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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

#161

Post by panick21_ »

This is so fantastic. That a 'Christian' university would do this is kind of insane to me, but I take it.

So many problems with nuclear in the last 50 years are that there simply are not enough experiments and research reactors.

If you don't have them, then how can you ever test new materials.

The original molten salt experiment reactor was only not that much bigger then this university reactor and didn't cost a huge amount, but it lead to such amazing research results including new materials that were designed when making it.

New materials can't easily be qualified without having the necessary research infrastructure.

Re: Application submitted for US molten salt research reactor

#162

Post by japanuspus »

credit_guy wrote: post #121
YakBizzarro wrote: post #47

Earlier quoted context omitted.

Not compltly accurate. It's true that the half-life of tritium is short compared to long lived actinides. However, like hydrogen, it diffuses very easily and it's not easy to contain. In fact, it's one of the few things emitted in the environment during normal reactor operations. As beta emitter, you are right that it's dangerous only when ingested, but it's very easy to breath of to get it from other ambient sources

> you are right that it's dangerous only when ingested Not really. Tritium is Hydrogen. It cannot bioaccumulate. Each atom of Tritium will spread out to become one among the quadrillions of atoms of Hydrogen in our body. Most will get out of the body in a matter of days, long before they've had a chance to decay. Even when they decay, they undergo beta decay, which is not very damaging. But even if it were damaging,…

One tidbit on information damage that has stuck with me is that carcinogenic radiation damage is a second order process: to get a cancerous mutation you need both copies of DNA damaged, which would in most cases require two separate events.

To the extend this is true, it implies that it is the square of the radiation dose that determines carcinogenic effects: Half the dose would cause only a fourth of damage.

Re: Application submitted for US molten salt research reactor

#163

Post by pfdietz »

panick21_ wrote: post #154
pfdietz wrote: post #131

Earlier quoted context omitted.

The corrosion issue is part of what drove Moltex to their rather interesting design (sterile coolant salt is a fluoride; fuel salt in tubes is chloride; this is a fast reactor.) The absence of uranium in the fluoride allows it to be operated at a redox potential where chromium does not dissolve.

Yes, one of the reason I like that reactor design. They basically put something in the fluoride that is basically designed to corrode so that the actual reactor vessel doesn't. If I understand correctly. Their design doesn't require the 7 year swap cycle most MSR do.

Right! They've got the same thing going that ordinary LWRs do: the neutrons lose their energy in a surround liquid rather than in a solid moderator or solid structural materials other than the fuel rods (which are designed to be replaced often anyway). The design even adds some hafnium to the coolant salt (substituting for zirconium, which is the sacrificial metal you refer to there); hafnium serves to shield the reactor walls from thermalized neutrons.

One additional advantage of separating the fuel salt from the coolant salt is that the coolant salt volume can be increased as desired, making the thermal inertia of the reactor as large as one likes independent of reactor power or size of the fuel load.

Re: Application submitted for US molten salt research reactor

#164

Post by pfdietz »

jabl wrote: post #142
pfdietz wrote: post #71

Earlier quoted context omitted.

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 pe…

It means the offgas storage system has to be designed for a large heat load, even in accident scenarios. It also means the common MSR talking point that the FPs stay in the salt is not correct.

Re: Application submitted for US molten salt research reactor

#165

Post by carlmr »

ortusdux wrote: post #138
jxf wrote: post #126

Earlier quoted context omitted.

> The standard way to test material's resistance to molten salt is to put a coupon in a crucible full of salt for a few hundred hours. Q: What is a coupon in this context?

It's used 2 ways in metallurgy. Mainly it is a term for test pieces cut from a batch of metal and used for proof testing. Tensile, elongation, fatigue, weldability, and many other tests require destructive testing coupons. When you take welding certification tests, you weld two coupons together, and then submit your coupon for testing. It is also a term for strips of metal that you mount in a corrosive environment as…

>test pieces cut from a batch of metal

>strips of metal

I mean in essence you just have to look at the word. Coupon is from French couper, which means to cut. So it's a cut-out. It has the same meaning when you look at extreme couponing and metal testing.

Re: Application submitted for US molten salt research reactor

#166

Post by mnw21cam »

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.

A moderator is a material that slows neutrons down. Slow neutrons are more likely to initiate fission in a Uranium (or other fissile) nucleus that they hit, so a moderator increases the reactivity of the reactor.

Re: Application submitted for US molten salt research reactor

#167

Post by jabl »

pfdietz wrote: post #164
jabl wrote: post #142

Earlier quoted context omitted.

> "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 pe…

It means the offgas storage system has to be designed for a large heat load, even in accident scenarios. It also means the common MSR talking point that the FPs stay in the salt is not correct.

> common MSR talking point

Well, a lot of 'common MSR talking points' are overblown, firmly detached from reality. Or at least conveniently ignoring all the significant challenges remaining in industrializing MSR technology. MSR fanboys are the most tedious of the pro-nuclear side of the energy debate, perhaps beaten only by the "this entirely unproven aneutronic fusion concept will imminently solve all our energy woes" crowd. :)

Re: Application submitted for US molten salt research reactor

#168

Post by mikewarot »

Rokid wrote: post #147
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.

I didn't realize that the viscosity stays high for molten salt[1], that makes everything abrasive, along with dealing with possible phase change if the salt solidifies... yikes!

So, what we're dealing with is highly radioactive corrosive molasses with a constant stream of radioactive decay product gasses bubbling out of it, like Xenon and Iodine. Yeah, that seems more challenging that I first thought.

  1 - https://www.powermotiontech.com/home/article/21144640/armoring-a-valve-against-molten-salt

Re: Application submitted for US molten salt research reactor

#170

Post by ethbr0 »

panick21_ wrote: post #152
Retric wrote: post #124

Earlier quoted context omitted.

Nothing requires this research to to be carried out in the US specifically beyond funding being available here. It’s really the inherent difficulties which is holding back progress.

My understanding is that you are not allowed to build a research reactor that is bigger then a university reactor but isn't a full scale energy producing reactor. My understanding is that for such a reactor you would need the full operating license just as a grid connected PWR. And since in the US its essentially impossible to get a license for anything but a PWR, that isn't rally possible. Technology independent reg…

> Technology independent regulatory framework is one of the main reasons Canada has so many reactor startup

Canada's vast tracts of land wouldn't hurt either. If a meltdown or containment breach happens, and no population centers are within 400km, that's a much better bad scenario.

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