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PostPosted: Aug 28, 2015 6:21 pm 
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I've just sent off a paper (see below) which points out that a properly implemented "nuclear renaissance" should be able to reverse the effects of Mankind's "industrial age" CO2 dumping. Both of the reactors recommended for tackling both this and other problems are isobreeding MSRs - one which "burns" thorium and one which "burns" depleted uranium. The paper describing both of them hasn't been submitted to any journal yet because I haven't yet managed to get anyone to perform the "simple" calculations required to replace its hypothetical Figure 9 with one that's based upon up-to-date neutronics calculations & data. That "draft" paper will be ATTACHED to the second posting in this topic.

Please look them over and give me your opinions.


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CO2 basalt scrubbing paper.doc [199 KiB]
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PostPosted: Aug 28, 2015 6:23 pm 
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Here's the other paper.


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MCFR & MSFR paper-23Aug15.doc [1.23 MiB]
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PostPosted: Aug 28, 2015 7:16 pm 
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The basalt dissolution is certainly interesting - but I am not convinced that it is actually required to use breeder reactors for this mechanism to work.
Seawater uranium has, I think, destroyed any chance of any kind of fuel reprocessing becoming cost effective in the medium and possibly even long term.
The numbers look just as good with a simple DMSR cycle that avoids many of the issues with a breeder cycle - indeed even a high converting LWR like an ESBWR could manage 600GWe indefinitely with only a very small amount of uranium consumption. (35% efficient, 50GWd 4.2% fuel gives us a consumption of 12510 tonnes of enriched fuel per year, which translates to something like 86,000t of natural uranium).

86,000t of natural uranium could be provided by the sea for centuries without even significantly depleting the resource.
And in a glorious nuclear future you could expect carbon dioxide production to fall precipitously thanks to electrification (or district heat) crushing every other energy market of note apart from maybe aviation.


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PostPosted: Aug 28, 2015 7:42 pm 
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E Ireland wrote:
...The numbers look just as good with a simple DMSR cycle that avoids many of the issues with a breeder cycle - indeed even a high converting LWR like an ESBWR could manage 600GWe indefinitely with only a very small amount of uranium consumption. (35% efficient, 50GWd 4.2% fuel gives us a consumption of 12510 tonnes of enriched fuel per year, which translates to something like 86,000t of natural uranium)..
.


Which of the "numbers" looks just as good - please be specific.

Most of the DMSR-based schemes that I've been privy to just keep on kicking the waste (& reprocessing) problem down the road. It's time to get serious about implementing a genuinely sustainable nuclear fuel cycle - not just another "temporary" fix..

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PostPosted: Aug 29, 2015 3:31 am 
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Uranium consumption with a DMSR is still so small it basically doesn't matter - whilst waste volume is greater it is still tiny.

Fluorination to remove Uranium is probably worth it but the rest should probably go straight into a glass form.

It might be a "temporary" fix - but in this case the temporary is a matter of millennia, and I think I can live with that.


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PostPosted: Aug 30, 2015 6:41 am 
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Spent DMSR salt (if this is the MSR fueled future) is almost all either glass forming material (lithium borosilicate glass is still a glass) or fission products anyway.
There is only a very limited amount of plutonium and neptunium in the salt - and former of which is of terrble isotopic quality.

Meanwhile solid fuel reprocessing is now so expensive that you could pay for twelve to fifteen centuries of dry storage for the cost.


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PostPosted: Sep 03, 2015 3:09 am 
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E Ireland wrote:
Meanwhile solid fuel reprocessing is now so expensive that you could pay for twelve to fifteen centuries of dry storage for the cost.
I presume you mean solid oxide fuel into solid oxide fuel?

Seems pyro-type processing into fluoride fuels would be a whole lot cheaper.

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PostPosted: Sep 03, 2015 6:40 am 
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Really?
It still has multiple chemical operations on insanely radioactive fuels.
Meanwhile high burnup spent fuel turns out to not produce that much useful material as it is.


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PostPosted: Sep 03, 2015 10:31 am 
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My argument for the MCFR isobreeder described in the second paper ATTACHED in this topic is keyed to the CR vs reprocessing rate plot depicted in its Fig 9. Unfortunately that plot is "hypothetical" since the blanket less "breeder" in question apparently hasn't ever been modeled before (or if it was, described in a way that GOOGLEing recognizes). So far none of the "real" NEs I've asked to do so has volunteered to calculate/prepare a real plot so I've decided to try to ball park it myself (see below & the latest ATTACHMENT). If anyone who's following this post is qualified to render an opinion (is a real NE or equivalent) about my effort please pitch in & do so.

