Slashdot Mirror


GE To Turn World's Biggest Civilian Plutonium Stockpile Into Electricity

First time accepted submitter ambermichelle writes "GE Hitachi Nuclear Energy has proposed to the U.K. government to build an advanced nuclear reactor that would consume the country's stockpile of radioactive plutonium. The technology called PRISM, or Power Reactor Innovative Small Module, would use the plutonium to generate low-carbon electricity. The U.K. has the world's largest civilian stockpile of plutonium. The size of the stockpile is 87 tons and growing. Nuclear reactors unlock energy by splitting atoms of the material stored in fuel rods. This process is called fission. For fission to be effective, neutrons – the nuclear particles that do the splitting and keep the reaction going – must maintain the right speed. Conventional reactors use water to cool and slow down neutrons, keeping fission effective. But water-cooled reactors leave some 95 percent of the fuel's potential energy untapped."

43 of 241 comments (clear)

  1. Water-cooled reactors are only 5% efficient? by timeOday · · Score: 3, Insightful

    I am amazed that conventional water-cooled reactors are only 5% efficient. It sure casts the seemingly low efficiency factors of other alternative fuels(such as the cheapest solar panels) into a different light.

    1. Re:Water-cooled reactors are only 5% efficient? by Anonymous Coward · · Score: 2, Informative

      Save solar, wind and various methods of deriving hydroelectric power, all electric power generators boil down to the downright caveman primitive method of heating water into steam to drive turbines. No one has yet figured out anything better.

    2. Re:Water-cooled reactors are only 5% efficient? by Chrisq · · Score: 5, Informative

      I am amazed that conventional water-cooled reactors are only 5% efficient. It sure casts the seemingly low efficiency factors of other alternative fuels(such as the cheapest solar panels) into a different light.

      But you are talking about 5% of the energy from a fuel with an energy density which is about 1,000,000 times the energy density of coal

    3. Re:Water-cooled reactors are only 5% efficient? by Anonymous Coward · · Score: 2, Interesting

      It's not the thermodynamical efficiency. The usual water cooled
      reactors use slow neutrons (water slows the initially fast neutrons from
      fission to slower speeds). These reactors can only extract a fraction of available
      energy from the fuel. Liquid metal cooled reactors use heavy metal
      atoms (sodium, eutectic lead/bismuth) as primary coolant which does not slow
      neutrons. The fast neutrons are used in fast breeder reactors, which can burn
      the fuel more thoroughly or create new fuel (U-239/Pu) as they run.

    4. Re:Water-cooled reactors are only 5% efficient? by Anonymous Coward · · Score: 3, Informative

      It's not 5% efficiency. Of the thermal energy they produce, in fact, more of it can be used than coal, since nuclear reactors can operate at higher temperatures than coal furnaces. However, if someone came up with a coal fuel cell, perhaps it could be even more efficient, since it wouldn't lose energy to thermalization. Muscles are not heat engines, they are like 95% efficient.

      Only 5% of the nuclei that can be fissioned are. In a different reactor, more of the fuel could be fissioned; with current reactors, unburnt fuel is left piling up. Until, apparently, there's enough unburnt fuel to make that different reactor viable.

      This is great news.

    5. Re:Water-cooled reactors are only 5% efficient? by MozeeToby · · Score: 2

      And the energy density of a chunk of Uranium is still orders of magnitude higher than any other practical fuel source. Also, it's not as if we couldn't refine and recycle the fuel and squeeze more of the energy out of it later. Today's nuclear waste storage is tomorrow's 'unlimited energy source'.

    6. Re:Water-cooled reactors are only 5% efficient? by jo_ham · · Score: 4, Informative

      It's not that it's not that efficient, it's that it really doesn't need to be. The energy from fission is mostly captured (although you are dumping a lot of heat), but crucially it leaves high energy products behind in the fuel. It's what makes the spent fuel so hazardous to deal with, which is why it's crazy to suggest burying it in the ground!

      Why bury something that has so much juicy energy still in it that we can extract with current technology? The answer is political, of course.

