Thorium: Preferred Nuclear Fuel of the Future
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NUCLEAR REPORT
USGS
India has a plentiful supply of thorium
in the rare earth monazite, found in its
beach sands. At left, workers transport
sand to the Rare Earth Processing Plant
at Alwaye. Inset is a backscattered
electron image of a monazite crystal.
Pure thorium is silver in color, but it
becomes gray and then black as it
oxidizes.
Information Service of India
There is a significant reduction in the
Thorium: Preferred plutonium content of the spent fuel,
compared with what comes out of a
conventional uranium-fueled reactor.
Nuclear Fuel of the Future Just how much less plutonium is
made? The answer depends on exactly
how the uranium and thorium are com-
by Ramtanu Maitra bined. For example, uranium and thori-
um can be mixed homogeneously with-
in each fuel rod, and in this case the
T horium is an abundant element in
nature with multiple advantages as a
nuclear fuel for future reactors of all
work have motivated the Indian nuclear
engineers to use thorium-based fuels in
their current plans for the more
amount of plutonium produced is
roughly halved. But mixing them uni-
formly is not the only way to combine
types. Thorium ore, or monazite, exists advanced reactors that are now under the two elements, and the mix deter-
in vast amounts in the dark beach sand construction. mines the plutonium production.
of India, Australia, and Brazil. It is also India decided on a three-stage nuclear Indian Initiatives
found in large amoungs in Norway, the program back in the 1950s, when its To a certain extent, India has complet-
United States, Canada, and South Africa. nuclear power generation program was ed the first stage of its nuclear program,
Thorium-based fuel cycles have been set up. In the first stage, natural uranium putting on line a dozen nuclear power
studied for about 30 years, but on a (U-238) was used in pressurized heavy plants so far, with a few more plants now
much smaller scale than uranium or ura- water reactors (PHWRs), of which there in the construction process.
nium/plutonium cycles. Germany, India, are now 12. In the second stage, the The second stage is as yet realized
Japan, Russia, the United Kingdom, and plutonium extracted from the spent fuel only by a small experimental fast breed-
the United States have conducted of the PHWRs was scheduled to be used er reactor (13 megawatts), at Kalpakkam.
research and development, including to run fast breeder reactors. The fast Meanwhile, the Indian authorities have
irradiating thorium fuel in test reactors to breeders would burn a 70-percent approved the Department of Atomic
high burn-ups. Several reactors have mixed oxide (MOX) fuel to breed fissile Energy’s proposal to set up a 500-MW
used thorium-based fuel, as discussed uranium-233 (U-233) in a thorium-232 prototype of the next-generation fast
below. (Th-232) blanket around the core. In the breeder nuclear power reactor at
India is by far the nation most com- final stage, the fast breeders would use Kalpakkam, thereby setting the stage for
mitted to study and use of thorium fuel; Th-232 and produce U-233 for use in the commercial exploitation of thorium
no other country has done as much neu- new reactors. as a fuel source.
tron physics work on thorium as have One main advantage of using a com- India’s commitment to switch over to
Indian nuclear scientists. The positive bination of thorium and uranium is thorium stems, in part, from its large
results obtained in this neutron physics related to the proliferation question: indigenous thorium supply. India’s esti-
NUCLEAR REPORT 21st CENTURY Fall 2005 45mated thorium reserves are 290,000 being the rare earth thorium-phosphate
tons, second only to Australia. But the mineral, monazite, which usually con- WORLD THORIUM RESOURCES
(economically extractable)
nation’s pursuit of thorium, which helps tains from 3 to 9 percent, and sometimes
bring it independence from overseas up to 12 percent thorium oxide. In India, Reserves
Country (tons)
uranium sources, came about for a rea- the monazite is found in its southern ____________________________
son that has nothing to do with its bal- beach sands. Australia 300,000
ance of trade. Th-232 decays very slowly (its half-life India 290,000
India is a nonsignatory of the Nuclear is about three times the age of the Earth). Norway 170,000
Non-Proliferation Treaty (NPT). Hence, Most other thorium isotopes are short- USA 160,000
India foresaw that it would be con- lived and thus much more radioactive
Canada 100,000
strained in the long term by the provi- than Th-232, but of negligible quantity.
