tritium x-rays -Reply

[FRAMEP@ORAU.GOV]

Les:

Thanks for the good info. This is a useful discussion. 

First, wrt Dale's question about uranium in black ceramic glaze. I
don't know why uranium was used, as opposed to some other means for
producing a black glaze. I know Coor's used it until 1989 to produce
black spot plates - as hot or hotter than Fiesta ware. Bill Kolb
might know. Are you there Bill?  

>With multicurie tritium sources (both tritium adsorbed into titanium
>and tritium encapsulated in glass) I have detected x-rays with G-M
>and ion chamber detectors. 

I believe the typical level of H-3 in a watch was on the order of 2
mCi. (NCRP 95). I would also think that the manufacturer would use a
crystal thick enough to take out the bremsstrahlung.

>The discriminator on a low energy NaI may prevent detection with
>that detector.

Good point! It didn't have a discriminator but the threshold setting
might have been too high. Shame on me for not checking that out.

> But I would have thought the effective x-ray energy would be
>higher, given the strong energy dependence on beta energy in
>producing these.

The maximum energy of the bremstrahlung is the same as the maximum
beta energy i.e. 18.6 keV. But for protection purposes, we assume
that the bremsstrahlung energy is the maximum possible. Like you say,
it would be nice to see some data here.
 
>The note regarding tritium contamination causing interference in the
>Am-241 measurements was curious, since it would take close to a
>curie of tritium to produce detectable reading.  A hell-of-a-lot of
>contamination.

Thats what I thought too. But I just found a statement in the DOE HP
Manual of Good Practices for Tritium Facilities.(MLM-3719)"for highly
contaminated surfaces (>1 mCi/100 sq cm), it is possible to use a
thin sodium iodide crystal or a thin window GM tube" to measure the
bremsstrahlung. A watch might have that. Would it get out? Hmmm.

Interesting

Paul Frame