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Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

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Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#161

Post by DennisP »

denton-scratch wrote: post #80
rgmerk wrote: post #31

Earlier quoted context omitted.

It might guarantee clean fusion power, but there's no guarantee it would be in any way economic. Edward Teller proposed something along these lines with conventional two-stage nuclear explosives back in the 1970s, but it was rapidly abandoned as horribly inefficient and costly: https://en.wikipedia.org/wiki/Project_PACER I know this stuff is fun to speculate about but the boring and unsexy option of more solar panels…

> clean fusion power From what I understand, practical routes to fusion all produce a lot of fast neutrons, and tritium. The neutrons make the surrounding equipment radioactive, and create toxic elements. The tritium is itself toxic, and is hard to contain. And the high neutron flux means that such a machine could easily be used to create weapons-grade plutonium, by irradiating uranium. And come decommissioning time,…

These issues apply to D-T fuel, whose output energy is 80% high-energy neutrons. Helion is using D-D/D-He3, whose output would be only 6% neutrons, at lower energy. If you do the D-D reactions in specialized fuel production facilities, you could sell the He3 to anyone with an He3 power plant and they'll have zero neutron radiation to deal with or misuse.

Even with D-T, the reactor waste would stop being dangerously radioactive in a few decades.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#162

Post by throwawaymaths »

dotnet00 wrote: post #120
bawolff wrote: post #39

Everything i have heard about this makes it sound more like a milestone than a breakthrough. I.e. its great it happened and an important step, but its not shocking that we eventually did it. When i hear breakthrough i think of something more unexpected. I.e. figuring out how to solve a problem we had no idea how to solve.

I feel like HN is being especially pedantic and jaded about this specifically and I don't really get why. Scientifically this is absolutely a breakthrough, just like the detection of the Higgs boson was despite them already having expected it or just like LIGO's detections of gravitational waves were despite that being entirely what it was built for or just as JWST's detections of galaxies much older than those seen…

No it's not a breakthrough. It is only net positive because the NIF has an exquisitely stupid and convenient place where they are defining "energy in" which let's them cheat how good it looks. If you could take other types of fusion and draw a clever line around where you start tallying energy in, then they would have had "breakthroughs" long ago.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#163

Post by jliptzin »

HPsquared wrote: post #97
sigmoid10 wrote: post #86

Earlier quoted context omitted.

You greatly underestimate the order of magnitude difference of produced energy in these two examples. You can't contain a bomb's hydrogen fusion reaction in a chamber for the simple reason that you need a nuclear fission warhead just to ignite it. So if you want to produce useful, controlled energy outside of killing things, the lasers are your only shot for inertial confinement fusion. Yes they still get damaged, bu…

Parent was basically saying it has not been a physics problem for decades, it's already an engineering problem and there is no change there. The physics are known to work and have been demonstrated decades ago in a different engineering context (i.e. weapons).

Didn’t we already know it’s just an engineering problem by virtue of the sun existing?

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#164

Post by px43 »

dotnet00 wrote: post #120
bawolff wrote: post #39

Everything i have heard about this makes it sound more like a milestone than a breakthrough. I.e. its great it happened and an important step, but its not shocking that we eventually did it. When i hear breakthrough i think of something more unexpected. I.e. figuring out how to solve a problem we had no idea how to solve.

I feel like HN is being especially pedantic and jaded about this specifically and I don't really get why. Scientifically this is absolutely a breakthrough, just like the detection of the Higgs boson was despite them already having expected it or just like LIGO's detections of gravitational waves were despite that being entirely what it was built for or just as JWST's detections of galaxies much older than those seen…

With the Higgs, we got the mass, which was not predicted by any of the theoretical models. We were basically done at that point. With LIGO we got tons of tangible data of black holes colliding.

Fusion is not useful until Q>1, and for NIF to claim that when it obviously isn't true is, IMO, a bad look. They invented Qplasma where they arbitrarily get to ignore over 99% of the energy that actually went in, and don't need to worry about capturing any of the energy actually coming out. They got Qplasma>1, which is a great milestone, but the overwhelming narrative in the media is that they got more energy out than they put in, which is simply not true.

Someone, and almost certainly someone *ELSE* will get to Q>1 very soon. Lots of groups are targeting 2024-2025. That will be a major breakthrough, but in the public mind, NIF already did it, and I guarantee that's going to cause a lot of confusion.

It just feels like a marathon race where a bunch of competitors are competing honestly, and one participant jumps in a scooter, and blasts through the finish line, and the crowd is cheering, and they're doing interviews about how great it was to win the race, and people are going home, but the actual race is still happening, and getting super interesting, but no one cares anymore because that milestone was already claimed by someone who didn't even accomplish it.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#165

Post by generalizations »

chongli wrote: post #32
garyclarke27 wrote: post #9

Most interesting fact from the article. At the system level it took 300 million Joules to produce 3 Million a 1% return - so still a very long way to go! With this kind of approach I can’t see how fusion can ever be cheap, the capital costs are enormous. Better to focus on standardised production lines for small fission reactors.

