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Robo-Connery OP t1_j03ehxz wrote

I thought I could provide some caveats to this announcements as well as some relevant context from magnetic confinement fusion, sometimes seen as a competitor but really a complementary set of experiments.

Does this announcement mean fusion as an energy source is near? Unfortunately not. I love NIF and think they do great science but fusion has long suffered from over promising so we should make sure we have appropriate context for these results.

I mentioned in the main post that NIF takes about 400 MJ per shot to power the flashbulbs that pump the lasing material, this produces a 4 MJ IR laser pulse which is frequency converted to a 2 MJ UV laser pulse. This means obviously that the 3.15 MJ is obviously not larger than the total energy spent on the system. There are undoubtedly huge energy efficiency gains to be made in the laser, as efficiency was not the goal, but this will absolutely need to be made alongside a huge gain in the experiment output, probably one comparable to the 2500% leap forward made last year. They might have it in them, we will have to wait.

The energy is obviously clearly not recovered. A working Fusion plant needs some kind of energy recovery system in place, normally considered to be a lithium blanket which absorbs neutrons, heats water into steam to drive turbines, and, as a side benefit, produces tritium fuel for your reactor.

NIF can do about 1 shot a day, at 3MJ per shot that works out something like 30 Watts. A power plant using Inertial Confinement Fusion (ICF) probably needs to do several shots per second. This is actually an extremely complicated task requiring a complete rethink of the entire machine.

Related, the shots are extraordinarily expensive. The last I heard was $60k per shot but I suspect that is years out of date. The ice pellets need to be perfect, as does the gold holraum and, with these being tiny objects, the fabrication is extremely expensive. The level of quality control as well needs to be extremely high, the nonlinearity of the compression wave that travels through the pellet presents a ridiculous physics challenge. As such I expect there to be large variance between experiments due to small imperfections or differences between the pellet and the pulse shape.

Those are the main caveats about this experiment, though others definitely exist.

How about tokamaks?

I want to compare this to similar results from tokamaks which are being compared in the corresponding news articles, they are generally the fusion experiments which people are more familiar with. I worked on tokamaks for years and as such, I probably have inherent bias. I certainly have a bias in the degree in which I am informed about the various machines.

The Joint European Torus (JET) is the record holder in terms of energy out to energy in in tokamaks. In tokamaks this ratio is called a Q value.

Aside about q value: many news articles are calculating the q of NIF and comparing it to tokamaks which, in my opinion, is inappropriate. In tokamaks the q value is defined as the ratio of alpha heating power (energy produced by the fusion reactions that is trapped in the machine) to the input heating power. The reason why this is used is down to a simple idea: if I am providing 25 MW of external heat to keep a reactor at a given temperature then you could replace this with 25 MW of internal heat and maintain the same temperature. In practice, the whole business is far more complicated and probably means you always need at least some of the external heat. We call the situation, where there is 25MW internal and 25MW external, Q=1.

There are two ways energy is emitted in DT fusion where D+T -> He + n, the alpha power (or the energy of the helium nucleus) remains trapped in tokamaks but energy imparted to the neutron escapes the magnetic field into the surroundings. In DT fusion about 80% of the energy goes to the neutrons and escapes the reactor therefore, if you had 25MW of alpha power, you would have 100MW of neutron power. You utilise the alpha power to keep your plasma hot and you use the neutrons in your steam turbines for power.

In NIF, they don't need the alpha power because the reaction is not self sustaining and indeed there is no magnetic field so it all escapes equally easily to be used anyway (although the alpha radiation is obviously collected by the walls of the machine rather than requiring an external blanket). This means when NIF quotes an energy output they mean combined alpha+neutron.

Ok so with that out the way, I have no problem with NIF using the total energy rather than the alpha power because it makes total sense, but when this is then compared to MCF experiments which only quote the alpha power it makes the hairs on the back of my neck stand up.

back on topic. So JET has obtained a q value of about 0.7 in 1996 when they ran DT campaigns, they got about 17MW of alpha power from 25MW external heating. JET are currently running DT campaigns again but are focused on sustained power output and with massive upgrades in the intervening years to the neutral beam heating system they now produce about 30 MW alpha for 45-50MW external heating. for a q of about 0.6 (but sustained for about 6-8 seconds).

ITER, the next generation tokamak experiment is tentatively expected to produce about 500MW from 50-60MW of heating but with those experiments 10 years off it remains to be seen how close they get to that goal.

I brought up the 400MJ energy budget to pump the laser and it is true that JET also has additional energy costs. The magnets alone use 800MW to power! However there is a much clearer path (in my opinion) to reducing this cost as superconducting magnets on ITER and other experiments take the power needed for the magnets to almost 0 and the other energy sinks are trivial in comparison. There is no comparable reduction available for the lasers on ICF machines which will always need to be pumped inefficiently.

