Moreno Posted January 27, 2018 Posted January 27, 2018 How safe are fast reactors in comparison to common water-cooled? Why nobody (except Russia and India) want to build them? There seem to be huge amount of fuel for them which is essentially free - Plutonium, Uranium 232, Thorium and thousand of tons of dangerous nuclear waste. All this could be efficiently burned in fast reactors with few nuclear waste remaining. What about gas-cooled fast reactors in particular? Why these reactors are so unpopular?
Moontanman Posted January 27, 2018 Posted January 27, 2018 6 minutes ago, Moreno said: How safe are fast reactors in comparison to common water-cooled? Why nobody (except Russia and India) want to build them? There seem to be huge amount of fuel for them which is essentially free - Plutonium, Uranium 232, Thorium and thousand of tons of dangerous nuclear waste. All this could be efficiently burned in fast reactors with few nuclear waste remaining. What about gas-cooled fast reactors in particular? Why these reactors are so unpopular? I'm pretty sure France uses them as well. Their lack of popularity at least in some respects, has to do with them not being good at producing weapons grade material... 2
Moreno Posted January 28, 2018 Author Posted January 28, 2018 1 minute ago, Moontanman said: I'm pretty sure France uses them as well. Their lack of popularity at least in some respects, has to do with them not being good at producing weapons grade material... It seems some countries have more Plutonium they need. For example UK. https://www.theguardian.com/environment/2012/feb/02/nuclear-reactors-consume-radioactive-waste France only experimented with them. They had sodium-cooled fast reactor but turned it down for persistent accidents. Now they continue small-scale experiments with few types of fast reactors. Japan is exactly the same story. The only full-power operational fast reactor is in Russia. This one is a sodium-cooled, but Russia plans to develop lead-cooled reactors. Gas cooled rectors don't suppose to have the same problems, because in difference from sodium helium is an inert one.
OldChemE Posted January 28, 2018 Posted January 28, 2018 I've been out of this aspect of the field for way over a decade, so this is pretty general. Thermal reactors are set up such that the immediately released (Fast) neutrons from fission are themselves not sufficient to maintain the chain reaction-- the neutrons released in a slower time frame are necessary. This makes them somewhat forgiving from a control standpoint. Fast reactors do not have this somewhat forgiving time lag in the chain reaction-- making them less popular from a design standpoint. And-- they use coolants, such as liquid sodium, that are a lot more difficult to work with than water or graphite. The combination of control complexity and materials difficulties made the fast reactors less popular. Technology has been changing so I may be out of date. Back in the 60's and 70's the US (Via Admiral Rickover's organization) actually built and successfully operated a thermal breeder reactor at the Shippingport power plant which converted Thorium into usable nuclear fuel. But, as I recall, the breeding ration was very slim (something like 1.05). The advantage was that thorium is very plentiful, but it was never pursued because fast breeders (on paper at least) had much better conversion ratios. For an interesting perspective on fast reactors you should search for a very old science fiction story called "Blowups Happen" written, I think, by Robert Heinlein. It described an accident at a fast reactor, predicated on the assumption that, if you don't design for the slow (thermal) neutrons to maintain criticality, things can get out of control very fast. 1
Moreno Posted January 28, 2018 Author Posted January 28, 2018 55 minutes ago, OldChemE said: I've been out of this aspect of the field for way over a decade, so this is pretty general. Thermal reactors are set up such that the immediately released (Fast) neutrons from fission are themselves not sufficient to maintain the chain reaction-- the neutrons released in a slower time frame are necessary. This makes them somewhat forgiving from a control standpoint. Fast reactors do not have this somewhat forgiving time lag in the chain reaction-- making them less popular from a design standpoint. If chain reaction is their regular mode, what can happen even worse than that? How runaway can happen?
OldChemE Posted January 28, 2018 Posted January 28, 2018 Its primarily a timing thing. In a fast reactor, the fuel used readily fissions with high energy neutrons ("fast" neutrons). This is a very fast process. In a thermal reactor, the fissile material is chosen that fissions best with lower energy neutrons ("Slow" neutrons). The moderator (water or graphite) is used to slow the neutrons down to where they will cause fission. The slowdown process creates a time lag in the chain reaction which aids control. In addition, most thermal reactors that use a water moderator are designed so that the expansion of the water moderator as it heats reduces the water density just enough to become less effective at slowing the neutrons. This gives the reactor a negative temperature coefficient-- that is, excessive energy production acts to reduce energy production. The overall effect is that thermal reactors react less quickly to power excursions-- which is a control benefit. Fast reactors, by comparison, do not need a moderator and respond much more quickly to reactivity changes. Its really a trade-off. Thermal reactors are easier (less costly) to build and operate but don't do well at breeding, while fast reactors breed much better but have greater challenges in technology and materials.
