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| [[File:Thorium sample 0.1g.jpg|thumb|250px|A sample of [[thorium]].]]
| | Andera is what you can call her [http://hknews.classicmall.com.hk/groups/some-simple-tips-for-personal-development-progress/ email psychic readings] but she never really favored [http://kard.dk/?p=24252 psychic readings online] that name. One of the issues she enjoys most is canoeing and she's been performing it for quite a while. North Carolina is where we've been living for years and will never move. Distributing manufacturing is exactly where my main earnings comes from and it's some thing I truly enjoy.<br><br>Feel free to surf to my weblog: clairvoyance ([http://Medialab.Zendesk.com/entries/54181460-Will-You-Often-End-Up-Bored-Try-One-Of-These-Hobby-Ideas- http://Medialab.Zendesk.com/]) |
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| The '''thorium fuel cycle''' is a [[nuclear fuel cycle]] that uses the naturally abundant [[isotope]] of [[thorium]], {{SimpleNuclide2|Thorium|232|link=yes}}, as the [[fertile material]]. In the reactor, {{SimpleNuclide2|Thorium|232}} is [[Nuclear transmutation|transmuted]] into the [[fissile]] artificial [[uranium]] isotope {{SimpleNuclide2|Uranium|233|link=yes}} which is the [[nuclear fuel]]. Unlike [[natural uranium]], natural thorium contains only trace amounts of fissile material (such as {{SimpleNuclide2|Thorium|231|link=yes}}), which are insufficient to initiate a [[nuclear chain reaction]]. Additional fissile material or another neutron source are necessary to initiate the fuel cycle. In a thorium-fueled reactor, {{SimpleNuclide2|Thorium|232}} absorbs [[neutron]]s eventually to produce {{SimpleNuclide2|Uranium|233}}. This parallels the process in uranium [[breeder reactor]]s whereby fertile {{SimpleNuclide2|Uranium|238|link=yes}} absorbs neutrons to form fissile {{SimpleNuclide2|Plutonium|239|link=yes}}. Depending on the design of the reactor and fuel cycle, the generated {{SimpleNuclide2|Uranium|233}} either fissions [[in situ]] or is chemically separated from the [[used nuclear fuel]] and formed into new nuclear fuel.
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| The thorium fuel cycle claims several potential advantages over a [[uranium fuel cycle]], including thorium's [[Thorium#Occurrence|greater abundance]], superior physical and nuclear properties, better resistance to [[nuclear proliferation|nuclear weapons proliferation]]<ref>{{Cite doi|10.1080/08929880108426485}} [http://www.torium.se/res/Documents/9_1kang.pdf]</ref><ref>[http://nuclearweaponarchive.org/Nwfaq/Nfaq6.html Nuclear Materials] FAQ</ref><ref name="Hargraves-Moir">{{cite web |url=http://www.aps.org/units/fps/newsletters/201101/hargraves.cfm |title=Liquid Fuel Nuclear Reactors |author=Robert Hargraves |coauthors=Ralph Moir |date= January 2011 |work=[[American Physical Society]] Forum on Physics & Society |accessdate=31 May 2012}}</ref> and reduced [[plutonium]] and [[actinide]] production.<ref name="Hargraves-Moir" />
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| ==History==
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| Concerns about the [[Uranium depletion|limits of worldwide uranium resources]] motivated initial interest in the thorium fuel cycle.<ref name="Thorium Fuel Cycle - Potential Benefits and Challenges" /> It was envisioned that as uranium reserves were depleted, thorium would supplement uranium as a fertile material. However, for most countries uranium was relatively abundant and research in thorium fuel cycles waned. A notable exception was [[India's three stage nuclear power programme]].<ref>{{cite book|
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| author = Ganesan Venkataraman|
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| title = Bhabha and his magnificent obsessions, page 157|
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| year = 1994|
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| publisher = Universities Press}}</ref>
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| In the twenty-first century thorium's potential for improving proliferation resistance and [[nuclear waste|waste]] characteristics led to renewed interest in the thorium fuel cycle.<ref>{{cite web| url= http://www-pub.iaea.org/MTCD/publications/PDF/te_1349_web.pdf
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| |publisher= International Atomic Energy Agency
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| |title= IAEA-TECDOC-1349 Potential of thorium-based fuel cycles to constrain plutonium and to reduce the long-lived waste toxicity |year= 2002 |accessdate= 2009-03-24}}</ref><ref>
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| {{cite news | url= http://www.abc.net.au/news/newsitems/200604/s1616391.htm | title= Scientist urges switch to thorium |last=Evans |first=Brett |date= April 14, 2006 |work= |publisher= [[ABC News (Australia)|ABC News]] |archiveurl=http://web.archive.org/web/20100328211103/http://www.abc.net.au/news/newsitems/200604/s1616391.htm|archivedate=2010-03-28| accessdate= 2011-09-17 }}</ref><ref>{{cite news |url= http://www.wired.com/magazine/2009/12/ff_new_nukes/ |last=Martin |first=Richard |work= [[Wired (magazine)|Wired]] |date= December 21, 2009 | title= Uranium Is So Last Century — Enter Thorium, the New Green Nuke | accessdate= 2010-06-19 }}</ref>
