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I used to be so excited about fusion, but then I actually learned more about it. Perhaps I'm missing something, but the benefits over fission seem underwhelming

I used to be so excited about fusion, but then I actually learned more about it. Perhaps I'm missing something, but the benefits over fission seem underwhelming. It's about the same cost on a per-megawatt basis. Modern fission plants are totally safe. Nuclear waste is basically a non-problem, especially with the most recent technology. And fission has the huge benefit of being a mature, proven technology. What's the big benefit of fusion that makes it worth investing so much money? The only thing I can see is that it doesn't require uranium, which can be abused to make weapons. But does that by itself justify the investment?

scanny 5y ago
> Modern fission plants are totally safe. Nuclear waste is basically a non-problem Just removing that as part of the rhetoric around the tech makes fusion invaluable.
- d_theorist 5y ago
  That is true actually. Seems silly but it's actually a serious benefit! The main issue with fission is that people have become irrational about it. Maybe we get a fresh start with fusion.
  - civilized 5y ago
    Unfortunately, a lot of the same environmental interest groups that halted the scaling up of fission also hate fusion. It's best to think of fusion as a way to generate effectively unlimited amounts of energy, kicking in 50-100 years from today. This could be super useful for the long-term ambitions of human civilization - energy has been such a hard constraint for so long that people have barely thought about the amazing stuff we could do with an effectively unlimited energy supply. For addressing climate change, it's likely to be too-little-too-late to bank on. But a century from now it'll be nice for cheap fresh water / agriculture / climate control anywhere on this planet, space elevators, interplanetary/interstellar travel, terraforming, cheap fresh water / agriculture / climate control on other planets, etc. This sort of stuff is incredibly energy-hungry and it's unlikely that renewables will be able to supply the requirements alone. (It'd be awesome if one of the private fusion start-ups gets us there a lot faster, but this is what I'm projecting for now!)
    - simiones 5y ago
      > generate effectively unlimited amounts of energy I don't understand where this concept is coming from. The best ever fusion power experiments so far have not even produced 1 miliwatt net electrical power. ITER, if it succeeds in its 30 year timeline, will not be even close to engineering breakeven (net power generation) - they estimate 0.57 output power/input power ratio - with DEMO hoping to break even 20 years later. Why is there this bizarre idea that we'll jump from <massive effort to get even one miliwatt> to <unlimited power> with fusion?
      - arcanon 5y ago
        It’s not unlimited power, it’s unlimited fuel. The hype is coming from REBCO tape magnets which aren’t in ITER. Many consider ITER to already be obsolete. This is like how computers used to take up whole rooms in the 50s but later could sit in the corner. Fusion takes up whole buildings (ITER) but the MIT ppl proved a magnet so that it can fit in just a room. As our magnets get stronger the tokamaks can get smaller. Room sized tokamak is manageable for commercialization. Commonwealth Fusion Systems has a pretty clear path it seems.
      - civilized 5y ago
        There's a nearby fusion reactor that generates quite a lot of power. You may have heard of it. Jokes aside, fusion would provide way more energy per fuel mass than any other source if we could only contain sufficiently hot plasma. Better magnets may be the key, as the other comment alludes.
- simiones 5y ago
  But it's not true. Fusion power plants produce a steady stream of radioactive waste from the neutron bombardment. They can leak radioactive tritium. They can explode, spewing hot plasma and chunks of radioactive reactor walls in the area around the plant. The scope of the problem is nowhere near a fission reactor meltdown, but it's also not "gone".
leephillips 5y ago
It is not worth investing money in, because it will never supply grid power: http://progressive.org/op-eds/let-cut-our-losses-on-fusion-energy-180313/ http://progressive.org/op-eds/let-cut-our-losses-on-fusion-e... Here is another physicist warning about the hype just a few days ago: http://backreaction.blogspot.com/2021/10/how-close-is-nuclear-fusion-power.html http://backreaction.blogspot.com/2021/10/how-close-is-nuclea...
- ip26 5y ago
  It receives a pretty small level of funding, so I'm not quite sure there are many losses to cut. $2.2bn over 5 years is about $1.50 per person per year. It's comparable to the funding for the CPB.
  - leephillips 5y ago
    It’s not much compared with some other budget items, you’re right. But a billion here, a billion there, and soon you’re talking about real money.
  - simonh 5y ago
