Thorium doesn’t solve – multiple reasons

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Thorium doesn’t solve – multiple reasons

Rees, 11 – Reporter for the Ecologist (Eifion, “Don't believe the spin on thorium being a ‘greener’ nuclear option,” Ecologist, June 23,

And yet the nuclear industry itself is also sceptical, with none of the big players backing what should be – in PR terms and in a post-Fukushima world – its radioactive holy grail: safe reactors producing more energy for less and cheaper fuel.

 In fact, a 2010 National Nuclear Laboratory (NNL) report concluded the thorium fuel cycle ‘does not currently have a role to play in the UK context [and] is likely to have only a limited role internationally for some years ahead’ – in short, it concluded, the claims for thorium were ‘overstated’. Proponents counter that the NNL paper fails to address the question of MSR technology, evidence of its bias towards an industry wedded to PWRs. Reliant on diverse uranium/plutonium revenue streams – fuel packages and fuel reprocessing, for example – the nuclear energy giants will never give thorium a fair hearing, they say. But even were its commercial viability established, given 2010’s soaring greenhouse gas levels, thorium is one magic bullet that is years off target. Those who support renewables say they will have come so far in cost and efficiency terms by the time the technology is perfected and upscaled that thorium reactors will already be uneconomic. Indeed, if renewables had a fraction of nuclear’s current subsidies they could already be light years ahead. 

 Extra radioactive waste All other issues aside, thorium is still nuclear energy, say environmentalists, its reactors disgorging the same toxic byproducts and fissile waste with the same millennial half-lives. Oliver Tickell, author of Kyoto2, says the fission materials produced from thorium are of a different spectrum to those from uranium-235, but ‘include many dangerous-to-health alpha and beta emitters’. Tickell says thorium reactors would not reduce the volume of waste from uranium reactors. ‘It will create a whole new volume of radioactive waste, on top of the waste from uranium reactors. Looked at in these terms, it’s a way of multiplying the volume of radioactive waste humanity can create several times over.’ Putative waste benefits – such as the impressive claims made by former Nasa scientist Kirk Sorensen, one of thorium’s staunchest advocates – have the potential to be outweighed by a proliferating number of MSRs. There are already 442 traditional reactors already in operation globally, according to the International Atomic Energy Agency. The by-products of thousands of smaller, ostensibly less wasteful reactors would soon add up. Anti-nuclear campaigner Peter Karamoskos goes further, dismissing a ‘dishonest fantasy’ perpetuated by the pro-nuclear lobby. Thorium cannot in itself power a reactor; unlike natural uranium, it does not contain enough fissile material to initiate a nuclear chain reaction. As a result it must first be bombarded with neutrons to produce the highly radioactive isotope uranium-233 – ‘so these are really U-233 reactors,’ says Karamoskos. This isotope is more hazardous than the U-235 used in conventional reactors, he adds, because it produces U-232 as a side effect (half life: 160,000 years), on top of familiar fission by-products such as technetium-99 (half life: up to 300,000 years) and iodine-129 (half life: 15.7 million years).

Add in actinides such as protactinium-231 (half life: 33,000 years) and it soon becomes apparent that thorium’s superficial cleanliness will still depend on digging some pretty deep holes to bury the highly radioactive waste. Thorium for the UK? With billions of pounds already spent on nuclear research, reactor construction and decommissioning costs – dwarfing commitments to renewables – and proposed reform of the UK electricity markets apparently hiding subsidies to the nuclear industry, the thorium dream is considered by many to be a dangerous diversion. Energy consultant and former Friends of the Earth anti-nuclear campaigner Neil Crumpton says the government would be better deferring all decisions about its new nuclear building plans and fuel reprocessing until the early 2020s: ‘By that time much more will be known about Generation IV technologies including LFTRs and their waste-consuming capability.’ In the meantime, says Jean McSorley, senior consultant for Greenpeace’s nuclear campaign, the pressing issue is to reduce energy demand and implement a major renewables programme in the UK and internationally – after all, even conventional nuclear reactors will not deliver what the world needs in terms of safe, affordable electricity, let alone a whole raft of new ones. ‘Even if thorium technology does progress to the point where it might be commercially viable, it will face the same problems as conventional nuclear: it is not renewable or sustainable and cannot effectively connect to smart grids. The technology is not tried and tested, and none of the main players is interested. Thorium reactors are no more than a distraction.’

Thorium is hype – no support

Rees, 11 – Reporter for the Ecologist (Eifion, “Don't believe the spin on thorium being a ‘greener’ nuclear option,” Ecologist, June 23,

The pro-thorium lobby claim a single tonne of thorium burned in a molten salt reactor (MSR) – typically a liquid fluoride thorium reactor (LFTR) – which has liquid rather than solid fuel, can produce one gigawatt of electricity. A traditional pressurised water reactor (PWR) would need to burn 250 tonnes of uranium to produce the same amount of energy. They also produce less waste, have no weapons-grade by-products, can consume legacy plutonium stockpiles and are meltdown-proof – if the hype is to be believed.

