[ RadSafe ] Tritium contamination

Olsson Mattias :MSO mso at forsmark.vattenfall.se
Mon Oct 31 10:03:57 CDT 2011

Dear Radsafers,

I am playing around with a nuclide vector that I hope to be able to
apply for free release measurements. The assumption is that the
contamination comes from BWR reactor water, and at least Co-60 is
measurable with a gamma detector. I want to use Co-60 as a key nuclide
to estimate the amount of a whole array of other nuclides by using the
known composition of the activity in reactor water.

To set this up is not very difficult, and I also add a function to let
the nuclide vector "age" for the cases where it is known that the
contamination occured some time ago.

The thing is that the free release measurements will be done on dry
materials. That means that the tritium, which is fairly abundant in the
reactor water, will no longer be there during the measurement. I suppose
*some* tritium will be retained on the materials, though. Surfaces are
somewhat prone to exchange protons in an aqueous environment, if nothing
else. Anyway... What I wonder is if there is any experience on here on
how much tritium will stay as contamination on a surface if the surface
is first splashed with tritiated water and then allowed to dry. I
imagine this would depend on a number of factors (type of surface, ratio
between available surface and the amount of tritiated water etc) that
would make a general statement hopeless, but if there are any practical
examples I would love to hear about them! It could lead me towards a
conservative reasonable assumption.

All the best,

Mattias Olsson, Sweden

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