Nuclear Fusion Redux: How Realistic Are Scientists' Plans to Build Mini-Stars on Earth?
Image via BBC
I know what you're thinking: This, again? Or: Why are scientists still wasting precious time and money futilely pursuing such pie-in-the-sky schemes? Having read my fair share of nuclear fusion hyperbole, I can certainly sympathize with the sentiment.
But, from the sounds of British physicist Brian Cox's assessment, it looks like this latest attempt at building a working commercial prototype within the next few years may actually happen. Joint European Torus (JET), a working nuclear fusion reactor that has been in development for the past three decades, may be too small to generate significant quantities of electricity, but a new, much larger commercial prototype, called ITER, being built in the south of France could do the trick.
According to the project website's description:
In ITER, scientists will study plasmas in conditions similar to those expected in a electricity-generating fusion power plant. It will generate 500 MW of fusion power for extended periods of time, ten times more than the energy input needed to keep the plasma at the right temperature. It will therefore be the first fusion experiment to produce net power. It will also test a number of key technologies, including the heating, control, diagnostic and remote maintenance that will be needed for a real fusion power station.
Image via Sandia National Laboratories
The American approach to nuclear fusion, known as inertial fusion, is being developed by the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNB) in Berkeley, California, and by the Z-Machine at the Sandia National Laboratories in Albuquerque, New Mexico. (For some more background, see Michael's post about the NIF.) Whereas JET/ITER operate much like conventional reactors, producing equable amounts of electricity by consuming fuel for days or weeks at a time, NIF/Z-Machine produce huge, but short-lived, bursts of energy:
NIF blasts tiny pellets of deuterium-tritium fuel with a single 500-trillion-Watt laser beam. This is a big number; about 1,000 times the power consumption of the United States.
This gargantuan sort-lived laser pulse causes the fuel pellet to collapse and detonate, producing a mini-star for a fraction of a second.
The Z-machine takes a different approach, channelling half a trillion Watts through a spider's web of hair-thin wires surrounding the fuel pellet. The result is much the same: a big crunch known as a Z-pinch and the birth of a star.
Cox explains that an inertial fusion reactor could be built if the instruments are able to produce a steady stream of these mini-stars. He points out that the Z-Machine has already successfully managed a test run and that the NIF plans on doing so by 2010.
"This is no mean feat, but there seems to be no fundamental reason to doubt that it is possible . . . In fact, the fusion engineers of 2009 are speaking of building the final generation of experimental reactors now," he assures us.
Even if everything goes according to plan, however, we won't see the first commercial reactors go online until 2030, at the earliest. As a long-term solution to our energy woes, nuclear fusion may eventually come into its own but, for the moment, we're better off sticking to more feasible clean energy technologies.