Revamped German stellarator should run longer, hotter and compete with tokamaks • Hacker News Board

Re: Revamped German stellarator should run longer, hotter and compete with tokamaks

#121

Post by Smoosh » Mon, Sep 12, 2022, 12:22 AM UTC

GordonS wrote: post #92

sidkshatriya wrote: post #79

Earlier quoted context omitted.

Well fusion reactors are likely to cost a huge amount of money when they do become operational. No point having them sinking in a storm. Probably just safer to charge a huge battery and put it on a ship (if you don’t want to use fossil fuels). Avoids a lot of unfoseen commercial risk. Even though you could use water for shielding, the metal container and other things that hold the reactor would be highly radioactive…

> Probably just safer to charge a huge battery and put it on a ship Large container ships burn through 16 tons of bunker oil per hour, and each journey can last up to 3 weeks - any idea what size of battery such a ship would need? I have no clue how to calculate that), but I'm guessing it would be completely impractical, even if we made huge strides in battery energy density.

> charge a huge battery

I'm hoping that some of the battery technology currently under development (such as flow batteries, or aluminium-sulphur batteries) can trade space and weight for increased total capacity. A good battery for grid storage would probably work well for a container ship.

Re: Revamped German stellarator should run longer, hotter and compete with tokamaks

#122

Post by pfdietz » Mon, Sep 12, 2022, 12:23 AM UTC

stormbrew wrote: post #119

GordonS wrote: post #91

Earlier quoted context omitted.

I don't understand this; if fission reactors were "better", we wouldn't be pouring so much into fusion? Also, if it makes a difference, I didn't mean we'd be bolting a first gen tokamak to a container ship; I meant, much later down the line, if we were able to miniaturise (similar to how we have nuclear powered subs and ice breakers).

Much more money is "poured into" fission than fusion, likely by a few orders of magnitude. There's one mega project around fusion (ITER) that has a price tag of about 1-2 billion dollars a year if you average it out over the many-decade life of the project, while any given fission plant built also costs billions of dollars. Like, whether or not fusion itself is a "meme," the idea that we spend obscene amounts of mone…

Who said it was "obscene"? You seem to be putting words in mouths.

I will say I do think money has been spent unwisely on fusion, particularly on approaches that have very little chance of success, with programmatic dysfunction that even fusion advocates have noted with anger. Chance of success does have to enter into the evaluation of whether funding is wise, or else one could argue for spending on perpetual motion machines.

Re: Revamped German stellarator should run longer, hotter and compete with tokamaks

#123

Post by stormbrew » Mon, Sep 12, 2022, 12:29 AM UTC

pfdietz wrote: post #122

stormbrew wrote: post #119

Earlier quoted context omitted.

Much more money is "poured into" fission than fusion, likely by a few orders of magnitude. There's one mega project around fusion (ITER) that has a price tag of about 1-2 billion dollars a year if you average it out over the many-decade life of the project, while any given fission plant built also costs billions of dollars. Like, whether or not fusion itself is a "meme," the idea that we spend obscene amounts of mone…

Who said it was "obscene"? You seem to be putting words in mouths. I will say I do think money has been spent unwisely on fusion, particularly on approaches that have very little chance of success, with programmatic dysfunction that even fusion advocates have noted with anger. Chance of success does have to enter into the evaluation of whether funding is wise, or else one could argue for spending on perpetual motion…

I.. wasn't replying to you? And I wasn't referring to you or the person I was replying to specifically anyways, but the common sentiment whenever this comes up.

But it is absolutely a common misconception that fusion is very well funded when, given the challenges involved, it is funded quite poorly. If it was well funded, ITER might have been finished 20 years ago.

That said I think the results would have been disappointing, it doesn't really seem like material science was there yet and it's not clear more money thrown at it then would have gotten us there.

Imo I think even if you think it's a boondoggle it'd be better to fund it well (much better than we are) now and find out than drag this slow march of wasted money on old designs and ideas out forever. The ITER funding should have probably gone to something more like milestone awards and letting a bunch of paths proliferate.