Moreno Posted January 28, 2018 Author Posted January 28, 2018 How good are heavy water thermal reactors at burning Thorium or Uranium 232? What are issues behind them aside heavy water price?
studiot Posted January 28, 2018 Posted January 28, 2018 (edited) The UK Dounreay reactor was the worlds first and only fully successful breeder reactor which operated from 1955 to 1977, until the UK government got cold feet. It supplied national grid power and added an huge boost to the local economy in a previously poor area. https://www.google.co.uk/search?q=History+of+Dounreay+reactor&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&dcr=0&ei=SaFtWvLTE7TP8AfMmovIAw I remember at school being taught how the availability of cheap electricity enabled the aluminium smelting industry to develop in Scotland, but that's also gone now. And thanks to OldChemE for sharing his knowledge of the subject, including facts I didn't know. +1 Edited January 28, 2018 by studiot
swansont Posted January 28, 2018 Posted January 28, 2018 10 hours ago, OldChemE said: The slowdown process creates a time lag in the chain reaction which aids control. Most of this time lag comes because a small fraction of the neutrons comes from neutron emission after beta decay of fission products (delayed neutrons), which takes a several tens of milliseconds, on average. Thermalization takes a few tens of microseconds. A reactor critical on prompt neutrons alone is not controllable.
OldChemE Posted January 30, 2018 Posted January 30, 2018 On 1/28/2018 at 6:24 AM, swansont said: Most of this time lag comes because a small fraction of the neutrons comes from neutron emission after beta decay of fission products (delayed neutrons), which takes a several tens of milliseconds, on average. Thermalization takes a few tens of microseconds. A reactor critical on prompt neutrons alone is not controllable. Wish I had thought to say that. Good point
Raider5678 Posted January 30, 2018 Posted January 30, 2018 (edited) On 1/27/2018 at 7:07 PM, Moreno said: It seems some countries have more Plutonium they need. For example UK. The entire world has a shortage of Plutonium. http://www.businessinsider.com/nasa-nuclear-battery-plutonium-238-production-shortage-2017-8 At least that particular type. Edited January 30, 2018 by Raider5678
Moreno Posted March 19, 2018 Author Posted March 19, 2018 (edited) What do you think about particle accelerator driven Thorium reactors? They seem require no Uranium or Plutonium, subcritical (no threat of meltdown) and can burn lot of radioactive waste. It is claimed accelerators with required parameters are on the verge of development. https://phys.org/news/2011-06-pint-sized-particle-nuclear-energy.html https://en.wikipedia.org/wiki/Accelerator-driven_subcritical_reactor http://large.stanford.edu/courses/2013/ph241/baxevanis1/ Edited March 19, 2018 by Moreno 1
Outrider Posted March 20, 2018 Posted March 20, 2018 Turns out Russia has what is described by Wiki as a sodium cooled fast breeder reactor know as the BN-800. It has been producing commercial power since November of 2016. It runs on a plutonium and uranium mix. Weapons grade if the article is accurate and I'm not missing something. https://en.m.wikipedia.org/wiki/BN-800_reactor Quote The reactor core is, in size and mechanical properties, very similar to the BN-600 reactorcore, but the fuel composition is very different. While BN-600 uses medium-enriched uranium dioxide, this plant burns mixed uranium-plutonium fuel,[2] helping to reduce the weapon-grade plutonium stockpile and provide information about the functioning of the closed uranium-plutonium fuel cycle. It was highlighted that the closed cycle will not require plutonium separation or other chemical processing. I have been hearing thorium quite a bit lately and what little bit I have read about it seems very promising. Inda seems poised to make it a reality. http://www.indrastra.com/2017/09/India-s-Tryst-with-Next-Gen-Nuclear-Energy-Systems-003-09-2017-0008.html?m=1 Quote The Indian nuclear establishment is reportedlyin the final throes of developing a (conceptual)design for Advanced Heavy Water Reactor (AHWR), a Technology Demonstrator Reactor of 300 MW, as the stepping stone to the third stage of India’s three-stage nuclear energy program. In December 2016, Government of India is known to have accorded in-principle approval for the Tarapur Maharashtra Site (TMS) for locating the 300MW AHWR. Meanwhile, the 500MW Prototype Fast Breeder Reactor (PFBR) at Kalpakkam, under construction for several years, is now scheduled to be commissionedtowards the end of this year. These two developments (PFBR and AHWR) as they mature would herald the era of next-generation reactor systems in India. More importantly, India would be the first country, after Russia, to bring online a commercial fast-breeder reactor. Really guys I am much more comfortable with windmills and solar panels but with things the way they are all options need to be on the table.