      The other factor to consider is the sheer magnitude of the energy we're talking about here. E = mc^2 is not just a handy soundbite.

  2. isn't untapped energy a more universal problem? by khallow · · Score: 3, Insightful

    But water-cooled reactors leave some 95 percent of the fuel's potential energy untapped."

    I gather the problem is that decay products poison the fuel after it's been run for a while. One would still need to reprocess fuel rods on a regular basis. But once that's done, you can get more than 5% of the energy from a fuel rod.

  3. Re:New power source? by ae1294 · · Score: 5, Insightful

    This 'fission' technology sounds interesting, but is it safe?

    Yes perfectly safe as long as nothing goes wrong.

  4. Re:New power source? by Dunbal · · Score: 3, Funny

    Living entails a 100% chance of dying - is living safe?

    --
    Seven puppies were harmed during the making of this post.
  5. Re:Nuclear power efficiency by Smidge204 · · Score: 2

    Today's nuclear plants are ~35% or so thermal efficiency, which is not that bad. Upgrading the generating end to a closed cycle turbine loop and staging multiple loops can raise that efficiency a great deal - 50%+ is realized in some newer natural gas power plants. The nuclear part itself is not the limiting factor.
    =Smidge=

  6. radioactive plutonium by Anomalyst · · Score: 2

    Is there a kind of plutonium that isn't radioactive?

    --
    There is no right to feel safe thru security vaudeville at the expense of everyone's freedom, privacy and tax money.
    1. Re:radioactive plutonium by leucadiadude · · Score: 2

      Technically speaking, anything in the periodic table over Pb208 (Lead) is radioactive. It's just some of these elements have REALLY long half lives. And the longer the half life, the lower the radioactivity...

    2. Re:radioactive plutonium by Amouth · · Score: 2

      considering all atoms have some half life and there for are in some way radio active i'd have to say no.. but if you don't consider normal every day stuff radioactive then i'd point you at Plutonium 244

      http://en.wikipedia.org/wiki/Plutonium-244

      with a half-life of ~80 million years the radio activity from it would be very minimal

      --
      '...if only "Jumping to a Conclusion" was an event in the Olympics.'
    3. Re:radioactive plutonium by iggymanz · · Score: 4, Informative

      no. but the usual Pu-239 isn't very radioactive, just emits alphas slowly with a very long half life of 24,200 years. That radiation can't even penetrate your skin or go through a piece of paper. Pu-240 is artificial, usually decays by alpha but sometimes spontaneously fissions, it too has long half-life of more than 6500 years. Then there is Pu-238, emits huge amounts of alphas with its short half-life of 88 years, it's used in RTG batteries and also radioisotope heater units. A kilogram of the stuff gives off 500 watts.

    4. Re:radioactive plutonium by CrimsonAvenger · · Score: 2

      The real question is "how long does it give off 500W?" Just the first day, or for one year, or for ten years, etc.?

      Half life of 88 years. That means it'll be giving 250W after 44 years.

      About 350W after 22 years.

      About 420W after 11 years.

      After one year, 490W...

      --

      "I do not agree with what you say, but I will defend to the death your right to say it"
  7. Re:Short sighted by Alwin+Henseler · · Score: 2

    If Iran gets the bomb, I hope for all Iranians its government won't be stupid enough to use it (in any way, like running a test explosion somewhere).

    And if any country would feel the urge to stop Iran from obtaining a nuclear bomb, let's hope for all our sakes conventional bombs would be used for that job.

    In the meanwhile, "The PRISM reactor actually disposes of a great majority of the plutonium as opposed to simply reusing it over again without ever actually ridding the planet of the substance." sounds like a very good plan to me.

  8. Re:Can you please explain what's an atom again? by NEDHead · · Score: 3, Informative

    kumquat:unit of kum

  9. CANDU by FeatherBoa · · Score: 3, Interesting

    But water-cooled reactors leave some 95 percent of the fuel's potential energy untapped.

