Re: Missing H-3

[Scott Schwahn <schwahn@jlab.org>]

Mr Jo wrote:

> We boiled about 20 ml of tritiated water... The initial H-3 activity in
> the water is 2400 dpm/ml and the condensated water activity is about 1800
> dpm/ml...

We've seen similar things here.  Our best explanation so far is that (for us)
there was tritiated gas (T2 or HT) dissolved in the water and that the process
of heating drives off the gas, leaving only the tritiated water (HTO or T2O)
behind.  Thus the reduction in apparent specific activity.  One way to verify
this in your case is to vent the original sample (by now, the tritium gas should
have collected in the airspace at the top of your scintillation vial) and
recount it.  You may find that the apparent tritium concentration has decreased
in the original sample vial to the level of your second sample.

Another RADSAFER suggested that "regardless of the isotope involved, 99+% of the
material stays in the concentrate."  This is incorrect for tritiated water.  In
this case, the tritium _is_ water, and if you completely desiccate the water,
you leave next to nothing behind.

Please, Mr. Jo, forward your private responses to me.

Thanks,
Scott
--

Scott O. Schwahn, CHP
Thomas Jefferson National Accelerator Facility
schwahn@jlab.org


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