Nuclear Reactors Get Small

Steve Martin was ahead of his time when he told us “Let’s get small!” While you usually think of a nuclear reactor as a big affair, there’s a new trend towards making small microreactors to produce power where needed instead of large centralized generation facilities. The U.S. Department of Energy has a video about the topic, you can watch below.

You probably learned in science class how a basic nuclear fission reactor works. Nuclear fuel produces heat from fission while a moderator like water prevents it from melting down both by cooling the reactor and slowing down neutrons. Control rods further slow down the reaction or — if you pull them out — speed it up. Heat creates steam (either directly or indirectly) and the steam turns a conventional electric generator that is no more high tech than it ever has been.

One of the key benefits of a small reactor is that it is transportable. That means you can build them in an efficient central location and move them where you need them. Generally, these new reactors have passive safety systems, automated control systems, and can operate for a decade without new fuel. While there are several technologies in development, the Department of Energy says that the earliest available microreactors will use gas or heat-pipe cooling. Liquid metal and molten salt systems are also promising but probably will arrive later.

Of course, small is a relative term. These reactors produce from 1 to 20 megawatts of power and look like they might fit on a large truck. We don’t expect a nuclear-powered laptop anytime in the near future.

Maybe these new reactors will benefit from additive manufacturing. Of course, submarines and naval surface ships have had tiny and reliable reactors for a long time. One obvious application for a transportable reactor is to power a means of transportation.


92 thoughts on “Nuclear Reactors Get Small

      1. According to the wikipedia page, a plane flew with an operational reactor in it (a number of times), but it was to test the shielding and it wasn’t actually powering the aircraft.

      2. A B-36 made 47 flights carrying a fission reactor but they were only to test radiation shielding. The reactor was never equipped to power anything. There was a massive lead shield installed between the reactor compartment and the flight deck. A special underground bunker was built to house the reactor. The B-36 was positioned over it then doors on the bottom of the plane and the bunker lid opened so the reactor could be lifted up and locked in place.

    1. They were able to keep the weight down by leaving off reactor shielding. The cockpit was shielded but anything within a fairly large distance would get a lethal dose of radiation.

      According to James Mahaffey in “Atomic Awakening” a Convair B-36 was converted to (partial) atomic power and redesignated the NB-36H. It flew 43 test missions over the desert between Texas and California.

      The Georgia Nuclear Aircraft Laboratory (GNAL) was built in Northern Georgia for testing materials under high radiation environments. The GNAL had a network of train tracks that could move materials between several test areas. One of the areas had an unshielded 10MW reactor that could be raised out of a shaft to a height of 10 feet within the test area. GNAL has been (mostly) cleaned up and is now a state park.

    1. It’s actually far better to build one that truckbed size, so you can have it power a neighborhood. Cost of everything goes down, stupidly reliable, it’s just getting over the whole “there’s a nuclear power plant in my neighborhood? screw you!” response from the average person.

        1. > My only experience with modern American suburbia is from popular media

          In fairness, this is the same popular media that thinks you can hack into a computer system by typing “override” at the password prompt.

      1. I grew up in Florida near the St Lucie nuclear plant. At some point Florida Power & Light started sending out annual pamphlets to our neighborhood explaining that we were within the inner evacuation zone and that we should all be prepared to evacuate if the sirens started going off.

        Of course, nobody really cared that much.

      2. I rather have one in my backyard and leave the power companies out of it. If it breaks, I can tap a neighbor’s until mine is fixed or a replacement is installed.

    2. A foolish perspective because nuclear reactors currently too dangerous to just be handing out to just anyone. However, these look like the right size for powering shipping boats and cruise ships. If you are unaware, they are massive polluters because there is no regulation to how much they are allowed to pollute due to the nature of them always being out at sea.

      1. You are wrong. There are regulations about emissions from commercial ships. Look it up. Ships move cargo with the most efficient use of fuel. One tenth the pollution of rail and about 1% of road transport.

          1. > I doubt If electric rail has emissions lower than modern ships. Their electricity is generated somewhere.

            Sure. And it’s increasingly generated in non-carbon-emmiting ways.

            Such a false equavalency…

            French High Speed electric trains claim 3.2g of CO2 per kilometer travelled.
            To be compared with 205g for a typical car, or 168g for a domestic flight.

    1. Radioisotope Thermal Generator. At best they produce a few hundred watts and after 10~15 years the output starts dropping off. The Voyager probes’ RTGs are just about done, barely able to power their lowest power instruments and slow transmit a trickle of data from them.

      Originally these generators were called SNAP. Systems Nuclear Auxiliary Power or System for Nuclear Auxiliary Power.

      One of the main locations where RTGs are built is the INEL in Idaho.

      Why RTGs aren’t used (often) for Earth based power is due to stupid people. The USSR used them to power remote, automated light houses and radio beacons. There were several incidents of hunters stealing the RTGs, peeling off the shielding and using the heat to keep warm instead of building campfires. Then they died, probably horribly.

