6/30/2026 at 9:15:21 AM
by clarionbell
6/30/2026 at 9:45:31 PM
Antares were the first ones: https://www.energy.gov/articles/department-energy-celebrates...And closely followed by Valar Atomics two weeks later: https://www.energy.gov/articles/department-energy-celebrates...
by e9
7/1/2026 at 8:38:32 AM
Actually this guy achieved criticality before either of them: https://i.imgflip.com/a0w01q.pngby pseudohadamard
6/30/2026 at 9:35:05 AM
TRISO fuel so.. pebble bed? Is there a reluctance to market on this? The Chinese were all-in.Great to see engineering deliver on time. I wonder if Rolls Royce will also have a smooth ride. It's a PWR.
by ggm
6/30/2026 at 10:20:39 AM
Prismatic (or cylindrical) TRISO also makes sense. There are lots of potential problems using pebble beds (circulation, grinding), whereas doing regular refuelling cycles avoids them, in exchange for down-time to refuel.by chickenbig
6/30/2026 at 12:03:43 PM
TRISO increases fuel cycle costs. It's harder to make, harder to dispose of, and (IIRC) uses higher enrichment.by pfdietz
6/30/2026 at 11:44:00 PM
The positive schpiels say it gets higher utilisaton ("burn") of the fuel inside the micropellets, so it may be HEU, but there's more taken out so less made overall.I'm unsure where the H in HEU comes from, probably nasty sources, and probably nasty radiochemistry.
by ggm
6/30/2026 at 8:42:11 PM
The Rolls Royce modular reactor update page [1] leaves me scratching my head as to where they are, it seems they've passed some really hard UK regulation though, maybe the official source is not the best:by boznz
6/30/2026 at 2:04:16 PM
From the article: > We said criticality in 2026, electricity production in 2027, and power to the warfighter in 2028.Are there any other examples of land-based militaries using nuclear power? Seems kind of like since they can't talk about the energy transition or w/e this has to be a military thing instead.
by tech_ken
6/30/2026 at 8:31:41 PM
That's originally what the SL-1 reactor was meant for. It was also developed at Idaho Falls.Instead of parking diesel generators up at Arctic radar stations (and other remote locations), we'd use a nuclear reactor, which is a logical choice.
The problems were:
1) one control rod could send the entire reactor prompt critical
2) rods could get stuck, requiring that they be "exercised" very carefully as to prevent them from making #1 happen
3) this maintenance was being done by a man in his early 20s who had been sleep deprived and received a phone call before his shift from his wife asking for a divorce
The result was the only immediately-fatal reactor accident in American history.
Glad to see that we're getting over this and moving forward with the concept. Only took us 60+ years...
by lenerdenator
6/30/2026 at 3:05:58 PM
"Stalin is proud to support the rebirth of Soviet Russia’s nuclear industry and ensuring soviets have access to affordable, reliable and secure energy for generations to come". Always mention the fearless leader.by actionfromafar
6/30/2026 at 10:19:57 AM
Congrats to everyone involved. This is a pretty awesome milestoneby seanhunter
6/30/2026 at 10:52:10 AM
To add a bit of context there were 11 companies participating in program and only 2 achieved critiality, and the deadline included in "DOE Reactor Pilot Program" was "July 4, 2026", and Aalo Atomics is the only one that might also make it in time.by mDyJzDPmBdG
6/30/2026 at 1:59:52 PM
Sigh, everything is being done for political purposes, now Dear Leader Donny can proclaim on the quartermillenial celebrations that "we achieved a nuclear milestone!". And maybe add that this is possible because of his nuclear physics genius abilities.I wouldn't even be surprised if the achievements are like "Full-Self Driving", announced hastily with boasts and then slowly revealed to be full of Elon.
by netsharc
6/30/2026 at 2:51:47 PM
Honestly these political rants contribute very little, no offence.by Gud
6/30/2026 at 3:33:24 PM
> Honestly these political rants contribute very little, no offence.What do the other comments contribute? Do they solve inflation, wars, monopolization? Small-picture comments have small audience, like, how many people have access to nuclear materials and gear to make use of the information provided here? In other words "political rants" have their place and in many cases they are more valuable than the rest.
by bigbadfeline
6/30/2026 at 11:19:32 AM
I am still quite confused on the scientific consensus:Should we double down on renewable energy and solve its issues with lots of batteries or should we invest in next generation nuclear energy?
Both at the same time?
Does anyone know?
by Traubenfuchs
6/30/2026 at 11:20:18 AM
Both at the same time. I don't see how putting all our eggs in a single basket benefits us.by datakan
6/30/2026 at 11:29:59 AM
China does: all of the above, where it makes sense.Renewables and batteries to keep your AC, workplace EV charger, stove, pool heater and (since recently) green ammonia producer going, nuclear to prevent e.g. aluminium smelters from seizing up.
