This is a passionate team working on a very hard problem. They have guts and skills. I've always loved microreactors for fringe remote power where people are willing to pay 20x more than normal diesel generator prices. Like Antarctica, remote bases, the moon etc.
Trying to make microreactors cheap is super hard. We've obviously tried it many times, the most relevant being the truck-mounted military microreactor ML-1 (the only closed-cycle direct gas turbine reactor ever operated) https://en.wikipedia.org/wiki/ML-1.
Shielding is hard. Even a small reactor this size needs like 8 ft. of high density concrete on all sides, or equivalent, plus 4-6" of a heavy metal like tungsten to take down the gammas. You can't just put it underground because the neutrons activate the dirt. Driving it off afterwards is borderline impossible because you generally have to put the spent fuel in robust canisters that can handle collisions, rollovers, and RPG attacks.
But the hardest part is fuel cost. This reactor uses medium-enriched ('HALEU') fuel, which is super expensive, and then it packages it into TRISO form, which is about 100x more expensive to fabricate than regular UO₂ fuel. On the plus side, it's super robust and can minimize the need for other safety systems. Those prices could both go down, conceivably, but the fab process is pretty intricate, and it's hard to bring down enrichment costs. In my analysis, the fuel cost alone nearly makes this kind of reactor uncompetitive with a diesel generator in almost all applications. So even if the reactor is free (because you build it on an assembly line?), you're still out of luck.
Then there's thermal strain. When you're a small reactor you have big gradients. This bends things. Neutrons make it worse. Then you have a tiny box with electronics in it getting absolutely hammered by neutron dose. That does bad things too.
I hope they can find a way to bring fuel costs way down. I really like the people at this company, and I really like nuclear power and want to see it used in many new applications. I just don't quite see the path yet.
Wonder if much of the world didn't turn away from nuclear power they way they did since the 1960s, if we wouldn't have solved alot of problems like these already given research was stagnant (relative to other research in power generation) for a very very long time.
It'd be a much different field if we had kept it up. I spend a lot of time in nuclear archival material, and facilities like CANEL in Middletown CT absolutely blow my mind. They had hundreds of people working on crazy reactor technologies. They were flowing white-hot lithium metal at 100 mph. But yeah we gave all that up. My friend wrote a pretty good article about this not long ago https://www.ans.org/news/2025-05-08/article-6961/hightempera...
If they radiation shield it properly, I'd like to think so. That won't do anything to 8 ft of concrete plus 4" of tungsten.
Plus the fuel form holds in a lot of the fission products even when scattered around. It may overheat and release volatile fission products but I don't think it would be a widespread disaster no matter what.
I don't really get the "make it small enough to fit on a truck" thing. The main impediment for nuclear is cost, and then being able to build reactors on an assembly line would be a significant advantage. But how much of that advantage is retained if the product comes on more than one truck and the thing that comes is the reactor, the fuel and the turbines whereas the concrete gets poured on-site? It seems like that should get you nearly all of the cost savings from mass production but then you get a full-sized reactor that can power a city instead of something that can only replace a diesel generator.
I think you're missing some use cases and some parameters.
For the average home, this doesn't make sense. But for a hospital? A data center? There are plenty of places that are happy to pay a premium for an independent, redundant, and/or emergency power source. Somewhere like a hospital is going to get big advantages from something like this because it not only provides electricity but hot water (reducing the electrical demand that would go to hot water creation).
There are also big advantages to remote places. Getting power in Alaska[0]. It's even difficult to get it in places like Alberta or Montana, both of which will also would take advantage of the heat source.
Even at 5 years, this is more reliable than something like a gas generator and has a lot of logistical advantages. This says it does 1MW or electric power and 1.9MW of thermal. I found a 1MW generator[1], and it looks to consume between 77-87 gal/hr. A gallon weighs 7lbs, so 80 gal is 560lbs and takes 0.3m3. At one day's consumption (1920 gal) you need to be able to store over 13klbs and it'll take up 7.3m3 (not including the volume of the container and that it needs to be stored somewhere that is dry but also well ventilated). On top of that, diesel has a self life of 6mo (can extend to a year), so you're going to be doing a lot of deliveries...
Given that, I can see a lot of places that would gladly make those trade-offs.
