Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Successful second round of fusion experiments with Wendelstein 7-X

ipp.mpg.de

Post reply on HN
Print view View original

51–60 of 223 posts

Re: Successful second round of fusion experiments with Wendelstein 7-X

#51

Post by Jach »

hyperbovine wrote: post #11
ttul wrote: post #3

Experiments like Wendelstein remind me that the only thing holding back fusion power is money for research like this. Every year, we spend billions on fossil fuel exploration because the return on investment is quick - just think about all the wells going in to extract shale oil. What if we collectively had the will to invest this much into fusion?

Err no, money is not "the only thing" keeping us from having fusion power. I can think of one other thing which is that it's damn hard to create stellar-core conditions inside of a small containment vessel on Earth. It's not obvious that throwing more money at the problem is going to change this. After all, fusion research has been funded in some form or another since the 1950s. I'll bet if you added up all the resea…

In 1976 a plan for how much funding over how much time was made to get fusion ready. This graph shows the possible paths, as well as the actual level of funding, and is a great explanation for why fusion seems to always be x decades away: https://commons.wikimedia.org/wiki/File:U.S._historical_fusi...

Re: Successful second round of fusion experiments with Wendelstein 7-X

#52

Post by nine_k »

ben_w wrote: post #50
nine_k wrote: post #13

Earlier quoted context omitted.

I can imagine that this is just the neutron flux picture. The neutron streams should pass the walls pretty well (unfortunately), so registering it should not be hard.

I doubt that. High energy neutrons are difficult to diffract (so no lenses), reflect more like light on fog than light on tin foil (so no mirrors) and pass through material too easily for a pinhole lens to be plausible. I think you have to go to quite low energies (per neutron, not flux) for neutron optics to be a thing. Neutron cameras use collimated neutron sources to get around this, but that option isn’t availabl…

You don't need to diffract the neutron flux. Instead, you can wrap (low-res) neutron-sensitive material around the stellarator tube. IDK now well would conventional photodiode or CCD work under high magnetic field, though.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#53

Post by jessriedel »

nine_k wrote: post #52
ben_w wrote: post #50

Earlier quoted context omitted.

I doubt that. High energy neutrons are difficult to diffract (so no lenses), reflect more like light on fog than light on tin foil (so no mirrors) and pass through material too easily for a pinhole lens to be plausible. I think you have to go to quite low energies (per neutron, not flux) for neutron optics to be a thing. Neutron cameras use collimated neutron sources to get around this, but that option isn’t availabl…

You don't need to diffract the neutron flux. Instead, you can wrap (low-res) neutron-sensitive material around the stellarator tube. IDK now well would conventional photodiode or CCD work under high magnetic field, though.

That would just record the total neutron flux. It won't form an image unless you have a lens, aperture, or something similar.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#54

Post by gmueckl »

pastullo wrote: post #31
nine_k wrote: post #12

With fusion devices having trouble to confine the plasma for long times, I wonder if a massively-parallel fusion plant woud be feasible. Let's assume that plasma destabilisation does not damage the device, and is a mundane event. Build 10 or even 20 fusion devices (economy of scale!) feeding the common heat buffer, e.g. a large reservoir of a molten salt or metal. Feed conventional turbines off the heat of the heat t…

The idea of having many small fusion reactors is quite interesting. I never thought about it and i would normally dismiss it since building a big one is cheaper than building many little ones. However, SpaceX and their 9-engine Falcon rocket teach us a different story. Sometimes building smaller yet complicated power plants is cheaper than building fewer ones but bigger. Would be great to know more about the economic…

The real issue is surface to volune ratio of the contained plasma. This needs to be as small as possible for the containment to be effective (reduced energy losses through the surface area). So you want your reactors to be as big as possible.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#55

Post by HoochTHX »

antocv wrote: post #30
nine_k wrote: post #12

With fusion devices having trouble to confine the plasma for long times, I wonder if a massively-parallel fusion plant woud be feasible. Let's assume that plasma destabilisation does not damage the device, and is a mundane event. Build 10 or even 20 fusion devices (economy of scale!) feeding the common heat buffer, e.g. a large reservoir of a molten salt or metal. Feed conventional turbines off the heat of the heat t…

What is it with physicists and molten salt? Every battery-tech, pro-nuclear, fusion related news have to have somebody chiming in "molten salt". Just an observation.

