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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

#71

Post by elihu »

moffkalast wrote: post #53
albertopv wrote: post #22

Real Engineering published a video about Helion Energy company. I don't have the tools to filter out commercial BS, still it seems to me to be most promising effort. The idea to get electricity directly from magnetic fields instead of boiling water is very intriguing.

I've also been quite surprised watching that one, it's completely novel approach to fusion and it may be the best way to mass adoption. If they can make it work that is. What most surprised me about NIF's ignition announcement was that this was even news. I'd assumed for years that most if not all tokamaks and stellerators could already achieve at least some brief fusion, just not to a useful degree. Turns out they'r…

> What most surprised me about NIF's ignition announcement was that this was even news. I'd assumed for years that most if not all tokamaks and stellerators could already achieve at least some brief fusion, just not to a useful degree.

I think they've done fusion in tokomaks and stellerators before, it's just that the energy applied to the plasma is greater than the additional energy that's created by fusion. It's not that no fusion is happening at all in the most powerful magnetic confinement devices yet built, it's that there isn't very much of it happening.

That's my layperson's understanding anyways.

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

#72

Post by albertopv »

hoseja wrote: post #60
moffkalast wrote: post #53

Earlier quoted context omitted.

I've also been quite surprised watching that one, it's completely novel approach to fusion and it may be the best way to mass adoption. If they can make it work that is. What most surprised me about NIF's ignition announcement was that this was even news. I'd assumed for years that most if not all tokamaks and stellerators could already achieve at least some brief fusion, just not to a useful degree. Turns out they'r…

They basically have no real achievements yet - the energy harvesting system isn't working, they are just fusing D+He3 - even though the concept sounds impressive. The video was cool but not cool enough to break through healthy fusion vaporware skepticism.

There is no energy harvesting system yet, next prototype will be include that. I like their "fast" (relatively speaking, of course) prototyping process.

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

#73

Post by moffkalast »

elihu wrote: post #71
moffkalast wrote: post #53

Earlier quoted context omitted.

I've also been quite surprised watching that one, it's completely novel approach to fusion and it may be the best way to mass adoption. If they can make it work that is. What most surprised me about NIF's ignition announcement was that this was even news. I'd assumed for years that most if not all tokamaks and stellerators could already achieve at least some brief fusion, just not to a useful degree. Turns out they'r…

> What most surprised me about NIF's ignition announcement was that this was even news. I'd assumed for years that most if not all tokamaks and stellerators could already achieve at least some brief fusion, just not to a useful degree. I think they've done fusion in tokomaks and stellerators before, it's just that the energy applied to the plasma is greater than the additional energy that's created by fusion. It's no…

I'm not sure if it's true or not exactly, but I don't see how the NIF experiment would be any different from that if that were true, and in that case it wouldn't be news at all. It's not like they didn't use absurd amounts of laser power to get a tiny poof.

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

#74

Post by albertopv »

Cthulhu_ wrote: post #69
albertopv wrote: post #57

Earlier quoted context omitted.

I'm very skeptical about those great announcements, even more when there's an announcement of the announcement. 300MJ in, 3MJ out, I wouldn't call it a breakthrough, maybe a milestone, nothing more.

And yet, they need to keep making announcements, else their funding will be cut. They knew all along that fusion energy would take decades to develop, and every year they need billions in funding to keep pushing for advancements. They can't just go radio silent until they're like "we've done it", they need to regularly publish papers and make big media announcements etc. Come to think of it, the LHC has been silent f…

I understand, but twice the expectation, double the disappointment, at least for me and in this specific case.

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

#75

Post by denton-scratch »

arethuza wrote: post #18
fallingknife wrote: post #14

Earlier quoted context omitted.

Actually, the tech that you are hinting at would guarantee clean fusion power. If you could generate clean fusion explosions, detonate underground and use the heat to generate power. Nuclear bombs are currently the only net energy positive fusion devices we have.

Most bomb designs are fission-fusion-fission - most of the energy comes from the fission of the casing of the secondary by neutrons from the fusion process in the secondary. Edit: Mind you - there were tests like the huge Tsar Bomba that de-rated at 100+ Mt design to 50Mt be leaving out the final fission stage - the output being mostly from fusion. https://en.wikipedia.org/wiki/Tsar_Bomba

My understanding is that what you're referring to as a "fusion" stage is really a fusion-enhanced fission stage. All the stages of normal "H-bombs" are fission stages, using a small fusion core to generate a flood of neutrons, which results in the fission fuel combusting more completely.

Pure fission bombs tend to disintegrate long before enough neutrons have been generated to achieve complete combustion. The inclusion of a small core of lithium deuteride results in a much more efficient fission bomb.

I suppose these NIF tests are tiny pure fusion explosions; but I'm not aware of any practical weapon that generated energy mainly from fusion.

