4 ms·

I have personally taken a tour of the NIF at Livermore. The guide was an old hand, who constantly remarked about the efforts of NIF towards "stockpile stewardsh

I have personally taken a tour of the NIF at Livermore. The guide was an old hand, who constantly remarked about the efforts of NIF towards "stockpile stewardship," ie the maintenance of the US arsenal of nuclear weapons. It seemed like NIF was all about the stockpile stewardship first, and fusion research was a secondary consideration. The capability of the NIF to get positive energy from the energy that they impart on the Hohlraum itself is neat, but I constantly discount any milestones that Livermore/NIF report, because the inertial confinement approach has such higher barriers to commercialization than tokamak style approaches, that I just consign it to "boondoggle" in my head. Yeah, the lasers could be 20x more efficient, and yeah, they probably could figure out how to pump 10s of targets into the chamber per second, but the energy extraction is just completely missing from the considerations. The engineering challenges are a whole 'nother level for NIF, a big barrier to usability.

DennisP 4y ago
Seems like energy extraction would be similar to other D-T designs: surround the reaction chamber with molten FLiBe or lead-lithium and run some coolant pipes through it.
- uplifter 4y ago
  > surround the reaction chamber with molten FLiBe or lead-lithium So manufacturing fusion reactors would use a lot of lithium, which is already in short supply. That would be an interesting complication with the demand of lithium for electric vehicle batteries. Maybe the Li supply situation will be eased by then.
  - Schroedingersat 4y ago
    The quantity of lithium required is miniscule, but would require a fair bit of enrichment to eliminate the Li-6. The limiting resource is the inner wall for which no known material other than double the annual world production beryllium is even close to sufficient
rawgabbit 4y ago
What is your opinion of ITER? https://edition.cnn.com/interactive/2022/05/world/iter-nuclear-fusion-climate-intl-cnnphotos/ https://edition.cnn.com/interactive/2022/05/world/iter-nucle...
- TaylorAlexander 4y ago
  Personally my money is on SPARC as a demo plant and its planned successor ARC as a commercial power plant prototype. Unlike ITER these systems use high field strength superconducting magnets, which directly translates to a much smaller machine for the same energy gain. Because of the smaller machine size, it can be built much faster than ITER. The company building SPARC plans to achieve first fusion around the same time as ITER, and since their machines are smaller, they should be able to move faster. That said ITER will be fantastically useful for proving a lot of science, and I am happy we have so many viable fusion projects in the works. https://cfs.energy/news-and-media/new-scientific-papers-predict-historic-results-for/ https://cfs.energy/news-and-media/new-scientific-papers-pred...
  - pfdietz 4y ago
    ARC's volumetric power density is just 40x worse than a PWR's reactor vessel, vs. 400x worse for ITER. Neither appears to be on a route to an economical power plant.
    - TaylorAlexander 4y ago
      I’m not sure I follow, but you’re saying the power plants are very large relative to their power output, and this size correlates to cost, thus making them so expensive that they are not economical? You’re probably right, but I guess what I’m saying is that we’ve never had a fusion power plant that produces net energy gain at any cost. I believe SPARC is on the path to doing so. It will still take a long time to make fusion actually affordable. For what it’s worth I am a huge advocate of wind and solar power. But fusion is neat and I’m excited for us to get to a point where we actually have sustained Q total greater than 1.
floxy 4y ago
I'm a complete layman when it comes to ICF, but I'm assuming that there is a scaling factor between surface area and volume that would eventually help here? As in, the lasers initiate fusion on the surface of the fuel pellet, which propagates the fusion into the interior of the pellet in a chain reaction / positive feedback kind of way. So that if you increased the surface area of the pellet by a factor of 10, you'd get 100 times more total output energy (since there is 100 times more mass in a pellet with 10 times the surface area). So you'd need 10 times the current input power, but would get 100 times the output power.
- leephillips 4y ago
  That won’t work, I don’t think. You can’t make the pellets much larger because laser nonuniformities and hydrodynamic instabilities will kill the implosion; there will be no fusion at all. But that’s not a problem, you see, because in a commercial reactor you’ll have a pellet factory making the required one million targets per day, and they will be injected into the chamber 10 times per second, with practically no down time. And each shot will have gain > 100 to get net energy out.
  - b33j0r 4y ago
    That’s pretty much what this design would require for continuous operation. But I cannot tell if this comment is being facetious or rather optimistic. Therefore, I’ll agree!

