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.

There's quite the discussion about this over at Slashdot.
https://hardware.slashdot.org/story/18/ ... r-reactors

The people are are largely computer geeks and IT nerds and this got their attention because Bill Gates is involved. There seems to be a heavy bias for wind and solar power among the moderators, editors, and commenters but this time seems different. There seems to be more people defending nuclear power this time than in the past. Maybe, again, because Bill Gates is involved and he has his fans among the people there. I'm guessing that a lot of people there are in college now or recently graduated, young but old enough to vote. If this is indicative of how the next generation feels on nuclear power then the future looks bright.

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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.

This is good “news” but not really new. Exactly what’s been going on or even the goals of Terrapower’s DOE’s/Southern Company’s collaboration remain as much a secret now as they were two years ago.

For instance, is it going to “breed and burn” or be a genuine breeder? There’s a pretty big difference. Two years ago (Oct 5, 2016), I posted an analysis of what Terrapower’s patent disclosures revealed in this thread. Basically, I’d concluded that its example 3.42 GWt, MCFR would be about 5 meters in diameter, and initially contain about 123 tonnes of 15% 235U. At the end of its 70 year breed-and-burn cycle another 92 tonnes of raw (or depleted) uranium would have to have been added as well. Assuming that…

• its initial startup uranium was 15% enriched (a reasonable guess but of course another secret)
• 1/7 of the original uranium’s 235U was discarded during enrichment
• Its thermal-to- electricity conversion factor was 45%

This translates to about 29.4 tonnes natural U/GWe-year which is about 5x better than today’s most “advanced” burners can achieve but still a long ways from the roughly 1 tonne/GWe-year that a genuine breeder would need.

I’ve just reread Bupp & Derian’s, 1978 book, “Light Water: how the nuclear dream dissolved”. One of the reasons that it had already pretty much unraveled by then was the fact that nuclear power’s champions have always been pretty sneaky (deliberately vague) about what they were selling & by that time it’d become pretty obvious that some of the “promises” they’d made weren’t apt to come true. For instance, the Terrapower’s patent “publications” mentioned above indicated that their reactor would consume 43% of U without bothering to mention that the vast majority of the uranium actually mined to make its fuel would end up in the “temporary” discard pile.

I can understand why businessmen and politicians like “breed and burn” (& "batteries") because most of their waste management and reprocessing responsibilities/issues are kicked a long ways down the road. However, the big downside of all such “easy” scenarios is that they would require a lot more startup fissile and therefore further delay realization of Weinberg & Goeller’s (& my - see ATTACHMENT) clean & green, nuclear-powered, future.

This news is good primarily because it demonstrates that the US nuclear industry’s (& DOE’s) old guard are no longer dictating what its own people & contractors can think about.

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Darryl Siemer

My comment on things looking bright is primarily on how people seem to respond to nuclear power now as opposed to even a year ago. I'll agree that this news isn't exactly news but what's news to me is that people aren't dismissing nuclear power like they used to. There's been a couple more entries on the Slashdot news blog concerning nuclear power since I made my comment above and there is continued support for more nuclear power. Here's another such discussion on nuclear power safety and people are again saying nice things about nuclear power.
https://science.slashdot.org/story/18/0 ... -fukushima



Yes, this is good news. These people in DOE and NRC got there because of people voting for politicians that are supportive of nuclear power. I recall a comment from Bill Nye on how public opinion changes as people "age out" (his words) of the pool of voters. While I find his euphemism an odd phrase he is right, every election is from a different pool of people. I'm rather pleased seeing this pool seeming to grow in support of nuclear power.

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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.