Re: "Who Killed the Electric Car?" opens July 14th


In article <ts08921rcopiukhoc3vs7ius8gn48v9iqv@xxxxxxx>,
Michael Benveniste <mhb-offer@xxxxxxxxxxxxxx> wrote:
On Sat, 17 Jun 2006 04:36:39 +0000 (UTC), nospam@xxxxxxxxxx (Paul
Ciszek) wrote:

Of course, that's a false either-or. India is committed to Thorium
reactors. The desirable isotope of Thorium is also the most common
(so no isotope separation); the reaction produces only as many
neutrons as it consumes, making it dependent on an outside neutron
source (no possibility of a runaway chain reaction); and none of
the products are useful in making fission weapons.

Not quite.

Any reaction which produces only as many neutrons as it consumes
would not be sustainable, as neutrons would inevitablely make
their way out of the system.

That is a feature, not a bug. The design is called a "subcritical
energy amplifier"; before someone jumps on me for claiming to violate
the first law of thermodynamics, the energy comes from fission, and
it isn't really amplification in that sense. I will give two
sources now, then go on with the description:

http://doc.cern.ch/archive/electronic/cern/preprints/lhc/lhc-96-001.pdf
http://www.inesap.org/bulletin17/bul17art25.htm
Also wiki on "energy amplifier" and "Carlo Rubbia"

You make neutrons through spallation, by hitting a target with
high energy protons. Yes, this is an added complexity that conventional
reactors don't have, but it also means that you have complete control
over the rate at which fission takes place, by modulating the proton
beam current. The reactor is designed to produce between 0.95 and
0.98 neutrons for each one consumed; for each neutron introduced
into the core, twenty to fifty fission events should take place.
Shut off the proton beam, and you shut off the fission.

Like U-238, Th-232 is not fissile. In order to burn it in a
reactor, you first have to turn it into U-233. In order to make
U-233, India is planning to use fast breeder reactors. At first,
those reactors will use either Reprossed MOX fuel (a mix of uranium,
plutonium, and a little americium). The hope is to close the cycle
eventually by running the breeders on U-233. Source:
http://www.world-nuclear.org/info/inf62.htm

This describes something different from Rubbia's design, which is
what I thought India was going to use. According to the article
you cite, they do appear to have chosen a somewhat different approach.
In Rubbia's design, the U233 is "continuously bred", meaning that
it is produced and used in situ. You don't have to take it out of
the reactor and extract it. BTW, your article does mention the
use of particle accelerators to drive subcritical reactors.

The Indian reactor unveiled in August of last year will require
2.2 tons of plutonium as "seed." Source:
http://www.hindustantimes.com/news/181_1471875,00040006.htm

Yes, that is one way to start this type of reactor; there are
others. The article you cite mentions that this can also be
considered a way to *dispose of* unwanted plutonium. BTW, this
article seems to be saying that they will be using some of
the U233 created in situ.

For making bombs, U-233 is almost as good as Pu-239. It has a
higher neutron yield than either U-235 or Pu-239. The U.S.

I was not previously aware of this twist. The second of the
papers I cited above does discuss it, and suggests "denaturing"
the fuel with U238 as a security measure. The U233 is still
there of course, but in order to purify it to bomb grade you
will need enrichment capability.

The fission products of U233 fission are supposed to have
shorter lifetimes than those of U235 and Pu fission; they
are more radioactive, but decay down to the activity level
of coal ash in centuries rather than millenia; therefore,
the storage facilities do not need to be stable for nearly
as long.


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