Honey, We Shrunk The Nuclear Reactor

[Power Engineering] took a trip to the Westinghouse facility that provides maintenance for nuclear reactors. The research division there has a new microreactor called eVinci and — according to the company — it is a disruptor. Technically, the device is a heat pipe-based passive cooling design that can generate 5 MW of electricity or 13 MW of heat from a 15 MW heater core. You can see a video about the device below.

The company says its initial targets are remote areas like mines that usually depend on diesel generators. Hundreds of passive heat pipes inside a graphite core which contains TRISO (tristructural isotropic) fuel pellets. The heat pipes allow efficient transfer of thermal energy with no pumps.

A heat pipe uses a working fluid — in this case a liquid metal — to provide impressive thermal transfer characteristics. Heat boils the liquid which then moves to the cooler end of the pipe. There it condenses and wicking returns the liquid to the hot side where the process repeats.

The reactor has only one set of moving parts: the reactivity control drums which manage the power level. If power demand goes down, the drums expose an absorber to retard nuclear activity. For higher demand, the drums expose a reflector which increases nuclear activity. The reactor manages this autonomously.

Of course, the term “micro” is in the eye of the beholder. The eVinci would take four trucks to move. One carrying the reactor, another carrying the electrical conversion system. A third truck carries instrumentation and controls while a fourth carries some additional equipment. Fuel lasts eight years and is encapsulated in several different ways to prevent contamination.

Westinghouse claims they plan to have commercial availability by 2027. Of course, there are regulatory and other hurdles to clear before that can really happen.

Building your own nuclear battery is possible, but don’t expect megawatts of output. We’ve been tracking the trend toward microreactors since last year.


99 thoughts on “Honey, We Shrunk The Nuclear Reactor

  1. About time! The shape reminds me of some designs I’ve read about for deep space propulsion applications. Also compact reactors, similar fuel cladding and reaction control scheme. But you pipe liquid hydrogen through it fast as you can and out the back so you get thrust and also so your rocket does not become liquid.

  2. On top of all the obvious risks involved with having large amounts of nuclear fuel in cost-optimised reactors without containments, installed in remote and insecure locations:

    The problem with these reactors is that all the parameters keep changing, timelines keep shifting, demonstrators never go into operation and if something is built there are cost overruns that ruin the whole concept. Back in 2019, eVinci was supposed to be a 25 MWe (around 75 MWt) design with a demonstrator going into operation in 2022. Now it’s a 5 MWe design with a demonstrator going into operation in 2027.

    The general target for these reactors is 2 $ per Megawatt (not MWh) of installed electrical power to be able to compete with Natural Gas (larger sites that require multi-Megawatt supplies often don’t use diesel generators), but that just doesn’t seem possible. And since conversion to electrical energy has such a low efficiency, these designs are always optimised to provide process heat. How many sites need 5 MW of electrical energy plus ~8 MW of process heat, 24/7?

    If it wasn’t for government grants, all research into nuclear reactors would stop. Westinghouse had already left the Micro-Nuclear field and only came back because of a 12.9 million USD grant by the DoE.

          1. The high level waste is Plutonium 239 and 240, from U238 neutron capture and double decay. These fuels can be used in the MSR to generate energy.

          2. From what I understand, the waste is a bit of a non-issue if you’re looking at reactors for purely power needs.

            I don’t know the details, but it was explained to me that the reactors that are primarily in use today were created with subsidies, because reactors are expensive to get started.

            The subsidies required research/development/implementation of a specific type of reactor where the byproduct was material that could be further refined into weapons grade.

            The other type of reactor path available has waste that has a MUCH shorter half life of something to the tune of 500-1000 years rather than the astronomical half-life of the variety that came to be in use.

            But again, no weapons-grade fodder so it wasn’t funded.

            (Anyone knows more, please correct inaccuracies.)

        1. The same goes for coal. Somebody is going to have to deal with all the stored coal ash someday – and it’ll be the public that pays.

          Coal ash is radioactive, too. It is as radioactive as waste from a nuclear power plant, but nobody cares because coal ash didn’t come out of a nuclear reactor.