    Light water reactors, sure. But heavy water reactors are a whole different kettle of fish. CANDU can already burn anything from natural uranium through plutonium. Hot stuff you just dilute down.

    No need to invent some new crazy reactor, just burn it at Bruce or Pickering.

    1. Re:CANDU by tlhIngan · · Score: 2

      Yes, CANDU is actually very inefficient - it doesn't extract all the usable fuel as other reactors can.

      However, it does have the advantage that it's impossible to have a meltdown - heavy water is a great moderator. In fact, it's required in order to have a reaction - if there's no heavy water, the fuel's inert. And normal water impedes the reaction as well, so if the cooling system leaks, the reaction stops as well.

      Plus, the fuel that comes out needs even heavier processing to become weapons grade.

  10. wording by StuffMaster · · Score: 4, Insightful

    I'm getting tired of all these posts saying "some entity to do something" when the summary says "proposed".

    Assuming that "to" means "going to" to everybody else as it does me, I'd appreciate it if the editors could stop doing or allowing that.

  11. Re:New power source? by JSBiff · · Score: 4, Interesting

    You should really read up on the "Integral Fast Reactor" - the S-PRISM this article is about is evolved from the technology developed in the IFR project.

    The main potential safety weakness of an IFR is the possibility of sodium leaks leading to a sodium fire (I'm not sure how they manage this risk; it certainly seems like a potentially nasty problem, but I'm sure they've taken some sort of measures to try to prevent that from happening; I hope they are effective).

    But, Sodium fires aside, the type of problems you had an Chernobyl, TMI, and Fukushima-Daiichi simply cannot happen in an IFR-style reactor. You can't get supercriticality/runaway fiisson like happened at Chernobyl; you can't get a meltdown; you don't have to worry about steam pressure overwhelming the containment (because water is not used as the coolant, so hence no steam), and you can't get a hydrogen explosion (again, no water in the reactor).

    You might get a hydrogen explosion if, somehow, water started mixing with the sodium, as sodium and water will combine to form sodium hydroxide and hydrogen gas, but if they can keep water out of the reactor, then no hydrogen explosions.

    So far as I know, there have only been a few sodium fires amongst all the world's sodium cooled reactors over the last 60 years - the most famous one was in Japan back in the late 90's or early 00's, and while that scared the public, it wasn't actually a disaster - just a relatively minor industrial accident in the end. I've never heard of a sodium fire at a nuclear plant becoming a major problem, so I don't think the risk of sodium fires is actually a big, unmanageable 'ticking time bomb', but again, I'm no expert.

    Still, I think the technology looks *very* interesting. Let's face it, we have a nuclear waste problem, and either IFR or another type of fast reactor (such as a molten salt fast reactor) are basically the only way to solve that problem. Let's stop fighting the solution to the nuclear waste problem. It truly is the only realistic solution - burn off that 100,000 year "plutonium problem".

  12. Re:Nuclear power efficiency by leucadiadude · · Score: 2

    The higher the temperature of your working fluid, the higher your possible theoretical efficiency can be. The best out there are hitting 60% with a very high temp gas turbine with a steam generator hooked to it's exhaust and a rankine cycle attached to that.

    There are some advanced reactor designs that can hit 50% if built, mostly due to higher working temperatures.

  13. Re:New power source? by chris.alex.thomas · · Score: 2, Funny

    just have a water sprinkler system to put out the fire! no more problems!

  14. Geeky density fun by thatseattleguy · · Score: 4, Interesting

    Just 'cuz I was curious, and it has some peripheral bearing on the question - assuming 19.816 gm/cm^3 for the density of Pu (more than lead) and also assuming (since it's the UK) we're talking "tons" = metric tonnes = 1000kg = 10^6 gm -

    87 x 10^6 gm / 19.816 gm/cm^3 = 4.39 x 10^6 cm^3 = 4.39 m^3.

    4.39 cubic meters is a single cube 1.637 meters on a side (or a little more than 5 feet/side, for us backward Yanks). More or less the size of a smallish SUV, yes?