      1. Best (lowest in gamma and neutron emission with “high” power density) isotope for RTGs is rare and expensive. I don’t believe RTG is considered a “reactor” as they don’t depend on neutron chain reaction and are not controlled.

      2. For the most part, RTGs were used with thermopiles. This means efficiency was pretty abysmal, in the sub-10% range. You use them when there’s truly no other solution. Even in space craft, they’re looking at ways to build a reactor (rather than a RTG) because the RTGs are so low power.
        Nuclear reactors produce a lot more heat from the same mass of fuel.

        Furthermore, the isotopes needed for an RTG have to be made in a reactor, and are extremely expensive. So although they are super reliable and safe, the cost per watt is too high to be useful in areas where there are alternative sources of power.

      3. > after 10~15 years the output starts dropping off.

        That’s a misconception.

        The output starts dropping off immediately.

        10-15 years, or whatever the half-life is, is a measure of how soon power drops by half. Ask Wikipedia for half-life, or even better for direct information on RTGs and on things like the Curiosity rover, those pages have plenty of explanations on all this.

  1. One thing that is missing from the video is the source of cold, to generate power using heat you need a thermal difference, so what are they using for the source of cold ? Is it air ? A large source of cold water, to improve the efficiency of the turbines, is one of the reasons that why most gas/coal/oil/nuclear power plants are generally built near coastal waters.

    1. I presume it can be piped in. Perhaps with this size of reactor you don’t need an ocean-sized source of cold, and you can just use a groundwater well or municipal water supply?

    2. Wonder what the cost is? Roughly, 1 MWh is £100. A 1 MW reactor would produce 87600 MWh in 10 years, thus £8,760,000 worth of power.

      A little sceptical that the 1MW ones would be cost effective in today’s society. But to power a remote lair in a hollowed out volcano, where money is no problem – perhaps.

        1. I like the thinking – nuclear powered sharks with lasers :)

          Probably a bit big for mutated bass, but if they leak, in a few generations the mutations could go wild, so who knows!

      1. Well, compare and contrast to a wind turbine, which cost about a million pounds per Megawatt to build, plus 3-5% for maintenance per year, and they have a typical capacity factor below 0.3 and a lifespan of 25 years. That comes out roughly 65,700 MWh of electricity for £2 million at a wholesale cost of £30/MWh.

        UK ofgem day-ahead wholesale prices vary between £20-60/MWh with an average around maybe £45-50 although currently it’s been ticking up to £60 with the lack of new base load capacity.

        1. For the same worth, a nuclear reactor can run at a capacity factor of nearly 1 if so desired, so for the same 25 years you get about 200,000 MWh and if you want to hit that £30 per MWh you can pay up to £6 million for the generator all told.

          I’m sure they can build one cheaper than that.

          1. You forgot to factor in the decommissioning costs: disassembly, proper storage of irradiated materials and used combustible. While most of a used wind turbine can be recycled and reused, this isn´t much the case with a nuclear reactor. Also the costs for clean-up and de-pollution in case of accident are way beyond the benefits. A failed wind turbine not so much.

          2. That’s for a 114 MW SMR. Can’t imagine it scales well down to the 1 MW capacity. But if it does and continues to do so all the way down, I’d certainly splash out a few $k to power my house and have endless free hot water for 25 years. That’d be awesome. A little too much like the Fallout universe though!

            Wonder how much of the $303M for the 114 MW reactor is set aside for decommissioning? If deep geological deposits are a thing by then, perhaps a little work (remove on switch/drain coolant/leave for a few decades to cool off and then stick the thing in a hole? Shame that can’t be done with Chernobyl.

          3. The $2,901/kw is for a 100+ MW machine. Wonder if it scales as low as the 1MW being discussed. It’d be awesome if it scaled linearly lower too as replacing central heating in everyone’s houses with an inexpensive generator would be awesome!

          4. That’s an interesting question. 100+ MW generators are still big stationary plants that cannot be mass-manufactured in the proper sense, so a truck-sized unit could be even cheaper per unit since they would be pushed out of a production line.

          5. For a point of reference, a 1-2 MW generator set – basically a marine diesel engine, a generator and a fuel tank with all the automation and controls stuffed in a shipping container or trailer – can be bought for less than $500k.

          6. The way the nuclear subs work these days, they’re fueled once and after 30 years they simply float them to a dry dock and cut the reactor section out. The rest of the ship goes to scrap, and the reactor is stripped and buried in the desert.

          7. @rok even including stupid incidents like Chernobyl, the environmental costs of the nuclear industry are far lower than our current power systems – and potentially lower than renewables (don’t forget that solar PV relies on stuff coming from Chinese open cast mines… mmm run-off…), and wind relies on non-recyclable composites.
            Cost-wise, yes, cleanup is high when there’s a problem, though I’m sure if we stopped government funding cleanup, we’d soon find cheaper ways to do it. Nothing spends money faster than a government cleanup.

