[ RadSafe ] Tritium contamination

[Scott Davidson]

You seem to be on the right track.  Unless the material is porous or
has a particular affinity for tritium, then when it is dry, the
tritium will be gone.

Porous is on atomic/molecular level where tritium can permeate the
material.  This would be evident if wipes came up contaminated after
decontamination (weeping).  This was the classic "re-appearium" that
occurred on casks that were used in spent fuel pools and can occur
from many radionuclides.  The NRC has some old guidance on cask
weeping.

Materials with an affinity for tritium include some metals that form
hydrides and things with hydrogen in them.  Some metal hydrides will
be stable and not release their hydrogen (tritium) readily.  But if
the tritium concentration is high, some exchange will occur and be
well fixed.  Likewise for plastics or other polymers that might
exchgange a hydrogen for tritium.

There is a lot of information in chapter 5 of DOE Handbook 1129 a
portion a different section is shown as "19-26" but I am not sure how
much you want to make this a science project.

On Mon, Oct 31, 2011 at 11:03 AM, Olsson Mattias :MSO
<mso at forsmark.vattenfall.se> wrote:
> 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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