Uranium Is So Last Century — Enter Thorium, the New Green Nuke
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By Richard Martin
- December 21, 2009 |
- 10:00 am |
- Wired Jan 2010
Photo: Thomas Hannich
The thick hardbound volume was sitting on a shelf in a colleague’s office when Kirk Sorensen spotted it. A rookie NASA engineer at the Marshall Space Flight Center, Sorensen was researching nuclear-powered propulsion, and the book’s title — Fluid Fuel Reactors — jumped out at him. He picked it up and thumbed through it. Hours later, he was still reading, enchanted by the ideas but struggling with the arcane writing. “I took it home that night, but I didn’t understand all the nuclear terminology,” Sorensen says. He pored over it in the coming months, ultimately deciding that he held in his hands the key to the world’s energy future.
Published in 1958 under the auspices of the Atomic Energy Commission as part of its Atoms for Peace program, Fluid Fuel Reactors is a book only an engineer could love: a dense, 978-page account of research conducted at Oak Ridge National Lab, most of it under former director Alvin Weinberg. What caught Sorensen’s eye was the description of Weinberg’s experiments producing nuclear power with an element called thorium.
At the time, in 2000, Sorensen was just 25, engaged to be married and thrilled to be employed at his first serious job as a real aerospace engineer. A devout Mormon with a linebacker’s build and a marine’s crew cut, Sorensen made an unlikely iconoclast. But the book inspired him to pursue an intense study of nuclear energy over the next few years, during which he became convinced that thorium could solve the nuclear power industry’s most intractable problems. After it has been used as fuel for power plants, the element leaves behind minuscule amounts of waste. And that waste needs to be stored for only a few hundred years, not a few hundred thousand like other nuclear byproducts. Because it’s so plentiful in nature, it’s virtually inexhaustible. It’s also one of only a few substances that acts as a thermal breeder, in theory creating enough new fuel as it breaks down to sustain a high-temperature chain reaction indefinitely. And it would be virtually impossible for the byproducts of a thorium reactor to be used by terrorists or anyone else to make nuclear weapons.
Weinberg and his men proved the efficacy of thorium reactors in hundreds of tests at Oak Ridge from the ’50s through the early ’70s. But thorium hit a dead end. Locked in a struggle with a nuclear- armed Soviet Union, the US government in the ’60s chose to build uranium-fueled reactors — in part because they produce plutonium that can be refined into weapons-grade material. The course of the nuclear industry was set for the next four decades, and thorium power became one of the great what-if technologies of the 20th century.
Today, however, Sorensen spearheads a cadre of outsiders dedicated to sparking a thorium revival. When he’s not at his day job as an aerospace engineer at Marshall Space Flight Center in Huntsville, Alabama — or wrapping up the master’s in nuclear engineering he is soon to earn from the University of Tennessee — he runs a popular blog called Energy From Thorium. A community of engineers, amateur nuclear power geeks, and researchers has gathered around the site’s forum, ardently discussing the future of thorium. The site even links to PDFs of the Oak Ridge archives, which Sorensen helped get scanned. Energy From Thorium has become a sort of open source project aimed at resurrecting long-lost energy technology using modern techniques.
And the online upstarts aren’t alone. Industry players are looking into thorium, and governments from Dubai to Beijing are funding research. India is betting heavily on the element.
The concept of nuclear power without waste or proliferation has obvious political appeal in the US, as well. The threat of climate change has created an urgent demand for carbon-free electricity, and the 52,000 tons of spent, toxic material that has piled up around the country makes traditional nuclear power less attractive. President Obama and his energy secretary, Steven Chu, have expressed general support for a nuclear renaissance. Utilities are investigating several next-gen alternatives, including scaled-down conventional plants and “pebble bed” reactors, in which the nuclear fuel is inserted into small graphite balls in a way that reduces the risk of meltdown.
Those technologies are still based on uranium, however, and will be beset by the same problems that have dogged the nuclear industry since the 1960s. It is only thorium, Sorensen and his band of revolutionaries argue, that can move the country toward a new era of safe, clean, affordable energy.
Named for the Norse god of thunder, thorium is a lustrous silvery-white metal. It’s only slightly radioactive; you could carry a lump of it in your pocket without harm. On the periodic table of elements, it’s found in the bottom row, along with other dense, radioactive substances — including uranium and plutonium — known as actinides.
Actinides are dense because their nuclei contain large numbers of neutrons and protons. But it’s the strange behavior of those nuclei that has long made actinides the stuff of wonder. At intervals that can vary from every millisecond to every hundred thousand years, actinides spin off particles and decay into more stable elements. And if you pack together enough of certain actinide atoms, their nuclei will erupt in a powerful release of energy.
To understand the magic and terror of those two processes working in concert, think of a game of pool played in 3-D. The nucleus of the atom is a group of balls, or particles, racked at the center. Shoot the cue ball — a stray neutron — and the cluster breaks apart, or fissions. Now imagine the same game played with trillions of racked nuclei. Balls propelled by the first collision crash into nearby clusters, which fly apart, their stray neutrons colliding with yet more clusters. Voilè0: a nuclear chain reaction.
Actinides are the only materials that split apart this way, and if the collisions are uncontrolled, you unleash hell: a nuclear explosion. But if you can control the conditions in which these reactions happen — by both controlling the number of stray neutrons and regulating the temperature, as is done in the core of a nuclear reactor — you get useful energy. Racks of these nuclei crash together, creating a hot glowing pile of radioactive material. If you pump water past the material, the water turns to steam, which can spin a turbine to make electricity.
Uranium is currently the actinide of choice for the industry, used (sometimes with a little plutonium) in 100 percent of the world’s commercial reactors. But it’s a problematic fuel. In most reactors, sustaining a chain reaction requires extremely rare uranium-235, which must be purified, or enriched, from far more common U-238. The reactors also leave behind plutonium-239, itself radioactive (and useful to technologically sophisticated organizations bent on making bombs). And conventional uranium-fueled reactors require lots of engineering, including neutron-absorbing control rods to damp the reaction and gargantuan pressurized vessels to move water through the reactor core. If something goes kerflooey, the surrounding countryside gets blanketed with radioactivity (think Chernobyl). Even if things go well, toxic waste is left over.
