Major Milestone Reached in race for Fusion

[Borgholio]

After seeing video of people living close to fracking operations lighting their fucking tap water on fire, I'm not inclined to support the process.

[Magis]

One should be careful not to underestimate the challenges facing fusion commercialization or its costs. And "Breaking even" on the energy balance is still very far off.

This announcement concerns only the laser energy absorbed by the target, rather than the total laser energy expended. The next step would be to break even relative to the total laser energy expended. The next step would be to break even on the total energy input to the lasers. Next would be to break even on the recoverable thermal energy deposited in the reaction chamber, and then to break even on the electric output of the steam-driven thermodynamic cycle which is limited to Carnot efficiencies. Oh, and of course, break-even still doesn't actually produce anything.

The material hardware for a fusion plant would be much more expensive than for a fission plant of similar output. For D-T fusion, that Tritium needs to come from somewhere, it's very hazardous to humans and has a relatively short half-life. The current thinking is that a fusion plant will breed Tritium by activating a Lithium layer in the reaction chamber, which only adds to the planet's growing Lithium demands. Personally, I think what's more likely would be fission or accelerator facilities breeding Tritium independently, but there are nuclear proliferation issues related to this.

While it's true that a fusion plant will not create radioactive fission products, there will be an enormous amount of radioactive activation products being generated by the bombardment of high-energy neutrons on the reaction chamber vessel and hardware. Atomic dislocations will necessitate frequent replacement of metal components. These wastes would need to be disassembled, removed from the building and stored in dry storage casks; the total volume of waste is likely to exceed that of fission products.

[Guardsman Bass]

Tokamaks have the same issue of having to remove the reactor vessel every so often because of radioactivity from neutron bombardment, IIRC. It's one of the things that makes me worried about whether fusion that way would be profitable even if we got past all the technical challenges involved in getting self-sustaining fusion. The upside is that they don't stay as radioactive as long as waste from a fission reactor.

I really wish there was more fusion funding in general, so we could try a whole ton of approaches. As is, the only American projects I know about that receive decent funding are the tokamaks, Livermore, and that fusion reactor that Lockheed's people have been working on.

[StarSword]

The slug-absorbed energy is relevant, however. TOKAMAKs at the start also produced less energy than they used up but now thanks to investigation we know that the fusion powerplant is feasible. If there were no positive balance in the first place, this wouldn't even be considered and ITER would not go forward at all. I think the same applies to laser ignition. Positive balance underscores the fact that this is a sound idea, since after that it is a matter of designing a system with desired specifications to actually have an overall energy-positive result. Might be another 50 years, but it's worth it.

Isn't there a joke out there somewhere that practical fusion power has been fifty years away for more than fifty years?

After seeing video of people living close to fracking operations lighting their fucking tap water on fire, I'm not inclined to support the process.

I've seen that video too, and there were stories of flaming faucets in that area of (Pennsylvania?) long before they started fracking there.

Not saying fracking's a good idea, though. Groundwater contamination from the fracking chemicals themselves still worries me. Not to mention the fact that the world's supply of fresh water is limited and you're basically injecting it into the ground with no way of getting it back out.

[Irbis]

Isn't there a joke out there somewhere that practical fusion power has been fifty years away for more than fifty years?

Part of it is the fact that first 20 years western research went into blind alley and it was only once Soviet scientists announced their design is nearly 2 magnitudes more efficient ('tokamak' is from Russian, after all) prompting reactions of disbelief, then we had post-Cold War research budget cuts, then slow and badly funded ITER program (with some countries pulling out, no less, hopefully these won't get any access to data once it's successful). We could have been much further now, just no political will

[K. A. Pital]

The first 20 years the West mostly ignored that the USSR had a functioning TOKAMAK - perhaps for political reasons, too. They couldn't really admit that the USSR got something so fundamental first, right and functioning with such an enormous lead.

[Sky Captain]

For stable power generation I think tokamak approach are more likely to work because of constant output. Laser ignition only provides burst of power and then chamber has to be cleared from reaction products, new fuel pellet inserted - just sounds more complex. If you want serious gigawatt range output depending on how often whole process can be reset it may be required to have each burst have explosion power comparable to large bomb, there may be obvious technical difficulties with that.

[Magis]

For stable power generation I think tokamak approach are more likely to work because of constant output. Laser ignition only provides burst of power and then chamber has to be cleared from reaction products, new fuel pellet inserted - just sounds more complex. If you want serious gigawatt range output depending on how often whole process can be reset it may be required to have each burst have explosion power comparable to large bomb, there may be obvious technical difficulties with that.

The NIF's vision for a fusion power demonstration facility would achieve 10 bursts/second. The fuel pellets would be fired at high speed straight through the reaction chamber and out the opposite side. In the middle of their flight, in the center of the chamber, they would be hit by the laser and fuse.

[Oskuro]

Oil companies will start buying renewable companies when we start running out or finally break our addiction to that black heroin.

Of course they will, what I really wonder is if those energy sources will be efficient enough to properly replace oil in our current (or future) energy needs.

[Borgholio]

Oil companies will start buying renewable companies when we start running out or finally break our addiction to that black heroin.

Of course they will, what I really wonder is if those energy sources will be efficient enough to properly replace oil in our current (or future) energy needs.

A combination of large scale solar, wind, geothermal, hydro, and tidal power could work to supply a large amount of our power needs. The rest would have to be made up with *gasp* nuclear power.

[Kanastrous]

"I am so sorry for continuing to be flippant about this technological achievement, but according to Dr. Hurricane's bio here, his work ...focuses on weapons physics, high energy density physics (HEDP) science, the theory of plasmas, and plasma instability. He has authored 44 journal publications and 54 conference papers, largely in the area of plasma physics and HEDP. He was the lead Secondary Designer for W87 warhead during most of its life extension program (LEP)".

Are we absolutely sure he isn't working out of a volcano lair? I'm suspecting volcano lair.

While we were scouting at the NIF our hosts were kind of sort of chuckling over how the project had been funded for the purpose of weapons-design validation, and the fusion-energy aspect of the work was sort of an extra. Chuckling, because their attitude appeared to be "we snookered 'em into financing fusion energy research by selling them on a weapons program."

So the involvement of guys with impressive weapons-development credits isn't surprising. Also - and this is just my guess - it seems natural that the people with the knowledge base to contribute to reactor programs would overlap with the people suited to reactor research.

[Starglider]

For stable power generation I think tokamak approach are more likely to work because of constant output.

Tokamaks do not have constant output. The design is inherently limited to pulsed operation, because the plasma current (that provides lateral confinement) is unstable. JET uses pulses in the 60 second range and ITER is supposed to be capable of pulses up to 1000 seconds, although 400 will be more typical. This is not terribly relevant for electrical power generation as it's easy to provide a thermal buffer with sufficient heat capacity to maintain steam generation. However the thermal and electrical cycling is hard on the physical plant. Pulsed output on laser inertial fusion can also be worked around, but the frequency is thousands of times higher so the engineering challenges are a bit different.

Stellerators do have constant output, because they don't rely on plasma current for confinement. Stellerators are in general just a more elegant and robust solution to the problem - see Wendelstien 7-X for the most impressive example - but are harder to design and build so have consistently trailed Tokamaks in development. My layman opinion is that magnetic confinement fusion (all flavours including Polywell) is still considerably more promising than inertial for power generation. LIF gets so much funding because it's more useful for nuclear weapons research, although the need for fusion power is so great it would be worth investigating anyway.