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Sandia simulation suggests sunny skies for fusion reactors

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April 2, 2012

Sandia's Z-Accelerator in action (Photo: Sandia National Laboratories)

Sandia's Z-Accelerator in action (Photo: Sandia National Laboratories)

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In the beginning, there was the thermonuclear bomb - mankind had harnessed the energy of the Sun. Confident predictions abounded that fusion reactors would be providing power "too cheap to meter" within ten years. Sixty years later many observers are beginning to wonder if billions of dollars of effort has been lost in digging out dry wells. Now a new simulation study carried out at Sandia National Laboratories in Albuquerque, New Mexico, suggests that magnetized inertial fusion (MIF) experiments could be retrofitted to existing pulsed-power facilities to obtain fusion break-even.

Fusion power results from combining the nuclei of light atoms to make heavier ones, while in the process releasing ~1% of their mass-energy. Research on controlled fusion power has focused primarily on two paths - magnetic confinement fusion and inertial confinement fusion.

In magnetic confinement fusion, a very low density plasma is held at perhaps 200 million degrees K for about a second. In inertial confinement fusion, an enormously dense (~ 100 times the density of solid lead) is enormous, and rapid compression to that density produces a hot plasma, but the confinement time is only about a nanosecond.

Neither approach has demonstrated break-even performance - where the fusion power released is greater than the energy required to establish and maintain the fusing plasma.

Magnetized Inertial Fusion

The magnetized inertial fusion method works like this. A sample of mixed deuterium-tritium gas is placed in a small conducting cylindrical target. The target is placed in an extremely strong axial magnetic field (typically tens of Tesla in intensity). A pulsed laser is used to heat the sample gas, following which the cylinder is subjected to rapid radial compression, either by an imploding laser pulse or by an extremely strong current. Fusion follows.

Among the benefits of this approach to fusion power are that the axial magnetic field makes the collapsing cylinder resist linear instabilities, so the compression is quite uniform across the sample. During compression, the axial magnetic field becomes tangled near the ends of the cylinder, which serves to further trap the sample and prevent an otherwise large axial loss of heat.

Sandia National Laboratories' Z-accelerator (Z for short) is an ideal platform upon which to test out magnetized inertial fusion. Designed as an intense X-ray source for testing nuclear weapon components, Z can deliver an electrical pulse with a sizable fraction of a petawatt of power for a duration of a tenth of a microsecond to a region about the size of your little finger. The axial magnetic field for the MIF experiment is supplied by a pair of coils energized just prior to the experiment by a 2.2 megajoule capacitor bank, supplying a field of about 10 Tesla. After heating the sample gas with an external laser pulse, the Z is discharged across the cylinder.

Such tests are currently being prepared. Sandia's simulation of the soon-to-be-carried out tests were intended to discover if the likely enhancement of fusion reaction rate was likely to be a small effect or a large effect (previous analysis had suggested a small effect was more likely). To their surprise, they found that in a situation where the cylinder was compressed by 60 mega-amperes of current, the process yielded about 100 times break-even performance. Increasing the current to 70 mega-amperes produced 1000 times break-even - a level at which the ratio between power taken from the power grid to run the apparatus would be less than the power returned to the power grid - in excess of true break-even performance.

Sandia researchers are preparing experimental tests of the MIF technique. They will begin at smaller compression currents, as the Z can only deliver 26 mega-amperes with which to compress the cylinder. However, we continue to hope for encouraging results ahead.

Source: Sandia National Laboratories

About the Author
Brian Dodson From an early age Brian wanted to become a scientist. He did, earning a Ph.D. in physics and embarking on an R&D career which has recently broken the 40th anniversary. What he didn't expect was that along the way he would become a patent agent, a rocket scientist, a gourmet cook, a biotech entrepreneur, an opera tenor and a science writer.   All articles by Brian Dodson
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12 Comments

This simulation result is good news. Now if just some indication can be found in the experiment.

This method is likely to benefit by the soon to be announced Ignition event at Livermore for Laser Inertial Confinement Fusion at the NIF facility.

It would be great if both methods for inertial confinement ended up delivering real energy for the planet.

