Fusion? Not yet, but getting close

[rhoenix]

The dream of igniting a self-sustained fusion reaction with high yields of energy, a feat likened to creating a miniature star on Earth, is getting closer to becoming reality, according the authors of a new review article in the journal Physics of Plasmas.

Researchers at the National Ignition Facility (NIF) engaged in a collaborative project led by the Department of Energy's Lawrence Livermore National Laboratory, report that while there is at least one significant obstacle to overcome before achieving the highly stable, precisely directed implosion required for ignition, they have met many of the demanding challenges leading up to that goal since experiments began in 2010.

The project is a multi-institutional effort including partners from the University of Rochester's Laboratory for Laser Energetics, General Atomics, Los Alamos National Laboratory, Sandia National Laboratory, and the Massachusetts Institute of Technology.

To reach ignition (defined as the point at which the fusion reaction produces more energy than is needed to initiate it), the NIF focuses 192 laser beams simultaneously in billionth-of-a-second pulses inside a cryogenically cooled hohlraum (from the German word for "hollow room"), a hollow cylinder the size of a pencil eraser. Within the hohlraum is a ball-bearing-size capsule containing two hydrogen isotopes, deuterium and tritium (D-T). The unified lasers deliver 1.8 megajoules of energy and 500 terawatts of power—1,000 times more than the United States uses at any one moment—to the hohlraum creating an "X-ray oven" which implodes the D-T capsule to temperatures and pressures similar to those found at the center of the sun.

"What we want to do is use the X-rays to blast away the outer layer of the capsule in a very controlled manner, so that the D-T pellet is compressed to just the right conditions to initiate the fusion reaction," explained John Edwards, NIF associate director for inertial confinement fusion and high-energy-density science. "In our new review article, we report that the NIF has met many of the requirements believed necessary to achieve ignition—sufficient X-ray intensity in the hohlraum, accurate energy delivery to the target and desired levels of compression—but that at least one major hurdle remains to be overcome, the premature breaking apart of the capsule."

In the article, Edwards and his colleagues discuss how they are using diagnostic tools developed at NIF to determine likely causes for the problem. "In some ignition tests, we measured the scattering of neutrons released and found different strength signals at different spots around the D-T capsule," Edwards said. "This indicates that the shell's surface is not uniformly smooth and that in some places, it's thinner and weaker than in others. In other tests, the spectrum of X-rays emitted indicated that the D-T fuel and capsule were mixing too much—the results of hydrodynamic instability—and that can quench the ignition process."

Edwards said that the team is concentrating its efforts on NIF to define the exact nature of the instability and use the knowledge gained to design an improved, sturdier capsule. Achieving that milestone, he said, should clear the path for further advances toward laboratory ignition.

So - the problem is not power generation anymore. The problem is that the fuel capsule burns unevenly, and they're currently finding out why.

That's one hell of a milestone.

[rhoenix]

And another milestone reached:

Researchers at the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in California have made a major breakthrough toward achieving self-sustaining nuclear fusion.

The NIF is home to the highest-energy laser in the world—a composite of 192 lasers, all trained on one tiny pellet of the hydrogen isotopes deuterium and tritium. The pressure from the lasers is designed to compress the fuel pellet (inside a dime-sized cylinder called a hohlraum) until the deuterium and the tritium fuse together, releasing a huge burst of energy. The process is designed to replicate the inside of a star, mimicking the Sun's long-lasting, self-sufficient energy creation here on Earth for a vast, cheap supply of power.

Scientists have been working towards creating fusion energy in the lab for decades, but creating a system that puts out more energy than it takes in has so far proved impossible. Now, the NIF has reportedly conducted an experiment in which the amount of energy released by the fusion reaction in the hohlraum was greater than the amount of energy that went into the pellet.

This is still a step away from ignition, the point where the reaction releases as much energy as went into the system as a whole, since the system isn't totally efficient and some of the laser energy that goes in doesn't reach the pellet. But it's a major breakthrough nonetheless, the first time in the world that scientists have been able to achieve this level of (minor) efficiency in a fusion energy reaction in the lab.