South Africa 35,000
sions laid down by the commercial ura- In addition to thorium’s abundance,
nium suppliers, which would jeopardize all of the mined thorium is potentially Brazil 16,000
India’s nuclear power generation pro- usable in a reactor, compared with only Other countries 95,000
gram. The 44-member nuclear suppliers 0.7 percent of natural uranium. In other World total 1,200,000
group requires that purchasers sign the words, thorium has some 40 times the Source: U.S. Geological Survey, Mineral
Commodity Summaries, January 1999.
NPT, and thereby allow enough over- amount of energy per unit mass that
sight to ensure that the fuel (or the plu- could be made available, compared
tonium spawned from it) is not used for with uranium.
making nuclear weapons. From the technological angle, one There are some other benefits. For
India began the construction on the reason that thorium is preferred over example, thorium oxide, the form of tho-
facility for reactor physics of the enriched uranium is that the breeding of rium used for nuclear power, is a highly
Advanced Heavy Water Reactor U-233 from thorium is more efficient stable compound—more so than the
(AHWR) last year. The AHWR will use than the breeding of plutonium from uranium dioxide that is usually
thorium, the “fuel of the future,” to gen- U-238. This is so because the thorium employed in today’s conventional
erate 300 megawatts of electricity, up fuel creates fewer non-fissile isotopes. nuclear fuel. Also, the thermal conduc-
from its original design output of 235 Fuel-cycle designers can take advantage tivity of thorium oxide is 10 to 15 per-
megawatts. The reactor will have a life- of this efficiency to decrease the amount cent higher than that of uranium diox-
time of 100 years, and is scheduled to be of spent fuel per unit of energy generat- ide, making it easier for heat to flow out
built on the campus of India’s main ed, which reduces the amount of waste of the fuel rods used inside a reactor.
nuclear research and development cen- to be disposed of. In addition, the melting point of thori-
ter, the Bhabha Atomic Research Center
(BARC) at Trombay.
The construction of the AHWR will
mark the beginning of the third phase of
India’s nuclear electricity-generation
program. The fuel for the AHWR will be
a hybrid core, partly thorium/uranium-
233, and partly thorium-plutonium. The
reactor will be a technology demonstra-
tor for thorium utilization. According to
B. Bhattacharjee, Director of the
Bhabha Atomic Research Center, “At the
international level, the AHWR has been
selected for a case study at the IAEA
[International Atomic Energy Agency]
for acceptance as per international stan-
dards for next-generation reactors.”
Abundance of Thorium
Although India’s embrace of thorium
as its future nuclear fuel is based mostly
on necessity, the thorium fuel cycle itself
has many attractive features. To begin Information Service of India
with, thorium is much more abundant in The Bhabha Atomic Research Center (BARC) in Trombay, India. Thorium fuel cycles
nature than uranium. Soil commonly have been intensively studied here, and the design phase of the thorium-fueled
contains an average of around 6 parts Advanced Heavy Water Reactor is under way. At an August meeting in Brussels on
per million (ppm) of thorium, three times emerging reactor designs, two BARC scientists unveiled their design for an
as much as uranium. Thorium occurs in Advanced Thorium Breeder reactor (ATBR) that can produce 600 MW of electricity
several minerals, the most common for two years, with no refueling.