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| At [[Oak Ridge National Laboratory]] in the 1960s, the [[Molten-Salt Reactor Experiment]] used {{SimpleNuclide2|Uranium|233}} as the fissile fuel as an experiment to demonstrate a part of the Molten Salt Breeder Reactor that was designed to operate on the thorium fuel cycle. [[Molten Salt Reactor]] (MSR) experiments assessed thorium's feasibility, using [[thorium(IV) fluoride]] dissolved in a [[molten salt]] fluid which eliminated the need to fabricate fuel elements. The MSR program was defunded in 1976 after its patron [[Alvin Weinberg]] was fired.<ref>{{cite web |last=Miller|first=Daniel| title=Nuclear community snubbed reactor safety message: expert|url= http://www.abc.net.au/news/2011-03-18/nuclear-community-snubbed-reactor-safety-message/2649768|work= ABC News|date=March 2011 | accessdate= 2012-03-25 }}</ref>
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| In 2006, [[Carlo Rubbia]] proposed the concept of an [[energy amplifier]] or "accelerator driven system" (ADS), which he saw as a novel and safe way to produce nuclear energy that exploited existing accelerator technologies. Rubbia's proposal offered the potential to incinerate high-activity nuclear waste and produce energy from natural [[thorium]] and depleted [[uranium]].<ref>{{cite web |last=Dean |first=Tim| title=New age nuclear |url= http://www.cosmosmagazine.com/features/print/348/new-age-nuclear?page=0%2C3 |work= [[Cosmos (magazine)|Cosmos]] |date=April 2006 | accessdate= 2010-06-19 }}</ref><ref>
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| {{cite book
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| | url= http://www.inference.phy.cam.ac.uk/withouthotair/c24/page_166.shtml
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| | title= Sustainable Energy - without the hot air
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| | last= MacKay |first= David J. C. |authorlink= David J. C. MacKay
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| | date= February 20, 2009 |publisher= UIT Cambridge Ltd. |page= 166 | accessdate= 2010-06-19 }}</ref>
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| [[Kirk Sorensen]], former NASA scientist and Chief Nuclear Technologist at [[Teledyne Brown Engineering]], has been a long time promoter of thorium fuel cycle and particularly [[liquid fluoride thorium reactor]]s (LFTRs). He first researched thorium reactors while working at [[NASA]], while evaluating power plant designs suitable for lunar colonies. In 2006 Sorensen started "energyfromthorium.com" to promote and make information available about this technology.<ref>{{cite web|url=http://flibe-energy.com/ |title=Flibe Energy |publisher=Flibe Energy |date= |accessdate=2012-06-12}}</ref>
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| A 2011 MIT study concluded that, although there is little in the way of barriers to a thorium fuel cycle, with current or near term light-water reactor designs there is also little incentive for any significant market penetration to occur. As such they conclude there is little chance of thorium cycles replacing conventional uranium cycles in the current nuclear power market, despite the potential benefits.<ref>{{Cite report |date=2011 |title=The Future of the Nuclear Fuel Cycle (Full Report) |url=http://mitei.mit.edu/publications/reports-studies/future-nuclear-fuel-cycle |publisher=MIT |page=181 }}</ref>
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| ==Nuclear reactions with thorium==
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| In the thorium cycle, fuel is formed when {{SimpleNuclide2|Thorium|232}} [[neutron capture|captures]] a [[neutron]] (whether in a [[fast reactor]] or [[thermal reactor]]) to become {{SimpleNuclide2|Thorium|233|link=yes}}. This normally emits an [[electron]] and an [[antineutrino|anti-neutrino]] ({{SubatomicParticle|Antineutrino}}) by [[beta decay|{{SubatomicParticle|beta-}} decay]] to become {{SimpleNuclide2|Protactinium|233|link=yes}}. This then emits another electron and anti-neutrino by a second {{SubatomicParticle|beta-}} decay to become {{SimpleNuclide2|Uranium|233}}, the fuel:
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| :<math>\mathrm{n}+{}_{\ 90}^{232}\mathrm{Th}\rightarrow {}_{\ 90}^{233} \mathrm{Th} \xrightarrow{\beta^-} {}_{\ 91}^{233}\mathrm{Pa} \xrightarrow{\beta^-} {}_{\ 92}^{233}\mathrm{U}</math>
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| ===Fission product wastes===
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| [[Nuclear fission]] produces radioactive [[fission product]]s which can have half-lives from [[LLFP#Short-term|days]] to [[LLFP|greater than 200,000 years]]. According to some toxicity studies,<ref name="LEBRUN">{{cite web |url= http://hal.archives-ouvertes.fr/docs/00/04/14/97/PDF/document_IAEA.pdf |format=PDF |last=Le Brun |first=C. |coauthors= L. Mathieu, D. Heuer and A. Nuttin | title= Impact of the MSBR concept technology on long-lived radio-toxicity and proliferation resistance |date= |year= |month= |work= |publisher= Technical Meeting on Fissile Material Management Strategies for Sustainable Nuclear Energy, Vienna 2005 | accessdate= 2010-06-20 }}</ref> the thorium cycle can fully recycle actinide wastes and only emit fission product wastes, and after a few hundred years, the waste from a thorium reactor can be less toxic than the [[uranium ore]] that would have been used to produce [[low enriched uranium]] fuel for a [[light water reactor]] of the same power.