Moreno Posted March 26, 2018 Author Posted March 26, 2018 (edited) On 3/19/2018 at 8:43 PM, Outrider said: Really guys I am much more comfortable with windmills and solar panels Why exactly? Edited March 26, 2018 by Moreno
swansont Posted March 27, 2018 Posted March 27, 2018 11 hours ago, Moreno said: Why exactly? Not having to clean up after a solar or wind spill, perhaps? 1
Moreno Posted March 28, 2018 Author Posted March 28, 2018 On 3/27/2018 at 5:53 AM, swansont said: Not having to clean up after a solar or wind spill, perhaps? Do you think all possible nuclear reactor concepts are that much inherently unsafe? What about subcritical reactors? Can there be an all-solid state reactors?
swansont Posted March 28, 2018 Posted March 28, 2018 6 minutes ago, Moreno said: Do you think all possible nuclear reactor concepts are that much inherently unsafe? I don't think that has anything to do with it. "Inherently safe" does not mean "foolproof" or "without potential problems" 6 minutes ago, Moreno said: What about subcritical reactors? What about them? Do they make fission products with half lives longer than a few years? If yes, then there are potential issues with waste and contamination. 6 minutes ago, Moreno said: Can there be an all-solid state reactors? How would that work? Solid-state refers to atom-level interactions. Fission is nuclear.
Moreno Posted March 28, 2018 Author Posted March 28, 2018 5 hours ago, swansont said: I don't think that has anything to do with it. "Inherently safe" does not mean "foolproof" or "without potential problems" What about them? Do they make fission products with half lives longer than a few years? If yes, then there are potential issues with waste and contamination. How would that work? Solid-state refers to atom-level interactions. Fission is nuclear. The spills, waste and contamination are typically associated with liquid or gaseous substances. If there are solid state substances in the reactor only, with only microscopic amounts of some radioactive gases present, how a dangerous spill can occur?
studiot Posted March 28, 2018 Posted March 28, 2018 (edited) 45 minutes ago, Moreno said: The spills, waste and contamination are typically associated with liquid or gaseous substances. If there are solid state substances in the reactor only, with only microscopic amounts of some radioactive gases present, how a dangerous spill can occur? Jammed moderator rods / broken/faulty rod control mechanism. Fluids are used to cool a reactor, how would solid state cooling work? Fluids are also needed to transfer heat to the generating plant. Without this transfer what would be the point of the reactor? Edited March 28, 2018 by studiot
Moreno Posted March 28, 2018 Author Posted March 28, 2018 1 hour ago, studiot said: Jammed moderator rods / broken/faulty rod control mechanism. Fluids are used to cool a reactor, how would solid state cooling work? Fluids are also needed to transfer heat to the generating plant. Without this transfer what would be the point of the reactor? 1) I'm not sure exactly, but accelerator driven and LFTR reactors may not require control rods. 2) Helium can be used to cool reactors. It can't get radioactive. To create danger of contamination outside the plant, liquids need to be lightweight enough and vaporize easily to leak outside power plant. It may not be the case if molten lead or molten salts are used as a coolants. They are heavy and viscose and even if they will leak out the reactor core it's doubtful they will get far and contaminate area outside power plant. 3) I think an attempt to create a reactor without any liquid or gaseous coolant can be made. For example, reactor core can be bricked by boron-10 from inside, maybe in the borosilicate glass form. When Boron-10 captures neutron it converts to Lithium and radiates a proton. Proton radiation can be easily converted to electricity with help of an electrostatic energy converter. This method is already used in some isotopic energy converters.
studiot Posted March 28, 2018 Posted March 28, 2018 14 minutes ago, Moreno said: 1) I'm not sure exactly, but accelerator driven and LFTR reactors may not require control rods. You demand some sort of solid state reactor then offer me a liquid fluoride one ??????????????? or a gaseous helium one? 1
Moreno Posted March 28, 2018 Author Posted March 28, 2018 43 minutes ago, studiot said: You demand some sort of solid state reactor then offer me a liquid fluoride one ??????????????? or a gaseous helium one? I just suggested different possibilities.
