CANDU

>
> Silicon moderator probably wouldn't be very good as the best
moderators are
> elements with a low atomic mass. Silicon would probably be just too
heavy to
> work well. Even if it does work the reactor is going to be very
large.

Actually silicon is surprisingly a very good moderator. The problem is
that uranium silicide is a liquid at about 600 C. Most reactors a
running at about a 1000C.

>
> I have heard that it may be possible to use Magnesium Flouride as a
moderator

I was actually testing MgF2 as a moderator at University a lifetime
ago. It was a project that we had. It didn't do very well. Alpha rays
made it brittle.

could use
> Zirconium Deutride instead to allow Natural U to be used.
>
Interesting idea but the main problem in CANDUs at the moment is
zircomium-hydride cracking of the tubes. The uranium is contained in
Zr tubes. The heavy water at high pressure and temperature produces
zircomium hydride that crack the tubes.

> I have also been thinking about using a *gasp* plastic moderator
(would still
> require the enrichment), but the low melting point and radiation
damage
> problems plastics have would make that a bad idea.

I think the key hear is to use it as a moderator not as a support
structure. Imagine plastic pellets packed with uranium pellets. Maybe
it would work.

Bill