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Thread: Fast reactors for nuclear power generation

  1. #1
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    Fast reactors for nuclear power generation

    What is a fast reactor?

    For terminology, see the NRCs nuclear glossary.

    To understand why we should or should not build fast reactors, it is necessary to understand what they do and how they differ from other technologies.

    The difference between fast reactors and ordinary ones is that the fast reactor uses the neutrons released by nuclear fission in uranium directly, without slowing them down first. This makes the fast reactor more difficult to build, in the sense that more concentrated fissile material is needed in the core to keep it running, and extra steps must be taken to avoid excessive neutron leakage. This has nothing to do with safety, only how to keep the reaction going. The advantage is that a fast reactor can "burn" all of the heaviest elements (the actinides), instead of mostly U-235, some Pu-239 and a tiny bit of U-238.

    This feature of the fast reactor has multiple very interesting consequences, in fact a carefully designed fast reactor can eliminate every one of the traditional drawbacks of nuclear energy: Nuclear waste, nuclear proliferation, safety and the lack of renewability.

    Nuclear waste:

    A fast reactor in combination with a small fuel recycling plant can burn all of the uranium fed to it, instead of just 1%, as current reactors do. This reduces the volume of the waste by a factor of 20, or 100 if depleted uranium is defined as waste. In addition, reprocessing plants for fast reactors have a much easier job than a normal reprocessing plant - only the true ashes of the fission process, the fission products, must be removed to keep the reactor running. The radioactivity of the fission products decreases to below the level of the natural uranium ore in 300 years, as opposed to the 300000 years which regular spent nuclear fuel needs to reach the same level. Safe storage of a volume of 1/20 the size of the already small volume of normal spent nuclear fuel for a period of just 300 years is trivially simple.

    Nuclear weapons proliferation:

    Fast reactors can be very resistant to nuclear proliferation.

    First, no nation has ever first aquired nuclear weapons by using plutonium from power reactors. All of them have chosen either enrichment of uranium or dedicated plutonium production facilities camouflaged as research reactors. India and the US have demonstrated that plutonium from power reactors can be used in bombs, but that was only after having aquired a significant nuclear weapons expertise. Bombs made from plutonium from power reactors are very radioactive, which complicates production and necessitates heavy uranium radiation shielding and active cooling of the bomb core to keep it from cooking its conventional explosives trigger. Also, such a bomb has an unpredictable explosive yield, and the unavoidable gamma radiation it would emit makes long distance detection of the weapon possible. No military would want a bomb like that when they can more easily build more reliable bombs that are easier to handle.

    Second, in a reprocessing plant for fast reactors, plutonium is never separated from all of the other actinides and the recycled fuel also always contains so high levels of radioactive impurities that it must be handled remotely. Trying to go near it without heavy shielding would mean instant death. Even after a successful theft, which would require a remote manipulation device and a large truck containing many tons of radiation shielding, further processing would be required to separate the plutonium. The high irradiation levels of a fast reactor also makes the plutonium produced in such a reactor even less useful for weapons than regular reactor grade plutonium.

    Third, the volume of recycled fuel is much smaller than in the thermal reactor counterpart, so there is less material to steal or divert to a weapons program.

    Fourth, the small size of the reprocessing plant means that it is practical to co-locate reactor and reprocessing facility. Spent fuel will be reprocessed on-site, which means that no material is supposed to leave the premises for reprocessing. The facility also produces its own fuel. This means that transportation of dangerous material is almost eliminated, the only exception is newly created fuel for other fast reactors. Any sudden increase of truck traffic would be extremely suspicious.

    Even if someone despite all of these obstacles managed to obtain sufficient plutonium to build a bomb, the result would be a very impractical and unreliable weapon.

    In addition to the above, fast reactors remove the need for uranium enrichment. This closes the easiest path to nuclear weapons. Finally, stockpiled civilian and military plutonium, plus weapons grade uranium can be quickly destroyed in a fast reactor. The destroyed weapons material can then be reprocessed into more fuel.

    Safety:

    Fast reactors can be completely passively safe. This was repeatedly demonstrated in the EBR-II test reactor. The reactor was subjected to both the Three Mile Island and the Chernobyl accident scenarios without any mishap. The reactor simply shut down by itself without operator intervention, and the passive decay heat removal systems performed as they should.

    Most fast reactors are cooled by liquid metal, and therefore the coolant is not under pressure. This simplifies construction and enhances safety. Injecting water into the high-pressure, boiling Fukushima reactors turned out to be rather challenging - such a scenario is impossible in a liquid metal cooled reactor. All pumps, valves, heat exchangers and other equipment exposed to radioactive primary coolant is contained inside of the reactor pool. This, together with the lack of pressure, eliminates the possibility of leaks of radioactive coolant.

