Re: Cross Post: Radioactivity in Watches?

["Dale E. Boyce" <dale@radpro.uchicago.edu>]

Pm-147 is probably the most likely candidate, but tritium has
been used in some relatively modern watches.  I do not know
if tritium is still in use.  Pm-147 is used much as radium was
in a paint.  Tritium in the watches that I have seen, is in
small tubes that are easier to discern under low power magnification.

I have a dive watch that read about 10,000 cpm with a xtal probe.
It was barely discernable with a GM probe.  I believe it is a Pulsar, but
it may be a Citizen. I also have a Citizen watch that you cannot detect
with a xtal, but when the back is removed to change batteries,
the guts fall out exposing the face.  Exposed, the face read about
25,000 cpm with an end window GM.

Out of curiousity, what is the highest reading people have seen off
of old watches.  I have a Rolex inscribe 1951 that reads 50,000 cpm
(20 mRem) with an HP-190 end window GM.  I first learned how
hot it was by accident.  I was a grad student helping out on a research
project at Los Alamos.  I was wearing the watch which still today keeps
excellent time.  I set off the portal alarms when I walked into the
building.  I've been digital ever since.

Dale E. Boyce
dale@radpro.uchicago.edu