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| Other studies assume some actinide losses and find that actinide wastes dominate thorium cycle waste radioactivity at some future periods.<ref name="BRISSOT">{{cite web |url= http://lpsc.in2p3.fr/gpr/english/NEWNRW/NEWNRW.html#foot284 |title= Nuclear Energy With (Almost) No Radioactive Waste? |quote=according to computer simulations done at ISN, this Protactinium dominates the residual toxicity of losses at {{val|10000|u=years}} |month= July |year= 2001 |author= Brissot R.; Heuer D.; Huffer E.; Le Brun, C.; Loiseaux, J-M; Nifenecker H.; Nuttin A. |publisher= Laboratoire de Physique Subatomique et de Cosmologie (LPSC)}}</ref>
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| ===Actinide wastes===
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| In a reactor, when a neutron hits a fissile atom (such as certain isotopes of uranium), it either splits the nucleus or is captured and transmutes the atom. In the case of {{SimpleNuclide2|Uranium|233}}, the transmutations tend to produce useful nuclear fuels rather than [[transuranic]] wastes. When {{SimpleNuclide2|Uranium|233}} absorbs a neutron, it either fissions or becomes {{SimpleNuclide2|Uranium|234|link=yes}}. The chance of fissioning on absorption of a [[thermal neutron]] is about 92%; the capture-to-fission ratio of {{SimpleNuclide2|Uranium|233}}, therefore, is about 1:10 — which is better than the corresponding capture vs. fission ratios of {{SimpleNuclide2|Uranium|235|link=yes}} (about 1:6), or {{SimpleNuclide2|Plutonium|239}} (about 1:2), or {{SimpleNuclide2|Plutonium|241|link=yes}} (about 1:4).<ref name="Thorium Fuel Cycle - Potential Benefits and Challenges">
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| {{cite web
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| |url=http://www-pub.iaea.org/MTCD/publications/PDF/TE_1450_web.pdf
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| |format=PDF
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| |publisher=International Atomic Energy Agency
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| |title=IAEA-TECDOC-1450 Thorium Fuel Cycle-Potential Benefits and Challenges
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| |date=May 2005
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| |accessdate=2009-03-23
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| }}</ref>
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| The result is less [[transuranic]] waste than in a reactor using the uranium-plutonium fuel cycle.
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| {{Thorium Cycle Transmutation}}
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| {{SimpleNuclide2|Uranium|234}}, like most [[actinide]]s with an even number of neutrons, is not fissile, but neutron capture produces fissile {{SimpleNuclide2|Uranium|235}}. If the fissile isotope fails to fission on neutron capture, it produces {{SimpleNuclide2|Uranium|236|link=yes}}, {{SimpleNuclide2|Neptunium|237|link=yes}}, {{SimpleNuclide2|Plutonium|238|link=yes}}, and eventually fissile {{SimpleNuclide2|Plutonium|239}} and heavier [[isotopes of plutonium]].
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| The {{SimpleNuclide2|Neptunium|237}} can be removed and stored as waste or retained and transmuted to plutonium, where more of it fissions, while the remainder becomes {{SimpleNuclide2|Plutonium|242|link=yes}}, then [[americium]] and [[curium]], which in turn can be removed as waste or returned to reactors for further transmutation and fission.