    Fast reactors make uranium renewable:

    It sounds implausible, but it is in fact true. The energy density of uranium is so enormous, and the fuel efficiency of carefully designed fast reactors so high, that in effect, uranium is a renewable resource. This is because so little fuel is required that the price of electricity is almost completely independent from the price of fuel even when the uranium is extracted from sea water. There is enough uranium in the oceans to provide all the fuel we might ever want until the sun engulfs the earth in some 4 billion years. Erosion continually sends more dissolved uranium into the sea than we can possibly burn, so we would not even be able to change the uranium concentration in the oceans.

    No new uranium would be needed for a long time, we already have enough spent fuel and depleted uranium stockpiled to keep us going for several hundred years.

    One implementation of the IFR, the successor of EBR-II, is GE Hitachi's S-PRISM reactor. This design is ready for building, and provided it is coupled with a suitable reprocessing facility, it has all of the above mentioned properties.
    Last edited by eledille; 2012-04-17 at 02:50 PM.

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    It seems the UK might become one of the first countries to build an IFR: UK nuclear officials have signed a deal for a feasibility study to investigate the possibility of building a pair of PRISM reactors at Sellafield to find out whether such reactors can be used to destroy the large UK plutonium stockpile.

    Note that without the pyroprocessing plant, all the reactors can do is to make the plutonium unsuitable for weapons use. With pyroprocessing, the plutonium stockpile could be used to start up more PRISM reactors to burn the spent fuel or uranium waste too.

    David MacKay confirms that the UK could be powered for 500 years using the plutonium waste. MacKay is the guy who wrote Sustainable Energy - without the hot air (which everyone ought to read, by the way). He is also the chief scientific adviser to the Department of Energy and Climate Change.

    George Monbiot posted even more on the subject, including a withering reply to Friends of the Earth anti-nuclear campaigner Ruth Balogh.
    Last edited by eledille; 2012-04-17 at 07:20 AM.

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    Great, but now lets talk about the downsides:
    1 - Fast reactors are twitchy. They require at least 10x more nuclear material per GWe than thermal reactors, controlling the reactor versus a light water thermal reactor has advantages and disadvantages, but compared to another molten fuel/molten coolant reactor it's way more complex.
    2 - Sodium burns in contact with air and explodes in contact with water
    3 - High intensity fast neutron flux wreak havoc inside the reactor. What I mean is the insides of the reactor lasts far less longer than a similar thermal moderated reactor. The only countries operating fast reactors continuously for decades are former USSR states. Its said that BN series reactors have to essentially be built in pairs, one operates, the other undergoes maintenance, with both operating for less than 1/3 of the time.
    4 - Sodium coolant and oxide fuel limits the reactor operating temperature which limits it's electricity production to the same level of current nuclear.
    Between LWR reactors and IFR, I say we should build IFRs until we have LFTR tech ready. But those that actually invested in this tech outside of Russia/Ukraine/... is GE, with it's S-PRISM reactor, but instead of building the first one and proving it's economics, they are fishing around for a sugar daddy country to pay for the first reactor out of their pocket. The current target is the UK. I challenge GE to put their money where their mouth is...

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    While fast reactors are stalled in NATO countries. Russia presses forward with the first BN-800 reactor entering operations. The first BN-800 reactor will be run as a plutonium burner, consuming weapons grade plutonium (instead of selling it to the USA). However the BN-800 could operate as a breeder reactor (making more plutonium than it consumes and fissioning U-238 from LWR/BWR spent nuclear fuel and depleted uranium). Bottom line, the BN-800 reactor does cost a little more to operate than Russia's cheaper VVER-1200 reactor, but at the same time any unfissioned nuclear material that comes out of the reactor can be reprocessed and made into new fuel.
    Reprocessing spent nuclear fuel from water cooled reactor only increases uranium utilization from 0.6-0.7% up to less than 1.5%. A BN-800 + reprocessing increases uranium utilization to 90% (a 100 fold improvement). It is able to run on plutonium + depleted uranium stockpiles. So it closes the nuclear fuel cycle and improves electricity generated from each ton of mined uranium by two orders of magnitude.
    Next step is the BN-1200 reactor. BN-1200 is just slightly smaller than a full sized nuclear reactor (1200MWe vs 1333-1500MWe for a regular full size reactor).
    If the USA built one fast reactor for each regular reactor in operation it would suck up all of the plutonium and minor actinides in USA spent nuclear fuel. And as those reactors require refueling, depleted uranium from SNF reprocessing + depleted uranium stockpiles would be used to fuel those reactors for its entire lifetime (no new uranium would need to be mined to operate those reactors, only LWR spent nuclear fuel + already available depleted uranium would be used).
    On one hand fast reactors are far more efficient in the long run in using uranium. On the other hand they require almost 10x more nuclear fuel at initial startup than a regular reactor, so they suck up a lot of depleted uranium, spent nuclear fuel and plutonium stockpiles. Which is a good thing (instead of leaving spent nuclear fuel and plutonium in storage, it goes into a reactor).
    Oh if we could only trust Mr Putin machinations. And get over this anti nuclear paranoia.

