Dr. Hans Bethe (1906-2005)

Ever since Hans Bethe in 1939 explained how the fusion of hydrogen atoms into helium generates the energy in the stars,  mankind has dreamed of replicating that process on Earth to provide us with an endless supply of energy.

Now, after 70 years of intensive research and trial and error, humanity is in the process of building an experimental fusion nuclear reactor in the south of France to see if that dream can come true.

The purpose of ITER (the International Thermonuclear Experimental Reactor) is to determine if it will be possible to build full-scale electricity-producing fusion power plants by the end of the 21st century.  After years on the drawing board construction commenced on the site at Cadarache, France in November, 2010 with plans to have the facility ready for operation by the end of this decade. The plant would remain in operation until about 2035 although it could be extended for another decade.

 

Cadarache, France (ITER site)

The fusion reactor itself has been designed to produce 500 MW of output power for 50 MW of input power, or ten times the amount of energy put in.   The machine is expected to demonstrate the principle of getting more energy out of the fusion process than is used to initiate it, something that has not been achieved with previous fusion reactors.

If successful, there are plans to build DEMO around mid-century, the first commercial demonstration fusion power plant based on ITER’s research.

ITER is an international project funded by the world’s largest energy users: the European Union, Japan, India, China, Russia, the United States, South Korea and India.  It is also likely to be the most expensive scientific experiment in history and cost overruns have been an ongoing theme.  The projected cost is anywhere from  $13 to $21 billion. The current economic crisis has not helped with the on-going funding and many meetings have been held among the countries to sort this out.

ITER is based on the tokamak concept of magnetic confinement, in which a very hot plasma is contained in a doughnut-shaped vacuum vessel. The fuel—a mixture of Deuterium and Tritium, two isotopes of Hydrogen—is heated to temperatures in excess of 150 million°C, forming a hot plasma. Strong magnetic fields are used to keep the plasma away from the walls; these are produced by superconducting coils surrounding the vessel, and by an electrical current driven through the plasma.

The reason the temperature has to be so high has to do with the difference between the intensity of gravitation on Earth and on the Sun.  The pressure is so great on the Sun that hydrogen fuses into helium at 15 million °C; on Earth, with much lower gravity, we need energies 10 times that amount.  At these very high temperatures very little radioactive waste is produced, unlike today’s fission reactors.  Instead, the process produces a very large output of energy.

Scientists theorize that a fully functional fusion reactor would provide cheaper, safer, cleaner and endless energy and reduce the world’s dependence on fossil fuels.

Despite being technically non-renewable, fusion power has many of the benefits of renewable energy sources (such as being a long-term energy supply and emitting no greenhouse gases as well as some of the benefits of the resource-limited energy sources as hydrocarbons and nuclear fission.  Like these currently dominant energy sources, fusion could provide very high power-generation density and uninterrupted power delivery (due to the fact that it is not dependent on the weather or time of day, unlike wind and solar power).

 

 

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