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By Robert Rapier on Sep 10, 2012 with 22 responses

Responses to Thorium Reactor Story

Tags: thorium

9/16/11 Update: New story from Wired — Thorium potential ‘overstated’ says government report

Following last week’s R-Squared Energy TV episode that discussed thorium nuclear reactors, there were a number of comments and emails from readers that added a lot of clarity to the discussion. I want to highlight some of those comments, because as I had indicated that was definitely outside of my area of expertise.

My general feeling is that there are some technical challenges that have been downplayed, and I compared the situation to that of hemp. Advocates of hemp for fuel frequently suggest that were it not for government regulations against it, hemp could be a major raw material for biofuels for the U.S. My comment to that is always that hemp is legal to grow in many countries, and yet is not utilized in those countries for biofuels. Thus, there are challenges regarding hemp other than simply government regulations against it.

Nevertheless, many readers provided very good complementary information on the topic of thorium reactors, and I share three of those comments and one email below.

First comment:

The fuel fabrication for thorium reactors is not costly.  Thorium oxide mined from the earth can be put straight into a liquid fluoride thorium reactor (LFTR).  Thorium is about 4 times more abundant that uranium 238.  Thorium is about as abundant as lead.

A LFTR works by converting the fertile thorium into fissionable (burnable) uranium.  Both the thorium and uranium are mixed with molten salts that allows the reactor to pump the ‘fuel’ around for processing and heat transfer.

A LFTR has many advantages over a light water reactor; however, there are  two main features that contribute to its safety:  1) since the ‘fuel’ is liquid, the reactor is ‘self-regulating’.  As the reactor heats up the molten salt expands and moves the uranium away from the core; thereby slowing the reaction. 2) liquid fuel allows a ‘safety plug’ (made of the same ‘fuel’ salt with a fan blowing across it to keep it solid) to be installed on the reactor.  In the event that  the pump circulating the fuel stops or the reactor needs to be shutdown, the fan stops blowing, the molten salt melts the ‘plug’ and drains into a tank designed for maximum heat transfer.  This ‘drain plug’ is walk away safe since it depends upon gravity to work.

This is a great advantage over light water reactors.  They all require some kind of active cooling and hence some kind of generator to run the cooling.  This is what failed at Fukushima.  The tsunami wiped out all of the back up generators that would have cooled the solid fuel uranium.   A LFTR in the same scenario as Fukushima would have had no problems.  The molten salt fuel would have drained into their tanks and solidified back to crystal salt in the tanks.  Once the danger was over, the Japanese could have heated the drain tanks and pumped the molten salt back into the reactor to restart it.  This technology was demonstrated at Oak Ridge National Labs in 1965 – 1969.  At Oak Ridge the technicians would shut off the reactor over the weekends this way and restart it on Monday.

I recommend that you read Dr. Richard Hargraves book called “THORIUM: energy cheaper than coal.”  The book was published just last month.  He runs through all of the competing energy production technologies, prices them, and discusses how thorium can be cheaper than all of them.  The book’s website is  It is available on Amazon.

Second comment:

AFAICT, there are numerous challenges in building high temperature molten salt reactors, and this is why we are unlikely to see them commercialised – at least not in a large scale – anytime soon. But I’m fairly sure that if the engineering hurdles can be overcome, LFTR-style designs hold an enormous promise, mainly because of the strongly negative thermal coefficient of reactivity, which means they can be easily throttled to match demand. They might work extremely well as a complement to solar and wind; they could be cranked up nighttime and during calm weather and idled whenever solar and wind are plentiful.

Actually, a liquid fuel reactor could be run on uranium as well. It’s more about the reactor design than about the fuel. I think the main reason they did not get commercialised in the past was that the whole concept was so different from all previous reactor designs that none of the conventional nuclear reactor expertise was any good for them and that to be viable they would have needed to make a couple of material science breakthroughs to prevent corrosion of the reactor chamber structures at the sustained high temperatures. I am all for continued research and development in nuclear power and LFTR is one of the most exciting ideas that are floating around, and certainly one of the most radical ideas that might actually become reality. But it’s still in its early stages, and huge showstopper issues might still come up.

Third comment:

After reading a bunch of pro Thorium articles a year or so back, I also wondered why it hasn’t been commercially successful if it’s truly as superior as proponents claim (and has been fairly well understood for nearly 50 years). So I did a very quick google and easily found a slew of articles that seem to directly contradict many of the claims made by the pro-Thorium crowd. Here is one example from a very well respected organization
I’d like to hear a true Thorium expert respond to the claims in this document.