46 Fall 2005 21st CENTURY NUCLEAR REPORTum oxide is about 500 degrees Celsius higher than that of urani- um dioxide, which gives the reactor an additional safety mar- gin, if there is a temporary loss of coolant. The one challenge in using thorium as a fuel is that it requires neutrons to start off its fission process. These neutrons can be provided by the conventional fis- sioning of uranium or plutonium fuel mixed into the thorium, or by a particle accelerator. Most of the past thorium research has involved combining thorium with conventional nuclear fuels to provide the neutrons to trigger the fission process. The approach undergoing the SIMPLIFIED DIAGRAM OF THE THORIUM FUEL CYCLE most investigation now is a com- The neutron trigger to start the thorium cycle can come from the fissioning of con- bination that keeps a uranium- ventional nuclear fuels (uranium or plutonium) or an accelerator. When neutrons hit rich “seed” in the core, separate the fertile thorium-232 it decays to the fissile U-233; a neutron striking the U-233 from a thorium-rich “blanket.” leads to fission products, more neutrons, and a lot of energy. (Not shown is the short- The chief proponent of this con- lived intermediate stage of protactinium-233.) cept was the late Alvin Radkowsky, a nuclear pioneer who, under the direction of Admiral Hyman Rickover, helped to launch America’s Nuclear Navy during the 1950s, when he was chief scientist of the U.S. Naval Reactors Program. Radkowsky, who died in 2002 at age 86, headed up the design team that built the first U.S. civilian nuclear reactor at Shippingport, Pennsylvania, and made significant contributions to the commercial nuclear industry during the 1960s and 1970s. Although thorium is not fissile like U-235, Th-232 absorbs slow neutrons to produce U-233, which is fissile. In other words, Th-232 is fertile, like U-238. The Th-232 absorbs a neutron to become Th-233, which decays to protactinium-233 (Pa-233) and then to fissionable U-233. When SIMPLIFIED DIAGRAM OF THE URANIUM FUEL CYCLE the irradiated fuel is unloaded In the conventional uranium fuel cycle, the fuel mix contains fissionable U-235 and from the reactor, the U-233 can fertile U-238. A few fast neutrons are released into the reactor core (for example, from be separated from the thorium, a beryllium source), and when a neutron hits a U-235 nucleus, it splits apart, pro- and then used as fuel in another ducing two fission fragments (lighter elements) and two or three new neutrons. Once nuclear reactor. the fission process is initiated, it can continue by itself in a chain reaction, as the neu- Uranium-233 is superior to the trons from each fissioned uranium nucleus trigger new fissions in nearby nuclei. conventional nuclear fuels, U- Some of the U-238, when hit by a neutron, decays to plutonium-239, which is also 235 and Pu-239, because it has a fissionable. higher neutron yield per neutron NUCLEAR REPORT 21st CENTURY Fall 2005 47
absorbed. This means that once it is acti- twisted three-section rods, which are three times as fast as MOX at a signifi-
vated by neutrons from fissile U-235 or 12.75-mm wide, with cladding of zirco- cantly lower cost. Spent thorium fuel
Pu-239, thorium’s breeding cycle is nium alloy (See page 51). would be more proliferation-resistant
more efficient than that using U-238 The blanket consists of uranium-tho- than spent MOX fuel. . . . [The thorium
and plutonium. rium oxide fuel pellets (in a ratio of fuel technology] will not require signifi-
The Russian-U.S. Program uranium to thorium of 1:9, with the cant and costly reactor modifications.
Since the early 1990s, Russia has had a uranium enriched up to almost 20 per- Thorium fuel also offers additional ben-
program based at Moscow’s Kurchatov cent) in 228 cladding tubes of zirconi- efits in terms of reduced weight and vol-
Institute to develop a thorium-uranium um alloy, 8.4-mm diameter. These pel- ume of spent fuel and therefore lower
fuel. The Russian program involves the lets are in four layers around the center disposal costs.”
U.S. company Thorium Power, Inc. portion. The blanket material achieves Four Decades of R&D
(founded by Radkowsky), which has U.S. 100 gigawatt-days burn-up. Together as Concepts for advanced reactors based
government and private funding to design one fuel assembly, the seed and blan- on thorium fuel cycles include:
fuel for the conventional Russian VVER- ket have the same geometry as a nor- Light Water Reactors. Fuels based on
1000 reactors. Unlike the usual nuclear mal VVER-100 fuel assembly. plutonium oxide (PuO2), thorium oxide
fuel, which uses enriched uranium oxide, As reported by Grae et al. (see note 4), (ThO2), and/or uranium oxide (UO2)
the new fuel assembly design has the plu- thorium fuel burns 75 percent of the particles are arranged in fuel rods.
tonium in the center as the “seed,” in a originally loaded weapons-grade pluto- High-Temperature Gas-cooled Reactors
demountable arrangement, with the thori- nium, compared with a 31 percent burn (HTGR). These are of of two kinds: the
um and uranium around it as a “blanket.” for mixed oxide (MOX) fuel, which is pebble bed and the prismatic fuel
A normal VVER-1000 fuel assembly made of a mixture of uranium and plu- design.
