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Re: [Phys-L] thorium reactors



Unfortunately this is the kind of thing that happens when politicians try
to expound upon things about which they haven't the slightest clue.

On Fri, Dec 20, 2019 at 10:56 AM John Denker via Phys-l <
phys-l@mail.phys-l.org> wrote:

Hi Folks --

I don't want to get unduly political ... but by the same token,
politicians should not be magically exempted from the laws of physics.
I am appalled that the usual fact-checkers did not pick up on the
following issue:

At the debate last night, one of the candidates said the following,
which is spectacularly wrong:

And the next generation thorium reactors have a wealth of potential.
Thorium is not radioactive the way uranium is. It doesn't last as
long. And you can't make a weapon out of it.

1) Saying it "doesn't last as long" obviously contradicts the previous
sentence; if it weren't radioactive you wouldn't care how long it
lasts.

In fact, thorium reactors produce all the same nuclear waste as
uranium reactors. Actually the thorium fuel cycle is much worse, as
discussed below.

2) Minor point: Natural thorium is 99.98% ²³²Th which is /slightly/
radioactive.

3) More importantly: When it is used as reactor fuel, the first step
is to *make* it very highly radioactive. That's the whole point of
the exercise! Bombarding ²³²Th with neutrons produces ²³³Th which
decays into ²³³Pa and then ²³³U and a host of other things.

This is a really big deal for India, which has the world's largest
thorium reserves, but no uranium reserves to speak of.

4) Most importantly: Breeder reactors in general, and thorium reactors
in particular, are absolute nightmares from a weapons proliferation
point of view. Let me quote from the Bulletin of the Atomic
Scientists:

In terms of chemistry, «Protactinium behaves so differently from
thorium and uranium that, under many conditions, their separation is
inevitable.»

From there, «Compared with naturally occurring uranium 235, uranium
233 has a lower critical mass, which means that less material can be
used to build a weapon. And compared with weapons-grade plutonium 239,
uranium 233 has a much lower spontaneous fission rate, enabling
simpler weapons that are more easily constructed.»

=============

Reference:

https://thebulletin.org/2018/08/thorium-power-has-a-protactinium-problem/

You can find additional details by googling:
https://www.google.com/search?q=thorium+fuel+cycle
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