 Global support for thorium India certainly has faith, with a burgeoning population, chronic electricity shortage, few friends on the global nuclear stage (it hasn’t signed the nuclear non-proliferation treaty) and the world’s largest reserves of thorium. ‘Green’ nuclear could help defuse opposition at home (the approval of two new traditional nuclear power reactors on its west coast led to fierce protests recently) and allow it to push ahead unhindered with its stated aim of generating 270GW of electricity from nuclear by 2050. China, Russia, France and the US are also pursuing the technology, while India’s department of atomic energy and the UK’s Engineering and Physical Sciences Research Council are jointly funding five UK research programmes into it. There is a significant sticking point to the promotion of thorium as the ‘great green hope’ of clean energy production: it remains unproven on a commercial scale. While it has been around since the 1950s (and an experimental 10MW LFTR did run for five years during the 1960s at Oak Ridge National Laboratory in the US, though using uranium and plutonium as fuel) it is still a next generation nuclear technology – theoretical. China did announce this year that it intended to develop a thorium MSR, but nuclear radiologist Peter Karamoskos, of the International Campaign to Abolish Nuclear Weapons (ICAN), says the world shouldn’t hold its breath. ‘Without exception, [thorium reactors] have never been commercially viable, nor do any of the intended new designs even remotely seem to be viable. Like all nuclear power production they rely on extensive taxpayer subsidies; the only difference is that with thorium and other breeder reactors these are of an order of magnitude greater, which is why no government has ever continued their funding.’ China’s development will persist until it experiences the ongoing major technical hurdles the rest of the nuclear club have discovered, he says. Others see thorium as a smokescreen to perpetuate the status quo: the closest the world has come to an operating thorium reactor is India’s Kakrapar-1, a uranium-fuelled PWR that was the first to use thorium to flatten power across the core. 

‘This could be seen to excuse the continued use of PWRs until thorium is [widely] available,’ points out Peter Rowberry of No Money for Nuclear (NM4N) and Communities Against Nuclear Expansion (CANE). In his reading, thorium is merely a way of deflecting attention and criticism from the dangers of the uranium fuel cycle and excusing the pumping of more money into the industry. Why is the nuclear lobby so quiet?

 And yet the nuclear industry itself is also sceptical, with none of the big players backing what should be – in PR terms and in a post-Fukushima world – its radioactive holy grail: safe reactors producing more energy for less and cheaper fuel.

 In fact, a 2010 National Nuclear Laboratory (NNL) report concluded the thorium fuel cycle ‘does not currently have a role to play in the UK context [and] is likely to have only a limited role internationally for some years ahead’ – in short, it concluded, the claims for thorium were ‘overstated’.

Thorium has multiple challenges – radiation and safety

Williams, 7/13 – a Hong Kong-based writer specialising in conservation and the environment, with a PhD in physical chemistry from Cambridge University (Martin, “Scientists including in China study thorium-fuelled nuclear power,” South China Morning Post, 2014,

