Wow. There indeed are wise men in the desert.

Note the date, gang!

Ivan - given that LFTRs cannot physically be built, since no seed blanket material exists, I would strongly suggest that you not do that! That said, today is April Fool's Day!

I like a good April Fools joke but MSRs/LFTRs have enough difficulty being taken seriously in the academic, finance and engineering realms already and nonsense like this can do a lot of harm. This is also a world wide effort and certainly April Fools day isn't known worldwide. I strongly suggest you take this joke post down now before it does further damage.

David LeBlanc

I like that Twitter is now charging for vowels.
;]

Alex -

"No seed blanket material exists" refers to the two-fluid LFTR design with an outer blanket which Kirk is so fond of. No seed blanket (calandria) material is currently known which can simultaneously permit neutron fluence, as well as be chemically resistant.

Your statement above can only mean that you either don't know this or don't realize that your statement above more safely describes the MSR ("the single-fluid machine...").

Alex, Solidspin,

Take it easy guys. How's this for a compromise, you are both are way off...

Solidspin, just because we don't have a material that we can point to extensive testing in a strong flux and fluoride salt doesn't equate to saying it doesn't exist. Think of all the structural material used in every other reactor in the world in a strong flux. Molybdenum is great in both a strong flux and great with the salt, just not demonstrated. SiC, fine in the flux, yet to be proven with the salts. Graphite itself for modest dimension barriers (not multiple ones though). Lots of choices just zero funding for 40 years to do experimental work. That said, I agree the single fluid approach just simplifies the outlook.

Alex...
"And, do you not know that the separating material can be the same stainless used for plumbing, even thinner, because of the small pressure difference between volumes."
Not sure what you are talking about here. Very little chance stainless steel would be used, it has never been used in a molten salt reactor before. Might be an outside chance of some form of steel used if one really drops the temperature. Hastelloy N, a nickle is used and it would have quite a short lifetime (but again if the design is simple enough, maybe even that is good enough).

If you guys can't play nice I'm going to have to send you to your rooms with no internet...

I bow to your chemistry kung fu, not my domain at all but Moly was studied quite a bit at ORNL and even at 1100C proved well behaved in fluoride salts (unless somehow colder is worse). Now an engineer will moan about low temperature fragility but as someone once said, just don't go hit it with a hammer.

J.W. Koger, A.P. Litman, Compatibility of molybdenum-
base alloy TZM with LiF–BeF2–ThF4–UF4 (68–
20-11.7–0.3 mole percent) at 1100°C, Oak Ridge
National Lab, Oak Ridge, TN Report ORNL-TM-2724,
1969.
Y. Desai, K. Vedula, A.K. Misra, Corrosion of refractory
metals in molten LiF, J. Met. 40 (1988) A63.

Moly or TMZ is not neutron transparent but certainly no net problem to make a breeder if it is just a few mm or even a couple cm of barrier (remember everyone else has tonnes of metal in their cores).

I know SiC has potential issues, but they will be testing it soon in the loops at ORNL so we'll know for sure.

In terms of graphite, depends what you mean by calandria. Yes certainly a no go for anything complex but for a single barrier some shrinkage and expansion is doable since we don't really need it to be vapor proof, just leak proof.

As they say though, the proof is in the pudding and the DOE has effectively stopped us from cooking any pudding for 40 years.

Hello, David L:

Yes, I am well aware of the ORNL report you cite. If you look carefully at the data, the Ti and Zr are naturally solubilizing out of the TZM! This is structurally disastrous, b/z the crystal structure is changing, leaving vacancies in the lattice positions. Ergo, this isn't just an issue of embrittlement, so I would caution you on this point. Dope in Nb and you could potentially stave this off but of course, I would love to test my hypothesis on the Nb doping. Alas, I cite your astute point you raised previously. You also run into the fact that all three elements have nettlesomely large neutron cross sections - nettlesome because they are all in the minority for each (Ti-47,49; Zr91; Mo95,97) but that adds up quickly under these conditions.

I am unable to access the J. Met. article. I will be emailing you off-thread (if this website permits such communication). Perhaps you could share this file with me.

Yes, I am painfully aware of the ORNL SiC testing. I have recently published a SiC paper, which pretty conclusively documents the 40+ years of negative results of SiC exposure to fluorinating baths. When Nokamura, et al. exposed the alpha, beta polytypes of SiC to only three days of FLiBe at 650°C, they quantified the dissolution rate, which was substantial.

I am not averse to looking at graphite (or GO) as such, for a material in the manner you propose, but it can serve no structural purpose. Any sound investment must spend every square cm twice, so as to have it make financial sense at the end.

"Cooking any pudding" I love the rapier wit.

ondrejch: Please send me the SiC article (ajshaka@uci.edu). I am less concerned with the fabrication of a barrier between fuel and fertile fluids than I am with the whopping off-scale toxicity of beryllium. The allowed exposure limit is 1 microgram per cubic meter! Even though BeF2 is unlikely to "go anywhere" it could contaminate groundwater, and getting approval to heat it up requires a hood like a jet engine. With the recent unfortunate accident at UCLA in which a young woman died after a fire in an organic lab, safety has become a major concern at UCI. Working with FLiBe gets the EH&S people shaking their heads. That, and the 99.995% Li-7 enrichment, the ability of tritium to penetrate solids, etc., etc., allow me, as a chemist, to see why the conclusion was that a LFTR would have a low probability of a criticality accident, but a high probability of a reprocessing accident. Much of the ORNL program was of the "crash" variety-- get it done, and get it done now. Concentrating only on the neutronics is too myopic. The safety analysis should take into account chemical toxicity, possible release of gases (like HF or F2) and explosion hazards (like H2). Put altogether, I see the LFTR as a project that comes dressed in overalls and looks like work. But it is work that we should all try to contribute to.

All the best,

A. J.