Also the cheapest way to make renewables work 24/7 is to build HVDC lines - they cost as much as a highway per unit length and even undersea cables would deploy for less and faster than equivalent nuclear.
The total length of HVDC lines just in China is currently more than 40k km, so they've literally deployed enough of them to wrap around the globe.
by Tade0
6/30/2026 at 12:56:34 PM
China is also still building coal and has passed Europe and will (if they don’t change course) soon pass the US and Canada and the other big ones on a per capita emitter basis. They already passed everyone as top emitter in an absolute sense.https://ourworldindata.org/grapher/co-emissions-per-capita
Not saying they’re not also building renewables and nuclear, but it seems like the policy is more “build anything and everything to satisfy demand” than a focused effort.
BTW: if you look at US emissions, the data center bubble hasn’t had much if any effect. They are still trending down. There’s reasons to dislike that industry but I’m sick of the mindless echo chamber doom on that issue. They’re not that significant in the grand scheme of things.
by api
6/30/2026 at 1:23:02 PM
Coal is already shrinking in the China (in absolute terms, not just as share of production) [1], and share of wind + solar is already larger than in the US [2], so I doubt China will ever reach US proportions in CO2 emissions per capita.An additional data point to support that is that emissions intensity per GDP is clearly falling fast for China [3].
[1] https://ember-energy.org/data/electricity-data-explorer/?ent...
[2] https://ember-energy.org/data/electricity-data-explorer/?ent...
[3] Chart 75 from here: https://robbieandrew.github.io/GCB2025/
by atwrk
6/30/2026 at 2:06:32 PM
According to this graph and assuming both US emissions fall and Chinese grow exponentially at the rate they were over the decade 2014-2024, the figures will cross around 2037.Personally I doubt that, as US emissions have been going up due to data centers:
https://www.reuters.com/business/energy/us-leads-global-co2-...
And while China, like you said, doesn't seem to have a focused goal, it so happens that renewables are the path of least resistance for just having more energy as fast and cheap as possible.
by Tade0
7/1/2026 at 3:31:55 AM
> They already passed everyone as top emitter in an absolute sense.They also passed everyone as top emitter of produced goods, which almost everyone else has outsourced to there. So what?
Buy less? Buy American? European? More expensive? Reshore?
by LargoLasskhyfv
6/30/2026 at 11:22:06 AM
Government should tax / provide incentives based on negative externalities such as environmental impact and let the free market decidehttps://unece.org/sites/default/files/2022-04/LCA_3_FINAL%20...
I think a low carbon mix will result in the cheapest, most reliable and cleanest energy grid.
by preisschild
6/30/2026 at 11:52:35 AM
If your location already has a well-run nuclear energy sector (Finland, Sweden, South Korea): invest in nuclear energy.If you don't: stick to renewables.
And it also depends on what you mean by "we". As a Dane, I don't think us Danish taxpayers should invest in nuclear energy, but I'm perfectly happy that private Danish investors invest in Seaborg/Saltfoss and Copenhagen Atomics.
by sehansen
6/30/2026 at 11:27:22 AM
When it comes to avoiding the worst impacts of the current catastrophic path we’re on, “nothing will work, but everything might”.Do it all.
by bevekspldnw
6/30/2026 at 12:13:33 PM
Nuclear is not on a trajectory to do more than supply a minor amount of world energy. A (say) 10% nuclear, 90% renewable world is not an easier challenge than a 100% renewable world -- the intermittency/seasonality issues aren't eased by having 10% nuclear running as baseload, and keeping it as backup makes its cost per kWh explode.Nuclear really has to go big (supply most of the world's energy) or go home. But supplying most of the world's energy means burner reactors are inadequate -- there isn't enough cheap uranium. Burner microreactors have even worse neutron economy, so this argument applies even more so to them.
by pfdietz
6/30/2026 at 1:17:14 PM
nuclear takes longer to come online though vs renewables can be very quick, so it makes sense to do both as a short-long term strategyby fssys
6/30/2026 at 1:56:24 PM
It's more of an engineering call than something that can be purely determined from inductive reasoning. I think most engineers working in the space would say "both" are needed, but partisans exist on both sides.by tech_ken
6/30/2026 at 12:45:20 PM
That's a political and economic question, not a scientific one. Science can provide input information, but the decision involves weighing all sorts of facts and considerations outside the scope of science.by rayiner
6/30/2026 at 1:06:24 PM
Exactly. Waiting for a scientific consensus on a question that is very clearly not posed as a scientific question is oddly cultishby mohamedkoubaa
7/2/2026 at 6:26:20 AM
We're gonna need portable energy storage regardless of energy source, it's battery vs fuel. There is no such things as battery vs atomic core.by nsonha
6/30/2026 at 12:09:55 PM
Nuclear partisans like to call renewables ideological, but I think this is another example of "the accusation is a confession".The empirical evidence has nuclear being uncompetitively expensive. The current focus on variant reactor designs appears to be something of a Hail Mary attempt to get around this sad state of affairs.
