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PostPosted: Mar 12, 2014 7:46 pm 
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A lower degree of separation, repeated, could enable further running of reactor for decades. A rigorous processing could be undertaken at that time only. That may reduce the overall cost of processing.
Frequent purge of gases is one such process. Fractional crystallization of part of fuel could be another.


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PostPosted: Aug 17, 2014 2:59 pm 
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Jagdish wrote:
For getting rid of Xenon you need liquid fuel.
Hydrogen inside the core eats up neutrons.
Graphite changes volume. It caught fire at Sellafield and Chernobyl.
Deuterium is costly. Cant risk leaking at high temperature.
That leaves you with unmoderated fast spectrum MSR. Can anyone do it for purely civilian power? Even with the lollipop of waste burning thrown in?


I agree with your implied conclusion that we need to eschew the notion that "moderation" is either desirable or necessary.

Here's a comparison of the reactor that's sorta-described in the TAP white paper & the no moderator fast spectrum isobreeder described in the last/current version of the paper posted in viewtopic.php?f=3&t=4197MSR .

1) calculations based upon a couple of the numbers revealed in the TAP white paper (HM mole fraction = 27% & total mass = 65 tonnes) suggest that its 0.52 GWe reactor will have about 22 cubic meters of molten fuel salt in it (about 20% greater than that of EVOL's 1.5 GWe MSFR.)
2) I don't see why the TAP reactor's moderator's cladding wouldn't be subjected to about the same fast neutron flux as would an equally powerful MSFR's "barrier tank" wall.
3) assuming that 25% of TAP's fuel salt is in its HXs and that its moderator occupies about 50% of the core and that the density of ZrH1.6 =5.66, its core must contain about 47 tonnes ZrH1.6
4) Since that moderator's lifetime is apt to be limited by its cladding which material probably won't last much longer than would the stuff comprising an equally powerful MSFR's "barrier" wall, which, in turn, should weigh roughly 3-5 tonnes, Transatomic's reactor would generate 30-50 times as much "really crapped up" metallic waste/GWe year as would the MSFR (1.5/0.52*47/3-5)
5) Both the 241Am growth rate depicted in the TAP white paper's Fig 10 plus Am's electrochemical redox potential (more "electropositive" than is either Pu or U) suggests that its writers are assuming that americium would comprise virtually all of its "20 kg of actinide waste/year". They must also be assuming 100% Pu recovery, not the 97% figure which, according to the top boss of ANL's/INL's NE R&D program as of 2009, represents the "best ever" Pu recovery achieved by his/ANL's/INL's pyroprocessing experts.
6) 241Am decays to the same long-lived radioisotope (237Np) which comprises most of my "minimal reprocessing" MSFR isobreeder's TRU waste (i.e., 5.2 kg total TRU/GWe year, 70% of which is 237NP - figures calculated/provided by Carlo Fiorina)
7) therefore, Transatomic's reactor would generate about 12x (1.5/.52*20/5.2) as much equally long-lived TRU waste/Joule as would the MSFR isobreeder
8) Since Transatomic's reactor is supposed to generate just 500 kg of "waste" per year, that figure must not include the misc. salts, nickel wool, metallic Bi. etc., matrices which would surely accompany any FP "reprocessed" from its fuel salt stream. (If one were to apply the same reasoning to the 55 million gallons of stuff in Hanford's tank farm, those tanks would contain only about 0.03% of the "high level waste" that most people and the law seems to think they do)

The last/current version of MSFR paper posted in my thread deliberately doesn't have much to say much about other possible MSR designs (the sole exception being its footnote w) because any attempt I'd make to do so would probably piss off most of the MSR/thorium "community" as well as just everyone else who's trying to convince decision makers that a nuclear renaissance should be implemented with any particular sort of reactor.