    ITER will cost about the same as the Manhattan project, around $21bn in 2021 $, and that's just one project. Total investment in Fusion globally is huge and the problem is at the moment there are multiple different feasible ways forward, and it's not clear which will pan out. There's huge risk of wasting large amounts of resources and time, even if we do eventually figure it out.
    - willis936 5y ago
      Creating conditions to split a heavy nucleus for 1 microsecond is much easier to do than fusing light nuclei steady state.
      - simonh 5y ago
        Yes of course, I know that. I’m not even saying the investment in fusion is a bad idea. I’m just pointing out that actually our investment in it is enormous and very risky.
skywal_l 5y ago
Don't you think that the fact that you can use sea water as input and you get hydrogen as output is a huge advantage over fission? Add to that the fact that there is no fukushima style meltdown in a fusion power plant. If something goes wrong, it just stops. Finally, contrary to fission, fusion power plants will be able to adjust their power output as fast as gaz power plants. It takes months to turn on or off a fission power plant. So yes, there is definitely a few benefits to fusion. And take a step back on the numbers. Look at how much we injected in banks in 2008. If it works (and indeed there is a risk they won't make it work and this is probably where the argument should be) the investment would be amortize over thousands of years... Can you imaging a guy, 3000 years ago in China, complaining about spending money on a kiln to smelt that thing called iron?...
- soperj 5y ago
  >Add to that the fact that there is no fukushima style meltdown in a fusion power plant. If something goes wrong, it just stops. That's already the case with the CANDU reactors. They also don't need upgraded uranium, and can use uranium from decommissioned nuclear weapons.
- d_theorist 5y ago
  >Don't you think that the fact that you can use sea water as input and you get hydrogen as output is a huge advantage over fission? If it reduces the cost. But it doesn't seem to. >Add to that the fact that there is no fukushima style meltdown in a fusion power plant. If something goes wrong, it just stops. Same as the most recent fission plants.
  - flavius29663 5y ago
    > Same as the most recent fission plants. How are these 2 things the same? On one hand, you rely on a good design and execution to achieve an automatic stop. History has shown time and again that there will always be something that goes wrong: from the cracking rods of Chernobyl to the backup power at Fukushima. On the other, if you don't design and execute perfectly, nothing works, so there is nothing to shut down. This is the definition of "fail safe". It's like saying both a meteorite and a rocket will reach 500km/h in the atmosphere, but me it's pretty obvious one is much more likely to do so.
tambourine_man 5y ago
>Modern fission plants are totally safe. Nuclear waste is basically a non-problem, especially with the most recent technology Please elaborate on both. And I think we can all agree there's no such thing as totally safe, only risk management.
- orwin 5y ago
  Gen2, even with weird designs (so Fukushima included) are individually safer than any coal plant ever built, and the whole generation will kill less people, even counting those dying in a shameful, unprepared evacuation, that the new "clean coal" plants (with flue gas discharge) built in the western world since the 2000s. Not taking into account the GHG emissions. Number of death/GW is in the favor of nuclear for any power station, even when counting dislodged people as "dead" (in this case, hydro is actually the 2nd most deadly) For the nuclear wast beeing a non-problem: i don't agree, but i understand where he is coming from. There is basically 3 type of nuclear waste: low-activity waste is waste that we could ignore, and the most present. radioactivity levels are what is find in granitic area. Often indirectly contaminated materials, or very long-lived isotope (radioactive decay is long, the the material is not very radioactive). It can still be dangerous and create radon gas if poorly stored (as do caves in granitic areas). We have no good answer to that. Maybe separate long=lived isotopes from the rest, store it, and reuse the contaminated materials after waiting a dozen years, mixing it with new cement or something. intermediate-activity waste: still extremely dangerous, its often contaminated material (filter, pipes), or active (and dangerous) isotopes, with a half-life of up 500 years (i think the most present have an half-life of 200 years, and you need 10 cycles basically to be rid of it). Those are not direct fission byproduct (i don't think so, i don't remember exactly, maybe a small number is?). High-activity waste: This is the real dangerous stuff. Those can stay hot for years. There is to kind: - direct fission byproducts. Some degrade not in stable isotopes, but in the intermediate-activity waste, so even with a short half-life, they take as long as the intermediate ones to get rid of (since they degrade into it. If i'm over-explaining, sorry). Some degrade into stable heavy metals that also poison the environment, in a different way. - transuranic elements. The graphite