In a broader sense, the steady state nature (well we can hope they will be steady state one day) of tokamaks makes the path towards energy generation clearer. In my mind, ICF just has a few more hurdles in the way (and they are properly big hurdles too).

I have rambled on far too long and my fingers are cold so I definitely have to end this comment here and I definitely have to end this on the positive note that I love NIF and I've seen some amazing results from it but the headline grabbing "energy positive fusion reaction" doesn't do it for me. With no clear pathway to the next step (a demonstration power plant) it seems to me to be almost irrelevant how much the reaction produces although I begrudgingly admit it does help fusion funding to have these stories.

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dudaspl t1_j03hykv wrote

Great commentary thanks. It's a nice breakthrough but I hate how they game the Q-factor definitions to pretend to be closer to producing energy than they really are. I'm looking forward to the commentary on tokomaks and I have a hypothetical question: if JET/ITER/the MIT one wanted to game the system, would they be able to use a lot of "external" energy to prolong/improve fusion and demonstrate a breakthrough on this stupid metric of "energy delivered to plasma"?

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Robo-Connery OP t1_j03jxui wrote

So in one sense, using only the 2MJ they use for NIF as a goal makes sense because that is the energy that is available to the pellet. In comparison the "goal" that MCF fusion uses is the external heating which consists of a bunch of different mechanisms (neutral beams, large plasma currents, radio stimulation of ions called cyclotron resonance heating are the big 3). They are both about as equivalent a number as you can get for their respective machines (unlike the comparisons of energy output which I already have griped about).

Both regimes are ignoring all the other energy costs of running the machines as well as the efficiencies of supplying that energy to the fuel.

It turns out though that the efficiencies of tokamaks (only with superconducting magnets) are just a couple of order of magnitudes better (than ICF) so including the other energy sinks wouldn't make the results look as bad. There are still efficiencies to gain for ICF both in the hohlraum design, the frequency doubling and the pumping of the lasing material for ICF machines and probably countless other places so we will see this record be smashed over and over again both by NIF and future machines.

In terms of gaming the system, it doesn't really make sense. JET could probably smash their own record if they designed the pulse differently but they are concerned with their own experimental program (which is heavily focused on understanding how ITER will perform and how to optimise ITER). It has made many sacrifices both in the machine design (e.g. using Be-W walls instead of carbon) and operation (going for long burns) which make peak power output lower but have other benefits.

The true gaming of the system for ITER would be to turn off the external heating during a shot once, that way the q-factor would be infinite but the external heating remains important for reasons other than just providing heat. For example the external heating makes it far easier to access and maintain something called H-mode or high confinement mode which makes the plasma more stable and has a far higher core temperature. As such, it isn't that sensible to design experiments along this line of thinking.

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Asleep-Emu-7977 t1_j03l9sd wrote

You seem like someone that I would love to drink some beers with. Thanks for your comments ^^ super informative!

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Robo-Connery OP t1_j03lp0k wrote

A very nice thing to say, thanks. I am glad it was informative.

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zbobet2012 t1_j055r4s wrote

This is really informative thank you. I've read a few counterpoints (I am not an expert) that ICF has over MCF and am curious as to your take:

  1. In the presser today and on the Wikipedia article for laser inertial fusion energy it's mentioned the lasers could be "upgraded" from ~0.5% efficiency to ~20% efficiency which certainly helps the case for "LIFE" systems.
    In general efficient laser generation is something which receives tens of billions per year in investment due to demands in semiconductor lithography (literally more than the entirety of investment in fusion research worldwide). While not directed at LIFE, much of the possible gains none the less come from it. (see commercial products such as https://www.trumpf.com/en_US/products/laser/euv-drive-laser/ )
  2. The relative size of the chamber significantly reduces problems with neutron embrittlement and the relative simplicity of the chamber means costs around lifecycle maintenance may be lower. (See https://web.archive.org/web/20160506011449/https://life.llnl.gov/why_life/life_advantages.php )
  3. ICF requires a lot less tritium for startup. Tritium is a rare resource, largely made from nuclear breeder reactors today. It's also useful for making fission-fusion-fission bombs (the "H-bomb"), so we don't like having a ton of it lying around for proliferation reasons.
  4. I feel that there is "no clear pathway to the next step (a demonstration power plant)" somewhat contradicted by the work layed out in the laser inertial fusion energy project. What do you feel is missing from this versus a MCF approach?
  5. I think the most interesting article I've read recently suggested combining the two: https://medium.com/fusion-energy-league/the-fundamental-parameter-space-of-controlled-thermonuclear-fusion-1c1e34206ed8. So in my very uninformed opinion folks shouldn't disregard either approach. It's quite possible a future fusion power-plant could be built on the results of ICF and MCF. Would funding both of them make sense?
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Robo-Connery OP t1_j06psgk wrote

