[ RadSafe ] RE: Thorium nuclear fuel cycle
Jaro Franta
jaro-10kbq at sympatico.ca
Sun Dec 13 19:45:11 CST 2009
Thanks George,
In a more recent comment about an article in the Economist Magazine
(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
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>
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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