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Thorium Reactors: Nuclear Redemption or Nuclear Hazard?

Could thorium be the faltering nuclear industry’s salvation — or is it a mirage? Is the U.S. missing an immense energy opportunity?

“We should be trying our best to develop the use of thorium,” former UN weapons inspector Hans Blix recently told BBC News. “I am told that thorium will be safer in reactors – and it is almost impossible to make a bomb out of thorium.”

Thorium is up to 200 times more energy dense than uranium and as common as lead. It could be a safer, cheaper nuclear fuel, GTM reported shortly after the 2011 Fukushima disaster: “China, India, Japan, France, Russia and the U.S. are all currently developing thorium-based reactors.”

Yet thorium-based nuclear power is still a hypothesis. Maybe because, Blix noted, besides the technical obstacles, there is a multi-billion dollar uranium-based nuclear industry “backed by vested interests.”

“Uranium, which is much better for making bombs, took over the stage” during World War II, explained SuperFuel author and thorium advocate Richard Martin on NPR’s Science Friday last year. Thorium was “pushed aside.”

It could be coming back. India, with the world’s biggest thorium resource, is committed to a program using “thorium compounds as breeder fuel to produce more uranium.” It plans to get “30 percent of its electricity from thorium reactors by 2050,” according to the November Economist.

China is developing “a next-generation reactor which its supporters say will enable thorium to be used much more safely than uranium,” BBC News said. And Norway’s Thor Energy is developing thorium technology through an “evolutionary approach” that will use thorium “in existing reactors together with uranium or plutonium.”

TerraPower, backed by Microsoft billionaires Bill Gates and Nathan Myhrvold, is a uranium-based small modular reactor (SMR) technology that reuses stockpiled nuclear waste.  The NY Times recently called it  “a very long term bet.”

Thorium technologies fit the nuclear industry’s move toward SMRs. Flibe Energy’s modular liquid-fluoride thorium reactor (LFTR) and “known thorium reserves” could supply “advanced society for many thousands of years,” according to a Flibe fact sheet.

LFTR’s external nuclear chain reaction also reuses stockpiled nuclear waste and safely eliminates the need for containment vessels because it shuts down automatically if there is a disruption. Thorium is cheaper and more efficient than uranium and LFTR modular reactors would be mass produced cost effectively, use less water, and provide waste heat and marketable byproducts.

Nobel laureate and former CERN Director Carlo Rubbia leads advocacy for an alternative accelerator-driven system (ADS) thorium technology that would give thorium “absolute pre-eminence” over other fuels, Rubbia said recently. Norwegian nuclear industry player Aker Solutions purchased Rubbia’s patents earlier this year and is investing $1.8 billion in their development.  

ADS could, according to Jefferson Laboratory Associate Director Andrew Hutton, “transform the landscape of the waste-disposal and storage problem.”  It is minimally radioactive, shuts down automatically, and offers “proliferation resistance.”

Thorium does not resolve nuclear power’s proliferation and waste issues, Institute for Energy and Environmental Research President Dr. Arjun Makhijani responded to Martin on the NPR program last year. Pure uranium-233 can be derived from the molten salt coming out of thorium reactors “which is easier to make bombs with than plutonium.” And the waste, Makhijani added, contains carcinogenic radioactive materials.

Deriving U-233, Martin said, is “virtually impossible, even for a sophisticated nuclear power lab, much less for a rogue nation, or terrorist group.” Thorium reactors do create waste, he acknowledged. But they use stockpiled waste as a starter, their waste is “tenths of a percent of the comparable volume from a conventional reactor,” and its half-life is “a few hundred years as opposed to tens of thousands of years.”

Dr. Alvin Weinberg, the “guru” of thorium nuclear technology, called it a “Faustian bargain” and said it was “a great energy source, but you’ve got to worry about proliferation and waste,” Makhijani replied.

“OK, you have concerns about thorium-based nuclear power,” Martin replied. “But what is the answer? Renewables are not going to solve our problem in the time scales that we need it, in the next 30 to 50 years.” The choice is between “an innovative form of nuclear power” and “a three-degree-Celsius rise in global temperatures over the next 50 years.”

