No ignition at the U.S. National Ignition Facility, home to the world’s largest laser.
When it comes to nuclear reactions, you've got your fission and your fusion. Both garner energy from mass, according to Einstein’s famous E=mc2, but in a different way. Fission -- the process at work in an atomic bomb or a nuclear power plant -- gets the energy by splitting a relatively heavy atom* (heavier than iron) into lighter atoms and particles. Fusion, by contrast, combines two atoms lighter than iron into a larger atom and a whole lot of energy.
And in our world, fusion is the real deal. The fusion reactions on the sun provide virtually all of the energy that drives our world -- photosynthesis, weather, pretty much life as we know it. And with the exception of just four elements -- hydrogen, helium, lithium and beryllium -- all of the elements in our world are byproducts of stars and their fusion-filled lives.
|The size of three football fields, the National Ignition Facility houses 192 laser beams and "is capable of directing nearly two million joules of ultraviolet laser energy in billionth-of-a-second pulses to the target chamber center."|
If there were a choice between fission and fusion, it'd be a no-brainer. Fusion is the holy grail of humanity's quest for energy security.
Two downsides to fission: it requires fuels like uranium and plutonium that are in finite supply and it produces radioactive waste. Fusion produces zero waste and requires only hydrogen -- the most abundant element in the universe.
Talk about a game changer. Scientists have been thinking about how to bring this game changer into the energy game for decades. (See fusion/fission timeline.) As far back as 1946, two British scientists -- Sir George Paget Thomson and Moses Blackman -- filed the first patent for a fusion power plant.
But there have been a couple of hold-ups. To get a fusion reaction started, you need to slam the hydrogen atoms together really, really hard and that requires a lot of energy. (In a hydrogen bomb, the fusion reaction gets ignited by an atomic bomb, using fission. Not exactly the preferred method for your local fusion power plant.)
Even trickier is controlling the fusion reaction. It's one thing to make a fusion bomb, it's a lot harder to get the reaction going and keep it under control in a way that the amount of energy extracted is larger than that expended to initiate and manage the reaction.
Over the almost 70-year pursuit of the fusionary holy grail, it's been fairly common for scientists working on the problem to say that they're about 30 years away from achieving a power plant based on fusion. (See here and here.) The problem has been that while time has marched on, the 30-year horizon has remained fixed. Suffice to say it has proven to be a very tough problem.
The Big Fusion Ten
Currently there are about 10 major projects underway around the world trying to get a net-energy producing reaction. Several basic approaches are being tried to compress and heat the fuel to get ignition: lasers, magnets, X-rays and sound waves.
In recent years, Lawrence Livermore National Laboratory's Laser Inertial Fusion Energy (LIFE) project at the National Ignition Facility (NIF) has generally been viewed as the most promising: "Completed in March 2009, the $3.5 billion machine is the size of three football fields and has 192 laser beams. The now-operational facility is capable of directing nearly two million joules of ultraviolet laser energy in billionth-of-a-second pulses to the target chamber center."
With the facility's lasers up and running and breaking temperature records, hopes were running high for NIF over the past year or two. Bold statements and predictions peppered in its literature (pdf) also made a breakthrough look promising, such as “NIF will be the first fusion facility to demonstrate ignition and self-sustaining burn, as required for a power station,” “Demonstration of net energy gain from fusion fuel (On target, by end of 2012)," and (my favorite) “LIFE was the holy cow game changer.” NIF also indicated (pdf) that the timeline for the first commercial fusion power plant had shrunk -- instead of 30 years, it was now a mere 20 years away.
In February 2012, Mike Dunne, the director for energy laser fusion, explained the progress in some detail and included a qualified time line: "Overall our anticipation is that the prospects of getting to energy break-even look like roundabout six to 18 months away... It's impossible to predict in detail exactly what will happen and what the surprises will or won't be. But it feels around that time scale."
In March the journal Nature reported "Laser fusion nears crucial milestone," and quoted Lawrence Livermore National Lab director Ed Moses saying that, as far as the lab's efforts on ignition were concerned: "We have all the capability to make it happen in fiscal year 2012."
But by July 19, 2012, the fusion bubble was burst. An external review (pdf) of NIF by the National Nuclear Security Administration presented a mixed bag of praise -- "NIF has demonstrated an 'unprecedented level of quality and accomplishment'" -- and circumspection -- "considerable hurdles must be overcome to reach ignition ... [G]iven the unknowns with the present ...approach, the probability of ignition before the end of December is extremely low."
Just so happens that LIFE's funding was to run out at the end of this fiscal year, which fell on September 30. Perhaps that's why the fusion researchers were so publicly sanguine about having results by the end of 2012. So now the scientists hand off this energy holy grail to the politicians, transforming, at least for the time being, a scientific quest into a political football, or, you might say fusing the scientific and the political. What should Congress do? Scrap the project or double down? Just another spending issue poised on the fiscal cliff our folks on the Hill will have to wrestle with.
* A common fuel is the uranium isotope, U-235.
** Isotopes of hydrogen -- deuterium and tritium -- are typically used.
Image Credit: Lawrence Livermore National Laboratory.