from Chernobyl could be counted in this category? (not sure, if an expert is here, can you infirm this?). I do not exactly understand this category, but its basically elements from the reactor core that are not fission products. The reason why GP said "Nuclear waste is basically a non-problem" might be because we are able to re-use some the fission products, and to deactivate the rest. Both technologies are at an experimental stage, the first one could be in commercial use in the decade if China doesn't fail. And since the fission product decay is what's create the most troublesome waste (half-life between 100 and 500 years mean the wast stay dangerous for between 1000 and 5000 years), its a "non-problem". I don't have the material on hand, i learned that in 2019. i could find it again if you wanted (probably mostly be in French, sorry), and to be fair, i might have oversimplified things i did not understand in the first place.
c7DJTLrn 5y ago
>Modern fission plants are totally safe Ha what? The number of flaws in any system is unknowable. We thought the Fukushima Daiichi reactors were safe and then what happened? Meltdown because the backup generators were flooded. That statement transposed to software engineering is like saying "we use Kubernetes so we have 24/7 uptime".
nobody9999 5y ago
>What's the big benefit of fusion that makes it worth investing so much money? 4-20 times the energy density of fissionable materials[0] and fuel that's the most common element in the universe. [0] https://en.wikipedia.org/wiki/Energy_density#In_nuclear_reactions https://en.wikipedia.org/wiki/Energy_density#In_nuclear_reac...
- d_theorist 5y ago
  And what is the benefit of that?
  - nobody9999 5y ago
    >And what is the benefit of that? I'll leave that as an (fairly obvious) exercise for you, dear reader.
goodpoint 5y ago
> Modern fission plants are totally safe Unless there's a war. Unless corruption leads to poor management of the plants. Unless nuclear waste is mismanaged. Unless there is an earthquake or tsunami of completely unexpected intensity.
- mzs 5y ago
  or corrosion of containment vessel, or an airplane strike… http://green.blogs.nytimes.com/2010/04/21/critics-challenge-safety-of-new-nuclear-reactor-design/ http://green.blogs.nytimes.com/2010/04/21/critics-challenge-...
- orwin 5y ago
  > Unless there's a war. Unless corruption leads to poor management of the plants. Unless nuclear waste is mismanaged. Unless there is an earthquake or tsunami of completely unexpected intensity. No for mismanagement, earthquake or tsunami, the gen3 are completely safe, all security mesures are passives, unless the fault is directly on the core, it will fail gracefully. Irradiated water might leak, but to be fair, underground water in granitic areas are more irradiated than the fission product pool. Issues are war (and in this case, direct sabotage from an actor with actual knowledge, or a direct hit into a functioning reactor, so pretty much on purpose strike. I wouldn't be afraid of terrorism) and waste.
cantagi 5y ago
Since a commercial fusion reactor hasn't yet been developed, you can't argue that it is or will be the same cost per-megawatt as fission power. That's because you can't predict any advances in technology that make fusion easier or reduce the capital cost. Based on a HN recommendation, I read this book: https://www.amazon.co.uk/Future-Fusion-Energy-Popular-Science/dp/1786345420 https://www.amazon.co.uk/Future-Fusion-Energy-Popular-Scienc... The authors argue that ITER will get there and it's a matter of time, funding, and politics. SPARC might be able to get there around roughly the same time. Neither will be hooked up to the grid, but they will demonstrate the tech needed to make a viable fusion power plant. Unfortunately none of the other exciting fusion projects out there will be able to get off the ground due to fairly fundamental limitations. If you ignore any tedious jokes about when fusion power will be ready, and assume it will be ready in a few decades, it's still a process that converts reasonable quantities of seawater into power, with no CO2 emissions, and is relatively safe compared to fission. It won't be ready in time to reduce emissions enough to prevent catastrophic climate change. However, it can be ready soon enough to power the devices we'll need to sequester CO2 from the atmosphere once we've reduced our emissions to the point of diminishing returns. After the concept has been demonstrated, there's plenty of scope for improvement which will make it better and cheaper. On the other hand, the price of oil will increase as emissions taxes are introduced (I hesitate to say that we'll run out of reserves). There's a lot more mileage in fission technology that what's commonly deployed for power, but the new types of reactors needed make it far easier to produce weapons(). Also, although fission technology is mature and safe, the human factors around it are not, which will still lead to accidents, contamination, and deliberate theft. () Fusion reactors would also make it possible to breed fissile material since they are a neutron source but it would be slower and easy to detect.