The other thing is that a significant percentage of the pro-Thorium articles seemed to include a very faint but detectable whiff of conspiracy to them. Many of them included verbage that implied ‘If only big-oil/big-uranium/government/the UN/etc would stop suppressing Thorium we’d all have clean nuclear energy that is nearly too cheap to meter’. That type of stuff always sets my baloney detector into high gear.

I really do have an open mind about it. I appreciate there absolutely is great potential there. I just would like to hear the response to critics, and of course, I’d really like to see the results from a functional, near-industrial sized reactor before I hop fully on board. I mean hasn’t India been pursuing commercial Thorium power for years with very limited success?

Email received:

Three quick thoughts about thorium development:

1. Your comparison to hemp advocates stung a little (I’m a thorium advocate), but I have to admit, it was apropos. Still, there is a huge difference in regulation between biomass and nuclear of any sort in this country.

2. Thorium fuel processing into thorium oxide is indeed expensive, but that is only for solid-fueled reactors. Most thorium advocates (at least as I have observed them) are pushing for liquid-fueled thorium reactors, a type of molten salt reactor. These don’t need thorium oxide, just plain old thorium. Of course they do need a neutron source to get them going, which is something of a challenge.

3. There are good reasons to believe that uranium will get very expensive in the next few years. The world hasn’t produced as much uranium as we consume in probably 40 years because we are still drawing down inventories of it from the 40s and 50s. Those will probably deplete before too long, and the price of uranium will jump accordingly. Of course the fuel inputs are such a small part of the cost of nuclear power that this would not be analogous to oil or coal jumping substantially in price.

Link to Original Article: Thorium Reactor Follow-up

By Robert Rapier

  1. By Walter Sobchak on September 10, 2012 at 9:17 pm

    The 3rd comment above states that the linked paper is from a ” a very well respected organization”. The organization in question is the “Physicians for Social Responsibility” which is a leftist anti-nuclear political organization that is fronted by a pediatrician Helen Caldecott of Australia. The organization has no institutional expertise in nuclear issues, and no objectivity.  Personally, I will not waste my time reading anything they publish.

  2. By brendan on September 10, 2012 at 9:50 pm

    That IEER “fact sheet” is just the usual anti-nuclear propaganda hatchet job. It has no credibility and plays very loosely with a paucity of truth

    Here are a couple of rebuttals and

  3. By Lyn on September 11, 2012 at 11:41 pm

    Your comment about hemp being approved but not utilised in other countries is correct, but only to a point.  Hemp is legal to grow in Australia but because of public perception that hemp is marijuana, it has been difficult to source appropriate investors.  In addition, our government has placed costly and onerous conditions on growing hemp, such that farmers cannot yet find it viable.

    The public perception issue has been widely quoted as stemming from US prohibition laws.  It is odd that, even though US farmers cannot grow hemp, food products made from hemp seeds are widely available in the US – most of it imported from Canada.

    In countries where hemp is legally grown, there is definite industry growth and you will no longer be able to make your (unsubstantiated) comparison.  Hemp is being used for food, fibre and building materials.  It is NOT marijuana.

    Perhaps a little more diligence by you and others in learning the reasons why hemp is not yet widely used would cease the perpetuation of the notion that hemp is marijuana and allow the industry to flouish.

    • By Robert Rapier on September 11, 2012 at 11:55 pm

      Perhaps a little more diligence by you and others in learning the reasons why hemp is not yet widely used would cease the perpetuation of the notion that hemp is marijuana and allow the industry to flouish.

      First, I never mentioned hemp in relation to marijuana. I don’t know why you would suggest that. Second, hemp is legal to grow in numerous countries, but is not used as biofuel. Hence my point that there is more to hemp not catching on as a fuel than just being frowned upon. I am suggesting that there are technical challenges in economically converting it to fuel.


      • By Cyril R. on September 12, 2012 at 5:05 am

        Hi Robert. In my country, and most countries in fact, it is ILLEGAL to build a nuclear plant. In countries where it is not illegal, it is a highly bureaucratic and burdenous long term undertaking. It’s important to realise this crucial difference. I can grow hemp in my garden. But if I have an idea for a nuclear reactor – not to mention that it is radically different than the encumbent water cooled reactor – then it will be very hard for me to get started. For any startup, you need a dozen lawyers, and millions of dollars, just to pay the regulators, safety studies, etc. before you can put any shovel in the ground. Then you need the lawyers again for litigation, as chances are people won’t like the nuclear reactor in their backyard, or anyone’s backyard. It is an environment that, sadly, that discourages innovation, including innovation that leads to improved safety, ironically.