My reactor is free. It’s in the sky, 93 million miles away. You can store its energy in molten salt. It is being done today. You can generate electricity for 24 hours a day,” Makhijani answered.

Even with extensive investment in thorium technology, he said, it would take ten years to build the infrastructure and ten more to put regulation in place. “I did an honest, unbiased look, not thinking we could do renewable energy. And I found out that my hunch was wrong: We can do 100 percent renewable energy.”

Thorium will not happen in the United States “because of the licensing issues,” Martin agreed. It is happening in China, India, and Western Europe. “The thorium revival is inevitable. The question is whether the United States is going to be a follower or a leader.”

“Let them raise venture capital and do it,” said Vermont Law School Institute for Energy and the Environment nuclear economics researcher Mark Cooper. “I have low carbon and no carbon technologies whose costs have been coming down and they can keep the lights on. In 25 years I am likely to have a whole range of cost effective ways to keep the lights on that evolve from the current set of technologies.”

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Keith Pickering's picture
Keith Pickering on December 10, 2013

The proliferation “issue” is a total red herring. Consider:

1. Makhijani’s claim that it is easier to make bombs with U-233 than plutonium is obviously false. Tens of thousands of plutonium bombs have been contstructed, compared to exactly two bombs from U-233. Both were experimental, and neither warranted a follow-up. 

2. The reason it’s a bad idea to make a bomb out of U-233 is that it is inevitably contaminated with U-232, which has hard gamma emitters in its decay chain. This makes the stuff not only VERY hazardous to work with, it also adds to bomb complexity by requiring heavy shielding for bomb electonics.

3. Even if Makhijani were right, his whole argument is a strawman. A U-233 bomb doesn’t have to be harder to build than a plutonium bomb. It just has to be harder to build than a U-235 bomb, which is the easiest bomb to make and the obvious path to first weapon. Just ask the Iranians. 

Bob Meinetz's picture
Bob Meinetz on December 10, 2013

Herman, Arjun Makhijani is one of a handful of scientists who have made a cottage industry out of anti-nuclear scaremongering. He runs the “Institute for Energy and Environmental Research” – a vanity anti-nuclear portal – and even though he has a non-nuclear degree and no experience in nuclear engineering, his diploma comes from an eminent university so the misinformation he distributes is repeated as gospel. Some examples:

1) The idea that it’s easier to make bombs out of U-233 than plutonium is flat-out wrong. Gamma radiation from a U-233 decay product makes it extremely dangerous to handle outside of a reactor vessel.  Dr. Ralph Moir of Lawrence Livermore:

The radiation associated with the thorium fuel cycle is well known and is one of the reasons it is not used in nuclear reactors, especially since hands-on fabrication of solid fuel is precluded. This radiation argues against 233U from thorium use in nuclear weapons because of the dose to workers near the explosive. The allowed time of exposure is 300 hours for a fatal dose at 232U /233U =2.4%.

2) Dr. Makhijani’s statement that thorium waste “contains carcinogenic radioactive materials” is technically correct. So does coal ash, so do banana peels. This kind of provocative nonsense has no place in science.

3) More hysterical fearmongering: “You’ve got to worry about proliferation and waste.” Well you can, but you certainly don’t have to. The United States has created 69,720 metric tons of high-level waste over the last forty years – a tiny fraction of the waste which would have been created by an energy-equivalent amount of coal – and it’s been stored safely without a single incidence of injury or contamination.

4) Makhijani’s prononcement that ““My reactor is free. It’s in the sky, 93 million miles away” represents typical renewables hyperbole, and ignores the fact that collecting sunlight and putting it to truly practical use is exhorbitantly expensive.

5) Richard Martin’s statement that thorium will not happen in the United States “because of the licensing issues” is only superficially true – it’s not a copyright license but a DOE regulatory license which is preventing domestic research. DOE puts thorium, which you can hold in your bare hand (the piece below was passed around at this year’s Thorium Energy Alliance conference) in the same classification as plutonium. Scientists like Stephen Boyd, who have petitioned the DOE to change the classification, have met a brick wall, even being informed by DOE staffers off-the-record that uranium interests are behind the licensing restrictions.

ralpph allen's picture
ralpph allen on December 10, 2013

 “”Yet thorium-based nuclear power is still a hypothesis.”


