Fusion energy breakthrough...

[Genady]

Quote

The US department of energy has said energy secretary Jennifer Granholm and under-secretary for nuclear security Jill Hruby will announce “a major scientific breakthrough” at the Lawrence Livermore National Laboratory on Tuesday.

Fusion energy breakthrough by US scientists boosts clean power hopes | Financial Times (ft.com)

[Phi for All]

Here's an open link to the article: https://arstechnica.com/science/2022/12/fusion-energy-breakthrough-by-us-scientists-boosts-clean-power-hopes/

Quote

 

The federal Lawrence Livermore National Laboratory in California, which uses a process called inertial confinement fusion that involves bombarding a tiny pellet of hydrogen plasma with the world’s biggest laser, had achieved net energy gain in a fusion experiment in the past two weeks, the people said.

Although many scientists believe fusion power stations are still decades away, the technology’s potential is hard to ignore. Fusion reactions emit no carbon, produce no long-lived radioactive waste, and a small cup of the hydrogen fuel could theoretically power a house for hundreds of years.

 

 

[exchemist]

10 hours ago, Phi for All said:

Here's an open link to the article: https://arstechnica.com/science/2022/12/fusion-energy-breakthrough-by-us-scientists-boosts-clean-power-hopes/

 

Hmm, yet more breathless "breakthrough" announcements, of which I remain rather sceptical. I wonder what they mean by net energy gain, in the context of a laser-ignited inertial confinement setup. I copy below the part of the relevant Wiki article, which suggests the definition of "Q" has been altered by the Livermore group to make it seem easier to surpass, whereas, given the very low energy efficiency of lasers, it actually takes quite a lot to emit more energy than the laser needs to run.

 

Although most fusion experiments use some form of magnetic confinement, another major branch is inertial confinement fusion (ICF) that mechanically presses together the fuel mass (the "target") to increase its density. This greatly increases the rate of fusion events and lowers the need to confine the fuel for long periods. This compression is accomplished by heating a lightweight capsule holding the fuel using some form of "driver". There are a variety of proposed drivers, but to date, most experiments have used lasers.^[16]

Using the traditional definition of Q, P_fus / P_heat, ICF devices have extremely low Q. This is because the laser is extremely inefficient; whereas  for the heaters used in magnetic systems might be on the order of 70%, lasers are on the order of 1%.

For this reason, Lawrence Livermore National Laboratory (LLNL), the leader in ICF research, has proposed another modification of Q that defines P_heat as the energy delivered by the driver to the capsule, as opposed to the energy put into the driver by an external power source. That is, they propose removing the laser's inefficiency from the consideration of gain. This definition produces much higher Q values, and changes the definition of breakeven to be P_fus / P_laser = 1. On occasion, they referred to this definition as "scientific breakeven".^[17][18] This term was not universally used; other groups adopted the redefinition of Q but continued to refer to P_fus = P_laser simply as breakeven.^[19]

On 7 October 2013, LLNL announced that it had achieved scientific breakeven in the National Ignition Facility (NIF) on 29 September.^[20][21][22] In this experiment, P_fus was approximately 14 kJ, while the laser output was 1.8 MJ. By their previous definition, this would be a Q of 0.0077. For this press release, they re-defined Q once again, this time equating P_heat to be only the amount energy delivered to "the hottest portion of the fuel", calculating that only 10 kJ of the original laser energy reached the part of the fuel that was undergoing fusion reactions. This release has been heavily criticized in the field.^[23][24]

On 17 August 2021, the NIF announced that in early August 2021, an experiment had achieved a Q value of 0.7, producing 1.35 MJ of energy from a fuel capsule by focusing 1.9 MJ of laser energy on the capsule. The result was an eight-fold increase over any prior energy output.^[25]

 

[mistermack]

4 hours ago, exchemist said:

Hmm, yet more breathless "breakthrough" announcements, of which I remain rather sceptical.

Me too. They've moved the goalposts so much, it's like they want to give a false impression. I'm very keen on fusion research, but I've never seen the problem of Lazer inefficiency adressed head-on. How can there be any future for Lazer systems, without an entirely new form of Lazer? 

