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Progress toward fusion energy gain as measured against the Lawson criteria

fusionenergybase.com

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Re: Progress toward fusion energy gain as measured against the Lawson criteria

#121

Post by DennisP »

bbatha wrote: post #110
boxed wrote: post #91

Earlier quoted context omitted.

From what I understood, laser fusion needs laser efficiencies not just 40x better than what NIF uses, but like 3 or 4 orders of magnitude more efficient than the state of the art. Seems like a non-starter.

Everything fusion reactor design needs similar gains in some part of the stack outside of the fusion parts to make it a viable power source: tokamaks need magnets to be orders of magnitude better, the lining for the reactors needs to last for much longer, the whole steam conversion mess, etc.

Commercial REBCO tape is an entirely sufficient superconductor for tokamaks. At this point the limiting factor for the magnetic field is the structural strength of the reactor. Tokamak output scales with the square of size and the fourth power of magnetic field strength, and using REBCO, the CFS ARC design should get practical power output from a reactor much smaller than ITER.

Re: Progress toward fusion energy gain as measured against the Lawson criteria

#122

Post by myrmidon »

cobbzilla wrote: post #113
myrmidon wrote: post #103

Earlier quoted context omitted.

> I call things like ITER "Blazing Saddles" projects. "We have to protect our phony baloney jobs, gentlemen!" I think this is overly harsh and somewhat unfair. You could make the same argument that anything operating in a regime similar to the Chicago Pile 1 could never be an economical reactor nor a bomb, but that does not mean skipping that particular development step is viable. As far as fusion reporting goes, art…

conceptually sure; but size-wise they are so different as to warrant valid questions about ROI. Chicago Pile 1 ran for 12 years, ITER started ~12 years ago and plans to run into the 2030s at least. Budget and headcount would likely be vastly different too, I’d welcome any educated guesses. Sometimes quantity has a quality of its own, as they say.

Sure but those are not really equivalent/comparable in scale; just looking at power/size and conceptual distance from commercial viability, the Chicago pile does not even match up to something like SPARC or JET, much less ITER.

A more fitting comparison to ITER would be something like Fermi-1 or other prototype designs at almost commercial scale, IMO, and those were multi-year, large projects too (and fission is much simpler than fusion, which obviously also helps).

Re: Progress toward fusion energy gain as measured against the Lawson criteria

#123

Post by UltraSane »

worik wrote: post #95
UltraSane wrote: post #81

Earlier quoted context omitted.

I am so tired of this lie being repeated endlessly. We have a perfectly safe way to handle nuclear "waste": reprocess the dirty fuel and bury the actual waste deep underground like Finland is doing at the Onkalo spent nuclear fuel repository. https://en.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_repo... And there is still very much a need for zero-carbon DISPATCHABLE electricity of witch nuclear is the ONLY choice.…

> bury the actual waste deep underground How deep, to stay put thousands of generations?

https://en.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_repo...

Re: Progress toward fusion energy gain as measured against the Lawson criteria

#124

Post by gene-h »

Calwestjobs wrote: post #111
gene-h wrote: post #41

This will probably need to be updated soon. There are rumors NIF recently achieved a gain of ~4.4 and ~10% fuel burn up. Being able to ignite more fuel is notable in and of itself.

what "gain" means.

Energy out/energy into capsule

Re: Progress toward fusion energy gain as measured against the Lawson criteria

#125

Post by adgjlsfhk1 »

Kubuxu wrote: post #93
adgjlsfhk1 wrote: post #86

Earlier quoted context omitted.

hydro is also a 0 carbon dispatchable choice (which is much cheaper)

Majority of good spots for hydro were already built up, and if they weren’t, good luck with NIMBY.

meant of the good spots are already used, but we can change how they are used to greatly increase their usefulness to a 0 carbon grid. we can make them all pumped hydro, and start treating hydro as a battery rather than a generation source.

Re: Progress toward fusion energy gain as measured against the Lawson criteria

#126

Post by damnitbuilds »

stshank wrote: post #63
damnitbuilds wrote: post #55

Hmm. How much of this progress is really progress to actual useful fusion power ? I want to believe, but this does not make that easier.

Progress toward net fusion energy is critical for delivering fusion power on the grid. It's not the only progress required — the rest of the machine has to be economical to build and operate. Most of the fusion machines in this paper are scientific projects, but as commercialization progresses, fusion machines with power plant needs in mind should arrive. (I work for one startup in the field, Commonwealth Fusion Syst…

I wish you luck !

Re: Progress toward fusion energy gain as measured against the Lawson criteria

#127

Post by sam »

Calwestjobs wrote: post #111
gene-h wrote: post #41

This will probably need to be updated soon. There are rumors NIF recently achieved a gain of ~4.4 and ~10% fuel burn up. Being able to ignite more fuel is notable in and of itself.

what "gain" means.