I can try to answer these follow ups:

  1. For sure there is efficiency to be gained, 20% is definitely achievable but not for a long time (maybe only when using a non frequency doubled laser), currently the most efficient diode pumped lasers are about 10% efficient. At 20% this means a 20x improvement (if you can deliver the 4MJ rather than 2MJ to target. It is hard to imagine much more improvements over that, but there is a huge ceiling for improvements in the fusion yield. They need both to get the 5 or so orders of magnitude they need between both. I would point out though that the demands on the laser are different for the different purposes, technology translates but not without adaptation.

  2. I 100% agree that one of the few (maybe only significant?) advantages of ICF is the target chamber being very simple. They actually also benefit from a smaller neutron blanket being necessary but it isn't all positives, the number of laser beam paths needed to evenly heat the holhraum makes fitting the blanket around the outside comparatively tricky.

  3. I don't believe this is either true or an advantage. NIF uses less tritium because it does tiny shots once a day. Jet pulses every 20-30 minutes with much higher amounts of tritium in each shot because it generates far more energy (50-100x more roughly) so requires far more fuel on site. Fundamentally I disagree there is a proliferation problem, tritium is not the limiting step in making a hydrogen bomb (the fission warhead is far harder) nor is it essential, DD is sufficient. Lastly, we don't like having it around because it is hard to handle, and extremely radioactive, I don't think it is in particular due to proliferation fears.

  4. So NIF is a weapons lab but it is somewhat supported by the fusion-for-power cause too. It does what it is designed to do very well (test equation of state of high density matter, test x-ray ablation of hydrogen targets, test compression and fusion of hydrogen targets). It does fusion for power reasonably badly. Without going off on paragraphs of text, MCF problems are numerous but they are mostly understood, we know we need different divertor designs and what they should be, we know we need better ELM control, we know we need to conquer tritium breeding and material science under neutron bombardment. ICF has similar problems and then 100 other ones - in the context of fusion for power. There is no sensible plan to get a 2-10Hz repeat rate on it (versus the 0.000001Hz of NIF), there is no sensible plan to get fabrication costs down by a factor of 1000. And on top of all of that MCF machines built in the 90's are about 1-1.5 order of magnitude away from our goal in terms of raw power output. (JET at 30MW versus ITER at 500MW with the same heating). ICF is 3 or 4 away (Again alongside the 6 orders in repeat rate). The disclaimer here is that ICF is extremely new science and MCF is established so there is plenty if time for ICF to mature. I'll leave it with saying that the steady state nature of a tokamak (maybe 1000s flat top burns not being out of the realms of possibility for ITER) just makes so much more sense as a power plant than pulsed explosions.

  5. Funding both of them makes 100% sense to me, I have no issues with ICF or with laser plasma physics in general and as I've said all over the place, NIF is an incredible feat of plasma physics and engineering. I doubt a commercial reactor will ever use both in my lifetime (in fact I doubt one will use ICF in my lifetime) but I am 100% certain there will be a tokamak power plant.

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Vertigofrost t1_j06lq67 wrote

I'm not an expert either but I think I can provide some limited responses for your questions.

  1. That represents a 40x reduction in power requirements for the laser, which is only a single order of magnitude and realistically not a massive change in the energy balance.

  2. While this could be true, the current cost of a shot is over 100,000x more expensive than it would need to be for that to be true. You need shots costing pennies when they currently cost >$10,000.

  3. Tritium is naturally rare but not hard to make. Bombarding lithium with neutrons is not a super complex process, though capturing the resulting tritium requires a good set-up. Not something that's really a worry for nuclear proliferation because anyone could do it. It's currently produced in 10-20kg per year from reactors and can be stored for future use. The industrial production would need to occur for future fusion needs but its not such a big problem.

  4. The LIFE project has clear goals but not really steps to get to commercial production.

  5. I will leave this one to an expert.

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ackermann t1_j05hyvx wrote

Thanks! So, a basic question. Would a hypothetical large scale, commercial reactor work with a series of discrete pulses, or “shots”? Eg, fusion wouldn’t be happening continuously, but in pulses?

I imagine this would make them safer than fission reactors. If the reaction isn’t continuous, then it can’t “runaway” out of control, or melt down, right?

