How to construct economical fusion reactors?

[Airbrush]

They were able to get 50% more energy out of the fusion experiment at LLNL.  However, to do that required MANY GIANT LASERS.  How else can you get a fusion reaction going without so many giant powerful lasers to get it started?  It seems so impractical to have fusion energy for the masses.

Edited December 26, 2022 by Airbrush

[studiot]

11 hours ago, Airbrush said:

They were able to get 50% more energy out of the fusion experiment at LLNL.  However, to do that required MANY GIANT LASERS.  How else can you get a fusion reaction going without so many giant powerful lasers to get it started?  It seems so impractical to have fusion energy for the masses.

I can google this question as well as anybody else.

So here is some commentary on an extract from a good reply article.

Quote

https://www.iaea.org/topics/energy/fusion/background

Three main conditions are necessary for a controlled thermonuclear fusion:

1. The temperature must be hot enough to allow the ions of deuterium and tritium to have enough kinetic energy to overcome the Coulomb barrier and fuse together.
2. The ions must be confined with a high ion density to achieve a suitable fusion reaction rate.  
3. The ions must be held together in close proximity at high temperature with a confinement time long enough to avoid cooling.

Not that it is not only a question of initiating the fusion, but sustaining that fusion for long enough for it to produce enough energy for it to become self sustaining.

Simple Fusion is more common than you think, simply firing a neutron or alpha or other particle into a nucleus can produce fusion.

But that is only for one atom at a time.

 

Nature takes a statistical approach in the stars since if you have a container of gas and either wait long enough or large enough or some combination of the two, two particles will eventually collide fast enough to provide the kinetic energy for initiation.

In the laser approach you have to keep supplying the initiation energy since the process is a continual series of match strikes, rather than a continuous flame.

This avoids the containment problem, but much of the energy is then needed to keep the matches striking.

 

So the problem is a trade off between initiation, containment and sustainability.

[TheVat]

11 hours ago, Airbrush said:

They were able to get 50% more energy out of the fusion experiment at LLNL.  However, to do that required MANY GIANT LASERS.  How else can you get a fusion reaction going without so many giant powerful lasers to get it started?  It seems so impractical to have fusion energy for the masses.

We have a recent thread that discussed this, so it may work well to merge these threads.

 

 

[mistermack]

12 hours ago, Airbrush said:

It seems so impractical to have fusion energy for the masses.

Agreed. I'm interested in fusion energy, but I've never seen any explanation how a laser/pellet inertial confinement system could ever be developed that could run economically. There's no substitute for the laser, that can kick in once fusion starts. Even the explosive event of one pellet can't kick off fusion in the next one, so as far as I can see, you would need to have the lasers constantly firing, in a continuously operating system, so you will never get more electrical energy out, than you put in.

Unless someone invents a laser machine that lasts for decades, and converts about 50% of electrical energy to the final heat energy absorbed by the pellet. Maybe 10% would be enough, eventually, but there is no sign of that ever happening. 

Ideas come and go. There was a proposal to 'invent' a system that would work with smaller lasers, giving the same performance as current ones, and costing one tenth to build. It had a huge number of unknowns ahead of it, and it ground to a halt about ten years ago. 

They called it HiPer in Europe and Firex in Japan, wikipedia has a page : https://en.wikipedia.org/wiki/HiPER 

I don't think the concept has been abandoned, but nothing's happened in the last five years. 

[studiot]

1 hour ago, mistermack said:

but I've never seen any explanation how a laser/pellet inertial confinement system could ever be developed that could run economically.

 

If you have never yet seen a full description of the idea how can you be so convinced it will not work ?

1 hour ago, TheVat said:

We have a recent thread that discussed this, so it may work well to merge these threads

As I understood the OP, airbrush was asking for alternative methods to laser initiation.

So I think this is a separate subject.

[swansont]

2 hours ago, TheVat said:

We have a recent thread that discussed this, so it may work well to merge these threads.

That thread was about the NIF, which isn’t an approach that was designed with commercial energy generation in mind. So that thread isn’t discussing the question raised here.

But AFAIK nobody yet has an answer to “How to construct economical fusion reactors?” since nobody has built one yet, and there’s no guarantee that any current approach will get there.

[mistermack]

42 minutes ago, studiot said:

If you have never yet seen a full description of the idea how can you be so convinced it will not work ?

Just as you quoted me, I said "I've never seen any . . . . blah blah "

I didn't say I was conviced it wouldn't work. I'm seeing no signs that it can. That doesn't rule anything out, but some pretty drastic advances will need to be made, and there doesn't seem to be much optimism out there in people studying and commenting on it. 

One thing I did notice was that the HiPer concept needs equipment made of specialised neodymium glass, which is no longer being made. 

37 minutes ago, swansont said:

But AFAIK nobody yet has an answer to “How to construct economical fusion reactors?” since nobody has built one yet, and there’s no guarantee that any current approach will get there.

That's true, but it's really just stating that nobody can know the future. There certainly is a theoretical route to it, but nobody can say now whether there will be an insurmountable blockage on the way. 

They faced the same problem with the first steam trains, nobody knew if humans would be able to breath at speeds faster than horses can run. And before the first powered flight, there would have been huge scepticism. 

The market for energy is so huge, that if the financial institutions get a sniff that a fusion method is a goer, it's likely to get a huge investment boost. At the moment, the investment sums sound big, but when you compare them to the total energy market, they are miniscule.

[npts2020]

The biggest problem with commercialization of fusion is that it has been "a decade away" for at least the 50+ years I have followed the subject. The catch is figuring out a substitute for the gravity well of a star.

[Airbrush]

Would EVERY fusion reactor require a large number of gigantic, powerful, expensive lasers?  Or is there another way to kick start fusion?

[swansont]

3 hours ago, Airbrush said:

Would EVERY fusion reactor require a large number of gigantic, powerful, expensive lasers? 

No. Fusion reactors exist that have zero lasers. 

https://en.m.wikipedia.org/wiki/Magnetic_confinement_fusion