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| However, the {{SimpleNuclide2|Protactinium|231|link=yes}} (with a half-life of {{val|3.27|e=4|u=years}}) formed via (''n'',2''n'') reactions with {{SimpleNuclide2|Thorium|232}} (yielding {{SimpleNuclide2|Thorium|231}} that decays to {{SimpleNuclide2|Protactinium|231|link=yes}}), while not a transuranic waste, is a major contributor to the long term [[radiotoxic]]ity of spent nuclear fuel.
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| ===Uranium-232 contamination===
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| [[Uranium-232]] is also formed in this process, via (''n'',2''n'') reactions between [[fast neutron]]s and {{SimpleNuclide2|Uranium|233}}, {{SimpleNuclide2|Protactinium|233|link=yes}}, and {{SimpleNuclide2|Thorium|232}}:
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| :<math>\mathrm{n}+{}_{\ 90}^{232}\mathrm{Th}\rightarrow {}_{\ 90}^{233} \mathrm{Th} \xrightarrow{\beta^-} {}_{\ 91}^{233}\mathrm{Pa} \xrightarrow{\beta^-} {}_{\ 92}^{233}\mathrm{U}+\mathrm{n}\rightarrow {}_{\ 92}^{232} \mathrm{U}+2\mathrm{n}</math>
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| :<math>\mathrm{n}+{}_{\ 90}^{232}\mathrm{Th}\rightarrow {}_{\ 90}^{233} \mathrm{Th} \xrightarrow{\beta^-} {}_{\ 91}^{233}\mathrm{Pa}+\mathrm{n} \rightarrow {}_{\ 91}^{232}\mathrm{Pa}+2\mathrm{n} \xrightarrow{\beta^-} {}_{\ 92}^{232}\mathrm{U}</math>
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| :<math>\mathrm{n}+{}_{\ 90}^{232}\mathrm{Th}\rightarrow {}_{\ 90}^{231} \mathrm{Th} + 2\mathrm{n} \xrightarrow{\beta^-} {}_{\ 91}^{231}\mathrm{Pa}+\mathrm{n} \rightarrow {}_{\ 91}^{232}\mathrm{Pa} \xrightarrow{\beta^-}{}_{\ 92}^{232}\mathrm{U}</math>
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| Uranium-232 has a relatively short half-life ({{val|68.9|u=years}}), and some [[decay product]]s emit high energy [[gamma radiation]], such as {{SimpleNuclide2|Radon|224|link=yes}}, {{SimpleNuclide2|Bismuth|212|link=yes}} and particularly {{SimpleNuclide2|Thallium|208|link=yes}}. The [[thorium series|full decay chain]], along with half-lives and relevant gamma energies, is:
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| [[File:Decay chain(4n,Thorium series).PNG|thumb|right|300px]]{{SimpleNuclide2|Uranium|232|link=yes}} decays to {{SimpleNuclide2|Thorium|228|link=yes}} where it joins [[thorium series|decay chain of {{SimpleNuclide2|Thorium|232}}]]
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| :<math>{}_{\ 92}^{232}\mathrm{U} \xrightarrow{\ \alpha\ } {}_{\ 90}^{228}\mathrm{Th}\ \mathrm{(68.9\ a)}</math>
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| :<math>{}_{\ 90}^{228}\mathrm{Th} \xrightarrow{\ \alpha\ } {}_{\ 88}^{224}\mathrm{Ra}\ \mathrm{(1.9\ a)}</math>
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| :<math>{}_{\ 88}^{224}\mathrm{Ra} \xrightarrow{\ \alpha\ } {}_{\ 86}^{220}\mathrm{Rn}\ \mathrm{(3.6\ d,\ 0.24\ MeV)}</math>
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| :<math>{}_{\ 86}^{220}\mathrm{Rn} \xrightarrow{\ \alpha\ } {}_{\ 84}^{216}\mathrm{Po}\ \mathrm{(55\ s,\ 0.54\ MeV)}</math>
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| :<math>{}_{\ 84}^{216}\mathrm{Po} \xrightarrow{\ \alpha\ } {}_{\ 82}^{212}\mathrm{Pb}\ \mathrm{(0.15\ s)}</math>
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| :<math>{}_{\ 82}^{212}\mathrm{Pb} \xrightarrow{\beta^-\ } {}_{\ 83}^{212}\mathrm{Bi}\ \mathrm{(10.64\ h)}</math>
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| :<math>{}_{\ 83}^{212}\mathrm{Bi} \xrightarrow{\ \alpha\ } {}_{\ 81}^{208}\mathrm{Tl}\ \mathrm{(61\ m,\ 0.78\ MeV)}</math>
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| :<math>{}_{\ 81}^{208}\mathrm{Tl} \xrightarrow{\beta^-\ } {}_{\ 82}^{208}\mathrm{Pb}\ \mathrm{(3\ m,\ 2.6\ MeV)}</math>
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| Thorium-cycle fuels produce hard [[gamma emission]]s, which damage electronics, limiting their use in military bomb triggers. {{SimpleNuclide2|Uranium|232}} cannot be chemically separated from {{SimpleNuclide2|Uranium|233}} from [[used nuclear fuel]]; however, chemical separation of thorium from uranium removes the decay product {{SimpleNuclide2|Thorium|228}} and the radiation from the rest of the decay chain, which gradually build up as {{SimpleNuclide2|Thorium|228}} reaccumulates. The hard gamma emissions also create a radiological hazard which requires remote handling during reprocessing.