          8. Build one for cheaper than that? Sure. But that won’t cover the cost of the environmental impact studies. And if by some chance it does, or you’re willing to pay anyway, they’ll make you do a bunch more until you get the picture. Nuclear power _is too expensive_. Understand?

          9. > don’t forget that solar PV relies on stuff coming from Chinese open cast mines… mmm run-off…), and wind relies on non-recyclable composites.

            Those are all just temporary limitations of the technologies that happened to be current when renewable usage exploded. They won’t be issues with the coming generations of renewables that will be implemented in the coming decades, so it’s really pointless to complain about any of this.

        1. This response shows a lack of understanding of basic economics. The solution has to be profitable so that we can use that profit to fund new and even better ideas!

          But your views aren’t unique – they even expand to Governments. Most Socialists countries who fail to understand that everything has to be long-term profitable to succeed have failed and the ones that have not failed yet will fail.

    3. Not sure if it’s actually true, but when I went to the University of Maryland (College Park) it was always said that the buildings were heated by the exchange water from the reactor on campus. Exchange water could be used to heat neighborhood homes in the winter and just heat-pumped into the ground (distributed over a large area).

    4. A lot of designs I’ve seen were build so that the reactor was placed in the basement of a skyscraper and then tied into the building’s HVAC system to dissipate the heat of the reactor. I’ve also seen some solutions that use the heat of the reactor to boil water, vent the steam up to a collection system at the top of the tower, storing it in a water tower for distribution throughout the building, replacing the need for water pumps to water to the upper parts, and the steam would reduce the amount of contaminates in the water itself as well.

    1. A steampunk train running for decades, on nuclear power, never needing to refuel? The Orient Express people will be selling a$$ to get their hands on as many of these as they can.

    2. Well, the TGV’s in France are electric, and France gets a lot of power from nuclear sources, so that’s basically a nuclear powered train, but with extra steps.

      1. Steam isn’t dead. Steam runs every major power plant in this country. Mobil steam is dead only because of the power density of diesel and because modern electric designs gave more control by decoupling the wheels from the power source.

      2. Nearly every nuclear, coal, or oil power plant in the world today uses steam. If you have a more efficient way to convert heat into kinetic energy get your patent and claim your Nobel prize.

        1. While it’s not more efficient energy wise, in terms of Carnot, ORC systems can be more cost effective for smaller power generation facilities. Well designed and managed steam cycle probably makes the most sense for nuclear with it’s near constant heat output, but for geothermal, biomass, or anything with variable heat output ORC is usually the better choice.

  2. With the proliferation of small reactors it will make answering one question more difficult…. “Where are the Noooclear Wesssels ?” (Ensign Chechov – Star Trek)

  3. Just a little nitpick: the moderator and the control rods are not on same task. Moderator does slow down fast neutrons, but that enables the nuclear fuel to capture them, which increases chain reaction rate. The purpose of control rods is not to slow neutrons further down, but to absorb them, soak them up, remove them from the equation, throttling chain reaction rate down.

  4. They didn’t exactly steal them. The Soviets built the RTGs for a fairly high power density, as a consequence they would lose power fairly quickly in a few years, and they kept tossing the spent ones around the woods behind the lighthouse without any attempts to safely dispose of them. The local illiterate peasants and roaming tribesmen would find them and go, “Hmm, strange magic thing that keeps warm.”

  5. Somewhere I have kicking around a “Look how great our science is” booklet that describes soviet radio sets that were powered by bi-metallic coils of wire wrapped around a kerosene lamp. The colder it was outside, the more efficient the power generated. I have always thought what I great idea. And a hell of lot safer.

  6. Don’t seem to be a good idea to me. Imagine those constructed by thousands then after their expected life they would be dumped anywhere or left on place in remotes areas with no monitoring with their radioactives byproducts spreading in the envrionment. Bad! bad!

  7. The first paragraph says “Nuclear fuel produces heat from fission while a moderator like water prevents it from melting down both by cooling the reactor and slowing down neutrons.” Slowing down neutrons does not prevent a melt down. The purpose of slowing down the neutrons is allow them to be absorbed by the fuel and produce fission in thermal reactors.

  8. Wondering why there is still the issue with storage.

    I wonder if there is a conspiracy to keep the nuclear plant installations for other more nefarious reasons and why like recently a former “chemist” from Los Alamos commented regarding the concealed wireless assaults and came out acting like she understands microwaves, microwave heating and microwave weapons systems.

    Not that microwaves are the only regions of the electromagnetic spectrum (EMS) capable. Probably photonic and phononic weapons would be a better term if not EMS weapons.

    Anyway, something doesn’t add up and I wonder if the U.S. has either brain damaged or compounding and concealing or compromised D.O.E. leadership, scientists and engineers as well as other staff.

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