5 ms·

The very high cost of fission has a lot to do with how nasty, awkward, long-lasting and expensive the fuel and waste are. We really won't know until we try bui

The very high cost of fission has a lot to do with how nasty, awkward, long-lasting and expensive the fuel and waste are. We really won't know until we try building a power plant.

TheOtherHobbes 10y ago
Fusion produces energetic neutrons, and energetic neutrons are a very good way to make things radioactive. So all the popular approaches create waste that is more radioactive than fission waste, and probably comparable in volume. The only up side is that the decay products have a shorter half life. So the waste will only be a problem for a century or so, instead of for millennia. This may be better than fission, but it's definitely not clean by any realistic definition of the word.
- Baeocystin 10y ago
  Uranium mining is a nasty business. Deuterium concentration is, by comparison, just a bunch of water-filled centrifuges. Surly that would make a large difference all on its own, no?
- Jedd 10y ago
  > The only up side is that the decay products have a shorter half life. So the waste will only be a problem for a century or so, instead of for millennia. This sounds like a tremendous underestimation of the problem - handling waste. We have people who live 'for a century or so' but we don't even have languages (now!) that have lasted a millenia.
  - chadgeidel 10y ago
    Our current "decay product" of energy generation (carbon) is going to impact our world for a lot longer than a century. I'll take known-quantity, manageable century-long decay products over unknown-quantity, nearly unmanageable (large-scale carbon sequestration is hard) any day.
  - kmicklas 10y ago
    > we don't even have languages (now!) that have lasted a millenia. Wut?
    - garfieldnate 10y ago
      You might make the case that MSA and Classical Arabic is an exception, but MSA is not spoken natively AFAIK. Other than that, I cannot think of any examples where a language spoken by someone a thousand years ago would be intelligible now. Languages change in sound, structure and vocabulary over time naturally. That's how we got the Romance languages from Latin (which is no longer spoken). However, language standardization artificially slows down change, so current languages might last a lot longer. English hasn't changed that much since Shakespeare and the KJV. Maybe interesting to you: https://en.m.wikipedia.org/w/index.php?title=Conservative_(language) https://en.m.wikipedia.org/w/index.php?title=Conservative_(l...
      - ohyes 10y ago
        What about Hebrew?
        garfieldnate 10y ago
        Yes, for written form you could make that argument, though there are some differences between the two. Also, it didn't really "last" in the normal sense, since it was revived in modern times. Also, Tibetan maintains the same spellings from 1200 years ago, but that really just means that it's very, very difficult to spell, since the pronunciation no longer matches spelling well. These make interesting exceptions to the general rule, so I think the original point is still very valid. I'm curious about old vs. modern Syrian, if anyone knows about that.
    - Jedd 10y ago
      Okay, point taken - we certainly do have some languages still in use that that have lasted more than a millennia. I'd posit that storage is not a solved problem, and a big part of that is a lack of confidence that we can reliably communicate with the people who will have to deal with this waste in the distant future. There's also the inherent disdain involved in passing on massive costs and risks to future generations to solve a comparatively short-term problem of ours.
- Retric 10y ago
  Not really, fusion needs to keep the reaction in a near vacuum where fission uses a multi loop system which creates a lot more surface area and waste. Further the blanket needs to be made from lithium to make tritium in a DT fusion setup capturing those fast neutrons without creating long term waste. Most importantly they are vastly safer and thus need far less security and far less insurance. Remember a huge benefit for PV solar and wind is they don't need guards. PS: Another consideration is the half life is short enough that over 20 years things become a lot less radioactive. Fission has some half lives just long enough to be a real pain.