I feel I must be missing something, because the money keeps going in to it.

[exchemist]

35 minutes ago, mistermack said:

Me too. They've moved the goalposts so much, it's like they want to give a false impression. I'm very keen on fusion research, but I've never seen the problem of Lazer inefficiency adressed head-on. How can there be any future for Lazer systems, without an entirely new form of Lazer? 

I feel I must be missing something, because the money keeps going in to it.

I'm sure that if and when they get a significant  fraction of the fuel in these pellets to fuse, they can get back the energy needed and the losses in the laser will seem trivial. But there seem to be so many further steps to be completed in the process, before we get anywhere near a commercial reactor.  I recall doomed projects like the British Advanced Passenger Train. Very clever, but too many novel features and not enough focus on developing them through to commercial reliability. It was so full of glitches that the engineering division in Swindon lost patience and designed and built their own, less advanced, High Speed Train, which was a triumph and went on to become the backbone of our diesel expresses for several decades! 

Once they can produce significant energy gain, how do they get the energy out and how do they convert that to electricity? We had a thread on that once before, but it seemed to me there would be big challenges in getting all that working. At least a further decade. And they've got to have a commercial scale supply of deuterium/tritium pellets to fuel the thing. Will that be simple? I doubt it. And so on. 

Meanwhile we get these pot-boiling "breakthrough" announcements at regular intervals, reminding me of that line in "The Right Stuff":

"Know what makes this bird go up? Funding makes this bird go up." 😁

 

[Sensei]

The breakthrough would be if people stopped doing things for money..

[mistermack]

56 minutes ago, exchemist said:

I'm sure that if and when they get a significant  fraction of the fuel in these pellets to fuse, they can get back the energy needed and the losses in the laser will seem trivial.

That must be the goal, but I wouldn't be confident that it will ever be achievable. Fusion only takes place for a tiny fraction of time, while the inertia of the ingredients and casing keep the whole thing intact, but as it's an explosive event, it's hard to see how that tiny fraction of time can be lengthened enough. 

Whereas magnetic confinement can be run for minutes, in a continuous process, inertial confinement can't. So I can't see how you can use the energy of one pellet to cause fusion in the next one. It needs the lazer in order to inject the energy almost instantaneously, in order to work.

With magnetic confinement, you work with much lower pressures, but much higher temperatures. So there is the prospect of the heat of fusion taking over, and becoming self-sustaining at some point, without the input of external energy. I can't see how you can get to that with lazers and pellets. But like I said, there must be a way, they don't throw money away lightly.  

Edit : 

Maybe the fusion experiment is just a front, for the military research into bigger and stronger lazers ?

Edited December 13, 2022 by mistermack

[TheVat]

I share the underwhelmed state here.  As the lab director said:

"300 megajoules at the wall, two megajoules at the laser.”

 

The old "wall socket" problem.   And agree that magnetic confinement might be the better path than inertial, in terms of the engineering hurdles.  

It's laser, btw, not lazer (forum pedant rears its ugly head briefly).

It's originally an acronym.  Light Amplification by Stimulated Emission of Radiation.

[Genady]

18 minutes ago, TheVat said:

It's laser, btw, not lazer (forum pedant rears its ugly head briefly).

It's originally an acronym.  Light Amplification by Stimulated Emission of Radiation.

But, it is 'lazer' in Russian...

[TheVat]

2 minutes ago, Genady said:

But, it is 'lazer' in Russian...

Makes sense, since Russian would transliterate to keep the "z" sound of the spoken word.  And Russian S is C, which is only pronounced like the sibilant S.  

Добро пожаловать.

[swansont]

1 hour ago, mistermack said:

Maybe the fusion experiment is just a front, for the military research into bigger and stronger lazers ?

The NIF is a weapons-research facility. AFAIK there is no stated goal to make something that generates net energy. 

https://wci.llnl.gov/facilities/nif

WCI is using NIF to advance an understanding of fundamental nuclear processes and nuclear weapon performance. NIF is the only facility that can perform controlled, experimental studies of thermonuclear burn, the phenomenon that gives rise to the immense energy of modern nuclear weapons.

