Thorium-based nuclear power generation is fueled primarily by the nuclear fission of the isotope uranium-233 produced from the fertile element thorium. According to proponents, a thorium fuel cycle offers several potential advantages over a uranium fuel cycle—including much greater abundance of thorium on Earth, superior physical and nuclear fuel properties, and reduced nuclear waste production. However, development of thorium power has significant start-up costs. Proponents also cite the lack of easy weaponization potential as an advantage of thorium, while critics say that development of breeder reactors in general (including thorium reactors, which are breeders by nature) increases proliferation concerns. As of 2019, there are no operational thorium reactors in the world.[ citation needed ]
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into 2 or more smaller, lighter nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay.
Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom.
Uranium-233 (233U) is a fissile isotope of uranium that is bred from thorium-232 as part of the thorium fuel cycle. Uranium-233 was investigated for use in nuclear weapons and as a reactor fuel. It has been used successfully in experimental nuclear reactors and has been proposed for much wider use as a nuclear fuel. It has a half-life of 160,000 years.
A nuclear reactor consumes certain specific fissile isotopes to produce energy. The three most common types of nuclear reactor fuel are:
Uranium-235 (235U) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a fission chain reaction. It is the only fissile isotope that is primordial and found in relatively significant quantities in nature.
Enriched uranium is a type of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99.284% 238U isotope, with 235U only constituting about 0.711% of its mass. 235U is the only nuclide existing in nature that is fissile with thermal neutrons.
Uranium-238 is the most common isotope of uranium found in nature, with a relative abundance of 99%. Unlike uranium-235, it is non-fissile, which means it cannot sustain a chain reaction in a thermal-neutron reactor. However, it is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239. 238U cannot support a chain reaction because inelastic scattering reduces neutron energy below the range where fast fission of one or more next-generation nuclei is probable. Doppler broadening of 238U's neutron absorption resonances, increasing absorption as fuel temperature increases, is also an essential negative feedback mechanism for reactor control.
The concept of using thorium as a nuclear fuel was proposed in 1942 by Glenn T. Seaborg, John W. Gofman, and R. W. Stoughton when they started investigating macroscopic chemistry of protactinium, just after they discovered uranium-233, which itself is a daughter of protactinium after irradiation of thorium.
Protactinium is a chemical element with the symbol Pa and atomic number 91. It is a dense, silvery-gray actinide metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds in which protactinium is usually present in the oxidation state +5, but it can also assume +4 and even +3 or +2 states. Concentrations of protactinium in the Earth's crust are typically a few parts per trillion, but may reach up to a few parts per million in some uraninite ore deposits. Because of its scarcity, high radioactivity and high toxicity, there are currently no uses for protactinium outside scientific research, and for this purpose, protactinium is mostly extracted from spent nuclear fuel.
Some believe thorium is key to developing a new generation of cleaner, safer nuclear power.According to a 2011 opinion piece by a group of scientists at the Georgia Institute of Technology, considering its overall potential, thorium-based power "can mean a 1000+ year solution or a quality low-carbon bridge to truly sustainable energy sources solving a huge portion of mankind’s negative environmental impact."
After studying the feasibility of using thorium, nuclear scientists Ralph W. Moir and Edward Teller suggested that thorium nuclear research should be restarted after a three-decade shutdown and that a small prototype plant should be built.
Edward Teller was a Hungarian-American theoretical physicist who is known colloquially as "the father of the hydrogen bomb", although he did not care for the title, and was only part of a team who developed the technology. Throughout his life, Teller was known both for his scientific ability and for his difficult interpersonal relations and volatile personality.
After World War II, uranium-based nuclear reactors were built to produce electricity. These were similar to the reactor designs that produced material for nuclear weapons. During that period, the government of the United States also built an experimental molten salt reactor using U-233 fuel, the fissile material created by bombarding thorium with neutrons. The MSRE reactor, built at Oak Ridge National Laboratory, operated critical for roughly 15,000 hours from 1965 to 1969. In 1968, Nobel laureate and discoverer of plutonium, Glenn Seaborg, publicly announced to the Atomic Energy Commission, of which he was chairman, that the thorium-based reactor had been successfully developed and tested.