No pressure vessel required. Meaning no explosion possible. Intrinsic safety by design.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#56

Post by gmueckl »

nine_k wrote: post #44
adrianN wrote: post #18

Earlier quoted context omitted.

Confining the plasma is easier in a larger reactor, so you might be better off building one big reactor instead of 20 small ones.

If confinement is easier in a large machine, why are not very large machines being built? If this is economically infeasible, then again, building piecemeal may be better, in the same way as taking a credit and paying interest on it might be better if you can't secure the upfront sum anyway.

Please have a look how frigging huge ITER is. There is no other way to put it. This thing has its own campus. It is also delayed because it is the first of its kind and also underfunded with some mismanagement on top. But

Re: Successful second round of fusion experiments with Wendelstein 7-X

#57

Post by gmueckl »

jerf wrote: post #45
ttul wrote: post #3

Experiments like Wendelstein remind me that the only thing holding back fusion power is money for research like this. Every year, we spend billions on fossil fuel exploration because the return on investment is quick - just think about all the wells going in to extract shale oil. What if we collectively had the will to invest this much into fusion?

If the Stellerator, or any of its descendants, turn out to be the answer to practical fusion, it would have been contingent on vast quantities of computational power being available cheaply. It does not matter how much money you poured into your Stellerator project in 1970, you could never have built the 7-X, because there would have been no way to produce that design in the first place. Personally, I think one of th…

Uhh... are you aware that the 7-X design was computed in the late 80s?

It was just an enormous challenge to build this thing. Things like building and validating the field coils required a lot of effort and some novel approaches that they had to come up with along the way.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#58

Post by twic »

semi-extrinsic wrote: post #41
emilfihlman wrote: post #19

Earlier quoted context omitted.

>BTW the waste heat could be directly reused Yes, for district heating.

Not really. For power generation as in a coal or nuclear fusion or fission powerplant, you run a multi-stage steam turbine cycle to get down to as low a temperature as possible after the final LP turbine. Because that maximizes the Carnot efficiency of the (idealised) Rankine cycle, it also maximizes real world efficiency. In practice, coing down to ~40 C (~100F) is not uncommon. And then the waste heat is basically…

You can (and at least one nuclear plant does!) run greenhouses off 40-celsius air. Maybe some tropical fish aquaculture.

But no, nothing at infrastructure scale.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#59

Post by Chemiseblanc »

nine_k wrote: post #42
bicubic wrote: post #17

Earlier quoted context omitted.

This doesn’t solve the fact that a single fusion pulse (all existing reactors are pulsed) currently consumes more energy than it produces.

I remember hearing about break-even events for a few years. E.g. from 2014: https://www.nature.com/news/laser-fusion-experiment-extracts... A design that produces e.g. 2x the energy it consumes for the startup could be viable, even if pulsed (running minutes, not months).

IIRC They were able to get net energy from the fuel versus the energy of the x-rays used to ignite it. But not in terms of the energy of the lasers used to create the x-rays by vaporizing the fuel pellet.

Re: Successful second round of fusion experiments with Wendelstein 7-X

#60

Post by nine_k »

jessriedel wrote: post #53
nine_k wrote: post #52

Earlier quoted context omitted.

You don't need to diffract the neutron flux. Instead, you can wrap (low-res) neutron-sensitive material around the stellarator tube. IDK now well would conventional photodiode or CCD work under high magnetic field, though.

That would just record the total neutron flux. It won't form an image unless you have a lens, aperture, or something similar.

It's almost as if you posit that the flux through every piece of surface is exactly the same. I suspect it's not.
Post reply on HN