Thorium gas mantles -Reply

[FRAMEP@ORAU.GOV]

Bruce Pickett wrote:

> the past year or two, the mantles have no longer contained
>radioactive materials (I suspect that the mantle manufacturers got
>tired of being held up as examples by the nuclear industry, so they
>eliminated the use of thorium).
 >Can anyone answer these questions:

 >(1) Have all manufacturers of gas mantles stopped using thorium?
Its been about two years since I bothered to check this out but at
the time, Coleman was making nonradioactive mantles in the US but
still importing some radioactive ones from its overseas facilities
in, I think, Malaysia and Malta. I also believe the Alladin Lamp
Company still imports thorium mantles from Brazil. Maybe we can get
an update from someone.

>(2) I've always thought that the thorium was intentionally used to
>increase the luminosity of the burning gas mantles; what has
>replaced the thorium and is it as effective in brightening the
>light?
The light is given off by the heated thorium i.e. it is incandescent
light. The burning gas heats the thorium. I believe that the
replacements use yttrium rather than thorium  The light output from
the yttrium is 20% less than with thorium but the mantles are
supposed to last longer.

>(3) In a thorium gas mantle, what percentage of the thorium burns
>off and what remains in the mantle ash?
Don't have info on this but I'd suspect almost all of it remains in
the ash. Some of the daughters will have burned off though. Why not
do a gamma spec analysis?

>(4) What is considered to be an "average" activity for thorium
>mantles and how much variability is there?
I believe a typical value is between 250 and 400mg of Th per mantle.

Paul Frame
Professional Training Programs
ORISE
framep@orau.gov