isleepinahammock t1_j03tnpz wrote on December 13, 2022 at 9:41 PM

Reply to comment by Robo-Connery in National Ignition Facility (NIF) announces net positive energy fusion experiment by Robo-Connery

>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.

Robo-Connery OP t1_j0401av wrote on December 13, 2022 at 10:23 PM

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.

Blarg_III t1_j04uiz9 wrote on December 14, 2022 at 2:01 AM

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.

FrickinLazerBeams t1_j068q2s wrote on December 14, 2022 at 10:55 AM

>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.

Kioer t1_j0431f6 wrote on December 13, 2022 at 10:43 PM

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

isleepinahammock t1_j045ate wrote on December 13, 2022 at 10:57 PM

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.

Kioer t1_j04b6al wrote on December 13, 2022 at 11:39 PM

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.

m-in t1_j075dpf wrote on December 14, 2022 at 3:43 PM

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.

m-in t1_j075ou0 wrote on December 14, 2022 at 3:45 PM

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.