Breeders and EROI

[Gregory Meyerson]

I have been trying on and off (intermittently) to track down numbers that I could comprehend on the impact of, say, Integral Fast Reactors or LFTRs on EROI for nuclear.


That it would boost EROI a bit is based on my sense that the fuel energy cost is not a major part of energy invested so the improvement would not be all that great. and large EROI improvements for Gen 4 reactors have come from other areas. You would save on mining energies one could argue but that would be set against processing energy expenditures. 


We have asked some of the EROI people what they thought and they were too unfamiliar with energy budget dynamics to really know. I saw something on line by an energy blogger named Pickering I think who suggested that IFRs (he mentioned them by name) would boost EROI from 100 to 114. But I had no feel for how this was arrived at.


Anyway, does anyone know of any studies of EROI for reactors that use their fuel more efficiently (IFRs and LFTRs)??

I would appreciate any help you can offer.


Greg

[Gregory Meyerson]

In the above message, I meant "IFR people" not "EROI people," the latter obviously being familiar with energy budgets.

[engineerpoet]

I've stumbled across estimates of the cost of reprocessing, but nothing on the energy requirements.  That might have just taken a nosedive with the new nitric acid U/Tu recovery process announced by TAMU.

today.tamu.edu/2020/05/04/study-reveals-single-step-strategy-for-recycling-used-nuclear-fuel/

We just had some discussion about this either here or at r/nuclear on Reddit.

[gregory]

Thanks EP: you are thinking the energy requirements would take a nosedive with this crystal separation process?


Conceptually, for breeders vs once through, would it be a question of energy for the reprocessing versus the energy for mining, fuel processing (not reprocessing) and waste storage for the once throughs?

[engineerpoet]

May 20, 2020 8:12:46 GMT 9.5 gregory said:

Thanks EP: you are thinking the energy requirements would take a nosedive with this crystal separation process?

Go read the article.  The process involves only solution and crystallization in nitric acid over a fairly moderate range of temperatures.  Where would the energy go?

Conceptually, for breeders vs once through, would it be a question of energy for the reprocessing versus the energy for mining, fuel processing (not reprocessing) and waste storage for the once throughs?

That's what it looks like to me.

Three things I noticed:

1. The TAMU process isn't really suited for recycling LWR fuel as LWR fuel, as re-enrichment would be required.
2. If it's a simple matter to separate the FPs from U/Tu using the nitric acid process, and the U/Tu can be fluorinated and most of the U drawn off leaving a U/Pu/Am/Cm mix, you could turn used LWR fuel into FBR driver fuel plus a breeding material stream in just 4 steps.
3. The breeding material stream is likely well-suited for re-enrichment, as it would already be chemically converted to UF6.  This would net you perhaps 14% of your net uranium requirements for LWRs, with all the tails left as breeding material.  No waste other than FPs.

Here's something I found from the CBO:

www.cbo.gov/sites/default/files/cbofiles/ftpdocs/88xx/doc8808/11-14-nuclearfuel.pdf

[huon]

Hi, Gregory--welcome to the site. I'm afraid I lack the technical expertise to discuss this matter directly. But you might have a look at this thread in the BNC Blog Post Comments section:

EROEI and the IFR
bravenewclimate.proboards.com/thread/290/eroei-ifr

Apparently Barry Brook came up with a figure of around 900!

[gregory]

Thanks.


I did read the article, EP, and it did seem pretty energy light, in comparison to electrorefining, but that's just how it "seemed" to me and I don't trust my intuitions in this area.

But I trust your intuitions so thanks.


and I do recall not, the Barry number from the old days.


I have read higher numbers for a German designed dual fuel reactor.  But many of the improvements in EROI were largely independent of the fuel.

[gregory]

thanks EP: that doc on reprocessing assumes one additional pass through, not full reprocessing.

[Roger Clifton]

May 20, 2020 2:35:33 GMT 9.5 Gregory Meyerson said:

the impact of, say, Integral Fast Reactors or LFTRs on EROI for nuclear.

Welcome back, Greg. I guess you been hovering near us in cyberspace, ghostlike for the last 10 years.

What you mean by EROI? Energy sold compared to dollars invested? The business plan for new reactors use a figure in $/MWh, which includes the amortization of all capital equipment, and probably the cost of decommission 40 years later at the end of the loan period for the original capital. We see ballpark figures of 100 $/MWh for new reactor plans, but when the lifetime of a 40-year old reactor is extended for another 20 years or so, many of those costs have already been paid off and the forward estimate of $/MWh plunges.

