[Prev][Next][Index][Thread]

Re: Thoriated Tungsten vs Pure

Tesla List wrote:
> 
> >From bert.hickman-at-aquila-dot-comFri Sep 27 22:07:52 1996
> Date: Fri, 27 Sep 1996 06:31:06 -0700
> From: Bert Hickman <bert.hickman-at-aquila-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Thoriated Tungsten vs Pure
> 
> All,
> 
> I've heard three reasons for NOT using thoriated tungsten rods in a
> rotary spark gap:
> 
> 1. The thoriated kind are somewhat more expensive
> 
> 2. The doping material (Thorium) is radioactive, and when in use will
> generate particles of radioactive material that can be inhaled, etc.
> However, it must not be very radioactive, or there must not be very much
> of it in the rods since I've never seen any warning labels.
> 
> 3. Thoriating makes the rod easier to use when TIG welding since it
> helps stabilize the arc. This may be related to why thoriated tungsten
> filaments are used in high power transmitting tubes. However, if we want
> to quench the arc, wouldn't pure tungsten rods be the better choice?
> 
> I'm designing my rotary now, and need to make a materials decision.
> Thanks in advance!
> 
> -- Bert --


Bert,

Thorium is usually added to the rods in a 1% concentration (rather high 
for a radioactive).  Luckly, the surface radioactivity is rather low due 
to the fact that the bulk of the thorium is always in the rod and 
tungsten is a very dense material and absorbs most of the emitted 
particles while still in the rod.

Thorium has a nice long half life of 14 Billion years!

Most of the thoria (thorium oxide) created by arc is depositied around 
the work.  What little is breathed....well that's sort of too bad for the 
welder.  The Coleman lantern mantles are loaded with thoria!  Next time 
your out campin' thinkin' you'are breathin' in the fresh air at night 
around the campfire, realize that the folks in the city are exposed to 
the thoria that you are in the wild.

Thoriated rods are not something I would seek out.  I use pure tungsten 
and you should too.  But believe me, if I had a chance to pick up 1/2" 
diameter 10% thoriated rods cheap,  I'd burn 'em to stumps in my system.

Richard Hull, TCBOR