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While fusion sounds simple, the heating, compressing and confining hydrogen plasmas at 100 million degrees is a significant challenge. It has taken a lot of science and engineering research to get fusion developments to where they are today. Following the first fusion experiments in the 1930s, fusion physics laboratories were established around the world. By the mid-1950s “fusion machines” were operating in the Soviet Union, the United Kingdom, the United States, France, Germany and Japan.
A major breakthrough occurred in 1968 in the Soviet Union, where researchers approached fusion conditions in a doughnut-shaped magnetic confinement device called a tokamak. From this time on, the tokamak was to become the dominant concept in fusion research, and tokamak devices multiplied across the globe (JET, TFTR, JT-60). Achievements in those machines led fusion science to an exciting threshold: the long sought-after energy “breakeven” point. Breakeven describes the moment when plasmas in a fusion device release at least as much energy as is required to produce them. Plasma energy breakeven has never been achieved, but scientists expect that the next-step tokamak device—ITER, currently under construction in France—will produce more power than it consumes, beginning to write the chapter on 21st century fusion.
An alternative type of magnetic confinement device is the so-called stellarator, which has the shape of a twisted doughnut. The world’s largest stellarator, called Wendelstein 7-X (or W7-X) is under construction in Greifswald, Germany by the Max Planck Institute for Plasma Physics. It is expected to start operating in 2015, after 20 years of planning and construction.
In parallel to magnetic fusion research, the international community is also exploring the feasibility of inertial confinement fusion as a viable energy source, where energetic beams such as lasers, are used to confine and heat the plasma to fusion conditions. This effort is being led by the experimental facility NIF, currently under operation in California, USA. Although energy breakeven has not yet been achieved in the NIF, scientific and technological progress since start of operations in 2010 has been substantial, and ongoing experiments are expected to demonstrate a feasible path towards commercial fusion in the near term.
DID YOU KNOW?
In September 2013, scientists at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory achieved the first step towards harnessing the power of the sun here on earth – they got more energy out of a fuel burn than was put into it. The achievement falls short of the NIF’s stated definition of “ignition”, which requires that the fuel burn release more energy than all of the energy used by the machine. To be clear, at this point they achieved a release of energy greater than that which the laser beams put into the fuel capsule.
The primary goal of the fusion program worldwide is the production of a commercially viable fusion power plant which would provide cheap, efficient, and clean power for the entire world. Fusion can also:
If scientists are successful in achieving a sustained fusion reactions, we will have an economical energy source that will change the world. Fusion fuel comes from water, and hence widely available and easily harvested at low cost. One out of every 6,500 atoms of hydrogen in ordinary water is deuterium, giving a gallon of water the energy content of 300 gallons of gasoline.
Fusion Reactor History
Massachusetts Institute of Technology
1991- Alcator C
1976 – PDX: Poloidal Divertor Experiment
1982-1997 TFTR: Tokamak Fusion Test Reactor
TFTR was the first in the world to use 50/50 mixtures of deuterium-tritium, yielding an unprecedented 10.7 million watts of fusion power.
In 2010 JT-60 was disassembled and is currently under construction to be upgraded to JT-60SA by using niobium-titanium superconducting coils.
The largest tokamak in the world, it is the only operational fusion experiment capable of producing fusion energy.
The NIF and ITER Projects
Center for Nuclear Science and Technology Information of the American Nuclear Society
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