Only Laser however at this time has the potential to deliver a real world Mr. Fusion i.e. a compact and light BH (boron hydrogen) near zero radiation fusion machine that could power your ultimate vehicle, home, plane or boat or even space cruiser.

attoman
2nd April, 2012 @ 10:18 am PDT

Hit that tritium with everything we've got, all at once! Hit it again with even more. Repeat ad infinitum. Eventually it has to light up.

ralph.dratman
2nd April, 2012 @ 10:53 am PDT

Gung ho! It would be really cool to have fusion power at last, lifting civilization out of these dark hard times of poverty, cruelty, humiliation, and fatigue. Virtually free electricity would move us forward into our galactic future. Congratulations Sandia Labs for your cool simulation. Now get to it!

Facebook User
2nd April, 2012 @ 11:21 am PDT

Take that, eco-greenies. Next time before you embarass yourself with absurd feelgood alternative energy boondoggles like wind, take a science class and find out what the adults are up to.

Todd Dunning
2nd April, 2012 @ 12:04 pm PDT

"Neither approach has demonstrated break-even performance - where the fusion power released is greater than the energy required to establish and maintain the fusing plasma."

Break even means the power output from the fusion reaction of the fuel is equal to the energy input required to make it fuse.

A fusion reactor running at break even is still useless. It must do much better than break even. The cost and energy it takes to produce the reactor fuel also must be considered.

Thermal depolymerization is an example of a technology where the energy obtainable from the fuel produced by it is greater than the energy required to manufacture the fuel.

Same goes for gasoline. There's more energy in a gallon of gasoline than it takes to drill for the oil, pump and transport the oil and refine the gasoline out of it. Plus there's all the other useful stuff that can be made from the oil.

For Ethanol, it's a far less efficient process to make it from grain or corn. If farms of genetically altered, alcohol producing algae ever get going, that will change because most of the energy required will be "free" from sunlight. The caveat there is the process is only workable in locations that rarely have cloudy skies.

What I find funny is all the depictions of fusion reactors in SciFi having massive explosions when they fail, or are "self destructed" when the real things are so difficult to keep going. The first thing a fusion reactor does when anything goes wrong is *stop fusing*. Any fusion powered starship would have an exhaust path (nice and twisty to avoid Death Star style destruction) where the plasma would vent in the event of containment failure. Making a fusion reactor *boom* proof is simply a matter of redundancy and (in cases where directed violence is expected) as wide of separation as possible for the redundant systems.

How about a SciFi story where a fusion reactor "unstart" is mostly an annoyance or in battle leaves the ship on a ballistic trajectory, unable to maneuver (except for possibly being able to rotates on its axes) and thus vulnerable to enemy fire.

Gregg Eshelman
2nd April, 2012 @ 01:31 pm PDT

Great tech! But - that is overkill to boil a kettle. Am I missing something? It still boils water to generate steam to drive a turbine? Wouldn't it be smarter to have thermal voltaic cells - they are at 4% efficiency at the moment but hey are not getting the funding like fusion.

RaVOLT
2nd April, 2012 @ 04:09 pm PDT

Although I really like the idea of Fusion Power, I often wonder if "breakthroughs" occur when it looks like people start to question the value of the investment. I also wonder what could have been accomplished with the same nationa investment in geothermal power. Clean, consistent, baseline geothermal power. When it comes to energy, often the least practical solutions garner undue funding and enthusiasm. Microwave beaming power down from orbiting solar stations and the like. Geothermal to varying degrees of drilling costs is the very definition of ubiquitous, endless power. Yet, many consider it Alternative Energy's ugly kid sister. Not saying fusion won't work or it's not worth it, just saying there may be a far more practical paths to the Electric Economy.

Burnerjack
2nd April, 2012 @ 05:36 pm PDT

about time :)

Andrew Kubicki
2nd April, 2012 @ 08:32 pm PDT

re; RaVOLT

Sure if you only use power during daylight.

While they are chasing the very nice dream of fusion power, let us build some nuclear power plants to give electricity to this generation.

Slowburn
2nd April, 2012 @ 09:59 pm PDT

re; Gregg Eshelman

Loss of containment promises to be darn spectacular.

Slowburn
3rd April, 2012 @ 05:16 pm PDT

Ahh, fusion power. So alluring and yet you are so far away. For 60 years and counting. I'll be waiting for that day.

Fretting Freddy the Ferret pressing the Fret
4th April, 2012 @ 02:11 pm PDT

"A new simulation", we are well aware of how financially lucrative a well massaged simulation can be to scientists and non scientists ala Al Gore and company. I'll stay dubious and shocked by the costs till REPEATABLE lab results are seen.

Michael Gene
7th August, 2012 @ 07:46 pm PDT
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