3 ms·

- no radioactive waste - no nuclear meltdowns / runaway processes - more abundant fuel (on earth and the rest of the solar system) - less pre-processing of f

- no radioactive waste - no nuclear meltdowns / runaway processes - more abundant fuel (on earth and the rest of the solar system) - less pre-processing of fuel - fuel cannot be used to easily make weapons Should we use fission right up until we have viable fusion? Of course, we should definitely be building more fission reactors. But I can't think of a single reason we'd continue using fission once we get to fusion.

hairytrog 6y ago
- there is waste, it's just shorter lived than fission waste and lower in quantity. The expectation is that fusion reactors will have to be regulated in almost exactly the same way as fission reactors because they are nuclear sites, with nuclear waste, and proliferation concerns. - there is lot's of pre processing of the fuel to breed the Tritium in a molten salt blanket that surrounds the reactor and separating from the salt and then feeding it into the chamber - there is plenty of fission and fusion fuel. Yes, there is more hydrogen around. - tritium is used in nuclear weapons as a booster, to dramatically lower the amount of necessary fissile material - each fusion reactor is a fast neutron source, which means it can be used to make weapons grade materials. Conveniently, it has a breeding blanket for tritium, in which other fertile fuels can be place to make weapons material: proliferation concerns are a real problem for fusion
- willis936 6y ago
  - tritium is used in nuclear weapons as a booster It is, but tritium is not put into bombs. Lithium is. - proliferation concerns are a real problem for fusion Unless all fissile materials are banned. It is very easy to check for the existence of fissile materials. If there were no legitimate, safe reasons to have any fissile materials in use on the planet, then a global ban on fissile materials is on the table. A treaty where every nation checks on the other is reasonable. It is hard to build a secret fusion reactor, just as its hard to build a secret uranium centrifuge.
  - philipkglass 6y ago
    It is, but tritium is not put into bombs. Lithium is. Both are put into bombs. The main concern when it comes to tritium supply, regards tritium used for boosting of fission charges. Both applications are crucially important, but fusion boosting appears to require significantly larger quantities of tritium. Tritium and deuterium for boosting are supplied to the weapon from an external reservoir (gas bottle) as part of the arming process of the weapon. Since about 5.5% of existing tritium decays every year, the tritium assigned to each weapon must be regularly replenished. This is done by removing the weapon’s tritium reservoir and exchanging it with a newly refilled reservoir (5). Figure 1.3 shows what may be such a reservoir. From Norwegian Defence Research Establishment report "Tritium production": https://publications.ffi.no/nb/item/asset/dspace:6780/20-01388.pdf https://publications.ffi.no/nb/item/asset/dspace:6780/20-013... Also see this Savannah River Site page about tritium supply for weapons: https://www.srs.gov/general/programs/dp/index.htm https://www.srs.gov/general/programs/dp/index.htm And for a deeper dive, this fascinating blog post: "U.S. Tritium Production for the Nuclear Weapons Stockpile – Not Like the Old Days of the Cold War" https://lynceans.org/all-posts/u-s-tritium-production-for-the-nuclear-weapons-stockpile-not-like-the-old-days-of-the-cold-war/ https://lynceans.org/all-posts/u-s-tritium-production-for-th...
    - why_Mr_Anderson 6y ago
      You are both correct :) Tritium is used for boosting fission bombs, lithium (lithium 6/7 deuterides) as fusion fuel in thermonuclear bombs.
      - peckrob 6y ago