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Robo-Connery OP t1_j06qeok wrote

That is the design that they are working towards. Well NIF isn't really about a pathway to fusion power but if you are following a NIF-like design for power than it needs to be pulsed. It needs to be pulsed a couple of times a second before designs start to make sense (nif is about once a day).

Modern fission designs can also not melt down (search for Gen IV or gen V reactor designs), they are completely passively controlled and cooled.

In addition magnetic fusion devices can not melt down either, they might damage the machine if you turned them off (also JET makes a horrible bang if it is turned off early) but there is no risk to anyone, reaction stops the instant you turn it off.

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ackermann t1_j08b62v wrote

Cool thanks! So magnetic confinement devices do have continuous fusion then, unlike NIF style devices?

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Robo-Connery OP t1_j08ddiu wrote

The best ones are only matter of tens of seconds. ITER is meant to be 1000s but the ultimate goal is continuous operation. Nif and other icf machines are necessarily pulsed (because they are explosions).

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millijuna t1_j04gwfm wrote

For reference, most commercial scale power plants, regardless of energy source, use about 5-10% of their output to operate the plant itself. In Nuclear plants, this includes the energy required to operate the cooling and safety systems. This also includes the excitation energy required to operate the generators. I work with a small hydroelectric power plant (about 250kVA), and the exciter uses about 15kVA to make it operate when at full power.

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yellekc t1_j05v02w wrote

So I got a few questions. kVA is not real power, so depending on your PF it might not be consuming much. But the real question I have is about the plant capacity. 250 kVA is peanuts, the transformer at a small pump station I visited today was twice that. How does that work economically? I assume it is mostly unmanned cause it would barely generate enough revenue to cover the cost of an employee and maintenance.

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millijuna t1_j06x965 wrote

The power factor is relatively close to unity for the exciter. The actual excitation current is around 90A DC at 50V or so, though it varies.

Anyhow, the plant itself powers a remote wilderness community that's a good 50km from the nearest power pole. It's maintained largely by volunteers, and is a replacement for diesel power. The landed cost for diesel power right now would be on the order of $2.50/L for the fuel, nevermind the environmental costs. The feedwater for the hydro plant is run of the river type system, taken from a small creek that flows over a large waterfall (meaning no fish concerns).

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OwlAcademic1988 t1_j03nhyy wrote

We're making progress, but fusion energy's still nowhere near ready to be used yet. Exactly when it'll be ready, no one knows yet, but one hurdle has been overcome, which is good. Now the other hurdles have to be overcome such as energy storage, cost, efficiency, and the amount of times it can used in one day.

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[deleted] t1_j03uco8 wrote

[removed]

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Blarg_III t1_j04t7ej wrote

Better and more effective to focus on commercial transport, manufacturing processes and other various industrial waste and pollution. A carbon tax would do considerably more good for the environment than switching everyone to electric cars tomorrow.

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sw_faulty t1_j04g519 wrote

And go vegan

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m-in t1_j06nfmm wrote

Given how inefficient it is to feed people with animal products - yeah, knee jerk downvoters got something to think about first.

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Englishgrinn t1_j03ka2i wrote

As a layman who is not scientifically literate, I appreciate this simplified breakdown I could follow.

I hope I'm not just being foolish when I ask this, but: If the gains in efficiency, output and collection tech you mention are all technically possible, does that make the ultimate goal unlimited (or an arbitrarily high amount of) clean energy? A solution to our energy/climate crisis for good? Or is that just science fiction and excitement blurring my understanding? Is the real goal just another clean energy alternative? Something that could practically lower emissions as one part of a larger strategy?

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Robo-Connery OP t1_j03lmw0 wrote

So efficiencies gains are always possible but probably not unlimited. There are also fundamental science problems for both fusion regimes that need to be solved (even though I will claim ICF has far more of those problems).

> A solution to our energy/climate crisis for good?

I have a bog standard answer to this question: Just because there is unlimited fuel doesn't make it cheap. Fusion reactors will be, for the foreseeable future, extremely expensive. This means the energy they produce will be very expensive.

However, they will get cheaper as we learn to make them better and as energy prices rise there will always be a tipping point where they make economic sense. More importantly though is your mention of climate. While there are obviously some co2 emissions associated with fusion (due to the plant needing built and operated and the fuel collected etc.) the amount is trivial so the environmental benefit of fusion is huge. Traditional Nuclear power also shares many of these benefits too but produces larger quantities of waste (though fusion still causes nuclear waste due to neutron activation of materials) and requires larger quantities of fuel.

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m-in t1_j06ohmr wrote

It’s also worth mentioning what does it mean to be “expensive”: it’s not about numbers in a database in a bank somewhere. It’s about how much energy it takes to make all the stuff that you need for a fusion power plant.

