Since 1985, we have been waiting for Doc Brown's Mr. Fusion, first revealed in the Back to the Future Series. In the southern tip of France, just slightly northeast of Marseille, ITER (International Thermonuclear Experimental Reactor) is being built by China, European Union, India, Japan, Korea, Russia, and the United States. The concept is to build a tokamak that will produce 500 MW of fusion power from deuterium and tritium. It is hoped that the reactor will produce more power than it consumes, but it will not be coupled to electrical turbines. (The ITER website hopes for a 10:1 positive energy ratio.)
Unlike fission reactors which produce energy when a heavy atom splits into parts, a nuclear fusion reactor combines two lightweight atoms to produce a heavier atom. The latter has been elusive for scientists and engineers because it requires ludicrous amounts of energy to overcome the natural electrostatic repulsion of two atomic nuclei. Once the two nuclei are close enough, then the strong nuclear force which holds the protons together in the nucleus is stronger than the electrostatic force. Wiki tells that the initial energy barrier is 0.01 MeV. Almost instantaneously, the new nucleus releases 14.1 MeV. (A significant payoff, if we can ever achieve it.)
The original goal of ITER was to construct the facility in 10 years. The full activity of the ITER is delayed eight years explains that operation will start in 10 years, but it will be an additional eight years before fusion experiments begin.
Cost and complexity are explained as the need for stretching the schedule. Fusion falters under soaring costs describes ITER as the world's largest science experiment. They are constructing 130 separate buildings, with the largest building to house the tokamak - describes as large as the Arc de Triomphe in Paris. The BBC reports the cost of the facility is now greater than $16B - the original budget was $6B.
The article explains that scientists are still inventing the machine as it is being built. The tokamak requires temperatures ten times greater than the sun. The materials to build the containing box have not been invented yet. (Recall the tokamak must be hotter than the sun because the solar reaction exploits intense gravity to help overcome the Coulomb Barrier.)
So are we going to get there? Some scientists in the BBC article think it will be another 100 years. I don't know - we have been working this problem since the 1940s and still do not have an operating fusion reactor.
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