You sometimes see them making an argument about energy density, which goes back to Vaclav Smil. But Smil used this argument to massively mispredict how solar would be go in the market. We don't hear him much anymore.
Nuclear advocates increasingly resort to conspiracy theoretic reasoning to explain away the failure of their technology to compete. This should be a red flag.
by pfdietz
6/30/2026 at 12:48:06 PM
> The empirical evidence has nuclear being uncompetitively expensive.France nuclearized 75% of its grid in the 1980s while the solar folks were faffing around. It's not a cost issue, it's that anti-nuclear folks have choked out the industry.
We need to take the boot off the neck of nuclear. Wind and solar aren't an avenue to moving up the tech tree of civilization, which will involve using vastly more power.
by rayiner
6/30/2026 at 1:01:39 PM
We don't actually know how much that cost France, sine it was mixed in with their military nuclear effort. French auditors threw up their hands trying to figure out the actual costs.What we do know is their attempt to build more NPPs now has gone spectacularly tits up, with costs completely out of control. This should make one view their earlier efforts with great suspicion. Have they become much worse, or were earlier problems concealed?
by pfdietz
6/30/2026 at 1:58:48 PM
Costs are out of control due to nuclear regulation.by rayiner
6/30/2026 at 3:01:33 PM
This is the conspiracy theory reasoning I was talking about. Nuclear is wonderful, but a global omnipotent green conspiracy has hobbled it.Or, maybe, it really is complicated and needs regulation to keep it sufficiently safe in a world where corners are always cut.
by pfdietz
7/1/2026 at 12:44:41 AM
Right or wrong, I don't think conspiratorial is the right descriptor here. The pro-nuclear claim is that the very loud, very public anti-nuclear movement was influential in setting regulations of the industry. It's not "an evil cabal of shadowy green elites secretly control everything", it's "democracy works; fellow citizens were/are dumb; legislation improvements move slowly".by ToValueFunfetti
6/30/2026 at 1:59:30 PM
> moving up the tech tree of civilizationLife isn't Civ 6, there is no tech tree to climb.
by tech_ken
6/30/2026 at 2:24:08 PM
Incorrect. Compare Bangladesh to the United States.by rayiner
6/30/2026 at 2:36:07 PM
Tech development != tech tree, history is nonlinear and ecological. Linear, unlockable "tech trees" are an ahistorical fantasy necessary to make some video games fun and digestible. Applying them to the real world is like trying to win a war by replicating the Battle of Helm's Deep or something.by tech_ken
6/30/2026 at 2:44:04 PM
I’m not saying it’s literally a tree. My point is that we need vastly more power to upgrade to the next level of civilization.by rayiner
6/30/2026 at 2:52:21 PM
Right but “upgrading to the next level” is exactly the type of cognitive error that I’m against, it’s forward-looking Whig history. There is no “levels” of civilization, there’s only the arrangements we have now and the ones that will occur in the future. Maybe those arrangements will have different pros and cons than we have now, maybe they’ll have more sophisticated engineering practices, but there’s no objective “development score” that is being maximized it’s just more humanity.by tech_ken
6/30/2026 at 5:59:15 PM
It's an abstraction, not an error. Naturally you might or might not agree with any individual's underlying metrics, and them with yours.by fc417fc802
6/30/2026 at 6:14:29 PM
> It's an abstraction, not an error.Extending an abstraction beyond its expressive capabilities is an error IMO.
by tech_ken
6/30/2026 at 4:03:45 PM
How do you know nuclear is even on the "tech tree", rather than being a blind alley? Isn't this argument just assuming what you're trying to show?by pfdietz
6/30/2026 at 1:22:34 PM
>The empirical evidence has nuclear being uncompetitively expensiveI have a solution, take the subsidies spent on "renewables" and put them into nuclear! Easy peasy!
by rs_rs_rs_rs_rs
6/30/2026 at 1:44:27 PM
Too late, governments have already subsidized nuclear more than they've subsidized renewables.by bryanlarsen
7/1/2026 at 1:06:55 PM
Renewables have shown excellent experience effects. These effects are a kind of positive externality: improvements in the technology become available generally to future consumers. It makes sense to subsidize positive externalities, just as it makes sense to penalize negative ones.If nuclear had shown good experience effects it too would have merited its subsidies. Unfortunately it hasn't done that.
