[ RadSafe ] Thorium nuclear fuel cycle

George Stanford gstanford at aya.yale.edu
Tue Nov 17 16:32:40 CST 2009


      To try to put the thorium issue into some sort of perspective,
I am sending the  the message below to the editor of Chemical
and Engineering News

      Apologies to those who are getting this message more than

      --  George

      *     *    *    *

To: edit.cen at acs.org
Subject: Reintroducing Thorium

To the Editor
Chemical and Engineering News

      In his interesting article "Reintroducing Thorium" (Nov. 16), 
Mitch Jacoby has been a little too uncritical in passing along the 
rosy opinions of the thorium enthusiasts.  Here are some of the 
not-so-fine points his sources failed to tell him about.

      The article: "At no point in the thorium cycle, from mining 
thorium minerals to preparing and 'burning' reactor fuel to managing 
the waste, can fuel or waste products be converted into nuclear bomb 
materials. Unlike uranium, thorium is nuclear-proliferation proof."

      Reality:  That is just plain wrong, for at least three reasons:

-  First, while a thorium reactor can indeed be operated in a 
break-even mode (producing as much fissile fuel as it consumes), it 
has limited breeding potential, so each new one must be primed with 
fissile from elsewhere -- meaning either plutonium from today's 
reactors or enriched uranium.  Thus at least one and maybe both of 
the technologies that can separate weapons materials would continue 
to be needed as long as the thorium fleet continued to grow.

-  Second, any kind of reactor can be used to create weapons-quality 
plutonium by irradiating special uranium-containing fuel elements for 
short periods and then separating the resulting Pu-239.  Thorium 
reactors are no exception.

-  Third, isotopically pure U-233 is a good bomb material.  Some 
thorium enthusiasts like to point out that the U-233 is usually 
contaminated with U-232, rendering it too radioactive to make bombs 
with.  However, it is quite feasible to use chemical means to 
separate the 27-day Pa-233 from the fuel, and then let it decay into 
isotopically pure U-233.  In fact, that very process is part of some 
proposed thorium fuel cycles.

      In other words, for assurance that a nuclear power program is 
not being subverted, there must be effective international oversight 
of all enrichment and fuel-processing activities, regardless of 
reactor type.  The reality is that the thorium cycle has no 
significant proliferation advantage over any other nuclear fuel cycle.

      The article: "For example, [thorium] is roughly four times more 
abundant than uranium."

      Reality:  True (probably) but irrelevant.  When used in fast 
reactors, uranium itself is inexhaustible .

      The article:  "Thorium . . . does not need to undergo a costly 
and complex enrichment process to render it usable in a nuclear reactor."

      Reality:  True but misleading.  As observed above, a source of 
U-235 or Pu-239 would continue to be needed as long as new thorium 
reactors continued to come on line.  Since the supply of plutonium is 
finite, enrichment of uranium would probably continue.

      The article:  "Proponents also point out that although waste 
products from thorium usage are radioactive, radiotoxicity persists 
for just tens of years rather than thousands of years as uranium 
waste does. . . .
      "David LeBlanc, a staff physicist at Carleton University, in 
Ottawa, and a nuclear reactor specialist, points out several 
safety-related differences between LFTRs and today's commercial 
reactors. . . ."

      Reality:  Both of those statements wrongly assume that thorium 
reactors would be in competition with thermal reactors (the kind that 
are in use today).  But thorium technology is far from mature.  As 
Mr. Jacoby reports, "Several attendees at the Washington conference 
acknowledged that an enormous investment of time, effort, and money 
would be required before any new type of nuclear reactor could be 
licensed for commercial operation."  Thus the comparison that matters 
is not with today's commercial reactors, but with candidate 
"Generation IV" reactors. Of the latter, one of the leading 
contenders is the metal-fueled, sodium-cooled fast-reactor system 
known as the IFR (Integral Fast Reactor), which is not mentioned in 
the article but has very similar advantages over today's 
reactors.  IFR technology is now so close to maturity that General 
Electric is prepared to do a commercial demonstration as soon as seed 
money and regulatory approval materialize.

                         *     *     *     *

       While the thorium cycle offers a clean, feasible, and possibly 
economical way to generate electricity, it is farther in the future 
than its main competitor, the IFR.  Continued development of the 
thorium cycle would not be unreasonable, but avoiding prompt 
demonstration of the IFR technology would be a mistake.  There is 
lots of room for healthy competition as reactor deployment proceeds.

George S. Stanford, Ph.D.
Reactor physicist, retired from Argonne National Laboratory


At 04:48 PM 11/16/2009, Jaro Franta wrote:
FYI, here's a new article in Chemical & Engineering News:

Reintroducing Thorium
November 16, 2009 Volume 87, Number 46 pp. 44-46
A largely forgotten natural resource holds vast nuclear power potential


-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf
Of Otto G. Raabe
Sent: November-12-09 6:04 PM
To: radsafe at radlab.nl>
Subject: [ RadSafe ] Thorium nuclear fuel cycle

November 12, 2009

Can anyone provide some information about the thorium nuclear fuel
cycle and the reason it is supposed to be a better
proliferation-resistant nuclear fuel cycle.



Prof. Otto G. Raabe, Ph.D., CHP
Center for Health & the Environment
University of California
One Shields Avenue
Davis, CA 95616
E-Mail: ograabe at ucdavis.edu
Phone: (530) 752-7754   FAX: (530) 758-6140
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