has 331 fuel rods, each of 9-millimeter tonium. But unlike MOX, thorium fuel The Pebble Bed Modular Reactor
diameter, forming a hexagonal assembly does not produce more plutonium and (PBMR) originated in Germany, and is
235-mm wide. The center portion of has cost advantages over MOX. Grae et now being developed in South Africa
each assembly is 155-mm across and al. conclude: and in China. It can potentially use thori-
holds the seed material, consisting of “Thorium fuel offers a promising um in its fuel pebbles.
metallic plutonium-zirconium alloy means to dispose of excess weapons- The Gas Turbine-Modular Helium
(about 10 percent of the alloy is plutoni- grade plutonium in Russian VVER-1000 Reactor (GT-MHR) was developed in the
um, of which more than 90 percent is reactors. Using the thorium fuel technol- United States by General Atomics using a
the isotope Pu-239) in the form of 108 ogy, plutonium can be disposed of up to prismatic fuel. The use of helium as a
Thorium Converter Reactor Ready for Development
A n attorney-inventor working with
Lawrence Berkeley National
Laboratory physicists has proposed a
mission lines. Its small size also allows
it to be factory-built and transported to
its destination, “plugged in” in a deep
The self-regulating reactor is expected
to operate for 10 years without needing
refueling. The neutrons to start it up will
small 50-megawatt-thermal thorium underground containment structure, be provided by a fusion-driven neutron
converter reactor for multiple uses: pro- and put to work quickly. The core can generator, designed by Dr. Ka-No Leung,
ducing electricity (15 megawatts), burn- be shipped back to the factory when head of Plasma and Ion Source
ing up high-level actinides from spent the fuel needs to be changed. Technology under the Accelerator and
fuel, and producing low-cost, high-tem- The reactor configuration is differ- Fusion Research Division of the
perature steam (or process industrial ent from the Radkowsky design in the Lawrence Berkeley National Laboratory.
heat). This high-temperature steam can Russian thorium-burning reactors. Its The alloy and fuel configuration are
be used for extraction of oil from tar ceramic fuel is dispersed in an inert expected to be tested at the Advanced
sands, or desalinating, purifying, and metal matrix covered by Holden’s pro- Thermal Reactor testing complex at the
cracking water. The reactor’s fuel matrix visional patents. This solid state metal Idaho National Lab; computer model-
can be “tuned” to provide the right out- alloy is composed of four materials. ling of the system will also be done in
put for each particular work process. The thorium and uranium fuel parti- the national laboratory system.
Designed by Charles S. Holden, cles are embedded in the alloy, which Holden and Pui’s company,
working with physicist Tak Pui Lou, both slows and moderates the fission- Thorenco LLC, is now looking for
the reactor core is a squat cylinder, ing process. Using the metal as a mod- investors to develop a commercial
about 3 meters wide and 1 meter tall. erator (instead of the water used in prototype. Thorenco is based in San
Its size makes it portable, so that it can other thorium reactor designs) allows Francisco, and can be reached by e-
be brought to a remote work site and the reactor to operate in a more ener- mail at rusthold@mindspring.com or
supply electricity there without getic neutron spectrum so that its core by telephone 415-398-7878.
dependence on long-distance trans- can have a long life. —Marjorie Mazel Hecht
48 Fall 2005 21st CENTURY NUCLEAR REPORTcoolant at high temperature, ball-size fuel elements.
and the relatively small power Overall, a total of 1,360 kilo-
output per module (600 grams of thorium was used,
megawatts-thermal), permit mixed with highly enriched
direct coupling of the reactor to uranium (HEU). Maximum
a gas turbine (a Brayton cycle), burn-ups of 150,000
resulting in power generation at megawatt-days were
48 percent thermal efficiency achieved.
(which is 50 percent more effi- Thorium fuel elements with
cient than the conventional a 10:1 ratio of thorium to high-
nuclear reactors in use today). ly enriched uranium were irra-
The GT-MHR core can accom- diated in the 20-megawatts-
modate a wide range of fuel thermal (MWt) Dragon reactor
options, including highly at Winfrith, United Kingdom,
enriched uranium/thorium, U- for 741 full-power days.
