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Firstly heat from inefficient low temperature solid-fuel reactors can't be used directly for many applications. So consider electricity. Cars/planes/kitchen-sto

Firstly heat from inefficient low temperature solid-fuel reactors can't be used directly for many applications. So consider electricity. Cars/planes/kitchen-stoves cant use uranium or nuclear heat!! All 4.5 billion tons can't be extratcted. More we extract, concentration decreases and harder it gets. I keep asking this question: If seawater extraction of metals is practical, why aren't we extracting other costly metals now? https://twitter.com/AchalHP/status/1011661441412337665 https://twitter.com/AchalHP/status/1011661441412337665

acidburnNSA 7y ago
Don't confuse solid fuel with traditional light water reactors. The highest temperature reactors are triso fueled helium cooled solid fuel reactors like HTTR with outlet temperatures over 1000C. Also, fast breeder reactors with solid fuel are just as sustainable as any fluid fuel breeder. Molten salt is one of about a dozen advanced reactor techs that has huge potential. Hard part is economics. Hazardous coolant has been a pain to maintain cheaply so far. Also seawater uranium replenishes from erosion and plate tectonics so it will effectively never decrease in concentration, even if we pull it out at world scale. http://large.stanford.edu/publications/coal/references/docs/pad11983cohen.pdf http://large.stanford.edu/publications/coal/references/docs/...
- achalhp 7y ago
  The successor of LWR/HWR should be a fluid-fuel reactor. Once we setup a pebble/advanced fuel making factory, closing it will takes decades (because people may lose jobs) and the new solid-fuel factory will again pause nuclear innovation for another 100 years. The only way to continuously improve nuclear reactors is to go fluid-fuel. No engineered fuel, so no job loses. Reactor innovation is independent of fuel factory. Nuclear fuel becomes a commodity instead of engineered speciality. Example: MSRE ran U235 and U233 without any modification. Secondly, solid fuel reactors throw away fuel along with heat exchange surfaces (clad). Fuel also undergoes crystal structure degradation along with other solid structures. Maybe there is enough fuel in the seawater, but there may not be enough places suitable for geological repositories. Solid-fuel reactors always need excess reactivity reserve. Always needs control rods, and if someone (or a bad actor) pulls all the control rods, reactor gets supercritical. Needs highly skilled people and needs security. For emergency shutdown of solid-fuel reactor, poison is added to coolant, not fuel. In an emergency, poison is added to the liquid-fuel, permanently destroying the fuel. Emergency can be anything, from a natural disaster to terrorist attack. Fluid-fuel reactors offer unbeatable safety features against anything.
- achalhp 7y ago
  Highest temperature fission reactors are the gas core (vapor core) and ion core reactors. They are fluid-fuel reactors, but not demonstrated. Currently solid-fuel reactors hold the record for highest temperatures. Fusion reactor runs hotter and again fuel is in fluid state.(Fluid: Liquid, gas & plasma.). But only runs for 10-100 minutes. Demonstrated fission reactors run for thousands of hours continuously.
PopeDotNinja 7y ago
One could make a pedantic argument that a battery powered anything can use nuclear, but I agree with your point.
- dredmorbius 7y ago
  There's no likelihood of batteries scaling to certain uses, such as large long-distance air transport, or marine shipping. Most trucking as well. We either stop using those transport modes, or revert to prior forms (wind), or wire-based electrical systems (rail, canals, trucks).
  - wffurr 7y ago
    Or make fuel. There are all sorts of ways to make carbon neutral diesel and jet fuel. They just aren't economic compared to pumping it out of the ground unless the externalities of burning virgin fuels are priced in with regulation.
    - dredmorbius 7y ago
      Good point. I've been excited by fuel synthesis technologies, though they've proved difficult to develop at scale. A Google X Project tried and failed.
philipkglass 7y ago
The most optimistic cost projection I can easily find for seawater uranium extraction goes as low as $360 per kilogram of uranium. https://inis.iaea.org/collection/NCLCollectionStore/_Public/48/039/48039446.pdf?r=1&r=1 https://inis.iaea.org/collection/NCLCollectionStore/_Public/... If extracting gold is only 300 times harder, that puts the lower bound cost at $108,000 per kilogram of gold. That's significantly more expensive than the market price of gold. Indeed, extracting uranium itself from seawater is not cost competitive with conventional terrestrial mining at present. But the process has been demonstrated on a technical level. Either terrestrial uranium deposits will have to get closer to exhaustion or seawater extraction will have to be much more cost optimized (or both) before seawater extraction of uranium is economically competitive. I was only addressing your technical claims about the exhaustion of seawater uranium, not making economic claims.
- achalhp 7y ago
  You included my sentence: "Efficiency really matters when we have >1000 GW of installed nuclear capacity." I wanted to address that: efficiency matters. Inefficient technologies will hit some constraints if not others. We may run out of time: A pressure vessel production cycle is over one year[1]. By the time we reach >1000GW someone may make fusion practical or China's competent nuclear industry may start selling MSRs to everyone. We may run out of highly skilled people required to build and operate these complex machines. The safety is highly dependent on operations and management throughout the life cycle of complex machines. From manufacturing to operations there is tiny margins for error. (Not a physical constraint.) LWR technology is associated with military ships and submarines, no one shares it. Few countries control the technology and there are only a few places in the world to make pressure vessels. (Not a physical constraint.) We may run out of waste disposal sites. A geological repository needs special rock formations away from earthquake zones. The article is written by a nuclear industry professional who tells that routine things done by the nuclear industry today when applied to MSR is a "disadvantage". They open the lid of an LWR every 18 months and replace/shuffle highly radioactive fuel assemblies and say that it is a disadvantage for them to replace graphite. That is totally unfair. [1] VVER pressure vessel production cycle needs 3 years. https://www.youtube.com/watch?v=91yVhrSZ5jQ https://www.youtube.com/watch?v=91yVhrSZ5jQ NuScale pressure vessel R&D: https://www.energy.gov/sites/prod/files/2016/10/f34/02%20-%20EPRI%20SMR%20Reactor%20Vessel%20Manufacture-Fabrication-Demonstration%20Project_0.pdf https://www.energy.gov/sites/prod/files/2016/10/f34/02%20-%2... TL;DR Even small pressure vessels (used by nuscale) have lead times of about a year. A megafactory can build like 1 or 2 vessel per month. At 1.5GW/year/factory, we need like 22 factories to keep up with the production schedule if we need to reach 1000 GW of small-LWR capacity within, say 2050.