In my opinion, one of the biggest problems we're facing is that the leadership of the Western world's MSR/thorium enthusiasts have been forced to adopt a business model similar to those of the people/organizations trying to strike it rich in silicon valley; i.e., convince potential investors that there's a killing to be made by putting money into something based upon intellectual property (IP) the "details" of which must be kept secret. Similarly, I believe that the consequence is that most of the sales pitches being made for those reactors/fuel cycles are misleading; i.e. attribute "LFTR" characteristics (clean, cheap, simple, "sustainable", etc. ) to systems which likely wouldn't possess some of those characteristics.

One of nuclear power's greatest problems is that much of the Western world's citizenry & their elected representatives simply don't trust the habitually secretive & often deliberately deceptive organizations which have come to represent, promote, or "study" (develop?) it. This suggests two things: 1) we're apt to be given just one shot at implementing a genuinely sustainable nuclear fuel cycle with MSRs & 2) it'd better behave as "promised".

My MSFR paper is written the way it is because here in the "free" world, cost related risk dominates decision making & nuclear power's waste issues provide its anti nukes with their most "real" argument*.

PS Section IV-B of the "really final" version of that paper will include mention of Kirk Sorensen's emergency denaturing system (which would dump in some 238UF4 while the imaginary terrorists/proliferators are trying to break through the fence).

Darryl Siemer

* Any genuinely sustainable nuclear fuel cycle will require/invoke a great deal of reprocessing that will generate waste which must be dealt with in a technically competent & totally honest fashion. To date, the USA's decision makers have managed to turn most of its reprocessing waste management exercises into hugely expensive boondoggles; e.g., the ATTACHMENT describes how DOE went about trying to "manage" INL's remaining liquid reprocessing waste. The same people responsible for the decisions which generated that relatively little boondoggle (Hanford's tank waste boondoggle is over an order of magnitude bigger/worse) went on to assume leadership positions at DOE's remissioned/renamed "lead NE R&D lab".


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PostPosted: Aug 17, 2014 3:28 pm 
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The graphite did not burn at Windscale.

If it had been the fire would almost certainly have been uncontrollable.
All that burned was the aluminium cladding on the fuel and the magnesium in isotope cartridges.

Additionally as far as I know there was no major fire in the graphite at Chernobyl - indeed the explosion was a simple steam explosion and any burning was incidental as tiny pieces of it lay on the ground.


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PostPosted: Aug 17, 2014 4:50 pm 
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darryl siemer wrote:
1) calculations based upon a couple of the numbers revealed in the TAP white paper (HM mole fraction = 27% & total mass = 65 tonnes) suggest that its 0.52 GWe reactor will have about 22 cubic meters of molten fuel salt in it (about 20% greater than that of EVOL's 1.5 GWe MSFR.)

Darryl,

I think you are ignoring an important point in your comparison of TAP vs. EVOL's 1.5 GWe MSFR.

Since TAP is moderated, it's fissile loading is much lower: They claim to be able to use fuel enrichment down to 1.8% - ten times less than a fast reactor (....and in a steady-state Candu core, the fissile concentration is three times lower still -- less than NU actually, even while retaining ALL fission product poisons).

Perhaps more importantly, EVOL's 1.5 GWe MSFR is NOT proven to be dynamically stable during operation -- a point that Fiorina freely admits.
While one could argue that the same is true of TAP's concept, the lattice-style layout of the core, combined with the bi-modal spectrum, increases the likelihood of dynamic stability.


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PostPosted: Aug 17, 2014 7:26 pm 
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jaro wrote:
darryl siemer wrote:
1) calculations based upon a couple of the numbers revealed in the TAP white paper (HM mole fraction = 27% & total mass = 65 tonnes) suggest that its 0.52 GWe reactor will have about 22 cubic meters of molten fuel salt in it (about 20% greater than that of EVOL's 1.5 GWe MSFR.)

Darryl,

I think you are ignoring an important point in your comparison of TAP vs. EVOL's 1.5 GWe MSFR.

