Why we need a Small Rugged Reactor…

This is why:

Militants in Pakistan attacked a fuel supply convoy yesterday, killing at least four, that was bound for US military facilities inside Afghanistan. Twelve tankers were set ablaze and crews struggled throughout the night to put out the fire.

What does this have to do with thorium or LFTR?

A small rugged LFTR could provide electrical energy to these bases in Afghanistan that currently rely on shipments of vulnerable petroleum. Furthermore, the high-temperature capabilities of LFTR mean that we could also synthesize hydrocarbons to fuel vehicles on site, rather than trucking them in.

How would it work?

A small LFTR unit would be brought in to a military site in the form of a few standard containers. One would hold the reactor, its fuel and blanket processing system, and the primary heat exchangers, all within a strong and sealed containment system. The fact that LFTR operates at low pressure would mean that this containment would be close-fitting to the reactor. This is very different than the containments required on today’s water-cooled reactors, where they have to accommodate the expansion of high-pressure water into steam that can happen if pressure is lost. In a LFTR, the system is at low pressure and there is no high-pressure water or other gases inside the containment. The only thing that goes in is coolant salt and the only thing that comes out is coolant salt.

This whole assembly would be lowered into a below-ground concrete bunker. The gas turbine power conversion system would be brought in and attached to the coolant salt system. Coolant salt would heat gas that would drive turbines and generate power. The gas used in the power conversion system would be air-cooled via large air intakes and outlets.

How could we generate hydrocarbons? Using the electricity from the LFTR, we crack water electrolytically to generate hydrogen and oxygen. The hydrogen is reacted with carbon (either brought in to the site or extracted from CO2 in the air) to form synthetic hydrocarbons to power vehicles and aircraft.

The fuel for the LFTR would be brought in separately from the reactor, and when it was time to leave it would be removed from the reactor first. The reactor would not be transported with fuel or blanket material onboard.

Why consider LFTR versus other designs?

LFTRs can operate at low pressures. Pressurized-water reactors can’t and gas-cooled designs like the pebble-bed reactor can’t. Low-pressure operation means you can have a compact unit with a close-fitting containment and no risk of high-pressure explosions.

Liquid-metal-cooled designs like sodium-fast reactors can also operate at low pressures, but they have reactive coolants that would be much too risky in a combat zone. You need a reactor that can take a lot of punishment and not risk a sodium fire or an supercriticality accident.

LFTRs can operate at high temperatures. This is important for generating power efficiently, but it’s even more important for making gas turbine power conversion (Brayton-cycle) and air-cooling feasible. With lower temperature reactors like water-cooled and sodium-cooled reactors, you have to use steam turbine power conversion (Rankine-cycle) and it’s really hard (not impossible, but really hard) to air-cool these systems without excessive penalty.

LFTRs are easy to fuel and keep running. Nobody wants to try to swap fuel rods or reprocess solid fuel elements in a remote environment. The liquid fuel used in LFTR can be shipped separately from the reactor. Don’t try that with a solid-fueled reactor. LFTR’s liquid-fuel is already in the right form for simple processing techniques like fluorination/reduction. Thorium in the blanket/shield of the LFTR absorbs neutron and gamma radiation while making new fuel to keep the reactor running.

LFTRs are stable and self-controlling. You don’t want a whole bunch of reactor operators trying to keep your reactor happy in a remote environment. You want a reactor that runs itself. LFTR can do that, through a strong negative temperature coefficient that makes it follow the load well, and the simple removal of xenon gas that would otherwise make changes in power level difficult. It’s the same reason why they wanted liquid-fluoride reactors for aircraft sixty years ago–they’re good at controlling themselves.

LFTRs can be protected against enemies. Liquid fuel means that “just-in-time” denaturing of the uranium-233 fuel is possible. If it looks like the bad guys are going to overrun your base, you hit a button and dump depleted uranium tetrafluoride in the core. Now no one will ever start your reactor again, and the U-233 is thoroughly denatured against any other use. (It’s always sad to trash U-233, but if the bad guys are coming, don’t you want to have the option?) Solid-fuel reactors can’t do just-in-time denaturing. You’ve got what you’ve got in the fuel and you can’t change it out in the field.

