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Comment by PaulHoule | Hacker News Reader

I don't think it's a bad reactor but I looked at the application and it wasn't a good application. (The NRC says the same)

There was a large amount of hand-wringing about the risk of avalanches and other natural disasters that were extremely low probability.

They were skimpy on interesting details about the reactor such as "What do you do if the sodium coolant catches on fire?" (e.g. sodium burns in water, sodium burns in air, sodium burns in carbon dioxide) There are good answers to that in the U.S. and Russian experience. They don't draw on that experience to show they can solve it.

If they fix the application and submit it again it could get approved.

View on HN

I think it is probably a bad reactor and a questionable company.

1. The company is totally opaque on even basic design details. This is not ghost mode. It's likely hiding incompetence and lack of design work / maturity.

2. It's a fast reactor so lots of high energy neutrons that will cause faster material degradation, higher maintenance cost, more downtime - the economics for fast reactors have never worked (not even in Russia or China), and this is probably why fusion reactors will never be economical (32x greater neutronicity).

3. It has terrible fuel utilization: 1% burn-up of fuel, with 100 metric tons uranium / GWe-year compared to 5-10% in other normal and advanced reactors.

4. The founders lie to congress claiming their reactor “can consume the used fuel from today’s reactors” when each reactor is actually going to require 3 tons of pretty pristine HALEU...

5. The founders peddle some serious BS (bitcoin mining, TED talks ... etc) not unlike the other great MIT nuclear startup Transatomic.

6. NRC really went out of their way to publicly reject this with press release and all. This was not done lightly to a company often featured in the WSJ and Popular Mechanics.

7. I'm disturbed by the way they talk about their reactor as a "community meeting place" with their modern glass A-frame without any power generating equipment. Is there going to be a daycare center or country club in there? Where the hell are the cooling towers? I'm all for nuclear power, but we shouldn't be down playing the seriousness of nuclear power systems.

In Fusion reactors the neutrons are used to breed Tritium from the Lithium so they're not hitting the structure and degrading it.

Not quite. 80% of the energy in D-T fusion reactions are released as neutron energy. I sure hope most of that will be used for generating electrical power rather than breeding tritium... :) The dpa rates and helium embrittlement are way higher for fusion and fast fission reactors than for thermal fission reactors. See Figure 3 and 5 of https://www.annualreviews.org/doi/abs/10.1146/annurev-matsci...

You have to absorb the neutrons to capture that energy, so you will always have to deal with transmutation. You can't choose one or the other.

On this case, the lithium absorbs the neutrons and convert most of the energy into heat, while it becomes tritium.

So, we have half a meter of lithium just sitting there, not contained in any structure?

Look to FFTF for a completely successful fast reactor run in the U.S. that was unfortunately shut down for political reasons that, retrospectively, look like a terrible mistake.

One of the most interesting features of the FFTF was a sodium-to-air heat exchanger which is a key to fast reactors having superior economics.

That is, no nuclear reactor which uses a steam turbine is going to be economically competitive with fossil fuel fired gas turbine generators. Between the absolutely huge and massive steam turbine and absolutely huge and massive heat exchangers (look at how big the steam generators are in the PWR or the huge tube-in-shell heat exchanger used at Dounreay)

A closed cycle gas turbine will fit in the employee break room of the turbine house of a conventional LWR. It requires some kind of reactor that runs at a higher temperature than the LWR. I like fast reactors and molten salts but have a hard time being enthusiastic about HTGR and friends.

So much of the literature still looks like a stopped clock. People still compare nuclear to coal although coal has been economic for a long time for the same reason as the LWR... The cost of that huge steam turbine.

Problems with fast reactors I worry about are the fear of proliferation (not proliferation) constricting what you can use for fuel and (more so) the plutonium nanoparticle problem w/ MOX fabrication. Of course you don't need to use MOX or you'd think in 2022 you could use 100% remote handling and not have the problems that Karen Silkwood was worried about at the place where she worked.

> One of the most interesting features of the FFTF was a sodium-to-air heat exchanger which is a key to fast reactors having superior economics. > That is, no nuclear reactor which uses a steam turbine is going to be economically competitive with fossil fuel fired gas turbine generators.

OK, but FFTF reactor has not generated electricity at all. How is “sodium to air heat exchanger” supposed to generate electricity, to make it more economical than steam turbines?

> That is, no nuclear reactor which uses a steam turbine is going to be economically competitive with fossil fuel fired gas turbine generators.

That’s highly likely to be true (at least until cheap gas runs out, which will happen at some point, though it will take many decades/centuries until then), but I thought we are aiming to get off fossil fuels, no? We should be willing to pay some premium for nuclear, because it does not emit GHG.

A next generation nuclear reactor is not going to couple to air but probably to carbon dioxide and then to a powerset like

https://www.sciencedirect.com/science/article/pii/S173857331...

Nuclear also competes with fossil fuel powerplants that capture carbon. There are many options such as: (1) turn the fuel to hydrogen and burn the hydrogen, (2) run the exhaust gas through an amine stripper, (3) burn the fuel in pure oxygen so the amine stripper has less work to do (recycle the combustion products so the turbine doesn't burn up), (4) chemical looping combustion that uses a metal like iron as an oxygen carrier, etc.

The cost of something like that doesn't look crazy, optimizing it is a job for the systems engineering department, you can compress the CO2 to 1500 psi and inject it into saline aquifers which exist in most places. (Drives me nuts that carbfix gets so much press for a process which only works in a few places and consumes much more water than the carbon it captures)

It is not happening because regulators aren't forcing it, there is no carbon tax or carbon credit for it.

You could save the world with a nuclear option that is truly cheaper than the alternatives without subsidy. Anything that involves subsidy is going to give somebody an opportunity to get rich by siphoning off 5% of the credits and keep the gravy train running by paying 1% of that to politicians. Anything like that will run into intense opposition, look like a scam to people, probably be a scam in many cases (extortion like "we'll cut down this forest if you don't pay us" and then the forest gets cut down or burned anyway, unverifiable schemes like grinding up rocks and leaving them at the beach, ...) damage the legitimacy of the government and delay real solutions.

Thank you for your response, it seems to be much better informed about both the technical side, and also the public choice side of the issue, than I typically see on sites like HN.

RE: your last paragraph:

Basically you're praying for China to succeed at this point. They have full blown LFTR research underway and I think other reactor designs under aggressive research.

Alas private funding of reactor designs is a not starter at this moment, with battery/wind/solar in rapidly evolving economies of scale and R&D. Solar/Wind is closing in on beating the leveled cost of gas turbines, and a reactor project wouldn't hit the market for ten years.

What's the economics of battery/wind/solar at that point? Salt water or Li-Sulfer batteries that are ultracheap, ultracheap but decently efficient perovskite or other techs? Too murky.

I agree we should be funding reactor techs in the billion-per-year range in the US (take it from the boondoggle fusion funding if you have to) and keeping close watch on China's progress, but probably all nuclear startups are fraud for the next decade.

You're exactly right here, and I'd say this is well put in several areas.

I'll add that supercritical CO2 sounds like science fiction to people, but it's actually been pretty well demonstrated at the small sizes. The scaling up is what needs to happen if it's used at sizes beyond a few MWe. We've worked with vendors who have these available at the <5 MWe scale.