When he took over as head of Oak Ridge in 1955, Alvin Weinberg realized that thorium by itself could start to solve these problems. It’s abundant — the US has at least 175,000 tons of the stuff — and doesn’t require costly processing. It is also extraordinarily efficient as a nuclear fuel. As it decays in a reactor core, its byproducts produce more neutrons per collision than conventional fuel. The more neutrons per collision, the more energy generated, the less total fuel consumed, and the less radioactive nastiness left behind.
Even better, Weinberg realized that you could use thorium in an entirely new kind of reactor, one that would have zero risk of meltdown. The design is based on the lab’s finding that thorium dissolves in hot liquid fluoride salts. This fission soup is poured into tubes in the core of the reactor, where the nuclear chain reaction — the billiard balls colliding — happens. The system makes the reactor self-regulating: When the soup gets too hot it expands and flows out of the tubes — slowing fission and eliminating the possibility of another Chernobyl. Any actinide can work in this method, but thorium is particularly well suited because it is so efficient at the high temperatures at which fission occurs in the soup.
In 1965, Weinberg and his team built a working reactor, one that suspended the byproducts of thorium in a molten salt bath, 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.
That proved to be “the most pivotal year in energy history,” according to the US Energy Information Administration. It was the year the Arab states cut off oil supplies to the West, setting in motion the petroleum-fueled conflicts that roil the world to this day. The same year, the US nuclear industry signed contracts to build a record 41 nuke plants, all of which used uranium. And 1973 was the year that thorium R&D faded away — and with it the realistic prospect for a golden nuclear age when electricity would be too cheap to meter and clean, safe nuclear plants would dot the green countryside.
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That’s not corrosion, that’s geometry changes. Graphite use in LFTR is totally different than in the RBMK. The RBMK had graphite AND water moderation, which was the real danger, because when the water boiled away the graphite was still there to moderate. In LFTR, if the salt expands due to heating, it changes the fuel/moderator ratio and automatically slows down the reaction.
Kirk -
I appreciate that Thorium reactors are a viable technology and, in a wider nuclear future may well have a place. But you seem to be willfully ignorant of the proliferation risks.
Liquid fluoride thorium reactors are literally one of the top approaches for U-233 weapons material production, as they can be run in a continuous process rather than batched and the processing is relatively benign. Long before anyone was talking about them recently for power production, some of us in the proliferation tech analysis community were looking at easy paths to weapons grade fissile material. This was on the short list.
As was posted elsewhere in another comment, the US has detonated a number of U-233 weapons tests. As was posted elsewhere, U-233 has nearly as low a critical mass as plutonium, and especially if produced in a continuous process avoiding much U-234 contamination it will be a easy to handle and fabricate material, much less tricky than Plutonium. It also has Uranium’s well known pressure/density behavior and long metallurgical stability, making a bomb designers work relatively easy.
Nuclear power is inherently nuclear weapons material proliferation risky, in some form or another. Some processes and reactor designs are harder to divert from, or produce dirtier output which is hard to weaponize. Conventional LWR for example are relatively prolific Plutonium producers, but it’s so heavily Pu-240 contaminated by useful burnups that the postprocessing to extract Pu-239 and purify it to weapons grade is highly difficult if not prohibitive, so the Pu content in LWR waste is by conventional criteria not that high a risk. The exact inverse is true for LFTR.
It may well be acceptable – for suitably monitored facilities and processing streams, under safeguards, to ensure that there isn’t diversion. That is not inherently much harder than ensuring that additional fissile target blankets for weapons grade Pu production aren’t used in LWR reactors, for example. But ignoring the need for that, and the consequences of failure to monitor, is not responsible or educated.
Willfully ignorant? I don’t think there’s anyone on Earth who’s thought more and pondered more on LFTRs and their proliferation potential than me. You say that a LFTR is a “top approach” for weapons production? I say, “what are you talking about?” If there’s one stone that has not gone unturned in the last 70 years of nuclear energy, it is the search for weapons material. Again–the facts speak for themselves: 70K nuclear weapons in the world, none of them based on thorium or its derivatives.
The US had one U-233 weapons test. It was, for all intents and purposes, a dud. It was never repeated and we know no details about the lengths they had to go to to keep U-232 contamination down in the U-233 they used. U-232 would infest all aspects of the uranium in a LFTR, and it can’t be separated. It broadcasts its presence like a fire alarm. It tells detectors hundreds of feet away it’s coming. It is the very LAST thing anyone who wanted a clandestine weapon would ever want to have in their weapon. In fact, I’ve seen recommendations that we spike all the U-235 in our weapons with U-232 to make them impossible to hide. That’s how potent this stuff is, and the uranium in a LFTR will be full of it. Furthermore, a liquid solution with uranium in it can be denatured instantly by adding another solution with U-238 in it. There’s no natural denaturant for plutonium.
That said, you’d have to look long and hard to find anywhere where I’ve recommended unrestricted global deployment of LFTR. I understand and advocate for their deployment by responsible parties. That’s why I’ve proposed building the power reactors into submersibles and parking them off the coasts of locations that need nuclear power, but never selling, giving, or trading the reactor to any non-responsible country. Sell them the kW-hrs, not the reactors that makes the kW-hrs. And it some other country wants to build LFTRs, then they have the technology to build centrifuges or graphite/natural-uranium piles or any number of FAR easier ways to get weapons-grade material than a LFTR.
Finally, I didn’t write this article nor did I preview it beforehand. Don’t assume that everything said in there is what I think.
Here’s something that Dr. Per Peterson of UC Berkeley said several months ago on our thorium-forum:
“First, and importantly, with just modest design effort, terrorists will never successfully steal U-233 from a LFTR and make a bomb, even if the LFTR uses Pa-233 separation and thus makes relatively pure U-233. The primary reason is that the U-233 must be remotely handled for personnel safety reasons, and it is pretty easy to make it very hard for insiders or outsiders to steal stuff from hot cells.