In the context implied above it is the ratio of fusion energy released to laser energy on target or the laser energy crossing the vacuum vessel boundary (they are the same in this case). So it would have been more precise to say "target gain" or "scientific gain".

Re: Progress toward fusion energy gain as measured against the Lawson criteria

#128

Post by cyberax »

pfdietz wrote: post #112
cyberax wrote: post #73

Earlier quoted context omitted.

DEMO concept sketches are completely obsolete at this point. It's not going to look anything like this. They're based on the state-of-the art from about 2005. Since then, a lot of improvements happened. A more realistic power plant design is going to use a thinner center column (because of better superconducting magnets), resulting in a smaller cryostat volume. Possibly high-TC magnets. It can also be made more compa…

It's my understanding that neutron wall loading of DEMO concepts had been trending downward (due to materials limits), the opposite of the trend you're trying to portray there. And in no future world is the power density of DEMO going to be anywhere close to that of a fission reactor.

Neutron loading is not the limiting factor (for now), it's the magnetic field pressure and its homogeneity. That's actually what is driving the humongous size of the ITER.

To solve the homogeneity problem, you need the central column to be as thin as possible. That's where a lot of the recent advancements can help.

Also, fission research and fusion are actually aligned in designing materials that can tolerate more displacements per atom.

> And in no future world is the power density of DEMO going to be anywhere close to that of a fission reactor.

That's for sure. Modern fission reactors are close to magic, with the amount of heat they produce for a given volume.

Re: Progress toward fusion energy gain as measured against the Lawson criteria

#129

Post by hinkley »

trhway wrote: post #54
hinkley wrote: post #35

Earlier quoted context omitted.

I was trying to work out a joke about buying better lasers off of alibaba but it seems that despite being 30 years old they're still orders of magnitude beyond off the shelf options.

partially. The very efficient lasers from alibaba don't have short pulse/high power, so they can potentially be used only as the part of the system - the pumping lasers. The final nanosecond-laser is still a one-off build which though seems to be pretty doable even by a small company if they set their mind to it. Btw, NIF achieved those recent results by adding strong magnetic field around the target (penny-shrinkers…

I’ve seen some pretty wacky structures that involve mechanically forcing permanent magnets together at different orientations to create assymetric magnetic fields that are strongest where they need to be or weak where they would cause problems. Like eddy currents in electric motor housing, or insufficient hold for chef’s knives.

I know motor windings have gotten pretty funky of late to do a little bit of this, but do they do multi tesla magnetic fields that use several different windings to create the same sorts of bias in field strength? The ITER windings seem to be an extremely mild form of this.

Re: Progress toward fusion energy gain as measured against the Lawson criteria

#130

Post by pfdietz »

cyberax wrote: post #128
pfdietz wrote: post #112

Earlier quoted context omitted.

It's my understanding that neutron wall loading of DEMO concepts had been trending downward (due to materials limits), the opposite of the trend you're trying to portray there. And in no future world is the power density of DEMO going to be anywhere close to that of a fission reactor.

Neutron loading is not the limiting factor (for now), it's the magnetic field pressure and its homogeneity. That's actually what is driving the humongous size of the ITER. To solve the homogeneity problem, you need the central column to be as thin as possible. That's where a lot of the recent advancements can help. Also, fission research and fusion are actually aligned in designing materials that can tolerate more di…

However, if neutron loading has gone down, and the reactor is the same size, the volumetric power density must also have gone down.

The comment about fission and neutron dpa is misleading. The neutron damage issue is much less bothersome in fission reactors.

Fission produces about 3% of its energy in neutrons, vs. 80% in the DT fusion reaction. The spectrum of fission neutrons is much softer, with a peak around 1 Mev, vs. 14 MeV for DT neutrons. The DT neutrons are above threshold for (n,2n) reactions in most materials, and have much higher cross section for (n,p) and (n,alpha) reactions. The latter is particularly troublesome, as helium accumulates inside materials, forming microscopic very high pressure bubbles that rip the materials apart.

But it's even comparatively worse for fusion than that. In a PWR (for example), the core is carefully designed so that the only parts exposed to unmoderated neutrons are the fuel rods and the replaceable parts of the fuel rod bundles. The latter provide structural support for the fuel rods and are removed along with the fuel rods when the fuel is spent. The actual core supports for the fuel bundles are well away from where the chain reaction is occurring, shielded by water. The mean free path of a fission neutron in water is just a few centimeters, so their energy is quickly dissipated before reaching these components.

So, exposure of permanent reactor components to fast neutrons is essentially a non-issue in PWRs. Even control rods are not exposed much; reactivity is controlled by boric acid dissolved in the water (BWRs do it somewhat differently.)

This same strategy cannot be used in a fusion reactor; the plasma facing surfaces are exposed to the full, unshielded brunt of the DT neutron flux. Maybe a few cm of liquid lithium could be flowed along some surfaces? This is a stretch, particularly in a toroidal reactor.

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