3 ms·

You're not just saving on fuel, you're saving on waste

tlb 7y ago
And safety. Fusion has the enormous advantage that you can just switch it off, without the core continuing to generate heat and causing a meltdown if the cooling system fails. 0.5 MW capacity costs around $1M with solar, so if 0.5 MW of fusion power takes up a cubic meter that doesn't seem like a deal breaker.
- pfdietz 7y ago
  The argument involves the comparison with fission. The low power density means it's going to be more expensive than fission, and fission already fails economically. The difference between fission and solar is that solar lacks many systems (like, turbines and generators) that fission and fusion would need. More fundamentally, solar is distributed (even on a large solar farm), so there's a lack of coupling between elements that makes everything easy to assemble and very fault tolerant. In fission and fusion plants, the intricate dependencies mean everything has to be highly reliable. Safety (for fission) and the extreme difficulty of repair of activated structures (for fusion) also drive this very expensive reliability.
  - bassman9000 7y ago
    The argument involves the comparison with fission. With the current LWR/HWR fission reactors, where core is solid.
- nine_k 7y ago
  > switch it off, without the core continuing to generate heat and causing a meltdown A number of fission designs have this property, too. Most operational fission reactors are from 1960s to 1980s, and indeed are capable of a meltdown.
  - pfdietz 7y ago
    And if one were allowed to design a fission core with a power density as low as a fusion core, it could also be made highly resistant to meltdown, because it would have so much more thermal inertia. One might ask why fission reactors are not designed that way.
acidburnNSA 7y ago
Technically true, but not in the way a casual reader may think. The storage and ultimate disposal of spent nuclear fuel (i.e. "nuclear waste") is a small fraction of the overall cost of the nuclear power enterprise. The Nuclear Waste Fund has been accumulating capital from rate-payers for years and has about $50B in it in the USA, from ~100 operating plants that have sold ~$1T of electricity in their lifetimes. It's the short-term handling of fission products (that eventually cool off and become nuclear waste) that makes fission expensive. Since fusion products are much less radioactive than fission products, fusion has a major advantage over fission in terms of worrying about containing radioactive material. To contain it in fission reactors, we have lots of redundant cooling systems, control systems, instruments. We have a powerful regulator checking everything, and requesting major changes. We have teams of people planning maintenance work to minimize dose to the workers. We have big 50km radius emergency planning zones with sirens and drills and all that. Nuclear fusion is the dream energy source because it has all the positive elements of fission (24/7, zero-carbon, can build anywhere, tiny fuel requirements b/c nuclear) without the major downside of radioactive fission products and transuranics. I got into the nuclear industry specifically to help solve climate change with fusion, but I got distracted by advanced Gen-IV fission reactors for now, assuming they'd be shorter-term developments. Fusion is still the dream though, for sure.
- pfdietz 7y ago
  The major downside of fission isn't fission products or transuranics. Would that those were! The major downside of fission is that it's too expensive. Fusion would take this, THE showstopper for fission, and make it worse. It's an example of not focusing your problem solving on the actual problem.
  - acidburnNSA 7y ago
    Cost is the proximal issue, but why? My claim is that if the fission products and TRU were not radioactive it would not be expensive. This point is pretty easy to argue, as most cost ratcheting has been related to protecting against radiation hazards. Fusion products are far less radioactive but the engineering to get to the proper physical conditions is very hard and expensive. Fission is the opposite. Trivial to get fission chain reactions given the material (done in 1942 by Enrico Fermi with natural uranium), expensive to deal with radiation. Fresh fission products will always be radioactive, that problem isn't going away easily. Engineering challenges of fusion could possibly be solved by good engineering and fancy materials. That's a lot easier to postulate. Thus, fusion remains a potentially-attainable dream.
bassman9000 7y ago
MSR/LFTR are fission, produce a fraction of the waste, and would require a fraction of the investment to make them market ready. Don't get me wrong, happy to see fusion advancing. But we need lots of power, today, market-ready, outside the lab. No, not the US or Europe. China, India, Africa. They want to grow, now, and we don't want them to use coal/oil, nor outdated PWR/LWR/HWR. If fusion is 20y and $1T away, and we can have hundreds of MSR/LFTR 1GWe plants by investing $1B over 10y years, desalinating water, making aviation fuel out of sea water, and recycling fission waste from older reactors, I'd stick with fission for now.

