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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

#141

Post by jabl »

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

Water is actually a very unusual substance in that it expands upon freezing. (Plutonium being another)

Most materials instead contract when freezing.

Re: Application submitted for US molten salt research reactor

#142

Post by jabl »

pfdietz wrote: post #71
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…

There are a number of obstacles. Neutron damage to the reactor structure is more of a problem, since the fuel is dissolved in salt in direct contact with that structure (unlike a reactor with solid fuel rods, which are separated from the reactor vessel by a thickness of moderator, in the case of LWRs is water.) See here for a (somewhat old) list of some technical issues: https://gain.inl.gov/SiteAssets/MoltenSaltReac…

> "Over 40% of [fission products] leave core [in offgas]" "Large fraction of cesium, strontium, and iodine end up in offgas"

That could, in theory at least, be an advantage if you have a good process for capturing and storing that offgas (reacting it with something to make it solid and then glassifying it, for instance).

In a traditional fission reactor, gaseous fission products cause swelling and cracking of fuel pellets, and builds up pressure in the fuel tubes, which is one of the factors limiting fuel burnup.

Re: Application submitted for US molten salt research reactor

#143

Post by jabl »

AtlasBarfed wrote: post #135
PaulHoule wrote: post #60

Earlier quoted context omitted.

As much as people portrayed an epic battle between renewables and nuclear the real winner from the move away from nuclear was natural gas fired gas turbines. The most obnoxious thing about the energy literature is that it frequently reads like a stopped clock. People still compare the cost of nuclear energy to the cost of coal, but it's no accident that the US stopped building coal plants at the same time it stopped…

Do the gas turbines use the brayton cycle? As I understand gas turbines are around 64% efficient with various tricks. I recall a LFTR presentation talking about how they could use the Brayton cycle because of... ?high temps I think?. Is the closed cycle gas turbine also using a superior cycle like the Brayton? Oh it's in the third sentence, CTRL-F failed me.

> As I understand gas turbines are around 64% efficient with various tricks.

These super-high efficiency gas turbines are not 'pure' gas turbines, but so-called combined cycle plants. Basically you first have a 'normal' gas turbine driving a generator (which, by itself, maybe gives you ~45% efficiency), but then you take the host exhaust of that gas turbine and use that to drive a secondary steam cycle driving another generator.

I'm not sure such a thing is doable in a closed Brayton cycle, at least I haven't read anything about anything like that.

An interesting thing with closed cycle Brayton is that instead of air you can use another fluid as the working fluid. Supercritical CO2, for instance, has some nice properties leading to extremely compact machinery. Of course there's an uphill battle in commercializing this technology; if you use air (or nitrogen) you can just adapt one of the many existing gas turbine cores with $zillions of R&D and decades of experience behind them.

Re: Application submitted for US molten salt research reactor

#144

Post by jabl »

powerhour wrote: post #123
phonon wrote: post #100

Earlier quoted context omitted.

Westinghouse went bankrupt a few years ago[0]...and GE hasn't been doing well and is splitting up[1]... [0] https://www.nytimes.com/2017/03/29/business/westinghouse-tos... [1] https://www.usnews.com/news/business/articles/2022-07-18/ge-...

I'm out of date, lol. Well, GE, even post-breakup, has a huge energy business that would benefit from increasing nuclear production. Assuming they really can make safe, cost-effective power, anyway.

GE is one of the big names in gas turbines, and AFAIK they make wind turbines as well, in addition to nuclear power plants. So whatever the customer wants they can offer. ;)

Re: Application submitted for US molten salt research reactor

#145

Post by hanniabu »

powerhour wrote: post #44
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 :(

It's also sad that industry completely failed to convince the population that they can provide a safe solution. For all the credit we give BigCo for creating propaganda, it's curious that they were unable to be successful here, given the stakes.

Safety isn't a technical problem, it's a human problem. Over long periods safety measures end up being cut and introduce risk. There's also design decisions revolved around cost even though better solutions exist. Then there's just plain oversights. For example we all know earthquakes and tsunamis exist and yet the Fukushima still happened.

Re: Application submitted for US molten salt research reactor

#146

Post by jabl »

runarberg wrote: post #112
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?

> Why is it so important which government is facilitating which research?

For better or worse, the world doesn't work such that everyone who reads a research paper is on an equal footing to industrialize/commercialize the technology. The ones who got their hands dirty are far ahead. Thus governments do something called 'industrial policy' (a somewhat dirty word in the West these days, to our detriment I think) where they try to build 'value chains' (or whatever you wanna call it) where they spend money on pure research, applied research, early stage spinoffs, etc. to kickstart an industry around a particular technology.

For an example, consider how decades-long investment by the US government into electronic warfare and military electronics kickstarted Silicon Valley.

So China is gearing up to be a dominant player in the global nuclear power market. So does that matter? In a way it's better somebody does it than nobody and we continue burning fossils, but being one of these hopeless romantics who think things like democracy and human rights are incredibly important I'd rather see 'our team' on the field as well. Energy extortion isn't pretty, see Europe and Russia at the moment.

Re: Application submitted for US molten salt research reactor

#147

Post by Rokid »

mikewarot wrote: post #61

I'm surprised the reactor needs a moderator, I would assume that a liquid fuel reactor could be controlled far better by controlling flow into and out of the critical mass. It's all at normal pressures, just hot (temperature and radiation wise), so just bog standard plumbing practices for handling fluid levels should work. Being able to scramble the reactor by just dumping the contents through a set of diverters into…

One of the great practical challenges with molten salt is to design a reliable valve. At temperatures this high and with the high corrosive properties of the medium, this is not trivial.

Re: Application submitted for US molten salt research reactor

#148

Post by jabl »

nine_k wrote: post #21
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…

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…

I think one fear is about the proliferation of reprocessing technology. So currently, with a traditional LWR, you buy X fuel rods, then later IAEA inspectors come by and check that those X rods are in the spent fuel pool. Reprocessing, to the very little extent it's done at all, is done by countries that already have nuclear weapons (except maybe Japan?), so the horse has already left the barn.

But a MSR, at least for some of the more advanced concepts, would have online reprocessing on site (continually siphoning off fission products and adding small amounts of fresh fuel). Additionally, since the fuel wouldn't be in discrete bundles, I think there's a fear that small amounts of fuel could be diverted to a clandestine weapons program.

Re: Application submitted for US molten salt research reactor

#150

Post by acidburnNSA »

pfdietz wrote: post #133
acidburnNSA wrote: post #56

Earlier quoted context omitted.

LANL built a reactor like that, with liquid fuel in tungsten capsules. It was called LAMPRE. https://www.osti.gov/biblio/4368180-operation-plutonium-fuel...

Tantalum capsules. Molten plutonium is darn corrosive.

Even better.
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