Also, if it can fit self-contained in a container, the parts are going to be much smaller. You gotta start somewhere, right? Doesn't seem a bad idea to start with edge customers who are willing to pay a premium.
I have a hard time seeing how communities that have trouble keeping the skills necessary to operate diesel generators will be able to switch to nuclear reactors.
Extracting uranium from seawater gives you natural uranium, which needs to be enriched for use in most power reactors. The reactor under discussion here needs higher uranium enrichment and more expensive fuel fabrication operations than common power reactors. Developing uranium extraction from seawater is a good long-term insurance plan for uranium availability, but it's not going to help this reactor get its fuel costs down.
Pro tip: if you want to check if a nuclear reactor design is vaporware or has real legs, you check their application with the NRC (nuclear regulatory commission). It turns out that the NRC does have a page for Kaleidos [1]. You can even go and see what documents Kaleidos submitted this month. They submitted a request to be exempted from some regulation called "10 CFR 55", which they feel is not applicable to them. I have no clue if that is the case or not, but at least they seem to be in fairly frequent contact with the NRC, and that's good news.
I'm skeptical, not because it can't be achieved, but because it's not that practical.
Diesel generators are "great" because diesel doesn't evaporate. You can have it there for years, and with good design, it just springs up the next day.
This nuclear reactor has to be connected for fleet monitoring if you want to operate it. Which excludes it from many real life scenarios where diesel generators are used.
Maybe for remote locations where constant power is needed (Antarctica and such), but I see their uses being very limited.
> Diesel generators are "great" because diesel doesn't evaporate.
LOL, no. I see, you have never worked with large diesels meant for backup.
If you just leave diesel fuel alone, then over time (6-9 months) the residual water separates at the bottom of the tank. And then various microbial life springs into action, happily living off all of that free energy. While there's some dissolved oxygen, it will happily use it to oxidize the fuel. But even without oxygen, the bugs will try to live off energy produced by polymerization of unsaturated hydrocarbons.
Polymerization == gunk that clogs up your fuel filters.
So you have to periodically clean up diesel fuel by removing water and filtering the gunk out. It's called "fuel polishing". Large diesels will have fixed systems, for smaller diesels, sometimes mobile systems are used like these: https://fueltecsystems.com/equipment/pneumatic-systems-2/
If I Google "diesel shelf life", the most common answer is 12 months. Do you have a better source? Propane probably makes more sense for fuel that needs to sit around for years.
Do you know the shelf life of TRISO fuel? I imagine it doesn't matter because it would be very expensive to build a reactor and not switch it on.
Diesel will degrade with exposure to oxygen, but a diesel engine can burn pretty much any flammable liquid that you can meter out. It really comes down to the engine itself and if it can handle less-than-perfect fuel.
Anecdotally, I came across a large (for a single user) quantity of diesel 9 years ago. (Nothing exotic - a company went titsup and I was the only one both bidding for and capable of removing the diesel from their premises within an acceptable time frame; I got approx 80% off the pump price at the time.)
I still run my tractor and Land Cruiser off the stuff; the tractor had an outing today. Granted, neither of those engines are very particular about the fuel they are given, but still...
(Water drained off every few months, also a biocide is added to keep the diesel gunk at bay.)
I mean if you trying to run that fuel in a performance application where you are pushing the fuel to its absolute limit, it might be bad, but most diesel engines can be run on nearly any burnable oil, you just get less power out and a bit dirtier burn.
They give similar specs ideals about gasoline fuel going bad in 3-6 months, and yet 95% of gasoline engines will still run 2 year old fuel fine because they aren't pushing compression ratios to the absolute possible limit, and half of the performance engines that do push limits these days have adaptable computer controlled compression and sensors which will figure out how much it can push the fuel.
If I put 5 year old diesel fuel into any regular diesel motor or generator or vehicle and it didn't start up, I would be extremely surprised, and be most worried that the fuel either wasn't diesel fuel to start with or had a wide open hole in the container that a bunch of rain water drained down into.
That said, if I had some kind of tuned up diesel motor that I was trying to push 800+ HP out of, I probably wouldn't use year old diesel fuel just in case. High performance motors like that are already straddling the line between working great and catastrophic failure and using old potentially bad fuel only adds to it.