- Symmetry 10y ago
  The advantage with Fusion is that you can control what elements are exposed to the neutron flux and so control what sort of new elements or isotopes you get. For instance there's basically nothing in the air except for dust that will absorb a neutron and turn into something you have to worry about. And part of the design of a fusion reactor is to use lithium to absorb as many neutrons as possible to breed tritium to feed back into the reaction. By contrast the byproducts of a fission reaction are set by the fuels used and include really nasty stuff like Strontium-90 and so on. But even fission plants are designed so that the radioactive byproducts are essentially all spent fuel or things contaminated by spent fuel. Neutron activation is a design consideration rather than a source of waste. Of course the neutron flux will tend to enbrittle the metals used in it's construction which will have the effect of increasing maintenance costs.
- Gupie 10y ago
  Don't you get a lot more energy for a given amount of radiation?
loup-vaillant 10y ago
Much of the nasty stuff comes from the fact that current (light water) reactors were actually meant to produce military plutonium. Bombs first. Energy was a by-product, and a very nice way to sell nuke-making to the civilians. There is another way of doing fission, that was demonstrated (working prototype and all) in the 60's: molten salt. You basically dissolve the fissile matter in molten salt, provide initial heat, and you have a reaction going. This has multiple advantages: - Originally designed for a nuclear plane, it is capable of reacting to load changes very quickly. It's basically easy to power-up, and easy to shut down. - It is amenable to a passive security set up: when all goes wrong, the reactor shuts down by default. When it does, the radioactive matter is trapped in no-longer-molten salt, such that contamination is limited even if there is a leak. - It consumes 90% of the fissile matter before it has to go to recycling. (Current reactors do about 10%.) - It currently produces 5 times less waste than current reactors. There is hope to do even better. - Last but not least, it can run off thorium, which is 4 times more abundant than uranium, and much better spread out geographically. With one or two decades and a few billion dollars, we could make commercial grade reactors. They would almost certainly be significantly cleaner, and much safer than current light water reactors. They could adapt to changes of demand in the power grid, or compensate for the volatility of most renewable power sources without the need for a "battery miracle". Overall, they would make a terrific mid-term solution, that could last a couple centuries. More than enough time to come up with something better. https://en.wikipedia.org/wiki/Molten_salt_reactor https://en.wikipedia.org/wiki/Molten_salt_reactor
- marcosdumay 10y ago
  Molten halogen salts are nasty stuff. I'm sure with some extra R&D people could make those reactors reliable, but if you search the new generation reactors on Wikipedia, you'll see every one of them ended in some kind of failure.
  - loup-vaillant 10y ago
    I'll wager this was mostly because of the lack of funding. Those reactors were not as thoroughly researched as the light water ones. In a sense, they're still stuck in the 60's. (Really, putting molten salt reactors in the "new generation" bucket is a bit of a joke. It's old stuff that was shut down mostly for military and economic reasons, and only recently got more traction.) Another possible cause is path dependence. We have a whole industry around solid fuel, light water reactors. Switching to molten salt throws much of that away. Much research still need to be done. We may want cleaner salts, we want even less radioactive waste, and we definitely want to accurately assess the safety of this stuff ("passive security" is not enough by itself). This means more prototypes reactors, of various sizes, each more expensive than before. We want a few million dollars for the small ones, then a few billions for the big ones.