“On the proliferation side, U-233 has roughly the same bare-sphere critical mass as plutonium, almost no spontaneous neutron generation, and almost no heat generation. This is excellent from the perspective of weapons use. The primary disincentive for weapons use involves OSHA issues due to personnel radiation exposure from U-232, which can be avoided by choosing weapons grade plutonium or HEU instead of U-232. If one has a dedicated production capability for weapons material, it’s quite logical that it would focus on the plutonium or HEU routes, and not thorium. But that does not mean that the potential diversion of U-233 by a state would not be a major concern, when the major barrier to use of U-233 in weapons involves OSHA rules rather than actual physical limits.
“Reducing demand for uranium enrichment has clear potential non-proliferation benefits, because uranium enrichment is particularly problematic from the perspective of the development of clandestine production facilities. A fission energy system based on LFTRs will also involve far smaller inventories and flows of plutonium than one based on fast-spectrum IFRs. But LFTRs will still require effective IAEA safeguards to assure that the state cannot divert material without detection, and will have similar non-proliferation issues with other fission reactors (e.g., break-out remains theoretically possible, if likely unattractive, particularly for denatured LFTRs). As is commonly said, no technologies will offer a silver bullet to eliminate proliferation risks, but these risks can certainly be managed and minimized.”
George,
While it is possible to design and construct a LFTR reactor for weapons purposes it is also possible and reasonable to design the reactors to make proliferation quite hard. If anyone is willing and able to build a reactor to make weapons with, then no technologist can stop them. LFTR is not the simplest reactor to design and would not be the reactor of choice for beginner weapons states.
With unity breeders (be it IFR or LFTR) there is no need to add fissile material once the reactor is started. This means once the world has enough of these reactors there is NO further market for enrichment services. There is no market for centrifuges. There is no market for mining uranium. These changes would make proliferation very much harder, would make weapons activity more obvious, and provide longer lead times for the world to respond to problem areas.
You mentioned plutonium mixed with pu240 from LWRs and concluded with “the exact inverse is true for LFTR”. It sounds like you think the Pu content of LFTR is more of a weapons concern than for an LWR. This is not true.
LFTR produces 10x less plutonium than an LWR. The plutonium it produces is Pu238 which is the least worrisome isotope of plutonium. If you continuously feedback the plutonium into the reactor you get much much higher burnup than in an LWR – which means the isotropic mix of plutonium is less attractive to weapons producers.
If you have some plutonium you wish to destroy a LFTR will do the job quite nicely. Note that it will destroy the plutonium – not just bury it in the ground. I think destroying the plutonium inside a LFTR is a much better plan for the existing stockpiles of plutonium embedded in spent fuel (compared to storing it onsite or burying in the ground).
Looking ahead many decades when we have built out the full fleet you will have no uranium mining, no enrichment, no routine shipments of fissile, and sufficient energy to reduce the chances of wars over oil. This will make anti-proliferation treaties far more effective as it removes the nuclear power cover for many weapons activities.
Let me throw in a comment I read by another nuclear engineer…
“Yes, it’s possible that the LFTR could be made resistant to easy U-233 extraction. However with a few changes to the blueprints, I could change it right over to being perfect for U-233 extraction. And there are thousands of other nuclear engineers, from Russian and other places, who could make those same changes just as easily. Perhaps not after the reactor is running, but certainly during construction. This is less true of other (solid core) reactors.”
The LFTR has unique qualities which means it needs to be very agressively examined and worst-case scenarios considered, not glossed over.
Nobody’s glossing over anything–that’s why we’ve had an open thorium-forum for three years now where people can come and discuss this technology and get smart on it. So that a community will exist that knows how to recognize a proliferation-resistant LFTR from a non-one. But as Professor Peterson says, a country that’s determined to build weapons wouldn’t be deterred by a proliferation-resistant LFTR. They’d simply build a graphite-uranium pile or enrich uranium, just like we did back in the Manhattan Project. Nothing we’re going to do would stop them. So why should we (responsible nations) turn our back on thousands, nay millions, of years of clean energy?
My question is why does the picture of the three stages of thorium reactor plants show the last, final all thorium stage as not needing cooling towers? You still have to convert the thermal energy generated by the core to electricity so is there some magic step I am missing that would allow for the direct conversion of thermal energy to electrical energy?
I wondered the same thing myself. The ocoling towers are needed to cool the water that is used to condense steam back into water. LFTR runs at a much higher temperature than an LWR, so it can effectively use a closed-cycle gas turbine power conversion system rather than a steam turbine. That’s what lets it have a power conversion efficiency of about 1/2 rather than about 1/3 for an LWR. But it still has to dump 50% of the heat it generates. There are a couple of options. One would be to directly air-cool the gas used in the gas turbines in counterflow heat exchangers. This would allow you to install LFTRs in arid locations that don’t have convenient bodies of water for cooling, but at the price of a few percentage points of efficiency. If you did use water cooling of the gas in a countercurrent heat exchanger, using cooling towers is one options, but they would be MUCH smaller than the equivalent units for LWRs for two reasons: you’re rejecting about 2/3rds as much heat (for the same amount of electrical power generation) and you’re rejecting the heat across a much higher temperature range, which allows you to dump a LOT more heat into a given unit of air. So air-cooling or cooling towers, but much smaller ones.
Let me put it out there on the table – the trivial obvious and easy proliferation pathway for LFTR is to chemically process the LF material to extract the Pa precursor in a continuous loop. You then let the precursor decay to U-233 in the absence of neutron flux. You have to do this actively enough to keep much Pa-231 -> Pa-232 reaction from happening, which is where the U-232 comes from.
If you’re scrubbing Pa-231 out of the main fuel actively enough the end result U-232 contamination is negligible.
You basically then keep milking your Pa supply chemically, pulling U out of it as the Pa decays.
With normal thorium reactors (heavy water, etc) the batch mode makes U-232 unavoidable if there’s much fast neutron activity, and unavoidable if there’s much Th-230 in the input. With this process, you don’t care, the Pa is pulled out in process and the Pa-231 doesn’t get enough chance to absorb the extra neutron to Pa-232 and thence the contamination cycle.
“Clean” U-233 produced in this manner is an ideal weapon material. U-233 from conventional reactors with U-232 contamination is not, but the weaponized LFTR U-233 output is nearly ideal.