          Coal ash is radioactive. It gets into the ground water around the plants, and in the air. Coal causes acid rain, and dumps loads of CO2 in the atmosphere.

          But, hey, so what? It isn’t a nuclear power plant, so nobody cares.

          1. “Coal ash is radioactive, too. It is as radioactive as waste from a nuclear power plant”

            That is not true and has since been corrected by the author of the linked article.

            The number actually refers to the radiation emissions to the environment around the plants, which is 100 times higher near coal plants than near nuclear power plants, but still on a low level of max. 5% of yearly background radiation doses.

          2. @Pete Just click the link in the parents comment and scroll to the very end. There it literally says:

            “*Editor’s Note (12/30/08): In response to some concerns raised by readers, a change has been made to this story. The sentence marked with an asterisk was changed from “In fact, fly ash—a by-product from burning coal for power—and other coal waste contains up to 100 times more radiation than nuclear waste” to “In fact, the fly ash emitted by a power plant—a by-product from burning coal for electricity—carries into the surrounding environment 100 times more radiation than a nuclear power plant producing the same amount of energy.” Our source for this statistic is Dana Christensen, an associate lab director for energy and engineering at Oak Ridge National Laboratory as well as 1978 paper in Science authored by J. P. McBride and colleagues, also of ORNL.

            As a general clarification, ounce for ounce, coal ash released from a power plant delivers more radiation than nuclear waste shielded via water or dry cask storage.”

          3. Did you actually read the article? The conclusion was that the radioactivity of coal ash results in minimal health effects. You are 3 to 4 times as likely to be hit by lightning than experience adverse health effects from coal ash.

          4. Your comment is generalized to say that coal ash is as radioactive aS nuclear waste! The impression you give is that the two are equivalent, which is not true! Is coal ash radioactive? Yes it is at very low levels that could possibly but not likely be comparable to treated radwaste, which is also very low and within all government discharge regulations and within the discharge permits for a given generating station. Complex technical discussions need to be held in a suitable forum where peers can question and resolve discrepancies with facts that expand knowledge rather than propoghandize!

        2. There are solutions for the waste. The waste can be “burned” in other reactor types. All the nuclear waste in the world probably would fit a Walmart parking lot with room to spare anyways.

          Nuclear (fission) is the best energy solution. Not though in made-to-explode Fukishima and Chernobyl types, but safe reactor tech exists.

          1. Nuclear reactors don’t use highly enriched (aka “weapons grade”) uranium. The nuclear fuel is enriched to a fraction of the percentage necessary for weapons production. Trying to further enrich reactor grade uranium (or spent reactor fuel) to obtain viable weapons grade nuclear material is a massive undertaking that usually requires the resources of nation state.

        3. Nuclear power is stupid — it involves massive amounts of waste water. Does anyone believe the Earth has too much potable water?!?
          More proof that scientists /engineers are both smart AND stupid.

          1. Having operated nuclear power plants for years… where did you pull this non fact from, because it is mot true. We do not release waste water, the core need 20 to 30 gallons a day to replenish water used in sampling. The steam plant may need thousands of gallons a day, but that water is pure in and the steam that is lost is also pure.

          2. In a properly functioning reactor the waste water is not radioactive. Yes, it is warm, but up here in the north end of the world, fishes seem to quite enjoy the warmth.

      1. Much of the cost of nuclear is based on safety. And much of that safety has come from military use of nuclear power. The rest has come through experience working with it. If safety is left to corporate control, disaster waits around the corner. Corruption and greed do not take a backseat to safety. I do not want safety being based off profit.

          1. The price that french consumers pay for their electricity has little relation to the cost. The building of the nuclear powerr plants has been heavily dubsidised and the operator EDF needed to be saved by the state on several occasions.

      2. If it wasn’t for thieves we would never lose our keys because we wouldn’t need them.

        Every regulation over an industry with far greater access and control over our legislative process is the result of the past actions of that industry than the people in it protects.