The very high cost of fission has a lot to do with how nasty, awkward, long-lasting and expensive the fuel and waste are. We really won't know until we try building a power plant.

TheOtherHobbes 10y ago

Fusion produces energetic neutrons, and energetic neutrons are a very good way to make things radioactive. So all the popular approaches create waste that is more radioactive than fission waste, and probably comparable in volume. The only up side is that the decay products have a shorter half life. So the waste will only be a problem for a century or so, instead of for millennia. This may be better than fission, but it's definitely not clean by any realistic definition of the word.

Baeocystin 10y ago
Uranium mining is a nasty business. Deuterium concentration is, by comparison, just a bunch of water-filled centrifuges. Surly that would make a large difference all on its own, no?
Jedd 10y ago
> The only up side is that the decay products have a shorter half life. So the waste will only be a problem for a century or so, instead of for millennia. This sounds like a tremendous underestimation of the problem - handling waste. We have people who live 'for a century or so' but we don't even have languages (now!) that have lasted a millenia.
- chadgeidel 10y ago
  Our current "decay product" of energy generation (carbon) is going to impact our world for a lot longer than a century. I'll take known-quantity, manageable century-long decay products over unknown-quantity, nearly unmanageable (large-scale carbon sequestration is hard) any day.
- kmicklas 10y ago
  > we don't even have languages (now!) that have lasted a millenia. Wut?
  - garfieldnate 10y ago
    You might make the case that MSA and Classical Arabic is an exception, but MSA is not spoken natively AFAIK. Other than that, I cannot think of any examples where a language spoken by someone a thousand years ago would be intelligible now. Languages change in sound, structure and vocabulary over time naturally. That's how we got the Romance languages from Latin (which is no longer spoken). However, language standardization artificially slows down change, so current languages might last a lot longer. English hasn't changed that much since Shakespeare and the KJV. Maybe interesting to you: https://en.m.wikipedia.org/w/index.php?title=Conservative_(language) https://en.m.wikipedia.org/w/index.php?title=Conservative_(l...
    - ohyes 10y ago
      What about Hebrew?
      - garfieldnate 10y ago
        Yes, for written form you could make that argument, though there are some differences between the two. Also, it didn't really "last" in the normal sense, since it was revived in modern times. Also, Tibetan maintains the same spellings from 1200 years ago, but that really just means that it's very, very difficult to spell, since the pronunciation no longer matches spelling well. These make interesting exceptions to the general rule, so I think the original point is still very valid. I'm curious about old vs. modern Syrian, if anyone knows about that.
  - Jedd 10y ago
    Okay, point taken - we certainly do have some languages still in use that that have lasted more than a millennia. I'd posit that storage is not a solved problem, and a big part of that is a lack of confidence that we can reliably communicate with the people who will have to deal with this waste in the distant future. There's also the inherent disdain involved in passing on massive costs and risks to future generations to solve a comparatively short-term problem of ours.
Retric 10y ago
Not really, fusion needs to keep the reaction in a near vacuum where fission uses a multi loop system which creates a lot more surface area and waste. Further the blanket needs to be made from lithium to make tritium in a DT fusion setup capturing those fast neutrons without creating long term waste. Most importantly they are vastly safer and thus need far less security and far less insurance. Remember a huge benefit for PV solar and wind is they don't need guards. PS: Another consideration is the half life is short enough that over 20 years things become a lot less radioactive. Fission has some half lives just long enough to be a real pain.
Symmetry 10y ago
The advantage with Fusion is that you can control what elements are exposed to the neutron flux and so control what sort of new elements or isotopes you get. For instance there's basically nothing in the air except for dust that will absorb a neutron and turn into something you have to worry about. And part of the design of a fusion reactor is to use lithium to absorb as many neutrons as possible to breed tritium to feed back into the reaction. By contrast the byproducts of a fission reaction are set by the fuels used and include really nasty stuff like Strontium-90 and so on. But even fission plants are designed so that the radioactive byproducts are essentially all spent fuel or things contaminated by spent fuel. Neutron activation is a design consideration rather than a source of waste. Of course the neutron flux will tend to enbrittle the metals used in it's construction which will have the effect of increasing maintenance costs.
Gupie 10y ago
Don't you get a lot more energy for a given amount of radiation?

loup-vaillant 10y ago

Much of the nasty stuff comes from the fact that current (light water) reactors were actually meant to produce military plutonium. Bombs first. Energy was a by-product, and a very nice way to sell nuke-making to the civilians. There is another way of doing fission, that was demonstrated (working prototype and all) in the 60's: molten salt. You basically dissolve the fissile matter in molten salt, provide initial heat, and you have a reaction going. This has multiple advantages: - Originally designed for a nuclear plane, it is capable of reacting to load changes very quickly. It's basically easy to power-up, and easy to shut down. - It is amenable to a passive security set up: when all goes wrong, the reactor shuts down by default. When it does, the radioactive matter is trapped in no-longer-molten salt, such that contamination is limited even if there is a leak. - It consumes 90% of the fissile matter before it has to go to recycling. (Current reactors do about 10%.) - It currently produces 5 times less waste than current reactors. There is hope to do even better. - Last but not least, it can run off thorium, which is 4 times more abundant than uranium, and much better spread out geographically. With one or two decades and a few billion dollars, we could make commercial grade reactors. They would almost certainly be significantly cleaner, and much safer than current light water reactors. They could adapt to changes of demand in the power grid, or compensate for the volatility of most renewable power sources without the need for a "battery miracle". Overall, they would make a terrific mid-term solution, that could last a couple centuries. More than enough time to come up with something better. https://en.wikipedia.org/wiki/Molten_salt_reactor https://en.wikipedia.org/wiki/Molten_salt_reactor

marcosdumay 10y ago
Molten halogen salts are nasty stuff. I'm sure with some extra R&D people could make those reactors reliable, but if you search the new generation reactors on Wikipedia, you'll see every one of them ended in some kind of failure.
- loup-vaillant 10y ago
  I'll wager this was mostly because of the lack of funding. Those reactors were not as thoroughly researched as the light water ones. In a sense, they're still stuck in the 60's. (Really, putting molten salt reactors in the "new generation" bucket is a bit of a joke. It's old stuff that was shut down mostly for military and economic reasons, and only recently got more traction.) Another possible cause is path dependence. We have a whole industry around solid fuel, light water reactors. Switching to molten salt throws much of that away. Much research still need to be done. We may want cleaner salts, we want even less radioactive waste, and we definitely want to accurately assess the safety of this stuff ("passive security" is not enough by itself). This means more prototypes reactors, of various sizes, each more expensive than before. We want a few million dollars for the small ones, then a few billions for the big ones.