[ RadSafe ] An interesting article. Cleaner Nuclear Power?

[Brennan, Mike (DOH)]

I have nothing against the concept of using thorium in reactors.  Given
that thorium is, I've read, more common than uranium it seems like a
reasonable path to explore.  But selling it on the basis of being
"cleaner" is problematic.  There are several incorrect statements in the
article.

I do not agree that diversion of spent fuel by terrorist groups in order
to process out material for nuclear weapons is an issue (governments
that own the reactors are a different story).  But if that is what you
is worried about, then you need to be as concerned about diversion of
U233 as you are about Pu239.  U233 can be used to make nuclear weapons,
just as Pu239 can.  U233 is somewhat difficult to handle, as it is more
radioactive per unit weight than Pu239, but that really doesn't matter
when talking about commercial reactor fuel, as such fuel will have
significant amounts of Pu240 and Pu241.  These isotopes build up the
longer the fuel cooks in the reactor, are almost impossible to separate
from the Pu239.  The both increase the amount of plutonium needed for a
critical mass and greatly increase the radioactivity of the plutonium.
Thus the thorium cycle does not seem to have an advantage over the
plutonium cycle from a non-proliferation point of view.  

The article says that the thorium fuel rods will be left in the reactor
for a long time, which is good, but only if it actually decreases the
amount of time the reactor is off line.  From what I know about current
reactor design, even fuel rods that "stay in the reactor" through a
refueling cycle often get moved from one part of the reactor to another
in order to balance neutron flux and burn-up.  I suspect that such
movement would be required in a hybrid reactor, too.  The article says,
"The DOE's plan is to burn recovered plutonium by blending it with
uranium. This produces a hotter and more toxic spent fuel that can only
be burned in breeder reactors. Those reactors have, to date, proved
infeasible at commercial scale."  I am fairly certain that fuel rods
with a mixture of plutonium and uranium can and are being used in
regular pressurized and boiling water reactors.  I know that in
commercial reactors a non-trivial amount of energy comes from the
fission of plutonium that is bred in the fuel rods in the reactor, as
part of normal operations.  As for breeder reactors, I believe the lack
of feasibility is political, not economical.

The main issue as to whether or not the thorium cycle is "cleaner" or
not comes down to the amount of waste per net unit of energy produced.
I assume that the mix of fission products for U233 is different than for
U235 or Pu239, but I don't see that that will make a practical
difference.  The waste will be as hot, and the challenges of what to do
with it will remain.  (NOTE: the challenges are not nearly as
insurmountable as some people like to claim.)

All in all: an interesting subject, but a poorly done article that, by
leaving out and/or misstating important points, leaves me at least as
skeptical about the superiority of thorium as a nuclear fuel.

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of ROY HERREN
Sent: Monday, November 26, 2007 10:29 PM
To: radsafe at radlab.nl
Subject: [ RadSafe ] An interesting article. Cleaner Nuclear Power?

Cleaner Nuclear Power?  http://www.technologyreview.com/Energy/19758/
   


Roy Herren
       
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