Re: Radium Painted Dials

[rkathren@tricity.WSU.edu (Ron L. Kathren)]

MThe reading that one would get from any radium dial time piece is a
function of the activity and the geometry, as well as the energy response of
the dectector used, and the 'filtration' through the watch crystal or cover.
At distances close to the watch/clock face, the beta contribution to dose
may be appreciable, as may the contribution from low energy x-rays.  With
all due respect, a reading of 25 mR/h migh have been very much higher if the
detector were large because of geometry considerations; similarly, it could
also be very much lower if the detector were overresponding because of
energy dependence.

A number of studies have been published with respect to the dose rate from
radium bearing time pieces and instrument dials.  According to Moghissi et
al. in 1978, there were an estimated 8.4 million radium bearing timepieces
in the US, with a mean activity of 0.5 microcurie.  The dose rate has been
estimated by Moghissi and Carter (USPHS Report FDA 76-8001, 1975) as 2.4 rem
to the wrist if the watch was worn continuously.  In addition to UNSCEAR,
those interested may wish to check NUREG/CP-0001, Radioactivity in Consumer
Products, or Radioactivity in the Environment for a summary.  p. 79 of the
latter indicates that a typical radium dial watch may contain from 0.1-3
microcuries of Ra, and indeed I have seen radium dial watches with
activities in the microcurie range, but not for many years.

Ron Kathren

At 01:46 AM 1/22/99 -0600, Michael Kay wrote:
>While you might have a book value, I have read up to 25 mR/hr from a couple
of watches (and one of them was worn crown down by the male owner!), and one
clock that could be detected at the door of the room it was in. There is
much more variation in the field than given in the book. I think the
variation is due to the source of the paint used, and maybe even the place
of manufacture. I am sorry I do not have further details as this was some
time ago.
>
>Michael Kay, ScD, CHMM
>makay@teleport.com
>
>Charles Willis wrote:
>
> Boyd:
>
> Eisenbud & Gesell offer a range of 0.01 to 0.36 microcuries per watch and
0.5 microcuries per clock.  Great variation is likely.
>
> Charlie Willis
> caw@nrc.gov
>
> >>> Boyd Imai <IMAIBM@nv.doe.gov> 01/21 4:19 PM >>>
> Any suggestions on quantifying the radium activity found on the faces of
> gauges and dials from older instrument panels?  Also, any references
> regarding the composition of radium containing paints?
>
> Send  to:
> imaibm@nv.doe.gov
>
> Thanks.
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