That's not the only big challenge. The fuel pellets are 1mm diameter hollow spheres machined out of diamond to extreme precision and filled with a tiny amount of deuterium-tritium gas inside. The pellets need to be carefully cooled to cryogenic temperatures so that the gas condenses evenly around the inside of the pellet, in order to maintain the near-perfect geometry needed for ignition. Once the pellet is hit with…

One of the things about reaching this point is that we can reconsider just how much of that complex process is required - like getting the poc of some code working, then working backwards to strip away what isn't necessary.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#166

Post by thereddaikon »

dotnet00 wrote: post #120
bawolff wrote: post #39

Everything i have heard about this makes it sound more like a milestone than a breakthrough. I.e. its great it happened and an important step, but its not shocking that we eventually did it. When i hear breakthrough i think of something more unexpected. I.e. figuring out how to solve a problem we had no idea how to solve.

I feel like HN is being especially pedantic and jaded about this specifically and I don't really get why. Scientifically this is absolutely a breakthrough, just like the detection of the Higgs boson was despite them already having expected it or just like LIGO's detections of gravitational waves were despite that being entirely what it was built for or just as JWST's detections of galaxies much older than those seen…

Because we've been told for decades that commercial fusion plants are a decade away. So people are understandably cynical about it. Really, physics has had a problem of late over hyping things that don't impact people's lives. Maybe that's unfair to expect every discover will directly lead to noticeable changes in technology. But I would argue that researchers over estimate how much people care about their discoveries. Laymen don't understand or care about minor milestones if they don't directly impact them. Or to put it another way, people will be receptive if you have a big achievement at your job but will get annoyed if you tell them every detail about it.

So yeah, when people are told fusion is around the corner but all they hear are small improvements that to them mean nothing, its easy to see why. Now obviously not everyone is that way, there are communities of laymen and amateurs online who are interested and do care. But you don't need public press conferences to get to them. A press conference is for Joe Sixpack. And Joe Sixpack assumes when you come calling about Fusion its to say that it works, global warming has been solved and his electric bill will be next to nothing.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#167

Post by thereddaikon »

px43 wrote: post #164
dotnet00 wrote: post #120

Earlier quoted context omitted.

I feel like HN is being especially pedantic and jaded about this specifically and I don't really get why. Scientifically this is absolutely a breakthrough, just like the detection of the Higgs boson was despite them already having expected it or just like LIGO's detections of gravitational waves were despite that being entirely what it was built for or just as JWST's detections of galaxies much older than those seen…

With the Higgs, we got the mass, which was not predicted by any of the theoretical models. We were basically done at that point. With LIGO we got tons of tangible data of black holes colliding. Fusion is not useful until Q>1, and for NIF to claim that when it obviously isn't true is, IMO, a bad look. They invented Qplasma where they arbitrarily get to ignore over 99% of the energy that actually went in, and don't nee…

I'd argue Q>1 isn't worth a press conference either. People care about commercial power generation and that needs more like Q>150.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#168

Post by TheDudeMan »

AlanSE wrote: post #145
randallsquared wrote: post #103

Earlier quoted context omitted.

> You can't contain a bomb's hydrogen fusion reaction in a chamber You certainly can, if you use a large enough chamber. Pacer was exactly this. You just have to accept high proliferation risk.

Pacer took thinking about nuclear fuels in a lot of new and interesting directions. For the use case of interest, they really wanted to maximize the fusion yield fraction, minimize the radioactive products, and minimize the total yield. Had it ever been allowed to proceed to a commercial scale, these would have been very tight, very challenging, technical constraints. If you relax one of those requirements, then it b…

We can also trigger fusion bombs with nice clean anti-matter instead of dirty fission. But we'd have to get better at making anti-matter.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#169

Post by zug_zug »

gaoshan wrote: post #144
dotnet00 wrote: post #120

Earlier quoted context omitted.

I feel like HN is being especially pedantic and jaded about this specifically and I don't really get why. Scientifically this is absolutely a breakthrough, just like the detection of the Higgs boson was despite them already having expected it or just like LIGO's detections of gravitational waves were despite that being entirely what it was built for or just as JWST's detections of galaxies much older than those seen…

Responding in a pedantic/jaded manner is one way to assert a form of intellectual dominance. For this audience I feel like that sort of dominance is unsurprising.

Agreed, but I think it has the side-effect of signaling "This technology advancement isn't worth excitement/praise/prestige" which I think in this case could have effects like demotivating people who might be considering going into the field.

Re: Nuclear physicist explains why fusion ignition is hailed as a major breakthrough

#170

Post by whywhywhydude »

rob74 wrote: post #43

Still unconvinced why this is such a major breakthrough - it may be the first net-positive controlled fusion, but the distinction between controlled and uncontrolled fusion is a bit academic in this case. In uncontrolled fusion ( https://en.wikipedia.org/wiki/Thermonuclear_weapon ), you are using a nuclear fission primary stage to generate enough energy to start the fusion reaction in the secondary stage. In the NIF,…

“So the only real difference between the first and the second case is that the H-bomb is smaller, much more expensive per amount of energy released, and explodes inside a chamber” - that sounds like a major technological breakthrough to me. They managed to concentrate so much energy inside a chamber in a controlled manner.
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