by pfdietz
6/30/2026 at 12:18:56 PM
next generation nuclear energy = fusionby krunck
6/30/2026 at 1:19:14 PM
Fusion's main accomplishment will likely be to make fission look cheap in comparison, due to fundamental issues of power density in the nuclear island. Why make a huge complex low power density radioactive thing when you can make a much smaller simpler high power density radioactive thing?by pfdietz
6/30/2026 at 12:52:23 PM
Both.We should be investing in all non carbon emitting sources and we should have been doing it since the 1970s when we figured out pretty conclusively that this would be a problem.
Instead we had right wing fossil fuel shills on one shoulder and unscientific woo woo greens on the other, the net effect being that we kept burning more carbon. We still have them, Trump with “beautiful coal” and greens now opposing even solar power and batteries, but climate change is no longer possible to ignore. Some still manage it but those people are nuts.
If we hadn’t stopped improving nuclear we’d probably have emitted half the CO2 we have. It would have become cheaper and safer and more scalable and then when China industrialized they would have copied that instead of burning so much coal.
France with its nearly zero carbon grid is the existence proof.
It wasn’t until the 2010s that solar and wind became grid scale in a big enough way to matter. That was too slow.
Whether someone is at least open to nuclear power is my litmus test for whether they take climate change seriously.
I do. If we hit 600, 800, 1000 ppm CO2, which is possible if the world keeps developing on the back of fossil fuels, we are entering existential risk territory. Earth has had those CO2 levels before, and higher, but our species was not alive then.
We already passed the FAFO threshold for ppm CO2 and now we will FO. But that’s not X-risk yet. I’m talking about the next threshold, which may start around 600 but really kicks in near 1000. This is where you actually start asphyxiating. You get lowered IQ and impaired judgement to a small degree, but across the globe at a time when we really don’t need it.
by api
6/30/2026 at 4:15:00 PM
Other than "not light-water", what type of reactor is it?by NoGravitas
6/30/2026 at 5:53:02 PM
Graphite-moderated core, passively cooled with sodium filled heat pipes:https://antaresindustries.com/
It also uses a Brayton cycle generator with nitrogen instead of steam.
(See 03, 04, 06 in their schematic outline.)
by philipkglass
6/30/2026 at 12:59:36 PM
Is anyone working in the US on a waste solution that isn’t a big hole with a straight out of cyberpunk sci-fi warning plaque?The French reprocess and recycle fissile material but that’s kind of a gnarly industrial process. Still they do it and it works.
The long term solution is to create a second kind of reactor that has a higher burn fraction which means a more fuel efficient fast reactor. Those would be, ideally, the big base load plants if we did this rationally.
by api
6/30/2026 at 1:26:56 PM
I don't see the issue with dry cask storage medium term, and deep geological storage long term. Spent fuel isn't really that dangerous once it's been cooled down and for a couple decades before putting it in the ground, to the point that there are far more dangerous natural things you can dig up.What concerns me is that 250 years of fossil fuel energy continues to store its waste products in my lungs and the water I drink. That's the issue we need to solve with urgency.
by yabones
6/30/2026 at 1:21:45 PM
Europe has about 60,000 tons of nuclear waste storage[1], so lets say the global nuclear waste quantity is 2-3x or 120,000 to 180,000 tons. That sounds like a lot, however it's less than 2 weeks of coal deliveries to a coal plant (at 1 train of 115 cars each with 116 tons of coal = 13,340 tons delivered per day[2]). To take another approach, the average landfill size is 600 acres[3].The "eh, just bury it" approach is really not a bad one. Its not even that much stuff to bury
[1] https://worldnuclearwastereport.org/
[2] https://www.eia.gov/todayinenergy/detail.php?id=16651
[3] https://www.colorado.edu/ecenter/2021/04/15/hidden-damage-la...
by quirkot
6/30/2026 at 6:14:37 PM
I thought something like 30 tons per Gwatt capacity per year was the ballpark for high level waste without reprocessing? How are you arriving at a 120,000 ton estimate?by fc417fc802
6/30/2026 at 7:18:01 PM
Footnote has the backup. 2-3x is guesstimate, but it doesn't really matter. The answer is there's just not much waste to storeby quirkot
6/30/2026 at 9:28:21 PM
Sure there isn't a prohibitive quantity either way but regardless I think the 120k number might be off by one or two orders of magnitude even before reprocessing reduces the amount by ~95%.by fc417fc802
7/1/2026 at 11:59:55 AM
you'll have to take that up with the folks from worldnuclearwastereport.orgby quirkot
6/30/2026 at 4:17:47 PM
Fast neutron reactors can also "burn" waste from other reactors, the "ashes" are radioactive for only 300 years, there is no need for special storage after that. Untreated waste has to be kept in storage for around 100K years before it reaches safe levels of radioactivity.Other than marketing propaganda, there isn't much real information about Mark-0. I'm assuming it's a sodium cooled, slow and hot pebble bed reactor. Hot pebble beds are well known but one with sodium cooling appears to be a first.