Do you mean "fissionables recovered on fissionables consumed"? This is the breeding ratio. The time base has to be stated. In an average fission of U235, one neutron must be consumed to maintain criticality, leaving a maximum of 1.5 neutrons available for breeding, and heavier isotopes produce more neutrons. Subsequently, bred isotopes are themselves fissioned and breed further fuel. If losses are kept low enough, the breeding can continue indefinitely while fertile isotopes are available. In the literature an unstated time base is usually a single fuel loading cycle – usually three years for a PWR. The "doubling time" is more useful for bean counting as it explicitly states the number of years that a particular reactor family would take to double their fissile inventory.

Wikipedia gives a remarkable(*) figure of 0.6 for the breeding ratio of an LWR, and an extreme figure of 2.5 for a experimental fast reactor. Here they are including Pu240, which is only "fissile" in a fast neutron reactor – not slow neutron reactors like LWR. Consequently its economic value is only realised when there is a demand for fuel for fast neutron reactors. Sentimentally, many of us are inclined to the idea that that all of the actinides put into a reactor should be burnt in a reactor, using reprocessing, perhaps on-site as in the IFR concept. However, the bean counter will always intrude. Enrichment processes have improved to the point where it may always be cheaper to top up a fast reactor with fresh enriched uranium than recycle the mess of fissiles from old fuel.

However recycled fuel still has a potential market as start-up fuel for fast reactors, because a fast reactor requires more a lot more fissiles in the core to attain and maintain criticality than the slow reactors. Because China plans to expand its power generation from fossil fuels and slow neutron reactors into fast reactors, the accelerating rate of startups will create a demand for recycled fissiles. However, they are likely to recycle their own old slow reactor fuel before they would buy internationally.

(*) An LWR could be said to have a BR of ~0.6 if its fuel started with 3.5% U235 and ended up with 1% U235 plus 1% Pu. Sometimes the calculation includes the fuel which is both bred and burnt during a fuel cycle. In a breeder reactor it would make more sense to talk in terms of doubling time. Doubling time is a rate, so a DT of 200 years would indicate a poor breeder rather than a long-lived reactor.

[David B. Benson]

A Forecast for the Commercial Future of GEN IV Reactors ~ Three Types Have a 50/50 Chance of Success
2020 Feb 07
Energy Central
energycentral.com/c/ec/forecast-future-gen-iv-reactors-5050-chance-success-three-types

EROEI isn't directly mentioned in this long article, just the $$ it takes. The current thinking is that $60/MWh is required to break even. But in my opinion half that is required to successfully compete.

So the article then continues with the idea that reactors make heat. Hot enough for process heat probably has a good market.

[Gregory Meyerson]

Thanks David.  That's a sobering article for sure.


Roger, I didn't know where you guys went.  I found the site reading something at Rod Adams blog on the Moore film.


On EP's reprocessing link, Bill Sacks and I asked Yoon Chang about it and asked his aqueous chemistry experts and they said this: (I was googling away, looking up stuff like group actinide extraction process)



The general approach is not new and relies on careful control of the oxidation state (6+) of the minor actinides (Np, Am) during the process. Two of our aqueous chemistry experts did a quick review of the paper. Their comments are provided below.



· Very interesting laboratory study and results, but application of this approach for treating spent fuel will be very challenging

· Management of oxidation states mainly for Np(VI) and Am(VI) will become very problematic with scale-up

· Maintaining Am(VI) under strong radiation conditions might be another challenge

· Any residual TBP or other organics from the GANEX process would bring additional challenges to maintaining Am(VI)

· Scale-up of crystallization process is very challenging, where simple operations such as washing are not as effective

· The paper indicates that it is difficult keeping Am(VI) in small scale experiments, it will be even more difficult at larger scales

· Marginal if any cost improvement because of the batch nature of the process

[Roger Clifton]

May 20, 2020 2:35:33 GMT 9.5 Gregory Meyerson said:

impact of, say, Integral Fast Reactors or LFTRs on EROI for nuclear

The book, "Plentiful Energy " analyses the various costs of recycled versus once-through fuel, comparing the IFR breeder with a typical LWR slow reactor. See pages 280-294. Cost of fuel in any nuclear power bill is trivial, less than a cent per kWh.

I am deeply suspicious of the word "energy" in seemingly innocent EROI calculations used by renewables fanatics to claim cost efficiency for their toys. However their "energy" is only comparable to the energy-on-demand of the system in which it is parasitic while it injects a negligible contribution to the power on the grid. Then it is only a minor irritation to steam generators as a minor loss of electricity sold. When the intermittent energy becomes a significant fraction of the generation on the grid, the costs increase to the major generators, to level out the intermittency and to the grid operator to pay the major generators for the extra spinning reserve required to balance it. The fanatic counts these costs as "externals" and excludes them from the EROI calculation.

Such people would do less damage to the community if they dedicated themselves to selling magic potions to the terminally ill.