When the NIF started operating in 2009, the lab promised it would achieve ignition by September 2012, a deadline it obviously blew past. Since ignition researchers couldn't predict when ignition would be achieved, or even what they were doing wrong, the NIF's government funding has been in jeopordy. Proposed budget cuts for the NIF for fiscal year 2014 would reduce the lab's funding by $60 million. "It is impossible at the moment to predict whether ignition can be achieved," Senator Diane Feinstein, a member of the Senate Appropriations Committee, said in May. "Now is the perfect opportunity to reassess the goals of this program." In other words, the government doesn't want to pour its billions into a high-energy pipe dream.

But it seems the NIF has plugged at least some of the leaks allowing energy out of the system. How exactly they managed to achieve this feat, we don't yet know, although a review in Physics of Plasmas published online this summer detailed some of the potential causes of the NIF's performance issues. John Edwards, the associate program director for inertial confinement fusion and high energy density (HED) science and the study's lead author, explained in a press statement that "the NIF has met many of the requirements believed necessary to achieve ignition—sufficient X-ray intensity in the hohlraum, accurate energy delivery to the target and desired levels of compression—but that at least one major hurdle remains to be overcome, the premature breaking apart of the capsule."

So not quite at the point where it's releasing more energy back total than went in, but it's now at the point where it's releasing more energy than that which was used to shoot the pellet directly.

Given everything else happening, this seemed like good news.

[Josh]

C'mon guys, daddy needs a new Mr. Fusion.

[Batman]

They've been promising me fusion is 'just around the corner' for longer than I've been alive in the real world. I'll get excited when somebody actually gives us an economically viable fusion reactor. You know, the one that lets us toss out (or at least seriously cut back on) fossil fuels or those atrociously inefficient (and expensive) renewable energies approaches.

[rhoenix]

They've been promising me fusion is 'just around the corner' for longer than I've been alive in the real world. I'll get excited when somebody actually gives us an economically viable fusion reactor. You know, the one that lets us toss out (or at least seriously cut back on) fossil fuels or those atrociously inefficient (and expensive) renewable energies approaches.

Fair enough, but getting out more energy than you put in is one hell of a milestone for the technology.

[Lys]

Batman, listen to Michael Kaku, he knows what he's talking about. The short version is that, unlike the past 60 years, have now have actual physical plant that is capable of doing more than leaking plasma all over the place. We're basically right on the edge of the break-even point, which I think is a reason to get excited. Frankly, commercially viable fusion is unlikely to lead to the immediate tossing out of fossil fuel energy sources. There will be considerable costs involved in the development and construction of such a thing that will have to be amortized into the price of the energy it produces, as well as not inconsiderable running costs from requiring high end technical expertise to keep the power plant running. What we are likely going to see is a slow transition away from fossil fuels and toward fusion power, much like we were seeing with nuclear power until a coalition of stupid peaceniks and greenies mixed with crappy public education on the subject caused progress on that area to stall and die. Which is really unfortunate because nuclear power has already saved the lives of nearly 2 million people, and would have saved more had progress continued apace on that front.

[rhoenix]

Batman, listen to Michael Kaku, he knows what he's talking about. The short version is that, unlike the past 60 years, have now have actual physical plant that is capable of doing more than leaking plasma all over the place. We're basically right on the edge of the break-even point, which I think is a reason to get excited. Frankly, commercially viable fusion is unlikely to lead to the immediate tossing out of fossil fuel energy sources. There will be considerable costs involved in the development and construction of such a thing that will have to be amortized into the price of the energy it produces, as well as not inconsiderable running costs from requiring high end technical expertise to keep the power plant running. What we are likely going to see is a slow transition away from fossil fuels and toward fusion power, much like we were seeing with nuclear power until a coalition of stupid peaceniks and greenies mixed with crappy public education on the subject caused progress on that area to stall and die. Which is really unfortunate because nuclear power has already saved the lives of nearly 2 million people, and would have saved more had progress continued apace on that front.

There's also the small but notable fact that nuclear fusion reactors don't melt down and leak radioactive sludge everywhere, unlike the nuclear fission reactors that we current have in production; they'd simply shut down, if I read the design right.

So - much more potential power, and less mess. It just takes a bit more engineering to get it right, and that makes sense to me.

