[ RadSafe ] RE: Thorium nuclear fuel cycle
George Stanford
gstanford at aya.yale.edu
Sun Dec 13 21:06:46 CST 2009
Jaro:
A fast reactor certainly produces a lot of TRU -- that's part
of its raison d'etre. The question is how much comes out into the
waste stream (assuming a break-even cycle). My thinking was
this: The goal of the IFR program is to have >99.5% consumption of
actinides, or maybe better -- there's a cost trade-off. That would
mean that 0.5% of the waste stream would be actinides.
How much of that would be TRU? Since most of the heavy metal
in the IFR recycling stream is uranium, I'll guess (just a guess)
that maybe 40% of the residual actinides in the waste stream would be
TRU -- i.e., 0.2% of the waste stream, or ~2 kg per GWe-yr. That's
versus some 200 kg of TRU per GWe-yr in LWR spent fuel.
That's just the TRU. My statement was that " the amount of
long-lived waste from SFRs is no greater than that from MSRs." In
both cases, we have something like 50 - 100 kg of long-lived fission
products per GWe-yr, overshadowing the TRU for at least for several
tens of millennia. In other words, the long-lived-waste problem for
the two technologies seems comparable.
I'd appreciate comments & corrections from those closer to the
nitty-gritty (of both technologies) than I am. If the MSR in some
scenarios has a second-order advantage, so be it.
Best,
-- George
~~~~~~~~~~~~~~~~~~~~~~~~~~~
At 07:45 PM 12/13/2009, Jaro Franta wrote:
Thanks George,
In a more recent comment about an article in the Economist Magazine
(<http://www.economist.com/comment/435611#comment-435611>http://www.economist.com/comment/435611#comment-435611
), you state that,
Which reactor type is "best"? That depends on what characteristic
you're looking at.
Since they can consume the transuranic elements almost completely,
the amount of long-lived waste from SFRs is no greater than that from MSRs.
For very rapid expansion of nuclear power, the MSR is best, because
it needs less fissile material (mainly plutonium from thermal-reactor
spent fuel) per unit of capacity.<end quote>
I can certainly agree with your second comment, about expansion of
nuclear: it is simply due to the fact that thermal neutron reactors
need less fissile load than fast ones -- and the more thermal, the
greater the difference (i.e. less difference for epithermal reactor types...)
Your first comment however, bears some explaining, because a reactor
using a significant fraction of Th produces less TRUs in the first
place; Secondly, the much higher HM load in a fast reactor means that
losses to the waste stream from fuel processing are greater (and
quite significant!).
How did you come to your conclusion ?
Jaro
^^^^^^^^^^^^^^^^^^^^^^^^^
From: cdn-nucl-l-admin at mailman1.cis.McMaster.CA
[mailto:cdn-nucl-l-admin at mailman1.cis.McMaster.CA] On Behalf Of George Stanford
Sent: November-17-09 5:16 PM
To: Jaro Franta
Cc: cdn-nucl-l at mailman1.cis.McMaster.CA
Subject: Re: [cdn-nucl-l] Thorium nuclear fuel cycle
Jaro:
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
-- 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>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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