So this is a landmark, but not for commercial energy (at least, not directly)

[Genady]

18 minutes ago, TheVat said:

Makes sense, since Russian would transliterate to keep the "z" sound of the spoken word.  And Russian S is C, which is only pronounced like the sibilant S.  

Добро пожаловать.

Right. Such misspelling is natural for a person whose first language is Russian.

Thank you.

[exchemist]

2 hours ago, mistermack said:

That must be the goal, but I wouldn't be confident that it will ever be achievable. Fusion only takes place for a tiny fraction of time, while the inertia of the ingredients and casing keep the whole thing intact, but as it's an explosive event, it's hard to see how that tiny fraction of time can be lengthened enough. 

Whereas magnetic confinement can be run for minutes, in a continuous process, inertial confinement can't. So I can't see how you can use the energy of one pellet to cause fusion in the next one. It needs the lazer in order to inject the energy almost instantaneously, in order to work.

With magnetic confinement, you work with much lower pressures, but much higher temperatures. So there is the prospect of the heat of fusion taking over, and becoming self-sustaining at some point, without the input of external energy. I can't see how you can get to that with lazers and pellets. But like I said, there must be a way, they don't throw money away lightly.  

Edit : 

Maybe the fusion experiment is just a front, for the military research into bigger and stronger lazers ?

I don't think that's how it is meant to work. I think the concept is a stream of pellets, each one ignited in turn by the laser. So part of the electrical energy generated by each fusing pellet goes towards igniting the next one.

 

[mistermack]

27 minutes ago, exchemist said:

I don't think that's how it is meant to work. I think the concept is a stream of pellets, each one ignited in turn by the laser. So part of the electrical energy generated by each fusing pellet goes towards igniting the next one.

That doesn't sound very promising. You are compounding the inefficiency of energy delivery to the pellet by laser with having to run the lasers more or less continuously, which must surely incur maintenance problems, with such high-energy machines. I don't know much about lasers, but what I have come across is generally short-term use. 

It's so much more efficient a concept, to create a fusion burn that is self-sustaining once ignited, that just needs control input, rather than constant power input. 

2 hours ago, TheVat said:

It's laser, btw, not lazer (forum pedant rears its ugly head briefly). It's originally an acronym.  Light Amplification by Stimulated Emission of Radiation.

No, this American version is Lazer. It stands for 'Let's all zap every Russian' .

[Moontanman]

20 hours ago, Phi for All said:

Here's an open link to the article: https://arstechnica.com/science/2022/12/fusion-energy-breakthrough-by-us-scientists-boosts-clean-power-hopes/

 

My son works there! 

 

[TheVat]

1 hour ago, mistermack said:

 

It's so much more efficient a concept, to create a fusion burn that is self-sustaining once ignited, that just needs control input, rather than constant power input. 

 

This was the original concept when I first read about it back in the early Paleolithic.  A miniature sun in a magnetic bottle.  It also has the advantage in terms of "where do we put everything?" The inertial confinement with its stadium-filling array of LAZERS faces the thorny engineering problems of where you then fit all the thermal conversion stuff needed for an actual power plant.

 

[swansont]

2 hours ago, exchemist said:

I don't think that's how it is meant to work. I think the concept is a stream of pellets, each one ignited in turn by the laser. So part of the electrical energy generated by each fusing pellet goes towards igniting the next one.

AFAIK that’s not how the NIF was designed, though, since it wasn’t build as research facility for energy generation. Higher efficiency lasers or ability to continue generation wouldn’t have been a design priority. 

Hitting milestones such as this probably make it easier to justify upgrades or a new facility.

[exchemist]

1 minute ago, swansont said:

AFAIK that’s not how the NIF was designed, though, since it wasn’t build as research facility for energy generation. Higher efficiency lasers or ability to continue generation wouldn’t have been a design priority. 

Hitting milestones such as this probably make it easier to justify upgrades or a new facility.

Oh sure, but the NIF isn’t intended as a proof of the whole concept, just that laser induced fusion can be made to work. From what I have read, a commercial power station would rely on a steady stream of pellets being ignited in turn by the laser array. But then you have the problems of how to get the energy out in order to run a steam turbine, given that the laser equipment seems to take up all the space,  how to exhaust the reaction products before each ignition, how to manufacture a stream of these pellets (which I gather have rather subtle design structure), what the neutron flux does to the chamber walls........