Let’s now imagine that we’ll get to a stage when the first commercial fusion plant can be built

The design, build, and commissioning process of that plant will take about as much energy as that plant will produce through its entire lifetime. It’ll be basically sunk cost for investors just to get the design and operating process shaken down and ready for the next build. And that’s optimistic.

High tech plants like that take hundreds of thousands of man-hours of work, if not millions. While that work is going on, you’re spending resources just to feed and keep the workforce happy - a gross oversimplification, but think of how many resources it takes to run the equivalent of a large residential subdivision. That’s just to keep those people alive and happy so they can do their 8 hours of work per workday. And those people live across the planet pretty much, since many different industries will be providing raw materials, machining, design, assembly, and a host of other services.

As the technology advances and more plants are built, it’ll become profitable to operate one. Not the first one. Not the second one either.

*Happy workforce is a relative term and I’m far from claiming working people everywhere are happy with their jobs. What we should strive for, though, is for big projects to contribute to workers’ well-being everywhere in some way.

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yves759 t1_j04mipr wrote

Whether an energy is "clean" or not, whatever that means, the use of it is by definition not clean, energy is our power to act on/transform the environment : the vast amount of energy that fossile fuel today provides, is what allows to build roads, houses, fish the whole oceans, cut forests like crazy, etc

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rmzalbar t1_j05ou6e wrote

But with enough "free" energy you can reduce or do away with many of those things. Farming could be replaced with high-density hydroponics instead of slash-and-burn, oil burning transportation could be replaced with electric, etc. Getting humans as a global community to stop doing.. well, everything.. and sit on their hands in the darkness and starve, is not realistic because they simply won't do that. But if you can offer them something that is cleaner and better they'll take it.

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yves759 t1_j060v0m wrote

Well, regarding "and sit on their hands in the darkness and starve, is not realistic because they simply won't do that." , it might not be a matter of "choice" at all ...

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rmzalbar t1_j062hea wrote

Oh, of course. Nevertheless, they'll continue to destroy stuff in order to put the next meal on the table or iphone in their hands, regardless of how badly you might want them to think long term.

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droans t1_j04pt44 wrote

Thanks for this.

At what point would you say that fusion power is more of a political or engineering question than it is a scientific and physics question?

How likely is it that fusion really won't be a feasible energy source, whether that be due to the science not working in our favor or because the cost/designs aren't feasible?

Which design shows more promise? Is it likely that commercial plants will utilize a mixture of the designs? Is it likely that both designs could be the basis for future plants?

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Robo-Connery OP t1_j06narj wrote

> fusion power is more of a political or engineering question than it is a scientific and physics question?

I'd say not yet.

There are still fundamental physics questions that remain in terms of optimising the plasma, you have 100's of knobs to tweak when designing and operating a machine and we aren't sure exactly what combinations are optimal - though we are getting better, modern machines achieve a huge milestone, called H-mode access, almost instantaneously when this used to be something that took years of tweaking parameters.

Engineering challenges will take over significantly in a post ITER world, when we are trying to design a demonstration power plant.

Once that has been successful it will become a political and economic issue, when is it worthwhile to invest, where should we build them, what does the energy landscape of our country look like 50 years down the line.

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theoatmealarsonist t1_j05oxwu wrote

I appreciate you taking the time to add context to the announcement today!

Given that ICF and tokamak MCF reactors are still decades out from commercial viability, what are your thoughts on private companies like Helion and General Fusion? It sounds like their approaches are matured enough that they could be generating electricity in the relatively short term. I'm guessing that the theoretical net energy gain for their approaches is a lot lower, but appears commercially viable and ready to use in the relatively short term. For example, General Fusion is essentially making a pulsed fusion driven piston engine, and Helion doesn't actually need ignition as they're inducing a current from the magnetic field fluctuations in a pulsed fusion reaction. There are others out there as well, I've just seen them highlighted recently and was curious how they stacked up against conventional research directions.

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Robo-Connery OP t1_j06qymk wrote

Some of them are blowing hot air for investment reasons, some of them are just flat out scams. The remainder are simply doing very simple jobs and acting like they are reinventing the universe.

I've seen some propositions that rely on things like magnetic bottles for confinement rather than tokamak designs and they just will not ever work, we moved on from those designs 60 years ago for good reason.

More players in the game means more progress too so I'm not bothered by their presence - as long as it doesn't reduce funding for the mainstream experiments by virtue of having to necessarily criticise them in order to justify their own work.

