Fusion "Breakthrough" At National Ignition Facility? Not So Fast

sciencehabit writes "One unintended effect of the U.S. federal shutdown is that helpful press officers at government labs are not available to provide a reality check to some of the wilder stories that can catch fire on the Internet. They would have come in handy this week, when a number of outlets jumped on a report on the BBC News website. The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California, it reported, had passed a 'nuclear fusion milestone.' NIF uses the world's highest energy laser system to crush tiny pellets containing a form of hydrogen fuel to enormous temperature and pressure. The aim is to get the hydrogen nuclei to fuse together into helium atoms, releasing energy. The BBC story reported that during one experiment last month, 'the amount of energy released through the fusion reaction exceeded the amount of energy being absorbed by the fuel — the first time this had been achieved at any fusion facility in the world.' This prompted a rush of even more effusive headlines proclaiming the 'fusion breakthrough.' As no doubt NIF's press officers would have told reporters, the experiment in question certainly shows important progress, but it is not the breakthrough everyone is hoping for."

Comments

Blowing out of proportion

[Geoffrey.landis]

There's a good discussion by Jeff Hecht in the Laser Focus World blog: "Progress at NIF, but no 'breakthrough'"
http://www.laserfocusworld.com/articles/2013/10/progress-at-nif-but-no-breakthrough.html

The amount of energy generated by fusion is quoted as having exceeded the amount of energy absorbed by the fusion fuel [my italics].

The misleading part comes from the fact that the target absorbs only a small fraction of the energy in the laser pulse. The August experiments used a laser pulse of 1.7 million joules to generate 8000 joules of fusion energy (measured from neutron yield). So the fusion energy amounts to a few percent of the energy in the laser pulse (and much less if you account for the inefficiency of the laser).

Re:Blowing out of proportion

[TapeCutter]

That was actually a serious concern before we started blowing up Pacific islands for practice. It was thought that the bomb could trigger a chain reaction that fused all of the Nitrogen in the atmosphere in one very brief but spectacular flash of high energy radiation. Contrary to what some have claimed the boffins on the Manhattan project did not just cross their fingers and light the fuse, they rigorously demonstrated that it could not happen long before they had a working bomb. It's actually quite an interesting historical story and well worth a browsing in WP (ie: I can't be bothered looking it up and posting the links for you ;)

BBC reported correctly

[Anonymous Coward]

actually the BBC's story reports correctly -
"The BBC understands that during an experiment in late September, the amount of energy released through the fusion reaction exceeded the amount of energy being absorbed by the fuel - the first time this had been achieved at any fusion facility in the world.

This is a step short of the lab's stated goal of "ignition", where nuclear fusion generates as much energy as the lasers supply. This is because known "inefficiencies" in different parts of the system mean not all the energy supplied through the laser is delivered to the fuel."

Re:BBC reported correctly

[erice]

actually the BBC's story reports correctly -
"The BBC understands that during an experiment in late September, the amount of energy released through the fusion reaction exceeded the amount of energy being absorbed by the fuel - the first time this had been achieved at any fusion facility in the world.

Actually, no. It still isn't correct.

In 1995, scientists at Princeton’s TFTR achieved scientific break even, whereby their tokamak briefly produced as much energy as it consumed.

So, not only is it not the breakthrough we were looking for, at best it replicated a feat achieved with a different technology nearly 20 years ago.

Not there yet!

[FoolishBluntman]

The headline states, "the amount of energy released through the fusion reaction exceeded the amount of energy being absorbed by the fuel".

This is not enough, they must be able to capture that energy and use it to produce the next laser implosion of the fuel.
That will be a milestone.

Also, since this is using a Deuterium-Tritium Fuel it produces very high energy neutrons which will help destroy the reactor much faster than in conventional fission reactions.

Re:My worry

[Anonymous Coward]

Fusion doesn't work with chain reactions. You have to replicate and maintain temperatures and pressures thousands of times greater than that at the centre of the sun to get most of your reaction mass to fuse (there are actually far less fusion reactions in the sun as a proportion of its mass than most people seem to think). If you can't maintain these conditions, the fusion stops and the reactor shuts down. For inertial confinement fusion like the NIF one has to keep feeding hydrogen pellets and shooting the laser, and if one can extract enough energy from the fusion to power the laser and whatever else, one can just keep feeding hydrogen pellets to keep producing energy. Same deal with a tokamak design: high magnetic fields heat and compress a plasma of hydrogen so much that it achieves fusion, and presumably the energy produced from the fusion can be used to power the magnetic fields and whatever else. If you shut off the magnetic fields or stop providing a continuous source of usable hydrogen plasma, the fusion stops and the reactor shuts down. We only get nuclear fusion in the sun and other stars because the mass of the sun is so great that gravity produces the conditions necessary for fusion in its core.

Re:Boring, boring, boring

[Anonymous Coward]

We won't have actual, real, fusion producing actual, real, power in an actual, real, commercial power plant on the grid in the lifetime of anyone alive now.

Don't be so sure. There are scientists working on increasing the human lifetime.