I spent two years as a civilian working at the US Army Space and Missile Defense Command, and had the privilege of working with men and women in uniform who had been over to the “sandbox”. I have talked with senior officials who have seen the problem firsthand that we face with vulnerable fuel convoys. I have talked to a general who wrote the letters to mothers and fathers telling them that their son or daughter had been killed transporting fuel through a combat zone. He had a simple question for me: would this reactor make a difference?

Yes sir, it would. It would make a big difference.



20 Replies to "Why we need a Small Rugged Reactor..."

  • don wilkins
    February 25, 2011 (11:52 am)

    Good afternoon,

    I understand that DARPA is looking into this concept. From 18 February Wired

    Buried within Darpa’s 2012 budget request under the innocuous name of “Small Rugged Reactor Technologies” is a $10 million proposal to fuel wartime Forward Operating Bases with nuclear power. It springs from an admirable impulse: to reduce the need for troops or contractors to truck down roads littered with bombs to get power onto the base. It’s time, Darpa figures, for a “self-sufficient” FOB.

    I think your proposal fits within their need

  • Jeff S.
    February 25, 2011 (5:30 pm)

    Two thoughts occured to me when reading this:

    A) How 'rugged' can we make whatever containers we ship the initial, radioactive fuel load for the reactor, which is needed for 'first fission'. (After that, you can ship non radioactive Thorium – although, unless the base is in operation for years, you won't even need that)? Looking at those pictures of burning fuel tankers, I'm left to wonder what a pleasant thing it would be to create multi-decade radioactive hotspots along a road when a truck is transporting that fuel load and hits an IED. I suppose it should at least be possible to make the container for that fuel load much, much more rugged than how we build petro tankers?

    Actually, thinking about it more. . . it's impractical to fly liquid fossil fuels in on a heavy lift helicopter, because you need so much fuel, so frequently, and the helicopter itself would be using a lot of fuel for every trip it made bringing more fuel (which might be hundreds a year).

    But, for a Rugged LFTR, since you only need to bring a load of fuel once every, what, 2-3 years potentially(?), it might make sense to just fly that initial reactor load into the base (you'd use a lot of fossil fuel for that one flight, but who cares if you only do it once per base, or once initially and then once every 2-3 years?

    Helicopters could perhaps be a lot less vulnerable than trucks, particularly if you have like tanks, gunships, and soldiers secure the position where you'll be setting up the LFTR (which, you would obviously have to do before setting up a base, anyhow, even with diesel generators).

    B) This idea is just so awesomely sci-fi – military bases with nuclear reactors that generate their own fuel from water and air. lol It sounds like something out of a video game, but could be reality in my lifetime.

  • Jim Baerg
    February 25, 2011 (8:23 pm)

    See http://www.ammoniafuelnetwork.org/ for a possible fuel to be made given an energy source such as a small LFTR. I'm not sure it is quite as environmentally benign as they claim, but it may be the best option.

    The 'Solid State Ammonia Syntheis' mentioned on the Ongoing Projects pate & the LFTR would complement each other well.

  • fireofenergy
    February 25, 2011 (9:01 pm)

    It should be reality! I'm sure it would be safer to transport the starter fuel once than the FF alternative, especially since the operations themselves may be voided almost all together in light of this "new" and urgently needed concentrated energy source…

    I believe the only other source of power that could ever replace FF's are like 50,000 sq miles of robotically mass produce solar panels made from competing and vertically integrated companies as large as present day oil companies. Needless to say, solar panels (and the billions of batteries that would also have to be mass produced by robotics) won't work under fire… And would {still} be far more expensive than LFTR.

  • atomikrabbit
    February 25, 2011 (9:49 pm)

    This idea is not new, just abandoned; about the same time as commercial nuclear power was losing favor.

    I originally licensed with a guy who operated MH-1A in the Canal Zone. http://en.wikipedia.org/wiki/Army_Nuclear_Power_P

    Nowadays the Taliban is the least of your worries – watch out for the fanatical Greenpeace tribe.

  • Jeff S.
    February 25, 2011 (10:53 pm)

    I had another thought to share, which I just remembered. . .

    A few days ago, as I was driving to work, I heard a story on the Marketplace Morning report (marketplace.org) on public radio.