233/Th, and Pu/Th. The use of Dragon was run as a coopera-
highly enriched uranium/thori- tive project of the Organiza-
um fuel was demonstrated in tion of Economic Cooperation
General Atomics’ Fort St. Vrain and Development and Eur-
reactor in Colorado (see atom, involving Austria,
below). Denmark, Sweden, Norway,
Molten salt reactors. This and Switzerland, in addition to
advanced breeder concept the United Kingdom, from
circulates the fuel in molten 1964 to 1973. The thorium-ura-
salt, without any external nium fuel was used to “breed
coolant in the core. The pri- and feed,” so that the U-233
Philadelphia Electric Co.
mary circuit runs through a that was formed, replaced the
heat exchanger, which trans- General Atomics’ Peach Bottom reactor, 65 miles southwest U-235 at about the same rate,
fers the heat from fission to a of Philadelphia, began commercial operation in 1967. This and fuel could be left in the
secondary salt circuit for high-temperature, graphite-moderated, helium-cooled reactor for about six years.
steam generation. It was stud- reactor operated between 1967 and 1974 at 110-MWt, using The General Atomics Peach
ied in depth in the 1960s, highly enriched uranium with thorium. Bottom high-temperature,
and is now being revived graphite-moderated, helium-
because of the availability of ad- which can readily be turned off, and used cooled reactor (HTGR) in the United
vanced technology for the materials either for power generation or destruction States operated between 1967 and 1974
and components. of actinides resulting from the at 110-MWt, using highly enriched ura-
Advanced Heavy Water Reactor uranium/plutonium fuel cycle. The use of nium with thorium.
(AHWR). India is working on this, and thorium instead of uranium means that In India, the Kamini 30-kWt experi-
like the Canadian CANDU-NG, this 250- fewer new actinides are produced in the mental neutron-source research reactor
megawatt-electric (MWe) design is light- accelerator-driven system itself. started up in 1996 near Kalpakkam,
water cooled. The main part of the core is The difficulties, as of now, in develop- using U-233 which was recovered from
subcritical, with Th/U-233 oxide, mixed ing the thorium fuel cycle include the thorium-dioxide fuel that had been
so that the system is self-sustaining in U- high cost of fuel fabrication. This is part- irradiated in another reactor. The
233. A few seed regions with convention- ly because of the high radioactivity of Kamini reactor is adjacent to the 40-MWt
al MOX fuel will drive the reaction and U-233, which is always contaminated Fast Breeder Test Reactor, in which the
give it a negative void coefficient overall. with traces of U-232; similar problems thorium-dioxide is irradiated.
(In other words, as the reactor heats up, in recycling thorium because of the In the Netherlands, an aqueous
the fission process slows down.) highly radioactive Th-228, and some homogenous suspension reactor has
Accelerator Driven Systems (ADS). In weapons proliferation risk of U-233; and operated at 1 megawatt-thermal for three
accelerator driven systems, high-energy the technical problems (not yet satisfac- years. The highly enriched uranium/
neutrons are produced through the spal- torily solved) in reprocessing. thorium fuel is circulated in solution,
lation reaction of high-energy protons Thorium Fuel Operating Experience and reprocessing occurs continuously to
from an accelerator striking target heavy Between 1967 and 1988, the AVR remove fission products, resulting in a
nuclei (lead, lead-bismuth, or other mate- experimental pebble bed reactor at high conversion rate to U-233.
rials). These neutrons can be directed to a Jülich, Germany, operated for more Thorium in Power Reactors
subcritical reactor containing thorium, than 750 weeks at 15 megawatts- The 300-MWe THTR reactor in
where the neutrons breed U-233 and electric, about 95 percent of the time Germany was developed from the AVR,
promote its fission. There is therefore the with thorium-based fuel. The fuel used and operated between 1983 and 1989
possibility of sustaining a fission reaction consisted of about 100,000 billiard with 674,000 pebbles, over half of them
NUCLEAR REPORT 21st CENTURY Fall 2005 49containing thorium/highly enriched ura- vations that would make it harder to Power) and its partners in their tests with
nium fuel (the rest of the pebbles were divert nuclear materials into bomb-mak- Russian reactors, as well as three other
graphite moderator and some neutron ing. The thorium fuel cycle is one such efforts (two national laboratories, two
absorbers). These pebbles were continu- technical innovation—as yet untapped. fuel fabrication companies, and a con-
ously recycled on load, and on average A 1998 paper by Radkowsky and sortium of three universities). This
the fuel passed six times through the Galparin (see note 8) describes the most research is geared to designing a thori-
core. Fuel fabrication was on an indus- advanced work in developing a practical um fuel system that will fit with conven-
trial scale. nuclear power system that could be tional reactors. (See box, p. 48, for
The Fort St. Vrain reactor in Colorado made more “proliferation resistant” than another thorium design.) There is also a
was the only commercial thorium-fueled conventional reactors and fuel cycles. new company, Novastar Resources, that
nuclear plant in the United States. Based on a thorium fuel cycle, it has the is buying up thorium mines in anticipa-
Developed from the AVR in Germany, it potential to reduce the amount of pluto- tion of thorium-fueled reactors in the
operated from 1976 to 1989. It was a nium generated per gigawatt-year by a future.