Reading this, you might think, "Great - let's get started! We can solve the world's energy problems, stabilise the climate, and move on to eliminating poverty and finding a cure for cancer." But there are challenges to overcome, and no one yet knows if these will prove insurmountable. Issues include the process involving isotopes that could be used in nuclear bombs, such as the plutonium or enriched uranium required to convert the thorium and get the reactor started. Also, there will be dangerously radioactive products, requiring safe storage for perhaps tens of thousands of years. There's as yet no agreement regarding the best technology for managing the process, without radioactive and chemically reactive substances plus heat causing damaging to containment vessels. Costs could be prohibitive. Yet with advantages including thorium being about as abundant as lead, plus severe difficulties for making a nuclear bomb from a thorium reactor - partly as it will include the dangerous and easily detectable U-232 uranium isotope, several projects are under way around the world, involving both theoretical and practical work. India is aiming to build thorium-based reactors, favouring designs akin to typical nuclear plants, with solid fuel plus heavy water - which has deuterium rather than hydrogen atoms. A Norwegian project is pioneering use of thorium in a light-water reactor. But the main excitement around thorium centres on the possibility of using salt mixtures with thorium fluoride plus other chemicals, which can become molten during operation. Advantages over reactors utilising water would include higher efficiency as temperatures could be around 800 degrees Celsius, and running at close to atmospheric pressure. Pioneering work on molten-salt reactors was conducted at the US Oak Ridge National Laboratory. Rather than include thorium as envisaged for working reactors, experiments were conducted with uranium isotopes. Though some issues arose, the five-year trial was a success, achieving all objectives. Laboratory director Alvin Weinberg - who had studied the absorption spectrum of carbon dioxide for his master's thesis - warned about the burning of fossil fuels leading to climate change, and believed there could be a solution in nuclear power, particularly using thorium. He was also concerned about safety, which evidently helped lead to him being fired - six years after which came the partial meltdown at Three Mile Island, Pennsylvania. With the US government wanting nuclear reactors that could create plutonium for making bombs, attention shifted away from thorium and molten-salt reactors. These reactors were little known, and thorium became akin to a forgotten fuel, until the recent resurgence of interest. This has been spurred partly by the Weinberg Foundation, which was established in 2011 and is "dedicated to driving awareness, research and the commercialisation of cleaner and safer nuclear technologies, fuelled by thorium". Last month, the foundation reported that a study of the feasibility of a pilot-scale molten-salt reactor had won funding from the British government's strategic innovation agency, the Technology Strategy Board. But never mind shilly-shallying with computer studies and the like, China is leaping into action with an intensive programme to create thorium-powered molten-salt reactors. In March, the South China Morning Post reported that, propelled by the "war on pollution", the Shanghai-based project team had their time frame for achieving this goal shortened from 25 to 10 years. The US Department of Energy - especially its Oak Ridge laboratory - is said to be "quietly collaborating" on the project, and we can only guess at the frustration some of its scientists may feel given previous work was abandoned by a government blinded by desire to build bombs. I've seen the China project described as akin to a nuclear "moon shot". It's indeed ambitious, and may fail. Yet we need something monumental to stave off calamitous climate change, and thorium may yet help us realise Alvin Weinberg's vision of the "Second Nuclear Era". If so - if! - we in Hong Kong may yet experience a stable climate and, whisper it, smog-free skies year-around.

Thorium reactors are dangerous – weaponization and prolif

Touran, 3/22 – PhD in Nuclear Engineering, BSE and MSE in nuclear engineering, and working as a reactor physicist on the design of an advanced nuclear reactor for a nuclear innovation company since 2009 (Nick, “Myths about Thorium nuclear fuel,” What is Nuclear? 2014,