> This nuclear reactor has to be connected for fleet monitoring if you want to operate it. Which excludes it from many real life scenarios where diesel generators are used.
I don't understand this sentence, why does connection to fleet monitoring preclude using this microreactor as opposed to a diesel generator? Can't you just hook a starlink up to it, and program it to shut down in the event of prolonged comms loss?
I don't have any first hand experience with diesel generators, but I saw three cases where power was lost and diesel backup was switched on. In two of these three cases, the generator failed (once didn't start, the other time it ran for 30 mins). In both cases it was in scenarios where I'd imagine reasonable care and maintenance were applied.
Am I right that 1MW of solar generation would only take about a football field worth of panels? Of course that doesn't account for battery or other storage for nighttime, etc. but seems like it would be far cheaper and far less regulatory issues unless you really needed that much power generation in a very small footprint.
Looks like a giant part of the value is that it can be shipped in, dropped on the ground on site, turned on overnight, and it only takes up the footprint of a shipping container.
If you have 24 hrs to find an empty football field within a powercable's distance of what you're trying to power, and then fill it with solar panels and batteries, you're gonna have a bad day.
If you ship in a stack of panels, inverters and cables, sure. But maybe you could be a little smarter about it, like a container with all the electronics (inverters, batteries, management) and a bunch of folded, pre-cabled panels that you can pull out across a field. If you bring a couple of those covering a field in a few hours shouldn't be that hard and could be ready for use instantly provided the batteries are charged at delivery.
And it's closer to 4-6x football fields if you did it in say, San Francisco. 4-5x football fields in Kansas City. 6-8x football fields in Chicago. Again, plus battery storage.
It depends on where you're at, but for a sunny place yes; somewhere like London a panel can harvest ~100 W/m^2 (0.5 MW for a football field with 100% panel coverage) averaged over the whole year, while in Arizona it's more like 230 W/m^2 (1.2 MW for a football field). NREL has some great insolation maps here: https://www.nrel.gov/gis/solar-resource-maps
For a permanent installation I would agree that solar would usually make more sense, but the mini reactor might be better in scenarios where it's replacing a diesel generator - emergencies, temporary events, confined spaces, etc.
It requires space, setup time, and then there's the intermittency issues. You'd need enough batteries to store, what, 12 MWh? 20? More if you're accounting for cloudy days?
People just want a compact solution to generate power, not a whole separate project.
“Only” a football field is a lot of space. A 1MW diesel genset on a trailer is about 30’ long by 8’ wide by 10’ tall, which is 0.4% of a football field.
That used to be true, not so sure my trust in our institutions is high these days. Seems a few million $ donation to the right people can make all regulations just vanish.
No, that used to be believed to be true. We're just seeing the curtain come down.
The food pyramid, the CIA's "war on drugs" in South America, the wars with Iraq, Libya.. Just to name a few. Why do we pretend like bribery and corruption is this new thing?
I'm not filled with optimism about this concept. Let's work backwards from crash safety (say a reactor on a truck getting t-boned by a freight train). The radioactive material needs to be held in an armored containment to avoid release. That would have to be roughly comparable to CASTOR containers in terms of its resilience. But these containers have limited capability of passive thermal energy dissipation (Google finds models that handle 10kW to 45kW thermal power generated in the interior). This would be approximately the ceiling for the direct thermal power output that is still reduced by limited efficiency of heat-to-power conversion.
This is admittedly napkin math, but it should be good enough to set expectations.
You are thinking accidents. I think we need to be thinking deliberate attempts to compromise these things and all the security measures needed to mitigate against that. And most importantly, the cost associated with that. Which comes on top of already significant cost.
The naive notion of we'll just ship these all over the place by the thousands and it's going to be fine is not going to withstand a lot of critical thinking very long.
I was indeed not thinking about deliberate attacks. But that doesn't change the result much as I assume that the CASTOR containers that I used as reference are designed to withstand all of these worst case scenarios.
Here's a related company, Ultra Safe Nuclear, making TRISO fuel units.[1]
They went bankrupt in April 2025.[2] They at least got as far as making fuel units, although I suspect the video shows dummies being made, because they are not taking enough precautions for handling enriched uranium.
