Neutron Activation

[kmq@cosmail1.ctd.ornl.gov (Kim McMahan)]

I have a materials trivia question.

Last summer a colleague and I participated in an accident dosimetry
intercomparison at the Los Alamos National Laboratory. We irradiated some
personnel TLDs on the standard lucite phantom, and also used styrofoam
blocks to position some of the TLDs an inch or two off the face of the
phantom to simulate the decrease in detected albedo with distance away from
the body.

We found most of the components were activated. Some, like the copper filter
in the dosimeter, were to be expected. But I'm not familiar enough with the
composition of a couple of the components to know what element(s) were
activated. Can anyone help for these two materials:

        styrofoam
        ABS plastic 

(The ABS plastic was one of the dosimeter holder materials, but it didn't
include any of the embedded filters. This was the back of the holder, which
has no filters. The only non-ABS component on the back side is a rubber
gasket, and it was removed.)

The activity was "fairly short-lived," but we were more interested in the
TLD response at the time and didn't follow the decay that closely. As I
recall, the styrofoam was at least **several** tens of thousands of cpm on a
pancake G-M. (It made a nice little contamination problem until we wrapped
it in tape.) The ABS was much less so, on the order of a few hundred cpm.
The delivered dose was about 200 rad using the bare Godiva reactor. The
approximate count rates were a couple of hours after the shot.

Thanks in advance,
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       _/_/       _/_/_/_/    _/     _/   _/     Kim McMahan, CHP
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    _/_/    _/      _/  _/     _/   _/_/_/_/_/   e-mail: mcmahankl@ornl.gov
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