Re: Revamped German stellarator should run longer, hotter and compete with tokamaks

#124

Post by credit_guy » Mon, Sep 12, 2022, 12:54 AM UTC

Tuna-Fish wrote: post #32

ak217 wrote: post #23

Earlier quoted context omitted.

By capturing neutrons (which, not being charged, escape the magnetic confinement continuously as the reaction goes on) with a moderator blanket which is then cooled with water/steam. How to keep the blanket from quickly degrading and becoming nuclear waste seems to be an open problem (not too different from what goes on in fission reactors though) https://en.wikipedia.org/wiki/Fusion_power#Energy_capture

> How to keep the blanket from quickly degrading and becoming nuclear waste seems to be an open problem Not really. Most reactors plan to also use the neutrons to breed the tritium fuel for the reactor, so the blanket would consist of liquid metallic lithium. The only products from neutrons reacting with lithium nucleii (either 6 or 7) are He-4 and tritium. The open problem is how to safely maintain the reactor-facin…

By the way, this type of reactor is technically a hybrid fusion-fission reactor. Because when the neutron hits a Lithium-6, what happens is a fission reaction. Lithium-6 absorbs the neutron, and then splits (in Tritium and Helium) and releases energy. We are taught that fission happens only for heavy nuclei, and this is mostly true, but Lithium-6 is an exception. The energy released in the fission of Lithium-6 is quite comparable to the energy releases in the fission of Uranium or Plutonium (4.8 MeV for the fission of one Li-6 nucleus vs about 200 MeV for Uranium-235 or Plutonium-239; that energy is nearly perfectly proportional to the atomic mass).

Re: Revamped German stellarator should run longer, hotter and compete with tokamaks

#125

Post by tkubacki » Mon, Sep 12, 2022, 12:54 AM UTC

FBISurveillance wrote: post #83

moogly wrote: post #41

Earlier quoted context omitted.

> We’re still a few years away from having them in actual power plants I admire your optimism. I'd say half a century, if things go well, but I'm not convinced fusion will ever be economically feasible.

Still sooner than Linux on Desktop if you'd ask me!

Yet 1-2% of population is using Linux as of today and 0% is using fusion energy as of today. Witty but false.

Re: Revamped German stellarator should run longer, hotter and compete with tokamaks

#126

Post by Bloating » Mon, Sep 12, 2022, 1:07 AM UTC

sidkshatriya wrote: post #12

dleslie wrote: post #6

Forgive my ignorance; what with all the effort made to isolate the exceedingly hot plasma from connecting with any surface, what are the plans to extract the heat in order to generate power?

From what I've understood from previous discussions (don't know much about plasma physics though): It is a multistep challenge. Step 1: Figure out how to get a self-sustaining fusion reaction. Step 2: figure out how to extract the energy in a useful, safe, non-destructive (to the reactor) way. Doing Step 1 alone is very difficult so the've postponed Step 2 to the future. I may be wrong though.

Step 3: Profit

Re: Revamped German stellarator should run longer, hotter and compete with tokamaks

#127

Post by Knufferlbert » Mon, Sep 12, 2022, 1:18 AM UTC

credit_guy wrote: post #124

Tuna-Fish wrote: post #32

Earlier quoted context omitted.

> How to keep the blanket from quickly degrading and becoming nuclear waste seems to be an open problem Not really. Most reactors plan to also use the neutrons to breed the tritium fuel for the reactor, so the blanket would consist of liquid metallic lithium. The only products from neutrons reacting with lithium nucleii (either 6 or 7) are He-4 and tritium. The open problem is how to safely maintain the reactor-facin…

By the way, this type of reactor is technically a hybrid fusion-fission reactor. Because when the neutron hits a Lithium-6, what happens is a fission reaction. Lithium-6 absorbs the neutron, and then splits (in Tritium and Helium) and releases energy. We are taught that fission happens only for heavy nuclei, and this is mostly true, but Lithium-6 is an exception. The energy released in the fission of Lithium-6 is qui…

A thermonuclear test yielded much, much higher energy, due to unexpected lithium 7 reactions.

