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Post by eclipse on Feb 5, 2015 15:59:54 GMT 9.5
Hi all I've tried to demonstrate on The Conversation that IFR's burn today's actinides for centuries of clean energy and eventually leave fission products that don't last as long. But I think my rival on The Conversation has confused which fission products are short and which are long lived. Does anyone have conclusive statements from authority figures that show how short lived final waste products are? Apparently the Chief Scientist of the UK David Mackay is not enough!
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Post by jagdish on Feb 6, 2015 8:01:21 GMT 9.5
There are some fission products like Technesium which are long lived. The important fact is that the present generation of thermal reactors use only 1% of mined uranium or not more than 5% of enriched fuel and have large amount used fuel 20-100 times the fission products. Some of the fission products could be otherwise useful. The fission products could be easily disposed off in deep boreholes. The fast reactors and the IFR make the waste problem really manageable.
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Post by David B. Benson on Feb 6, 2015 12:04:24 GMT 9.5
There is very little Technetium and it is a medically useful isotope; possibly worth separating. The majority of the actual wastes is Ce-137 www.geigercounter.org/radioactivity/isotopes.htmwith a short enough half live that isolation for 300 years suffices. However, the waste separation methods are not perfect; currently, eventually almost half of the actinides end up in the waste stream. Without further processing such a waste stream would require long term isolation. I suggest a salt dome as ideal. Note that is almost half of all the actinides, including natural and depleted uranium; this is a huge reserve.
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peterc
Thermal Neutron
Posts: 30
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Post by peterc on Feb 6, 2015 16:04:10 GMT 9.5
Hi eclipse - There's one thing I hope I've understood correctly (and I'd be only too happy to be put right in the negative case) is the relationship between half-life and activity: namely the longer the half-life, the lower the activity. The very long life stuff has such a low activity that it's sometimes less than that of the original uranium when it was dug out of the ground. The objections to burying it are then in my mind, completely spurious.
The problem with radiation nowadays is that it's detectable at extremely low levels, levels which are completely negligible for any human cause. Mind you, the same is happening now with certain elements and compounds, which, if you use sensitive enough methods can be found everywhere. More grist to the mill of the neurotic-tendency.
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Post by Ed Leaver on Feb 17, 2015 23:44:08 GMT 9.5
There is no "definitive proof" because no IFR has ever been built and its pyroprocessing fuel recycling facility evaluated in production environment. And the reason(s) an IFR has never been built are (1) "But what if it doesn't work?What'll we do with all the waste?" and (2) "What if it does work? What'll we do with all our wind and fracked gas?" Tough questions. For those of you with time on your hands, a fascinating little read is Actinide and Fission Product Partitioning and Transmutation Eleventh Information Exchange Meeting, San Francisco, California, USA 1-4 November 2010. In particular see B. Petrovic, M. Carelli, F. Franceschini, Ed Lahoda Requirements-driven comprehensive approach to fuel cycle back-end optimisation on page 85, and their figures 3 and 4 on pages 89 and 91. Their Figure 3 looks similar to one in M. Salvatores' Advanced Nuclear Fuel Cycles: That long purple low-level tail for the Fission Products is due mostly to Technetium-99 and Iodine-129. This figure only illustrates the time-scales involved for the different classes of decay products, not what can be achieved in production environment. Basically, if you can eliminate all Pu from the waste stream, your radiotoxic lifetime is the ~10,000 years of the Minor Actinides. If you can fission or transmute them as well, then the RT lifetime is about 300 - 500 years of the Fission Products: 0.1% MA leakage to waste stream gives about 400 years, 0.2% MA leakage 1000 years, 1.0% leakage 10,000 years. The question is, how much of the Pu and MA can you actually eliminate in practice? There isn't much actual practice to go on. David Benson suggests Australia play it safe and prepare for a worst-case few hundred thousand years, to avoid over-selling the product. Actually build an IFR and operate it for a few decades or a century and find out. You'll get the same reduction in waste volume, and same amount of useful clean energy either way. That M. Salvatores link above gives a good overview, and briefly mentions the sort of regional reprocessing and sequestration business now being discussed in Australia.. Does anyone know what the BN1200 back-end will look like?
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Post by eclipse on Feb 18, 2015 5:38:03 GMT 9.5
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Post by Ed Leaver on Feb 18, 2015 10:39:18 GMT 9.5
Thanks for the BN800 link, Eclipse. I wish it did go into more detail on BN800 fuel cycle, but it is a start. Do try to wade through the M. Salvatores presentation linked above, its a bit more accessible than the Petrovic et al. article, and is probably directly relevant to BN800 and BN1200. Your RT article mentions only "nitric acid" and "plutonium extraction", suggesting the fuel cycle is of the extended PUREX variety being developed by France. It doesn't mention the disposition of the Minor Actinides. Perhaps Russia intends to recycle the energy-rich stuff (Plutonium-Uranium) first, and save the other actinides for a rainy day.
My understanding is current European research is largely focused on oxide and nitride fuels, and their extended wet Purex - type recycle processes. This is largely driven by France as they have the world's 2nd largest fleet of LWRs to feed and look after. But BN800 is pretty flexible and can burn metal fuel as well, should anyone again take dry pyroprocesing seriously.
In 2010 GE-Hitachi inquired the US NRC of the feasibility of licensing their S-PRISM IFR, and submitted a 508 page overview document in support. NRC's reply:
Mr. Head resubmitted his inquiry one year later, and received an identical reply. Taking the hint, GE-H then focused their efforts on getting their large 1.6 GW ESBWR NRC certified. This was successfully completed last fall.
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Post by eclipse on Feb 18, 2015 10:53:52 GMT 9.5
Don't you just love political double-speak when they want to shift responsibility? Even the writing is often passive voice, like there's no actual people in there making any decisions or doing anything. It's all been decided for them and done to them. It's all so passive-aggressive.
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Post by Ed Leaver on Feb 18, 2015 19:07:28 GMT 9.5
I stand corrected. According to WNA's Processing of Used Nuclear Fuel (see section "Electrometallurgical 'pyroprocessing'") BN-800 does indeed use a pyroprocessing fuel recycle with similar properties to those being developed by South Korea - US DoE, and by GE-Hitachi. IOW, BN-800 fuel cycle keeps all the MA together with the Plutonium, and this radiologically hot mix is blended with some of the recovered uranium to fabricate new MOX fuel pellets. It differs from GE-H PRISM because of the radical differences between MOX and metal fuels. But for a closed fuel cycle, the overall idea is the same. The WNA article doesn't mention BN-800's production MA loss to waste, possibly because BN-800's have just been completed. The Korea / U.S. KAERI "hopes the project will be expanded to engineering scale by 2012, leading to the first stage of a Korea Advanced Pyroprocessing Facility (KAPF) starting in 2016 and becoming a commercial-scale demonstration plant in 2025," but we'll have to look further for details of the Korean FR program.
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Post by David B. Benson on Feb 19, 2015 11:58:06 GMT 9.5
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Post by cyrilr on Mar 12, 2015 2:40:09 GMT 9.5
It is important to understand the difference between ingestive toxicity and actual risk. It is not likely that people will eat spent fuel, cladding or vitrified wastes, just as it isn't likely that people look at a piece of glass or granite and think "yum chow-chow". When you look at the actual risk it is based on gamma dose. I've looked at this and it is basically safe to stand next to a PWR spent fuel assembly after about 500 years. Please see the following discussion for more: www.energyfromthorium.com/forum/viewtopic.php?f=51&t=4543
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