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

#76

Post by TheOtherHobbes »

danbruc wrote: post #59
tmikaeld wrote: post #12

Earlier quoted context omitted.

For one, it's theoretically impossible to make lasers 102 times more efficient, especially if you consider the current industrial efficiency of up to 20% (30% under special conditions). For example, the maximum efficiency of a laser is limited by the quantum efficiency of the laser material, which is the ratio of the number of photons emitted by the laser to the number of charge carriers (electrons and holes) injecte…

For one, it's theoretically impossible to make lasers 102 times more efficient, especially if you consider the current industrial efficiency of up to 20% (30% under special conditions). That is not true. You can of course not make a 10 % efficient laser more than 10 times more efficient, but there is no limit to how much more efficient you can make a laser in general, you just have to start with an inefficient enough…

I'm not sure if it's theoretically impossible. But it's certainly an incredible challenge to build a high efficiency laser system that can consistently generate many pulses per second without degrading either the laser head itself or any associated micro-focussing optics.

Can we stop pretending this isn't about nuclear weapons research and - basically - continued funding?

LLNL is at least a decade behind its initial predictions of ignition. The current lasers may be inefficient but they've been fine-tuned very precisely for optical quality. There's no guarantee more efficient lasers would have the same characteristics and could be focussed in the same way.

I'm sure LLNL know the maximum theoretical fusion gain for a realistic pellet design, and it's worth nothing that that number hasn't been mentioned anywhere. Clearly there's only so much energy available for each cycle. If that energy is on the wrong side of what's needed to release it even after efficiency improvements, the entire system isn't workable, no matter how it's re-engineered.

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

#77

Post by skelpmargyar »

nayroclade wrote: post #46
skelpmargyar wrote: post #17

Earlier quoted context omitted.

It's better to focus on standardised production lines for small fission reactors currently if your goal is to produce energy for the power grid right now, but that's not what cutting-edge research or science is about. Whoever launched the first firework probably didn't see how people could walk on the moon either. Science is rarely a linear path. It's also rarely "I have this problem so I solved it this way." That's…

Except it isn't the HN readership who choose to constantly frame these stories in terms of engineering. From the article: "These and other scientific, technological and engineering hurdles will need to be overcome before fusion will produce electricity for your home. Work will also need to be done to bring the cost of a fusion power plant well down from the US$3.5 billion of the National Ignition Facility. These step…

What that that paragraph means is that things that do not exist will cost money to bring into existence. A significant amount. It's not a critique. This is not new. This is not a fusion problem. There is an initial cost and development to any new technology. This technology is particularly difficult, however. It's also sustainable real renewable energy. You have to worry about actually being able to invent something before you can worry about saving money on that thing. Look up how much the Manhattan Project cost! This shit is not software engineering; It's really really fucking complicated it will cost a load of money.

We don't really know what path fusion research will lead to. It's science. We don't know what we could find out tomorrow that could apply this research. But even the promises of commercial power generation alone should be enough to keep funding the project whether it will happen in 50 years or 100 years. It's not like they aren't making progress. You can't rush research and also under fund them.

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

#78

Post by IanCal »

moffkalast wrote: post #73
elihu wrote: post #71

Earlier quoted context omitted.

> What most surprised me about NIF's ignition announcement was that this was even news. I'd assumed for years that most if not all tokamaks and stellerators could already achieve at least some brief fusion, just not to a useful degree. I think they've done fusion in tokomaks and stellerators before, it's just that the energy applied to the plasma is greater than the additional energy that's created by fusion. It's no…

I'm not sure if it's true or not exactly, but I don't see how the NIF experiment would be any different from that if that were true, and in that case it wouldn't be news at all. It's not like they didn't use absurd amounts of laser power to get a tiny poof.

But there was more energy released than laser power going in. That's what the news was about

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

#79

Post by wumms »

> more than 5 million degrees Fahrenheit (3 million Celsius) – about 100 times hotter than the surface of the Sun

As my fear of Crichton's Gell-Mann Amnesia sets in, I'm being pedantic: either its about 545 times hotter than the surface of the sun (5.500°C) or they've reached "only" 0.55 million degrees Celsius.

Also: its only 519 times hotter than the surface of the sun when using absolute temperature (5.778 K).

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

#80

Post by denton-scratch »

rgmerk wrote: post #31
fallingknife wrote: post #14

Earlier quoted context omitted.

Actually, the tech that you are hinting at would guarantee clean fusion power. If you could generate clean fusion explosions, detonate underground and use the heat to generate power. Nuclear bombs are currently the only net energy positive fusion devices we have.

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, the reactor itself is a pile of toxic waste that will need long-term storage.

I don't believe that fusion is inherently dirty; just that none of the technologies currently being investigated can be described as "clean". And they all run the risk of nuclear proliferation.

IANAP.

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