The primary reason this was not weaponized seems to be that it didn’t occur to anyone in the US or Russia in the 60s or 70s, and by the 80s and 90s we were winding down fissile production and not looking for new path choices. The fundamental underpinnings for bomb grade LFTR U-233 production are littered all over the late 80s and early 90s open literature; I don’t find it credible that the bomb lab people weren’t thinking about it in papers not now accessible to those without RD clearances.
Again – despite all this, I think it’s worth pursuing. But in pursuing it, the weapons cycle issues need to be considered. Ensuring that plants are built and operated in a way that ensures U-232 contamination (avoiding continuous Pa processing out of the LF fuel, essentially) is relatively easy for an active IAEA effort, as the processing is physically large and necessarily closely tied to the reactor as you need to cycle the bulk of the fuel through the extractor each day. With proper care and inspections the actual risk is arguably not significantly worse than Pu output from LWR operations.
Those overview assumptions should be tested and validated. There may be more vulnerabilities, or the continuous extraction process may turn out to be harder than it seems from a first analysis (I have not, for example, built a test lab to extract Pa from a LF bath in continuous processing, and I’m not aware of anyone else doing so, though several methods of doing so have been floated around and seem viable).
If doing it in continuous processing is hard, it’s still a weapons pathway, as one can oversupply fuel and run it through in a one way loop with short enough dwell times to keep Pa-231 buildup and irradiation low, batch processing off the end and then returning it into the input stream. It’s not clear what the economics are on that, but the high level overview looks showed it to be a risk.
The real risk of LFTR is that even with safeguards and safe plants, widespread proliferation of the technology makes manufacturing secret LFTR plants outside of the safeguards regime practical and easy. They can be much smaller and cheaper than the alternate reactor based cycles, so the overall infrastructure including reactor and chemical processing facility is smaller and will produce more output per dollar invested.
George, read “Fluid Fuel Reactors”. Written in 1958, there’s page after page where they talk about protactinium isolation and it’s implications. You haven’t found anything that they didn’t know about in the 1950s, and they did not attempt to weaponize thorium, despite the fact it is globally abundant, breeds in a thermal spectrum, and has an intermediate product (protactinium) that is chemically separable. You haven’t discovered some dark secret or terrible flaw.
Thorium is abundant in Sithilis but, your mining level must be very high to smelt it. Still, it brings hope…
Kirk – I know you’ve been doing this since 2000-ish.
I’ve been doing for more than a decade longer. Some of the resource material on your website is outside what I’ve read – but not a whole lot of it. I don’t come close to working LFTR all day long, because fuel cycles are only a small part of the problem, but I’ve studied it a lot over the years, with various isotopic fuel choices and fissile material output choices.
Please don’t discount the proliferation risks which weapons people tell you about. I’m not pulling it out of my nether regions. As you admit, the fundamentals were known in the 50s and 60s. The US choice not to pursue a Thorium – U-233 program was programmatic not due to an unsolvable a technical barrier. The issues with U-232 contamination are avoidable with continuous processing, and the output if you do so is an excellent weapons material.
Please don’t mistake me for some sort of knee-jerk anti-nuclear power activist, or a LWR apologist of some sort. I work on nuclear proliferation technology risks because they’re significant and scary, and because they’re largely not well known in public. And they’re also significantly discounted by experts in the power field. There is a tendency to view weapons as a narrowly defined, easy to avoid corner. In reality, there are myriad technically possible paths to minimally workable fissile bomb materials, and many many more practical paths to good fissile bomb materials than are typically credited. See the relatively recent public admission that Neptunium’s critical mass is small enough for practical weapons, etc.
I am not saying “Don’t build LFTR”. I’m saying, with anything you advocate doing, do it with a educated and insightful awareness of weapons material proliferation. Ask some weapons people, and think about what we tell you. If we tell you that we can weaponize it, listen, and work to build in safeguards. Telling the public that it’s entirely safe, when weapons people are telling you it is not, is irresponsible.
It is not necessarily a bad idea, all things considered. But it at the least needs to have appropriate safeguards and attention paid to weapons diversion of fissile material. I leave you the power cycle and energy cost issues to work and advocate on – I don’t approach being expert in that area. If those are strongly positive then that’s great. But the system needs to be one that avoids the proliferation risks proliferation people see.
George, could you give us greater insight into the proliferation-response community you represent?
George Herbert,
Please consider joining the Energy from Thorium discussion forum, where you will meet people who are working actively on the issues you are concerned with. For example, U-233 (n,2n) –> U-232 regardless of what you attempt to do with protactinium. So please contribute your ideas in the forum where they will get the attention of the best minds on this topic.
George,
I had assumed that anyone who could substantially modify the blueprints and build a clandestine LFTR would be a fairly sophisticated nation. Wouldn’t such a nation also be fully capable of breeding Pu using a much simpler pile and wouldn’t that be their preferred path? I agree if I wanted to build thousands of weapons I would look to designing a fluid reactor for the purpose but if I was looking to build a few I would follow the path the US trail blazed back in the 40’s.
There are several conceptual variants of LFTR. Some have Pa extraction and some do not. Some breed and some do not.
One observation is that weapons states plus states who are fully capable but have chosen not to be weapons states (Japan, Canada, Germany, … ) make up 80% of the energy consumption. So one thought is that initial deployments would be for such nations. As the technology is established and can be fully automated one could provide sealed units (think of 1 GWe, 60 year batteries) for deployment elsewhere. Another thought is submarine deployment where access is more difficult.
One concept (my favorite) is to design the machine to be a unity breeder so that we neither generate nor consume fissile. This eliminates the need to ship fissile around. Second, I would not use Pa extraction – this loses some breeding performance but if the target is unity breeding then we have some breeding margin to work with. Finally, I would not extract Pu in the field. Instead, the Pu would go with fission products (in particular the lanthanides). The concept is that periodically (where periodically is somewhere between years to life of the reactor) the fission products + Pu would be sent to a supervised reprocessing site where the Pu (depending on the cycle time 50-90% Pu238) would be extracted. The Pu238 could then be used in radioisotope generators or sent to fast spectrum LFTR reactors for destruction.
