Salt versus Sodium explosion - in water

General discussion of thorium and nuclear energy.
KitemanSA
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Re: Salt versus Sodium explosion - in water

Post by KitemanSA » Aug 28, 2016 12:39 am

alexterrell wrote:1. A failure of the salt / water heat exchanger. All MSR designs seem to have 3 or 4 loops, so this particular heat exchanger can be isolated from the fuel salt. Nevertheless, developers will need to prove that any explosion is contained in the secondary or tertiary loop.
In truth, there should be no salt/water heat exchanger. Even in early steam turbine units, the steam generator should never have water at the same point as molten salt. It shoud be a recirculation boiler, steam superheater unit.
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Kurt Sellner
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Re: Salt versus Sodium explosion - in water

Post by Kurt Sellner » Aug 28, 2016 12:49 am

TerjeP,
I believe that you are correct that the solubility of the material has a significant influence on the effects. This was even shown in the video with a less soluble material, it did not react nearly as violently. The theory given by the "backyard scientists" is probably correct but, IMHO, he wasn't thinking small enough. He said something like the salt was breaking up in the water and allowed for a very large surface area. I believe that this surface area was large because the molecules were being dissolved by the water. It's not just extremely small granules of salt dissipating this heat but the individual atoms.

He did test the pH of the water as a means to verify a chemical reaction did not occur but, IMHO, all that showed was that the reactions balanced. Also, I learned in high school chemistry that water has a small buffering nature of its own, it will maintain pH even if acted upon by weak acids or bases. Some other testing would have been helpful. Did he try tasting the water?

One way to test this theory is find something that is finely ground but will not dissolve in water, like sand, and heat it to the same temperature and drop it in the fish tank. Compare this to something with a similar solubility in water but consisting of elements that are less reactive to water. Just guessing on what that something might be and still be cheap and available enough for a backyard scientist, how about potassium chloride? Maybe use some of that stuff that's supposed to melt ice on sidewalks but not kill the grass in the spring, is that calcium chloride?

Testing this properly on a shoestring budget would be difficult. Actinides are rather unique in their density and solubility while also being radioactive. If a sufficient quantity is obtainable then it's unlikely one would be willing to risk the stuff being spread out all over their lawn.
Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.

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TerjeP
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Re: Salt versus Sodium explosion - in water

Post by TerjeP » Aug 28, 2016 3:25 am

What would be a more realistic test would be to get a large pool of each at ~500º and throw a bucket of water in.
That would be interesting. But it is only more realistic for a particular accident scenario which is water leaking into the reactor. The alternate scenario where the reactor room is flooded and salt leaks out (eg due to a ruptured pipe) is better tested by adding a bucket of molten salt to a large body of water.

So in paractice I think both scenarios ought to be tested. And at temperatures both at and above normal operating temperature.

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Re: Salt versus Sodium explosion - in water

Post by KitemanSA » Aug 28, 2016 3:58 am

Why would the reactor room be flooded with water? There is no need for water anywhere in the reactor room.
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TerjeP
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Re: Salt versus Sodium explosion - in water

Post by TerjeP » Aug 28, 2016 8:42 am

Tsunami.

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Tim Meyer
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Re: Salt versus Sodium explosion - in water

Post by Tim Meyer » Aug 28, 2016 9:34 am

TerjeP wrote:If you actually want a conversation pick one question out of the multitude and I'll try and answer it.
Looks like others are picking up on the point: FE LFTR design vulnerabilities.

Thanks for the "chill out"—whew! I do want a conversation. With you and everyone here. Can you answer the "NASA" - Thorium Remix 2016 question, please? Public outreach in selling the fluid-fueled (molten salt) reactor designs that are being purported as safer than LWRs is one area I might be qualified for. Does that make sense?
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Tim Meyer
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Re: Salt versus Sodium explosion - in water

Post by Tim Meyer » Aug 28, 2016 9:39 am

KitemanSA wrote:Why would the reactor room be flooded with water? There is no need for water anywhere in the reactor room.
Tsunami protection for a MSR would be part of the licensing plan; seismic and many considerations. The FE LFTR IHX couples to scCO2 by design. The PCS heat rejection is by water (but can it be air cooled?). ThorCon uses steam generators in their design, and the TEI IMSR also, yes?

I'm glad to see your post, Terje, has evoked the MSR safety discussion.
"Those who say it can’t be done are usually interrupted by others doing it."