And I'll second what you're saying about subsidy. The incredible subsidies out there, if I didn't care about fission, would make me agree with those that are effectively anti-nuclear. If those hundreds millions and billions to single companies are necessary to * ever * get a single nuclear plant built, it just doesn't add up that it will be successful without all that propping it up. I agree it isn't necessary to subsidize, and that's how we believed it was important to run our company to date.

In this case, I'll name names, and I hope this isn't taken in a malicious sense because it isn't meant that way. But I've always wondered why Bill Gates, one of the wealthiest humans on the planet, would go to Capitol Hill for money for his nuclear company. I think I've learned that it's for reasons along the lines of what you said there. Creating a self-sustaining government program goes a long way to guaranteeing that the government cares about your company, and anyone else along the trail of $. I'm not blaming that, of course it is smart, it is just intriguing what paths occur.

PS also agree on "carbfix" - that while I'm all for all solutions to climate issues, it is wild to me too how much press that carbfix gets too in comparison to at least my perception of its reality of potential. But i suspect it goes back also to a great govt relations piece...

I went looking for operating closed cycle gas turbine power plants- this seems like a research topic all on its own, no matter the heat source.

It's definitely true that simple cycle gas turbine plants are much cheaper than equivalent size steam plants. This right here sets the bar for any kind of thermal power plant.

See table ES3 for cost comparisons..

https://esmap.org/sites/default/files/esmap-files/TR122-09_G...

Can you elaborate as to why you aren't excited about HTGRs?

Gas is poor as a heat transfer medium, so the reactor vessel is both very large (power density is on the order of one tenth of current LWR designs) and has to withstand high pressure. Hard to make such a thing economical.

OTOH, the high temperature opens up interesting industrial applications outside electricity generation.

HTGR has faced numerous development problems.

One of the coolest sounding ideas is the "pebble bed" reactor where you have carbide coated spheres that are fed into the top of the reactor and get withdrawn from the bottom, taken up an elevator and replaced.

When they tested this out in air the spheres we well lubricated and slipped past each other. In hot helium the Germans found that there was a lot more friction and the spheres were sticking to each other, cracking, getting stuck, and releasing radiation.

"Prismatic" designs where the same material is in blocks seem a little more promising. Still the reactors haven't done that well and as lurid the stories around the plutonium economy have been, the ratio of progress to problems for the liquid metal fast breeder reactor has been better.

We know how to bury oxide fuels for the long term and we know how to reprocess them. If there is a "what to do about the waste" problem it's that we can't make up our minds. Carbide fuels can be encapsulated in concrete and stored for the medium term but the actual mass and volume of the fuel is dramatically more than the LWR fuel because of the low power density. The long term stability for burial is not established, and the amount of material is 10x more. Reprocessing is not developed and faces the problems of dealing with a large amount of 'filler' that is going to be somewhat radioactive and have to be dealt with.

China's HTR-PM pair of test reactors is now grid connected. We'll see how it performs over the next few years.

The demonstration High Temperature Gas-Cooled Reactor - Pebble-bed Module (HTR-PM) at the Shidaowan site in Shandong province of China has been connected to the grid, the partners in the consortium building the plant have announced.

https://www.world-nuclear-news.org/Articles/Demonstration-HT...

> the plutonium nanoparticle problem w/ MOX fabrication.

IIRC the Oklo design is using metal fuel, like EBRII or IFR? And the Russians are apparently working to switch from MOX to nitride fuels in their fast reactors.

Anyway, the French have been producing MOX fuel at industrial scale for decades, AFAIK without poisoning their workers. Maybe they are doing it smarter than the Americans in the 1970'ies.

I have been trying to figure it out and my guess is this.

At that factory Karen Silkwood worked (fuel for the FFTF) at they were making the workers wear respirators 100% of the time because they couldn't eliminate detectable particles.

I think in the US that's considered unacceptable. I think the French consider it OK.

The French tried to build a MOX factory in the US near the Savannah River Site last decade and it was never completed. I think there was some circle they realized they couldn't square. The UK was able to reprocess nuclear fuel and produce plutonium powder but they were unable to turn it into quality MOX fuel.

Metal fuels have a small particle problem too but you can melt the metal, pour it into a glass tube, then break the tube... All things straightforward to do with remote handling in the 1950s.

On paper nitride fuels are very high performing but I have no idea what goes into making them. It seems that with advances in robotics remote handling in fuel fabrication should be capable of much more than it ever was.

> At that factory Karen Silkwood worked (fuel for the FFTF) at they were making the workers wear respirators 100% of the time because they couldn't eliminate detectable particles.

Hmm. Dealing with Pu dust is a well known problem. Nobody knows exactly why, but Pu dust has an amazing capability to rapidly contaminate things. Best guess is that the high alpha activity of Pu produces a lot of recoil events propelling the Pu dust particle around (increasing it's diffusion constant, if you will).

I don't know exactly what the French do to make it work, is it PPE's, robotic handling or whatever.

> On paper nitride fuels are very high performing but I have no idea what goes into making them.

It's in some respects similar to making oxide fuels, you first somehow create microgranules (hopefully evenly sized) of the fuel which you then sinter into pellets. Nitrides, however, present several additional challenges. But it seems that these are not insurmountable problems, it's just that oxides have a large head start; and nitrides not being compatible with LWR's doesn't help finding R&D money either. Here's a recent overview: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6267113/

Personally I'm somewhat bullish on nitrides, if large-scale use of metal cooled reactors ever becomes a thing, that is.

> 2. It's a fast reactor so lots of high energy neutrons that will cause faster material degradation, higher maintenance cost, more downtime - the economics for fast reactors have never worked (not even in Russia or China), and this is probably why fusion reactors will never be economical (32x greater neutronicity).

Commonwealth Fusion Systems's ARC has an interesting approach to handling this -- using a liquid blanket which can be circulated. Of course, ARC isn't built yet! But if that approach is workable, perhaps it can be applied more generally?

I believe it has to be replaced every 4 years of operation as intermediate level radioactive waste.

Does it produce less waste than a fast reactor without the liquid blanket?

The replaced blanket itself is waste, so I'd venture to say no?

CFS claims that it's manageable, although I don't know enough to evaluate that claim. It's also not clear from this quote if the once/twice per year is referring to full replacement of the vacuum vessel, or maybe just to inspection or replacement of a subset of components.

"Bob Mumgaard, CEO of Commomwealth Fusion Systems, regards neutron flux as part of a fusion power plant’s wear-and-tear—a routine aspect of its servicing cycle, happening perhaps once or twice a year. “We can simplify the internal components, develop maintenance scenarios,” he says. “We have such a scheme substantially in place.”" https://nautil.us/issue/86/energy/the-road-less-traveled-to-...

Well we're all creatures of opinion; but there is a lot here without much real backing. We have a similar post on tech forums for almost every company from Apple to ... I can't think of a company name starting with Z, Volkswagen will have to do. And pretty much every startup if someone cares to look in to them.

Cynicism is extremely easy. Every company looks dodgy from the outside and most of them are dodgy. Many such posts turn out to be correct. But that is because cynicism is misplaced - the point of these startups is that some of them will, despite looking dodgy, turn out to be keystones for trillions of dollars of industrial success.

The upside of a serious energy revolution completely outweighs any of these points raised. There needs to be a way for dodgy-looking startups to experiment without just getting a "nah, this year's work is a write off. Oh well lol" from regulators.

> from Apple to ... I can't think of a company name starting with Z

Zeppelin? :)

https://zeppelin-nt.de/en/homepage.html

That's cool! Nice pictures and a couple good videos of the Zeppelin in flight. I was a bit disappointed not to see any ads for beer on the side of the Zeppelins. Seemed like a marketing miss.