    They were talking about the cost of the occupation of Afghanistan, and how it cost something like $1.2 Million *per soldier* (although, I'm pretty sure a lot of the costs don't actually have anything to do with supporting the soldiers, but you know, reporters like to break it down per soldier anyhow). Anyhow, they said that the largest single contributor to the cost was fuel – that the military was spending like $300,000 per soldier on fuel.

    I would imagine that field-deployed rugged LFTRs could bring that part of the cost down by a couple or 3 orders of magnitude.

  • Alex P.
    February 26, 2011 (3:54 am)

    "LFTRs can operate at high temperatures. This is important for generating power efficiently, but it’s even more important for making gas turbine power conversion (Brayton-cycle) and air-cooling feasible. With lower temperature reactors, you have to use steam turbine power conversion (Rankine-cycle) and it’s really hard (not impossible, but really hard) to air-cool these systems without excessive penalty."

    Are sure about this ?
    I actually believed that even with a steam turbine conversion system achieving ~ 50% of thermal efficiency (likely possible today with a LFTR having reactor temp output of ~ 700 °C) we can still cool the plants with small and economic dry cooling towers

  • P.M.Lawrence
    February 26, 2011 (4:13 am)

    I'm sceptical about the merits of generating hydrocarbons (or other carbon based fuels like methanol, CH3OH) at remote locations like that, not only because of the scale and opportunity costs of the (vulnerable) synthesising plant itself but also because of difficulties getting the feedstock. The feedstock problems would either be just moving the wrinkle in the carpet around, if the feedstock also had to be brought in from afar like fuel, or would show up in the additional plant needed to get the feedstock from the atmosphere, in the same way as the associated costs of the synthesising plant. (If it were practical to gather carbon containing feedstock locally, in a logistical and security sense, it would make more sense just to burn it in gasifiers mounted on the vehicles.)

    However, that suggestion for ammonia (NH3) has smaller problems of that sort, though still significant ones, and for greater energy density (and hazard) there's always hydrazine (NH2NH2)… Continuing that line of thought, if you're willing to accept the need to manage hazardous fuel and to use different engines, the technically simplest route to synthesising an energy store with the simplest feedstock is probably hydrogen peroxide (H2O2).

  • Jeff S.
    February 26, 2011 (9:41 am)

    @P.M. Lawrence: What if vehicles and other consumers of the fuel, captured their own emissions? Would that be feasible? You could then bring the captured exhaust gas back to the synthesis site and 'recycle' that exhaust back into fuel? You'd probably still have some loss (very few systems are perfect – you'd probably occasionally have leaks and things where you'd lose some exhaust gas), so would need some additional inputs, but perhaps if you could lower the need for new feedstock by a significant amount (say a 95% recycle rate or something), that might pretty significantly reduce the amount of transport missions necessary?

    I'm not sure, just thinking out loud here.

  • Andras
    February 26, 2011 (11:18 am)

    I have a much simpler idea: how about withdrawing the US army from Middle East and using the saved money to build LFTRs (and other advanced reactor types)?
    There was a great quote I heard somewhere: 'it's much better to utilize the energy of U-238 directly than to shoot it as bullets in order to grab much less concentrated energy resources from other nations'.

  • Robert Hargraves
    February 26, 2011 (2:15 pm)

    Emphasize the point that NO WATER supply is required for cooling a LFTR! Forsberg points out that an open cycle air Brayton turbine will suffice.

    The requirement for carbon-bearing feedstocks for producing methanol, diesel, or gasoline might be bypassed by extracting CO2 from air — Project Green Freedom.

  • Andrew Jaremko
    February 26, 2011 (2:18 pm)

    We need this just as much for disaster and emergency relief as for war – maybe even more so. Bring on the World Disaster Relief Society, with the Relief Brigade of volunteers from all nations, bringing succor and assistance. And maybe even leaving reactors behind to continue serving the communities. :D Maybe a little more seriously – air cooled reactors are perfect, since water is precious, and water purification might be just as important as transport fuel generation.