That is UNTRUE.   It was developed in the 60s and 70s in the US.  What is left is the hard core engineering development.  The Chinese are throwing hundreds of PhDs at if and hundreds of millions of dollars.  This is not a pipe dream but the solution for the worlds energy crisis.  Yes there are obstacles the oil and coal industries are against it along with the existing nuclear industry.   They pay people to spread falsehoods and disinformation  to keep any enthusiasm about this technology dampened down.  Obama got around them and shared all the information about this technology with the Chinese.  Although we will not be the world’s leader in the future but at least we may have a future with the reduced carbon.  

Nathan Wilson's picture
Nathan Wilson on December 10, 2013

It’s not so much that thorium was “pushed aside” in favor of uranium, but rather all breeder cycles were pushed aside by the once-thru cycle.  In the early days, uranium was thought to be a scarce resource, hence the early interest in spent fuel reprocessing and reactors which could “breed” more fisile material than they consume: Experimental Breeder Reactor 1 first operated in December 1951, two years before the Nautilus submarine set sail with its once-thru Light Water Reactor (Jan 1954).

The Nautilus program gave light water reactors and once-thru a head start, but it was always understood that we would switch to reprocessing and breeders as soon as the price of uranium became excessive due to resource depletion.  Breeders using uranium and thorium have been prototyped and proven to be workable, but the expensive uranium that would drive their use was always decades away.  Now we understand that Earth’s uranium resource is indeed vast.  This article by nuclear engineer James Hopf estimates that once-thru nuclear is sustainable for many hundreds of years, even at a greatly increased rate of usage.

So it is really the other concerns mentioned in the article that bring thorium back into the discussion today: environmental, political, and economic.  But with all of the advantages of LFTRs, we must remember that even today’s light water reactors are enormously safer and better for the environment than the use of fossil fuels.  And the high capacity factor (typically 90%) means that today’s nuclear can replace all fossil fuel use in electricity generation for a much lower cost than renewables with energy storage.  Unlike renewable energy whose cost varies a lot with the quality of the local resources and inevitably demands extensive and expensive transmission networks, nuclear is practical everywhere.  (Anyone who thinks solar is great no matter the price should read Gail Tverberg‘s articles.  Anyone who thinks solar is already cheap should add in the cost of energy storage and ponder the cloudy-day problem.)

Michael Keller's picture
Michael Keller on December 13, 2013

Seems to me the economics of the thorium cycle need to be better developed and explained, particularly with respect to liquid metal reactors and gas reactors. The later has used thorium in the past and can actually “burn-up” the building piles of plutonium generated by conventional water reactors.

Basically for a graphite moderated gas reactor, the Pu is chemically separated from conventional water reactor used fuel, mixed with the gas reactor fuel (a silicon carbide/graphite fuel form) and the used in the gas reactor in a “once-through” process. This type of cycle takes advantage of the great difficulty (from a practical standpoint, essentially impossible) attempting to chemically separate material from the graphite/silicon carbide fuel. From a proliferation standpoint, the weak-link is the chemical separation of the Pu from the conventional water reactor fuel, but ultimately getting rid of the Pu all together is a major plus that completely outweighs the small vulnerability. Because the gas reactor’s used fuel is so chemically stable, the used fuel is more or less ideal for permanent deep disposal in stable geological formations. 

As to the liquid metal reactors, they present a number of problematic issues from an engineering and operational standpoint. Also, as no one has actually licensed these types of reactors, it is very problematic whether or not they could pass through the regulatory gauntlet. Several gas reactors have been licensed in the US.

Geoff Thomas's picture
Geoff Thomas on December 13, 2013

To Nathan, – I have no problem with the replacement of current reactors with Thorium reactors, presumably the cost will be known when they are actually being produced, but the blanket disregard for the truth about renewables raises questions about the rest of your comment, – the price of renewables has fallen extremely, even with storage, whilst the cost of retail electricity has risen alarmingly.

As a seasoned and creative designer and supplier of Renewable energy systems which include storage, I know that there are many ways of designing such systems, which is not the case of nuclear reactor experts, and indeed not that many renewable energy experts, since the majority of Solar retailers only know grid connect Solar well, and the well educated Stand-alone experts are few.