scanny 5y ago

> Modern fission plants are totally safe. Nuclear waste is basically a non-problem Just removing that as part of the rhetoric around the tech makes fusion invaluable.

d_theorist 5y ago
That is true actually. Seems silly but it's actually a serious benefit! The main issue with fission is that people have become irrational about it. Maybe we get a fresh start with fusion.
- civilized 5y ago
  Unfortunately, a lot of the same environmental interest groups that halted the scaling up of fission also hate fusion. It's best to think of fusion as a way to generate effectively unlimited amounts of energy, kicking in 50-100 years from today. This could be super useful for the long-term ambitions of human civilization - energy has been such a hard constraint for so long that people have barely thought about the amazing stuff we could do with an effectively unlimited energy supply. For addressing climate change, it's likely to be too-little-too-late to bank on. But a century from now it'll be nice for cheap fresh water / agriculture / climate control anywhere on this planet, space elevators, interplanetary/interstellar travel, terraforming, cheap fresh water / agriculture / climate control on other planets, etc. This sort of stuff is incredibly energy-hungry and it's unlikely that renewables will be able to supply the requirements alone. (It'd be awesome if one of the private fusion start-ups gets us there a lot faster, but this is what I'm projecting for now!)
  - simiones 5y ago
    > generate effectively unlimited amounts of energy I don't understand where this concept is coming from. The best ever fusion power experiments so far have not even produced 1 miliwatt net electrical power. ITER, if it succeeds in its 30 year timeline, will not be even close to engineering breakeven (net power generation) - they estimate 0.57 output power/input power ratio - with DEMO hoping to break even 20 years later. Why is there this bizarre idea that we'll jump from <massive effort to get even one miliwatt> to <unlimited power> with fusion?
    - arcanon 5y ago
      It’s not unlimited power, it’s unlimited fuel. The hype is coming from REBCO tape magnets which aren’t in ITER. Many consider ITER to already be obsolete. This is like how computers used to take up whole rooms in the 50s but later could sit in the corner. Fusion takes up whole buildings (ITER) but the MIT ppl proved a magnet so that it can fit in just a room. As our magnets get stronger the tokamaks can get smaller. Room sized tokamak is manageable for commercialization. Commonwealth Fusion Systems has a pretty clear path it seems.
    - civilized 5y ago
      There's a nearby fusion reactor that generates quite a lot of power. You may have heard of it. Jokes aside, fusion would provide way more energy per fuel mass than any other source if we could only contain sufficiently hot plasma. Better magnets may be the key, as the other comment alludes.
simiones 5y ago
But it's not true. Fusion power plants produce a steady stream of radioactive waste from the neutron bombardment. They can leak radioactive tritium. They can explode, spewing hot plasma and chunks of radioactive reactor walls in the area around the plant. The scope of the problem is nowhere near a fission reactor meltdown, but it's also not "gone".

leephillips 5y ago

It is not worth investing money in, because it will never supply grid power: http://progressive.org/op-eds/let-cut-our-losses-on-fusion-energy-180313/ http://progressive.org/op-eds/let-cut-our-losses-on-fusion-e... Here is another physicist warning about the hype just a few days ago: http://backreaction.blogspot.com/2021/10/how-close-is-nuclear-fusion-power.html http://backreaction.blogspot.com/2021/10/how-close-is-nuclea...

ip26 5y ago
It receives a pretty small level of funding, so I'm not quite sure there are many losses to cut. $2.2bn over 5 years is about $1.50 per person per year. It's comparable to the funding for the CPB.
- leephillips 5y ago
  It’s not much compared with some other budget items, you’re right. But a billion here, a billion there, and soon you’re talking about real money.
- simonh 5y ago
  ITER will cost about the same as the Manhattan project, around $21bn in 2021 $, and that's just one project. Total investment in Fusion globally is huge and the problem is at the moment there are multiple different feasible ways forward, and it's not clear which will pan out. There's huge risk of wasting large amounts of resources and time, even if we do eventually figure it out.
  - willis936 5y ago
    Creating conditions to split a heavy nucleus for 1 microsecond is much easier to do than fusing light nuclei steady state.
    - simonh 5y ago
      Yes of course, I know that. I’m not even saying the investment in fusion is a bad idea. I’m just pointing out that actually our investment in it is enormous and very risky.