It has to be at least another 30 years away, I feel.

[mistermack]

33 minutes ago, exchemist said:

From what I have read, a commercial power station would rely on a steady stream of pellets being ignited in turn by the laser array.

That's where the fundamental difference between magnetic and laser systems comes in. The NIF are celebrating a Q figure of 1.5 (although it's arrived at by stretching the definition a bit). Q is power produced over power in. With an array of lasers running constantly, the power-in number will always be significant, limiting the raising of Q. But with magnetic confinement, there is the prospect of reducing the power-in, as the power out is made to grow. So the smaller the input power gets, the higher the value of Q, and as power-in approaches zero, the Q number is accelerating towards infinity. (in the ideal scenario) 

So it's hoped that the highly prized and critical Q number will take off, once magnetic systems get past a certain point. One big hurdle appears to be making the heat from fusion stick around in the plasma for long enough to enable turning down of the input electrical heating. A lot of that output energy is in high energy neutrons, that can't be held in by magnetic confinement as they have no charge. Another hurdle is collecting the energy from the neutrons and turning it into steam. And another big one is finding a good method for producing and handling tritium. The theory is there for this to be done, but doing it in practice is another thing. It's those kinds of problems that the ITER project will hopefully solve. 

[TheVat]

Here is a screenshot of the Washington Post editorial today on the NIF news.  (I hope this is okay, in terms of the rule about posting just links to commercial websites - this is really just a screenshot archive, quite safe to click on):

https://archive.ph/vS6fX

 

[exchemist]

9 hours ago, TheVat said:

Here is a screenshot of the Washington Post editorial today on the NIF news.  (I hope this is okay, in terms of the rule about posting just links to commercial websites - this is really just a screenshot archive, quite safe to click on):

https://archive.ph/vS6fX

 

An excellent editorial that expresses very clearly and concisely the reservations some of us have been trying to articulate about this announcement:

- the huge gap between laser beam energy input and the power needed to run the lasers,

- the huge and yet-to-be addressed challenges in capturing the energy released and converting it into steam to run a turbine,

- the issue, once all that is solved, of bringing the costs down to a scale that enable the technology to become economic,

- and finally, given that all the above will take decades of further work with a still uncertain prospect of success, the risk the paper clearly sees of people taking fusion as yet another excuse for procrastinating on the urgent issue of decarbonising the world's economy as soon as we possibly can, using the renewable energy technologies that we have in our hands already.

  

[Sensei]

The essential key to performing effective fusion is ultra perfect mirrors that will reflect as much light as possible from them toward to the center.

 

[exchemist]

5 hours ago, Sensei said:

The essential key to performing effective fusion is ultra perfect mirrors that will reflect as much light as possible from them toward to the center.

 

That seems a rather peculiar statement. Can you explain it? Because most articles I have read say the key is confinement of the plasma, in a dense enough state for fusion to occur. 

[mistermack]

1 hour ago, exchemist said:

That seems a rather peculiar statement. Can you explain it? Because most articles I have read say the key is confinement of the plasma, in a dense enough state for fusion to occur. 

I wondered about that. The key is the combination of plasma density and temperature. If you create temperatures high enough, you can do with less density. In the favoured tritium/deuterium fuelled reaction, a lot of the heat produced is lost very quickly via high energy neutrons, which can't be kept in the plasma using magnetic fields. Maybe mirrors could be used, to reflect them back towards the centre and maintain higher temperatures?  I don't know anything about reflecting neutrons, so that's just speculation. 

[MigL]

Inertial confinement uses a pellettised Tritium target , and the lasers provide the high temperatures to momentarily 'ignite' fusion.
Wondering how difficult it would be to use a magnetically confined torus target, and provide the initial temperature with lasers, but then, rely on the 'ignited' fusion reaction to sustain reaction temperatures in the magnetically confined torus.

The neutron problem seems almost trivial ( but maybe the engineering is not ).
A heavy water moderator is used to slow the neutrons and form tritium from the deuterium, ensuring a self-generating supply of fuel.