        So interesting story about this. We originally didn't know Lithium-7 would be useful in thermonuclear weapons. It was assumed that it would be inert and that only the Lithium-6 would react with neutrons from the fission primary and breed tritium for the fusion secondary. Then we tested a bomb [0] and the yield on it was accidentally 2.5x greater than anticipated. So large, in fact, that it is still the largest bomb ever detonated by the USA. It turns out that Lithium-7 will also breed tritium if the neutrons are powerful enough, and emits an additional neutron to continue the reaction. Reactions that we might never have discovered (or probably not until later) if it hadn't been for this mistake. The end result was a lot more fuel for the bomb, and the explosion was so large that many of the measuring instruments were vaporized. The large yield also contributed to a radiological disaster [1], which was then the inspiration for the original Godzilla [2]. Anyways, that's how a math/chemistry mistake lead to the most famous kaiju movie (series) of all time. [0] https://en.wikipedia.org/wiki/Castle_Bravo https://en.wikipedia.org/wiki/Castle_Bravo [1] https://en.wikipedia.org/wiki/Daigo_Fukury%C5%AB_Maru https://en.wikipedia.org/wiki/Daigo_Fukury%C5%AB_Maru [2] https://en.wikipedia.org/wiki/Godzilla_(1954_film) https://en.wikipedia.org/wiki/Godzilla_(1954_film)
benlivengood 6y ago
> more abundant fuel (on earth and the rest of the solar system) This is by far the most important reason in the long term. Between stars and even at our own outer planets where solar panels aren't reasonable fusion is the only long-term large scale energy source. It's the difference between being stuck as a Kardashev I or II civilization or approaching III. > Should we use fission right up until we have viable fusion? Of course, we should definitely be building more fission reactors. But I can't think of a single reason we'd continue using fission once we get to fusion. The power density and relative simplicity of fission (including mere thermocoupled) is still worthwhile for robotic probes or initial sources of power in distant places, but we'll be able to make our own fissionables indefinitely once we have solid fusion power.
nickik 6y ago
> no radioactive waste It can create things that take 100 years, a closed cycle thorium breeder takes 200-300 years. And the waste from that process is actually quite useful to extract isotopes for medical, nuclear batteries and other applications. > no nuclear meltdowns / runaway processes Neither can a properly designed fission reactor. And in a molten salt reactor all dangerous gases are chemically bound in the salt and if removed from the reactor would freeze instantly not realising them into the air. So even if some basically unforeseeable chain of event lead to a runaway process, it would not release gases into the air and would stay contained on the reactor site. A fusion reactor is actually more likely to release dangerous gases into the air in case of an accident. > more abundant fuel (on earth and the rest of the solar system) Thorium is incredibly common on most rocky planets. Its already a waste in rare earth mining, so likely you wouldn't even need a single new mine. Every country has enough thorium in the ground to power itself. Mars has plenty of Thorium as well. Fission does not have any practical issues in regards to fuel availability. > - less pre-processing of fuel Depending on the fusion reactor you still need some preprocessing. Depending on fission reactor you need more or less. If you have a continuously refundable thorium breeder you actually need very little pre-processing other then devolving the metallic thorium into salt. While that might be an advantage, I don't see it as some gigantic advantage that it worth the additional complexity of fusion. > fuel cannot be used to easily make weapons Most fusion reactors that are considered today absolutely can be used to create nuclear weapons. I would argue starting a nuclear weapons program if you have control over a fusion reactor is far easier compared to when you have a thorium breeder. With neither is it easy in any way. Practically is mostly a non problem. This is a buggy-men, and would still be with fusion. > Should we use fission right up until we have viable fusion? Of course, we should definitely be building more fission reactors. But I can't think of a single reason we'd continue using fission once we get to fusion. Well, the cost is the reason why you might not want to do fusion if fission works. That said, I'm not anti-fusion. I'm just miffed that we rush into fusion when we have so much improvement on fission that could solve the exact problems fusion is trying to solve.