Dear Internet, we need to have a talk about Thorium. It has many good attributes as a nuclear fuel, but the things being said on the internet have become largely misleading, if not all-out inaccurate. Every internet person I meet in real life who finds out that I am a nuclear engineer asks me why we aren’t using the end-all, be-all that is thorium. Every post regarding nuclear energy on reddit is packed full of comments claiming that Thorium will end all concerns about nuclear energy and that Uranium is only in use due to some dark dark conspiracy. Example: "So why did they go down the Uranium path? Because it was the military running the program, and Thorium reactors aren’t weaponizable." Misleading and half false! Yes, Uranium fuel was certainly developed because it was the easist path to weapons at the time, but these days, the owner of a thorium reactor could certainly make a bomb from it. So they are weaponizable. The internet has become an echo-chamber for this kind of thing and we need to stop it. This page will try to point people in the right direction if they get lost, using things like references and whatnot. And we’ll make a wall of shame where anyone who perpetuates a myth will get to be displayed. To learn about Thorium for real, we feature a page about Thorium as nuclear fuel, as well as a big page about the fluid fueled molten salt reactors (MSRs) that are good at using it. If you think we’re too negative-nancy here, go check out those pages. We love Thorium and think it has a bright future, both in solid and fluid fueled reactors. I personally have studied it a huge amount and many years ago considered getting a THORIUM vanity plate. As we claim elsewhere and throughout comment posts abound, we just think that people need to remain calm and accurate when discussing its merits and demerits. Thorium Myth #1: Development of Thorium-based molten salt reactors got cancelled because they couldn’t make bombs! Quite False. Not only can they be used to make bombs (see Myth #3), but they also were not canceled for any weapons-related reason. One of the most lucid descriptions of what happened to molten salt reactors like the LFTR can be found on page 49 of WASH-1222 [1]. There, they describe a few privately-funded working group studies of the MSBR, including the Molten Salt Breeder Reactor Associates (consisting of the engineering firm Black & Veatch and five midwestern utilities) and the Molten Salt Group, headed by Ebasco Services, Inc. (with 5 other industrial firms and fifteen utilities involved). These groups concluded that the MSBR (basically the LFTR) is attractive and potentially cheaper than LWRs. They said that a demonstration plant is warranted, but the performance cannot be predicted with confidence. Then, a list of factors that limit industrial involvement is given. They include (verbatim): The existing major industrial and utility commitments to the LWR, HTGR, and LMFBR. The lack of incentive for industrial investment in supplying fuel cycle services, such as those required for solid fuel reactors. The overwhelming manufacturing and operating experience with solid fuel reactors in contrast with the very limited involvement with fluid fueled reactors. The less advanced state of MSBR technology and the lack of demonstrated solutions to the major technical problems associated with the MSBR concept. It had nothing to do with weapons. Weapons were produced with graphite or heavy-water moderated production reactors and with gas centrifuge enrichment. Oh, and thermonuclear weapons require tritium as well, which is something that many Thorium MSR designs excel in producing (darn that lithium!). The commercial LWRs had nothing to do with making bomb material. Stop the nonsense. Earlier history will point you to Rickover’s USS Nautilus, which acted as the engineering demonstration of the light water reactor. Since the Navy had already developed the LWR, the commercial industry was much more comfortable going with it and scaling it up. Thorium Myth #2: Thorium reactors never need enrichment! Misleading at best. The nice thing about any breeder reactor (using Th-U or U-Pu) is that eventually they can become fissile self-sufficient, meaning they breed more (or equal) fissile material than they consume. The first electricity-producing reactor in the world (EBR-I in Idaho, 1951) was created to demonstrate that breeding was possible (in a liquid-metal cooled fast breeder reactor, or LMFBR). Any breeder reactor concept on the planet can run without additional enrichment (or some other external source of fissile material) after their initial startup by breeding fissile material out of fertile material like Th-232 or U-238. But you have to start your reactor up with fissile material from somewhere. If you take a vat of Thorium and try to turn it on, you'll be sorely disappointed because it cannot possibly sustain a chain reaction, under any circumstances. So you start it up with denatured bombs or enriched U-235 and then it becomes self-sufficient on Th-232 or U-238. I occasionally read misleading things that say Thorium will just fire right up. Alas. It should be noted, however, that the key advantage of Th fuel is that it allows thermal breeding. This means that you can start up a Th-based breeder with substantially less fissile material than you need to start an equivalent-powered fast breeder reactor. Once started, the fast breeder will make far more fissile material (because they make have a better breeding neutron economy), but the amount of fissile in fast spectrum reactors is always more than in thermal reactors. TL;DR: They do to start up, and U-Pu breeders like the LMFBR can do the same so it’s not Thorium specific. Thorium Myth #3: Thorium reactors cannot make bombs! False! They can indeed make bombs. Thorium reactors work by breeding Th-232 through Protactinium-233 (27.4 day half life) and into Uranium-233, which is fissile. Pa-233 is a pretty strong neutron absorber, so the MSBR (basically the LFTR) has to extract it from the core once it is produced and let it decay to U-233 away from the neutrons. Once the U-233 is created, it gets fed back into the reactor. Well, if you went rogue, you could build up a little excess reactivity (maybe add some low-enriched U235?) and then divert the freshly-bred U-233 into a weapons stream to make U-233 nuclear bombs. It may be difficult to do this several times without going subcritical, but it certainly could be done. A U-233-filled bomb has been tested before, and it worked just fine. Here’s a quote from a Frank von Hippel paper on the subject [2]: "On the one hand, gamma radiation from U-232 makes the U-233 from high- burnup U-233-thorium fuel cycles more of a radiation hazard than plutonium. On the other hand, because of its low rate of spontaneous-neutron emission, U-233 can, unlike plutonium, be used in simple gun-type fission-weapon designs without significant danger of the yield being reduced by premature initiation of the fission chain reaction" And another (also [2]): "In the case of the molten-salt U-233 breeder reactor, it was proposed to have continual chemical processing of a stream of liquid fuel. Such an arrangement also offers a way to completely bypass the U-232 contamination problem because 27-day half-life Pa- 233 could be separated out before it decays into U-233." Options to make bomb-making less favorable include fostering substantial U-232 contamination in the reactor and denaturing the U-233 with U-238 that keeps the in-reactor inventory safe. Both of these options can conceptually be bypassed in the Pa separation route though. Besides, U-232 isn’t releasing the gammas, its decay products are, and it has a 70 year half-life. So you can just chemically purify your stolen goods and then make the bomb anytime within the next decade or so. There are about a dozen other ways people try to amp up the proliferation resistance of various fuel cycles. But they always forget that the owner of such a plant can secretly install a chemical cell that does Pa separation. Really, most civilian power to bombs proliferation paths are mythical, in any reactor! But since the consequences of proliferation are so dire, nuclear power plants need to have baseline proliferation safeguards in place. Thorium-powered reactors, whether fluid fueled or not, are no exception.