Zbiotics! https://zbiotics.com/

I completely agree - but let's call it scientific research not startups.

Startups are about industrialising existing working processes. What we are missing here is the multiple different funded experiments that take the different combinations of salts, heat exchangers and so on and come up with "hey this one works best" - make these.

Funding these experiments through VC is just asking for bias and PR not empirical results.

In short, if the government was running 100+ experimental reactors, this press release would be "whoops, 99 to go" and not even create a stir. It's only because there is 100M at stake is anyone fighting back.

Zeit unfortunately is now Vercel

Zillow?

Zenefits?

> the economics for fast reactors have never worked (not even in Russia or China)

Russia currently has two sodium-cooled fast reactors that are producing power, the BN-600 and BN-800. They also have another sodium reactor under development, the BN-1200. BREST-OD-300, a lead-cooled fast reactor, is under construction as well.

But those don't have to be economical purely on power generation, right, because they also produce Pu-239? Presumably fast breeder reactors would be useful to the Russian state even if they didn't produce electricity at all...

There's no evidence that they are being used to breed plutonium. In fact the BN-800 burns a mixture of uranium and plutonium to reduce their weapons stockpile.

They have RBMKs which will produce 10 times that, and more cheaply.

They went bankrupt with their arsenal once, so I'd argue it would be more useful to their rivals.

> I'm disturbed by the way they talk about their reactor as a "community meeting place" with their modern glass A-frame without any power generating equipment

I'll submit that a nuclear startup that presents such a stylish Architectural Digest concept for its facilities, that by itself is enough for us to be extremely skeptical of the leadership team. Their head is in the wrong place.

You will counter-argue that it takes little effort for them to hire an artist-designer to create the rendering. Nonetheless: their head is in the wrong place. They're not reading the room. None of us (not the public and not the NRC) are looking for a new alpine lodge to grab an espresso. We basically just care that you don't blow up and you don't poison the land, water, and air around you.

If leadership spend any cycles to spend on hiring a stylish designer, then their priorities aren't straight.

I am all for style, but they aren't sending the right message. There's a certain beauty in a cartridge reactor that is buried below grade and shows hardly anything.

like this one? https://usnc.com

Fair point, but when we examined just having everything underground, it was more expensive actually. Once you consider operational realities in a remote environment (especially in permafrost), it is beneficial to have power conversion equipment indoors, offices, a bathroom, storage areas, etc. and then you're talking a building above ground anyway. There is security protection built in too that I can't elaborate on.

Presumably they're trying to shift the image of a nuclear plant from "dangerous, not in my backyard" to something more friendly and appealing.

NuScale Power's choice of communicating this seems a lot better. By contrast this is just like rendered images of hipster micro lodges in the mountains. For a nuclear reactor. A glass metal frame structure? It doesn't inspire safety at all. In the mountains? An avalanche could raze this structure in the blink of an eye.

It's a good thing then that we analyzed to such extreme events as completely losing everything above ground, whether due to an avalanche, a tornado, an earthquake, etc, etc. :) The inherent safety in the fuel type means that there would still be zero dose. (for more info on the tests that showed this result originally in historic research reactors in operation: http://www.thesciencecouncil.com/pdfs/PlentifulEnergy.pdf)

PS I realized that you thought the structure was glass. No wonder. It's not, it's steel panels. Modular construction. There are optional solar panels on the exterior, maybe that's what you saw.

At least use an image of a panel, not glass, geodesic dome then and don't try to sell it as a community meeting point. That's a more acceptable current day view on how a nuclear reactor should look. Also cut the bitcoin BS. It's like trying to associate your project with Bernie Madoff. The hardest thing is to change people's perception and radical approaches don't cut it in this case.

I edited the above comment instead of replying here (whoops). I realized that you thought the structure was glass. No wonder. It's not, it's steel panels. Modular construction. There are optional solar panels on the exterior, maybe that's what you saw. Please see the other comments on why having a heated, lighted building space is important in the communities we've gotten to know. Bitcoin isn't BS when it's a first moving customer, even while we are actively working with plenty of other customers you'll recognize well, when the time comes to announce. It takes time.

It would seem that both could be possible, but you're the expert here. ;) We didn't have to spend much time or money on an actually nice looking design, and the a-frame has a lot of practicalities I'm happy to talk about more (modular construction, resilience against snow, useful angle for the solar panels, strength for the internal cranes). (and yes, the power generating equipment, offices, and other space, is inside)

I guess then again here I am as part of the leadership engaging in communicating with the HN community on a friday night and hopefully transparently answering questions. I guess I can't help myself! I do think the public needs to both learn about the realities of fission, and I don't think it has to be ugly.

> I guess then again here I am as part of the leadership engaging in communicating with the HN community on a friday night and hopefully transparently answering questions.

Are you trying to guilt trip people by showing your dedication? It's in your own interest to do this, if you don't feel like it go and watch TV or something and don't bother. "Here I am on a Saturday morning commenting on HN etc..."

Haha not really. :) I was pretty much laughing at myself, responding to the commenter's idea that Oklo leadership shouldn't be spending cycles on building parameters with architects (i did - it's arguably important on a number of levels - security, regulatory, cost/finance/constructability, human factors, community relations etc...) but here i am spending cycles on like HN comments instead of other work which of course we do all weekend anyway.

Oklo has hundreds of pages of information on safety and all kinds of details of their design that is fully public. To say they’re hiding something is ridiculous and disengenuous.

Don’t claim they are lying to Congress about being able to reuse waste. You are the one who is blatantly lying about this to the point I wonder who’s paying you? It does not require “pristine haleu”- the very first reactor is using waste from Idaho National Labs. The DOE and Oklo are also working together on a waste-to-fuel factory as a second project. The fact you’d make up this information is reason enough to question both your motives and the entirety of your post.

Transatomic is nonexistent and Oklo chose not to work with them for a reason. They are quite different.

You also clearly don’t know anything about the NRC and their dealings with this company; they are working with Oklo currently on approval process.

Again, you seem uninformed on this company and their tech; the entire thing is small and on shutdown creates only as much heat as a riding lawnmower. So yes- there can be a country club or a daycare or whatever else you want to put on top. That’s part of why it’s so safe and needs to be approved. I question that you’re actually for nuclear power at all; if you are, stop making up lies about a revolutionary company working to solve our energy crisis.

Engaging in personal attacks is not the way to fight disinformation. This comment will likely be down voted and flagged into oblivion.

Take a look here for guidelines on how to comment on HN: https://news.ycombinator.com/newsguidelines.html

Excuse me- they are the ones claiming this company is lying to Congress, which they are not, and this person has zero proof of. In no way was I personally attacking- I am correcting their blatant lie. You should be standing up against a commenter making up lies about a small company in a huge space that’s doing amazing work.

> You should be standing up against a commenter making up lies

I am trying to help you understand how to do that effectively yourself given that you appear to be new to the site (given your account age) and unfamiliar how to effectively communicate in this community.

People are frequently factually wrong. You will be more effective at correcting those factual errors if your tone remains civil, focused on facts and especially if you provide good citations to back up your corrections.

Additionally, calling out people as shills is specifically discouraged here as it does not lead to productive discussions. If you are concerned that someone is a shill, you should send an email to the HN moderators as they do investigate.