Why slow sodium? You get all the risks associated with sodium with none of the benefits of fast neutrons. There are operational, electricity producing, fast sodium reactors which do make some sense. I can't say the same for Mark-0.
by bigbadfeline
6/30/2026 at 1:16:17 PM
IMO, the long term solution will be to simply launch the waste into space. With low enough launch costs the extra mass needed to armor the waste against accidents becomes tolerable.by pfdietz
7/1/2026 at 10:00:34 PM
A much better, safer, and cheaper idea is dropping suitably packaged waste on the subducting side of the Mid Pacific Subduction Zone. It’d be inert long before seeing daylight again…The only downside is the “waste” is quite valuable. MSRs can also use it, and their waste is only dangerous for ~300 years.
by Recurecur
7/2/2026 at 9:56:33 AM
That's a bad idea. Subduction zones move very slowly, and material would come back up in "mud volcanoes", especially with the added heat input of the waste.by pfdietz
6/30/2026 at 1:34:03 PM
Economically absurd, much more expensive than reprocessing or fast waste burning reactors.by api
6/30/2026 at 2:20:27 PM
I don't think that's the case, if launch costs are low enough. The options you describe there are quite expensive. Reprocessing costs somewhere in the neighborhood of $1000/kg. Even fast reactor have trouble disposing of the seven very long lived fission products. A fully reusable launcher might get costs down to $10/kg to LEO. Even if one had to wrap the waste in 10x its mass in launch armor this could be much cheaper than reprocessing.by pfdietz
6/30/2026 at 2:45:38 PM
Why would launch costs be low? $10/kg is fantasy land. UPS won’t ship a kilogram across the country for $10.And who wants spent nuclear fuel in low earth orbit? This is a far worse location for spent fuel than buried in a bunker. This is a worse location than Times Square.
by dpark
6/30/2026 at 6:18:22 PM
> UPS won’t ship a kilogram across the country for $10.I can purchase produce grown on a different continent for less than that at the grocery store so something isn't right here.
by fc417fc802
6/30/2026 at 7:03:08 PM
It was a metaphor for how absurd the statement was. But if you try to ship a 1kg package across the country it will likely cost way more than $10.Freight cost is certainly way lower.
by dpark
6/30/2026 at 2:56:12 PM
Why wouldn't they be low? In the limit, if launch becomes operationally similar to air travel, costs will be a few times propellant cost. And propellant is very cheap. LOX is almost free (the second cheapest industrial liquid after water) and liquid methane isn't very expensive either.Low earth orbit would just be where it's transferred to something to carry it farther out, for example using solar-electric engines.
For all this, remember it isn't done immediately, it's done in (say) 300 years when the short lived fission products are mostly gone.
by pfdietz
6/30/2026 at 3:37:08 PM
I think the onus is on you to explain why costs would drop by >3 orders of magnitude (>4 accounting for the 10x launch armor). It’s something like $1500/lb on a fully loaded Falcon Heavy and all indications are that SpaceX isn’t making money at that price.Plus even if this were free, “shoot 180k tons of nuclear waste into space” seems like a terrible idea in general. It’s one of those ideas that make sense only until you think about the ramifications. What happens when inevitably one of the 3 thousand Falcon heavy rockets explodes and the armor fails and we spread nuclear waste over 3 states?
by dpark
6/30/2026 at 3:51:21 PM
Falcon Heavy is more expensive per kg than F9, because it throws away more things. SpaceX flies it for certain military missions but you will note they launch their own stuff on F9.A full launch on F9 (with recovered S1) is estimated to cost $15M and can put up to 17,600 kg into LEO, or $850/kg.
> (>4 accounting for the 10x launch armor).
You're double counting there. 3x would be just fine even with 10x launch armor.
> seems like a terrible idea in general
And here's the problem: you started from an emotional reaction and are trying to rationalize that.
by pfdietz
6/30/2026 at 4:30:41 PM
> A full launch on F9 (with recovered S1) is estimated to cost $15MEstimated by who? SpaceX charges 74 million for this. Nothing credible I can find indicates that SpaceX is running an amazing 80% profit margin on Falcon 9 launches.