        How much damage, how many lives destroyed to have enough public presence to get these overburdensome regulations enacted despite the efforts of a much more connected and powerful industry that seems able to write the very laws that govern them?

    1. >The general target for these reactors is 2 $ per Megawatt (not MWh)

      Surely that’s a typo or a complete misunderstanding of the cost of generation. A more realistic cost would be in the neighborhood of $2 million per MW.

      You pay about $1.5 million per MW nominal power for renewable generators like wind turbines, except they return you about 1/4 MW actual power on average.

      1. It pains me to see this formally wonderful publication release repeatedly misleading stories while quoting studies from the 1970s to prove their point. They don’t mention the strict ash controls of coal plant smokestacks since then. In fact if you follow their logic to the end it appears to support nuclear energy as a cleaner process. Totally bananas. Goodbye Scientific American, you used to be a great source of apolitical pure science.

  3. this wins the the Cher~noble™ prize
    nukes are the most dangerous and destructive technology ever made
    there is zero plans for dealing with the fantastic amount radioactive waste
    but hey now its got an ecomitee name and boiler tubes

    1. One of the hard demands on new nuclear reactors, is that they cannot produce the elements needed to make a nuclear bomb. This is why very usable spent fuel isn’t re-used on a large scale – the reactors that can re-use spent fuel, also produce the elements needed for bombs, and that’s essentially prohibited. In other words, nuclear power plants literally cannot lead to more nuclear bombs. Not all nuclear reactions create the plutonium needed for bombs. Just like not all reactions with glycerin (vape juice) create nitroglycerin (bomb stuff).
      There is no fantastic amount of radioactive waste. It is a couple orders of magnitude less in volume than the amount of radioactive waste from coal fired power plants. And, if you want, you can chemically reprocess it and use it again.
      A lot of used fuel has been stored above ground, but look at how little it is, versus the number of decades and terawatt-hours the reactors have been in operation.

      1. That said, there is only one real reason to not want small nuclear plants distributed over the country – and that’s the amount of security needed. A 15MW plant needs as much security as a 1,5GW plant. Somehow you have to guarantee that each and every small plant is just as secure as the large ones, and that’s a big job. I have more trust in larger, more centralized plants.

      2. What deserves mentioning is the radiation level in wood pellets made in europe, especially the NE and E parts. Thanks to chernobyl, the ashes from burnt wood pellets are radioactive. Not so much an issue for a homeowner, but a powerplant running on pellets runs into issues with the ashes.

    2. > there is zero plans for dealing with the fantastic amount radioactive waste
      Watch a 2010 documentary film called “Into Eternity” about the Onkalo waste repository at the Olkiluoto Nuclear Power Plant on the island of Olkiluoto, Finland. It should have enough storage space for one hundred years of waste. The “hot” waste after it has been allowed to “cool” for 30 years stored under water will be stored using the Swedish KBS-3 ( https://en.wikipedia.org/wiki/KBS-3 ). The facility should start to store waste starting in 2023.

      Or read “Deep Time Reckoning” (How Future Thinking Can Help Earth Now) by Vincent Ialenti which uses Onkalo waste repository as a case study.

      I’m not even pro-nuclear, but you have to admire when something is done right. And if you can’t admire that then you can at least admire the engineering and actual long-term thinking.

      1. It is true that the Finns have dealt with this responsibly and timeously. The trouble is that NOBODY ELSE HAS. It can be done, but in practise nowhere in any country wants to be the nuclear waste repository, so plans never get off the ground and the stuff just gets stored “temporarily”.

          1. I have to admit than when I first looked at a sealed iron core inside a sealed copper case I saw the potential for it eventually, if it fills up with salt water, acting like a like a giant battery and oxidising both metals away. A bit like a lemon or potato battery. But then I remember that the bentonite clay is a groundwater sealant. And think that was smart.

          2. Such concerns come down mostly to academic concerns from the political opposition.

            The copper vessels can last for 10,000 years plus minus something? Yes, but the amount of radioactive materials that can escape a potential spill and reach the ground above over 100,000 years is negligible at best. However, the opposition is holding tight to some arbitrary definition of what is “negligible” to a point that is completely meaningless in terms of public health and safety anyways.

            Point being, even if nuclear waste is buried underground, it is never good enough to the opposition. They are applying double standards that require levels of safety and risk not required of any other technology or industry.

        1. You can blame the government for that. I just spent a few weeks loading old fuel cells into a couple dry casks. Wouldn’t need them if the US Govt didn’t flub the Yucca Mtn project.

          Don’t forget, big Nuclear PAID for a waste repository, and the government failed. Now the Govt has to foot the bill for radioactive waste.

      2. The big elephant in the room everyone seems to ignore though, is that pretty much all active nuclear power plants have sufficient space built into them to handle centuries of their own waste. The reason we don’t see much effort going into nuclear waste management technology is that it is a problem that is over 100 years out. And thus far every reactor commissioned has been decommissioned before running out of space for nuclear waste storage, so it’s just as far out as it was 50 years ago. Until and unless we start taking nuclear power seriously as a long term solution to our energy needs, nuclear waste disposal never will be a real problem. And countries that are taking long term nuclear energy seriously are already starting to work on solutions, despite the fact that they have at least a century to do it in.

        1. Good point! I laughed a little when you said the problem is over 100 years out. As long as a solution is identified, approved, and implemented in 50 years from now, no problem. Does anyone remember the Y2K computer programming problem? We all know that it all turned out just fine but does anyone remember the fear people had that it was the end of the world.

    3. if we keep burning n.g and coal earth will be like mars, I don’t understand why man wants to go to mars. in the sun on mars it 300 deg f, in the shade -300 its a dead planet. We have to stop burning carbon fuel , They are trying to build something to save the planet , What have you built or designed ?

      1. I think you are getting the moon and mars mixed up. Wiki, “Temperatures on Mars average about -81 degrees F. However, temperatures range from around -220 degrees F. in the wintertime at the poles, to +70 degrees F. over the lower latitudes in the summer.”

    4. Underground storage is fine. Dropping them into ocean subduction zones is also potentially even better. If you use fast reactors the radioactive waste is a) an order of magnitude less, b) more radioactive, but c)only dangerous for less than a thousand years compared to the tens of thousands of standard reactor waste.

    5. Attempting to be a commedian along with the factless 1970’s propaganda argumentation just doesn’t go hand in hand.

      Not only can the small volumes of spent fuel be reused or re-processed, but even stored ithey output at most 1/10th of sources found naturally in stuff like sand.

      If you want to talk about destructive technologies, burning fossil fuel should be a huge order of magnitude higher on your list.

      But then again, the humanist hippies of the 1970’s knew better – especially about 2020’s technology!

  4. I never understood why we simply not throw this waste into the sun. Space Launch System size rockets have a payload over 40t. The entire waste produced by nuclear reactors over history is under 400 tons.

    1. Lots of odds:
      CO2 and other polluting substances due to rocket production and launch, eating up more than what might have been saved. Risk of loss during launch (kaboom). Risk of loss of control. Only hits the sun if targeted _really_ precisely, otherwise will result in elliptical orbit (the stuff comes back). The given 400 tons are just the waste substances themselves (and represent just the USA sum, but we have a global problem), excluding containenment. Containment is essential here (consider kaboom). Costs are immense which obviously isn’t a problem for the US due to virtually unlimited external debt increase, but it is for most other countries.

      I only see one solution attempt: Ship to china and let them do the sun targeting (they’re quite good now, even with the occasional kaboom hitting nearby villages). But well, you know, they might just dig a hole and pretend.

      If even that fails the whole nuclear waste subject remains a terrible debt for hundrets of generations. If the very first homo sapiens cultures would have placed something like that and we dug it out today, it would not have lost much of its toxicity. We could only hope to understand their ancient warning signs (120 years ago we didn’t even have sufficient knowledge about and methods to detect radiation).

    2. imagine this – *any* fuckup during launch will result in that 40t payload falling back down @ terminal velocity…sounds fun, right?
      also you need about 3500m/s of deltaV from LEO to Sol *with* fairly complex maneuvering

    3. And if we simply process it back into usable fuel again, we wouldn’t even have that much. We had to process it up to fuel grade to begin with; processing it back up to fuel grade again wouldn’t magically make it weapons grade, but since the process is similar everyone has their panties in a bunch.

      Fully depleted fuel stuff that we used to death is no more radioactive than the ore it came from, and could be stuck right back where we found it once it’s done for.

    4. SLS can put that payload into LOW Earth orbit. Launching something into the Sun takes a lot more delta-V. You can’t just “drop stuff into the Sun”.

      The Parker Solar Probe launched on a Delta Heavy IV, with more than a third of the payload capacity of the SLS. That probe massed about 3/4 tonne, and getting it into a close solar ORBIT took SEVEN Venus flybys.

    5. Because of delta V.
      The earth orbit length is : 1 UA x 2 x pi = ~1 billion of km.
      You divide this by the number of seconds in one year (365.25 x 24 x 3600) and you find out that the earth travels around the sun at ~30 km/s.
      You have to cancel this speed to dive into the sun.
      As a comparison : going to LEO is about 8 km/s of delta V.

      1. Yes. Deorbiting into Earth is easy because of the close atmosphere, whereas the Sun from Earth has 8 light-minutes of hard vacuum you need to traverse before any atmospheric breaking help.

        Orbital mechanics are strange. Excluding planetary sling shots, the minimum-energy solution for reaching the Sun from Earth, has you rocketing away to the edge of the solar system.

    6. I just want to say that some of us who post with this name are not so naive and ignorant to propose such a thing. Don’t assume it’s the same voice.
      (This is my name. There are many like it, but this one is mine…)

  5. “A heat pipe uses a working fluid — in this case a liquid metal…”
    Ohhh… what can possibly go wrong? I don’t think there has ever been a liquid-metal-cooled reactor where things didn’t end badly.

  6. Why in the heck haven’t these so called “top scientists” ever heard of, or implemented the pche heat exchanger design into their projects? It takes up less than a tenth the size of a regular heat exchanger, can take massively more pressure and throughput and is way more efficient. I used to work with them over 25 years ago, and yet these guys are still using tubes? Hard to believe.

    1. ‘Top scientists’ spend all of their days thinking about their subjects, so if they’ve not done something then there’s going to be a very good reason why not.
      From two minutes of googling into what a ‘pche heat exchanger’ is (Printed Circuit Heat Exchangers), the two main disadvantages seem to be they’re really expensive, and get clogged very easily, but are difficult to clean.
      But hey, I’m sure if you know better than all these scientists then you can probably make a fortune.

    2. Because those “so called top scientists” are actually aware that PCHE stands for Phase Change Heat Exchanger, and the heatpipes used in this application are heat exchangers that utilise the phase change of the working fluid.

  7. There is no reason why we do not build verticle windmills with the generator at the bottom, these modern windmills do not even need to pivot. Making them cost effective.
    And trains can use both wind turbines and solar panels on top of all those boxcars they are pulling to power the engines electric motors. Both do not produce nuclear waste.
    The Dutchman

    1. For how many decades did we aim to save the planet with wind and solar? And how many percent of global consumption do those technologies cover today? Unfortunately less than the de a d has increased in the same period, despite the fact that only wind is nearly as safe as nuclear per energy unit put out, and this is even including Tjernobyl and technologies as outdated as the call centrals for connecting two people wishing to communicate, and this is without accounting for the future fiber glass disaster we are facing, not only in massive
      volume storage of soggy wings, but much worse all the fiber glass constantly peeling off and getting blown straight into land and oceans. Solar? Way worse than even old nuclear even in terms of direct mortality per output unit and without accounting for the environmental damage from the production, and both technologies without accounting for the massive factor of magnitude higher materials and energy use for the production of the units compared to nuclear.
      Your pipe dream simply fails completely to account for how endlessly more efficient nuclear is, and 4th to 5th generation reactors even much more so, including the benefits of zero long lived elements, inherent safety and no destruction of all our natural landscapes unlike wind especially.
      *Running trains by on-board wind and solar is absolutely hilarious by the way. Best of luck with that, lol!

