MIT-designed project achieves major advance toward fusion energy • Hacker News Board

Re: MIT-designed project achieves major advance toward fusion energy

#411

Post by lambdatronics » Fri, Sep 10, 2021, 3:49 AM UTC

tsimionescu wrote: post #265

dfdx wrote: post #34

Plenty of skepticism in these comments. I've been following CFS for a while and can present a point of view for why this time might be different. Fusion energy was actually making rapid progress in the latter half of the twentieth century, going from almost no power output in the fifties and sixties to a power output equal to 67% of input power with the JET reactor in 1997. By the eighties there was plenty of experim…

There are still fundamental problems with fusion reactors that are unlikely to make them economically viable, or even carbon neutral. Most notably, the extreme temperatures, hydrogen pumping, and high-energy neutron bombardment mean that, even with liquid metal blankets, the reactors will very quickly become brittle, probably not lasting more than a year or two. Since neutron bombardment also turns any material radio…

The nuclear engineering side of fusion has been underfunded for a long time. It's only been in the last couple years that the plasma physics side of the house has been willing to say "OK, we're close enough now that it's time to rebalance the budgets -- even if that means some of us lose our jobs."

Re: MIT-designed project achieves major advance toward fusion energy

#412

Post by lambdatronics » Fri, Sep 10, 2021, 3:56 AM UTC

causality0 wrote: post #61

dfdx wrote: post #34

Plenty of skepticism in these comments. I've been following CFS for a while and can present a point of view for why this time might be different. Fusion energy was actually making rapid progress in the latter half of the twentieth century, going from almost no power output in the fifties and sixties to a power output equal to 67% of input power with the JET reactor in 1997. By the eighties there was plenty of experim…

Are those calculations of net gain referring to the total energy generated, or the amount we can realistically capture and put to use?

You can assume that they're talking about the total generated. They call this the "scientific gain" whereas the "engineering gain" would include all the inefficiencies of the particle beam injectors that put power into the tokamak, and the inefficiency of the steam turbine that makes electrical power from the fusion heat exhaust, and the auxilliary power to run all the pumps, etc. It's generally thought that the "engineering gain" needs to be at least 5, and the "scientific gain" at least 30, for a working reactor. ITER's supposed to hit scientific gain of something like 10-20, which is close.

Re: MIT-designed project achieves major advance toward fusion energy

#413

Post by baq » Fri, Sep 10, 2021, 4:38 AM UTC

xyzzyz wrote: post #274

kongin wrote: post #236

Earlier quoted context omitted.

So that's between 150 and 250 years with the 2.5% energy consumption grows, then that much again for us to produce more energy than the sun shines on Earth. https://en.wikipedia.org/wiki/World_energy_supply_and_consum...

Yes, and with 2.5% energy consumption growth, in only 2500 years, we'll consume entire power output Milky Way galaxy. Extrapolating exponential growth over long timescales leads to silly results.

nothing silly about it if the purpose is to make a point in a discussion with an economist. some of them just don't get it that energy consumption is correlated with economic growth and you can't just grow yourself out of every problem.

Re: MIT-designed project achieves major advance toward fusion energy

#414

Post by baq » Fri, Sep 10, 2021, 4:41 AM UTC

el_nahual wrote: post #387

ziotom78 wrote: post #321

Earlier quoted context omitted.

Well, there is some radioactive waste [1], but its decay time is far smaller and is thus far easier to handle. (Moreover, there is a larger choice of elements.) [1] https://en.wikipedia.org/wiki/Fusion_power#Radioactive_waste

Aren't fast decay times harder to handle?

it's easier in the sense that a single accident doesn't make the area uninhabitable in the human civilization timescales. fast decay = it'll kill you today in a minute, but will be safe to approach in a week, or 50 years.

Re: MIT-designed project achieves major advance toward fusion energy

#415

Post by tcmart14 » Fri, Sep 10, 2021, 5:05 AM UTC

aaronblohowiak wrote: post #246

tcmart14 wrote: post #216

Earlier quoted context omitted.

I'd say yes and no. You most definitely have a point here as I agree that their model, or view, is different than NASA. However, if NASA had not happened, would even conceiving of a different model or target had happened? Not to mention just initial research into rocketry. It maybe could have happened without NASA, but probably with a severely higher initial investment.

The soviets had a very strong space program and arguably their rocket designs have had a significant impact on spacex…

I should have included them also. It is very much a "standing on giants." As many scientists and engineers from different countries and nationalities have made major contributions. I believe it was an early soviet scientist in the 20s who came up with the formula for how much fuel needed to be loaded into a rocket.

Re: MIT-designed project achieves major advance toward fusion energy

#416

Post by nickik » Fri, Sep 10, 2021, 5:30 AM UTC

pfdietz wrote: post #347

nickik wrote: post #323

Earlier quoted context omitted.

While this is true, its a fact that the regulatory and governmental outlook on fission has prevented these changes from happening. The western world has made development of new fission plants practically impossible. Requiring 100s of millions in development before you might get a hint if the government would actually allow you to build a plant. Thankfully this has finally started to change. Mostly in Canada and that'…

Regulation is the scapegoat for nuclear's failure, but it's equally the case that regulation is vital to nuclear (and to nuclear getting liability caps.) If the risk of nuclear were not socialized no one would build it (or insure it). What has also prevented changes from happening is that nuclear scales down poorly, so the cost of iterating designs is so large. Making a new kind of PV cell or module, or wind turbine,…

> Regulation is the scapegoat for nuclear's failure

No it isn't. If you have a regulatory structure that makes progress so expensive and counter to the government plan then progress is very hard to make.