In 1973, however, the US government settled on uranium technology and largely discontinued thorium-related nuclear research. The reasons were that uranium-fueled reactors were more efficient, the research was proven, and thorium's breeding ratio was thought insufficient to produce enough fuel to support development of a commercial nuclear industry. As Moir and Teller later wrote, "The competition came down to a liquid metal fast breeder reactor (LMFBR) on the uranium-plutonium cycle and a thermal reactor on the thorium-233U cycle, the molten salt breeder reactor. The LMFBR had a larger breeding rate ... and won the competition." In their opinion, the decision to stop development of thorium reactors, at least as a backup option, “was an excusable mistake.”
Science writer Richard Martin states that nuclear physicist Alvin Weinberg, who was director at Oak Ridge and primarily responsible for the new reactor, lost his job as director because he championed development of the safer thorium reactors.Weinberg himself recalls this period:
[Congressman] Chet Holifield was clearly exasperated with me, and he finally blurted out, "Alvin, if you are concerned about the safety of reactors, then I think it may be time for you to leave nuclear energy." I was speechless. But it was apparent to me that my style, my attitude, and my perception of the future were no longer in tune with the powers within the AEC.
Martin explains that Weinberg's unwillingness to sacrifice potentially safe nuclear power for the benefit of military uses forced him to retire:
Weinberg realized that you could use thorium in an entirely new kind of reactor, one that would have zero risk of meltdown. ... his team built a working reactor .... and he spent the rest of his 18-year tenure trying to make thorium the heart of the nation’s atomic power effort. He failed. Uranium reactors had already been established, and Hyman Rickover, de facto head of the US nuclear program, wanted the plutonium from uranium-powered nuclear plants to make bombs. Increasingly shunted aside, Weinberg was finally forced out in 1973.
Despite the documented history of thorium nuclear power, many of today’s nuclear experts were nonetheless unaware of it. According to Chemical & Engineering News , "most people—including scientists—have hardly heard of the heavy-metal element and know little about it...," noting a comment by a conference attendee that "it's possible to have a Ph.D. in nuclear reactor technology and not know about thorium energy."Nuclear physicist Victor J. Stenger, for one, first learned of it in 2012:
It came as a surprise to me to learn recently that such an alternative has been available to us since World War II, but not pursued because it lacked weapons applications.
Others, including former NASA scientist and thorium expert Kirk Sorensen, agree that "thorium was the alternative path that was not taken … " 2 According to Sorensen, during a documentary interview, he states that if the US had not discontinued its research in 1974 it could have "probably achieved energy independence by around 2000.":
The World Nuclear Association explains some of the possible benefits
The thorium fuel cycle offers enormous energy security benefits in the long-term – due to its potential for being a self-sustaining fuel without the need for fast neutron reactors. It is therefore an important and potentially viable technology that seems able to contribute to building credible, long-term nuclear energy scenarios.
Moir and Teller agree, noting that the possible advantages of thorium include "utilization of an abundant fuel, inaccessibility of that fuel to terrorists or for diversion to weapons use, together with good economics and safety features … " 7Thorium is considered the "most abundant, most readily available, cleanest, and safest energy source on Earth," adds science writer Richard Martin. :
Summarizing some of the potential benefits, Martin offers his general opinion: "Thorium could provide a clean and effectively limitless source of power while allaying all public concern—weapons proliferation, radioactive pollution, toxic waste, and fuel that is both costly and complicated to process. 13 Moir and Teller estimated in 2004 that the cost for their recommended prototype would be "well under $1 billion with operation costs likely on the order of $100 million per year," and as a result a "large-scale nuclear power plan" usable by many countries could be set up within a decade.:
A report by the Bellona Foundation in 2013 concluded that the economics are quite speculative. Thorium nuclear reactors are unlikely to produce cheaper energy, but the management of spent fuel is likely to be cheaper than for uranium nuclear reactors.