    Of course their Pu isn't, one hopes, stored all in one solid cube, which would probably exceed critical mass by some large factor. But still, it's not a massive physical quantity of material you're talking about here. /TSG/

  15. Re:New power source? by Anonymous Coward · · Score: 3, Informative

    All power sources are problematic. Energy has a way of making environments uninhabitable to humans... When you start storing large amounts of energy in small spaces things get more dangerous.

    But don't let that fool you. Coal seam fires for instance: http://en.wikipedia.org/wiki/Centralia,_Pennsylvania can make an area uninhabitable for decades, centuries...
    Hydro destroys ecosystems down stream; to some humans, this can destroy their livelihood. And when one damn fails it'll kill hundreds to thousands in a few minutes...

    Nuclear is just scary because its a black box that "normal people" don't understand. When a dam fails, those thousand people die quickly in an easy to comprehend way. When a criticality event happens and people drop to a gamma burst, well, lets just say a wall of water is a lot less scary than nothing at all... And, in the end, all energy storage mediums have risks: to the environment, to people, and to economies...

  16. Re:New power source? by geekoid · · Score: 3, Insightful

    " low frequency risk is still beyond catastrophic.

    Not with modern generators.
    http://en.wikipedia.org/wiki/Integral_Fast_Reactor
    Liquid metal thorium reactor are incredibly safe.
    No event in any nuclear reactor that has ever happened can happen in one. Plus you can burn waste in them.
    Oh and the waster from these return to background radiation levels in 200-500 year. Very workable, and possible to store on site. No shipping the waste.

    The US government should be building 20 of these right now. And the US government should operate them;remove the desire to make bonuses , and all other problems go away with it.

    These are the solution until we can get cheaper solar, or maintainable fusion.

    --
    The Kruger Dunning explains most post on /. http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
  17. Re:New power source? by Tomato42 · · Score: 4, Interesting

    Area under water behind a dam is uninhabitable and unarable, same goes with solar. Wind is just uninhabitable. If you count the amount of land required by them and compare to land made "uninhabitable" by nuclear, average over power generated, nuclear is a clear winner.

    The radiation levels in Chernobyl Zone are lower than natural background radiation in some areas around the globe. Year of living in Ramsar in Iran exceeds nuclear industry limits during emergencies! Calling them "uninhabitable" for 1000 years is a bit of an overstatement... Unarable for food production, maybe, but then you can use those areas for production of automotive fuel.

    Oh, and don't forget the amount of land made unarable and uninhabitable by heavy metal poisoning from regular industry, just look at mercury pollution in USA.

  18. Re:New power source? by Rising+Ape · · Score: 4, Informative

    You can't get supercriticality/runaway fiisson like happened at Chernobyl

    Fast reactors are somewhat notorious for being trickier to control than (well-designed) thermal ones. It's very difficult to avoid a positive void coefficient, and fairly small changes in the fuel geometry can lead to large changes in reactivity. There was a meltdown in an early FBR caused by thermal expansion causing the fuel to bow inwards, increasing the reactivity. Phenix in France also had unexplained loss of reactivity incidents.

  19. Re:Short sighted by geekoid · · Score: 2

    Anything a nuke can do, conventional bombs can do. It's just takes more.

    --
    The Kruger Dunning explains most post on /. http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
  20. Re:New power source? by Endo13 · · Score: 2

    No, you're flat-out wrong. The term 'renewable' indicates an energy source that either never runs out or can be indefinitely replaced. There currently exists no such energy on earth. Solar is no more renewable than any fossile fuel; our great big ball of fire out there is slowly burning out, and when it's done there is absolutely nothing we can do to replace it. We also can't keep renewing it so it doesn't burn out. In fact, if anything fossile fuels are more renewable than solar because it is possible to replenish (ie. renew) them. It just takes a lot of time, and we use them far faster than they can be replenished.