I see may estimations of the cost of renewable with storage that use inferior or extremely expensive batteries, that don’t have any idea how to integrate the storage and don’t take into account how it can be economically integrated with the grid.

Hence all one sees is Cherry Picking by nuclear experts of Renewable costings, and also to a degree of Nuclear by Nuclear experts for example citing high capacity factors for Nuclear when the demand is not for high capacity but for great flexibility in output so as to be able to provide electricity at the peak level but throttle right back for off peak times. (- forcing the rest of the system to adapt is no better than the variability of wind or solar, so a full costing of all the variables would be much more helpful, as then the truer picture could begin to emerge.)

My opinion is that that sort of one sided thing is more motivated by personal opinion and justifying it rather than a genuine search for the truth.

I also followed your link to Gail Tverberg’s article and there was no mention of Renewable costing nor much else about renewables, I prefer link’s to not be used to waste other folk’s time, or did I miss something? – in which case what?

 I would love to see a full discussion of these important issues with folk not coming out with old discredited arguments to “prove” their point but rather just to share ideas, prices, alternatives, etc. without trying to stuff down everybody elses’ throats a one answer solution.

Then we might start to make real progress.

Keith Pickering's picture
Keith Pickering on December 13, 2013

The last time I looked (and please correct me if I’m wrong), lead-acid batteries are still the cheapest storage going — at about $150/kWh for deep cycle. Assuming 250 total cycles, storage cost per cycle comes out to 60 cents per kWh, about 10 times the cost of generating a kWh from scratch — and that’s assuming 100% roundtrip efficiency. Other battery types can get more cycles, but are also more expensive.

So if you start with an expensive intermittant generator (like PV) and add even more expensive storage to relieve the intermittancy, you get a very reliable system that is economically uncompetetive. Am I missing something here?


ralpph allen's picture
ralpph allen on December 14, 2013


“As to the liquid metal reactors, they present a number of problematic issues from an engineering and operational standpoint. Also, as no one has actually licensed these types of reactors, it is very problematic whether or not they could pass through the regulatory gauntlet.”


Yes there are engineering issues just like the development of any new nuclear reactor. So based upon your argument then any new nuclear reactor should not be developed since they “they present a number of problematic issues from an engineering and operational standpoint.”  This technology was up and running for over 10 years without a meltdown or explosion etc.  This country could send a man to the moon in 7 years but, ohhh no, nuclear reactors are just too fighting. It is exactly this attitude that will insure the US will fall to second world status.   BTW the real “gauntlet “ is the vested interests of the coal and gas industry and the Westinghouse’s of the world who want everyone to continue to use an inferior technology. They have the lobbyists and campaign contributions (bribes) to make sure that MSR is never developed hear.  


If the US wants to develop MSR then they could make sure the NRC was not allowed to drag their feet or it is replaced. MSR reactors are not the same technology and require many fewer safeguard than the LWR.  The inherent beauty of the MSR is that it cannot do a china syndrome. It cannot explode and it is resistant to proliferation. Using an agency that applies the same rules as LWR reactors that are inherently in an unstable state and where a failure is a catastrophe is a straw man argument.


The other arguments presented here are the NEW small reactors that are being developed which IMO is just taking the big reactors problems and making many smaller reactors.  Failsafe is questionable and thousands of tons of waste with a 10,000 year ½ life is still a problem .  Uranium must be mined and refined.  So what is gained by these new super duper smaller reactors but spread the problem too many more sites. 


Michael Keller's picture
Michael Keller on December 14, 2013

The problematic engineering and operational issues lie with taking the heat from the reactor and using the energy to create power without undue risk. For instance, water and liquid salts or metals do not do well if they come in contact with one another. That makes a steam cycle somewhat dicey from a power plant perspective. There are ways to reduce the risk, but such measures generally create major cost complications.

Any new technology must have a reasonable expectation of being profitable, which is a point a lot of folks (especially the government) overlook when advocating new reactors. I’d put the current group of small modular reactors in that same boat. As you have observed, they are basically miniature versions of their larger cousins and have some of the same inherent weaknesses.