Some experts note possible specific disadvantages of thorium nuclear power:
Research and development of thorium-based nuclear reactors, primarily the Liquid fluoride thorium reactor (LFTR), MSR design, has been or is now being done in the United States, United Kingdom, Germany, Brazil, India, China, France, the Czech Republic, Japan, Russia, Canada, Israel, and the Netherlands.Conferences with experts from as many as 32 countries are held, including one by the European Organization for Nuclear Research (CERN) in 2013, which focuses on thorium as an alternative nuclear technology without requiring production of nuclear waste. Recognized experts, such as Hans Blix, former head of the International Atomic Energy Agency, calls for expanded support of new nuclear power technology, and states, "the thorium option offers the world not only a new sustainable supply of fuel for nuclear power but also one that makes better use of the fuel's energy content."
CANDU reactors are capable of using thorium,and Thorium Power Canada has, in 2013, planned and proposed developing thorium power projects for Chile and Indonesia. The proposed 10 MW demonstration reactor in Chile could be used to power a 20 million litre/day desalination plant. All land and regulatory approvals are currently in process. Thorium Power Canada's proposal for the development of a 25 MW thorium reactor in Indonesia is a "demonstration power project" that could provide electrical power to the country’s power grid. In 2018, the New Brunswick Energy Solutions Corporation announced the participation of Moltex Energy in the nuclear research cluster that will work on research and development on small modular reactor technology.
At the 2011 annual conference of the Chinese Academy of Sciences, it was announced that "China has initiated a research and development project in thorium MSR technology." 157In addition, Dr. Jiang Mianheng, son of China's former leader Jiang Zemin, led a thorium delegation in non-disclosure talks at Oak Ridge National Laboratory, Tennessee, and by late 2013 China had officially partnered with Oak Ridge to aid China in its own development. The World Nuclear Association notes that the China Academy of Sciences in January 2011 announced its R&D program, "claiming to have the world's largest national effort on it, hoping to obtain full intellectual property rights on the technology." According to Martin, "China has made clear its intention to go it alone," adding that China already has a monopoly over most of the world's rare earth minerals. :
In March 2014, with their reliance on coal-fired power having become a major cause of their current "smog crisis," they reduced their original goal of creating a working reactor from 25 years down to 10. "In the past, the government was interested in nuclear power because of the energy shortage. Now they are more interested because of smog," said Professor Li Zhong, a scientist working on the project. "This is definitely a race," he added.
In early 2012, it was reported that China, using components produced by the West and Russia, planned to build two prototype thorium MSRs by 2015, and had budgeted the project at $400 million and requiring 400 workers."China also finalized an agreement with a Canadian nuclear technology company to develop improved CANDU reactors using thorium and uranium as a fuel.
Currently two reactors are under construction in the Gobi desert, with completion expected in 2020. China expects to put thorium reactors into commercial use by 2030.
The German THTR-300 was a prototype commercial power station using thorium as fertile and highly enriched U-235 as fissile fuel. Though named thorium high temperature reactor, mostly U-235 was fissioned. The THTR-300 was a helium-cooled high-temperature reactor with a pebble-bed reactor core consisting of approximately 670,000 spherical fuel compacts each 6 centimetres (2.4 in) in diameter with particles of uranium-235 and thorium-232 fuel embedded in a graphite matrix. It fed power to Germany's grid for 432 days in the late 1980s, before it was shut down for cost, mechanical and other reasons.
India has one of the largest supplies of thorium in the world, with comparatively poor quantities of uranium. India has projected meeting as much as 30% of its electrical demands through thorium by 2050.
In February 2014, Bhabha Atomic Research Centre (BARC), in Mumbai, India, presented their latest design for a "next-generation nuclear reactor" that burns thorium as its fuel ore, calling it the Advanced Heavy Water Reactor (AWHR). They estimated the reactor could function without an operator for 120 days.Validation of its core reactor physics was underway by late 2017.