        Just look at the new improved, passive light water reactors. They are safer and simpler than previous light water reactors. And very similar. Yet it took 30 years for Westinghouse to get started building their AP1000 projects in the USA. (the tech was based on the AP600 where they spent hundreds of millions in R&D and licensing, and the AP1000 wasn’t much different from the AP600!!).

        This spells bad news for any nuclear startup with a radically new reactor design. You just won’t get any financing from any private groups, because it takes too long for the money to flow back.

  4. By Cyril R. on September 12, 2012 at 4:54 am

    Hi Robert. I just wanted to point out that we have been writing a Wiki article on LFTR. It has a lot of information regarding the design challenges and advantages. I tried to write as objectively, factually and comprehensively as I could, and I think the Wiki article, though still a “work in progress” helps inform and dispell many myths that we see from anti-nuclear interests such as IEER, Greenpeace, etc.


    Anyway, here’s the article:

  5. By Cyril R. on September 12, 2012 at 4:58 am

    As for the IEER “fact sheet” here’s what Alexander Cannara and Kirk Sorensen, both thorium experts, have to say:

  6. By notKit P on September 12, 2012 at 10:36 am

    Cyril if I understand RR point is that if something is a good idea they will try in someplace to find out if it is good idea. Many different kinds of reactors have been built in the US, Russia, UK, Canada, France, China and India.


    In the US, we have a process to build prototype reactors to prove design that cuts out a lot of the paper work. We have a friendly place, the high desert in Idaho. That is where the navy qualified me to supervisor the operation nuke propulsion plants.


    “Yet it took 30 years for Westinghouse to get started building their AP1000 projects in the USA. ”


    The problem was that no one in the US was buying reactors. It design to making electricity for new reactors is 10 years. That is being proven in China now and it is what we did in the US 50 years ago. It takes about two years to develop conceptual design into a design that can be submitted as a license application. Detailed design takes three years. Construction takes 5 years.


    The reason no new nukes were building nukes in the US was the price of coal and natural gas. As the price of fossil fuel increased and the operating cost of nukes decreased, US nuke plants became cash cows.


    “You just won’t get any financing from any private groups, because it takes too long for the money to flow back.”


    That is true but that is not how it works. The cost of producing power is paid by customers. Every year a state PUC decides on the rates. If operators of nuke plants are giving money back while fossil is asking for more money, some states said that it might be a good idea to invest some of that money in new reactors as a hedge against the cost of fossil fuels. This is called construction work in progress.


    The PUC have been very clear about CWIP funds. If the customers take the risk, they get the benefits. If you do not manage the project well, stockholders are going to be penalized.

    • By Cyril R. on September 12, 2012 at 11:32 am

      It was tried in the USA, At Oak Ridge. The Molten Salt Reactor Experiment. It worked fine, so ORNL was working on a large commercial reactor. But then the budget was cut and the US government send all the remaining budget to fast sodium reactors. No money left for a molten salt reactor…

      The funding was cut at a most critical time. They had the basic tech developed, and were working on a large power generating prototype that would have attracted more attention from utilities.

      Sadly, MSRs are the “path taken but abandoned”.


      Please see this link for more info.


      • By notKit P on September 13, 2012 at 9:06 am

        ORNL is another one of those nuke friendly sites. So is Handford nut it is in a left coast state which means the governors and senators will fight anything nuclear. I would still be living in Richland if the state was nuke business friendly.


        FFTR would be perfect for conversion to a medical isotopes production facility saving the government the cost of decommissioning. The problem is with nuclear is not the backyard. The problems is big cities farther away. Even if you work in a service industry, when you live in energy or agriculture based you talk to your customers. In big cities, electricity comes from the wall and food comes from a restaurant. The production of the necessities in life are now abstract instead of familiar. Nuclear power is dangerous and coal is dirty because that is what your local journalist thought that is what you wanted to read. Pesticides have high risk and low benefit for producing food not because a farmer told you but that is what the NYT prints.