I do not subscribe to the theory that the nuclear industry is overtly trying to hold back the development of new reactor technologies. I think it is more of an inherent unwillingness to think-outside-the-box which is a characteristic of a lot of engineers in the power industry. In their defense, however, the marketplace is such that most power industry firms do not have enough money lying around (thin profit margins) to explore alternatives in any great depth. The government might be helpful in that regard, but they are an extremely ponderous operation that is more prone to rewarding political contributors than providing real help to moving innovation forward.

Michael Keller's picture
Michael Keller on December 14, 2013

FYI. Might want to take a look at for an alternative nuclear approach currently under development.

ralpph allen's picture
ralpph allen on December 14, 2013

 “””For instance, water and liquid salts or metals do not do well if they come in contact with one another.””

 That is what a heat exchanger is for.  They are currently used in existing reactors and in hundreds of other applications.  This is a non issue that is solved with engineering design.  You also need to remember that MSR CANNOT have a runaway reaction since it is inherently self regulating. 

I think that you should read another article in the Energy Collective site about a liquid carbon dioxide cycle underdevelopment which is about 60% more efficient that the current steam systems.  And they require much less space.  This fits well with the smaller sized MSR designs that are being looked at. The MSR inherently smaller due to the elimination of the pressure dome and other unnecessary safety systems.   A MSR combined with the liquid carbon dioxide cycle would allow the placement of these reactors next to urban areas if not inside of them. MSR development is NOT dependent upon the liquid carbondioxide heat exchanger they are just synergistic technologies.

Cheap electricity impacts on aluminum smelting would be tremendous.  Someone needs to wake up Alcoa to this fact since the Chinese will put them out of business in 15 years.   Now multiply that by a thousand and you will soon see the industrial impacts on the US economy.  I would like to see carbon emission curbed so the we can all have a future but I would also like to see the US maintain its first world industrial power. 

Never underestimate what those in power will do to keep that power no matter what it does to our country and the world. 


Michael Keller's picture
Michael Keller on December 14, 2013

Nuclear heat exchangers (steam generators) can and do leak. That is irritating but since both fluids are water, not really that big a deal. However, for a molten metal or salt reactor, the steam side is at a sgignificantly higher pressure than the reactor side fluid. That means high pressure water from a tube leak ends up on the reactor side. Unhelpful and potentially catastrophic.

The CO2 Brayton cycle is an added complication, with the CO2 turbine partially operating in a peculiar region (gas/liquid). Not clear how well that will work from a practical standpoint. Might be easier to simply use a Helium Brayton cycle but the practical limits on metals place an upper limit on the temperature of the reactor side fluid.

Geoff Thomas's picture
Geoff Thomas on December 15, 2013

Hi Keith, you are correct about the price of lead acid, but not the cycling, – theoretically lead acid batteries, – if built for genuine deep cycling, can do 1500 of 100% cycles, – yes, 1500.

Most lead acid batteries will not handle 100% discharges very well, as the lead dissolves from the plates and is lost, but Tubular Positive lead acid will handle 80% every day, and 100% about 90 times.

At 80%, naturally you get more cycles, – app.1875.

Not knowing your price for those woeful 250 cycles batteries, it is hard for me to compare your figures, but with my updated figures, does your price reduce to app. 10 cents?

At the moment in Oz, we are paying app. 30cents/kWh for electricity, so 10 cents sounds workable.

Of course I don’t know your figures and it is only the higher quality Lead Acids that can get up towards the 1500 cycle ideal, – I usually am conservative in system design and use 1200 cycles to be safe although some companies, eg. Sonnenschein, seem to guarantee the full 1500.

My retail price for sealed Tubulars is $3.50; per a/hr for a 12 volt set, (not inc. freight etc) so that means a 500a/hr (@C10) 12 volt bank would cost $1750; and would store 6kW/hrs, – at 80% you could use 4.8kw/hrs per day, and you can just multiply all those figures to scale for bigger systems. 

Of course my price is in Australia, it would possibly be cheaper elsewhere and for quantity, but perhaps that gives us a starting point?



Robert Bernal's picture
Robert Bernal on December 15, 2013

We need to somehow rip the guts out of the established system of non scientific based regulations and fees in order to solve the twin problems of depletions and excess CO2.

How dare anybody say “we can’t do it”!


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