[ RadSafe ] Thorium nuclear fuel cycle
George Stanford
gstanford at aya.yale.edu
Wed Nov 18 16:46:14 CST 2009
Mike:
Thanks for the kind words.
In my opinion, the worry over terrorists making A-bombs
from such materials is way overblown -- it takes too much
time and technical sophistication. .Just the preliminary task,
extracting U-233 from used fuel, would be far beyond a terrorist
group's capabilities. They'd have to live long enough to finish
the job, and they'd be sacrificing their best and brightest.
The main concern is national subversion of a technical
base to embark on a surreptitious weapons program (think
Iran). That's why international oversight of enrichment and
fuel-processing facilities is so important. Without access
to one or the other of those, a nation cannot make weapons,
no matter how many reactors it has.
-- George
~~~~~~~~~~~~~~~~~~~~~~~~
At 03:52 PM 11/18/2009, Brennan, Mike (DOH) wrote:
Hi, George.
I think this is a good and worthy letter. I also think you are perhaps
the perfect person for it to come from. The only additional point I
might make is that in addition to the scenario for producing clean
U-233, one could separate out the uranium from the fuel, and just not
worry about the U-232. The extra activity is only a problem if you want
the people making your bomb to survive, and perhaps if you are looking
for optimal energy release (I don't know how U-232 would affect the
neutron economy of a potential weapon, and really don't care enough to
research it). If sacrificing your own people is acceptable, and if the
bomb is more for PR than actual destruction, then contaminated U-233 is
probably good enough.
-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of George Stanford
Sent: Tuesday, November 17, 2009 2:33 PM
To: radsafe at radlab.nl
Subject: RE: [ RadSafe ] Thorium nuclear fuel cycle
All:
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
once.
-- 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:
http://pubs.acs.org/cen/email/html/8746sci2.html
Reintroducing Thorium
November 16, 2009 Volume 87, Number 46 pp. 44-46
A largely forgotten natural resource holds vast nuclear power potential
Jaro
^^^^^^^^^^^^^^^^^^^^^^^^^
-----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.
Thanks,
Otto
**********************************************
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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