This is also explained the the guidelines (which really are worth reading.):

> Please don't post insinuations about astroturfing, shilling, bots, brigading, foreign agents and the like. It degrades discussion and is usually mistaken. If you're worried about abuse, email hn@ycombinator.com and we'll look at the data.

> You are the one who is blatantly lying about this to the point I wonder who’s paying you?

Ah the good old I disagree or you are wrong therefore you must be a shill accusation. That one is so boring it is actually part of the guidelines so if you're wondering why your comment is dead, that's it.

Hey Gloriana, I'm sure PR experts would say I'm probably not making a good decision responding here, and I haven't even had anything to drink, but I'll take a stab at sharing a bit on each of your points. I hope this response will be taken in the good faith in which it is given.

1) There's certainly many hundreds of pages/slides in the fully public docket on the NRC website, but the easiest source for the most information in one place is our application itself: bit.ly/AuroraCOLA. I don't expect anyone to want to read that entire thing either, but it's there. The only main things that are withheld are generally either: export controlled (defined by the Department of Energy, and we take it seriously) which includes detailed core maps, or security-related information (defined by the NRC). But the rest of it is all there. If there's something you want to know that isn't there, I'm happy to respond.

2) We are building our designs off the 30 years of experience and data with EBR-II and other fast reactors (http://www.thesciencecouncil.com/pdfs/PlentifulEnergy.pdf). EBR-II was ended prematurely for political reasons and had plenty of life left. The EBR-II showed how electricity could be put on the grid with higher uptimes than even the commercial fleet at the time. Unfortunately, I can't give details, but let's just say other major developers of historical fast reactors didn't release their economics because they didn't want it to cannibalize their other plants. But you don't need to believe that either. Our business model is to provide power via PPA so if the economics don't work for the customer we simply won't have a deal. Our FOAK plants are economic already in remote or higher cost areas, but the real key to our economics is when we are able to recycle existing waste, a fact unique to fast reactors.

3) 1% was really to be conservative for the FOAK, to try to make the licensing of the FOAK simpler within the datasets we had. I assume you know a number of SFRs have worked toward establishing datasets for up to and beyond 15% burnup. I really don't know where the number of 100 MT of uranium comes from. We would have <5MT total of fuel for 20 years, with <1T of that being uranium. 1.5MWex24hrx350days/yrx20 years is something like 250 GWe?

4) Oof. Yes, fast reactors can consume the fuel from today's reactors, and even though that supply chain isn't established, the FOAK is using waste fuel from EBR-II. I can assure you it is not pristine. No one else wants it. :) But we are working together with the DOE on a project with Argonne National Lab to begin work on the recycling from today's reactors (https://www.energy.gov/articles/doe-announces-over-65-millio...).

5) Hm. well, I want to be positive here: I'd argue there's a difference between our first customer announcement being Compass and a TEDx with my alma mater, and moving forward for years with something that fellow students and professors said had fundamental issues since grad school, which a professor finally leaked to the press out of frustration (and yes, we might have been fellow students). It's funny, I always said we should never do a TED too because they seem so smarmy, but a friend at my undergrad and the students there were organizing a TEDx and honestly it was cute and was just a fun opportunity to go back there for various reasons. We've been working with other more traditional customers in ways that we can't announce yet. But, we are working with other customers you'll likely approve of more. Remote communities as well as big companies just truly do need reliable power and they do want it to be emission-free.

6. They did seem to go out of their way didn't they. More will come on this once we are able to put out our own account too after 30 days, just because we should have the opportunity to set the record as well. But, to put myself in their shoes, they are trying to defend against an appeal or legal action. Neither of which we really have interest in, we just want to try again, move forward.

7. I responded to this with Paul. TL;DR: I don't think an attractive and functional building with all required security and operational characteristics means we are "down playing the seriousness." If you've been out to these truly poor, remote communities in the Arctic circle as I have, you'll see why they care about having heated, lighted, indoor areas in the long winters. And when the analysis shows the safety and security required, why wouldn't we offer that to them?

Well, there you go. Feel free to pick it apart but hopefully it added some context to the press releases and pretty pictures and whatnot.

Thanks for the response.

I had previously gone though the Oklo COLA, which is indeed hundreds of pages. But quantity is not always quality. I have seen the same types of submissions from other reactor proponents, and they are far more detailed, comprehensive, and informative and they are mostly at earlier stages of NRC engagement in pre-application discussions. As an example, I can't find a basic dimensioned or labeled reactor drawing or system diagram in Oklo's COLA. As far as the COLA illustrates, the Aurora design consists of an A-Frame drawing and a cylindrical vessel in a dugout. The safety analysis provided are generally simplified, rarely showing uncertainties or limitations of the analysis. See the NuScale or GE-Hitachi designs in pre-application or even the Transformational Challenge Reactor (TCR) as an example of a well documented research thrust that has not even begun the regulatory process if it ever will: https://tcr.ornl.gov/publications/

As far as spent fuel goes, the EBR II fuel that Oklo plans to use took decades to reprocess at a cost much greater than 0, which Oklo is not paying for. EBR II is not a civilian power generating reactor like all LWRs and BWRs currently in operation. Perhaps one day, reprocessing spent fuel will be cost effective. But today, it is a totally unnecessary activity as there's plenty of uranium and spent fuel storage is not an issue. I think telling congress that Aurora will consume spent fuel from today's reactors is false and disingenuous, both because it is extremely expensive to do so and because it is not particularly useful.

Aurora is ostensibly a tiny fast reactor, though I have to guess at this as there are no dimensioned figures in the COLA. Neutron leakage is going to be big and burnup low. This might be why Aurora is limited to 1% burnup. Maybe Oklo plans to make much larger reactors in the future, which have very different safety characteristics but can achieve higher burnup. It's curious that of the 70+ reactors in development, there are no fast spectrum and tiny reactors except for Oklo. There are fast reactors like TerraPower Natrium but they 200x larger than Aurora.

The calculation for tons / GWe-yr is as below assuming a 33% efficient power cycle (reasonable given the low temperatures of the heat pipes, but maybe the sCO2 is really good). GWe-yr is a unit of energy.

1.5 MWe * 20 yr means you are producing 4.5 MWth for 20 years, and must have fissioned 35 kg of Uranium (you get 200 MeV per U fission which is 2.6 MWyr / kg U). If 1% burnup is assumed, as indicated, Aurora is using 3500 kg or 3.5 tons of HALEU. I think this would change a bit depending on the spectrum.

3 tons HALEU / (1.5 MWe * 20 yr) * (1000 MW / 1 GW) = 100 ton HALUE / GWe-yr

Thanks for the followup as well. I'll just respond on a couple of the points:

- you don't see these detailed core schematics with analyses because in our design they are designated export controlled (ECI) as I mentioned. It doesn't mean that they aren't in there or that they haven't been extensively performed and documented.

- the endeavor (and cost) of downblending EBR-II fuel over many years has been based on the national and state nonproliferation agreements to downblend this high enriched used fuel from EBR-II. Don't confuse that endeavor with processing used, low-enriched fuel from existing plants. In the one case, the downblending work was being performed for many years in the interest of downblending before storing as waste (except now, instead, it can be used to produce clean power and demonstrate a FOAK fission plant). In the other case, recycling existing waste, we are already working with DOE (and starting NRC interactions) about deploying recycling existing nuclear waste for fuel. I can tell you it's incredibly cost effective for a fast reactor to utilize the TRU in existing low-enriched waste and that is our goal for not just feel-good reasons but also for economic reasons. It is not false nor disingenuous.