high-temperature (700°C), graphite- factor of five, compared to conventional The proliferation potential of the light
moderated, helium-cooled reactor with uranium-fueled reactors. It would also water reactor fuel cycle may be signifi-
a thorium/highly enriched uranium fuel, make the generated plutonium and ura- cantly reduced by using thorium as a fer-
which was designed to operate at 842 nium-233 much more difficult to use for tile component of the nuclear fuel, as
megawatts-thermal (330 MWe). The fuel producing bomb material. noted above. The main challenge of tho-
was contained in microspheres of thori- Heightened current concerns about rium utilization is to design a core and a
um carbide and Th/U-235 carbide, coat- preventing the spread of bomb-making fuel cycle that would be proliferation-
ed with silicon oxide and pyrolytic car- materials, have led to an increase in resistant and economically feasible. This
bon to retain fission products. interest in developing thorium-based challenge is met by the Radkowsky
Unlike the pebble bed design, the fuel fuels. The U.S. Department of Energy has Thorium Reactor concept. So far, the
was arranged in hexagonal columns funded Radkowsky’s company (Thorium concept has been applied to a Russian
(“prisms”) in an annular configuration.
Almost 25 tons of thorium were used in
the reactor fuel, achieving a 170,000-
megawatt-days burn-up.
Thorium-based fuel for Pressurized
Water Reactors (PWRs) was investigated
at the Shippingport reactor in the United
States (the first U.S. commercial reactor,
started up in 1957), using both U-235
and plutonium as the initial fissile materi-
al. It was concluded that thorium would
not significantly affect operating strategies
or core margins. The light water breeder
reactor (LWBR) concept was also success-
fully tested at Shippingport, from 1977 to
1982, with thorium and U-233 fuel clad
with zircaloy, using the “seed/blanket”
concept.
Another reactor type, the 60-MWe
Lingen Boiling Water Reactor (BWR) in
Germany also utilized fuel test elements
that were thorium-plutonium based.
Proliferation Issues
In the early days of the civilian
nuclear program, the Acheson-Lilienthal (1) Horizontal steam generator (4) Refueling crane
Report in 1946 warned of the connec- (2) Reactor coolant pump (5) Control rod drive assemblies
(3) Containment building (6) Reactor vessel
tion between civilian nuclear power and
Argonne National Laboratory
nuclear weapons, and concluded that
the world could not rely on safeguards CUTAWAY VIEW OF THE VVER-1000
alone “to protect complying states The 1,000-MW VVER, Russia’s conventional reactor design is shown here in
against the hazards of violations and its third-generation version. It is a pressurized light-water-cooled and
evasions”—illicit nuclear weapons. -moderated reactor, similar to Western pressurized water reactors in operation
Acheson-Lilienthal proposed interna- and safety standards. The Thorium Power/Radkowsky design would modify the
tional controls over nuclear power, but core for a thorium fuel cycle that would burn up weapons-grade plutonium.
also considered possible technical inno-
50 Fall 2005 21st CENTURY NUCLEAR REPORT(a) (b)
Courtesy of Thorium Power, Inc.
Radkowsky design for the thorium seed/blanket
assembly. The seed fuel is the inner part of the fuel
rod (three-sectioned), and the blanket fuel is the
outer part. The thorium fuel assembly is designed to
Nukeworker.com
replace the current fuel assembly, without requiring a
VVER fuel rod assembly major design rehaul.
