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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

#121

Post by credit_guy »

YakBizzarro wrote: post #47
ars wrote: post #41

Earlier quoted context omitted.

> 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…

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, the damage would be very localized, it would affect at most one cell, and the immune system is easily able to handle that.

Re: Application submitted for US molten salt research reactor

#122

Post by jasonwatkinspdx »

lolc wrote: post #93
elihu wrote: post #87

Earlier quoted context omitted.

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 interest…

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 :-)

Ok so I recently watched a video that went into some of this, and I had know idea how crazy some of these nuclear fuels are in terms of physical requirements.

If I recall the video correctly, solid metal oxide fuel produces offgas at a 50:1 ratio, while being insanely dense. This produces pretty insane internal pressures if the goal of the fuel design is to keep everything contained. Like strong enough to eventually cause mechanical failure of the fuel.

I think there's a lot of really difficult constraints intersecting in these fuel assembly designs, and something that seems obviously simple probably isn't.

Re: Application submitted for US molten salt research reactor

#123

Post by powerhour »

phonon wrote: post #100
powerhour wrote: post #57

Earlier quoted context omitted.

It seems to me that companies like GE and Westinghouse have tons of money. Add that to the billions pro-nuclear folks have in SV and you've got quite the war chest to fund effective pro-nuke campaigns.

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.

Re: Application submitted for US molten salt research reactor

#124

Post by Retric »

chris_wot wrote: post #117
ortusdux wrote: post #107

Earlier quoted context omitted.

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.

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.

Re: Application submitted for US molten salt research reactor

#125

Post by throwoutway »

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…

Which of these do you think ACU's NEXT project is pursuing?

Re: Application submitted for US molten salt research reactor

#126

Post by jxf »

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…

> 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?

Re: Application submitted for US molten salt research reactor

#127

Post by onlyrealcuzzo »

werdnapk wrote: post #118
mulmen wrote: post #104

Earlier quoted context omitted.

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?

At 3100 F.

Salt melts at 1474 F.

Re: Application submitted for US molten salt research reactor

#128

Post by AtlasBarfed »

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…

Well, one thing about liquid fuel vs solid fuel is that you can move the fuel to a new reactor and, uh... ?"recycle"? / ?"overhaul"? the old one. So you could use one for 7 years why the other is retrofitted. You'd need two reactors... or... you'd need 8 and seven are online while 1 is replaced per year.

So unless materials is solved, you need scalability and replacement. At least the OTHER problem with solid fuel, lots of waste, is generally not a problem with breeder reactors and liquids. You remove the fission products from the fluid and feed it back in. I'm no chemist so I don't know all the separation nastiness involved, but it's better than carting ten thousand year waste across the country to Yucca.

So the question is, what about the other reactor designs, don't they need replacement with respect to the vessel? And as I understand it, fusion reactors also have issues with high speed neutrons so their vessels would need periodic replacement, even if they get to sustained ignition and positive energy.

Your replacement containment layers seems like the "constant replacement" strategy. What if you could simply inject a new layer that hardens and pushes out the older layer?

Also, why not have solid uranium or some similar material as the inner container? Could simple saturation of the existing uranium in the salt prevent excessive wear?

I wonder how much of this approval is because the Chinese brought one online.

Re: Application submitted for US molten salt research reactor

#129

Post by AtlasBarfed »

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.

I'm not a nuke physicist, but I recall LFTR presentations on the "safety plug" to stop meltdown: basically a plug melts and the fluid flows into a shallow pool.

Since the fluid is "thinned", neutron economy plummets and chain reactions stop.

In addition, I though the fluid would expand a bit under high heat in the reactor, which would drop neutron economy as well, so a fluid can somewhat self-moderate.

So unless the fluid is in a ball or tank where the neutron economy is maintained in three dimensions, if you drain it out it no longer has the neutron economy.

So what they probably are saying is that since the fuel is fluid, and if you need to replace the moderator, you drain the fuel (and as stated above, that stops the reaction as well) and replace the moderator.

Re: Application submitted for US molten salt research reactor

#130

Post by AtlasBarfed »

jacquesm wrote: post #75
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…

There have been quite a few solar energy concentrator test beds based on molten salt in order to try to get to 24/7 solar power. It is an interesting technology but afaik it's not at the stage where it can be rolled out reliably and maintenance free.

It also simply couldn't compete with plummeting cost in silicon panels.
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