Thorium fails – it can be turned into a nuclear weapon and has multiple complications

Edwards, 13 – Ph.D., President at the Canadian Coalition for Nuclear Responsibility (Gordon, “Thorium Reactors and Nuclear Weapons Proliferation: “The Promise and Peril of Thorium”,” Pressenza Hong Kong, 2014,

Thorium is a naturally occurring radioactive element, but it is not a nuclear fuel, nor is it a nuclear explosive. The phrase “thorium fuel” is a misnomer. Thorium is not a fuel. However, when thorium is bombarded with neutrons, it is transmuted into a type of uranium that does not exist in nature: uranium-233. This manufactured material, U-233, can subsequently be used as a nuclear fuel or as a nuclear explosive. The article linked below is highly recommended. It provides a good discussion of the weapons proliferation risks associated with thorium-based nuclear reactor technologies. To better grasp the proliferation risk, some background on nuclear explosives is helpful. Background on Nuclear Weapons: All existing nuclear weapons use either uranium or plutonium as the primary nuclear explosive material. All nuclear fuels (fuels for nuclear reactors) are also based on either uranium or plutonium. The story begins with naturally occurring uranium…. A. Uranium-235 — Uranium Enrichment Uranium is the only naturally occurring material that can be utilized as a nuclear explosive. However, not all kinds of uranium can be used to make nuclear weapons. One cannnot use natural uranium (the stuff that is mined), or low-enriched uranium (the stuff that is used as fuel in most commercial power reactors around the world) as a nuclear explosive. The problem with these materials is that there is too much uranium-238 (which is NOT a nuclear explosive) and too little uranium-235 (which IS a nuclear explosive). Uranium enrichment is a technological process for increasing the concentration of uranium-235 by separating out and discarding much of the unwanted uranium-238. The end product of this separation process is called “enriched uranium” — uranium with a higher concentration of U-235 than that found in naturally occurring uranium. The discarded material — mostly uranium-238 — is called “depleted uranium” because it has even less uranium-235 per kilogram than is found in natural uranium ore deposits (0.7 percent). Technically, any type of uranium in which the concentration of uranium-235 is 20 percent or more is called Highly Enriched Uranium (HEU). HEU of any kind can be used as a nuclear explosive material, if available in sufficient quantity. Nuclear weapons designers prefer HEU that is more than 90 percent enriched — i.e. more than 90 percent U-235. Such HEU is called “weapons-grade uranium”. Any type of HEU is weapons-usable, even if it is not weapons-grade. Most commercial power reactors use only Low Enriched Uranium (LEU) as fuel; LEU cannot be used as a nuclear explosive due to the excessive amount of uranium-238 that it contains. It is a slow, difficult, time-consuming process to enrich uranium — but once weapons-grade uranium is produced, it is rather easy to make a powerful atomic bomb with it. All that is needed is a “gun-type” mechanism to bring two pieces of HEU together very rapidly, by firing a uranium “bullet” into a uranium “target”. The Hiroshima bomb was made in this fashion. The gun-type mechanism is so simple there is no need to test it. It was guaranteed to work the very first time it was tried. As indeed it did…. If weapons-grade uranium falls into criminal hands, the construction of a powerful atomic bomb is a relatively simple matter. No testing is needed. That is why the civilian use of HEU is being phased out — it’s just too dangerous to allow this material to remain in commercial circulation. B. Plutonium — Created from Uranium-238 Plutonium does not exist in nature; but it is created inside every reactor that uses natural uranium or low-enriched uranium as fuel. Some of the uranium-238 atoms in the fuel absorb stray neutrons, and those atoms are transmuted into plutonium atoms. It turns out that plutonium is a more powerful nuclear explosive than HEU. Plutonium is in fact more powerful than weapons-grade uranium. Obtaining plutonium involves a chemical extraction process that requires dissolving highly radioactive “used nuclear fuel” in boiling nitric acid — not an easy task! This makes it difficult to divert the plutonium from civilian nuclear reactors into bombs, unless the plutonium has already been extracted ahead of time. Once the plutonium has been separated from the rest of the radioactive garbage, it can be packaged and transported without detection fairly easily. Using plutonium as a nuclear explosive does require a more elaborate bomb mechanism than the “gun-type” uranium bomb design. A sophisticated “implosion mechanism” is needed. That requires the simultaneous detonation of shaped charges (conventional explosives) surrounding a perfectly spherical ball of plutonium. Such an implosion device is by no means simple; it requires painstaking engineering and careful testing. The Nagasaki bomb was made in this fashion. It was tested months ahead of time at Alamogordo, New Mexico. All reactor-produced plutonium is weapons-usable, but nuclear weapons designers prefer to use plutonium with a very high percentage of plutonium-239 and a low percentage of plutonium-240. Such material is called “weapons grade plutonium”. Although plutonium-240 is a nuclear explosive material, its presence complicates the job of the bomb-maker in two ways: (1) it makes the explosive material more difficult to handle because of higher levels of radio- activity and heat; (2) it makes the power of the nuclear explosion less predictable because it produces a lot of stray neutrons. Despite these complications, any type of plutonium can be used to make reliable, highly effective nuclear weapons at all levels of technical sophistication. See C. Uranium-233 — Created from Thorium-232 As previously remarked, naturally occurring thorium — thorium-232 — is the raw material from which a new kind of uranium — uranium-233 — can be created. All that’s needed is to bombard thorium-232 with neutrons. The easiest way to do that is to put the thorium inside a nuclear reactor, where neutrons are abundant. (Of course the reactor has to be fuelled by uranium or plutonium, otherwise there will be no neutrons.) When a thorium-232 atom absorbs a stray neutron it is transmuted into an atom of protactinium-233, which then spontaneously transmutes itself into an atom of uranium-233 — a type of uranium not found in nature. It turns out that uranium-233 is immediately weapons usable without the need for any kind of enrichment. It is a more powerful explosive than uranium-235, and — unlike plutonium — it can be used in a simple gun-type device, like the Hiroshima bomb. Thus uranium-233 avoids one of the complications posed by the use of uranium-235 (the need for enrich- ment) as well as one of the complications associated with plutonium (the need for an implosion mechanism). There is however another complication that arises. When thorium is placed inside a nuclear reactor, there is another type of uranium created called uranium-232. Although uranium-232 is also a nuclear explosive material, it is highly undesirable because it gives off an extremely powerful burst of gamma radiation — so powerful, in fact, that it can seriously damage electronic equipment. The more uranium-233 is contaminated with uranium-232 the more difficult it is to use it as a nuclear explosive. But, as the article cited above (see link) points out, it is relatively easy to avoid this contamination problem. All that is required is to chemically separate the protactinium-233 at an early stage, remove it from the reactor environment, and then simply wait until it has almost all changed into uranium-233. In this way a stockpile of weapons-grade uranium-233 can be produced that is uncontaminated with uranium-232 and virtually trouble-free for making any type of nuclear weapon, including gun-type A-bombs. The reason this works is due to the absence of neutrons outside the reactor environment. Uranium-232 is created only in the presence of neutrons, and outside the reactor there aren’t any neutrons — so no uranium-232 is being produced. But protactinium-233 becomes uranium-233 spontaneously, without any need for neutrons. So by separating the protactinium-233 from the rest of the irradiated thorium, the potential bomb-maker gets lots of uranium-233, and virtually no uranium-232.