Outrider Posted March 28, 2018 Posted March 28, 2018 On 3/27/2018 at 4:53 AM, swansont said: Not having to clean up after a solar or wind spill, perhaps? Yes or close enough at least. I was thinking along the lines of Chernobyl with its 1,000 or so square miles that can't be cleaned up at least by us. Thank you! On 3/19/2018 at 7:43 PM, Outrider said: Really guys I am much more comfortable with windmills and solar panels but with things the way they are all options need to be on the table. On 3/26/2018 at 5:13 PM, Moreno said: Why exactly? Nuclear reactors are high reward/high risk operations. High reward because the energy generated is very clean (disregarding spent fuel*) and practically "free" for us and I mean free in the renewable sense. That is if everything works properly. High risk because if something does go wrong you will almost certainly have killed most of the people in the plant and possibly many persons, plants and animals in the surrounding area. Also in worse case scenario you might have made 100's of miles of viable land uninhabitable by us and most other organisms. *This is why I was interested in your thread. Fast breeders promise to use up that spent fuel and leave very little behind. That is if I am understanding what I have read and it is true. I am not exactly trusting of power companies. BTW I am sitting within 50 miles of a conventional nuclear plant right now. So my concerns are very personal. 10 hours ago, Moreno said: Do you think all possible nuclear reactor concepts are that much inherently unsafe? So what level of saftey are you comfortable with? You cannot mitigate all the danger away which is why I would prefer to do without entirely but now the whole globe is in danger so we need to find what is best and do it quickly. Look I'm a bit on the fence regarding the consequences of climate change (but not of AGW itself) but we have run out of time we need to work out solutions now. Besides there are many upsides to clean energy and only one downside I can think of and that is we have to invest in new infrastructure. Also I think all your talk of theoretical reactors is muddying the waters. We need something now. 10 hours ago, Moreno said: Can there be an all-solid state reactors? 1. Can you show me one? 2. Isn't this a bit off topic in a thread titled "Fast breeder reactors"?
Moreno Posted March 28, 2018 Author Posted March 28, 2018 (edited) I think that at the present and near future level of technology solar and wind power can be regarded only as a supplemental type of power generation only. First of all, Sun and wind are intermittent and if more than 50% of power will be generated in this way, this intermittence may lead to an unpredictable, possibly even catastrophic consequences. Secondly, it requires too much expensive and sometimes rare materials. A typical nuclear power plant has 1 GWt output. Usually it includes a few nuclear reactors. And here is the size of a wind turbine which allows to generate just 10 MW of energy. And you will need to build at least 100 of those monsters to provide 1 GWt. But wind practically never blows all the time with the same strength, so this number will unavoidably grow to at least 200. Possibly even more. And each of this monsters requires tons of copper and neodymium for electric motors, hundreds of tons of aluminum and high grade stainless steel, etc. Some of this materials aren't particularly common. The price of this enterprise will unavoidably start to grow exponentially when all the World will start to build them on mass scale. Edited March 28, 2018 by Moreno
Outrider Posted March 29, 2018 Posted March 29, 2018 (edited) So the topic now is why wind turbines won't work? 3 hours ago, Moreno said: I think that at the present and near future level of technology solar and wind power can be regarded only as a supplemental type of power generation only. No one is proposing that we use only one type of power source. These technologies are working and will work better in the future. 3 hours ago, Moreno said: And each of this monsters requires tons of copper and neodymium for electric motors, hundreds of tons of aluminum and high grade stainless steel, etc. Some of this materials aren't particularly common. The price of this enterprise will unavoidably start to grow exponentially when all the World will start to build them on mass scale. This is just propaganda. Enercon's E-126 in Germany runs entirely without neodymium and has been running that way since 2011. As far as copper, aluminum and stainless steel I'm willing to wager that nuclear power sources use more per kilowatt. See with the turbines (once construction is complete) there is nothing to mine, refine, transport or dispose. If your going to compare the two systems you have to take in account the whole apparatus. While it is true that China as well as those that do business with them should be ashamed of their mining operation. The fact is that China's stranglehold on rare earth production will end sooner than later. Rare earths are not particularly rare and can be found all over the world. In 2015 the only U.S. company in the rare earth business went bankrupt not due to lack of supply but rather demand. https://investingnews.com/daily/resource-investing/critical-metals-investing/rare-earth-investing/rare-earth-producing-countries/ Quote 2016 was not an easy year for the rare earths sector. Prices were hit hard due to excess supply, and rare earths producers outside China continued to face challenges. So now can I see the solid state reactor or maybe you know we could get back to fast breeders. Edited March 29, 2018 by Outrider I made a boo boo
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