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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

#111

Post by politician »

xorbax wrote: post #97
el_nahual wrote: post #73

Earlier quoted context omitted.

Part of it is molten (above the plug), part of it is frozen (the plug). Think pipes in a house in winter, where one little part of the pipe gets frozen while the rest of the pipes have liquid water in them.

And in Spring, when the broken pipe plugged with solid molten ice thaws, your house's molten ice circuit performs an emergency evacuation into the yard, saving you from the convenience of adequate molten ice pressure

Hah! Well, we usually think of salt in the solid state (i.e. frozen) and not in the liquid state, so it's not so strange to be explicit in this case. For H2O, we do have pretty common encounters with three of its phase states, so there's less need to be explicit (or, rather, we have separate words for each state: steam, water, ice).

Re: Application submitted for US molten salt research reactor

#112

Post by runarberg »

EricE wrote: post #28

Way, way overdue! China has taken all of our research from the 50's and has been charging ahead. Very sad that politics and ignorance has severely kneecapped our nuclear industry :(

Why does that matter?

Particle physics dominated US research grants for several decades with some results to show for it. Now that the focus has shifted elsewhere (e.g. material science) and another country is leading in nuclear research, we will be able to observe their results and act accordingly (just like China did in the 50s). Why is it so important which government is facilitating which research?

Re: Application submitted for US molten salt research reactor

#113

Post by andy_ppp »

ortusdux wrote: post #53
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…

You are correct about the corrosion issue. I've done some work developing molten salt resistant claddings. The main culprit is chromium leaching, which de-alloys most of the metals approved for reactor design. The leeching happens at the grain boundaries, so you will hear 'intergranular attack' as a research focus. A close second problem is the radiation itself. Elements in both the containment vessel and salt transm…

What about using molten lead or something that can act like a lubricant/insulation at that temperature away from the corrosion in the same way airflow is used over jet turbine blades to stop them melting? It there any high temperature liquid that is molten salt phobic like oil and water?

Re: Application submitted for US molten salt research reactor

#114

Post by HPsquared »

mulmen wrote: post #105
HPsquared wrote: post #65

Earlier quoted context omitted.

If it's designed with replacement in mind, a graphite moderator isn't all that bad. It can even be a safety advantage, in that if you drain the fuel out of the vessel it's taken away from its moderator.

I must not be parsing this correctly. Taking fuel away from the moderator sounds like a safety disadvantage. Maybe I don't know what a moderator does.

If the fuel is designed such that it needs a graphite moderator to sustain a reaction, then if the fuel is removed from the reactor it's less likely to go critical than if the fuel was "higher-grade". It's less likely to have a criticality accident.

Re: Application submitted for US molten salt research reactor

#115

Post by runarberg »

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…

> There is fear that any advance in nuclear power technology will lead to corresponding advances in nuclear weapons technology.

It seems like it would be a good idea to get the United Nations’ Treaty on the Prohibition of Nuclear Weapons (https://www.un.org/disarmament/wmd/nuclear/tpnw/) signed by more nations then, so that this technology could be safely developed without a risk of nations weaponizing it.

Re: Application submitted for US molten salt research reactor

#116

Post by dragonshed »

thoughtpeddler wrote: post #64

Forgive me if this is a naive question, but how are molten salt reactors different from the reactor in the 1959 Sodium Reactor Experiment [1]? [1] https://www.etec.energy.gov/Operations/Major_Operations/SRE....

[Layman, but I've read up quite a bit on thorium and molten salt reactor designs]

The 1959 Sodium Reactor experiment was to demonstrate the feasibility of a sodium-cooled reactor as the heat source for a commercial power reactor to produce electricity. It used fuel rods similar to rods used in reactors in operation today.

Conversely the The Molten Salt Reactor experiment[1] used uranium fuel dissolved into a salt as both fuel and coolant for the reactor - this design enables significant advantages over traditional reactors powered by solid fuel.

[1] https://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment

Re: Application submitted for US molten salt research reactor

#117

Post by chris_wot »

ortusdux wrote: post #107
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?

It doesn't, but any material used needs to withstand 4 extremes - high temperatures (650-850 C), corrosion (dissolves uranium), very high neutron flux, and US govt. regulation. Graphite is the current favorite non-metal option. It is already widely used in traditional reactors, so it is approved, and its interaction with radiation is well understood. On the other hand, its interaction with radiation and molten salt i…

Ah yes, the most extreme thing one withstands is U.S. regulation.

Re: Application submitted for US molten salt research reactor

#118

Post by werdnapk »

mulmen wrote: post #104
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…

Glass is already basically welded, or maybe it's more like brazing. But an oxyacetylene torch can be used to work with glass just as well as to cut or weld metal. Metals also have weird properties. Like tempering and hardening based on temperature. In an industrial setting you need expert welders with deep knowledge of the materials or a weld is going to fail and ruin your day. So it doesn't seem like a huge leap to…

Doesn't glass.... melt?

Re: Application submitted for US molten salt research reactor

#119

Post by throwaway894345 »

politician wrote: post #109
throwaway894345 wrote: post #29

Earlier quoted context omitted.

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 wrote it that way to aid the reader in understanding what the plug material was composed of. I didn't want the reader to think that the material was water ice. Yes, the material is the frozen state of the once liquid reactor fluid. I hope that clears it up, and would welcome a better way of explaining it!

Yes, that makes a lot of sense. I wasn't trying to nit-pick your phrasing, I was just curious if I was misunderstanding something as a lay person. :)

Re: Application submitted for US molten salt research reactor

#120

Post by usrusr »

elihu wrote: post #98
lolc wrote: post #93

Earlier quoted context omitted.

Nice hack! That sounds so easy that I wonder what the catch is. Maybe it would need more energy for cooling than what it generates? So it would have to be scaled up to a size where the surface-to-content ratio becomes favourable. There might not be enough salt for that :-)

I suppose one problem might be selecting an appropriate coolant that doesn't dissolve the salt on contact. Presumably water would, but google says that salt doesn't dissolve in oil so maybe that's an option. Ideally you wouldn't need to expend energy to keep the coolant cold enough; rather, you'd use the coolant to boil water to run your steam generator.

“Vessel built out of nothing but heat transfer interface and freeze plug". Do some of the materials problems get easier while it's only touching the salt in frozen state?
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