Since TAP is moderated, it's fissile loading is much lower: They claim to be able to use fuel enrichment down to 1.8% - ten times less than a fast reactor (....and in a steady-state Candu core, the fissile concentration is three times lower still -- less than NU actually, even while retaining ALL fission product poisons).

Perhaps more importantly, EVOL's 1.5 GWe MSFR is NOT proven to be dynamically stable during operation -- a point that Fiorina freely admits.
While one could argue that the same is true of TAP's concept, the lattice-style layout of the core, combined with the bi-modal spectrum, increases the likelihood of dynamic stability.


According to WIKIPEDIA, today's BWRs contain 80 -140 tonnes of "low enrichment" uranium. If "low" means 4 wt% that adds up to 3.2 to 5.6 tonnes of start up fissile/BWR (typ 1 GWe) which figure is comparable to that required by EVOL's reference 1.5 GWe isobreeder. Similarly, TAP's 0.52 GWe reactor would require 1.2 GWe tonne of fissile which corresponds to 3.6 tonne/1.5 GWe.

My paper points out why it shouldn't be tough to come up with enough startup fissile to implement a nuclear renaissance with MSFRs. It also reminds one & all that the purpose of such a renaissance would be to substitute nuclear power for fossil fuels, not solve the Western world's pathological inability to deal with a growing accumulation of spent LWR fuel.

Where did you get your opinion about a MSFR's "dynamic instability"? Please post the doc. documenting Fiorina et al's "admissions" about it.

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PostPosted: Aug 17, 2014 9:27 pm 
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darryl siemer wrote:
Where did you get your opinion about a MSFR's "dynamic instability"? Please post the doc. documenting Fiorina et al's "admissions" about it.


...and continue that discussion in one of the many threads about EVOL/MSFR. Keep this one on Transatomic.


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PostPosted: Aug 17, 2014 9:57 pm 
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Kirk Sorensen wrote:
darryl siemer wrote:
Where did you get your opinion about a MSFR's "dynamic instability"? Please post the doc. documenting Fiorina et al's "admissions" about it.


...and continue that discussion in one of the many threads about EVOL/MSFR. Keep this one on Transatomic.


OK. However, because it's often pretty hard to find just where anything in those many threads might be found, I'd suggest that we do so via email. My address is d.siemer@hotmail.com.

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PostPosted: Aug 19, 2014 1:31 am 
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Given that the moderator is hydrogen - could Transatomic substitute deuterium instead and improve the moderator performance?


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PostPosted: Aug 19, 2014 2:52 am 
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Lars wrote:
Given that the moderator is hydrogen - could Transatomic substitute deuterium instead and improve the moderator performance?


Doesn't work with zirconium hydride. Because, while deuterium is more efficient in terms of reducing neutron captures, it also has a lower slowing down power... so to maintain the spectrum you need loads more zirconium, which more than offsets the advantage in neutron absorption deuterium affords over ordinary hydrogen...


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PostPosted: Aug 19, 2014 2:55 am 
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Here's my main issue of concern with TAP.

They rely on a cladding that does not yet exist. Cladding development, testing, safety testing, safety analysis... will be their critical path to deployment. Its a big gamble. If they can make the cladding work reliably and safely, in a reasonable time frame, and convince regulators of this, then they are in business. If they can't make the cladding work, their ship is sinking.


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PostPosted: Aug 20, 2014 7:24 pm 
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Cyril R wrote:
Lars wrote:
Given that the moderator is hydrogen - could Transatomic substitute deuterium instead and improve the moderator performance?


Doesn't work with zirconium hydride. Because, while deuterium is more efficient in terms of reducing neutron captures, it also has a lower slowing down power... so to maintain the spectrum you need loads more zirconium, which more than offsets the advantage in neutron absorption deuterium affords over ordinary hydrogen...

Yes, that sums it up nicely.

Deuterium is great, but not with zirconium in bulk moderator.

Zirconium needs to be minimized - thin tubes, low numbers, is OK but not more than that.