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Mobile-Ground-2226 t1_j088e1l wrote

But if more players are in the arena doing things that are just scams or marketing (the tech bros "out-innovating" the problem) doesn't it discredit the entire field for a while after the inevitable flop and cause a reactionary effect to funding? I saw this happen in biofuels with the algae and cellulosic fuels, it only recently started to recover, and probably mostly thanks to high oil prices and CA LCFS incentives.

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Robo-Connery OP t1_j08d4r0 wrote

Maybe. Fusion is sometimes seen as a bit of a joke already because while experts are very realistic amongst each other at some point in the dissemination of results the headlines become inaccurate and exaggeratory.

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Mobile-Ground-2226 t1_j08njys wrote

Yeah, but a lot of the investment crowd is discovering it for the first time. I did a summer internship at D3-D back in the '90's and people were making the 25 years away joke back then, so I'm glad there are people like you who will chat with us laypersons about ground truth.

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NickDanger3di t1_j09taif wrote

Disappointing that the average US citizen, and the media, have so little understanding of fusion that this is taken to mean we can start building fusion power plants now. My concern is the funding; US government funding for fusion research is $700 million per year; US government funding for subsidizing fossil fuels (mostly for exploring new sources) is a whopping $20 Billion per year.

Where would fusion be if we started funding fusion research and development for $20 billion every year? NIF has made a breakthrough; they have created the first fusion reaction to ignite here on earth. Proving that it can be done. But with only $700 million a year, it's not going to lead anywhere very quickly. I'm pretty sure we pay more than that to subsidize cheese production, so it can be stored in caverns and get moldy, requiring even more money to dispose of the rotten cheese. Makes me sad and frustrated.

Edit: information available on the whole Government Cheese thing is confusing; but it seems the government is down to a mere 300 million pounds of these days. My knowledge of cheese prices being restricted to the local grocery store, says that's around $1.5 billion at retail prices. So at wholesale, maybe the same as fusion gets?

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Robo-Connery OP t1_j0bgk2b wrote

I agree with the sentiment here but I would point out that the first ever successful controlled fusion ignition (so we exclude the obvious fusion weapons) was in 1958 with a theta pinch machine. Fusion is achieved dozens of times a day at a large number of reactors and nif has routinely ignited fusion since it was commissioned. Nif achieved a milestone with this experiment but not the first ever fusion ignition.

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drunkdoor t1_j0s9r4a wrote

Is this article completely wrong then by saying the first ever ignition event just happened?

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

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Robo-Connery OP t1_j0uuk42 wrote

Yes that article is completely wrong.

It even clarifies in the first section:

"Ignition should not be confused with breakeven, a similar concept that compares the total energy being given off to the energy being used to heat the fuel."

edit:

it also changes its definition multiple times throughout the article, that article is horrible. The definitions they give means NIF either achieved it on its first ever experiment or it is impossible for NIF to achieve it (id personally say the latter is true) it also claims it is a necessary pre-req for power - not true remotely. It also precludes all tokamaks from ever achieving it due to external heating being used for plasma control and h-mode access even if internal heating is 10 times higher (or 1000 or a billion).

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isleepinahammock t1_j03kni5 wrote

So here's one thing I'm wondering. What's the proliferation risk of pulsed fusion technology?

So, as you note, a LOT of improvements would need to be made to this system before pulsed fusion could ever be possible. So we would need far, far better lasers, better in power, charge time, and efficiency, in order to make a practical pulsed fusion reactor.

But let's say we do manage to build these lasers. What I wonder is, what ELSE can you use these hyper-efficient, super-powered lasers for? Two disturbing scenarios that have crossed my mind:

  1. Could you build a pure fusion bomb, a thermonuclear weapon without any uranium needed at all? In principle, if you can direct enough energy at a sufficiently large chunk of fusion fuel, you could create a nuclear explosion without any uranium, plutonium, etc. Our current non-proliferation strategies rely on monitoring and tracking fissile materials like uranium, plutonium, etc. But this might make it possible to build nuclear weapons out of only mundane materials, no uranium needed. It will probably be a long time til we have to worry about someone building a nuke in their basement. But if sufficient numbers of sufficiently high-powered lasers find their way into many industries and applications, this might be something that we have to worry about.

  2. Creation of fissile materials from non-fissile materials. Miniaturizing the entire laser setup of NIF (let alone the super-NIF I was thinking of in part 1) small enough to fit on top of a missile may never be possible. However, what if someone were to use an NIF-type facility to breed fissile materials from non-fissile ones? I don't know enough about the nuclear chemistry to suggest possible elements. But there probably are some non-fissile elements that are abundant, currently unmonitored by international agencies, and can be transmuted into fissile materials through heavy neutron bombardment. What happens if you build a target for the NIF (or a super-NIF) filled with a combination of fusion fuel and some transmutable element? For example, imagine if someone figured out that ordinary lead could be transmuted into U-235 in the intense neutron flux of a super-NIF facility. In such a world, every fusion reactor we build would be a proliferation nightmare. Every one would have to be continuously monitored to make sure some nefarious government or private company isn't using it to turn mundane, untraceable lead into plutonium or similar.