  7. By Russ Finley on September 12, 2012 at 9:41 pm

    Passive cooling designs are pretty basic for conventional reactors. The AP1000 has a water tank above it that passively drains down to cool the core for 72 hours. Which is enough time to top the tanks off again with tanker trucks, or pumps, had power been lost. To cool it longer they would simply need more water higher than the reactor. Everybody seemed to think 72 hours would be plenty of time to get more cooling water pumped into the tanks. Such a system would have prevented the Fukushima incident.


    • By Cyril R. on September 13, 2012 at 9:49 am

      Hi Russ. I’ve suggested an even simpler design for a molten salt reactor decay heat & passive containment cooling. It is basically the same as the AP1000 containment, except there’s no internal pressure or dependence on containment leak tightness for the cooling, as the cooling internally is radiative (thermal). Also there’s no reservoir to refill. So the cooling will still work if the containment is turned to Swiss cheese, unlike the AP1000.


      Here’s a concept sketch:


    • By Govindan on September 14, 2012 at 3:09 am

      To avoid cooling problems  one expert wrote to use steam turbines instead  of electric motors  to run the  cooling pumps. I feel this a brilliant suggestion. After shunting down the plant, there will be  enough steam  in the reactor to run the turbine pumps for  about three days.

      • By notKit P on September 14, 2012 at 10:43 am

        “I feel this a brilliant suggestion.”


        Every nuke plant I have worked at uses small steam turbines as a diverse and redundant safety systems  In Japan they  worked fine until the batteries supplying DC control power went dead.  Portable generators were staged on site but damage from the earthquake delayed getting power restored.



  8. By notKit P on September 13, 2012 at 9:29 pm

    Passive cooling for accident mitigation limits the power output of the reactor. All large reactors have some form of passive cooling to keep the core cooled in the first few second after a loss of coolant accident until the diesels start and safety injection pumps deliver full flow in 30 seconds.


    What is often overlooked in discussions of cool technologies is the goal is to produce electricity. Reactors scale up very nicely. The US reactor producing the most power is now:


    “The upgrade will increase Grand Gulf’s production by more than 13 percent, or approximately 178 MWe, bringing total (gross) output of the General Electric boiling water reactor to over 1,500 MWe.”


    The AP1000 has to reject approximately 10 MW after an accident passively but also during a normal cool down with RHR pumps.


    Larger 1600 MWe would have to eject approximately 16 MW.


    Pumps and heat exchangers is how we do it. Using heat loss through the steel containment is an interesting concept not a better way of doing it.

    • By Uzza on September 22, 2012 at 6:59 am

      For solid fueled reactors passive cooling does indeed leech energy from the core, since the core itself is designed to permit radiating enough energy to allow for passive cooling.

      But in a molten salt reactor, the passive cooling is in a completely separate system that is only used when it is needed, i.e. when the fuel drains to the drain tank. No energy is lost cooling stuff when it isn’t needed.

  9. By Govindan on September 14, 2012 at 3:25 am

     I  think Accelerator Driven Sub-Critical Systems (ADS)  nuclear reactor is better than LFTR

    The best thing should be to develop Accelerator Driven Sub-Critical Systems (ADS)  nuclear reactor. .Development of Accelerator Driven Sub-Critical Systems (ADS)  nuclear reactor is the latest addition to the Indian nuclear programme. ADS can provide a strong technology base for large scale thorium utilisation. As a first step towards realisation of ADS, DAE has launched  to development of proton injector. To carry out experimental studies on sub-critical assemblies, a 14 MeV neutron generator has also  been upgraded with a higher current ion source. 
    Norway and  Australia  are also interested to  develop ADS as they have large quantity of thorium  like India.

    “Accelerator Driven Sub-critical Nuclear Reactors for Safe Energy Production and Nuclear Waste Incineration[1] 
    S.R. Hashemi-Nezhad[2] “
     School of Physics, A28, University of Sydney, NSW 2006, Australia

    S.R. Hashemi-Nezhad’s view

    Solution to the nuclear safety issue
    An ADS will operate under sub-critical conditions (e.g , keff  = 0.95-0.98) and the operation of the reactor is directly linked to the operation of the attached accelerator which provides a high energy ion beam to produce spallation neutrons. These neutrons keep the ADS operational i.e. the system remains operational as long as the accelerator functions. The proton beam plays the role of the control bars in the current reactor, with the difference that if it fails, the fission reaction in the system dies out and it can never lead to overheating.
    There are many ways to shutdown an accelerator (an electric device) or divert its beam away from the sub-critical reactor core.