"The plan is for the small amount of spent fuel (the volume of the spent fuel in one reactor is equivalent in size to just two Walmart gas grill propane tanks) that comes out of our reactors at the end of their duty cycle to only be temporarily stored on-site until a federal repository or interim storage solution becomes available. "
> equivalent in size to just two Walmart gas grill propane tanks
Is this a real measurement in tank sizes? Why not just say two 20lb tanks? What if I bought my tank from Home Depot? Are they a different size? Do they think using Walmart makes it more relatable?
I mean that is exactly what we do right now with all nuclear waste. Without a nuclear material repository there is only so much you can do. You don't want to just dig a simple hole somewhere and start tossing everyone's high level waste into it, that would just be asking for a massive disaster.
Readit News
Trying to make microreactors cheap is super hard. We've obviously tried it many times, the most relevant being the truck-mounted military microreactor ML-1 (the only closed-cycle direct gas turbine reactor ever operated) https://en.wikipedia.org/wiki/ML-1.
Shielding is hard. Even a small reactor this size needs like 8 ft. of high density concrete on all sides, or equivalent, plus 4-6" of a heavy metal like tungsten to take down the gammas. You can't just put it underground because the neutrons activate the dirt. Driving it off afterwards is borderline impossible because you generally have to put the spent fuel in robust canisters that can handle collisions, rollovers, and RPG attacks.
But the hardest part is fuel cost. This reactor uses medium-enriched ('HALEU') fuel, which is super expensive, and then it packages it into TRISO form, which is about 100x more expensive to fabricate than regular UO₂ fuel. On the plus side, it's super robust and can minimize the need for other safety systems. Those prices could both go down, conceivably, but the fab process is pretty intricate, and it's hard to bring down enrichment costs. In my analysis, the fuel cost alone nearly makes this kind of reactor uncompetitive with a diesel generator in almost all applications. So even if the reactor is free (because you build it on an assembly line?), you're still out of luck.
Then there's thermal strain. When you're a small reactor you have big gradients. This bends things. Neutrons make it worse. Then you have a tiny box with electronics in it getting absolutely hammered by neutron dose. That does bad things too.
I hope they can find a way to bring fuel costs way down. I really like the people at this company, and I really like nuclear power and want to see it used in many new applications. I just don't quite see the path yet.
Can it survive 20 kilos of TNT planted by a terrorist?
Plus the fuel form holds in a lot of the fission products even when scattered around. It may overheat and release volatile fission products but I don't think it would be a widespread disaster no matter what.
For the average home, this doesn't make sense. But for a hospital? A data center? There are plenty of places that are happy to pay a premium for an independent, redundant, and/or emergency power source. Somewhere like a hospital is going to get big advantages from something like this because it not only provides electricity but hot water (reducing the electrical demand that would go to hot water creation).
There are also big advantages to remote places. Getting power in Alaska[0]. It's even difficult to get it in places like Alberta or Montana, both of which will also would take advantage of the heat source.
Even at 5 years, this is more reliable than something like a gas generator and has a lot of logistical advantages. This says it does 1MW or electric power and 1.9MW of thermal. I found a 1MW generator[1], and it looks to consume between 77-87 gal/hr. A gallon weighs 7lbs, so 80 gal is 560lbs and takes 0.3m3. At one day's consumption (1920 gal) you need to be able to store over 13klbs and it'll take up 7.3m3 (not including the volume of the container and that it needs to be stored somewhere that is dry but also well ventilated). On top of that, diesel has a self life of 6mo (can extend to a year), so you're going to be doing a lot of deliveries...
Given that, I can see a lot of places that would gladly make those trade-offs.
Also, if it can fit self-contained in a container, the parts are going to be much smaller. You gotta start somewhere, right? Doesn't seem a bad idea to start with edge customers who are willing to pay a premium.
[0] https://app.electricitymaps.com/zone/US-AK/72h/hourly
[1] https://mart.cummins.com/imagelibrary/data/assetfiles/007036...
https://www.spitsbergen-svalbard.com/2024/04/09/longyearbyen...
I've spoke with some researchers and investors working on seawater uranium extraction and left quite optimistic.
[1] https://www.nrc.gov/reactors/new-reactors/advanced/who-were-...
https://www.ecfr.gov/current/title-10/chapter-I/part-55
Diesel generators are "great" because diesel doesn't evaporate. You can have it there for years, and with good design, it just springs up the next day.