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Robo-Connery OP t1_j03mxri wrote

> What's the proliferation risk of pulsed fusion technology?

I mean the flippant answer is that you don't need lasers to make a bomb, it is much easier to compress your fuel with a fission explosion than with a laser. You also might be envisioning some sci-fi scenario where you lob your pellet at them then lase it to explode but that simply isnt possible, the symmetry required in the compression is almost absolute and the experiment requires a vacuum.

>Could you build a pure fusion bomb, a thermonuclear weapon without any uranium needed at all?

Yes, NIF though has a an entire building that generates the laser pulse and took years to build and it could only blow itself up, not easy to drop it on anyone.

As for question 2.

>were to use an NIF-type facility to breed fissile materials from non-fissile ones?

I believe there are just better ways to do this, and I mean much much much better ways. There are other neutron sources which are cheaper, easier and produce better neutrons than NIF and the actual fusion explosion doesn't help except as a neutron source. The most obvious neutron source is a fission reactor but there are others, any country could build a breeder reactor if they wanted to (though they might face consequences if they were seen to be using it for weapons tech).

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isleepinahammock t1_j03tnpz wrote

>I believe there are just better ways to do this, and I mean much much much better ways. There are other neutron sources which are cheaper, easier and produce better neutrons than NIF and the actual fusion explosion doesn't help except as a neutron source. The most obvious neutron source is a fission reactor but there are others, any country could build a breeder reactor if they wanted to (though they might face consequences if they were seen to be using it for weapons tech).

There are other ways to do it. But the key thing to worry about is the production of fissile materials from entirely mundane elements. Sure, you can make plutonium in a breeder reactor, but you still need to at least get a hold of a good amount of U-238 to do so. If today I call up a uranium mine and ask to buy a few hundred tons of yellow cake, I'm going to have some very angry-looking men carrying automatic weapons showing up at my front door very quickly. If I want to do anything involving uranium, I need to obtain special licenses and permits, plus regular inspections to make sure I'm not doing something I shouldn't be doing.

But think of the incredible lasers needed for a practical pulsed-fusion plant. This current step is good progress, but really we need to do about 100x better if we want a practical pulsed-fusion plant. We need lasers that can get 100 MJ of fusion energy for 1 MJ of input laser energy; and they need to be able to fire several times a second 24 hours a day, 365 days a year. We need laser tech far, far beyond our current levels.

And the thing is, that technology is simply far too useful to see it used only in fusion power plants. Highly precise, high-power, high-efficiency lasers have all sorts of applications, including in manufacturing, communications, even things as mundane as drilling deep holes. If we get the tech needed for a pulsed-fusion plant, these lasers are going to be used everywhere, not just in fusion plants.

And that's the real concern. You have to worry about some terrorist group buying some surplus mining or manufacturing equipment, and then using it to breed lead into plutonium. Or, if the knowledge is public enough, they might just build the lasers themselves. It represents a path to nuclear weaponry without ever having to get a hold of an ounce of uranium.

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Robo-Connery OP t1_j0401av wrote

The design goals for those commercial purposes are completely worlds apart. There are already much better suited lasers to the jobs you list than NIF which would be completely useless in any of those applications. Completely useless Even if it wasn't useless (which again it would be) it costs billions which isn't exactly gonna come down to a level that makes sense as a commercial product.

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Blarg_III t1_j04uiz9 wrote

Anyone who has, and can run, a fusion reactor (Or some super-powerful laser array) is more than capable of making their own nuclear bombs more easily by another method.

>I'm going to have some very angry-looking men carrying automatic weapons showing up at my front door very quickly.

You can buy it online in the US, though not in particularly large amounts. Buy a company with a legitimate use for it, order it in bulk and voila, you have Uranium 238.

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FrickinLazerBeams t1_j068q2s wrote

>Highly precise, high-power, high-efficiency lasers have all sorts of applications, including in manufacturing, communications, even things as mundane as drilling deep holes. If we get the tech needed for a pulsed-fusion plant, these lasers are going to be used everywhere, not just in fusion plants.

These lasers have absolutely no use in any of those applications. You're talking about a totally different definition of "high power".