Small-scale thorium reactors would make prolif easier—their ev gets the isotope math wrong

Helian, 10 – Technical contractor with a PhD in nuclear engineering (“Subcritical Thorium Reactors: Dr. Rubbia’s Really Bad Idea,” September 1, Helian Unbound,

In any case, the design he seems to be so excited about is Dr. Rubbia’s “energy amplifier,” which, as noted above, would be subcritical, requiring a powerful, high current proton accelerator to keep the fission process going. It would do this via spallation, a process in which a copious source of the neutrons required to keep the reaction going would be provided via interaction of the protons with heavy nuclei such as lead, or thorium itself. This is the process used to produce neutrons at the Oak Ridge Spallation Neutron Source. Such reactors could easily be “turned off” by simply shutting down the source of neutrons. However, the idea that they would be inherently “safer” is dangerously inaccurate. In fact, they would be an ideal path to covert acquisition of nuclear weapons. Thorium reactors work by transmuting thorium into U233, which is the isotope that fissions to produce the lion’s share of the energy. It is also an isotope that, like U235 and Pu239, can be used to make nuclear bombs. The article downplays this risk as follows: After the Manhattan Project, US physicists in the late 1940s were tempted by thorium for use in civil reactors. It has a higher neutron yield per neutron absorbed. It does not require isotope separation, a big cost saving. But by then America needed the plutonium residue from uranium to build bombs. “They were really going after the weapons,” said Professor Egil Lillestol, a world authority on the thorium fuel-cycle at CERN. “It is almost impossible make nuclear weapons out of thorium because it is too difficult to handle. It wouldn’t be worth trying.” It emits too many high (energy) gamma rays. What Lillestol is referring to is the fact that, in addition to U233, thorium reactors also produce a certain amount of U232, a highly radioactive isotope of uranium with a half life of 68.9 years whose decay does, indeed, release potentially deadly gamma rays. It would be extremely difficult, if not impossible, to remove it from the U233, and, if enough of it were present, it would certainly complicate the task of building a bomb. The key phrase here is “if enough of it were present.” Thorium enthusiasts like Lillestol never seem to do the math. In fact, as can be seen here, even conventional thorium breeders could be designed to produce U233 sufficiently free of U232 to allow workers to fabricate a weapon without serious danger of receiving a lethal dose of gamma rays. However, large concentrations of highly radioactive fission products would make it very difficult to surreptitiously extract the uranium, and it would also be possible to mix the fuel material with natural or depleted uranium, reducing the isotopic concentration of U233 below that necessary to make a bomb. With subcritical reactors of the type proposed by Rubbia, the problem of making a bomb gets a whole lot easier. Rogue state actors, and even terrorists groups if we “succeed” in coming up with a sufficiently inexpensive design for high energy proton accelerators, could easily modify them to produce virtually pure U233, operating small facilities that it would be next to impossible for international monitors to detect. There are two possible pathways for the production of U232 from thorium, both of which involve a reaction in which a neutron knocks two neutrons out of a heavy nucleus of Th232 or U233. Those reactions can’t occur unless the initial neutron is carrying a lot of energy as can be seen in figure 8 of the article linked above, the threshold is around 6 million electron volts (MeV). That means that, in order to produce virtually pure U233, all that’s necessary is to slow the incoming spallation neutrons below that energy. That’s easily done. Imagine two billiard balls on a table. If you hit one as hard as you can at the other one, what happens when they collide? If your aim was true, the first ball stops, transferring all its energy to the second one. The same thing can be done with neutrons. Pass the source neutrons through a layer of material full of light atoms such as paraffin or heavy water, and they will bounce off the light nuclei, losing energy in the process, until they eventually become “thermalized,” with virtually none of them having energies above 6 MeV. If such low energy neutrons were then passed on to a subcritical core, they would produce U233 with almost no U232 contamination. It gets worse. Unlike Pu239, U233 does not emit a lot of spontaneous neutrons. That means it can be used to make a simple gun-type nuclear weapon with little fear that a stray neutron will cause it to fizzle before optimum criticality is reached. And, by the way, a lot less of it would be needed than would be required for a similar weapon using U235, the fissile material in the bomb that destroyed Hiroshima. We’re quite capable of blowing ourselves up without Rubbia’s subcritical reactors. Let’s not make it any easier than it already is. Thorium reactors have many potential advantages over other potential sources of energy, including wind and solar. However, if we’re going to do thorium, let’s do it right. UPDATE: Steven Den Beste gets it right at Hot Air. His commenters throw out the usual red herrings about the US choosing U235 and Pu239 over U233 in the Manhattan Project (for good reasons that had nothing to do with U233′s suitability as a bomb material) and the grossly exaggerated and misunderstood problem with U232. You don’t have to be a nuclear engineer to see through these fallacious arguments. The relevant information is all out there on the web, it’s not classified, and it can be understood by any bright high school student who takes the time to get the facts.