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    Sounds like we need to bribe Putin for some thorium to build nuclear powered cars. Great concept for utopia.

    Cadillac’s World Thorium Fuel Concept</font>

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    Quote Originally Posted by Tuan View Post
    Sounds like we need to bribe Putin for some thorium to build nuclear powered cars. Great concept for utopia.

    Cadillac’s World Thorium Fuel Concept</font>
    Are you trying to be funny ??
    The BN-600 and BN-800 reactor are a reality. Right now. The BN-1200 will be in a few years.
    Thorium cars are impossible. Can't make a reactor that small. Even a reactor 100x larger than a car sized one is impossible.
    Just the shielding would be over a ton worth of metal.

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    Fast Reactors are an expensive solution to a problem that doesn't exist... there is no Uranium supply shortage and one isn't very likely in the next ~1000 years...

    http://fissilematerials.org/library/rr08.pdf

    Our current stockpile of UF6 is sufficient to power the US reactor fleet for >300 years...
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    Modern enrichment technology uses ~98% less energy than the gaseous diffusion used 20 years ago. This makes it economically feasible to use 'depleted' uranium as feed stock. In the list of problems facing the nuclear industry fuel supply doesn't even break the top 100.

    When someone finds a way to build nuclear plants for <$2/w then it might have a future.

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    Quote Originally Posted by nwdiver View Post
    Fast Reactors are an expensive solution to a problem that doesn't exist... there is no Uranium supply shortage and one isn't very likely in the next ~1000 years...

    http://fissilematerials.org/library/rr08.pdf

    Our current stockpile of UF6 is sufficient to power the US reactor fleet for >300 years...
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Views: 91
Size:  21.3 KB

    Modern enrichment technology uses ~98% less energy than the gaseous diffusion used 20 years ago. This makes it economically feasible to use 'depleted' uranium as feed stock. In the list of problems facing the nuclear industry fuel supply doesn't even break the top 100.

    When someone finds a way to build nuclear plants for <$2/w then it might have a future.
    I fully agree that there isn't a Uranium shortage. However nuclear has been essentially banned from California because the fuel cycle hasn't been closed.

    The problem with new nuclear in the USA isn't nuclear cost, but rather the wind energy credit that allows wind producers to force the overnight spot electricity prices to go negative (since the credit vastly overpowers the moneys paid to add power to the grid when it isn't needed). Natural gas isn't going to be cheap forever. Matter of fact, depending on cheap natural gas is a very unwise policy.

    If we can prove that we have a 10000 to 100000 year supply of Uranium then we can argue that nuclear is as sustainable as geothermal.
    I would much rather have MSR reactors, but the earliest hope for that is 2020ish. In the meantime Russia's BN600 has been producing electricity for 30 years.
    Plus I have my doubts that fast reactors must be expensive, but rather that they are expensive due to lack of scale and R&D to reduce costs.
    Sodium fast reactors don't need steam generators, low/medium/high pressure safety systems, large secondary containment vessels, thick steam piping due to high pressure operation.
    I'm not in love with Sodium. But I'd rather have one or two S-PRISM in construction and have GE prove (or fail to prove) that their design works.

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    When they can build a reactor for <$2/w all the other issues with nuclear power will melt away. Most people hate coal A LOT more than nuclear... Which is cheaper? Which is more dominant? Follow the money...

    There are a lot of reasons Solar PV is taking over... but this is the main reason;
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    There are a lot of reasons nuclear power is going away... but this is the main reason;

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  10. #10
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    Comparing the installed $/kW for solar to that of nuclear or coal is flawed; you should look at the capital cost per kWh, not kW. Solar's capacity factor is about 1/4 that of nuclear, so the capital charge per kWh is proportionally lower. Also, you have to look at the installed cost, not the cost for cells. Cells have to be assembled into panels, fitted out with electronics, shipped and installed.

    That said, one also has to compare other costs, including operations, maintenance, insurance, fuel, and waste disposal. As these are effectively zero for solar but definitely not so for fossil- and nuclear-plants, it's a boon to the economics of solar. (Wind has significant costs for maintenance, insurance, and land royalties.)

    While people often look at installed costs, it's really lifetime cost of energy (LCOE) that matters. Installed costs are a carryover from the days of fossil.
    Last edited by Robert.Boston; 2014-10-13 at 05:50 PM. Reason: Fixed sentence fragment.

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