    --
    There is no -1 Disagree mod. Slashdot.org/faq defines mod options. USE IT.
  21. Re:New power source? by AmiMoJo · · Score: 3, Interesting

    I was wondering why GE was trying to get a new reactor design built in the UK instead of its home country, the US. Then I realised why: our government is the only one that will pay for it. The Conservatives view the government as a way to fund commercial enterprises, to build stuff that no bank would back but which with most of the cost paid for out of taxation are a potential gold mine for the owner. That is the way we build nuclear plants here, the tax payer funds it and takes on most of the risk and clean-up cost while the commercial owner creams off a nice profit during the operational lifetime.

    Unfortunately the government always gets ripped off when building anything and the companies running our nuclear facilities seem to be incompetent and unwilling to invest in safety. The plant TFA mentions, Sellafield, is notoriously accident prone, so I'm not sure it is a good idea to give them any more ways to screw up.

    Thanks but no thanks GE, get back to us when you have built a working one paid for out of your own pocket.

    --
    const int one = 65536; (Silvermoon, Texture.cs)
    SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
  22. How much energy in 87 tons of plutonium? by starmonkey · · Score: 2

    Does anyone have a rough idea of how much electricity could be produced by this type of reactor using the 87 tons plutonium stockpile? Please express in terms of % of annual electricity consumption by Britain, or another unit readable by laymen.

  23. Re:New power source? by The+Askylist · · Score: 2

    Makes a change from Labour using public funds to create public sector non-jobs and as a by-product more Labour votes.

    If it's feasible, I'd say go for it - better to use the stockpile to create energy than to waste the money on public sector pensions or windmills / solar.

  24. Re:New power source? by Dogtanian · · Score: 2

    The Conservatives view the government as a way to fund commercial enterprises

    Sounds pretty much like the previous Labour with their enthusiasm for the Private Finance Initiative and such like.

    Even if we're "charitable" and assume a "best case" scenario that they were only doing it for cynical accounting and political reasons, to hide costs in the short term (rather than because they wanted to pander to private business interests), the end result is that the scheme was bordering on evil. Labour politicians knew full well that it would work out grossly more expensive in the medium and long term, any supposed "efficiencies" of the private sector vastly outweighed by the lucrative creaming off of profits funded by inflated running costs- *and* even in the short term, the private companies' ability to dictate how the various facilities were run had damaging effects on (e.g.) education.

    Despite some wanting to paint them as the "loony left", it's useful to remember that Blair and post-Blair Labour were still a bunch of (IMHO) big-business-pandering sell-outs that continued the post-Thatcher consensus in a similar direction to the point that I wouldn't consider them left-wing at all, unless we redefine "left" and "right" to account for the post-Blair "spot the difference" centre-right consensus. Like adjusting the white and black points in a digital image that has virtually no contrast, to extract some marginal detail. (Such a process would make pre-Blair Kinnock/Smith-era Labour look like Maoist extremists by comparison).

    Anyway, back on topic, the Conservatives bleated about the obscene costs of PFI at first, but they've quietened down over that recently, perhaps because they recognise the short-term political usefulness (to them) of it, even if it screws everyone over in every other respect.

    --
    "Slashdot - News and Chat Sites Deviant". (Click "homepage" link above for details).
  25. Re:New power source? by Dogtanian · · Score: 2

    In fact, if anything fossile fuels are more renewable than solar

    Er, weren't fossil fuels originally created, indirectly, by plants absorbing the sun's energy- which would bring us back to solar being non-renewable?

    --
    "Slashdot - News and Chat Sites Deviant". (Click "homepage" link above for details).
  26. Re:New power source? by tragedy · · Score: 2

    That's silly. You're claiming that the term 'renewable' indicates an energy source of a kind that doesn't exist anywhere in the universe? As for fossil fuels being renewable, if they're renewed, it's from plant and animal matter being fossilized. The animal life gets its energy ultimately from photosynthesizing plant life. Can you tell me where photosynthetic plants get their energy?

    A good rule of thumb might be to consider that an energy source that will last for longer than life has existed on Earth and certainly longer than human beings have been around can probably be considered indefinitely replaceable for the time being. Energy sources that may well run out (in the sense of becoming too scarce or hard to extract to be viable) within the lifetimes of currently living people, or even several generations removed probably can't be considered renewable.