tlb 7y ago

And safety. Fusion has the enormous advantage that you can just switch it off, without the core continuing to generate heat and causing a meltdown if the cooling system fails. 0.5 MW capacity costs around $1M with solar, so if 0.5 MW of fusion power takes up a cubic meter that doesn't seem like a deal breaker.

pfdietz 7y ago
The argument involves the comparison with fission. The low power density means it's going to be more expensive than fission, and fission already fails economically. The difference between fission and solar is that solar lacks many systems (like, turbines and generators) that fission and fusion would need. More fundamentally, solar is distributed (even on a large solar farm), so there's a lack of coupling between elements that makes everything easy to assemble and very fault tolerant. In fission and fusion plants, the intricate dependencies mean everything has to be highly reliable. Safety (for fission) and the extreme difficulty of repair of activated structures (for fusion) also drive this very expensive reliability.
- bassman9000 7y ago
  The argument involves the comparison with fission. With the current LWR/HWR fission reactors, where core is solid.
nine_k 7y ago
> switch it off, without the core continuing to generate heat and causing a meltdown A number of fission designs have this property, too. Most operational fission reactors are from 1960s to 1980s, and indeed are capable of a meltdown.
- pfdietz 7y ago
  And if one were allowed to design a fission core with a power density as low as a fusion core, it could also be made highly resistant to meltdown, because it would have so much more thermal inertia. One might ask why fission reactors are not designed that way.

acidburnNSA 7y ago

Technically true, but not in the way a casual reader may think. The storage and ultimate disposal of spent nuclear fuel (i.e. "nuclear waste") is a small fraction of the overall cost of the nuclear power enterprise. The Nuclear Waste Fund has been accumulating capital from rate-payers for years and has about $50B in it in the USA, from ~100 operating plants that have sold ~$1T of electricity in their lifetimes. It's the short-term handling of fission products (that eventually cool off and become nuclear waste) that makes fission expensive. Since fusion products are much less radioactive than fission products, fusion has a major advantage over fission in terms of worrying about containing radioactive material. To contain it in fission reactors, we have lots of redundant cooling systems, control systems, instruments. We have a powerful regulator checking everything, and requesting major changes. We have teams of people planning maintenance work to minimize dose to the workers. We have big 50km radius emergency planning zones with sirens and drills and all that. Nuclear fusion is the dream energy source because it has all the positive elements of fission (24/7, zero-carbon, can build anywhere, tiny fuel requirements b/c nuclear) without the major downside of radioactive fission products and transuranics. I got into the nuclear industry specifically to help solve climate change with fusion, but I got distracted by advanced Gen-IV fission reactors for now, assuming they'd be shorter-term developments. Fusion is still the dream though, for sure.

pfdietz 7y ago
The major downside of fission isn't fission products or transuranics. Would that those were! The major downside of fission is that it's too expensive. Fusion would take this, THE showstopper for fission, and make it worse. It's an example of not focusing your problem solving on the actual problem.
- acidburnNSA 7y ago
  Cost is the proximal issue, but why? My claim is that if the fission products and TRU were not radioactive it would not be expensive. This point is pretty easy to argue, as most cost ratcheting has been related to protecting against radiation hazards. Fusion products are far less radioactive but the engineering to get to the proper physical conditions is very hard and expensive. Fission is the opposite. Trivial to get fission chain reactions given the material (done in 1942 by Enrico Fermi with natural uranium), expensive to deal with radiation. Fresh fission products will always be radioactive, that problem isn't going away easily. Engineering challenges of fusion could possibly be solved by good engineering and fancy materials. That's a lot easier to postulate. Thus, fusion remains a potentially-attainable dream.

bassman9000 7y ago

MSR/LFTR are fission, produce a fraction of the waste, and would require a fraction of the investment to make them market ready. Don't get me wrong, happy to see fusion advancing. But we need lots of power, today, market-ready, outside the lab. No, not the US or Europe. China, India, Africa. They want to grow, now, and we don't want them to use coal/oil, nor outdated PWR/LWR/HWR. If fusion is 20y and $1T away, and we can have hundreds of MSR/LFTR 1GWe plants by investing $1B over 10y years, desalinating water, making aviation fuel out of sea water, and recycling fission waste from older reactors, I'd stick with fission for now.