Even the regulatory agency themselves have realized this and are changing their structures.

> What has also prevented changes from happening is that nuclear scales down poorly, so the cost of iterating designs is so large.

US regulation allows nothing between fully commercial and university research making any time of prototyping impossible.

Its in fact very possible to make smaller reactors that can teach you a lot and are not absurdly expensive and still useful. That data then could be used for to further inform regulatory agencies.

> The replicated nature of these sources is an advantage in so many ways.

Yes but even if it doesn't scale down well in terms of engineering you can still do factory construction of reactors. If we can mass produce plans, rocket engines, rockets and cars then the same could be done with reactors.

The reality is the government selected one winner and made deploying anything else practically impossible. The change in regulatory agencies has basically made progress impossible beyond marginal improvements.

Re: MIT-designed project achieves major advance toward fusion energy

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Post by nickik » Fri, Sep 10, 2021, 5:34 AM UTC

Symmetry wrote: post #362

nickik wrote: post #317

Earlier quoted context omitted.

Very questionable if a fusion reactor is safer then a common molten salt fission reactor. I would argue that is far less likely to 'explode'. And you can burn up the waste majority of that waste, the leftover waste after that would not really a huge issue. Both of these are far more political problems then actual real problems a society based on modern fission would have.

The problem with fission reactors in general is that after you stop the chain reaction you've still got a tenth or so of the power output you had when it was on from decay heat for a while and you need a reliable way to get rid of that heat even in the event of a disaster. With fusion the nice thing is that the new heat stops appearing as soon as the reaction stops.

Yes and that is far easier to do then containing a fusion reaction.

There are known well understood engineering solution that have been known since the 70s and that work fine.

The real danger is the high pressure that PWR are under and the chemical instability of the elements that were put together in those designs.

Reactors that are not under pressure and do not have chemical instability that lead to explosive cases have a very contained area of effect even in a worst case.

Re: MIT-designed project achieves major advance toward fusion energy

#418

Post by pfdietz » Fri, Sep 10, 2021, 12:34 PM UTC

tsimionescu wrote: post #280

AnthonyMouse wrote: post #262

Earlier quoted context omitted.

> Coal is dead. The competition is PV, and to a lesser extent wind. Coal is dying but it's still ~20% of US generation. The natural gas share of US generation has gone up . > Yes, and you use odd bits of land close to consumption sites, many of which will have simultaneous use for other purposes. Until you run out of those and then your costs increase worse than linearly because you have to start using more expensive…

> This is the opposite of how economies of scale work. If you make something bigger, the variable costs scale linearly and the fixed costs stay the same but are amortized over more units. That's not how construction works. Past some small scale, construction cost scales quadratically or worse with size. Building a 100m tall sky scraper is not 10 times as expensive as building a 10m tall 3-story house - it is at least…

I will note that fusion reactors have serious diseconomies of scale.

First, the power output of a fusion reactor is limited by what the first wall can withstand. Therefore, the power goes as radius^2, where as the cost goes (at least) as radius^3.

Second, the larger a fusion reactor becomes, the more parts it has, and the more reliable each individual part has to be (since there will be no redundancy in many; an leak into the vacuum chamber shuts down the reactor, for example). Reliability is expensive, so each part becomes more expensive as it is required to be more reliable.

Renewables sources are extremely redundant, so they'd scale just fine even with unexceptional per-unit reliability.

Re: MIT-designed project achieves major advance toward fusion energy

#419

Post by jonnycomputer » Fri, Sep 10, 2021, 12:52 PM UTC

danans wrote: post #399

jonnycomputer wrote: post #397

Earlier quoted context omitted.

which it should be. carbon is not the only environmental issue we face. appalachia is the main channel of animal migration. its incredible. we should do all we can to protect it's integrity.

> which it should be. Solar power will never need to remove more than a tiny fraction of tree cover from Appalachia. What's a far bigger threat to the ecosystem, including animal migration, is mountaintop removal for coal mining: https://law.lclark.edu/live/blogs/134-de-regulation-of-mount...

Whatever. You can stop mountain removal mining for coal, and prevent environmentally sensitive land from being devastated for solar farms. Its not an either/or, since there is, in fact, plenty of other land that can be used for solar farms.

Re: MIT-designed project achieves major advance toward fusion energy

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Post by ncmncm » Fri, Sep 10, 2021, 3:09 PM UTC

AnimalMuppet wrote: post #66

ChrisMarshallNY wrote: post #6

Earlier quoted context omitted.

The running joke has always been that “Fusion is 20 years away,” and has been, for the last 50 years. I really want this to work. I am a bit concerned, with how “the old guard” will react, once we have successful, productive, fusion. I foresee an astroturf NIMBY campaign against construction of fusion plants.

Per a comment by nielsbot, they're saying 2025. So, four years away, not 20. That's progress...

That is production of hot neutrons, not electrical power. Actual electrical power is still decades away... or would be if anybody bothered to try building it. Cost-effective electrical power from Tokamak is never.

FRC, though, maybe. But you would have to have people actually working on that.