I appreciate that we will need to adjust the design to reduce proliferation risks. We do talk about this quite a bit. But I would also content, that the biggest proliferation risk (beyond the desire for power by humans) is wide spread commercial uranium enrichment services. This technology has the potential for eliminating the need for such services over the next 50-90 years.
The relevant question is not could a LFTR be built that facilitates weapon making but rather
Can we design and build a LFTR that satisfies the worlds energy needs while simultaneously not increasing proliferation risks? I think the answer is yes.
Robert -
(Doing this from memory, I haven’t got all my papers in front of me)
If you are processing Pa out of the fuel stream chemically and isolate it, then the Pa-233 decays away from the reactor, and no further Pa-neutron or Pa product-neutron reactions have to occur, other than any produced by Pa decay product neutrons or Pa spontaneous fission.
You will sweep up any Pa isotopes you have in the fuel stream- but the dominant one will be the Pa-233. Pa-232 isn’t going to form in quantity, as it comes from the Pa-231 + n reaction, and if you reasonably promptly strip the Pa-231 out chemically then it’s not experiencing the neutron irradiation that needs. Pa-231 in the Pa output stream is annoying but not that serious a problem – it has a long (30k years -ish) halflife and you are chemically separating the U-233 out from the sequestered Pa, so the Pa-231 presence is not problematic there.
The comments thread is much more enlightening and better researched than the original article. Can we swap them?
“Posted by: thomasrex | 01/3/10 | 8:56 pm
There are thousands of potential reactor designs that have been proposed over the last 50 years. All of them have their advantages, disadavantages, risks. All of them are touted by their designers or supporters as the “better” reactor.
The LFTR is just one of many. Maybe it will at some point in the future be prototyped, if the appropriate regulatory agencies can be convinced to move forward. Unfortunately, most of the people with sufficient clout to drive this design are already working on their “own” designs. Maybe the LFTR can attract a rich silicon valley type to support it.
Kudos to Sorensen and his colleagues for pushing this design forward.
Above all, we must realize that there is infinite energy on the earth. Just the depleted uranium sitting in warehouses, abandoned and unused, has enough energy to power the electrical grid for 10000 years if used in the Terrapower travelling wave reactor or in the Prism reactor.
Easily available Thorium supplies, if used in LFTR, could power the world forever.
All of this could be done without the enormous environmental and economic drawbacks of solar, windpower, biofuel, and wave power, the worst energy sources on the planet.”
Best comment of all!!!!
Has India used Thorium – to U233 for any of their weapons technologies? Does anybody know? India has massive natural Thorium deposits, that’s why they are so interested in Th reactor technology (makes perfect sense).
George, while you fuss over protactinium, realize that a LFTR is essentially a unity breeder, making only as much fuel as it uses. So if some LFTR-operating country all of the sudden decided to break out as you seem to fear so much (unbearably tempted by the presence of protactinium, unable to resist) and decided to use their Pa inventory for wickedness, the refueling of the fuel salt would stop, within a few days there would be insufficient fuel to keep the reactor critical (since it operates with essentially no excess reactivity), and the lights would go out. People would notice major blackouts and would wonder if this wicked country had their hand in the protactinium jar at which point whatever happens when you breakout would happen (since the world still can’t seem to figure out how to respond to nations like N Korea or Iran who do this).
Mr. Jorgensen asked the right question–does LFTR increase the risk of proliferation? Is it easier to build a LFTR and use it to make weapons-grade material than to centrifuge uranium or extract lightly-irradiated plutonium from a natural uranium/graphite pile? If you really do represent some type of proliferation response community (and I’m waiting to find out if you do) then you already know that the answer to this question is emphatically no.
Kirk -
“Who I represent” is myself. People I talk to are most of the independent experts on weapons design. We have no organized community organization per se to represent (for what are probably obvious reasons); there are organized nonproliferation policy organizations around, which we generically and I specifically talk to as well, but I don’t represent them either. Some names you might recognize would include Howard Morland, Carey Sublette, Andre Gsponer, although those are just for context and not indicating that I speak for them in any way. If they’ve published books or papers on nuclear weapon design issues or history I’ve probably corresponded with them, many of them actively.
If you’re looking for some sort of employment or affiliation conflict of interest, I am not employed by or affiliated with nuclear power, government, or other institutions which might have some sort of organizational bias in this field.
Re LFTR as a unity breeder -
It’s possible to design a LFTR unity breeder, yes. If designed and operated in that manner it is fairly safe, as the proliferation risk involves diversion of the fuel supply in use and people will notice the shutdown.
It’s also possible to design net breeders using the same scheme, for which Pa net output in sufficient kg quantities for weapons programs are risks.
It is not entirely clear if it’s possible to build a LFTR unity breeder facility and reactor design that is inherently incapable of being operated in a net producer mode with minor modifications and malign operators. Such facilities would have to be monitored to ensure that they aren’t modified or operated inappropriately.
It is clear that many of the unity breeder design concepts and technologies are applicable to net breeder designs which are of similar overall configuration, and that unchecked proliferation of the design and operations knowhow therefore makes designing and building those dedicated facilities easier. It appears to be easier to design a LFTR dedicated weapons production facility than it is to build a large CANDU or graphite Pu facility, when you factor in the rather large and dirty Pu separation facility for industrial scale fuel reprocessing.
Centrifuging U to get HEU on industrial scale requires thousands and tens of thousands of centrifuges (or alternate enrichment technologies, whatever form your program ends up using). You end up needing about a factor of four to five more output material for HEU than you do for U-233 or Pu weapons, and the inputs are massive (you extract about 0.3% of the start mass in HEU, for typical SWU / capital / energy / input stream volume tradeoffs); for a bomb requiring a notional BOTE example 20 kg of HEU you’d need roughly 6 tons of natural uranium.