skywal_l 5y ago

Don't you think that the fact that you can use sea water as input and you get hydrogen as output is a huge advantage over fission? Add to that the fact that there is no fukushima style meltdown in a fusion power plant. If something goes wrong, it just stops. Finally, contrary to fission, fusion power plants will be able to adjust their power output as fast as gaz power plants. It takes months to turn on or off a fission power plant. So yes, there is definitely a few benefits to fusion. And take a step back on the numbers. Look at how much we injected in banks in 2008. If it works (and indeed there is a risk they won't make it work and this is probably where the argument should be) the investment would be amortize over thousands of years... Can you imaging a guy, 3000 years ago in China, complaining about spending money on a kiln to smelt that thing called iron?...

soperj 5y ago
>Add to that the fact that there is no fukushima style meltdown in a fusion power plant. If something goes wrong, it just stops. That's already the case with the CANDU reactors. They also don't need upgraded uranium, and can use uranium from decommissioned nuclear weapons.
d_theorist 5y ago
>Don't you think that the fact that you can use sea water as input and you get hydrogen as output is a huge advantage over fission? If it reduces the cost. But it doesn't seem to. >Add to that the fact that there is no fukushima style meltdown in a fusion power plant. If something goes wrong, it just stops. Same as the most recent fission plants.
- flavius29663 5y ago
  > Same as the most recent fission plants. How are these 2 things the same? On one hand, you rely on a good design and execution to achieve an automatic stop. History has shown time and again that there will always be something that goes wrong: from the cracking rods of Chernobyl to the backup power at Fukushima. On the other, if you don't design and execute perfectly, nothing works, so there is nothing to shut down. This is the definition of "fail safe". It's like saying both a meteorite and a rocket will reach 500km/h in the atmosphere, but me it's pretty obvious one is much more likely to do so.

tambourine_man 5y ago

>Modern fission plants are totally safe. Nuclear waste is basically a non-problem, especially with the most recent technology Please elaborate on both. And I think we can all agree there's no such thing as totally safe, only risk management.

orwin 5y ago
Gen2, even with weird designs (so Fukushima included) are individually safer than any coal plant ever built, and the whole generation will kill less people, even counting those dying in a shameful, unprepared evacuation, that the new "clean coal" plants (with flue gas discharge) built in the western world since the 2000s. Not taking into account the GHG emissions. Number of death/GW is in the favor of nuclear for any power station, even when counting dislodged people as "dead" (in this case, hydro is actually the 2nd most deadly) For the nuclear wast beeing a non-problem: i don't agree, but i understand where he is coming from. There is basically 3 type of nuclear waste: low-activity waste is waste that we could ignore, and the most present. radioactivity levels are what is find in granitic area. Often indirectly contaminated materials, or very long-lived isotope (radioactive decay is long, the the material is not very radioactive). It can still be dangerous and create radon gas if poorly stored (as do caves in granitic areas). We have no good answer to that. Maybe separate long=lived isotopes from the rest, store it, and reuse the contaminated materials after waiting a dozen years, mixing it with new cement or something. intermediate-activity waste: still extremely dangerous, its often contaminated material (filter, pipes), or active (and dangerous) isotopes, with a half-life of up 500 years (i think the most present have an half-life of 200 years, and you need 10 cycles basically to be rid of it). Those are not direct fission byproduct (i don't think so, i don't remember exactly, maybe a small number is?). High-activity waste: This is the real dangerous stuff. Those can stay hot for years. There is to kind: - direct fission byproducts. Some degrade not in stable isotopes, but in the intermediate-activity waste, so even with a short half-life, they take as long as the intermediate ones to get rid of (since they degrade into it. If i'm over-explaining, sorry). Some degrade into stable heavy metals that also poison the environment, in a different way. - transuranic elements. The graphite from Chernobyl could be counted in this category? (not sure, if an expert is here, can you infirm this?). I do not exactly understand this category, but its basically elements from the reactor core that are not fission products. The reason why GP said "Nuclear waste is basically a non-problem" might be because we are able to re-use some the fission products, and to deactivate the rest. Both technologies are at an experimental stage, the first one could be in commercial use in the decade if China doesn't fail. And since the fission product decay is what's create the most troublesome waste (half-life between 100 and 500 years mean the wast stay dangerous for between 1000 and 5000 years), its a "non-problem". I don't have the material on hand, i learned that in 2019. i could find it again if you wanted (probably mostly be in French, sorry), and to be fair, i might have oversimplified things i did not understand in the first place.