Please see the ATTACHED spreadsheet (it's really short & simple).

I started out by digging up an old (1968) paper that assigned actual numbers to the fission and n,gamma cross sections of 239Pu plus the sum of its FP's n,gamma cross sections in a generic "fast reactor". It turns out that natural platinum behaves about the same as does that sum. It and other papers written back during the heyday of reactor development/testing (and primitive computers), also indicated that the mean neutron capture cross sections of the FP in such a reactor don't vary much with neutron exposure.

Next, assuming that the relevant measure of "amount of fission product build up" would be its molar (or atomic) concentration relative to that of 239Pu and that 239Pu represents 6 mole% of the fuel salt (consistent with some of the MCFR salt recipes I've seen), I did some calculations of the net number of neutrons left for fissile breeding with various FP build ups & three different degrees of salt + structure n,gamma neutron losses. For those calcs, the average number of neutrons generated per 239Pu fission assumed was 2.5 which is consistent with a fairly but not super fast spectrum.

The plot at the bottom of the spreadsheet gives the results. They seem to support my contention that it should not be necessary to assume that achieving "break even" with a blanketless MCFR would require lots of reprocessing.

Would you please look it over & tell me if I've made any logic boo boos. Don't forget I don't need exact numbers to support the paper's contentions - I'm/we're not trying to actually design something to be built as-is.


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MCFR CR vs reprocessing rate ballparking.xls [477 KiB]
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PostPosted: Sep 03, 2015 5:17 pm 
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Nature's editors decided that my description of a potentially viable way of reversing the effects of anthropogenic CO2 did not "represent a development of sufficient scientific impact..." for them to consider any further.

Since lots of people in the geoengineering & oceanic acidification science fields have already seen it (I sent to several of the lead authors of the papers in its literature citations for review), I wouldn't be too surprised to have somebody else "invent" the same concept pretty darn soon. (The same thing happened to me during my "assistant professor" days at Marquette U).

This renders the immediate resubmission to another journal pretty important. I've made a few changes in it (ATTACHED) & would really appreciate hearing from you ASAP.

Don't be shy.


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CO2 basalt paper post Nature rejection.doc [613 KiB]
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PostPosted: Sep 03, 2015 5:30 pm 
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I've found/corrected a few boo boos. Updated version ATTACHED.


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CO2 basalt paper post Nature rejection.doc [613.5 KiB]
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PostPosted: Sep 05, 2015 2:33 am 
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E Ireland wrote:
Really?
It still has multiple chemical operations on insanely radioactive fuels.
Meanwhile high burnup spent fuel turns out to not produce that much useful material as it is.

It has EASY chemical operations (oxides to fluorides) just like PUREX starts with but doesn't have to undergo the DIFFICULT reverse fluoride to oxide steps. And it doesn't have to involve aqueous activities which create large amounts of secondary wastes.

High burnup is still mostly unused fuel at the end of its useful life. Unless you mean specialty solid fuel reactors like the navy units that start off with very highly enriched fuels and run for several decades rather than several years.

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PostPosted: Sep 05, 2015 4:33 am 
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The only thing available in quantity in spent fuel is 238U.
Modern spent fuels contain little useful plutonium and a 235U enrichment similar to or worse than Natural Uranium.

We are not short of either natural uranium or depleted uranium - there is little need to go to spent fuel for it.
You need U prices several times reprocessing prices per kg to make it even close to worthwhile


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PostPosted: Sep 08, 2015 6:18 am 
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238U and 232Th are the fertile isotopes available in plenty. However, the fissile materials are available in quantity with the US, Russia, UK and France and small quantities with some other countries.
http://www.fissilematerials.org/ thtFor energy security of the world, the fissile rich should breed the fissile and help rest of the world with nuclear fuel. Unfortunately only Russia and less endowed China and India are continuing with breeder reactors and the US is discouraging others from proceeding with the technology.
MSR is synergistic with pyro-processing involving Chloride/Fluoride volatility and is preferable for breeders.


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PostPosted: Sep 08, 2015 1:23 pm 
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I've decided to resubmit the again-improved revision to Nature. Here it is.


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CO2 basalt paper rewrite.doc [667 KiB]
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