According to Dr R K Sinha, chairman of their Atomic Energy Commission, "This will reduce our dependence on fossil fuels, mostly imported, and will be a major contribution to global efforts to combat climate change." Because of its inherent safety, they expect that similar designs could be set up "within" populated cities, like Mumbai or Delhi.
India's government is also developing up to 62, mostly thorium reactors, which it expects to be operational by 2025. It is the "only country in the world with a detailed, funded, government-approved plan" to focus on thorium-based nuclear power. The country currently gets under 2% of its electricity from nuclear power, with the rest coming from coal (60%), hydroelectricity (16%), other renewable sources (12%) and natural gas (9%).It expects to produce around 25% of its electricity from nuclear power. In 2009 the chairman of the Indian Atomic Energy Commission said that India has a "long-term objective goal of becoming energy-independent based on its vast thorium resources."
In late June 2012, India announced that their "first commercial fast reactor" was near completion making India the most advanced country in thorium research. "We have huge reserves of thorium. The challenge is to develop technology for converting this to fissile material," stated their former Chairman of India's Atomic Energy Commission.That vision of using thorium in place of uranium was set out in the 1950s by physicist Homi Bhabha. India's first commercial fast breeder reactor—the 500 MWe Prototype Fast Breeder Reactor (PFBR)—is approaching completion at the Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu.
As of July 2013 the major equipment of the PFBR had been erected and the loading of "dummy" fuels in peripheral locations was in progress. The reactor was expected to go critical by September 2014.The Centre had sanctioned Rs. 5,677 crore for building the PFBR and “we will definitely build the reactor within that amount,” Mr. Kumar asserted. The original cost of the project was Rs. 3,492 crore, revised to Rs. 5,677 crore. Electricity generated from the PFBR would be sold to the State Electricity Boards at Rs. 4.44 a unit. BHAVINI builds breeder reactors in India.
In 2013 India's 300 MWe AHWR (pressurized heavy water reactor) was slated to be built at an undisclosed location.The design envisages a start up with reactor grade plutonium that breeds U-233 from Th-232. Thereafter, thorium is to be the only fuel. As of 2017, the design was in the final stages of validation.
Delays have since postponed the commissioning [criticality?] of the PFBR to Sept 2016,but India's commitment to long-term nuclear energy production is underscored by the approval in 2015 of ten new sites for reactors of unspecified types, though procurement of primary fissile material—preferably plutonium—may be problematic due to India's low uranium reserves and capacity for production.
In May 2010, researchers from Ben-Gurion University of the Negev in Israel and Brookhaven National Laboratory in New York began to collaborate on the development of thorium reactors,aimed at being self-sustaining, "meaning one that will produce and consume about the same amounts of fuel," which is not possible with uranium in a light water reactor.
In June 2012, Japan utility Chubu Electric Power wrote that they regard thorium as "one of future possible energy resources."
In late 2012, Norway's privately owned Thor Energy, in collaboration with the government and Westinghouse, announced a four-year trial using thorium in an existing nuclear reactor."In 2013, Aker Solutions purchased patents from Nobel Prize winning physicist Carlo Rubbia for the design of a proton accelerator-based thorium nuclear power plant.
In Britain, one organisation promoting or examining research on thorium-based nuclear plants is The Alvin Weinberg Foundation. House of Lords member Bryony Worthington is promoting thorium, calling it “the forgotten fuel” that could alter Britain’s energy plans.However, in 2010, the UK’s National Nuclear Laboratory (NNL) concluded that for the short to medium term, "...the thorium fuel cycle does not currently have a role to play," in that it is "technically immature, and would require a significant financial investment and risk without clear benefits," and concluded that the benefits have been "overstated." Friends of the Earth UK considers research into it as "useful" as a fallback option.