    3.3 “Thorium Furnaces”
    Our group believes that Australia can become technically and commercially involved in a future commerce in modular ADS/Thorium reactors for both power generation alone in “greenfield” sites and for high level nuclear waste disposal at “brownfield sites” – those existing power stations where demand dictates increased capacity but where accumulating waste is a problem. We believe that Australians can certainly develop and construct the high flux accelerator component. We are negotiating to form a strategic alliance with an experienced European reactor constructor to assist with the reactor component.

    • By Cyril R. on September 14, 2012 at 10:57 am

      The issue with reactors is not shutting them down. Fukushima shut down just fine. LFTRs will be even safer in that respect because they don’t need control rods to stay below the material failure temperatures.


      The issue is decay heat & containment. ADS does nothing about decay heat. It adds cost and complexity which is not good for decay heat & containment safety. It tries to solve a problem, very expensively with an accellerator, that doesn’t exist.

      Any passive decay heat removal system that ADS has, LFTR can do better because it’s simpler.

      • By Cyril R. on September 14, 2012 at 10:59 am

        They had the steam driven turbines, but they forgot to stick a generator to them. So that they could have generated some electricity for seawater pumps/ultimate heat sink.

        More importantly though, the plant simply didn’t have sufficient design basis tsunami protection. 100 years ago a 23 meter tsunami hit Japan. The Fukushima designers and regulators made a big mistake.

    • By notKit P on September 14, 2012 at 11:25 am

      “The proton beam plays the role of the control bars in the current reactor, with the difference that if it fails, the fission reaction in the system dies out and it can never lead to overheating. ”


      Overheating is caused by decay of fission products not the continuation of fission. The amount of decay heat at shutdown is proportional to power.


      Safety is about not exposing people to fission products. From a heat transfer perspective one minute we are transferring 3000 MW thermal to through a turbine. After the reactor shuts down e next we are transferring 30 MW thermal either bypassing the turbine and sending the steam to condenser.


      During an accident, reactor coolant is released to the containment. If we put water back into the reactor fast enough, there will be little damage to the core and few fission products released..


      A LWR with a containment building is walk away safe even if an air plane hits it. It takes time to melt down the reactor. There is plenty of time to prevent exposing people to fission products be evacuation. At both TMI and Japan, no one was exposed to hazardous levels of fission products.


      In any case, for a given about of fission products you have to show how you protect the public. This is not done with marketing brochures, books, or grand student publications.

  10. By P.M.Lawrence on September 15, 2012 at 7:56 pm

    One inspiration for the work on molten salt reactors was what happened with the earlier aqueous homogeneous nuclear reactors, which also used fuels as salts dissolved in liquid, typically heavy water (sometimes even without fuel enrichment) or light water (if the fuel was enriched enough). These didn’t need separate arrangements for moderators, and they were small, simple, cheap and effective – right up until corrosion effects augmented by the radiation made them break down, what with the water and salts producing so many chemically reactive materials. They were useful enough for certain experiments to determine neutron absorption cross-sections etc., but in themselves they couldn’t be used operationally.

    This inspired the idea of using molten salts directly without any additional solvent, so that some combination without those disadvantages could be sought. But the thought has occurred to me that there is yet another possibility: fluidisation. If you blow a stream of suitable gas through a suitable powder, it will start to behave like a fluid – like a liquid at certain flow rates and like a gas at others. So, would a fluidised analogue of an aqueous homogeneous nuclear reactor work, say with carbon monoxide fluidising sugar charcoal that also contained a powdered form of fuel? I can see some potential problem areas straight away, like the powders clumping or the fuel separating, but it certainly appears that this would bypass the corrosion issues while still providing moderation material, and maybe the different kinds of problem would be more manageable.

  11. By jj on October 11, 2012 at 11:41 pm

    To address comment directly.  Variations on the wave front design seem the most interesting. See the los almos small reactor.   Thorium reactors need and eriched uraniun or plutonium starter. These starters however do not necessarily represent a proliferation threat – the Uranium can be are consumed rapidly.  Thorium is an efficent adsorber and  the fissil product is consumed as rapidly as it is produced.   The reactor can be designed so that is no accumulation of fissil material.  Indeed there is very little radoacdtive wast.  In a current Uranium reactor 99% of the uranium is wasted in the spent fule which has long lived products.  Thorium is 99% converted to fissel materil which is all consumed radioactive wast is much less (1%) and relatively slort lived.   There may be unforseen problems – but why abandon all thought and all possiblaity of action? People are also very good at solving problems if given a chance.   

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