  • Yordan Georgiev
    February 27, 2011 (2:21 pm)

    If USA would have started the LFTRs development just 5 years ago in a Manhattan like program , not troops would have been needed in Irak or elsewhere.
    Imagine a 10 factories producing standard 50 MW modules of LFTRs per day and doubling their output each year … I just READ that USA's Defense investments in science and technology are 20% bigger than the investments of the whole Germany ( all the industries + government ) …

    For me the biggest failure of nuclear is the fact that they have not involve the biggest energy player – the oil industry …, which is also twice as valid for the oil giants – they should have combined nuclear with hydrocarbons production years ago … it would have provided them alternative to the price spikes inducted by unstable political regions …
    Anyway pragmatic China, starting to produce cheaper hydrocarbons from LFTRs or why not even fusion would probably be the first wake-up call …

  • Jeff S.
    February 27, 2011 (8:01 pm)

    @Yordan Georgiev,

    I fail to see what LFTR has to do with us being in Iraq or not. . . particularly 5 years ago. We were *already in Iraq* 5 years ago. If you think Iraq was about oil (which I think history and facts clearly dispel that argument, but let's assume that is true for the sake of discussion), we would have needed to have started up LFTR development about 15-20 years ago for it to have prevented us from going to Iraq.

    But, moving away from political argument. . . you made another comment, "they should have combined nuclear with hydrocarbons production years ago … it would have provided them alternative to the price spikes inducted by unstable political regions", unfortunately, the way the world oil markets work, they actually profit a LOT from such political instability.

    Think of it this way – if I'm producing oil from any other region than the affected regions (say the Gulf of Mexico, Alaska, the North Sea, Saudi Arabia, UAE, Dubai, etc), I sell MORE OIL at a HIGHER PRICE when unrest in Libya, Nigeria, Iraq, etc forces the price of oil up – everyone gets to sell their oil at the new 'higher' price, even if their own production is not interrupted.

    So, why would the oil companies want to reduce price volatility again? Every time a politically unstable nation has a crisis, unless they happen to be the oil company(ies) doing business in that particular nation, their CEO's and VP's are probably popping champagne corks, and planning how to their Christmas bonuses that year.

  • Roger Maddrell
    March 1, 2011 (9:11 am)

    This proposal highlights the wonderful adaptability of LFTR. That it can make sense in such a challenging environment such as Iraq or Afghanistan makes me think it would be a walk in the park using it in a peaceful setting.

    I groan when I look at the history of nuclear development and the current sovereign vulnerability of the US in particular which continues to rely so heavily on oil imports from regions where most of the population either regard her with deep suspicion and resentment or see her outrightly as the "Great Satan" and would like nothing more than to bring her to her knees at the first opportunity.

    Failure to develop LFTR decades ago in order to strengthen US independence from Middle East oil strikes me as either one of the greatest failures of her leaders or chilling proof of the West's collective vulnerability to the power and self interest of LFTR's competitors; perhaps both.

    I wouldn't necessarily say that the current US military actions in Iraq and Afghanistan are all about oil but it sure is a part of it. How much more freedom to act would she have if she could brush off any threat to turn off her oil supply.

    It may take 12 years for a walnut tree to start producing walnuts but to put off planting or not bother at all because it will take so long to get walnuts is absurd. It may take time to develop and deploy LFTR on a significant scale but looking at how vulnerable the US is now, I'm astonished that an effort on the scale of the Manhattan Project scale effort isn't currently being made right now. The threat is just as real.

  • Jagdish
    March 1, 2011 (11:23 pm)

    Wrong reasons for a right idea.If money was spent on development of nuclear power (including LFTR), and on production of synthetic fuel, the US would not be dependent on imported fuel. It would have technology to offer for profit or friendship. Afghanistan is in middle of Muslim extremist regions and no one should have to be there without locals approving.

  • David Phillips
    March 6, 2011 (1:32 pm)


    One of the reasons for using this right idea in a wrong area is to get it started. Development funding and licensing issues are huge barriers to commercial use. However a military program has other development tracks that allow the technology to mature in current engineering and later to be used commercially. So we have the immediate benefit of reduced risk on the battle field while showing a reason for coming off the battle field in the future.

  • Luc Hansen
    March 13, 2011 (6:32 am)

    Why not do the world a favour and just bring your troops home?

  • kevinv
    March 13, 2011 (10:57 am)

    One of the best reasons for starting a program is inevitability. The fact that you can burn U-233 in these reactors, which seems to be the the best way if not the only way to get rid of it, makes the use of LFTR's inevitable.

    Let's get on with it.

  • Kevin
    March 13, 2011 (10:45 pm)


    How would the Protactinium be removed from the salt in a forward operating base? Do you really think that the hot chemistry can be performed in the field?


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