    2. I don’t think you understand how much energy is required to move a train or how little energy is actually harvested from solar panels. A typical diesel electric locomotive generates around 2,200kW to supply the electric traction motors. That’s over 2 million watts of electricity required. An average 100 watt solar panel is around 9 sq ft in size. To generate 2,200kW using roof top solar panels you’d need around 500 boxcars powering the engine (more than one locomotive can move). Also, the sun doesn’t always shine – so no tunnels or train shipments over night?
      Also, regarding wind turbines – yes wind turbine mounted to a moving train would in fact spin and generate electricity. But the turbine is only rotating because the train is in motion. Putting the train in motion will require substantially more energy than what is supplied by the wind turbines. If you could simply put a wind turbine on wheels and use it’s energy output to drive itself into the wind to generate it’s power than you’d have limitless free energy.

  8. SL-1/ Argonne Low Power Reactor Nuclear Accident, was a small reactor, that killed 3 people.

    One person was missing for days before they found him pinned to the ceiling. Here’s another rod: https://radiationworks.com/photos/sl1reactor2.htm

    They used a C-clamp on a round control rod: https://www.osti.gov/sciencecinema/biblio/1122857

    The entire building had to be dismantled: https://www.youtube.com/watch?v=Q0zT9ARfsT4

    I believe that the area is still radioactive. “The primary remedy for SL-1 was to be containment by capping with an engineered barrier constructed primarily of native materials.”

    Where in your neighborhood do you want the reactor?

    As far as small reactors being green, here an Indian video which shows tailings ponds from yellow-cake production, which is used to make the green-sand, which makes the nuclear metal for reactors.

    1. 1st off, thx for the vid. 2nd, the only not-so great thing about the tailings pond is the earthen dam (they have this bad habit of quickly failing when the draininge fails), otherwise surprisingly good.

    2. And how much harm has been done to humanity by fire, which we’ve used as our primary energy source for millennia and still do even now?

      Love how people cite accidents that happened long ago, when we had no clue how to do nuclear power safely, but they seem to forget that nuclear power still has a much better safety track record than even fire.

        1. You can walk about Fukushima TODAY. No nuclear boogeymen will get you, prompt dose has been at background for years already. Don’t go licking every unwashed surface and you’ll be fine (the same applies to fires too, insulation combustion products are nasty).

      1. Also fail to note that SL-1 was a research reactor which was built on a test range. The SL-1 was not really a failure of hardware as much as the incompetence of personnel (there is also rumor of a murderous love triangle underlying the story). The nuclear industry could be much safer but not if we keep using 50s-70s technology. Anyone who is really upset about the nuclear waste issue needs to go see a decommisioned reactor with fuel casks stored on site. It is amazing how little space is taken up. I am not sure about the desirability of burying encased waste, it seems much safer to me to have them stored in casks on pads above ground where they are easy to monitor and maintain. The reprocessing of this waste could reduce it tremendously.

  9. Might be handy for the robot that’ll populate Mars one day.
    Since humans going to Mars will need robots, and the same humans don’t stand a chance to survive, we’d end up with a population of robots, and if AI is successful then they would be intelligent and lay claim to the planet. Meanwhile they would still require power, and Mars is damn dusty and solar panels get covered in a very short time. So there you have it.

  10. I have ‘working’ design of reactor, size of refrigerator with 6-7 MW … availability by 2049 or so … Of course, there are regulatory and other hurdles to clear before that can really happen.

  11. All these little reactors run on significantly enriched fuel. Fine for space or the military, but the rest of these guys are just squandering VC money and denying the economics of scale inherent in all energy generation.

  12. The solution is using thorium instead of uranium (much more common, less radioactive byproducts, can’t be used for weapons) and breeder reactor designs that can reprocess spend fuel, eliminating the nuclear waste issue. Safe, clean, sustainable nuclear power capable of supplying base load for the entire grid night and day.

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