I will avoid, in the interests of space and proliferation sensitivity, a detailed discussion on the tradeoffs of burnup and processing volume and processing type and intensity for various Pu breeder reactor concepts, ranging from BWR batch mode production to CANDU to gas reactor to…
A LFTR for weapons production can be fairly simple; a reactor vessel and a heat rejection system, plus a chemical processing facility to cycle the fluoride fuel stream and strip Pa out and sequester it until U-233 decays out of it. One does not need to use the LFTR to produce power, though one could do that (a combined LFTR for power and something like a small uranium enrichment facility using that power, somewhere underground, would be a highly annoying combined operation…). If one just wants the heat to go away, it’s not that difficult to cycle it out into a heat dispersion or heat sink somewhere, though overhead IR imagery usually alerts on otherwise unexplained gigawatt heat sources.
As an aside – I have spent far too much time over the last year staring at pictures of construction in and around hills in Iran (and elsewhere), a topic which is highly engrumpenating. Clandestine proliferation is a concrete problem, literally and figuratively.
If a state wants to proliferate, this is how they do it:
http://www.nytimes.com/2010/01/07/world/asia/07korea.html
“It appears to be easier to design a LFTR dedicated weapons production facility than it is to build a large CANDU or graphite Pu facility,”
I am confused by your arguments here. If we presume a nation that has the skills, knowledge, and will to build dedication weapons production facilities just what is it that we are denying them by preventing the use of LFTR for producing electricity? A nation with such skills can certainly follow the route laid out by others already if they desire to build weapons. Achieving non-proliferation with such a country requires a different approach than trying to deny them knowledge.
We also need to balance the risks of deploying nuclear power responsibly with the risks energy shortages leading to resource wars. I’m all for being responsible but this cuts two ways. We must be responsible in deploying technologies, for example forgoing certain features such as plutonium isolation in commercial reactors. But likewise, being overcautious (such as saying any nuclear power leads to nuclear war) will stop the use of nuclear power and increase the chances of energy resource wars.
Looking over the long term, I think technically the most effective thing we can do to stop proliferation is to eliminate commercial enrichment. Unity breeders like LFTR could do this – LWR’s can not.
You stated “The real risk of LFTR is that even with safeguards and safe plants, widespread proliferation of the technology makes manufacturing secret LFTR plants outside of the safeguards regime practical and easy. They can be much smaller and cheaper than the alternate reactor based cycles, so the overall infrastructure including reactor and chemical processing facility is smaller and will produce more output per dollar invested.”
This statement sounds like you are categorically opposed to inexpensive nuclear power – but perhaps I misunderstand what you mean. It is my hope that we can indeed produce LFTRs at a lower cost than coal. This is the only path to stop the dramatic expansion of coal burning that is currently happening in China – and I presume will happen soon (<20 years) in India. If your stance is that inexpensive nuclear deployed in China and India is inherently too much of a proliferation risk (note that both are already weapons states) then we will just have to agree to disagree.
I am not opposed to nuclear power, low cost nuclear power, or LFTRs. Both the goals of cheap power, more available in more places, and clean power, reducing carbon output, are valuable to me. I am opposed to making proliferator states’ lives easier. Those are somewhat in conflict.
Ending uranium enrichment worldwide only ends one path to fissile materials. If you do it with LFTRs then you open the whole Pa -> U-233 spectrum up as another avenue, though that’s theoretically open now (someone could be doing it right now under a mountain in North Korea or Iran and we might be none the wiser). Commercializing and making the technology widespread would enhance and expand the risk there. None of these options using nuclear prevent various uranium irradiation to plutonium schemes – any neutron source, i.e. any fission reactor, can irradiate natural uranium to breed plutonium. Even if you ban LWRs, and all U enrichment, adding a natural U blanket to a LFTR system would give you a direct path to Pu.
And, it’s not clear that you can ban U enrichment, practically. The knowledge is not erasable. Several nations have started building centrifuges on their own.
And for that matter, there’s CANDU, where you’re enriching the heavy water, not the fissile material (necessarily). Another great path to plutonium, and oodles of tritium out the side…
Eliminating LEU and its commercial production technology cuts off one pathway, but doesn’t cut off nearly all the paths which are known to be viable or even which have been used. India used a CANDU reactor for at least much of their fissile material for their first bomb, in the 70s. Iran’s trying pretty much everything – LWRs and the research on Pu extraction, graphite reactors, LEU centrifuges with a presumed not yet operational or not yet located topping facility to weapons grade HEU outside any irradiation process, a CANDU type reactor complex under construction.
To avoid proliferation you need sufficient blocks and monitoring on all the possible pathways. To use atomic power for electricity you need to (as a modern industrial international society) keep many of those pathways open.
Blocking one off completely and leaving other viable methods open won’t work.
LFTR power reactor proliferation will open up some new pathways, unavoidably.
This does not mean LFTR is a mistake, nor does it mean we should leave all existing other ways open. But one has to keep an open mind on the totality of the risk paths.
If we believe or assert that the NPT regime and IAEA mechanism is good enough now for existing paths, we can apply that to LFTR and not really make the situation worse in any significant way. There’s a moderate to serious risk that the clandestine pure weapons / zero power LFTR would be easy enough in a widespread LFTR regime that it would make the situation worse, and paying attention to that is pretty important.
This is not opposition. Enlightened risk theory says to look at the risks of what we’re doing now and compare them to the risks of LFTR and balance them, and by and large that comes out favorably to LFTR. But you need to rationally and openmindedly look at those risks in depth to make that choice in an educated manner.
“Even if you ban LWRs, and all U enrichment, adding a natural U blanket to a LFTR system would give you a direct path to Pu.”
No it doesn’t. George, you think you understand this technology but clearly you don’t. A uranium blanket can’t have Pu removed simply because fluorination would remove ALL the uranium, not the plutonium. You talk about this reactor and its technologies like they’re legos and you can pick up and mix and match the pieces in any way you want, and that it will still work. We on the forum understand how the pieces work and in which combinations they work and how they work together to preclude any proliferation advantage.
You also clearly do not understand the challenges involved in protactinium isolation. It is QUITE challenging. I am interested in investigating it because of the performance advantages it confers on the reactor, but it is not simple or off the shelf. That said, it is easier to isolate protactinium in LFTR than any other proposed type of thorium reactor. But it is still quite challenging.