acidburnNSA 7y ago

Don't confuse solid fuel with traditional light water reactors. The highest temperature reactors are triso fueled helium cooled solid fuel reactors like HTTR with outlet temperatures over 1000C. Also, fast breeder reactors with solid fuel are just as sustainable as any fluid fuel breeder. Molten salt is one of about a dozen advanced reactor techs that has huge potential. Hard part is economics. Hazardous coolant has been a pain to maintain cheaply so far. Also seawater uranium replenishes from erosion and plate tectonics so it will effectively never decrease in concentration, even if we pull it out at world scale. http://large.stanford.edu/publications/coal/references/docs/pad11983cohen.pdf http://large.stanford.edu/publications/coal/references/docs/...

achalhp 7y ago
The successor of LWR/HWR should be a fluid-fuel reactor. Once we setup a pebble/advanced fuel making factory, closing it will takes decades (because people may lose jobs) and the new solid-fuel factory will again pause nuclear innovation for another 100 years. The only way to continuously improve nuclear reactors is to go fluid-fuel. No engineered fuel, so no job loses. Reactor innovation is independent of fuel factory. Nuclear fuel becomes a commodity instead of engineered speciality. Example: MSRE ran U235 and U233 without any modification. Secondly, solid fuel reactors throw away fuel along with heat exchange surfaces (clad). Fuel also undergoes crystal structure degradation along with other solid structures. Maybe there is enough fuel in the seawater, but there may not be enough places suitable for geological repositories. Solid-fuel reactors always need excess reactivity reserve. Always needs control rods, and if someone (or a bad actor) pulls all the control rods, reactor gets supercritical. Needs highly skilled people and needs security. For emergency shutdown of solid-fuel reactor, poison is added to coolant, not fuel. In an emergency, poison is added to the liquid-fuel, permanently destroying the fuel. Emergency can be anything, from a natural disaster to terrorist attack. Fluid-fuel reactors offer unbeatable safety features against anything.
achalhp 7y ago
Highest temperature fission reactors are the gas core (vapor core) and ion core reactors. They are fluid-fuel reactors, but not demonstrated. Currently solid-fuel reactors hold the record for highest temperatures. Fusion reactor runs hotter and again fuel is in fluid state.(Fluid: Liquid, gas & plasma.). But only runs for 10-100 minutes. Demonstrated fission reactors run for thousands of hours continuously.