In its January 2012 report to the United States Secretary of Energy, the Blue Ribbon Commission on America's Future notes that a "molten-salt reactor using thorium [has] also been proposed."That same month it was reported that the US Department of Energy is "quietly collaborating with China" on thorium-based nuclear power designs using an MSR.
Some experts and politicians want thorium to be "the pillar of the U.S. nuclear future."Senators Harry Reid and Orrin Hatch have supported using $250 million in federal research funds to revive ORNL research. In 2009, Congressman Joe Sestak unsuccessfully attempted to secure funding for research and development of a destroyer-sized reactor [reactor of a size to power a destroyer] using thorium-based liquid fuel.
Alvin Radkowsky, chief designer of the world’s second full-scale atomic electric power plant in Shippingport, Pennsylvania, founded a joint US and Russian project in 1997 to create a thorium-based reactor, considered a "creative breakthrough."In 1992, while a resident professor in Tel Aviv, Israel, he founded the US company, Thorium Power Ltd., near Washington, D.C., to build thorium reactors.
The primary fuel of the proposed HT3R research project near Odessa, Texas, United States, will be ceramic-coated thorium beads. The earliest the reactor would become operational was 2015. [ needs update ]
On the research potential of thorium-based nuclear power, Richard L. Garwin, winner of the Presidential Medal of Freedom, and Georges Charpak advise further study of the Energy amplifier in their book Megawatts and Megatons (2001), pp. 153–163.
Thorium is mostly found with the rare earth phosphate mineral, monazite, which contains up to about 12% thorium phosphate, but 6–7% on average. World monazite resources are estimated to be about 12 million tons, two-thirds of which are in heavy mineral sands deposits on the south and east coasts of India. There are substantial deposits in several other countries (see table "World thorium reserves").Monazite is a good source of REEs (Rare Earth Element), but monazites are currently not economical to produce because the radioactive thorium that is produced as a byproduct would have to be stored indefinitely. However, if thorium-based power plants were adopted on a large-scale, virtually all the world's thorium requirements could be supplied simply by refining monazites for their more valuable REEs.
Another estimate of reasonably assured reserves (RAR) and estimated additional reserves (EAR) of thorium comes from OECD/NEA, Nuclear Energy, "Trends in Nuclear Fuel Cycle", Paris, France (2001).(see table "IAEA Estimates in tons")
|Country||RAR Th||EAR Th|
The preceding figures are reserves and as such refer to the amount of thorium in high-concentration deposits inventoried so far and estimated to be extractable at current market prices; millions of times more total exist in Earth's 3×1019 tonne crust, around 120 trillion tons of thorium, and lesser but vast quantities of thorium exist at intermediate concentrations. Proved reserves are a good indicator of the total future supply of a mineral resource.
According to the World Nuclear Association, there are seven types of reactors that can be designed to use thorium as a nuclear fuel. Six of these have all entered into operational service at some point. The seventh is still conceptual, although currently in development by many countries:
A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a self-sustained nuclear chain reaction. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat from nuclear fission is passed to a working fluid, which in turn runs through steam turbines. These either drive a ship's propellers or turn electrical generators' shafts. Nuclear generated steam in principle can be used for industrial process heat or for district heating. Some reactors are used to produce isotopes for medical and industrial use, or for production of weapons-grade plutonium. As of early 2019, the IAEA reports there are 454 nuclear power reactors and 226 nuclear research reactors in operation around the world.
The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end, which are the preparation of the fuel, steps in the service period in which the fuel is used during reactor operation, and steps in the back end, which are necessary to safely manage, contain, and either reprocess or dispose of spent nuclear fuel. If spent fuel is not reprocessed, the fuel cycle is referred to as an open fuel cycle ; if the spent fuel is reprocessed, it is referred to as a closed fuel cycle.
