Natrium 'advanced nuclear' power plant wins Wyoming permit

You are assuming that as the core starts to expand, it doesn't expand in a way that increases k (for example, suppose liquid sodium is violently expelled from collapsing coolant channels; this could increase k). Can this be assured? Because if not, the yield could become very large. Granted, this doesn't seem likely, but can you assure it's impossible, in any possible accident, and any possible geometry of fuel and voids?

> What you are saying is a Catch-22. NRC can't approve a new design because it doesn't know how it performs under accident conditions, but then you can't know how something performs under accident conditions if you don't build it, and you don't build it if NRC does not approve it.

Even if you build it, and even if there is an accident, you don't know how it behaves under accident conditions. You just know how it behaved in that particular accident.

It might be easier for developers if we could build thousands a fast reactors and let some of them explode to get some statistics on what works, but that's not how the NRC is arranged, and even that would not ensure all the catastrophic risk had been retired.

I suppose that "passive natural circulation cooling" means that plain convection of the coolant(s) is sufficient to cool the reactor, without involving pumps which could fail. Convection can't fail as long as there is coolant and no significant obstacles.

Russia has been operating a sodium-cooled fast reactor for 45 years.

Fast reactors do have some attractive features. They have better neutron economy and work better with plutonium. They can achieve breeding ratios comfortably above 1 with the U-Pu system. They produce less actinide waste since the chance of neutron capture not causing fission is lower, and can more effectively destroy actinide waste. Sodium-cooled fast reactors will operate at higher temperature than LWRs, enabling the salt thermal storage scheme they propose to use.

In large reactors, these features have not been enough to compensate for the disadvantages and sodium-cooled reactors have not been successful, coming in more expensive than light water reactors for a given power output. France, which had been developing fast reactors, has recently mothballed the effort with no plan to restart before 2050.

The main advantages of using a fast reactor are less nuclear waste and more energy for a given fuel input.

It can make more fuel than it uses. It needs enriched uranium at startup but then can convert regular uranium and/or thorium to usable fuel.

How do you do that in a way that's amenable to conclusive analytic demonstration? For example, how do you prevent melted fuel from flowing into the cooling channels that go through the core?

About the only approach I'd be comfortable with would be dissolving the fuel in molten salt (probably chloride salt). This is not Natrium's approach.

Melting of fuel is not a theoretical problem -- it has actually happened at two fast reactors in the US (EBR-1 and Fermi-1, the latter the reactor in the hyperbolically titled book "We Almost Lost Detroit"). No explosions occurred, but it's very troubling the fuel melted at all. The NRC will surely insist on analysis of the consequences of partial fuel melting accidents.

Okay, we had a partial meltdown in prod, and released some radioactive iodine-131, so that goes on the sad face side of of the retro board.

But on the good side, we _didn't_ have a hydrogen explosion due to some late-night troubleshooting, great work Carl!

But we learned a lot, our alerts were confusing, and our metrics didn't surface coolant level or the relief valve that was stuck open.

So next sprint, let's focus on monitoring and cross-team knowledge transfer! 3 points, right?

While true, this has nearly nothing to do with building (still to happen) or planning (has to be finished before the approval process). It is a 2 year paperwork delay and making sure the NIMBYs have all the time they might need to get organised.

The reason nuclear isn't price competitive with renewables—or anything, really—is because of the amount of safety regulation and lack of experience building plants. Both of these emerged, at least in part, from decades of protests from well-meaning people with a laughable misunderstanding of how radiation works. So, you get people saying "don't build nuclear, it's unsafe!" and then you demonstrate that it's as safe as any energy technology in existence, so those people say "okay fine... don't build nuclear, it's expensive!" when they are the reason it's expensive. Meanwhile, we managed to create an irreparable 1.3C rise in global temperatures while waiting for solar, wind, and battery to catch up to where we could have been 70 years ago.

Once they’ve approved this reactor, build more of the same.

Last I checked solar without batteries is roughly the same price per Kw as nuclear. There’s a huge difference in capability though because nuclear is 24/7 peak availability which solar can’t do and if you start building batteries the price increases substantially.

I agree on regulatory experience but that comes more from panic over nuclear proliferation rather than any economic reason. Whether or not you view that as a legitimate concern is open to debate.

Indeed so. Renewables had about 15 years of breakneck-pace progress and massive production with huge economies of scale, which I cannot say about nuclear reactors.

But even if nukes were somehow very cheap to build, the review process due to high safety requirements and a lack of a standardized reusable reactor design would make the process slow. To become cost-competitive, nuclear reactors need to be mass-produced, using a proven design that needs little review. The French sort of achieved that, with two mass-produced types of reactors.

Renewables as baseload are still problematic though. Solar cells and even wind turbines are not expensive, but the batteries are very expensive, and are a huge fire hazard. It would be interesting to estimate how much would a kWh cost from a nuclear power station, and from an equal-power LiFePO4 battery installation with the capacity of, say, 3 days worth of the rated max power. Batteries can be replaced gradually, but would need to be replaced much sooner.

[Update:]

If we take a modest nuclear generation unit producing 300 MW of electric power, I'd like to compare it with a battery that can store 300 MW * 3 days of energy from renewable sources. It's 21.6 GWh. With LiFePO4 typical bulk price of $100 per kWh, the upfront cost in batteries alone would be $2.16 billion. It's still lower than nuclear reactor equipment, but very much in the same ballpark.

Yeah, the breeder reactions are good because they can burn long lasting isotopes, generating short half life and more easily disposable materials, but they also make more of the risky isotopes (those with low critical mass that are more easily/chemically separable). Thorium is quite a bit better about that (not perfect), but it's even less well understood for actual reactor design and production.

Not in the US.

Thanks. It looks like it meant to be short-term but nonetheless.

Low pressure, but you sure don't want air in there