Environment

By Maureen A S Griffin


New green energy for the future

New green energy for the future

Photo shows the interior of the NIF target chamber. The service module carrying technicians can be seen on the left. On the right is the target positioner, which works with the target alignment system to precisely locate a target with an accuracy of less than the thickness of a human hair. Photo credit: Lawrence Livermore National Laboratory.

 

The world’s largest laser is located at the Lawrence Livermore National Laboratory in Livermore, California, USA. Housed in the National Ignition Facility, or NIF, the NIF laser is actually made up of 192 laser beams which are focused onto a small target containing a mixture of deuterium and tritium. The goal of focusing all of this laser power is to convert the deuterium and tritium (DT) into Helium molecules through a fusion reaction.

The NIF laser was on schedule to demonstrate this reaction by the end of 2012, and a successful ignition reaction would be an important milestone on the way towards a new paradigm of power generation, known as the Laser Inertial Fusion Energy (LIFE) project.

Powerful and renewable

Currently in the theoretical stage, a LIFE power plant uses the energy of many laser beams focused on DT fuel targets, which are surrounded by a lithium-based coolant. After the fusion reaction occurs, the heat released is absorbed by the coolant, which is then cycled through a heat exchanger. The extracted heat can then be used to power a steam (or other hot gas) turbine and be converted into electrical power.

A fully operational LIFE power plant has the potential to produce energy gains of 25- to 35-fold, so a plant run by a 10-20 MW laser would produce 2000-5000 MW of thermal power. After the initial ignition, a LIFE power plant would therefore be able to produce enough energy to power itself in addition to supplying power to the electrical grid.

This astonishing energy gain is thanks to the conversion of a small amount of matter into energy according to Einstein’s famous equation E=mc 2. And as an added bonus, the free neutrons released by the fusion would react with the lithium in the coolant to create more tritium, which can be used to make more targets, thus creating a closed fuel system.

The hohlraum cylinder, just a few millimeters wide with laser beam entrance holes at either end, is about the size of a pencil eraser. It contains a fusion fuel capsule the size of a small pea.

Green and safety benefits

The benefits of a system of LIFE power plants are numerous. The by-product of the fusion reaction is helium gas, so fusion does not produce nuclear waste like traditional nuclear fission reactors do. In addition, the LIFE reactor does not generate heat when it is not operational, so there is no possibility of a “meltdown”, nor does the reactor need cooling in the event of a shutdown. And because the required amounts of tritium fuel are so small, an accidental spill would have no negative impact on the environment.

While a market system of LIFE power plants is still years away, the program is on track to demonstrate the first operational LIFE plant by the mid-2020s with a fleet of LIFE plants slated to begin supplying the electrical grid with power by the late 2020s.

This artist's rendering shows a NIF target pellet inside a hohlraum capsule with laser beams entering through the openings. The beams compress and heat the target to the necessary conditions for nuclear fusion to occur. Successful ignition will be the culmination of more than 30 years of inertial fusion research and development, opening the door to exploration of previously inaccessible physical regimes.
Photo credit: all photos provided by Lawrence Livermore National Laboratory. We also acknowledge the US Government's right to retain non-exclusive, royalty-free license in and to any copyright covering the photos used in this article.

References

  • Arnie Heller, Science & Technology Review, April/May 2009, “Safe and Sustainable Energy with LIFE”

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