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Comment by jonplackett | Hacker News Reader

I think I read recently that this was a US idea that was abandoned that China took up and made it work. Is that accurate?

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The US had a similar but not identical reactor in the 60s, the Molten-Salt Reactor Experiment https://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment

It had uranium-233 from breeding from thorium in other reactors.

The main problem with these things is they seem very unprofitable. The US reactor ran from 1964 to 1969 and produced a small amount of power but is still running about $10m a year in decommissioning costs. You thing you can run these things a while and think it's over but:

>Sampling in 1994 revealed concentrations of uranium that created a potential for a nuclear criticality accident, as well as a potentially dangerous build-up of fluorine gas: the environment above the solidified salt was approximately one atmosphere of fluorine. The ensuing decontamination and decommissioning project was called "the most technically challenging"...

No country has seriously invested in the thorium fuel cycle because it cannot be used to create weapons. Unfortunately, the technology also began to look most promising as an energy source around the same time the Three Mile Island nuclear accident effectively ended all interest in nuclear energy in the United States.

India has shown some of the most interest to date, due to their lack of domestic uranium reserves. But it's been slow going their fast breeder reactor plans were delayed by like two decades. But it is built and it was loaded with fuel last month [0]

The French interest in breeder reactors and nuclear reprocessing also originates from a similar concern about lack of domestic access to raw uranium. Though Super-phoenix [0] was a more traditional uranium -> plutonium approach and not thorium. They gave up because just using uranium is way, way cheaper than synthesizing your own fissile materials.

[0] https://www.world-nuclear-news.org/articles/indias-prototype...

[1] https://en.wikipedia.org/wiki/Superph%C3%A9nix

Also, it’s only energy positive under some specific carefully managed conditions, and is a real pain to make work.

If you have easy access to uranium, you just use it directly instead.

Depends on what you want out of your reactor. You want to make a synthetic fuel, Thorium not Uranium. You want a liquid fueled reactor (because its safer and proliferation resistant), Thorium not Uranium. You want 900C heat instead of 300C heat, Thorium not Uranium.

The fuel costs of a NPP are a tiny rounding error. If you want electricity and want to build it today, Uranium not Thorium. You are using arguments from 50 years ago when many incorrect assumptions about cost structure and fuel availability were used to make decisions.

The cope is strong here. The only liquid fueled reactors with any operational experience got shut down because of corrosion issues causing major leaks.

The pros you mention are theoretical - because the cons came out in force when actually tried, and they’ve been tried many times by many different countries.

Thorium can be used to make weapons via the breeding cycle. It's much less convenient and straightforward than uranium/plutonium, but it is possible.

Theoretically, perhaps, but I don’t think anyone with a serious interest in weapons would pursue it. From a nonproliferation perspective, I’d guess the infrastructure necessary to remove contaminants from uranium bred through the thorium cycle would be costly and difficult to conceal.

Multiple countries have detonated nuclear bombs using U-233 derived from thorium reactors! [0] Practically I agree with you that thorium is proliferation resistant and if someone is bomb hungry they won't prioritize it, but if you want to set up the bomb and all you have is thorium... The infrastructure wouldn't necessarily be significantly larger or worse than conventional enrichment.

0 - https://en.wikipedia.org/wiki/Uranium-233

Seems presence of U-232 is more manageable than I thought.

You can absolutely make nuclear weapons with U233.

Technically true and practically false. Only once has anyone done that. The bomb was considered a dud and the research was ultimately destroyed. So while you could, it would require completely reinventing all the original research that went into making the original one. Lookup operation teapot for more details.

Weapons are irrelevant for power generation. No modern classic pwr was used to create weapons- because it's cheaper to have dedicated infra

Yes: https://en.wikipedia.org/wiki/Thorium-based_nuclear_power#Hi...

Well, fible energy is trying to do lots. Gates invested in MSTR (molten salt thorium reactor).

But regulation, while it has its purposes, stifles many things. At the same time time it’s not even doing what they were meant for.

There are a number of countries being run far better than the US or the EU

> There are a number of countries being run far better than the US or the EU

It will be funny if China is what convinces the US to be more open to free industry. Opposite day vs the 1970s

To be fair, these advances are not being made in China due to "free industry". They have something of a command economy for their critical sectors. So it's unfair not to point out that it's easy to make advances if a nation as a whole points to a hill and says, "take that hill". Of course you can do it under those circumstances.

If it's just your company or some trifling consortium trying to develop nuclear energy advances in a "free industry" environment, the guy who is just slapping up windmills, [T Boone Pickens RIP], is just gonna mop the floor with you. There's just no way to compete on moonshots like that.

China has many capital controls but generally supports industrial activity in the state interest; the US does the opposite.

Gates invested in the traveling wave reactor which was a bust. Then he sold his entire investment in nuclear several years ago. He's very rich so perhaps he has other nuclear investments that I'm not aware of but none are in the MSTR space unless they are secret/private.

> none are in the MSTR space unless they are secret/private

TerraPower is not secret.

Historical experiments with alternative fuel cycles, not serious development attempts. A serious development attempt happened in India though.

Yeah, the US had an experimental Molten Salt Reactor in the 60s

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