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| ==Advantages as a nuclear fuel==
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| Thorium is estimated to be about three to four times more abundant than uranium in the Earth's crust,<ref name="The Use of Thorium as Nuclear Fuel">{{cite web
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| |url=http://www.ans.org/pi/ps/docs/ps78.pdf
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| |format=PDF
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| |publisher=American Nuclear Society
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| |title=The Use of Thorium as Nuclear Fuel
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| |date=November 2006
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| |accessdate=2009-03-24
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| }}</ref> although present knowledge of [[Thorium#Distribution|reserves]] is limited. Current demand for thorium has been satisfied as a by-product of [[rare earth element|rare-earth]] extraction from [[monazite]] sands. Also, unlike uranium, mined thorium consists of a single isotope ({{SimpleNuclide2|Thorium|232}}). Consequently, it is useful in [[thermal reactor]]s without the need for isotope separation.
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| Thorium-based fuels exhibit several attractive properties relative to uranium-based fuels. The thermal neutron absorption [[nuclear cross section|cross section]] (σ<sub>a</sub>) and [[resonance integral]] (average of neutron cross sections over intermediate neutron energies) for {{SimpleNuclide2|Thorium|232}} are about three times and one third of the respective values for {{SimpleNuclide2|Uranium|238}}; consequently, fertile conversion of thorium is more efficient in a [[thermal reactor]]. Also, although the thermal neutron fission cross section (σ<sub>f</sub>) of the resulting {{SimpleNuclide2|Uranium|233}} is comparable to {{SimpleNuclide2|Uranium|235}} and {{SimpleNuclide2|Plutonium|239}}, it has a much lower capture cross section (σ<sub>γ</sub>) than the latter two fissile isotopes, providing fewer non-fissile neutron absorptions and improved [[neutron economy]]. Finally, the ratio of neutrons released per neutron absorbed (η) in {{SimpleNuclide2|Uranium|233}} is greater than two over a wide range of energies, including the thermal spectrum; as a result, thorium-based fuels can be the basis for a [[Breeder reactor#Thermal breeder reactors|thermal breeder reactor]].<ref name="Thorium Fuel Cycle - Potential Benefits and Challenges" />
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| Thorium-based fuels also display favorable physical and chemical properties which improve reactor and [[deep geological repository|repository]] performance. Compared to the predominant reactor fuel, [[uranium dioxide]] ({{chem||UO|2}}), [[thorium dioxide]] ({{chem|ThO|2}}) has a higher [[melting point]], higher [[thermal conductivity]], and lower [[coefficient of thermal expansion]]. Thorium dioxide also exhibits greater [[chemical stability]] and, unlike uranium dioxide, does not further [[oxidize]].<ref name="Thorium Fuel Cycle - Potential Benefits and Challenges" />
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| Because the {{SimpleNuclide2|Uranium|233}} produced in thorium fuels is inevitably contaminated with {{SimpleNuclide2|Uranium|232}}, thorium-based [[used nuclear fuel]] possesses inherent [[nuclear proliferation|proliferation]] resistance. {{SimpleNuclide2|Uranium|232}} can not be [[separation process|chemically separated]] from {{SimpleNuclide2|Uranium|233}} and has several [[decay product]]s which emit high energy [[gamma radiation]]. These high energy photons are a [[ionizing radiation|radiological hazard]] that necessitate the use of [[remote handling]] of separated uranium and aid in the passive [[nuclear detection|detection]] of such materials.
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| {{SimpleNuclide2|Uranium|233}} can be [[Denaturation (fissile materials)|denatured]] by mixing it with natural or [[depleted uranium]], requiring [[isotope separation]] before it could be used in nuclear weapons.
