Fwd: Tritium Contamination

["Thatcher, Drew" <dht0303@hub.doh.wa.gov>]

                 ***** Original Message Follows *****

Does anyone know of a way to analyze chips of concrete suspected of
containing tritium contamination? We would like the ability to determine 
the
total activity contained within a sample. Assessing a sample for 
potential
activity seems fairly straight forward - one could grind up a sample and
count it by liquid scintillation. The trick is trying to determine the 
activity
contained within the particles. Is there a way of chemically dissolving 
the
concrete while retaining the tritium in solution?

Thanks,

Keith McCartney
EG&G Mound
(937) 865-4068
MCCAKA@DOE-MD.GOV

Keith - this is a response from Bud Taylor at the WA State Radiation 
Laboratory - his address is located below.  	Regards/Drew Thatcher
--------------
Tricky; if you acid digest the powdered concrete you lose water vapor and 
thus tritium.  I think I'd try a pressurized acid digestion.

First, prepare a standard using portland cement.  Mix a 5 gram portion of 
cement with DIW and spike with a known amount of tritium.  Mix the cement 
in a mold with at least one very thin dimension (long wide slab) so that 
it will cure quickly and break easily.  Cure the cement using just enough 
DIW to keep it moist but not enough for runoff to occur.  Once cured 
weigh the standard H3-cement, then proceed as follows for both the 
standard and an aliquot of sample.

1.  Break up an pulverize the cement.  
2.  Weigh an aliquot of the cement using an analytical balance.
3.  Place the powdered cement aliquot in a teflon lined pressure vessel.
4.  Add DIW & sulfuric acid.
5.  Seal the vessel and allow dissolution to occur for a day.
6.  Add concentrated HF to dissolve silicates.
7.  Re-seal and continue dissolution.
8.  Perform distillation procedure for collection of tritium as with 
other liquid matrices.
9.  Count the distillate by LS using a standard procedure.

This is off the top of my head.  The dissolution will of course require 
some more sophistication but this would be a decent first try.  Depending 
on the composition and age of the concrete dilute HF might also be 
needed.  A microwave digestion bomb would be a suitable pressure vessel.  
If the dissolution proved to be tricky microwave digestion in a sealed 
bomb under careful control might help (the tritium would volatilize but 
would be recovered on cooling).

Those folks at EG&G Mound are quite good, I'm sure they'll be posting a 
workable solution in the near future.  You might also ask Josephine 
Pompey for some ideas, she's fine tuned microwave digestions for a number 
of complex matrices.

Cheers,

Bud Taylor, Radiochemist

Washington State Department of Health
Public Health Laboratories
Office of Environmental & Radiation Chemistry

1610 N.E. 150th Street, Mailstop K17-9
Seattle, WA 98155
_____________________________________
     Tel : (206) 361-2896
     Fax : (206) 361-2899
Internet : bct0303@hub.doh.wa.gov
     WWW : http://www.doh.wa.gov/phl/envchem/radchem.html
_____________________________________