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Application submitted for US molten salt research reactor

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Re: Application submitted for US molten salt research reactor

#21

Post by nine_k »

PaulHoule wrote: post #9
marcosdumay wrote: post #2

A 1MW research reactor. Anyway, why is it always a fluoride salt? Is it because of the melting point or because of some nuclear property? I imagine there is some very relevant reason, because a less reactive anion (even chlorine) would be much easier to work with.

Fluoride salts are good for fissile uranium + fertile thorium. If you want to work with a plutonium/uranium 238 cycle then chloride salts are a better choice. Plutonium doesn't dissolve very well in fluorides. Molten chloride reactors can have performance characteristics right out of science fiction, it seems possible for such a reactor to not only breed more fuel but to destroy the long-lived (500 year) fission prod…

While at it, I never understood the worry about the plutonium surfacing in the MSR cycle. Of course it can be diverted to make nuclear warheads. But countries like the US, or France, or Russia, or China, or India already are able to produce nuclear warheads, even from plutonium extracted from more conventional reactors. I don't understand where is the risk of proliferation.

Is this about international treaties and ease of inspection? About currently non-nuclear countries obtaining nuclear weapons more easily?

Re: Application submitted for US molten salt research reactor

#22

Post by tadfisher »

sophacles wrote: post #15
dangerlibrary wrote: post #12

So, in a conventional reactor, you use nuclear fission to heat/pressurize water and then use your hot, slightly radioactive steam turn a turbine. This mostly works because moving even very hot, very high pressure water around is kind of a solved problem in industry. In a molten salt reactor, you use nuclear fission to melt various corrosive salts into a fluid, and this is good because molten salts store a lot more en…

> So, in a conventional reactor, you use nuclear fission to heat/pressurize water and then use your hot, slightly radioactive steam turn a turbine. I was under the impression that there was a heat exchanger in the path - that is the reactor turns water into slightly radioacive steam, which is sent through a heat exchanger to turn different water into non (or way less anyway)- radioactive steam for the turbines. So bo…

Correct, in a PWR or BWR the hot side is in a closed loop. There's a great PDF here: https://www.nrc.gov/reading-rm/basic-ref/students/for-educat...

Re: Application submitted for US molten salt research reactor

#23

Post by indymike »

This is really exciting. Fission tech is largely stuck in with incremental improvements from the 1950s. The last time the NRC got an application for a research reactor was 30 years ago.

The reactor is a graphite-moderated, fluoride salt flowing fluid design. If this works well, fission will have a very bright future as it should be more efficient and much safer to operate than current reactor designs.

Re: Application submitted for US molten salt research reactor

#24

Post by PaulHoule »

dangerlibrary wrote: post #12

So, in a conventional reactor, you use nuclear fission to heat/pressurize water and then use your hot, slightly radioactive steam turn a turbine. This mostly works because moving even very hot, very high pressure water around is kind of a solved problem in industry. In a molten salt reactor, you use nuclear fission to melt various corrosive salts into a fluid, and this is good because molten salts store a lot more en…

People thought this stuff

https://haynesintl.com/docs/default-source/pdfs/new-alloy-br...

(which is practically stainless steel without the steel) was good for this use but when it was tried in this system it did not hold up very well

https://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment...

but it was believed that some small change in the formula such as adding Niobium could clear the problem up. What's needed to move forward is not a big conceptual breakthrough but rather testing of materials under realistic conditions... A new test reactor.

What is more problematic with the MSRE design is that it incorporates graphite as a moderator and the graphite swells and goes bad over time. Possibly you can take the graphite core out every few years and replace it with a new one, but people have also found designs that don't require a moderator outside the fuel salt.

When I went to the first conference on Thorium Energy years ago David Leblanc had done some very simple calculations that showed you didn't need the graphite -- it works just fine with a faster spectrum. He's refined that idea and is running with it. Others are pursuing chloride salts and plutonium fuel with a very fast spectrum.

Re: Application submitted for US molten salt research reactor

#26

Post by nine_k »

Kalium wrote: post #8
AtlasBarfed wrote: post #5

I thought these were outlawed, per a LFTR video I saw once. To emphasize, I'm asking if that is the case, or was the LFTR video was engaging in misinformation, or if something changed in regulations.

I believe it's less outlawed and more not really approved for use due to insufficient research.

AFAICT materials research is a big part of it. At 800°C even water is pretty reactive; the salt is much more so. Even though an MSR does not need the high pressure of water-based reactors, you can't make all the piping from graphite or platinum.

Re: Application submitted for US molten salt research reactor

#27

Post by politician »

ortusdux wrote: post #18
dangerlibrary wrote: post #12

So, in a conventional reactor, you use nuclear fission to heat/pressurize water and then use your hot, slightly radioactive steam turn a turbine. This mostly works because moving even very hot, very high pressure water around is kind of a solved problem in industry. In a molten salt reactor, you use nuclear fission to melt various corrosive salts into a fluid, and this is good because molten salts store a lot more en…

Annoyingly, "molten salt reactor" is used to describe two different technologies. What you describe is a traditional reactor that uses molten salt to move heat. This typically leads to higher efficiencies, but does have corrosion issues. Other power generation systems can also benefit from molten salt loops - namely solar energy collectors. In the research field, "molten salt reactors" (MSRs) usually means the other…

One of those safety improvements -- a freeze plug -- passively halts the reaction in the event of a power cut. The reactor sits on top of a vault that has a larger volume separated by a narrow tube containing molten salt that has been frozen into a plug by cryocoolers powered by the turbines themselves. If the pumps stop for any reason, then the plug quickly melts and the molten fluid from the reactor drains into the larger vault via gravity at which point it cools and freezes into a solid.

Re: Application submitted for US molten salt research reactor

#29

Post by throwaway894345 »

politician wrote: post #27
ortusdux wrote: post #18

Earlier quoted context omitted.

Annoyingly, "molten salt reactor" is used to describe two different technologies. What you describe is a traditional reactor that uses molten salt to move heat. This typically leads to higher efficiencies, but does have corrosion issues. Other power generation systems can also benefit from molten salt loops - namely solar energy collectors. In the research field, "molten salt reactors" (MSRs) usually means the other…

One of those safety improvements -- a freeze plug -- passively halts the reaction in the event of a power cut. The reactor sits on top of a vault that has a larger volume separated by a narrow tube containing molten salt that has been frozen into a plug by cryocoolers powered by the turbines themselves. If the pumps stop for any reason, then the plug quickly melts and the molten fluid from the reactor drains into the…

Freeze plugs sound super cool, but this part breaks my brain:

> containing molten salt that has been frozen into a plug

Presumably salt can't be both molten and frozen at once, or is there something about this domain that I don't understand?

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