Re: Revamped German stellarator should run longer, hotter and compete with tokamaks

#128

Post by jodrellblank » Mon, Sep 12, 2022, 2:10 AM UTC

GordonS wrote: post #92

sidkshatriya wrote: post #79

Earlier quoted context omitted.

Well fusion reactors are likely to cost a huge amount of money when they do become operational. No point having them sinking in a storm. Probably just safer to charge a huge battery and put it on a ship (if you don’t want to use fossil fuels). Avoids a lot of unfoseen commercial risk. Even though you could use water for shielding, the metal container and other things that hold the reactor would be highly radioactive…

> Probably just safer to charge a huge battery and put it on a ship Large container ships burn through 16 tons of bunker oil per hour, and each journey can last up to 3 weeks - any idea what size of battery such a ship would need? I have no clue how to calculate that), but I'm guessing it would be completely impractical, even if we made huge strides in battery energy density.

1 ton of oil is roughly 12 MegaWatt-hours[1], so 12 MWh in a ton × 16 tons per hour × 24 hours in a day × 21 days in three weeks = ~96000 MWh or ~0.1GWh.

Here's[2] a company offering a 1MWh battery in a standard 20ft container. EverGiven[3] carries ~20,000 standard containers. So, five EverGivens?

[1] https://www.traditionaloven.com/tutorials/energy/convert-ton...

[2] https://www.geebattery.com/battery/1mw-lithium-battery-energ... (The first one I found, without looking for the smallest).

[3] https://en.wikipedia.org/wiki/Ever_Given

Re: Revamped German stellarator should run longer, hotter and compete with tokamaks

#129

Post by ncmncm » Mon, Sep 12, 2022, 3:47 AM UTC

stjohnswarts wrote: post #118

So for those of us who just want fusion without the physics explanations; is there any possibility a stellerator could actually give us a net Q (including -all- the power put into the process, and not just point of fusion) ? or is it just a good place to run fusion experiments?

Getting to net Q leaves you very, very far from useful fusion.

Structural material that can stand up to the neutron bombardment has not been identified; no one has worked on it in decades. No one knows how to breed enough tritium to fuel it, or how to extract it from the shielding ("blanket") fast enough to be useful, if indeed they did manage to breed some.

Current estimate is that working fusion is 40 years off and receding. People, and particularly startup companies, insisting otherwise are simply lying through their teeth. Securities fraud is poorly enforced.

Q is thus not very important, except maybe for getting more money.

So, there is nothing here to get excited about unless you are very keen on plasma fluid dynamics. Plasma fluid dynamics is probably the hardest kind of physics, so anybody who can do it deserves respect. It is a shame we can't find much for them to do besides fool with fusion and work on actually-useful ion propulsion.

Re: Revamped German stellarator should run longer, hotter and compete with tokamaks

#130

Post by ncmncm » Mon, Sep 12, 2022, 4:09 AM UTC

Tuna-Fish wrote: post #32

ak217 wrote: post #23

Earlier quoted context omitted.

By capturing neutrons (which, not being charged, escape the magnetic confinement continuously as the reaction goes on) with a moderator blanket which is then cooled with water/steam. How to keep the blanket from quickly degrading and becoming nuclear waste seems to be an open problem (not too different from what goes on in fission reactors though) https://en.wikipedia.org/wiki/Fusion_power#Energy_capture

> How to keep the blanket from quickly degrading and becoming nuclear waste seems to be an open problem Not really. Most reactors plan to also use the neutrons to breed the tritium fuel for the reactor, so the blanket would consist of liquid metallic lithium. The only products from neutrons reacting with lithium nucleii (either 6 or 7) are He-4 and tritium. The open problem is how to safely maintain the reactor-facin…

How to extract bred tritium at parts-per-billion concentration from hundreds or thousands of tons of "blanket" material quickly enough to cycle back into the plasma has not been studied, and might not be possible.

Furthermore, nobody knows how to get enough tritium bred in it in the first place. You need for each neutron captured to breed more than one tritium nucleus, to make up for the fraction that fails to breed any. A fusion reactor with no fuel is a remarkably expensive doorstop.