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Kurt Sellner
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Re: Salt versus Sodium explosion - in water

Post by Kurt Sellner » Aug 28, 2016 6:32 pm

TerjeP wrote:Tsunami.
Excellent answer. To better emulate that the experiment should be with water already saturated with salt, that would affect the rate of dissolution. Another thing to do would be to perform the experiment in a vessel that was sturdy enough to contain it. A MSR is not going to have glass walls as containment. The reactor hall might be buried, in which case the walls would be backed up by many tons of dirt. If above ground the hall would be enough steel and concrete to hold in the radiation and/or hold back a potential terror attack. If the vessel didn't fail then we might actually see something more violent happen, the water shooting up like out of a cannon.
Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.

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Re: Salt versus Sodium explosion - in water

Post by KitemanSA » Aug 28, 2016 6:58 pm

TerjeP wrote:Tsunami.
Sealed like a submarine. Easy to make water proof to 50m+.
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TerjeP
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Re: Salt versus Sodium explosion - in water

Post by TerjeP » Aug 28, 2016 9:34 pm

I think there is a distinction to be made between what can go wrong if molten salt hits water and the solutions you then engineer to deal with that problem. Jumping to solutions is perhaps natural but it is also putting the horse before the cart. First we should establish how big a problem it is if our molten salt (FLiBe or otherwise) hits water and then look at how we deal with that risk (eg strong reactor vessel, below grade installation, etc).

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TerjeP
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Re: Salt versus Sodium explosion - in water

Post by TerjeP » Aug 28, 2016 9:47 pm

"NASA" - Thorium Remix 2016 question, please?
Via Kickstarter I donated funds to Gordon McDowell for the 2012 Remix. I donated at the level necessary to get my name in the credits because I wanted bragging rights. But Gordon never followed through on that promise. I've never complained to him though because the guy is too much of a legend. The fact that he makes all these videos is just fantastic.

I watched the 2016 remix and showed it to friends. It's too long. Too focused on space. Needs more editorial polish. If I was talking to Gordon I'd suggest he make lots of 3 minute videos that deal with a single specific issue about nuclear in a clear, concise and entertaining way. I'd love to see a video that explains quickly how using molten salt saves money by shrinking the containment building. Keep it funky like the guy with the exploding fish tank. People like watching things go bang.

I'm not sure if I've answered the question. If I'm off track let me know.

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Re: Salt versus Sodium explosion - in water

Post by Kurt Sellner » Aug 28, 2016 10:00 pm

KitemanSA wrote:
TerjeP wrote:Tsunami.
Sealed like a submarine. Easy to make water proof to 50m+.
Like what has been proposed by Terrestrial and Thorcon? There might still be a coolant salt loop that could leak in a tsunami but it will not contain fuel and radioactivity will be minimal, as in barely above background.
Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.

alexterrell
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Re: Salt versus Sodium explosion - in water

Post by alexterrell » Aug 29, 2016 2:58 am

TerjeP wrote:I think there is a distinction to be made between what can go wrong if molten salt hits water and the solutions you then engineer to deal with that problem. Jumping to solutions is perhaps natural but it is also putting the horse before the cart. First we should establish how big a problem it is if our molten salt (FLiBe or otherwise) hits water and then look at how we deal with that risk (eg strong reactor vessel, below grade installation, etc).
I'm not sure how far (how improbable) the regulators will go.

If terrorists fly a plane into the reactor hall just before a Tsunami strikes?
In a week, P = Probability of aircraft impact x probability of tsunami x probability impact was before the tsunami
P = 1/50000 x 1/50000 x 1/2

Even then though, there should be undamaged reactor cores (or drain tanks) sitting underneath a wrecked and flooded reactor hall. No core breach.

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Re: Salt versus Sodium explosion - in water

Post by TerjeP » Aug 29, 2016 4:23 am

What if we're building a nuclear ship?

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Re: Salt versus Sodium explosion - in water

Post by alexterrell » Aug 29, 2016 4:49 am

TerjeP wrote:What if we're building a nuclear ship?
For that, I'd go for lead cooled reactors. In the even of destruction, the fuel elements are encased in lead which will last long enough for all the fission products to decay. Failing that, a PWR might do - the NuScale reactor is well sized (60MW) for very large container ships.

I wouldn't go for a soluble fuel.

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