[Lys]

That's incorrect rhoenix, the plant being unable to melt down and leak radiative sludge everywhere is exactly like the fission reactors we have in production. Modern fission reactors cannot melt down, the only ones that can and have are obsolete 1960s designs. Of those the only a minuscule fraction actually did suffer a melt down, and of those only one actually resulted in a disaster, and then only due to the absence of a containment dome. Meanwhile in India, right around the same time as Chernobyl, a gas leak at a pesticide plant killed thousands of people and severely injured tens of thousands more. Comparable to Chernobyl, except people aren't scared of pesticides like they are of evil radiation. Which is too bad really, because on the whole the power of the atom saves lives.

The primary benefit of fusion power is that once the technology matures it promises relatively cheap power that can avail itself of a plentiful fuel derived from simple sea water. The lack of radioactive elements is primarily a public relations benefit, which is not to say it isn't a practical benefit too, but it's not really the most important factor.

[rhoenix]

Fair point then - I'll have to look more into the modern designs a bit more; I'll admit I haven't done so.

Having a cheap and easily available source of fuel though... that would be another great thing for the world's fuel economy.

[Josh]

Okay, not a nuke engineer (thank god, given the weirdos I've dealt with) but my understanding is that even the modern designs can melt down under the right confluence of circumstance, but it's very, very unlikely.

However, a meltdown is not what a lot of people perceive it as- the Civ-style event with the horns blaring and the nuclear bomb effect. It's the core melting containment, which means it can theoretically leak radioactive ooze. This would obviously not be a good thing, but a Bhopal scenario is definitely a lot worse, or a gas plant explosion. (There've been like two in my lifetime at a plant about forty miles away, for example. Both killed multiple people.)

I would have no problems living near a conventional modern nuclear reactor. I'd be considerably more comfortable with that than living near a coal or gas plant. I do live sixty miles from a radioactive waste disposal facility that's ramping up to dispose of the hottest material going, and I'm not losing a bit of sleep over that either.

[Lys]

Meltdown is an informal term so it could in theory mean any damn thing. The technical terms is something like "core melt incident", so strictly speaking a melt down is about the core overheating and, well, melting. Whether a containment breach happens is rather irrelevant, Three Mile Island suffered core melting but had no breach of containment. In general reactors with hardened primary and secondary containment have little risk of containment breaches even in the event of the core melting.

Also, no, there are designs that cannot melt down, it's physically impossible unless the reactor wasn't built to spec or the safety mechanisms are physically destroyed by some outside force (say a 2000 lbs bunker buster). For example there's the CANDU reactor, a 60s design that's not obsolete in part because it's very safe and will not suffer core melting. It has a number of possible failure modes, but a melt down is simply not one of them.

[Batman]

Heck from what I know modern reactors are designed to survive a freaking plane crash. Modern fission plants are among the safest and cleanest means of electricity production in existence. Yes, you've got to store the spent reactant somewhere eventually, but at least you get to decide where to store it and secure the place accordingly. Fossil fuels? We just dump the stuff into our surroundings. Yeah, that sounds safe.

And I didn't mean to imply that fusion would magically replace fossils as the power generation method of choice (if nothing else the 'everything nuclear is EVIL!!!' crowd will see to it being a slow long and tedious process), but at least we'd have the option. And given hydrogen is one of the three most abundant substances in the universe and, as you said, to be had in droves from Earth's oceans alone, it's bound to eventually win out economically once we manage to make it work.

And yes, I'm massively sceptical. They promised me I'd be driving Terry's flying batmobile right now fifty years ago. I'll be most delighted if this turns out to be that one major breakthrough and viable fusion becomes viable down the line, and you can call me a doomsayer to your heart's content, because if that happens, that's what I'd be. I prefer looking like a pessimistic fool for not expecting it to work when it does over being all bouncy and then disappointed (for the nth time) when it doesn't.

[Cynical Cat]

Radiation is scary and all that and nuclear plants need to be one of the safer designs and built to survive the once in millenium earthquakes/tsunamis/whatever (because sooner or later one's going to be hit by that) and we have to deal with the waste but these things can be done. Coal kills more than 20,000 a year and dumps more radioactive crap into the atmosphere as part of normal operations. Because those deaths are from respiratory problems in high smog areas no one gives a crap because they aren't big scary accidents.