PopeDotNinja 7y ago

One could make a pedantic argument that a battery powered anything can use nuclear, but I agree with your point.

dredmorbius 7y ago
There's no likelihood of batteries scaling to certain uses, such as large long-distance air transport, or marine shipping. Most trucking as well. We either stop using those transport modes, or revert to prior forms (wind), or wire-based electrical systems (rail, canals, trucks).
- wffurr 7y ago
  Or make fuel. There are all sorts of ways to make carbon neutral diesel and jet fuel. They just aren't economic compared to pumping it out of the ground unless the externalities of burning virgin fuels are priced in with regulation.
  - dredmorbius 7y ago
    Good point. I've been excited by fuel synthesis technologies, though they've proved difficult to develop at scale. A Google X Project tried and failed.

philipkglass 7y ago

The most optimistic cost projection I can easily find for seawater uranium extraction goes as low as $360 per kilogram of uranium. https://inis.iaea.org/collection/NCLCollectionStore/_Public/48/039/48039446.pdf?r=1&r=1 https://inis.iaea.org/collection/NCLCollectionStore/_Public/... If extracting gold is only 300 times harder, that puts the lower bound cost at $108,000 per kilogram of gold. That's significantly more expensive than the market price of gold. Indeed, extracting uranium itself from seawater is not cost competitive with conventional terrestrial mining at present. But the process has been demonstrated on a technical level. Either terrestrial uranium deposits will have to get closer to exhaustion or seawater extraction will have to be much more cost optimized (or both) before seawater extraction of uranium is economically competitive. I was only addressing your technical claims about the exhaustion of seawater uranium, not making economic claims.

achalhp 7y ago
You included my sentence: "Efficiency really matters when we have >1000 GW of installed nuclear capacity." I wanted to address that: efficiency matters. Inefficient technologies will hit some constraints if not others. We may run out of time: A pressure vessel production cycle is over one year[1]. By the time we reach >1000GW someone may make fusion practical or China's competent nuclear industry may start selling MSRs to everyone. We may run out of highly skilled people required to build and operate these complex machines. The safety is highly dependent on operations and management throughout the life cycle of complex machines. From manufacturing to operations there is tiny margins for error. (Not a physical constraint.) LWR technology is associated with military ships and submarines, no one shares it. Few countries control the technology and there are only a few places in the world to make pressure vessels. (Not a physical constraint.) We may run out of waste disposal sites. A geological repository needs special rock formations away from earthquake zones. The article is written by a nuclear industry professional who tells that routine things done by the nuclear industry today when applied to MSR is a "disadvantage". They open the lid of an LWR every 18 months and replace/shuffle highly radioactive fuel assemblies and say that it is a disadvantage for them to replace graphite. That is totally unfair. [1] VVER pressure vessel production cycle needs 3 years. https://www.youtube.com/watch?v=91yVhrSZ5jQ https://www.youtube.com/watch?v=91yVhrSZ5jQ NuScale pressure vessel R&D: https://www.energy.gov/sites/prod/files/2016/10/f34/02%20-%20EPRI%20SMR%20Reactor%20Vessel%20Manufacture-Fabrication-Demonstration%20Project_0.pdf https://www.energy.gov/sites/prod/files/2016/10/f34/02%20-%2... TL;DR Even small pressure vessels (used by nuscale) have lead times of about a year. A megafactory can build like 1 or 2 vessel per month. At 1.5GW/year/factory, we need like 22 factories to keep up with the production schedule if we need to reach 1000 GW of small-LWR capacity within, say 2050.