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| The long term (on the order of roughly {{val|e=3}} to {{val|e=6|u=years}}) radiological hazard of conventional uranium-based used nuclear fuel is dominated by plutonium and other [[minor actinide]]s, after which [[long-lived fission products]] become significant contributors again. A single neutron capture in {{SimpleNuclide2|Uranium|238}} is sufficient to produce [[transuranic elements]], whereas six captures are generally necessary to do so from {{SimpleNuclide2|Thorium|232}}. 98–99% of thorium-cycle fuel nuclei would fission at either {{SimpleNuclide2|Uranium|233}} or {{SimpleNuclide2|Uranium|235}}, so fewer long-lived transuranics are produced. Because of this, thorium is a potentially attractive alternative to uranium in [[MOX fuel|mixed oxide (MOX) fuels]] to minimize the generation of transuranics and maximize the destruction of plutonium.<ref name=wnn-20130621>{{cite news |url=http://www.world-nuclear-news.org/ENF_Thorium_test_begins_2106131.html |title=Thorium test begins |publisher=World Nuclear News |date=21 June 2013 |accessdate=21 July 2013}}</ref>
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| ==Disadvantages as nuclear fuel==
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| There are several challenges to the application of thorium as a nuclear fuel, particularly for solid fuel reactors:
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| Unlike uranium, natural thorium contains no fissile isotopes; fissile material, generally {{SimpleNuclide2|Uranium|233}}, {{SimpleNuclide2|Uranium|235}} or plutonium, must be added to achieve [[nuclear chain reaction|criticality]]. This, along with the high [[sintering]] temperature necessary to make thorium-dioxide fuel, complicates fuel fabrication. [[Oak Ridge National Laboratory]] experimented with [[thorium tetrafluoride]] as fuel in a [[molten salt reactor]] from 1964–1969, which was far easier to both process and separate from contaminants that slow or stop the chain reaction.
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| In an [[Nuclear fuel cycle#Once-through nuclear fuel cycle|open fuel cycle]] (i.e. utilizing {{SimpleNuclide2|Uranium|233}} in situ), higher [[burnup]] is necessary to achieve a favorable [[neutron economy]]. Although thorium dioxide performed well at burnups of 170,000 MWd/t and 150,000 MWd/t at [[Fort St. Vrain Generating Station]] and [[AVR reactor|AVR]] respectively,<ref name="Thorium Fuel Cycle - Potential Benefits and Challenges" /> challenges complicate achieving this in [[light water reactor]]s (LWR), which compose the vast majority of existing power reactors.
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| In a once-through thorium fuel cycle the residual {{SimpleNuclide2|U|233}} is long lived radioactive waste.
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| Another challenge associated with the thorium fuel cycle is the comparatively long interval over which {{SimpleNuclide2|Thorium|232}} breeds to {{SimpleNuclide2|Uranium|233}}. The [[half-life]] of {{SimpleNuclide2|Protactinium|233}} is about 27 days, which is an order of magnitude longer than the half-life of {{SimpleNuclide2|Neptunium|239|link=yes}}. As a result, substantial {{SimpleNuclide2|Protactinium|233}} develops in thorium-based fuels. {{SimpleNuclide2|Protactinium|233}} is a significant [[neutron absorber]], and although it eventually [[breeder reactor|breeds]] into fissile {{SimpleNuclide2|Uranium|235}}, this requires two more neutron absorptions, which degrades [[neutron economy]] and increases the likelihood of [[transuranic element|transuranic]] production.
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| Alternatively, if solid thorium is used in a [[Nuclear fuel cycle#Plutonium cycle|closed fuel cycle]] in which {{SimpleNuclide2|Uranium|233}} is [[nuclear reprocessing|recycled]], [[remote handling]] is necessary for fuel fabrication because of the high radiation levels resulting from the [[decay products]] of {{SimpleNuclide2|Uranium|232}}. This is also true of recycled thorium because of the presence of {{SimpleNuclide2|Thorium|228}}, which is part of the {{SimpleNuclide2|Uranium|232}} decay sequence. Further, unlike proven uranium fuel recycling technology (e.g. [[PUREX]]), recycling technology for thorium (e.g. THOREX) is only under development.