1981. “Thorium” in Nuclear Chemical
design of a 1,000-MW pressurized water military nuclear power. Engineering (2nd Ed.), Chapter 6. (New York:
reactor VVER, designated as VVERT. Other scientists point out that even if McGraw-Hill) pp. 283-317.
The main results of the preliminary a terrorist group wanted to use the blan- 2. EIA, 1996. “The Role of Thorium in Nuclear
Energy.” (Washington, D.C.: Energy
reference design are as follows: The ket plutonium for making a bomb, the Information Administration/Uranium Industry
amount of plutonium contained in the process of extracting it from thorium Annual, 1996), pp. ix-xvii.
Radkowsky Thorium Reactor spent fuel fuel would be more difficult than 3. R. L. Garwin and G. Charpak, 2002.
stockpile is reduced by 80 percent, in removing it from conventional spent Megawatts and Megatons (Chicago:
University of Chicago Press).
comparison with a VVER of convention- fuel. This is because the spent blanket 4. Seth Grae, Dr. Alexei G. Morozov, and Dr.
al design. The isotopic composition of fuel from a thorium fuel cycle would Andrey Mushakov, 2005. “Thorium Fuel As a
the reactor’s plutonium greatly increases contain uranium-232, which over time Superior Approach to Disposing of Excess
Weapons-grade Plutonium in Russian VVER-
the probability of pre-initiation and yield decays into isotopes that emit high- 1000 Reactors,” Nuclear Future (Jan.-Feb.
degradation of a nuclear explosion. An energy gamma rays. To extract the plu- 2005). (Journal of the Institute of Nuclear
extremely large Pu-238 content causes tonium from this spent fuel would Engineers and the British Nuclear Energy
Society)
correspondingly large heat emission, require significantly more radiation 5. IAEA, 2000. “Thorium-based Fuel Options
which would complicate the design of shielding plus additional remotely oper- for the Generation of Electricity: Develop-
an explosive device based on plutonium ated equipment in order to reprocess it ments in the 1990s,” IAEA-TECDOC-1155.
(Vienna: International Atomic Energy Agency,
from this reactor. for weapons use, making a daunting May).
The economic incentive to reprocess task even more difficult. It would also 6. M.S. Kazimi, 2003. “Thorium Fuel for Nuclear
and reuse the fissile component of the be more complicated to separate the fis- Energy,” American Scientist (Sept.-Oct.).
Radkowsky Thorium Reactor spent fuel sionable U-233 from uranium-238, 7. J. Carson Mark, 1993. “Explosive Properties of
Reactor-grade Plutonium,” Science and
is also decreased. The once-through because of the highly radioactive prod- Global Security, Vol. 4, pp. 111-128.
cycle is economically optimal for its ucts present. 8. A. Radkowsky and A. Galperin, 1998. “The
core and cycle. Overall, the development of thorium Nonproliferative Light Water Reactor: A New
Approach to Light Water Reactor Core
To reiterate the proliferation difficul- fuel cycles makes sense for the future, Technology,” Nuclear Technology, Vol. 124,
ties: the replacement of a standard (ura- for advancing the efficiency and econo- pp. 215-222 (Dec.).
nium-based) fuel for nuclear reactors of my of nuclear power plants, ease of 9. S. Shwageraus, X. Zhao, M. Driscoll, P.
current generation by the Radkowsky recycling, and making it more difficult to Hejzlar, M.S. Kazimi, and J.S. Herring. “Micro-
heterogeneous Thoria-urania Fuels for
Thorium Reactor fuel will provide a divert radioactive materials for weapons. Pressurized Water Reactors,” Nuclear
strong barrier for nuclear weapon prolif- Ramtanu Maitra, a nuclear engineer, Technology (in press).
eration. This barrier, in combination with is a member of 21st Century’s scientific 10. Richard Wilson, 1977. “How to Have Nuclear
Power Without Nuclear Weapons,” Bulletin of
existing safeguard measures and proce- advisory board. the Atomic Scientists (Nov.).
dures, is adequate to unambiguously dis- Sources: __________________________________
associate civilian nuclear power from 1. M. Benedict, T. H. Pigford, and H.W. Levi,
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