[ RadSafe ] Tritium contamination
franz.schoenhofer at chello.at
franz.schoenhofer at chello.at
Tue Nov 1 15:50:11 CDT 2011
Jerry et al.,
Probably the concern is, what maximum permisible contaminant levels are prescribed by authorities - whether they make sense or not, they have to be fulfilled. Your comment, Jerry, is fully justified, but does not help when it comes to legislation.
I am somewhat surprised that Martin (hej!) asks RADSAFE for advice since he is dealing with a Swedish problem. I would be very surprised if limits and legislation in Sweden would be the same as in the USA. I know to well that US persons tend to assume that their national legislation is applicable and valid all over the world, which it is clearly not!
I have been working in a group of the Austrian Standardisation Institute on decontamination of surfaces. The problem in this tritium case is not to the surface. Anyway I refused to support the groups conclusions, because this is such an unbelievable difficult and complex question that it cannot be easily solved by just a few simple tests, even for common radionuclides. To many parameters!!!! We did not even touch the question of tritium.
---- Jerry Cohen <jjc105 at yahoo.com> schrieb:
> Based upon any credible exposure scenario, Tritium is simply not a serious
> health threat.
> So, why the concern?
> From: Scott Davidson <bsdnuke at gmail.com>
> To: The International Radiation Protection (Health Physics) Mailing List
> <radsafe at health.phys.iit.edu>
> Sent: Mon, October 31, 2011 8:26:21 AM
> Subject: Re: [ RadSafe ] Tritium contamination
> 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
> 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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Franz Schoenhofer, PhD, MinRat
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