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| Although the presence of {{SimpleNuclide2|Uranium|232}} complicates matters, there are public documents showing that {{SimpleNuclide2|Uranium|233}} has been used once in a [[nuclear weapon]] test. The United States tested a composite {{SimpleNuclide2|Uranium|233}}-plutonium bomb core in the MET (Military Effects Test) blast during [[Operation Teapot]] in 1955, though with much lower yield than expected.<ref>{{cite web
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| | url= http://nuclearweaponarchive.org/Usa/Tests/Teapot.html
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| | title= Operation Teapot
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| | date= 15 October 1997 | work= Nuclear Weapon Archive |publisher=
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| | accessdate= 2008-12-09 }}</ref>
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| Though thorium-based fuels produce far less long-lived [[transuranic elements|transuranics]] than uranium-based fuels,<ref name="LEBRUN" />
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| some long-lived [[actinide]] products constitute a long term radiological impact, especially {{SimpleNuclide2|Protactinium|231}}.<ref name="BRISSOT" />
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| Advocates for liquid core and [[molten salt reactor]]s such as [[LFTR]] claim that these technologies negate thorium's disadvantages present in solid fueled reactors. Since only two liquid core fluoride salt reactors have been built (the ORNL [[Aircraft_Reactor_Experiment#Direct_Air_Cycle|ARE]] and [[Molten-Salt Reactor Experiment|MSRE]]) and neither used thorium, it is hard to validate the exact benefits.<ref name="Thorium Fuel Cycle - Potential Benefits and Challenges" />
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| ==Reactors==
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| Thorium fuels have fueled several different reactor types, including [[light water reactor]]s, [[heavy water reactor]]s, [[HTGR|high temperature gas reactor]]s, [[sodium-cooled fast reactor]]s, and [[molten salt reactor]]s.<ref name="Thorium Fuel Utilization: Options and trends">
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| {{cite web
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| |url=http://www.iaea.org/inisnkm/nkm/aws/fnss/fulltext/te_1319_f.pdf
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| |publisher=International Atomic Energy Agency
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| |title=IAEA-TECDOC-1319 Thorium Fuel Utilization: Options and trends
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| |date=November 2002
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| |accessdate=2009-03-24
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| }}</ref>
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| ===List of thorium-fueled reactors===
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| From IAEA TECDOC-1450 "Thorium Fuel Cycle - Potential Benefits and Challenges", Table 1: Thorium utilization in different experimental and power reactors.<ref name="Thorium Fuel Cycle - Potential Benefits and Challenges" /> Additionally, [[Dresden Generating Station|Dresden 1]] in the USA used "thorium oxide corner rods".<ref>{{cite book|title=Spent Nuclear Fuel Discharges from U. S. Reactors (1993)|url=http://books.google.com/books?id=uwJr2SAEdqUC&pg=PA111|accessdate=11 June 2012|year=1995|publisher=[[Energy Information Administration]]|isbn=978-0-7881-2070-1|page=111}} They were manufactured by [[General Electric]] (assembly code XDR07G) and later sent to the [[Savannah River Site]] for reprocessing.</ref>
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| {| class="wikitable sortable"
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| |- style="text-align:center; background:#f0f0f0;"
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| ||'''Name'''
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| ||'''Country'''
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| ||'''Type'''
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| ||'''Power'''
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| ||'''Fuel'''
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| ||'''Operation period'''
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| |-
| |
| | [[AVR Reactor|AVR]] || Germany ||[[HTGR]], Experimental ([[Pebble bed reactor]]) || <span style="display:none;">015000</span> 15 MW(e)||Th+{{SimpleNuclide2|Uranium|235}} Driver Fuel, Coated fuel particles, Oxide & dicarbides||1967–1988
| |
| |-
| |
| | [[THTR-300]] || Germany || [[HTGR]], Power ([[Pebble bed reactor|Pebble Type]]) || <span style="display:none;">300000</span> 300 MW(e) || Th+{{SimpleNuclide2|Uranium|235}}, Driver Fuel, Coated fuel particles, Oxide & dicarbides || 1985–1989
| |
| |-
| |