This nuclear reactor has to be connected for fleet monitoring if you want to operate it. Which excludes it from many real life scenarios where diesel generators are used.
Maybe for remote locations where constant power is needed (Antarctica and such), but I see their uses being very limited.
LOL, no. I see, you have never worked with large diesels meant for backup.
If you just leave diesel fuel alone, then over time (6-9 months) the residual water separates at the bottom of the tank. And then various microbial life springs into action, happily living off all of that free energy. While there's some dissolved oxygen, it will happily use it to oxidize the fuel. But even without oxygen, the bugs will try to live off energy produced by polymerization of unsaturated hydrocarbons.
Polymerization == gunk that clogs up your fuel filters.
So you have to periodically clean up diesel fuel by removing water and filtering the gunk out. It's called "fuel polishing". Large diesels will have fixed systems, for smaller diesels, sometimes mobile systems are used like these: https://fueltecsystems.com/equipment/pneumatic-systems-2/
Do you know the shelf life of TRISO fuel? I imagine it doesn't matter because it would be very expensive to build a reactor and not switch it on.
I still run my tractor and Land Cruiser off the stuff; the tractor had an outing today. Granted, neither of those engines are very particular about the fuel they are given, but still...
(Water drained off every few months, also a biocide is added to keep the diesel gunk at bay.)
They give similar specs ideals about gasoline fuel going bad in 3-6 months, and yet 95% of gasoline engines will still run 2 year old fuel fine because they aren't pushing compression ratios to the absolute possible limit, and half of the performance engines that do push limits these days have adaptable computer controlled compression and sensors which will figure out how much it can push the fuel.
If I put 5 year old diesel fuel into any regular diesel motor or generator or vehicle and it didn't start up, I would be extremely surprised, and be most worried that the fuel either wasn't diesel fuel to start with or had a wide open hole in the container that a bunch of rain water drained down into.
That said, if I had some kind of tuned up diesel motor that I was trying to push 800+ HP out of, I probably wouldn't use year old diesel fuel just in case. High performance motors like that are already straddling the line between working great and catastrophic failure and using old potentially bad fuel only adds to it.
I don't understand this sentence, why does connection to fleet monitoring preclude using this microreactor as opposed to a diesel generator? Can't you just hook a starlink up to it, and program it to shut down in the event of prolonged comms loss?
Looks like a giant part of the value is that it can be shipped in, dropped on the ground on site, turned on overnight, and it only takes up the footprint of a shipping container.
If you have 24 hrs to find an empty football field within a powercable's distance of what you're trying to power, and then fill it with solar panels and batteries, you're gonna have a bad day.
Nor is that generating electricity at night.
Plus battery storage.
And it's closer to 4-6x football fields if you did it in say, San Francisco. 4-5x football fields in Kansas City. 6-8x football fields in Chicago. Again, plus battery storage.
For a permanent installation I would agree that solar would usually make more sense, but the mini reactor might be better in scenarios where it's replacing a diesel generator - emergencies, temporary events, confined spaces, etc.
People just want a compact solution to generate power, not a whole separate project.
No, that used to be believed to be true. We're just seeing the curtain come down.
The food pyramid, the CIA's "war on drugs" in South America, the wars with Iraq, Libya.. Just to name a few. Why do we pretend like bribery and corruption is this new thing?
This is admittedly napkin math, but it should be good enough to set expectations.
The naive notion of we'll just ship these all over the place by the thousands and it's going to be fine is not going to withstand a lot of critical thinking very long.
[1] https://www.youtube.com/watch?v=uR7VDqUbaCg
[2] https://nuclear-news.net/2025/04/04/update-on-the-bankruptcy...
yikes from their FAQ:
"The plan is for the small amount of spent fuel (the volume of the spent fuel in one reactor is equivalent in size to just two Walmart gas grill propane tanks) that comes out of our reactors at the end of their duty cycle to only be temporarily stored on-site until a federal repository or interim storage solution becomes available. "
They don't even have plan while the exist now.
So everyone just leaves it in the reactor's parking lot for now, in big concrete and steel dry casks.
Is this a real measurement in tank sizes? Why not just say two 20lb tanks? What if I bought my tank from Home Depot? Are they a different size? Do they think using Walmart makes it more relatable?