You need to consider what a nation risks by developing nuclear weapons. It is a titanic gamble, and it is not one that would be made lightly. Proliferators will not attempt to succeed at their dark task with unknown or uncertain technologies like U-233 or protactinium. Having taken this awful step they will stick with what they know works–enrichment and plutonium. That is why every nation has proliferated along the same route. You need to study your history.
Georgeherbert:
There is a vast divide between theory and reality. The devil is in the details. No matter how hard you try, you can’t make pure U233. Perfection is not a property of the real world. Equipment will break down for a time and/or the process that stops the Pa-231 -> Pa-232 reaction from occurring will not be 100% effective. Some micro-level amounts of U232 will always contaminate U233. It can’t be avoided.
Unlike all other radioactive sources that go down over time, the radioactivity of U232 increases substantially over time. After just 10 years, u232 radiation will increase by a factor of 100 and stay that way for hundreds of years. Radiation from that trace amount of U232 contamination will have grown to prohibitive levels for weapons applications. An old U233 bomb will become a very hot bomb; a bomb that is hard to hide; a bomb that is hard to maintain; a bomb that is not reliable.
As a example, from the mid 50’s to the mid 70’s the US tried to produce “pure U233” for weapons use at the Hanford Washington site and it was very hard. All told, they produced about a ton of it using purpose build ultra low level neutron reactors.
Since the late 90’s DOE wanted to get rid of that “pure U233” inventory but that U233 can’t just be down blended like U235 because that “pure U233” is just too hot to deal with in the usual highly enriched uranium way. It needs special and expensive handling. So after 15 years of failed effort, it is still around and the cost of its destruction is ever increasing as the radiation from traces of U232 in it increases.
The few U233 weapons tests that you reference demonstrate a consistent and substantial overestimation of the explosive yield produced by U233. The best nuclear weapons designers in the world can’t predict how a U233 weapon will actually perform. Without an extensive U233 weapons testing program supported by many actual weapons tests, a U233 weapon will be too unreliable in its performance for a weapon state to tolerate.
You do not want to go into a nuclear battle armed with a dud or a fizzle. The time for U233 weapons development has long past.
With the nuclear test ban treaty now in effect, it is unlikely that the world would permit the testing needed for the development of a reliable U233 weapon to occur. Prospective weapons states will stick with the tried and true plutonium route to a bomb; if they don’t, they are dangerously foolish.
The good news for us is that that U233 is BEYOND precious to us in the LFTR community, since it is the ideal fuel to start the reactor and absolutely minimizes the long-term production of waste. Also, the reactor doesn’t care how radioactive it is.
http://www.energyfromthorium.com/images/slide_LFTRstartupFuels.png
This image might help explain the advantages of U233 as a LFTR startup fuel. Of course, U233 is also the long-term fuel of a mature LFTR, continuously produced from fresh thorium and continuously burned up through fission, so that the amount of U233 you have when you shut down the reactor is the same you had at the beginning.
What a intresting energy area. Thorium must be ideal energysolution for the world. To get more knowlegde about thorium, i found http://www.itheo.org/.
It’s very worrisome that people seem so unwilling to honestly and publicly debate the very real proliferation hazards that would be added by these reactors.
Debate away, thomasrex, I’ve got a whole public forum devoted to this and other issues of thorium reactors. You seem disappointed that many others who know a lot about the issue don’t seem nearly as concerned about it as you do.
I agree with one of the earlier posters–thorium will never lead to proliferation because even if a country was dumb enough to attempt U-233 weapons it would require an entire weapons testing series that would never be allowed to happen in the real world. They’d use U-235 or plutonium instead.
There is no such thing as “green nuclear energy”!! Neither is nuclear fusion–still in the labs thank god–”safer” than fission, if anything, it is more dangerous! As an atomic physicist with more than 35 years experience with radiation and radioactive substances, I can assure you that none of the serious waste, leakage, or storage problems have been solved! Dr. Chu, Obama’s new energy adviser, has a Nobel prize in physics and knows this very well!
This is a late response (since paying jobs get first priority), but comes from someone who has investigated thorium technology for some time. It was particularly irritating, and yet delightful, seeing the warnings against thorium and more importantly against liquid core systems like LFTR. Irritating because the low proliferation risk is one of the best selling points for thorium and it is disingenuous to warn that the security community is well aware of it as a grave evil. Delighted since, if this is the best salvo of negativism this technology has to contend with, it is sure to get a fair and open chance at competing in the energy market.
This article is an excellent start to a serious and important debate. Is there no good answer to the future energy needs of the world? Are there no new cleaver ways to exploit older knowledge? Thorium has tremendous potential and has been neglected because of its lack of relevance to nuclear weapons, not the other way around!!! If someone is concerned about proliferation, I am not sure they would then continue to openly state, in detail, how to go about doing it on the net. If it is the best-kept secret ever it would be prudent not to bring it up at all. Fortunately anyone reading the comments would be discouraged seeing that LFTR type reactors have little possibility of any proliferation viability and that fortunately for them, there are many easier ways to go about doing it. Now some people post that they are nuclear engineers, well, so am I; if they say they are Ph.D. rocket scientists, so am I; if they say they are familiar with nuclear weapons, solar power and fusion, so am I … (ok, I am stealing from Saint Paul). Yet, there are many others, far greater in intellect, experience and accomplishments than me, who have helped shape the debate on thorium well before its benefits were brought before the public eye in this article. One cannot simply dismiss the new thorium revolution as a faulty notion coming from one rogue scientist, an illiterate mob, or a group of snake oil salesmen.
The article references “others” and a “cadre of outsiders” that has associated with Kirk Sorensen on thorium, but does not go into any detail. The vast number of these supporters have reputable and highly technical jobs in many diverse fields and most have advanced degrees in science and technology. Over the past several years they have spent countless hours investigating, debating and trading various concepts and ideas on thorium as well as other energy concepts. The primary debate has always been centered on “Is this the right technology, or not, and what is the absolute best way to use it?” [A side note of contention with the article was the illustration of a very large, almost fusion-looking, power plant when very small units are the likely economic boom technology.] There is no profit agenda in the thorium blog. It is ‘open source’ and it is meant to keep people honest in their claims and their motives. Look elsewhere to condemn the use of thorium.
