Energy From Thorium Discussion Forum

Absolutely right. That's what I keep telling INL's reactor R&D experts. They've been pretending that they can build new reactors with nothing other than modeling ever since INL became the "lead lab". That's as much BS now as it was 50years ago - the difference is that the AEC's experts realized that fact.

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Darryl Siemer

One thing chloride salts have going for them, at least in terms of chemical corrosion knowledge, is many years of experience with pyroprocessing research. In both the US and Korea (KAERI).
According to reports, a thin coat of HfN in melting pots protects the vessel walls.

It's hard to imagine that a HfN coating surrounding the core of any sort of high flux reactor would last very long - Hf's transmutation neutron cross sections are too high. The thicknesses of such coatings are typically very low (measured in Angstroms) so they are apt to be both totally & quickly "eaten up".

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Darryl Siemer

I looked at that a while back....
....I'm not so sure that's true.
Might be an issue for, say, a 40 year life.
But it's just a bucket with nothing in it..... 20 years might be OK.

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Here's a nice project for you. Download Fiorina's PhD thesis & do a smoothed plot of its Fig 1.3 (normalized neutron spectra of several U based fast reactors vs neutron energy). Note that most of the neutrons though "fast" are well under 1 Mev. Then do a numerical calculation of the fraction of those Hf isotopes transmuted/s at a so-distributed total flux of 10+15 neutrons/cm2/s based upon your ATTACHMENT'S numbers.

I'll do it too when I get THE time & we can compare notes - tonight I've got to go see what Dr. Kotek has to say about DOE's NE R&D program.

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Darryl Siemer

It's great PhD thesis. Already have a copy.
I also note that it's about MSFR, not MCFR.
Significant difference.
Both in fuel loading and in F-vs-Cl inelastic scattering & moderation.

Along similar lines - albeit somewhat tangential to this topic - it's interesting that decades of neutron absorption by natural Zirconium in CANDU pressure tubes, does not significantly shift the isotopic composition to less absorbing Zr isotopes.

For similar reasons (having to do with Avogadro's Number), I would expect a HfN coating to last some years as well.

Coating failure is generally caused by its peeling off, cracking etc., not by its being totally dissolved off or "transmuted" to something else. In this case, it's realistic to assume that the fraction of Hf transmuted per year will be on the order of 3% (barns * 10^24cm^2* flux/cm^2/s * #seconds/year). If the resulting composition changes cause cracking, etc., then the coating will fail to protect whatever it's covering.

Per Peterson pointed this out to me when I'd suggested nickel plating the stainless steel guts of a fluoride salt-based MSR. In any case, it's something that only real-world experimentation will prove one way or the other.

The latter (...only real-world...) was the gist of my "question" to DOE's head NE R&D honcho after his talk last night.

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Darryl Siemer

What about using ZrN instead of HfN?

It should be possible to increase the thickness of any coating to increase the life.
An alternative could be a replaceable thorium sleeve/liner to also act as a blanket. It could be changed periodically along with fuel change, to extract U-233.