That's why TAP's concept can never be an isobreeder.


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PostPosted: Aug 24, 2014 7:11 pm 
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Cyril R wrote:
Here's my main issue of concern with TAP.

They rely on a cladding that does not yet exist. Cladding development, testing, safety testing, safety analysis... will be their critical path to deployment. Its a big gamble. If they can make the cladding work reliably and safely, in a reasonable time frame, and convince regulators of this, then they are in business. If they can't make the cladding work, their ship is sinking.


The reason why silicon carbide might not be a good choice for cladding anything going into TAP’s “WAMSR” ( or a LFTR or a MSFR or a MOSART or ....) was pointed out by Prof. Peterson about a decade ago; i.e., thermodynamic considerations suggest that it’s apt to corrode in molten fluoride salt solvents containing uranium fluoride accompanied by the usual mix of fission product fluorides (see http://pb-ahtr.nuc.berkeley.edu/papers/ ... safety.pdf ). Recently, my own calculations performed utilizing HSC’s (version 5 circa 2002) embedded thermodynamic constants (for ~17,000 species including everything that’s apt to be relevant in this scenario) plus some alternative data found at NIST’s website, indicated both that such corrosion would be severe (virtually quantitative) & that its primary product would be gaseous SiF4 formed by the reaction of those “less stable” fluoride salts by SiC to form metal carbides (e.g., UC). However, since my version of HSC also predicts that clean FLiBe would react with SiC, I’m not all that sure that thermodynamic driving force has much to do with its corrosion rate.

Because the USA was/is only considering the use of such salts as coolants/heat exchange fluids in hypothetical graphite moderated, solid fueled, reactors in which case they would be both purified of such contaminants & sufficiently redox adjusted to scavenge free fluorine, this corrosion issue wasn’t considered a showstopper. Indeed, recent experimental work performed at the University of Wisconsin (Madison) indicates that several different forms of SiC are quite resistant to clean coolant salts (see http://www.iaea.org/NuclearPower/Downlo ... e_2014.pdf )

I’ve written a note to the authors of that report (cc’d to their colleagues at other institutions) asking whether or not anyone who’s worked on the FHR/PB-AHTR’s materials corrosion issues has ever slipped-in a corrosion test performed with “dirty” salts. Let’s hope that somebody’s shown enough initiative to do this.

Remember, what counts here is actual corrosion rate (not the potential for corrosion) – if the reactor is designed so that its guts are both easy & cheap to replace at a reasonable interval, those parts don’t determine its safety or “lifetime” (think about a car’s tires).

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PostPosted: Aug 25, 2014 4:48 am 
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Cyril R wrote:
Here's my main issue of concern with TAP.

They rely on a cladding that does not yet exist. Cladding development, testing, safety testing, safety analysis... will be their critical path to deployment. Its a big gamble. If they can make the cladding work reliably and safely, in a reasonable time frame, and convince regulators of this, then they are in business. If they can't make the cladding work, their ship is sinking.


A lot of work has been done on containing H for LiH, related to NASA work. The best seems to be multiple oxide layers to seal the H in. With molten salt, this would only work on the ZrH1.6 side of the cladding because the salts would strip the oxides away. But, guaranteed continuous multiple layers of oxides, I think would be hard to guarantee for that much ZrH1.6.


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PostPosted: Jul 04, 2015 1:01 pm 
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What would happen if you substituted enriched Zirconium (from a plasma centrifuge) into this design?
The significantly improved neutron captures in the zirconium would improve neutron economy and might even allow for deuterium to be used in the moderator.


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PostPosted: Jul 07, 2015 10:47 pm 
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The design uses zirconium hydride in cladding as moderator. If the hydrogen moderator as supercritical water is contained in zirconium capsules, it may achieve a higher hydrogen concentration. The hydrogen losses could also be reduced.
The corrosion proofing of capsules could be achieved by a nickel fluoride enamel on the capsules.


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