DennisP 4y ago

Seems like energy extraction would be similar to other D-T designs: surround the reaction chamber with molten FLiBe or lead-lithium and run some coolant pipes through it.

uplifter 4y ago
> surround the reaction chamber with molten FLiBe or lead-lithium So manufacturing fusion reactors would use a lot of lithium, which is already in short supply. That would be an interesting complication with the demand of lithium for electric vehicle batteries. Maybe the Li supply situation will be eased by then.
- Schroedingersat 4y ago
  The quantity of lithium required is miniscule, but would require a fair bit of enrichment to eliminate the Li-6. The limiting resource is the inner wall for which no known material other than double the annual world production beryllium is even close to sufficient

rawgabbit 4y ago

What is your opinion of ITER? https://edition.cnn.com/interactive/2022/05/world/iter-nuclear-fusion-climate-intl-cnnphotos/ https://edition.cnn.com/interactive/2022/05/world/iter-nucle...

TaylorAlexander 4y ago
Personally my money is on SPARC as a demo plant and its planned successor ARC as a commercial power plant prototype. Unlike ITER these systems use high field strength superconducting magnets, which directly translates to a much smaller machine for the same energy gain. Because of the smaller machine size, it can be built much faster than ITER. The company building SPARC plans to achieve first fusion around the same time as ITER, and since their machines are smaller, they should be able to move faster. That said ITER will be fantastically useful for proving a lot of science, and I am happy we have so many viable fusion projects in the works. https://cfs.energy/news-and-media/new-scientific-papers-predict-historic-results-for/ https://cfs.energy/news-and-media/new-scientific-papers-pred...
- pfdietz 4y ago
  ARC's volumetric power density is just 40x worse than a PWR's reactor vessel, vs. 400x worse for ITER. Neither appears to be on a route to an economical power plant.
  - TaylorAlexander 4y ago
    I’m not sure I follow, but you’re saying the power plants are very large relative to their power output, and this size correlates to cost, thus making them so expensive that they are not economical? You’re probably right, but I guess what I’m saying is that we’ve never had a fusion power plant that produces net energy gain at any cost. I believe SPARC is on the path to doing so. It will still take a long time to make fusion actually affordable. For what it’s worth I am a huge advocate of wind and solar power. But fusion is neat and I’m excited for us to get to a point where we actually have sustained Q total greater than 1.

floxy 4y ago

I'm a complete layman when it comes to ICF, but I'm assuming that there is a scaling factor between surface area and volume that would eventually help here? As in, the lasers initiate fusion on the surface of the fuel pellet, which propagates the fusion into the interior of the pellet in a chain reaction / positive feedback kind of way. So that if you increased the surface area of the pellet by a factor of 10, you'd get 100 times more total output energy (since there is 100 times more mass in a pellet with 10 times the surface area). So you'd need 10 times the current input power, but would get 100 times the output power.

leephillips 4y ago
That won’t work, I don’t think. You can’t make the pellets much larger because laser nonuniformities and hydrodynamic instabilities will kill the implosion; there will be no fusion at all. But that’s not a problem, you see, because in a commercial reactor you’ll have a pellet factory making the required one million targets per day, and they will be injected into the chamber 10 times per second, with practically no down time. And each shot will have gain > 100 to get net energy out.
- b33j0r 4y ago
  That’s pretty much what this design would require for continuous operation. But I cannot tell if this comment is being facetious or rather optimistic. Therefore, I’ll agree!