> And here's the problem: you started from an emotional reaction and are trying to rationalize that.
No, your premise is “just launch the trash into space” and you’re hand waving away the complexity, costs, and danger.
by dpark
6/30/2026 at 6:40:50 PM
SpaceX charges what the market will bear, and because they have no good competitor their profit margins can be very large.Anyway, the number is from fairly old Musk interviews. Costs have likely decreased since then.
https://www.nextbigfuture.com/2026/02/spacex-falcon-9-true-c...
> No, your premise is “just launch the trash into space” and you’re hand waving away the complexity, costs, and danger.
At least I didn't trot out a string of obvious errors like you did.
When people do that, it's a strong tell they're engaging in broken thinking. What you did, I think, is believe something, then try to rationalize it. When your thinking reached a justification you liked you just stopped thinking (because, after all, thinking more could break the pleasing argument you just constructed, and that would feel bad).
by pfdietz
6/30/2026 at 7:37:52 PM
> SpaceX charges what the market will bear, and because they have no good competitor their profit margins can be very large.Is your premise that SpaceX will ship nuclear waste at or below cost? Because the 74 million is a publicly available price. And when SpaceX ships stuff for the government the prices go up, not down.
> Anyway, the number is from fairly old Musk interviews.
Yes, Musk is famously honest and accurate with his claims.
> At least I didn't trot out a string of obvious errors like you did.
What obvious errors are those? You don’t seem to like that I’m using publicly available pricing.
> When people do that, it's a strong tell they're engaging in broken thinking. What you did, I think, is believe something, then try to rationalize it. When your thinking reached a justification you liked you just stopped thinking
Pot, meet kettle. You are basing your entire premise on a speculative future that doesn’t exist. You should have just proposed sending it up the space elevator.
None of this idea makes sense from a financial, physical, or risk stand point. “This stuff is too dangerous to store in a hole, let’s launch it into space in 3000 rockets, and then we’ll push it away from earth with another thousand solar electric rockets, and then we’ll use solar energy to evaporate it all! What could go wrong?”
Honestly if you’re betting on a hypothetical future where all this is effectively free, why not just bet on a future where reprocessing uranium drops in price as well?
by dpark
6/30/2026 at 3:31:00 PM
$10/kg isn’t fantasy land if we have fusion rockets, but then we don’t need fission power anymore. :)by api
6/30/2026 at 3:34:33 PM
Fusion would be useless for launch to orbit. Even fission sucks for that. It's really hard to beat the cost and power density of chemical rockets.by pfdietz
7/1/2026 at 11:25:16 AM
Depends. If we get explosive inertial confinement fusion to work you could build a pure fusion version of a nuclear pulse rocket. Look up Project Orion.Orion (in its fission bomb form) is impractical and would be insane to launch from Earth, but it holds the title of being the only “torch ship” drive we know how to build. We could technically build it.
by api
6/30/2026 at 8:45:25 PM
The problem with launching anything into orbit using current rocket motor technologies is that heavier stuff costs more to put into orbit.The elements that are used in nuclear reactors (particularly Uranium and Plutonium) are pretty dense, and thus heavy.
by lenerdenator
7/1/2026 at 12:46:49 PM
That's true, but the cost of reprocessing is also very high, per kg. And aren't the nuclear bros always telling us how little nuclear waste is actually produced? There's about 30 tons of spent fuel per GW(e)-year from today's burner reactors. At $10/kg to space that would be just $300,000 (yes, ignoring lots of costs there, at $10/kg is aggressive, but this is for comparison), a pittance compared to the value of energy produced from the power plant: at $0.05/kWh it produces > $300 M in electrical energy, three orders of magnitude higher.by pfdietz
6/30/2026 at 1:39:20 PM
Probably not worthwhile. If you just leave it in orbit you're going to have to track it and worry about debris/micrometeoroid strikes. The ideal would be to stick it in some permanently shadowed crater on the Moon, it'd be a stable environment without wild temperature swings and much lower risk of somehow ending up where people are. But that's a long way to go and a lot more risk to take for now.by hgoel
6/30/2026 at 2:23:58 PM
Once it's in orbit the cost of moving it farther out needed be very high. Just evaporating it with solar energy in very high orbit will allow the solar wind to carry it out of the solar system.by pfdietz
6/30/2026 at 2:40:04 PM
Unless you live in Sci Fi future where space travel is magically free, this is a pretty bad deal since sending a pound of spent nuclear fuel out of earth orbit takes 50+ pounds of fuel. Sending all the spent nuclear waste into space would be something like 10 million tons of fuel.by dpark
6/30/2026 at 3:33:44 PM
It doesn't have to be free, it just has to have a low cost. And remember, we're talking not about the cost now, but the cost up to centuries in the future. The ultimate time limit is set by when spent fuel stops being self-protecting against amateur diversion of the plutonium, which is 300-500 years.> 50+ pounds of fuel
Just out of curiosity, how much do you think LOX/LNG propellant costs?
