tritium decon

["Les Slaback, Health Physics" <SLABACK@micf.nist.gov>]

In reponse to Mike Grissom's horn blowing I have to plead excess exhalation
on his part.  My negative experience with tritium decon consists of an
effort (as a test) to decon the steel shell of a vac-ion pump off a
neutron generator.  The pump had contained in excess of 50 Ci of tritium and
released mCi amounts when brought to atmospheric pressure.  As I recall my
estimate of the 'apparent' burden (by turning the shell into an ion chamber)
was half a curie.  Acid washes, repeated heating, ultrasonic washing all remove
d activity but did not appear to reduce the 'apparent' activity.  From folks
who study hydrogen 'solubility' in metals this is not unexpected.

I have had similar negative results with aluminum tritium contamination, but
have not done such extensive brute force efforts.  I did find that tritium
leaves tungsten very readily via heating.


Take care not to do a contamination test immediately after surface decon
procedures.  More tritium will bleed to the surface.
My conclusion is that the economical route is simply disposal, or controlled
usage if the item will remain in use.

Our local materials expert indicated the maximum hydrogen to iron atom ratio
would be 1:1e6.  If anyone knows of a definitive reference for this I
would appreciate the source.

If you have airborne tritium, e.g., like at heavy water reactors, concrete
walls can be a reservoir that retains it.

If you have asbestos around, be aware it is hydroscopic and hence will suck
up airborne tritium.[mixed waste?]

I suspect the canadians must have a pile of info on this topic given there
operating experience with the heavy water CANDU facilities.  Perhaps we can
get input from someone up north before golf season starts (couldn't resist
mentioning that topic that bothers some folks).

SLABACK@MICF.NIST.GOV  [NBSR Health Physics Group]
    ...a little risk, like a bit of spice, adds flavor to life