How Does a Fusion Reactor Work?
In a fusion reactor, two light atomic nuclei pull together to produce a heavier nucleus, and release a large amount of energy.
This is done by heating the atoms to high temperatures and forming a plasma; the joining of the two nuclei and the release of energy. The leading designs for a fusion reactor follow two different paths: magnetic confinement and inertial confinement.
- Magnetic confinement is just that: it uses magnets to control a charged plasma, which will follow the magnetic field lines. Built in a shape like a donut, the magnetic field is curved in a closed loop to prevent the particles from coming into contact with the reactor, and losing energy. The most promising design is the tokamak. The largest experiment has been the Joint European Torus (JET) in the UK. Others have been TFTR at Princeton in the USA and its successor, ITER, a seven country consortium, currently under construction in France.
- Inertial confinement uses laser or ion beams focused on the surface of the target to control the plasma. The extreme heat produces the right conditions for plasma formation and combining of the nuclei. Experiments are being conducted at the United States National Ignition Facility (NIF) and the European Union High Power Laser Energy Research facility (HiPER).
Alternative Energy: Fusion Fuel
The most promising fuels for fusion power, at present, are Deuterium and Tritium (D-T), both isotopes of hydrogen. Deuterium (hydrogen-2) is naturally occurring in our oceans and readily available. Tritium (hydrogen-3) is found in negligible amounts in nature due to its half-life of only 12.32 years. The reaction products are helium and neutrons (kinetic energy). Tritium can be produced as a by-product from the lithium used in the reactor.
Why Haven’t We Seen More Fusion Reactors?
Many problems keep this technology at bay. Due to the extreme conditions needed to create the plasma that culminates in the energy-producing reaction, finding suitable interior materials is difficult next to impossible. JET has had its interior 4,500 carbon tiles replaced with hopefully more neutron resistant tiles of beryllium and tungsten. Also, creating the necessary gravitational forces for the reaction, magnetic confinement, requires a large amount of energy. The main problem is producing more energy then is used in the energy-production process. Shooting a beam (inertial confinement) is expensive, and the technology is also a problem; there is no model. And the biggest question: who will stand to benefit financially? With the rush to patent and protect, discoveries might not be shared, as in the past, when one scientific community creates a solution such as an interior of neutron resistant material.
Fusion Reactions and Plasma: Reader’s Question Answered
So, to answer our reader’s question: From galaxies to controlled fusion, our lack of understanding has fostered its own research in a difficult area of physics, today. Yes, sustained energy is needed to maintain the plasma. Is there a limit? Only continued research will tell.
Fifty years ago, fusion technology was 50 years away. It is still estimated to be at least that or more, but acquiring the golden egg of viable fusion energy production has always been the dream, and this technology is definitely going to be a part of our future.
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Perspectives on Plasmas. Basics- Overview. Plasma Science and Technology. Accessed July 27, 2012.
Plasma Properties. What is a Plasma? Accessed July 27, 2012