| | [[Lingen Nuclear Power Plant|Lingen]] || Germany||[[BWR]] Irradiation-testing || <span style="display:none;">060000</span> 60 MW(e)||Test Fuel (Th,Pu)O<sub>2</sub> pellets || 1968-1973
| |
| |-
| |
| | [[Dragon reactor|Dragon]] ([[OECD]]-[[Euratom]]) || UK (also Sweden, Norway & Switzerland) ||[[HTGR]], Experimental (Pin-in-Block Design) || <span style="display:none;">020000</span> 20 MWt || Th+{{SimpleNuclide2|Uranium|235}} Driver Fuel, Coated fuel particles, Oxide & Dicarbides||1966–1973
| |
| |-
| |
| | [[Peach Bottom Nuclear Generating Station|Peach Bottom]] || USA ||[[HTGR]], Experimental (Prismatic Block) || <span style="display:none;">040000</span> 40 MW(e) || Th+{{SimpleNuclide2|Uranium|235}} Driver Fuel, Coated fuel particles, Oxide & dicarbides || 1966–1972
| |
| |-
| |
| | [[Fort St. Vrain Generating Station|Fort St Vrain]] || USA || [[HTGR]], Power (Prismatic Block) || <span style="display:none;">330000</span> 330 MW(e) || Th+{{SimpleNuclide2|Uranium|235}} Driver Fuel, Coated fuel particles, Dicarbide || 1976–1989
| |
| |-
| |
| | [[Molten Salt Reactor Experiment|MSRE]] [[ORNL]] || USA || [[Molten salt reactor|MSBR]] || <span style="display:none;">007500</span> 7.5 MWt || {{SimpleNuclide2|Uranium|233}} Molten Fluorides || 1964–1969
| |
| |-
| |
| | [[BORAX-IV]] & [[Elk River Station]] || USA || BWR (Pin Assemblies) || <span style="display:none;">002400</span> 2.4 MW(e); 24 MW(e) || Th+235U Driver Fuel Oxide Pellets || 1963 - 1968
| |
| |-
| |
| | [[Shippingport Reactor|Shippingport]] || USA|| [[Breeder reactor#Thermal breeder reactors|LWBR PWR]], (Pin Assemblies) || <span style="display:none;">100000</span> 100 MW(e) || Th+{{SimpleNuclide2|Uranium|233}} Driver Fuel, Oxide Pellets || 1977–1982
| |
| |-
| |
| | [[Indian Point Energy Center#Unit 1|Indian Point 1]] || USA || [[Breeder reactor#Thermal breeder reactors|LWBR PWR]], (Pin Assemblies) || <span style="display:none;">285000</span> 285 MW(e) || Th+{{SimpleNuclide2|Uranium|233}} Driver Fuel, Oxide Pellets || 1962–1980
| |
| |-
| |
| | SUSPOP/KSTR [[KEMA]] || Netherlands || Aqueous Homogenous Suspension (Pin Assemblies) || <span style="display:none;">001000</span> 1 MWt || Th+HEU, Oxide Pellets || 1974–1977
| |
| |-
| |
| | [[NRX]] & [[National Research Universal Reactor|NRU]] || Canada ||MTR (Pin Assemblies)|| <span style="display:none;">020000</span> 20MW; 200MW ([[National Research Universal Reactor#History|see]]) || Th+{{SimpleNuclide2|Uranium|235}}, Test Fuel || 1947 (NRX) + 1957 (NRU); Irradiation–testing of few fuel elements
| |
| |-
| |
| | [[CIRUS]]; [[Dhruva reactor|DHRUVA]]; & [[KAMINI]] || India || MTR Thermal || <span style="display:none;">040000</span> 40 MWt; 100 MWt; 30 kWt (low power, research) || Al+{{SimpleNuclide2|Uranium|233}} Driver Fuel, ‘J’ rod of Th & ThO2, ‘J’ rod of ThO<sub>2</sub> || 1960-2010 (CIRUS); others in operation
| |
| |-
| |
| | [[Kakrapar Atomic Power Station|KAPS 1 &2]]; KGS 1 & 2; [[Rajastan Atomic Power Project|RAPS 2, 3 & 4]] || India|| [[PHWR]], (Pin Assemblies) || <span style="display:none;">220000</span> 220 MW(e) || ThO<sub>2</sub> Pellets (For neutron flux flattening of initial core after start-up) || 1980 (RAPS 2) +; continuing in all new PHWRs
| |
| |-
| |
| | [[FBTR]] || India || [[Liquid metal fast reactor|LMFBR]], (Pin Assemblies) || <span style="display:none;">040000</span> 40 MWt || ThO<sub>2</sub> blanket || 1985; in operation
| |
| |}
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| | |
| ==See also==
| |
| * [[Radioactive waste]]
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| * [[World energy resources and consumption]]
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| * [[Peak uranium]]
| |
| * [[Fuji MSR]]
| |
| * [[Alvin Radkowsky]]
| |
| * [[Weinberg Foundation]]
| |
| * [[Flibe Energy]]
| |
| * [[CANDU reactor]]
| |
| * [[Advanced heavy water reactor]]
| |
| * [[Thorium Energy Alliance]]
| |
| | |
| ==References==
| |
| {{reflist|2}}
| |
| | |
| ==External links==
| |
| * [http://www.world-nuclear.org/info/inf62.html FactSheet on Thorium], [[World Nuclear Association]].
| |
| * [http://alsos.wlu.edu/qsearch.aspx?browse=science/Thorium Annotated bibliography for the thorium fuel cycle from the Alsos Digital Library for Nuclear Issues]
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| *[http://www.itheo.org/ International Thorium Energy Organisation - www.IThEO.org]
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| | |
| [[Category:Nuclear chemistry]]
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| [[Category:Nuclear fuels]]
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| [[Category:Nuclear reprocessing]]
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| [[Category:Nuclear technology]]
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| [[Category:Actinides]]
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| [[Category:Thorium]]
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