It's true that the burnup is far less than would be ultimately most economically efficient. The FOAK was intended to serve as a bit of an MVP as I already mentioned. But it's key that larger doesn't mean less safety. The fundamentals of the safety in this case lie in how the fuel has inherent shutdown characteristics, which were proven true of EBR-II (at 65 MWth) even as it's true of Aurora (<10MWth). Many different plants have different mechanisms of safety at various size ranges!

Thanks for engaging and your thoughtful responses.

This is a great assessment of the response by the NRC. The operating phrase to focus on is "without prejudice," which in this context means "just fix the problems and try again."

We applied for a direct to phase 2 SBIR in 2020 and were thoroughly denied, mostly due to fixable errors in our application that we made because we put it together ourselves and had never applied for a grant before. After involving some consultants and the relevant institutions, we got a much lower impact score and are likely to receive the grant soon.

Moral of the story: you can't fake regulatory experience, and regulatory applications require specialist knowledge to put together correctly.

I wish them all the best in their resubmission!

Congratulations on (hopefully!) getting a phase 2 approved, that can be a breath of life for a lot of smaller companies.

> you can't fake regulatory experience

While that seems true, but reading previous applications doesn't help?

> and regulatory applications require specialist knowledge to put together correctly.

Again, seems trivially true, but (again) how come you can't copy-paste a previously accepted application? (I mean, if you find a very similar site, same risks, hazards, geology, weather patters, distance from population centers, blablabla, same technology, same trade offs... shouldn't it be okay? [assuming the regulations haven't changed])

Nobody has gotten an application approved for a new reactor (e.g. not an LWR) yet.

It's not that the NRC is unfair but it is like private spaceflight. For years there was talk at best. Designs like

https://aris.iaea.org/PDF/4S.pdf

have been up in the air for decades but nobody was serious about getting approval and building them. Oklo ought to be proud to be the first to get shot down, pick themselves up again, and submit a better proposal.

Most regulatory consultants give hyperfocused advice specific to your application, and cost in the ~$10k order of magnitude, sometimes pushing the ~$100k. Given the capital investments in applications, you'd be hard pressed to find successful, complete applications with enough details relevant to your proposal that you could simply plagiarize them.

For reference, our SBIR submission was over 200 pages, much of it containing _incredibly_ specific technical documentation about our system, clinical protocols, statistical analysis plans, etc.

Point being, it's not as simple as copy pasting a known good application.

And it shouldn't be. Without the relevant knowledge to make the application you shouldn't be receiving the 'go'.

But is this the one that got approved?

So 200 pages of technical details seems like a pretty good thing to go over, understand and then base a new application on.

The regulations have a laundry list of things that need to be included in the application, right? Looking at bad and good applications helps form a mental model of how one has to actually present the answers to those items on the list.

Of course it's not literal copypaste but which part is black magic from a system integrator point of view?

Of course hiring someone who wrote a few successful ones helps, but they are also basing their new work on their previous one, no? (Again not letter by letter obviously. And in some cases some sections require more depth, more detailed answers, in some cases they are not applicable, but good applications are similar to each other, because they are complete, they cover all the required risk assessments, etc... if not, what going on, could someone help me understand this?)

Sodium-cooled reactors have a long and troubled history.

* Sodium Reactor Experiment (Leak, minor sodium explosion, decommissioned)[1]

* Monju Nuclear Power Plant (Sodium fire, never worked properly, decommissioned)[2]

There's even been a sodium fire at a solar plant, one of those big focused mirror systems.

Many of these new reactor designs are based on complex arguments that the worst-case accident doesn't require a huge, expensive secondary containment vessel capable of containing a major accident. That's a tough sell, since Chernobyl didn't have a containment vessel and Fukushima's reactors had ones that were too small. On the other hand, Three Mile Island had a big, strong containment vessel, and in that meltdown, it held, containing the problem. In all three accidents, the actual accident was worse than the design maximum credible accident.

The NRC is right to be skeptical of weak containment designs.

It's frustrating. The reactor designs that have worked reliably for long periods are very simple inside the radioactive portion of the system. Sodium reactors had leaks and fires. Pebble bed reactors had pebble jams. Helium gas-cooled reactors had leak problems. Molten salt reactors include a radioactive chemical plant. So nuclear power is stuck with water as a working fluid.

[1] https://en.wikipedia.org/wiki/Sodium_Reactor_Experiment

[2] https://en.wikipedia.org/wiki/Monju_Nuclear_Power_Plant

Not all MSRs have the radioactive chemical plant, just the thorium-fueled ones. Several MSR companies are working on uranium-fueled versions; e.g. Terrestrial Energy, where the reactor core is a sealed can that gets swapped out every few years.

I am a fan of the can.

Here's some footage of Monju - pretty scary: https://www.youtube.com/watch?v=DRJGHWbIxC0

EBR-II and FFTF were 100% successful in the USA. Russia has also had very good experience with fast reactors. Sodium fires are a problem, but fires happen in industrial facilities all the time, you just detect them and then you put them out.

Monju had many things wrong with the design, it was a loop-type reactor that nobody is talking about building anymore. Also it was nowhere near adequate from a seismic perspective it is kinda shocking they were allowed to build it at all.

Water reactors have no future for the same reason nobody has built a coal plant since 1980. The steam turbine and associated heat exchangers are unacceptably large and capital intensive compared to modern fossil fuel power plants based on gas turbines. (Look at how huge the steam generators are for the PWR)

Even if the construction problems were solved for the LWR, the economics will not work, you are better off capturing the carbon from a fossil fuel gas turbine plant and pumping it underground.

For nuclear power to be competitive we have to develop closed cycle gas turbine powersets. The 1970s model was that a fast reactor would be more capital intensive than an LWR but with the CCGT advanced reactors could be possibly be competitive -- if we can develop the powerset and reactors that run at high enough temperatures (not water) to support the powerset.

> Water reactors have no future for the same reason nobody has built a coal plant since 1980. The steam turbine and associated heat exchangers are unacceptably large and capital intensive compared to modern fossil fuel power plants based on gas turbines.

Hmm, seems China, India and Indonesia are still building them at a rate of one per week or so, unfortunately. Heck, even Germany opened a new coal plant last year.

The hard coal power plant Dattel was planned in the 2000s and serves as a replacement for three shut down power plants. It was the last coal-fired power plant that will ever go online in Germany. It has to be shut down in 2038 due to the general phase-out of coal.

In France too they had a troubled history.

https://en.m.wikipedia.org/wiki/Superphénix

https://en.m.wikipedia.org/wiki/Cadarache

France has recently given up entirely on fast reactors, mothballing their proposed new program.

https://www.powermag.com/france-scraps-fast-nuclear-reactor-...

In addition to be bad news for fast reactors, this also means France does not see nuclear being a major factor in avoiding global warming (a nuclear powered world using burner reactors would run out of uranium very quickly, or would need to tap vast new sources at dubiously low cost.)

At least it gave up building them as public projects. They really want to control costs. Get the most boring thing possible and make more of it cheaper. (The EPR 2 project.)

The French Superphenix is the butt of jokes, but France really has led the world in (1) reprocessing spent fuel, and (2) really fabricating the extracted plutonium into MOX fuel and putting it back into reactors. Everybody else has been too scared of the high energy ball mill and the plutonium nanoparticles that it makes.

(Ok, the Russians are serious too about using MOX in fast reactors but they've developed an alternative to the high energy ball mill.)

The supply of uranium is vast if you consider seawater as a resource. If burner reactors can be made economical in terms of capital cost we could possible make seawater uranium work. With a breeder cycle seawater uranium would certainly be affordable, we'd wind up spending a lot more on the rest of the fuel cycle.

Reprocessing only makes sense if you're going to put that separated plutonium into a fast reactor. MOX fuel's value for LWRs is so marginal that it's not worth reprocessing spent fuel to make it.

Seawater uranium extraction would have to be scaled up by a factor approaching a trillion if nuclear w. LWRs is going to fuel the world (to in excess of 1 million tonnes of natural uranium per year), and it would only last a few thousand years.

A few thousand years is plenty of time to come up with alternatives.

It's illustrative of the scale of U extraction that would be needed. A single 1 GW(e) burner reactor would require a field of U absorbers covering 170 km^2 of continental shelf (and to supply 18 TW of primary thermal energy would need about 6000 such reactors). The power/area would be considerably worse than solar (with solar capacity factor taken into account).

Anyway, I don't believe France (or anyone else) has any major program to bring seawater uranium extraction to market either.

> So nuclear power is stuck with water as a working fluid.

Steam explosions :|

Isn't a sodium fire suppressible by throwing powder/foam on it?

Isn't a containment building that can dump powder on a fire much cheaper than one that is able to withstand explosions?

Also there are non-flammable salts (eg. FLiBe)?

"Molten salt reactors include a radioactive chemical plant"

So.... what happens with solid fuel rod processing that is any different?

Well, I guess they just bury it rather than trying to consume all the fuel?

I think all reactors are evil until proven otherwise. Avalanches and natural disasters happen.

Do we really want nuclear anything in remote areas without human guards? What if someone decides they might like to cause an unnatural disaster?

Everyone says nuclear is safe... but where's the proof it would still be safe without the level of hand wringing we currently have?

If someone wants to do nuclear, they have to prove it's safe. Move fast and break things has no place here.

> Move fast and break things has no place here.

This.

This is exactly why I always find it fun to read discussions about nuclear power on HN. Lots of people here are hardwired to only think in terms of software (where it's all 1s and 0s and you can do whatever you want), and then they apply that thinking and logic to real world engineering fields and the logic collapses. Doubly so for the nuclear sector because you can cause catastrophy if you aren't careful.

I can't say what kinds of security analyses we had to do to meet regulatory requirements, because there's a host of things you have to do to even know what security requirements there are. That's not even close to publicly available, for good reason.

I can say we have to analyze to massive vehicle bombs, armed assault, etc.

Here's what the possibly interesting, counterintuitive analysis showed. If you have a plant where a massive bomb can't cause damage to exceed regulatory standards (...we are talking about a truly miniscule amount of material here in this micro fission powerhouse in comparison with the nuclear plants you are probably thinking of... literally not more than a meter tall and wide, underground, below layers and tonnage of concrete and steel) and if an armed assault can't cause damage like that either, are you doing a favor by having a host of armed people on site? Probably not, in fact. Insider risk is then too large. There you go!

(totally agree with no "move fast and break things" here. I'm about 8 years into working on this company and still see many years ahead. we wouldn't be doing anything great if we weren't bringing forward the safest emission-free power plant to reality)

The question that should be asked is if the faults of the application is severe enough that its worth continuing burning fossil fuels until/if there is a new and better source of energy. That is the counter part when determining a balance between the need for strict regulation and risk assessments. The damage we know we are causing with known technology, or the damage we might cause with new technology.

We have this kind of cost-benefit assessment in other regulations. It is always a trade off between the benefit of having them vs the cost of not allowing it, be it a new food safety restrictions or building codes. A replacement for diesel generators might be worth a slightly higher risk given how much damage those fossil fuel generators do to the environment, and the global commitment to prevent climate change.

That question does not need to be asked. Nuclear power is dangerous and needs to be done with extreme care and extensive regulation. A worst case nuclear disaster can have local and not so local effects which are worse, sooner, and longer lasting than any global warming threat. If you are careful those things don’t happen.

Alternatively, “we asked that question and the answer is ‘yes’.”

I suspect that the current state of things is that nuclear is overregulated on a 'consequences to humanity' basis but not necessarily on a 'convincing humanity to let us ever build more nuclear plants' basis.

Nuclear accidents contaminate a few thousand square kilometers for a few hundred years at the very worst. Global warming threatens the stability of the whole ecosphere and carbon dioxide levels in the atmosphere decrease in timeframes on the order of tens of thousands of years.

If you're competent and do your job correctly then it's possible to get NRC approval on the first try. Doing it right doesn't have to be slower or more expensive.

> if the faults of the application is severe enough that its worth continuing burning fossil fuels until/if there is a new and better source of energy

You make it sound as if the only two options we had were to build these reactors or to burn fossil fuels. These are not the only two options that you have.

We can keep working on these reactors for another ten or fifteen years while we put maximum effort into building PV and wind turbines and electrifying everything. It's easy to have 50% renewables on your grid with essentially no storage at all. The world is very far away from getting 50% if its energy needs from renewables.

Can you say more about this? I'm glad the top comment here is actually about the application itself and would love to read more about this.

You can access Oklo's public combined license application at http://bit.ly/AuroraCOLA, and read more about what's next for Oklo here - https://okloinc.medium.com/whats-next-566bb49b74dc

> There are good answers to that in the U.S. and Russian experience.

What are your personal favorites of what those good answers are? One write up I found [1] doesn't go into much engineering details, and I find similar high-level descriptions elsewhere.

This reminds me of a documentary I once saw about what seemed to me a completely balls-to-the-wall experimental lab (the best kind) studying the earth's magnetic field by rotating a 12+ ton ball of molten sodium.

The way they solved the fire question was by suspending dewars of liquid nitrogen above the ball of death metal. The only way I could think of to improve upon that is a passive trigger design, wrapping the ball with walls of dewars with spring-loaded lids that open up when pressure drops below the level that the liquid nitrogen is normally contained at. If one is breached, they all breach at the same time enveloping the entire sodium footprint.

[1] http://nucleargreen.blogspot.com/2010/01/fire-in-sodium-cool...

Sodium fires are often flashy but not that bad. They look scary because they form hot aerosol particles that radiate a lot of light and heat. It's nothing like a hydrogen fire you might walk into before you see or feel anything.

Sometimes you spill a few liters of sodium and it goes poof and makes some caustic aerosol you have to clean up. If the heat exchanger with a carbon dioxide secondary pops it forms a crust that will probably keep the carbon dioxide inside. Even if a water tertiary heat exchanger develops a pinhole leak the reaction happens on a 2-d surface and develops more slowly than you might think it would.

https://www.fireengineering.com/leadership/dry-extinguishing...

https://www.osti.gov/etdeweb/servlets/purl/21330020

https://www.osti.gov/biblio/6669413-xoXD4J/

Russians documented hundreds of fires at a reactor in the 1970s most of which were little poofs, they kept calm and carried on because the prize is clean energy to power civilization for 1000s of years.

Every time I hear "liquid sodium" I think "run away!" How in the world would you make that safe even without the nuclear stuff?

(1) Argon cover gas

(2) Fires happen all the time in industrial facilities. You detect them and put them out. US and Russian literature tells you how it is done. EBR-II, FFTF and BN-800 point the way. Japan shows you how not to do it. (Not detect the fire for a long time, lie to the media about how bad the damage was)

> You detect them and put them out.

Well, not molten sodium. You don't put it out. You isolate the fire and let it run.

See https://www.osti.gov/biblio/6669413-xoXD4J/

> Fires happen all the time in industrial facilities. You detect them and put them out.

When we're talking about sodium fires in a nuclear facility, though, this comment reads to me like possibly a wry joke? I'm not even 100% sure it wasn't one, so apologies if I am responding inappropriately. It rather reminds me of an emergency physician I know who likes to comment that gunshot wounds are easy to treat; it's mostly a matter of plugging the hole. He enjoys seeing how saying it makes people squirm.

It's meant to be serious and funny at the same time.

Sodium fires are a real problem but they are manageable. If you detect the fires and put them out they are a minor problem. If you let the fires get out of control, let them wreck the equipment room next to the reactor, then try to cover up how bad the damage was to the media that is the Japanese experience with Monju.

People don't realize that Japan led the world in nuclear accidents from 1990 until Fukushima. There is something badly wrong with their safety culture that led to problems at Tokaimura and Monju and their choice to not install a proper backup electrical system at Fukushima. Choosing not to spend $1M to fortify their diesel generators that would have saved billions and billions. Remember it is a choice.

USA and Russia have dealt with the problem realistically and run beautiful and clean machines with sodium coolant. This is one of the nicest industrial facilities I have ever seen:

https://www.youtube.com/watch?v=Y0Cx2nZTgQg

> There is something badly wrong with their safety culture

I would not be surprised at all if their hierarchical culture and fear of speaking up to superiors played into a lot of these accidents.

Keep it inside the box I suppose, same principle as keeping the nuclear stuff safe.

Sometimes you open the box. There could be 'cartridge reactors' that live in a stylish hutch and only get opened at the factory, but if this is the first one they will probably need to open it and poke around inside for some reason.

Even if it only gets opened at the factory then you have to worry about the factory.

That one is reasonably easy. You make sure that you only open the box when it's not molten. It's much easier than the nuclear part.

If the sodium is cold you will have the hardest time getting the fuel rods in and out to refuel.

If sodium solidifies, you gace ruined the reactor - its a metal solid mass in your pipes

Is there a reason why most molten salt reactors chose sodium? There's got to be a good reason to pick it given all its negatives (i.e. it burns in air, water, etc.).

Sodium has great thermal conductivity and runs at high power density.

Fast reactors need a large load of fuel (often high enrichment) to attain a critical mass. High power density helps pay for the fuel. It also means the reactor is smaller and the capital cost goes down compared to, say, a lead cooled reactor.

If you get fuel damage the most biologically dangerous fission product is iodine. The iodine reacts with the coolant to form NI salt, that salt dissolves in the sodium. Dangerous iodine isotopes decay in a few weeks. An experimental reactor melted down in the suburbs of LA in the 1950s and they never saw the iodine because it stayed put and it decayed in place.

Sodium reactors can run at high temperatures compared to water reactors. In the 1970s it was assumed that sodium reactors were attached to steam turbines and it was assumed fast reactors would cost more than thermal reactors, even though the performance of the steam turbine improves at high temperature.

Modern thinking is that a closed-cycle gas turbine is 10% the size of a steam turbine and the same for the heat exchangers so a high temperature reactor could beat the LWR for capital cost and be competitive with other power sources. A sodium reactor is a good match for a CCGT.

I can tell you know this but just to clarify, sodium and lead don't moderate the neutrons like water does (i.e. slow them down), so you can have a fast reactor, which means you can fission your U238 and transuranics instead of throwing them away as nuclear waste.

Lead does slow down sufficiently fast neutrons, by inelastic nuclear scattering. But this has a threshold (0.57 MeV); below that energy it hardly affects neutron energy at all.

You can run a water reactor with a much faster spectrum if you have more fuel and less water.

Shippingport was able to breed on the Thorium-U233 cycle.

Plutonium breeding could also be accomplished with a water reactor, possibly with two separate reactors in the fuel cycle to tune up the use of odd and even numbered isotopes. See

https://en.wikipedia.org/wiki/Supercritical_water_reactor

The trouble with it is that water has limited ability to remove heat so you are going to have a large amount of fuel tied up creating a critical mass producing relatively little water. That makes it hard to build up the fuel inventory for a fleet of breeders and economics are even worse than today's water reactors.

The source term for cesium is more important than iodine over the long term, isn't it? What does cesium do in liquid sodium?

Someone else replied with reasons for sodium, just want to mention that molten salt reactors are not sodium reactors. Sodium catches fire in water and air, salt is the stuff on your kitchen table. A molten salt reactor has nothing that could cause a chemical explosion.

The NRC has never approved a new nuclear reactor (which ended up in production). The NRC says the same about every application.

It also took two years for the NRC to provide this rejection.

Please don't excuse incompetence on an issue this important to the future.

Applicants and the NRC have to figure out what the expectations are for a new reactor application to be considered a good application. Oklo is leading the way in that process, I hope they make it through.

I remember someone lecturing about the nuclear industry mentioned that there is an inherent second mover advantage in the industry because the first mover has to figure out all the new stuff and get it approved by regulators. The second mover just follows the template and has a much easier time. If this is truly the case, then it seems like it would be hard to innovate in this space. If so, how can we remedy that?

Limit the regulations. That’s the only way.

For nuclear power. Right.

I was answering the question. What other ways can you achieve innovation without limiting regulation? If the NRC is unwilling to budge, and they hold the keys to the castle, there’s no solution.

I'm not sure why you'd be suggesting that the already captured regulators at NRC should be even more limited, unless your wish were to see some nice nuclear fireworks.

> For nuclear power. Right.

This right here is the problem.

It is actually possible to over-regulate something, no matter what it is. The more people believe something needs to be regulated, the more likely it is to be regulated disproportionate to the need. Consider the safety record of commercial nuclear power in the US.

So some coal company gets a regulation inserted that says that in order to open a new nuclear reactor, you must first push a boulder up a hill for a thousand years.

Later someone does a cost benefit analysis on that regulation, it turns out to be costing a lot while actually making safety worse, so they propose to repeal it.

Headline: Get your Pitchforks, People, They Want To Deregulate Nuclear Power

Yes:

https://rootsofprogress.org/devanney-on-the-nuclear-flop

>Excessive concern about low levels of radiation led to a regulatory standard known as ALARA: As Low As Reasonably Achievable. What defines “reasonable”? It is an ever-tightening standard. As long as the costs of nuclear plant construction and operation are in the ballpark of other modes of power, then they are reasonable.

>This might seem like a sensible approach, until you realize that it eliminates, by definition, any chance for nuclear power to be cheaper than its competition. Nuclear can‘t even innovate its way out of this predicament: under ALARA, any technology, any operational improvement, anything that reduces costs, simply gives the regulator more room and more excuse to push for more stringent safety requirements, until the cost once again rises to make nuclear just a bit more expensive than everything else. Actually, it‘s worse than that: it essentially says that if nuclear becomes cheap, then the regulators have not done their job.

US test reactors have a reputation of running very very clean and being safe places to work.

The well-established LWR has had continuous improvement both in terms of reliable performance, high uptime, and reduced occupational exposure for nuke workers.

The cost problem is not over-regulation but: (1) the LWR depends on an oversized steam turbine and heat exchangers that an order of magnitude more expensive than the gas turbines used to produce energy from fossil fuels today; they quit building coal plants in 1980 for the same reason they quit building nuclear plants, the cost of the steam turbine. Even if the heat was free the steam turbine would struggle. (2) Building an LWR is a bungle-bung bridge right out of Dr. Seuss, it's hard to find a complete reckoning but it seems anything that can go wrong will go wrong, everything from All-American Cost Disease to the factory in China that struggles to build the pump that was supposed to be cheaper to manufacture.

Even if LWR construction went 100% to plan, (1) would still make the LWR unattractive. You might be able to add pre or post combustion carbon capture to the gas turbine, compress the CO2 to 1500 psi and inject it into a saline aquifer for less.

If you want "the power to save the world" you gotta quit it with the "conservative" claptrap and take the radical step of coupling a higher temperature reactor to a closed-cycled gas turbine powerset. In the 1970s it was thought that a fast reactor had to be more expensive than an LWR but in the 2020 it is not worth moving forward unless you can do better.

I'm often at least sympathetic to anti-regulatory sentiment whether or not I'm fully onboard with it, but not here. The risk to others in operating a nuclear reactor is considerable, and anyone wishing to do so should be required to prove they understand the risks and have mitigated them to a degree acceptable to the public.

Instead, regulators may have opportunities to improve the process to make it easier for applicants to understand what they must do to receive approval. In this case, I have the impression the NRC did adequately explain what Oklo needs to improve in its application.

Slow down the approval of the second mover to match the pace of the first approval.

Calculate the total cost of the approval process. Now divide it by the number of participants and have them each pay an equal share. This means that when the fifth mover comes, they only have to pay 20% of the cost of the first mover, but they're paying it to the people who came before them, so that they're really each paying 20%.

Unformed thought: This sounds like a situation where something shaped kinda like the (or at least an improved form of the) patent system might help.

It sounds like Oklo didn't bother to try to figure out what the regulators wanted, since they didn't bother to answer the questions of regulators.

I've done some first mover approval work in biology, and yes it's more work, but all first movement is more work in every way because you're pioneering something new. The FDA, at least, is not unreasonable and is usually very open about the bar they think they need to set. You just need to talk to them, request a meeting, and show up. And also realize that it's going to be an iterative process, as any new product design process is also iterative.

Two years actually sounds incredibly reasonable for a new nuclear reactor design.

So why is anyone wasting money trying to innovate on this technology in the US?

Surely there is some other nation state that is less risk averse and open to nurturing innovation.

Oh, there is another nation. It's named China.

It's a good conjecture, Paul. One might assume that low probability events were a major issue. With a design that is first of a kind, and given that the proven inherent safety characteristics, Oklo could analyze to the most extreme events (as you know, EBR-II showed how this fuel type, with no flowing coolant, and no shutdown systems, would inherently shut itself down http://www.thesciencecouncil.com/pdfs/PlentifulEnergy.pdf).

In this case, that meant assuming that everything above ground was completely gone. The building, the secondary side (power conversion equipment etc), and all human intervention, were all assumed gone. On top of that, Oklo analyzed the simultaneous loss of one of 3 independent shutdown systems. This is obviously a much higher bar than any existing nuclear plant, and for good reason: our mission is to build a new kind of plant with these inherent safety characteristics.

There might be a reason why there wasn't a lot of detail on sodium fires - there is no pool of sodium. The heat pipes use potassium. :) Oklo did tests on what happens in air, if sodium heat pipes were fully breached with huge holes and interacted directly with air. I was there. We just straight up had incredible amounts of energy hitting the heat pipe from myriad solar mirrors. It was pretty fun to test advanced fission with solar thermal. Anyway, there was a little bit of smoke, and actually the heat pipes kept functioning far longer than even the heat pipe expert expected, because the reacted sodium kept self-cauterizing the hole. In this reactor's case, the heat pipes would be in an inert environment, but it was interesting to see what would happen if somehow it were just pulverized in an open outdoor field.

There are roughly 40 external events that had to be analyzed: earthquakes, wind, tornadoes, seiche, avalanches, landslides, wildfires, you get the idea. What happens in our methods was that the worst possible event was analyzed. We took seismic accelerations worse than ever recorded in the history of the entire united states. It turns out, with a thorough risk analysis (based on risk analysis standards set up in the history of EBR-II and PRISM and others), that assuming you lose literally everything above ground is about the most conservative thing that is within the realm of happening once every million years. Keep in mind we were just seeking a 20 year license for a plant smaller than the MIT research reactor, but low-enriched.

But the end result is as you say, we have learned, they've learned, and we resubmit. We believe deeply that if fission is going to make a difference a commercial plant has to be built before the end of the decade! Happy to answer any questions.

Low-probability is not enough to wave away concerns when it comes to planning nuclear power

Yes, but focusing on the astronomically low probability scenarios while failing to discuss much higher probability scenarios is a bad look.

Is it? Those astronomically low-probability scenarios have a track record of creating real-world catastrophes.

Fukushima was a power failure. Sure, am improbable disaster caused the power failure, but the issue was still a power failure. They should haven’t been able to handle it and couldn’t.

The power failure is not "low probability", it is the dominant failure mode that happens somewhere around 1 in 1000 to 1 in 10,000 reactor years.

Reactors were licensed in the 1970s based on an entirely wrong model which saw the dominant failure mode being the pressure vessel bursting. Laymen have a totally wrong point of view about that, they think a pressure cooker really has the metal burst and go off like a bomb, really the seal breaks and you get sprayed with superheated steam which is dangerous enough. Pressure vessels burst because the chemicals eat them from the inside out but for every pressure vessel that bursts thousands of storage tanks get sucked in.

After TMI the model was updated to recognize "station blackout" as the #1 risk.

Fukushima currently has a body count of 1 and the city is perfectly habitable.

It was also basically the worst case scenario that could happen to that reactor design.

The tsunami and the earthquake killed 20000 for a scale.

Sure, I think that's true, but it was an event of such magnitude that there's a clear state interest in regulating against it! They had to evacuate a huge area around the disaster, for some time. Sure, it was a best-case scenario, but it was the best case of a worst case.

(I support nuclear power, for whatever that's worth. I think it's a good idea and we should do a lot more of it.)

Only because the high probably scenarios are handled safely...

This is pretty straightforward survivorship bias, i.e., you don't hear about the astronomically low-probability scenarios which don't result in real-world catastrophes (consider every building, bridge, etc which hasn't collapsed).

We have to balance that against the millions of annual fossil fuel deaths (tens of thousands die each year just in the US and just due to coal pollution https://www.scientificamerican.com/article/the-other-reason-...) and the cliff toward which climate science tells us we're careening.

Survivorship bias may explain why these events are so vivid in people's minds, but when the bar is that _there should be no survivors at all_ (i.e. no catastrophes), the fact that there _are_ survivors with which to form a bias is in and of itself a concern.

It’s a concern which must be weighed against the alternative. In the case of nuclear vs fossil fuels, it’s millions of annual deaths in the near term (air pollution) and much more with climate change.

Natural disasters are not astronomically low probability scenarios, they happen all the time. Astronomically low probability would be something that is unlikely to happen during the entire lifetime of the planet.

No, but an avalanche in a flat area is a lot less likely than, say, "what if the coolant runs out" and it seems they were missing some basic handling of these sorts of scenarios while still waxing poetic about things like avalanche contingency plans.

What? Depends how low the probability is and the magnitude of the worst case we're talking about.

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