by pfdietz
6/30/2026 at 1:29:42 PM
Can't wait for one of those launch rockets to explode in the atmosphere!by jampekka
6/30/2026 at 2:21:04 PM
And the armored waste carriers to fall back to Earth and be recovered for relaunch.by pfdietz
6/30/2026 at 1:35:29 PM
The requirements for a rocket to be allowed to fly nuclear material tend to be even more stringent than those for flying humans.by hgoel
7/1/2026 at 3:34:20 AM
Haven't you seen https://en.wikipedia.org/wiki/Space:_1999 ?by LargoLasskhyfv
7/1/2026 at 7:06:11 PM
Yes, it's a horrible pile of pseudoscientific TV crap. Why did you imagine it was relevant?by pfdietz
7/1/2026 at 7:46:37 PM
It isn't even pseudoscientific, just fiction, though their 'Eagles' don't need much suspension of disbelief ;->Metaphor. Allegory. Analogy. Parable.
by LargoLasskhyfv
7/2/2026 at 10:09:38 AM
It was intelligence-insulting crap.by pfdietz
7/2/2026 at 1:24:44 PM
It was https://en.wikipedia.org/wiki/Rudi_Gernreich !by LargoLasskhyfv
6/30/2026 at 11:13:07 AM
> "The Trump administration is proud to support the rebirth of America’s nuclear industry and ensuring Americans have access to affordable, reliable and secure energy for generations to come."> "The demonstration and the licensing pathway it establishes represent a key step toward deploying electricity-producing microreactors for U.S. military installations by September 30, 2028."
So which is it? Power to the people or power to the military? This microreactor concept doesn't seem very well suited for commercial use.
by sfn42
6/30/2026 at 11:19:20 AM
Why would microreactor concepts not be suitable for commercial use? History is overwhelmed with examples of large, rare and expensive tech being produced in small cheap packages and becoming massive commercial successes that make the old way look primitive.by roenxi
6/30/2026 at 12:15:09 PM
> Why would microreactor concepts not be suitable for commercial use?Crippling diseconomies of scale.
by pfdietz
6/30/2026 at 11:26:59 AM
Because large scale production is generally more scalable and efficient. And you probably don't want dozens of "microreactors" scattered across cities.by sfn42
6/30/2026 at 11:34:02 AM
> Because large scale production is generally more scalable and efficientRooftop solar is an example of small scale decentralized energy production, maximum efficiency is not the only relevant metric.
> And you probably don't want dozens of "microreactors" scattered across cities
Why not? If they're considered safe and pass all inspections, what's the problem?
by usrnm
6/30/2026 at 11:49:26 AM
A nuclear reactor is generally treated as a high security facility. I don't know how this new reactor works but I thought it was safe to assume something like a terrorist attack on one might be bad. It's also a lot more work to inspect and control them when scattered.Rooftop solar does not have these issues.
by sfn42
6/30/2026 at 11:35:56 AM
On the other hand you can scale production of reactor themselves. And I don't think the idea is to scatter them around, but to have a power plant with dozens of them in one place (instead of 3-4 regular reactors in a regular nuke power plant).by IsTom
6/30/2026 at 11:41:52 AM
I think that may be exactly wrong. The small scale may make it easier for a reactor to be “walk away safe” ie shut itself down absent external activity. I know that is a design goal of some of the Chinese micro reactors and those are used for civilian power generation.Secondly although generating large amounts of power is more efficient in terms of generation, generating power close to the point of use is significantly more efficient in terms of power loss on the grid as I understand it.
by seanhunter
6/30/2026 at 11:43:15 AM
Large scale production of commodity goods is generally more efficient. Which is why microreactors don't seem to have any inherent disadvantages. The efficiencies tend to kick in with the raw number of items produced.by roenxi
6/30/2026 at 12:25:18 PM
> microreactors don't seem to have any inherent disadvantagesThey have diseconomies of scale. Some of the costs of a nuclear power plant scale sublinearly with power. Neutron economy is improved in a larger core. Larger turbines are more efficient than smaller turbines. It doesn't take 1000x as many operators to operate a NPP with 1000x the power output.
by pfdietz
6/30/2026 at 12:34:11 PM
Is that relevant? The economics of nuclear plants doesn't have anything to do with efficiency as far as I'm aware, the fuel costs are relatively negligible. They can afford to be horribly inefficient if they can get economies of scale producing the plant. So you can use inefficient turbines and have bad neutron economy and it wouldn't change the economics by anything in particular.You'd also probably find similar issues with diesel generators, but small diesel generators do roaring trade and have great commercial applications.
by roenxi
6/30/2026 at 12:47:04 PM
Cost is not only relevant, it's paramount. Efficiency is only important insofar as it affects overall cost.Diesel generators have the advantage of being very cheap -- an order of magnitude cheaper than NPPs per unit power output -- and of having much of their total cost being fuel cost, so they can operate at lower capacity factor. But even so, we don't see large power plants composed of arrays of diesel microgenerators.