c7DJTLrn 5y ago

>Modern fission plants are totally safe Ha what? The number of flaws in any system is unknowable. We thought the Fukushima Daiichi reactors were safe and then what happened? Meltdown because the backup generators were flooded. That statement transposed to software engineering is like saying "we use Kubernetes so we have 24/7 uptime".

nobody9999 5y ago

>What's the big benefit of fusion that makes it worth investing so much money? 4-20 times the energy density of fissionable materials[0] and fuel that's the most common element in the universe. [0] https://en.wikipedia.org/wiki/Energy_density#In_nuclear_reactions https://en.wikipedia.org/wiki/Energy_density#In_nuclear_reac...

d_theorist 5y ago
And what is the benefit of that?
- nobody9999 5y ago
  >And what is the benefit of that? I'll leave that as an (fairly obvious) exercise for you, dear reader.

goodpoint 5y ago

> Modern fission plants are totally safe Unless there's a war. Unless corruption leads to poor management of the plants. Unless nuclear waste is mismanaged. Unless there is an earthquake or tsunami of completely unexpected intensity.

mzs 5y ago
or corrosion of containment vessel, or an airplane strike… http://green.blogs.nytimes.com/2010/04/21/critics-challenge-safety-of-new-nuclear-reactor-design/ http://green.blogs.nytimes.com/2010/04/21/critics-challenge-...
orwin 5y ago
> Unless there's a war. Unless corruption leads to poor management of the plants. Unless nuclear waste is mismanaged. Unless there is an earthquake or tsunami of completely unexpected intensity. No for mismanagement, earthquake or tsunami, the gen3 are completely safe, all security mesures are passives, unless the fault is directly on the core, it will fail gracefully. Irradiated water might leak, but to be fair, underground water in granitic areas are more irradiated than the fission product pool. Issues are war (and in this case, direct sabotage from an actor with actual knowledge, or a direct hit into a functioning reactor, so pretty much on purpose strike. I wouldn't be afraid of terrorism) and waste.

cantagi 5y ago

Since a commercial fusion reactor hasn't yet been developed, you can't argue that it is or will be the same cost per-megawatt as fission power. That's because you can't predict any advances in technology that make fusion easier or reduce the capital cost. Based on a HN recommendation, I read this book: https://www.amazon.co.uk/Future-Fusion-Energy-Popular-Science/dp/1786345420 https://www.amazon.co.uk/Future-Fusion-Energy-Popular-Scienc... The authors argue that ITER will get there and it's a matter of time, funding, and politics. SPARC might be able to get there around roughly the same time. Neither will be hooked up to the grid, but they will demonstrate the tech needed to make a viable fusion power plant. Unfortunately none of the other exciting fusion projects out there will be able to get off the ground due to fairly fundamental limitations. If you ignore any tedious jokes about when fusion power will be ready, and assume it will be ready in a few decades, it's still a process that converts reasonable quantities of seawater into power, with no CO2 emissions, and is relatively safe compared to fission. It won't be ready in time to reduce emissions enough to prevent catastrophic climate change. However, it can be ready soon enough to power the devices we'll need to sequester CO2 from the atmosphere once we've reduced our emissions to the point of diminishing returns. After the concept has been demonstrated, there's plenty of scope for improvement which will make it better and cheaper. On the other hand, the price of oil will increase as emissions taxes are introduced (I hesitate to say that we'll run out of reserves). There's a lot more mileage in fission technology that what's commonly deployed for power, but the new types of reactors needed make it far easier to produce weapons(). Also, although fission technology is mature and safe, the human factors around it are not, which will still lead to accidents, contamination, and deliberate theft. () Fusion reactors would also make it possible to breed fissile material since they are a neutron source but it would be slower and easy to detect.