A breeder reactor is a nuclear reactor that generates more fissile material than it consumes. Breeder reactors achieve this because their neutron economy is high enough to create more fissile fuel than they use, by irradiation of a fertile material, such as uranium-238 or thorium-232 that is loaded into the reactor along with fissile fuel. Breeders were at first found attractive because they made more complete use of uranium fuel than light water reactors, but interest declined after the 1960s as more uranium reserves were found, and new methods of uranium enrichment reduced fuel costs.
A fast-neutron reactor (FNR) or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons, as opposed to thermal neutrons used in thermal-neutron reactors. Such a reactor needs no neutron moderator, but requires fuel that is relatively rich in fissile material when compared to that required for a thermal-neutron reactor.
A molten salt reactor (MSR) is a class of nuclear fission reactor in which the primary nuclear reactor coolant and/or the fuel is a molten salt mixture. MSRs offer multiple advantages over conventional nuclear power plants, although for historical reasons, they have not been deployed.
Nuclear fuel is material used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission.
Indira Gandhi Centre for Atomic Research(IGCAR) is one of India's premier nuclear research centres. It is the second largest establishment of the Department of Atomic Energy (DAE), next to Bhabha Atomic Research Centre (BARC), located at Kalpakkam, 80 km south of Chennai, India. It was established in 1971 as an exclusive centre dedicated to the pursuit of fast reactor science and technology, due to the vision of Dr. Vikram Sarabhai. Originally, it was called as Reactor Research Centre (RRC). It was renamed as Indira Gandhi Centre for Atomic Research(IGCAR) by the then Prime Minister of India, Rajiv Gandhi in December 1985. The centre is engaged in broad-based multidisciplinary programme of scientific research and advanced engineering directed towards the development of Fast Breeder Reactor technology, in India.
Generation IV reactors are a set of nuclear reactor designs currently being researched for commercial applications by the Generation IV International Forum, with technology readiness levels varying between the level requiring a demonstration, to economical competitive implementation. They are motivated by a variety of goals including improved safety, sustainability, efficiency, and cost.
The thorium fuel cycle is a nuclear fuel cycle that uses an isotope of thorium, 232
, as the fertile material. In the reactor, 232
is transmuted into the fissile artificial uranium isotope 233
which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts of fissile material, which are insufficient to initiate a nuclear chain reaction. Additional fissile material or another neutron source is necessary to initiate the fuel cycle. In a thorium-fuelled reactor, 232
absorbs neutrons to produce 233
. This parallels the process in uranium breeder reactors whereby fertile 238
absorbs neutrons to form fissile 239
. Depending on the design of the reactor and fuel cycle, the generated 233
either fissions in situ or is chemically separated from the used nuclear fuel and formed into new nuclear fuel.
The advanced heavy-water reactor (AHWR) is the latest Indian design for a next-generation nuclear reactor that burns thorium in its fuel core. It is slated to form the third stage in India's three-stage fuel-cycle plan. This phase of the fuel cycle plan is supposed to be built starting with a 300MWe prototype in 2016. As of 2018 construction has not started and a firm date has not be set.
The Fast Breeder Test Reactor (FBTR) is a breeder reactor located at Kalpakkam, India. The Indira Gandhi Center for Atomic Research (IGCAR) and Bhabha Atomic Research Centre (BARC) jointly designed, constructed, and operate the reactor.
The Molten-Salt Reactor Experiment (MSRE) was an experimental molten salt reactor at the Oak Ridge National Laboratory (ORNL) researching this technology through the 1960s; constructed by 1964, it went critical in 1965 and was operated until 1969.
Peak uranium is the point in time that the maximum global uranium production rate is reached. After that peak, according to Hubbert peak theory, the rate of production enters a terminal decline. While uranium is used in nuclear weapons, its primary use is for energy generation via nuclear fission of the uranium-235 isotope in a nuclear power reactor. Each kilogram of uranium-235 fissioned releases the energy equivalent of millions of times its mass in chemical reactants, as much energy as 2700 tons of coal, but uranium-235 is only 0.7% of the mass of natural uranium. Uranium-235 is a finite non-renewable resource. There is speculation that future advances in breeder reactor technology could allow the current reserves of uranium to provide power for humanity for billions of years, thus making nuclear power a sustainable energy. However, in 2010 the International Panel on Fissile Materials said "After six decades and the expenditure of the equivalent of tens of billions of dollars, the promise of breeder reactors remains largely unfulfilled and efforts to commercialize them have been steadily cut back in most countries." But in 2016, the Russian BN-800 fast-neutron breeder reactor started producing commercially at full power.
The liquid fluoride thorium reactor is a type of molten salt reactor. LFTRs use the thorium fuel cycle with a fluoride-based, molten, liquid salt for fuel. In a typical design, the liquid is pumped between a critical core and an external heat exchanger where the heat is transferred to a nonradioactive secondary salt. The secondary salt then transfers its heat to a steam turbine or closed-cycle gas turbine.
A traveling-wave reactor (TWR) is a proposed type of nuclear fission reactor that can convert fertile material into usable fuel through nuclear transmutation, in tandem with the burnup of fissile material. TWRs differ from other kinds of fast-neutron and breeder reactors in their ability to use fuel efficiently without uranium enrichment or reprocessing, instead directly using depleted uranium, natural uranium, thorium, spent fuel removed from light water reactors, or some combination of these materials. The concept is still in the development stage and no TWRs have ever been built.
India's three-stage nuclear power programme was formulated by Homi Bhabha in the 1950s to secure the country's long term energy independence, through the use of uranium and thorium reserves found in the monazite sands of coastal regions of South India. The ultimate focus of the programme is on enabling the thorium reserves of India to be utilised in meeting the country's energy requirements. Thorium is particularly attractive for India, as it has only around 1–2% of the global uranium reserves, but one of the largest shares of global thorium reserves at about 25% of the world's known thorium reserves. However, thorium is more difficult to use than uranium as a fuel because it requires breeding, and global uranium prices remain low enough that breeding is not cost effective.
The FUJI molten salt reactor is a proposed molten-salt-fueled thorium fuel cycle thermal breeder reactor, using technology similar to the Oak Ridge National Laboratory's Molten Salt Reactor Experiment – liquid fluoride thorium reactor. It was being developed by the Japanese company International Thorium Energy & Molten-Salt Technology (IThEMS), together with partners from the Czech Republic. As a breeder reactor, it converts thorium into the nuclear fuel uranium-233. To achieve reasonable neutron economy, the chosen single-salt design results in significantly larger feasible size than a two-salt reactor. Like all molten salt reactors, its core is chemically inert and under low pressure, helping to prevent explosions and toxic releases. The proposed design is rated at 200 MWe output. The IThEMS consortium planned to first build a much smaller MiniFUJI 10 MWe reactor of the same design once it had secured an additional $300 million in funding.
Thorium Energy Alliance (TEA) is a non-governmental, non-profit 501(c)3, educational organization based in the United States, which seeks to promote energy security of the world through the use of thorium as a fuel source. The potential for the use of thorium was studied extensively during the 1950s and 60s, and now worldwide interest is being revived due to limitations and issues concerning safety, economics, use and issues in the availability of other energy sources. TEA advocates thorium based nuclear power in existing reactors and primarily in next generation reactors. TEA promotes many initiatives to educate scientists, engineers, government officials, policymakers and the general public.
The dual fluid reactor (DFR) is a reactor concept of a private German research institute, the Institute for Solid-State Nuclear Physics. Combining the advantages of the molten salt reactor with those of the liquid metal cooled reactor, it is supposed to reach the criteria for reactors of the Generation IV International Forum. The fuel is a molten solution of actinide chloride salts, while the cooling is provided by molten lead in a separate loop. As a fast breeder reactor, the DFR can use both natural uranium and thorium to breed fissile material, as well as recycle High-level waste and plutonium. Due to the high thermal conductivity of the molten metal, the DFR is an inherently safe reactor.