Now, who might be against exploring this option? The environmental purest might, just out of habit or fear that any nuclear power source cannot be safe. But surprisingly the debate there has been relatively cordial, even if they are not completely sold on the idea. Then there is the other “extremist group” from the existing nuclear power arena. Most DOE organizations will hate it since it is neither fusion nor the conventional fission reactor that they are familiar with. Some in the nuclear industry might consider it an economic threat (a false notion since the people who advocate thorium do not fear existing nuclear power, nor want to slow down any plants due to come on line). Big coal certainly could see it as a threat, but even then, thorium could not replace them overnight and they would simply learn to operate the new-fangled LFTR and sell electricity exactly the way they do today. Then there are the people who truly know what is, and is not, a proliferation threat. Those that have limited compartmental clearances, have a need to know, and will never say anything publicly (I think the phase is “I can neither confirm or deny…”). You will never actually confront them and anyone who claims the status is instantly exposed as a fake. We are left to open literature and our common sense to weigh the merits of proliferation or anything else to do with thorium.
Lastly, let’s take on the proliferation issue itself. Mr. Sorensen’s response contained the single salient point that anyone can understand, “If there’s one stone that has not gone unturned in the last 70 years of nuclear energy, it is the search for weapons material.” What person is going to say Dr. Weinberg missed that point about thorium, or the US/Russian arms race missed it, or every nuclear scientist from Nazi Germany to North Korea missed it? Then claim that a small group, interested in energy, has discovered the secret by accident, does not even realize it, and will doom the world to nuclear Armageddon. This kind of farce dilutes the real facts and issues. No nuclear device is 100% useless for making a weapon. If you have neutrons you can contaminate material or make depleted uranium into plutonium. If you have the knowledge of how to run a reactor, you have the basic starting point for understanding a nuclear weapon. The point is that LFTR, in the right configuration, is far more difficult to steal from because it inherently needs most of its released neutrons to keep the process going! Why is the fast breeder so attractive despite its costly and dangerous operation? – Precisely because it releases a larger number of neutrons than it needs to sustain the reaction and that allows more production of weapons grade material, namely plutonium, which is universally considered the best. Therefore, it does not matter if one conjectures that a significant modification can be made to a “stolen” reactor or not. Diverting neutrons from the reactor to make your own fuel (i.e., plutonium rather than U233), or stealing protactinium, or the U233 fissile fuel, just before it enters the reactor will shut the reactor down. If one takes very little out then it takes a long, long time to get enough to do anything and amplifies the risk of being caught doing it. So it is ludicrous to conclude it is a larger proliferation threat than present-day reactors based on this one fundamental argument alone. To further bolster the point, the theoretical breakeven point with thorium is pretty slim, and as everyone knows, the real world implementation of any theory is always less efficient and more costly in practice. We know a liquid core reactor can be done since Oak Ridge was highly successful, but smaller designs are geometrically more vulnerable to neutron loss and it will not be easy to take anything away from the reactor without it easily being noticed because of the limited design margin (hum, makes sense since history shows this very limited production ability made it so unattractive they never bothered to do it even as a backup plan, or with hopes they could tweak production up if they tried). This is one way that SMALLER reactors are LESS of a proliferation threat and less likely targets than larger versions. Still they have tremendous capacity and flexibility to meet the great energy demands facing the world, which is a major source of conflict itself.
I’m no expert, but I must say that the commentators excluding georgeherbert sound like a bunch of religious fanatics bent on extinguishing any doubt. I think you are weakening your case in the process. All this “we the community” talk is non-scientific/academic/professional.
Apologies, I should have said “some of the commentators” – I don’t want to sound to bigoted myself
)
Let’s say it is possible to make a thorium power plant such that electricity was so cheap it was not reasonable to meter it. In other words it would be like modern phone plans – unlimited power for one low monthly fee. Now that would be AWESOME.
However, it will probably never be done. And it has nothing to do with technology and everything to do with politics. First, about half of your (high) electric bill is taxes. Do you think the government will give that up willingly? Next, the government is moving to increase monitoring and control of your electric use through your meter – another thing they will not want to give up. Third, the “green” revolution is not about going green and is all about control and manipulation (if it was about being truly Green, would we have corn-based ethanol?). Fourth, the far left “green” people are more of a neo-Luddite group than an environmental group. They don’t want to see low cost electricity that anyone can use unlimited amounts of. Instead the neo-Luddites want to force people to use less of everything, especially electricity.
The current energy companies also have hundreds of billions invested in the way everything is currently done. New technology means changing the infrastructure and there is little incentive for that. Especially if changing the infrastructure means changing the pricing models.
Heck, it would be possible to make neighborhood-sized thorium plants and both limit the big companies and increase competition.
So, we have the government against the idea, the embedded oligopoly against the idea, the radical environmentalists against the idea, and most of the energy companies against the idea. Since this is also a complex subject that uses the “nuclear” word, it would be easy to drum up fear, uncertainty, and doubt in the general populace.
This is an example of a great idea that is most likely doomed.
Admiral Rickover chose the LWR with it’s heavy shielding and common-sense design over thorium and over the HTGR for heavy vessel and eventually submarine use. Since we “won” the Cold War, history has been kind to him. But it appears to be time to revisit the higher thermal efficiencies of liquid and gas cooled high temerature reactors.
Between The pebble Bed, the LFTR, algae, Focus Fusion and fracking shale, the energy future is looking up.
The proponents of lowered energy consumption such as Maurice Strong. Al Gore and Hussein Obama ignore that the only way to profitably reverse entropy is to apply large does of very cheap ENERGY.
This paper will explain the proliferation issues at a technical level for those so inclined. http://www.torium.se/res/Documents/9_1kang.pdf
@georgeherbert
First off, 233-U bred from thorium is generally contaminated with 232-U, which screws with the electronics one would use for weapons. It’s actually the most cited obstacle to proliferation via 233-U.
Second, removing 233-U from the core at anything like a high rate will shut down your reactor. The idea is to make fissionable isotopes more valuable as power than weapons, which LFTR does.