hairytrog 6y ago

- there is waste, it's just shorter lived than fission waste and lower in quantity. The expectation is that fusion reactors will have to be regulated in almost exactly the same way as fission reactors because they are nuclear sites, with nuclear waste, and proliferation concerns. - there is lot's of pre processing of the fuel to breed the Tritium in a molten salt blanket that surrounds the reactor and separating from the salt and then feeding it into the chamber - there is plenty of fission and fusion fuel. Yes, there is more hydrogen around. - tritium is used in nuclear weapons as a booster, to dramatically lower the amount of necessary fissile material - each fusion reactor is a fast neutron source, which means it can be used to make weapons grade materials. Conveniently, it has a breeding blanket for tritium, in which other fertile fuels can be place to make weapons material: proliferation concerns are a real problem for fusion

willis936 6y ago
- tritium is used in nuclear weapons as a booster It is, but tritium is not put into bombs. Lithium is. - proliferation concerns are a real problem for fusion Unless all fissile materials are banned. It is very easy to check for the existence of fissile materials. If there were no legitimate, safe reasons to have any fissile materials in use on the planet, then a global ban on fissile materials is on the table. A treaty where every nation checks on the other is reasonable. It is hard to build a secret fusion reactor, just as its hard to build a secret uranium centrifuge.
- philipkglass 6y ago
  It is, but tritium is not put into bombs. Lithium is. Both are put into bombs. The main concern when it comes to tritium supply, regards tritium used for boosting of fission charges. Both applications are crucially important, but fusion boosting appears to require significantly larger quantities of tritium. Tritium and deuterium for boosting are supplied to the weapon from an external reservoir (gas bottle) as part of the arming process of the weapon. Since about 5.5% of existing tritium decays every year, the tritium assigned to each weapon must be regularly replenished. This is done by removing the weapon’s tritium reservoir and exchanging it with a newly refilled reservoir (5). Figure 1.3 shows what may be such a reservoir. From Norwegian Defence Research Establishment report "Tritium production": https://publications.ffi.no/nb/item/asset/dspace:6780/20-01388.pdf https://publications.ffi.no/nb/item/asset/dspace:6780/20-013... Also see this Savannah River Site page about tritium supply for weapons: https://www.srs.gov/general/programs/dp/index.htm https://www.srs.gov/general/programs/dp/index.htm And for a deeper dive, this fascinating blog post: "U.S. Tritium Production for the Nuclear Weapons Stockpile – Not Like the Old Days of the Cold War" https://lynceans.org/all-posts/u-s-tritium-production-for-the-nuclear-weapons-stockpile-not-like-the-old-days-of-the-cold-war/ https://lynceans.org/all-posts/u-s-tritium-production-for-th...
  - why_Mr_Anderson 6y ago
    You are both correct :) Tritium is used for boosting fission bombs, lithium (lithium 6/7 deuterides) as fusion fuel in thermonuclear bombs.
    - peckrob 6y ago
      So interesting story about this. We originally didn't know Lithium-7 would be useful in thermonuclear weapons. It was assumed that it would be inert and that only the Lithium-6 would react with neutrons from the fission primary and breed tritium for the fusion secondary. Then we tested a bomb [0] and the yield on it was accidentally 2.5x greater than anticipated. So large, in fact, that it is still the largest bomb ever detonated by the USA. It turns out that Lithium-7 will also breed tritium if the neutrons are powerful enough, and emits an additional neutron to continue the reaction. Reactions that we might never have discovered (or probably not until later) if it hadn't been for this mistake. The end result was a lot more fuel for the bomb, and the explosion was so large that many of the measuring instruments were vaporized. The large yield also contributed to a radiological disaster [1], which was then the inspiration for the original Godzilla [2]. Anyways, that's how a math/chemistry mistake lead to the most famous kaiju movie (series) of all time. [0] https://en.wikipedia.org/wiki/Castle_Bravo https://en.wikipedia.org/wiki/Castle_Bravo [1] https://en.wikipedia.org/wiki/Daigo_Fukury%C5%AB_Maru https://en.wikipedia.org/wiki/Daigo_Fukury%C5%AB_Maru [2] https://en.wikipedia.org/wiki/Godzilla_(1954_film) https://en.wikipedia.org/wiki/Godzilla_(1954_film)

benlivengood 6y ago

> more abundant fuel (on earth and the rest of the solar system) This is by far the most important reason in the long term. Between stars and even at our own outer planets where solar panels aren't reasonable fusion is the only long-term large scale energy source. It's the difference between being stuck as a Kardashev I or II civilization or approaching III. > Should we use fission right up until we have viable fusion? Of course, we should definitely be building more fission reactors. But I can't think of a single reason we'd continue using fission once we get to fusion. The power density and relative simplicity of fission (including mere thermocoupled) is still worthwhile for robotic probes or initial sources of power in distant places, but we'll be able to make our own fissionables indefinitely once we have solid fusion power.

nickik 6y ago

> no radioactive waste It can create things that take 100 years, a closed cycle thorium breeder takes 200-300 years. And the waste from that process is actually quite useful to extract isotopes for medical, nuclear batteries and other applications. > no nuclear meltdowns / runaway processes Neither can a properly designed fission reactor. And in a molten salt reactor all dangerous gases are chemically bound in the salt and if removed from the reactor would freeze instantly not realising them into the air. So even if some basically unforeseeable chain of event lead to a runaway process, it would not release gases into the air and would stay contained on the reactor site. A fusion reactor is actually more likely to release dangerous gases into the air in case of an accident. > more abundant fuel (on earth and the rest of the solar system) Thorium is incredibly common on most rocky planets. Its already a waste in rare earth mining, so likely you wouldn't even need a single new mine. Every country has enough thorium in the ground to power itself. Mars has plenty of Thorium as well. Fission does not have any practical issues in regards to fuel availability. > - less pre-processing of fuel Depending on the fusion reactor you still need some preprocessing. Depending on fission reactor you need more or less. If you have a continuously refundable thorium breeder you actually need very little pre-processing other then devolving the metallic thorium into salt. While that might be an advantage, I don't see it as some gigantic advantage that it worth the additional complexity of fusion. > fuel cannot be used to easily make weapons Most fusion reactors that are considered today absolutely can be used to create nuclear weapons. I would argue starting a nuclear weapons program if you have control over a fusion reactor is far easier compared to when you have a thorium breeder. With neither is it easy in any way. Practically is mostly a non problem. This is a buggy-men, and would still be with fusion. > Should we use fission right up until we have viable fusion? Of course, we should definitely be building more fission reactors. But I can't think of a single reason we'd continue using fission once we get to fusion. Well, the cost is the reason why you might not want to do fusion if fission works. That said, I'm not anti-fusion. I'm just miffed that we rush into fusion when we have so much improvement on fission that could solve the exact problems fusion is trying to solve.