Application submitted for US molten salt research reactor • Hacker News Board

Re: Application submitted for US molten salt research reactor

#81

Post by kenned3 » Mon, Aug 22, 2022, 9:06 PM UTC

ars wrote: post #41

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…

> slightly radioactive steam For anyone worried about this, the longest lived unstable isotope of oxygen (that is heavier than stable oxygen) has a half life of 26 seconds. Hydrogen can become deuterium which is stable, and finally tritium which is not. Tritium has a long half life of 12 years, but is low energy and very easily shielded (just don't eat it). There is very very little tritium - first you'd have to make…

Your view really depends on the design.

CANDU (Canadian reactor design) is moderated via deuterium in which case there is a LOT of it circulating in the reactor core.

The heavy water is syphoned off to a tritium separation unit for recovery. With a market value of $30,000 a gram, there is a clear incentive to recover it ;)

Re: Application submitted for US molten salt research reactor

#82

Post by andrewflnr » Mon, Aug 22, 2022, 9:07 PM UTC

throwaway894345 wrote: post #29

politician wrote: post #27

Earlier quoted context omitted.

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?

I think it was just a clumsy phrasing, with the point being that it's a solid plug of whatever salt is molten and circulating above.

Re: Application submitted for US molten salt research reactor

#83

Post by systemvoltage » Mon, Aug 22, 2022, 9:11 PM UTC

kenned3 wrote: post #78

HPsquared wrote: post #68

Earlier quoted context omitted.

Does it even need to be a metal? (Since the pressure is so low strength requirements are lower)... How about ceramic or glass (or quartz), or something else non-metal?

non-metals have their own problems and glass tends to have some really weird properties. I would think a major one would be their failure mode. Metals flex and expand before they eventually fail. Glass/ceramic is fine until suddenly it isn't and has a total failure. Think of a window being hit. If it were metal it would probably deform but if it is glass it shatters. Next would be joining them on-site. If needed, met…

Composites? Such as the stuff used in Aviation?

Re: Application submitted for US molten salt research reactor

#84

Post by hedora » Mon, Aug 22, 2022, 9:21 PM UTC

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…

It's pretty cool that they designed their plants with a heat reservoir and oversized turbine generators. This allows them to turn the turbines on and off at will, complementing wind and solar. The nuclear plant "charges" the heat reservoir during the day when the turbines are idle.

Re: Application submitted for US molten salt research reactor

#85

Post by runarberg » Mon, Aug 22, 2022, 9:21 PM UTC

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…

> But I was under the impression that the main stumbling block for molten salt reactors was that high-energy corrosion resistant materials for containing / moving molten salt simply don't exist (yet).

Is this also an issue for molten salt / liquid metal batteries[1][2] that have been proposed as a grid scale energy storage solution for renewables?

The way I understand it, molten salt is used as the membrane separating the electrode and electrolyte layers. But I was under the impression that there are actual molten salt batteries prototypes with industrial scale facilities currently under construction.

Are the requirements to contain the molten salt in a battery different from a nuclear reactors? Or do they have the same challenges and are simply able to overcome economic feasibility whereas nuclear reactors aren’t?

1: https://ambri.com/

2: https://www.youtube.com/watch?v=-PL32ea0MqM

Re: Application submitted for US molten salt research reactor

#86

Post by aidenn0 » Mon, Aug 22, 2022, 9:30 PM UTC

PaulHoule wrote: post #36

nine_k wrote: post #21

Earlier quoted context omitted.

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 ea…

(1) There is fear that any advance in nuclear power technology will lead to corresponding advances in nuclear weapons technology. For instance, if somebody built a perfect system for separating out protactinium from a thorium MSR, that protactinium could be allowed to decay outside the reactor and produce pure U233 that could be used to make weapons. That perfect system is probably not practical, but in general there…

I can't find a source, but my recollection is that the majority of the U-235 for Little Boy was generated by gaseous diffusion? I know the original process was gaseous-diffusion followed by Calutron and that once gaseous diffusion was improved they shut down all of the Calutrons, and the timing is such that all but the first little boy bomb must have been made by gaseous diffusion, but it's unclear how the fissile material for the bomb dropped on Hiroshima was generated.

Re: Application submitted for US molten salt research reactor

#87

Post by elihu » Mon, Aug 22, 2022, 9:31 PM UTC

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…

It seems like that might suggest a potential option in the search for appropriate materials to build the containment vessel and piping to hold in the salt: just make the whole thing out of salt. Anything that needs to be solid can have built-in channels with coolant piped through. The rest can maintain a sort of steady state.

I'm sure there's all sorts of practical reasons why that wouldn't work, but it's an interesting thing to think about.

Re: Application submitted for US molten salt research reactor

#88

Post by [deleted] » Mon, Aug 22, 2022, 9:48 PM UTC

Turbots wrote: post #79

kenned3 wrote: post #78

Earlier quoted context omitted.

non-metals have their own problems and glass tends to have some really weird properties. I would think a major one would be their failure mode. Metals flex and expand before they eventually fail. Glass/ceramic is fine until suddenly it isn't and has a total failure. Think of a window being hit. If it were metal it would probably deform but if it is glass it shatters. Next would be joining them on-site. If needed, met…

what about glass pipes encased in said metals :-)

[deleted]

Re: Application submitted for US molten salt research reactor

#89

Post by nullc » Mon, Aug 22, 2022, 9:52 PM UTC

throwaway894345 wrote: post #72

PaulHoule wrote: post #9

Earlier quoted context omitted.

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…

> We can produce heat for hydrogen, replacing the need for fossil fuels in heating, transport and industry. What does it mean to produce "heat for hydrogen"? Why is heating hydrogen a useful property (how does hot hydrogen replace fossil fuels in heating, transport, and industry?)? That seems oddly specific, so I assume I'm misreading something?

Thermochemical water cracking.

Re: Application submitted for US molten salt research reactor

#90

Post by [deleted] » Mon, Aug 22, 2022, 9:52 PM UTC

systemvoltage wrote: post #83

kenned3 wrote: post #78

Earlier quoted context omitted.

non-metals have their own problems and glass tends to have some really weird properties. I would think a major one would be their failure mode. Metals flex and expand before they eventually fail. Glass/ceramic is fine until suddenly it isn't and has a total failure. Think of a window being hit. If it were metal it would probably deform but if it is glass it shatters. Next would be joining them on-site. If needed, met…

Composites? Such as the stuff used in Aviation?

[deleted]