided some of the questions that your
supervisor needs to answer.  A modern liquid scintillation counter should
provide detection limits for tritium in water of about 200 - 400 pCi/L.
Most labs don't bother looking for levels any lower than that because there
usually isn't a need.  Your supervisor should be able to give you a reason
for requesting possible enrichement analyses.  The only reason I can think
of is if you're interested  in establishing what background levels are in
the environment.  What kind of program are you running the analysis for?
Environmental?  Contamination control?

Here at BNL, using a 7 mL sample and a 50 minute count in an LSC we can
achieve an MDL of about 380 pCi/L.  Since we're interested in demonstrating
compliance with the drinking water standard of 20,000 pCi/L, this
sensetivity is quite adequate.

If enrichement is the way you want to go, the primary methods I'm aware of
is electrolytic enrichment, i.e. passing electric current through a sample
to preferentially drive off stable hydrogen.  Literature suggests
enrichement factors for tritium of up to 35:1 by this method.  I don't have
a complete reference method, though.

=======================
Gary L. Schroeder
Brookhaven National Laboratory
Environmental Protection Office
gs1@bnl.gov