  27. Not quite like that by dbIII · · Score: 4, Interesting
    Look up "liquid metal embrittlement" to get an idea of the problems the French and Russians have had with large liquid sodium cooled reactors (nobody else has tried). Water doesn't seem like such a bad idea once you know about it. Work is progressing (eg. new Russian reactor) but it's not a solved problem by any stretch of the imagination. However with good design there can be leaks that merely cause downtime instead of catastrophic breaks.
    Here's a clue - liquid sodium is used for technical and not safety reasons.
    Whoever is selling you on some snake-oil "sodium is safe" marketing line is not being honest to you and you are making yourself look naive and poorly informed by repeating it.

    Let's stop fighting the solution to the nuclear waste problem

    Two things, first it only consumes a small portion of nuclear waste and produces a larger volume of a different type of waste - which I'm sure you already know. Second, the established civilian nuclear energy producers have been the ones fighting the solutions to the nuclear waste problem on the basis of cost. I atteneded a seminar on Synrock over twenty years ago and it's only recently that it has been adopted anywhere due to governments pressuring reactor operators to do something with their waste.

    1. Re:Not quite like that by BlueParrot · · Score: 3, Informative

      Here's a clue - liquid sodium is used for technical and not safety reasons.

      That's half true. There's a number of properties that make sodium very attractive as a coolant:

      -It is much less corrosive to many steel alloys than is water. Some alloys don't corrode at all.
      -It allows for a high power density
      -High thermal conductivity
      -The reactor need not be pressurised
      -Low neutron capture cross section
      -Modest melting point
      -It only forms short lived radio-isotopes when irradiated
      -High operating temperature ( as compared to water )

      From a safety perspective a properly designed sodium cooled reactor is very unlikely to suffer a LOCA due to the low pressure, natural circulation allows for sufficient heat transport even during a total loss of power, the higher thermal conductivity enables fast thermal feedbacks and the higher thermal efficiency ( due to higher temperatures ) means somewhat less decay heat has to be transported away.

      Two things, first it only consumes a small portion of nuclear waste and produces a larger volume of a different type of waste - which I'm sure you already know.

      It can completely fission the actinides you feed it, and the waste it produces decay to safe levels within 300 years, as opposed to 100.000 for the original wastes. Plutonium that has been recycled through it would also be almost useless for nuclear weapons since the isotopic composition after 1 or two passes is even worse than reactor grade plutonium. The reason it only consumes a small portion of nuclear waste is because it needs almost 100 times less fuel than a conventional reactor ( thanks to a positive breeding gain ) , which conversely means that if you consider all the waste we have, there's enough fuel for a thousand years or so.

      Now there are alternative breeder designs to sodium coolant. Lead, molten salt, helium or supercritical water could all work. They all have their respective advantages and disadvantages.

  28. Re:New power source? by cheetah · · Score: 3, Informative

    I would hate to see a scaled up Solar Thermal power plant. The largest one that I know of is the SEGS plant in California. As I remember it has a peak power output of ~350MW. But if your talking about 24/7 operation that drops to a small 75MW of output.

    To get that 75MW of base load capacity, they have to use 6.5KM^2(I had to look that up ^^) of land. If this technology was scaled up to the size of a nuclear plant that has a base load capacity of 1GW you would be talking about using(some people would say destroying) 90KM^2 land.

    Actually, looking at the Invanpah plant which is currently under construction, it's a 392MW(Peak Power) plant that is going to be using ~16KM^2 of land. So the newer plant is even worse on land usage... While it's technically possible to build large solar thermal plants, I don't think your going to find the land to do it. Invanpah was scaled down from initial plans because of land use issues...