Specifically, thorium requires reprocessing—causes prolif

Edwards, 11 – PhD and President at the Canadian Coalition for the Nuclear Responsibility (Gordon, “Thorium Reactors: Back to the Dream Factory: The Nuclear Dream Factory,” July 13, Forgotten People,

Thorium is not a nuclear fuel: The fundamental fact about thorium is that it is NOT a nuclear fuel, because thorium is not a fissile material, meaning that it cannot sustain a nuclear fission chain reaction. In fact the ONLY naturally occurring fissile material is uranium-235, and so — of necessity — that is the material that fuels all of the first-generation reactors in the entire world. Thorium cannot replace uranium-235 in this regard. Not at all. Thorium is a “fertile” material: But thorium-232, which is a naturally occurring radioactive material, is about three times as abundant as uranium-238, which is also a naturally occurring radioactive material. Neither of these materials can be used directly as a nuclear fuel, because they are not “fissile” materials. However, both uranium-238 and thorium-232 are “fertile” materials, which means that IF they are placed in the core of a nuclear reactor (one that is of necessity fuelled by a fissile material), some fraction of those fertile atoms will be transmuted into man-made fissile atoms. Some uranium-238 atoms get transmuted into plutonium-239 atoms, and some thorium-232 atoms get transmuted into uranium-233 atoms. Both plutonium-239 and uranium-233 are fissile materials which are not naturally-occurring. They are both usable as either fuel for nuclear reactors or as nuclear explosive materials for bombs. (The USA exploded an atomic bomb made from U-233 in 1955.) Reprocessing of irradiated nuclear fuel: In general, to obtain quantities of plutonium-239 or uranium-233, it is necessary to “reprocess” the irradiated material that started out as uranium-238 or thorium-232. This means dissolving that irradiated material in acid and then chemically separating out the fissile plutonium-239 or uranium-233, leaving behind the liquid radioactive wastes which include fission products (broken pieces of split atoms, including such things as iodine-131, cesium-137, strontium-90, etc.) and other radioactive waste materials called “activation products” and “transuranic elements” Reprocessing is the dirtiest process in the entire nuclear fuel chain, because of the gaseous radioactive releases, liquid radioactive discharges, and large quantities of highly dangerous and easily dispersible radioactive liquids. Reprocessing also poses great proliferation risks because it produces man-made fissile materials which can be incorporated into nuclear weapons of various kinds by anyone who acquires the separated fissile material. Advanced Fuel Cycles and Breeders: “Any nuclear reactor-fuelling regime that requires reprocessing, or that uses plutonium-239 or uranium-233 as a primary reactor fuel, is called an “advanced fuel cycle”. These advanced fuel cycles are intimately related with the idea of a “breeder” reactor — one which creates as much or more fissile material as a byproduct than the amount of fissile material used to fuel the reactor. So it is only in this context that thorium reactors make any sense at all — like all breeder concepts, they are designed to extend the fuel supply of nuclear reactors and thus prolong the nuclear age by centuries. The breeder concept is very attractive to those who envisage a virtually limitless future for nuclear reactors, because the naturally occurring uranium-235 supply is not going to outlast the oil supply. Without advanced fuel cycles, nuclear power is doomed to be just a “flash in the pan”. Thorium reactors are most enthusiastically promoted by those who see “plutonium breeders” as the only other realistic alternative to bring about a long-lived nuclear future. They think that thorium/uranium-233 is a better fate than uranium/plutonium-239. They do not see a nuclear phaseout as even remotely feasible or attractive. “Molten Salt” reactors : Molten salt reactors are not a new idea, and they do not in any way require the use of thorium — although historically the two concepts have often been linked. The basic idea of using molten salt instead of water (light or heavy water) as a coolant has a number of distinct advantages, chief of which is the ability to achieve much higher temperatures (650 deg. C instead of 300 deg. C) than with water cooled reactors, and at a much lower vapour pressure. The higher temperature means greater efficiency in converting the heat into electricity, and the lower pressure means less likelihood of an over-pressure rupture of pipes, and less drastic consequences of such ruptures if and when they do occur. Molten salt reactors were researched at Oak Ridge Tennessee throughout the 1960s, culminating in the Molten Salt Reactor Experiment (MSRE), producing 7.4 megawatts of heat but no electricity. It was an early prototype of a thorium breeder reactor, using uranium and plutonium as fuels but not using the thorium blanket which would have been used to “breed” uranium-233 to be recovered through reprocessing — the ultimate intention of the design. This Oak Ridge work culminated in the period from 1970-76 in a design for a Molten Salt Breeder Reactor (MSBR) using thorium as a “fertile material” to breed “fissile” uranium-233, which would be extracted using a reprocessing facility. Molten Salt Thorium reactors without reprocessing?: Although it is theoretically possible to imagine a molten-salt reactor design where the thorium-produced uranium-233 is immediately used as a reactor fuel without any actual reprocessing, such reactor designs are very inefficient in the “breeding” capacity and pose financial disincentives of a serious nature to any would-be developer. No one has actually built such a reactor or has plans to build such a reactor because it just isn’t worth it compared with those designs which have a reprocessing facility. Here’s what Wikipedia says on this matter (it happens to be good info): To exploit the molten salt reactor’s breeding potential to the fullest, the reactor must be co-located with a reprocessing facility. Nuclear reprocessing does not occur in the U.S. because no commercial provider is willing to undertake it. The regulatory risk and associated costs are very great because the regulatory regime has varied dramatically in different administrations. [20] UK, France, Japan, Russia and India currently operate some form of fuel reprocessing. Some U.S. Administration departments have feared that fuel reprocessing in any form could pave the way to the plutonium economy with its associated proliferation dangers.[21] A similar argument led to the shutdown of the Integral Fast Reactor project in 1994.[22] The proliferation risk for a thorium fuel cycle stems from the potential separation of uranium-233, which might be used in nuclear weapons, though only with considerable difficulty. Currently the Japanese are working on a 100-200 MWe molten salt thorium breeder reactor, using technologies similar to those used at Oak Ridge, but the Japanese project seems to lack funding. Thorium reactors do not eliminate problems: The bottom line is this. Thorium reactors still produce high-level radioactive waste, they still pose problems and opportunities for the proliferation of nuclear weapons, they still pose catastrophic accident scenarios as potential targets for terrorist or military attack, for example.

Thorium reactors make prolif easier—don’t need to enrich them

Beste, 10 – reporter for Hot Air (Steven Den, “Nuclear Weapons for the Masses!” Hot Air Blog, August 31,

Glenn Reynolds tends to get hyped on certain kinds of high-tech. His latest “faster please” is thorium reactors. And yeah, there’s a lot to like about them. But there’s a really huge gotcha which is enough to kill the idea stone dead. Thorium reactors use natural thorium, which is isotope 232. There are a lot of neutrons running around in there; it’s how reactors work. If an atom of thorium 232 absorbs a neutron, it becomes isotope 233. Some will fission, but some won’t. Thorium 233 beta decays (HL 22 minutes) to proactinium 233, which beta decays (HL 27 days) to uranium 233. Uranium 233 is fissionable, and you can make bombs out of it. And the best part of all is that it can be purified chemically out of the spent fuel of the thorium reactor. You don’t have to mess around with gas diffusion or centrifuges. If, as some propose, there’s a thorium reactor buried in every backyard, you could face the possibility of pretty much any dedicated extremist being able to build nuclear weapons.

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