>And that's the real concern. You have to worry about some terrorist group buying some surplus mining or manufacturing equipment, and then using it to breed lead into plutonium. Or, if the knowledge is public enough, they might just build the lasers themselves. It represents a path to nuclear weaponry without ever having to get a hold of an ounce of uranium.

That's hilariously absurd. Never will any kind of laser used for manufacturing, telecom, etc. be usable for laser driven fusion or nuclear weaponry. That's not how any of this works.

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Kioer t1_j0431f6 wrote

Lasers shoot photons my man. There is no feasible way to transmute lower Z elements into higher Z elements with a laser. It is simply not possible. You might be able to induce beta decay on some isotopes but not at a scale to produce any measurable quantity of SNM

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isleepinahammock t1_j045ate wrote

Fusion reactions can be triggered by lasers, and the fusion reaction emits most of its energy as high-energy neutrons. Literally the entire basis of fusion reactors is transmuting lower-Z elements to higher-Z elements.

Yes, hitting a nucleus with a photon will not cause it to gain new nucleons. However, intense laser light can cause nuclei to collide with sufficient energy to fuse. That's literally the entire basis for the fusion processes discussed here.

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Kioer t1_j04b6al wrote

Just due to binding energy fusion does not apply to elements larger than iron. To create any of those we need neutron or proton capture. And if you're creating this massive state of the art laser array to create fusion to produce neutrons why not just build a neutron source to begin with? There are thousands of high flux neutron beams all over the world. Just build one of those for about 1/1000000 of the price or better yet just purchase one from a commercial supplier.

I'm not trying to be rude or anything, but proliferation of nuclear material is the least of the problems with fusion. It is just entirely unfeasible and way way way more expensive and technologically advanced than any other method.

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m-in t1_j075dpf wrote

Lasers don’t directly induce fusion. They take some other “working fluid” like gold plasma and dump energy into it. That then can fuse something else that’s the actual nuclear energy source. Of course dumping a bunch of photons close to the visible spectrum (UV and IR are not far at all) will not cause anything to fuse on its own - not even if the photons had unceasingly high energies AFAIK.

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m-in t1_j075ou0 wrote

The lasers we use for practical purposes in production environments you mention only share the name and general operating principle with those used at NIF. Calling both “lasers” is technically correct but practically absurd.

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zbobet2012 t1_j0599dj wrote

Wouldn't the largest proliferation risk simply be the increased knowledge of the high density regime ICF uses making it easier to make a fission-fusion-fission bomb (an "h-bomb")? I believe some of results of research at NIF are classified no?

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Robo-Connery OP t1_j06q0s8 wrote

Absolutely correct. Tonnes of high density matter stuff is classified, if you do work on this in general with laser plasmas the government is gonna come and steal your work (has happened to acquaintances).

I think though the limiting factor in making a passable h-bomb is the fission warhead though, not the fusion stage. The US and other nuclear powers care about this stuff to make efficient and clean weapons rather than to just make weapons (they made them in the 50s without any lasers or plasmas).

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FrickinLazerBeams t1_j068cce wrote

>What's the proliferation risk of pulsed fusion technology?

Absolutely zero.

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FrickinLazerBeams t1_j0686rz wrote

I think magnetic fusion is more likely to provide a path to power generation, but this:

>There is no comparable reduction available for the lasers on ICF machines which will always need to be pumped inefficiently.

is simply not true at all. Diode pumping is dramatically more efficient. Flashlamps are simply easy and reliable.

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Robo-Connery OP t1_j06shnx wrote

I think that I did not mean that there is not large efficiency gains to be made just that they can not eliminate their biggest inefficiency, unlike MCF which just removes the iron core magnets. I also disagree that this fundamentally changes the point I made. The most efficient diode pumped lasers are about 10% efficient (the primary beam on NIF when still IR is about 1% efficient.) and there is speculation that this could be 17%-18% in the medium term. So there is maybe a 20x improvement available.

The swap from iron core magnets to superconducting magnets completely eliminates that energy cost and is current technology, if JET had superconducting magnets in 1996 it would have reduced its energy usage by a factor of 40. This reduction is obviously present in all next gen tokamak designs.

The majority of the improvements therefore still need to come from target yield where I believe they need to hit several hundred MJ if not higher, so a further 2-2.5 orders of magnitude needed there. (NIF can handle up to something like 50 I think in terms of the chamber max, not the fuel max).

In comparison JET is about 1 order of magnitude less than ITER and ITER is larger in terms of power than power plants will be.

I would also be remiss if I didn't take the opportunity to point ouit that 6 orders of magnitude in repeat rate are needed.

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[deleted] t1_j06c4p0 wrote

[deleted]

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mcchanical t1_j09zge4 wrote

Oh yes. That's definitely what you should have read from this conversation.

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