(The solution for current higher capacity factor diesel users, like say remote operation at mines, would be to supplement them with renewables and storage to reduce fuel costs. This is already happening.)
A significant problem with any small power plant is fixed costs. A 1 MW(e) plant (Antares is said to be between 100 kW(e) and 1 MW(e)) making power at 90% capacity factor and selling at $0.05/kWh will gross about $400K/year. A single full time employee, like a security guard, will cost a good chunk of that.
by pfdietz
6/30/2026 at 12:57:35 PM
> Cost is not only relevant, it's paramount. Efficiency is only important insofar as it affects overall cost.Oh sorry, I thought you were talking about efficiency. Ok, what is the cost is for these plants?
> A single full time employee, like a security guard, will cost a good chunk of that.
I dunno, a 1MW nuclear plant could end up being pretty small. It might easily be economic to install them places that already have security guards.
by roenxi
6/30/2026 at 8:53:41 PM
Back in the 1950's, as part of a study for putting ICBM bases in Greenland, the US Army built a 2MW reactor (PM-2A) and deployed it to the test base (Camp Century) in Greenland. It powered the camp for about three years, modulo a little problem where it was shut down for a while after a prototype (SL-1) killed two soldiers and a sailor in Idaho. In addition, the Navy operated another one (PM-3A, 1.75MW) for a decade in Antarctica at McMurdo Sound, until they cut it up and brought it back to the US. There was also the MH-1A (10MW- and the only one I've mentioned that used LEU instead of bomb-grade HEU) sitting on a freighter in Lake Gatun to power parts of the Panama Canal Zone.All of these reactors were built in the early 1960's and the last (MH-1A) was retired in 1978. All of them were operated in places that had lots of soldiers around (though McMurdo and Camp Century relied more on being really difficult to get to than actual sentries) And they were never replaced. Because even having guards already paid for didn't help the economics of the situation. Maybe things are different now. But I've yet to see any evidence for it.
by mandevil
7/1/2026 at 12:53:10 PM
The SL-1 accident was something. One of the casualties was missing for a short time until they found him speared to the ceiling by a control rod that had been ejected from the reactor.They were all buried in shielded caskets, several feet deeper than normal.
by pfdietz
6/30/2026 at 1:03:46 PM
Microreactors have been tried before by the military, for use at bases, which have guards. They not only didn't make sense to install, they didn't make sense to continue to operate once installed.by pfdietz
6/30/2026 at 11:20:13 AM
"Antares is a nuclear fission energy company developing compact microreactors for defense and space applications"by ablation
6/30/2026 at 11:28:07 AM
[dead]by sfn42
6/30/2026 at 11:50:29 AM
That's just what we needed! Nuclear autotune.by coldtea
6/30/2026 at 8:16:28 PM
Can you please roll back the snark and flamebait in your comments? It has been upticking again for quite a while, to the point where notice I'm bracing myself when I see your username in threads.Since you've adjusted this in the past, I'm sure you can do so again, and we'd appreciate it. We like that you're here, but need you to stay within the guidelines.
by dang
6/30/2026 at 9:10:29 PM
Sure.I never do flamebait and rarely do snark tho (usually only after several increasingly futile exchanges).
Flippant comments (like the autotune one) and/or sincerely held even if unpopular opinions, I'll stoop to, yes.
by coldtea
6/30/2026 at 9:34:42 PM
Thanks! Yes, translated into your terms it sounds like the flippant ones I was referring to.Unpopular opinions are fine in principle - we definitely want to hear minority views on HN. But it's super common for people to pre-emptively load their unpopular-opinion comments with sarcastic or aggressive language, no doubt as a defensive against the anticipated negative reacction from the majority (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...). That never works well. But I'm just speaking generally - I don't know if it applies to your posts.
by dang
6/30/2026 at 12:19:07 PM
We need progress, not a decade per step.That distinction matters because nuclear.
Let that sink in for a moment.
by cadamsdotcom
6/30/2026 at 1:30:02 PM
(psst autotune is made by a company called Antares)by kibibu