    I am not so sure about the cost difference either. Invanpah is a 2.2 billion dollar project. When you compute $ per KW of capacity, your looking at about $5,600 per KW. It's hard to find accurate Nuclear plant numbers since so none have been built in the US in 30 years. Looking online I found two numbers on $per/KW a pro nuclear site quoted ~$2000-2500/KW and a anti-nuclear site said ~5000-6000/KW. I am not sure which to believe but even if it's the high number, it lines up with Invanpah cost almost exactly. But the problem is that this is comparing the Peak Power $/KW price of Invanpah vs Nuclear. I looked all over the place and I couldn't the planned capacity factor... but if Invanpah can only generate a base load of ~100-130MW then the cost of Invanpah would be 3-4 times that of the "High" figure vs Nuclear.

    Honestly after looking at these numbers I am shocked at just how bad Solar Thermal power really is for baseload generation costs. I didn't think it was good but I never would have thought it was this bad.

  29. Re:New power source? by rtfa-troll · · Score: 3, Informative

    No event in any nuclear reactor that has ever happened can happen in one.

    WTF. Where did you get this from? Twenty seconds of research shows the Monju Nuclear Power incident which was a fire caused by a liquid sodium leak. That can obviously repeat in any sodium cooled reactor.

    --
    =~ s,(.*),<sarcasm>$1</sarcasm>,g if any_point_you_wish();
  30. Re:New power source? by BlueParrot · · Score: 2

    Fast reactors are somewhat notorious for being trickier to control than (well-designed) thermal ones. It's very difficult to avoid a positive void coefficient, and fairly small changes in the fuel geometry can lead to large changes in reactivity. There was a meltdown in an early FBR caused by thermal expansion causing the fuel to bow inwards, increasing the reactivity. Phenix in France also had unexplained loss of reactivity incidents.

    The void coefficient is almost unavoidably positive since these reactors don't rely on moderators and the coolants thus acts mostly as a neutron absorber/reflector. However, if you build the reactor the right way, then thermal expansion of the fuel, Doppler broadening, and increased neutron leakage due to expansion of the coolant can make the overall thermal coefficient negative.

    It is in principle posible to make the void coefficient negative, but it tends to involve a heterogeneous core with many different enrichment zones, and it is harder to simulate.

  31. Re:New power source? by AmiMoJo · · Score: 2

    I would hate to see a scaled up Solar Thermal power plant. The largest one that I know of is the SEGS plant in California. As I remember it has a peak power output of ~350MW. But if your talking about 24/7 operation that drops to a small 75MW of output.

    To get that 75MW of base load capacity, they have to use 6.5KM^2(I had to look that up ^^) of land. If this technology was scaled up to the size of a nuclear plant that has a base load capacity of 1GW you would be talking about using(some people would say destroying) 90KM^2 land.

    Your numbers are way off. The older technology used in Spain would need about 575 hectares to generate 1GW, far less than you are claiming. That is old technology too, the newer stuff is more efficient.

    I'll grant you that it isn't going to be as compact as a nuclear plant though, but so what? We have plenty of space where no-one wants to live. The EU is looking to north Africa (and now we are best friends with Libya) because 0.3% of the Sahara could power the whole of western Europe. The US has plenty of unused space too. Maybe you could even recycle the Nevada test sites.

    Invanpah is a 2.2 billion dollar project. When you compute $ per KW of capacity, your looking at about $5,600 per KW.

    You got ass-raped. Spain is paying about â1000/kw. Current worst case cost is about $2.50/kwh, but when comparing that you have to also consider that there is no waste, no fuel, low clean-up cost and low maintenance costs. As mass production ramps up that is expected to fall to about $0.06/kwh in 2015, and unlike a nuclear plant there is no real limit on how long you can run a solar plant for.

    When you look at the actual cost of a nuclear plant over its entire lifetime, including fuelling it, waste storage and site clean-up it is vastly more expensive that solar. Look at it this way: private companies are willing to build solar plants at similar rates of subsidy to coal and gas, but when the UK tried to sell of its existing nuclear stations with a promise to pay for all clean-up costs and insure against accidents they still had no takers.

    --
    const int one = 65536; (Silvermoon, Texture.cs)
    SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC