[CGMthrowaway]

I heard that NIF was never intended to be a power plant, not even a prototype of one. It's primarily a nuclear weapon research program. For a power plant you would need much more efficient lasers, you would need a much larger gain in the capsules, you would need lasers that can do many shots per second, some automated reloading system for the capsules, and you would need a heat to electricity conversion system around the fusion spot (which will have an efficiency of ~1/3 or so).

Any truth to that?

[DennisP]

It's an experimental facility. Yes, a power plant would need much more efficient lasers, but NIF's lasers date back to the 1990s, equivalent modern lasers are about 40X more efficient, and for an experiment it's easy enough to do a multiplication to see what the net result would have been with modern lasers.

Modern lasers can also repeat shots much more quickly. Power gain on the capsules appears to scale faster than linear with the input power, so getting to practical gain might not be as far off as it appears at first glance.

These are some of the reasons that various fusion startups are pursuing laser fusion for power plants.

[boxed]

From what I understood, laser fusion needs laser efficiencies not just 40x better than what NIF uses, but like 3 or 4 orders of magnitude more efficient than the state of the art. Seems like a non-starter.

[DennisP]

NIF's lasers are 0.5% efficient. Equivalent modern lasers are 20% efficient. Both of these sources have both numbers:

https://physicsworld.com/a/national-ignition-facilitys-ignit...

https://pubs.aip.org/physicstoday/Online/31501/The-commercia...

[boxed]

80% energy loss on the way in would make the entire thing unworkable immediately. That's my point.

[DennisP]

Not at all. If you have that, plus 30% efficiency in a turbine, but you've got a 35X gain from fusion, then overall you have .2 * .3 * 50 = 2.1X overall gain.

NIF's latest shot is 2 MJ in, 7 MJ out[1], for a 3.5X fusion gain. So they've got an order of magnitude to go before getting to modestly practical levels. NIF seems to scale much better than linear with respect to the laser power, so an order of magnitude better gain is probably not a big change to the device.

(This does neglect energy loss in the hohlraum, so it assumes that direct drive laser fusion will get similar results. There are several projects working on that. Based on another comment here[2], the main reason for the hohlraum was that it made the experiment more relevant to weapons.)

[1] https://physicsworld.com/a/fusion-industry-meets-in-london-t...

[2] https://news.ycombinator.com/item?id=43935891

[bbatha]

Everything fusion reactor design needs similar gains in some part of the stack outside of the fusion parts to make it a viable power source: tokamaks need magnets to be orders of magnitude better, the lining for the reactors needs to last for much longer, the whole steam conversion mess, etc.

[DennisP]

Commercial REBCO tape is an entirely sufficient superconductor for tokamaks. At this point the limiting factor for the magnetic field is the structural strength of the reactor. Tokamak output scales with the square of size and the fourth power of magnetic field strength, and using REBCO, the CFS ARC design should get practical power output from a reactor much smaller than ITER.

[pfdietz]

Much smaller than ITER, but ITER is so huge a reactor could be much smaller and still be too big to be practical.

[DennisP]

About the size of JET. It's definitely practical in the sense that we can build it and it's likely to produce overall net power. Whether it will be competitive is another issue, and for that I agree with you that other designs, like Helion, have a better shot.

[hinkley]

I was trying to work out a joke about buying better lasers off of alibaba but it seems that despite being 30 years old they're still orders of magnitude beyond off the shelf options.

[trhway]

partially. The very efficient lasers from alibaba don't have short pulse/high power, so they can potentially be used only as the part of the system - the pumping lasers. The final nanosecond-laser is still a one-off build which though seems to be pretty doable even by a small company if they set their mind to it.

Btw, NIF achieved those recent results by adding strong magnetic field around the target (penny-shrinkers knew that tech for 20+ years :). There are other things like this around that can potentially be similarly useful. Only if somebody had money and interest ...

[hinkley]

I’ve seen some pretty wacky structures that involve mechanically forcing permanent magnets together at different orientations to create assymetric magnetic fields that are strongest where they need to be or weak where they would cause problems. Like eddy currents in electric motor housing, or insufficient hold for chef’s knives.

I know motor windings have gotten pretty funky of late to do a little bit of this, but do they do multi tesla magnetic fields that use several different windings to create the same sorts of bias in field strength? The ITER windings seem to be an extremely mild form of this.

[DennisP]

Lots of people do have money and interest: https://archive.is/BCsf5

[numb7rs]

From my time in fusion research circles, you're correct, but it's also not a simple "weapons or energy?" question. It could only have ever been a pure research facility. At the time of design, the physics wasn't certain enough to aim for net energy gain. Where the weapons research came in is in the choice of laser focus. Instead of "direct drive", where the lasers directly strike the fusion fuel, NIF lasers strike the inside of a Hohlraum, which produces X-Rays that then heat the fuel. X-Ray opacity is an important topic in nuclear weapons research.

Bear in mind that I wasn't directly involved, and this my impression picked up from conversations during my time in fusion research, which was about 10 years ago.

[willis936]

There is no need to ask for speculation. It's the top item in their mission statement.

https://lasers.llnl.gov/about/what-is-nif

>NIF is a key element of the National Nuclear Security Administration’s science-based Stockpile Stewardship Program to maintain the reliability, security, and safety of the U.S. nuclear deterrent without full-scale testing.

[aurizon]

Yes, after the test ban treaties, there was a huge push into exploring mathematical emulations of all aspects of fusion, and all assorted bombs, as well as laser ignition of pellets with these large lasers using inertial confinement of the pellet as the laser impacted it - analysing the fusion by observation of emitted neutrons. xrays etc. They issued reports from time to time(sanitised), and probably used the secret data to fine tune emulated weapons with fact points. The pellets were composed of potential fuels, various Hydrogens and Lithiums, varied in composition to explore the ignition space. A number of pellets performed well in terms of gain, but were far-far from useable fusion when the LL labs costs were factored in. I think they determined it could not ever work as a fusion energy source, but it provided data. They still mine data from it with various elemental mixes making up the pellets.

[crest]

The primary purpose of the NIF is to maintain the US nuclear stockpile without nuclear tests. The lasers very inefficient (iirc about 2%). The success they claimed is that the energy released by the burning plasma exceeds the laser energy put into the fuel capsule. Since NIF was never intended to be a power plant they don't use the most efficient lasers.

[__MatrixMan__]

Nothing about the NIF looks like a power plant to me. It's like the laser weapons guy and the nuclear weapons guy found a way to spend giant piles of money without having to acknowledge the weapons angle.

[DennisP]

A lot of people think so, but the US government openly spends way more money on nuclear weapons than on fusion research. We'll spend almost a trillion dollars on nuclear weapons over the next decade.[1] The government's fusion funding was only $1.4 billion for 2023.[2]

So it seems more likely to me that some physicists figured out how to get their fusion power research funded under the guise of weapons research, since that's where the money is. NIF's original intent was mostly weapons research but it's turned out to be really useful for both, and these days, various companies are attempting to commercialize the technology for power plants.[3]

[1] https://theaviationist.com/2025/04/26/us-nuclear-weapons-wil...

[2] https://www.fusionindustryassociation.org/congress-provides-...

[3] NYTimes: https://archive.is/BCsf5

[lotharcable]

Yes. The NIF is a weapons research lab, not a power research lab.

The purpose of it is to show that the USA is still capable of producing advanced hydrogen bombs. More advanced then anybody else.

The '2.05 megajoules' is only a estimation of the laser energy actually used to trigger the reaction. It ignores how much power it took to actually run the lasers or reactor. Even if they update the lasers with modern ones there is zero chance of it ever actually breaking even. It is a technological dead end as far as power generation goes.

The point of the 'breakthrough' is really more about ensuring continued Congressional approval for funding then anything else. They are being paid to impress and certainly they succeeded in that.

However I suspect this is true of almost all 'fusion breakthroughs'. They publish updates to ensure continued funding from their respective governments.

People will argue that this is a good thing since it helps ensure that scientists continue to be employed and publishing research papers. That sentiment is likely true in that it does help keep people employed, but if your goal is to have a working and economically viable fusion power plant within your lifetime it isn't a good way to go about things.

If the governments actually cared about CO2 and man-made global warming they would be investing in fusion technology and helping to develop ways to recycle nuclear waste usefully. Got to walk before you can run.

[hypercube33]

It's been over 20 years since ive dug into nuclear tech pretty deep but - don't we already have breeder reactors and other tech that is low waste, safer and thus we could build modern (not based on nuclear submarine) reactors in the fission category and deliver cleaner power, today? Yes there is a lot of politics especially around manufacturing, production and storage of spent fuel so all of those are probably show stoppers no matter how safe they are in reality but we aren't invested in it.

[UltraSane]

It was never intended to be a power plant but it was hoped that it would achieve a net gain fusion reaction for the first time. This turned out to be a lot harder than expected.

[hinkley]

NIF has achieved net power, right? But only if you ignore the massive, massive power losses in converting electricity to feed energy into the system.

[itishappy]

Correct. They got more bang out than they put in. The electrical-to-bang and bang-to-electrical conversions are not included.

[trhway]

ASML machine with "s/tin/DT/" looks like a prototype of such a reactor and of a fusion space drive.

[ashoeafoot]

Its a fusion & fission scientist storage facility .

[robocat]

They should also have put fusion bombs on the graph?