Last Monday we took a trip to the MIT Alcator C-Mod tokamak, where the MIT scientists and students are trying to make nuclear fusion as a source of energy a reality.
The Alcator itself is an impressive machine, and one question I had to ask was what would happen if there was an all out, complete and utter failure of the equipment. Mostly I was curious if there would be a huge mushroom cloud over Cambridge. I was informed, however, that the worst that would happen would be that the machine itself would be destroyed with no ill effects on the surrounding area. This was somewhat surprising because the phrase “nuclear energy” in the wake of Chernobyl tends to invoke fear, but as our visit showed the Alcator is a far different beast.
The basic idea of a nuclear fusion reactor is to mimic the process that naturally occurs in the sun. One way or another all of the energy on our planet comes from the sun, either directly from the sun’s radiation and harvested using solar cells or in more roundabout ways such as through wind power. Even the oil and gas we use is the sun’s energy several steps removed, and oil in particular is the fossilized remains of living creatures that consumed plants that got their energy from the sun.
The fusion reactor works by heating gas to the point that it becomes ionized and turns into plasma, a fourth state of matter. Because plasma is so hot the particles within it are moving extremely fast and contain an incredible amount of energy, and this is why it is so powerful. Plasma makes up 99% of the visible universe, including nebulas and the interior of the sun. While plasma is common in our everyday lives -TVs and electric lights, just to name two – in order to create plasma that can be used to generate power the reactor’s inside rises to millions of degrees, to the point that it no longer matters whether you’re measuring the temperature in Celsius or Fahrenheit, it’s just really really hot. Our guide summed up the tokamak by calling it “the world’s most complex teakettle.”
The amount of energy that can be produced by a fusion reactor is millions of times the number that fossil fuels can produce, and unlike nuclear fission reactors the waste produced by fusion reactors is on par with the medical waste that we commonly deal with and can dispose of safely. Additionally, the fuel source for fusion reactors, hydrogen and deuterium, are incredibly common on Earth, so there is no danger of running out of them any time in the next billion years or so.
The one catch when it comes to using fusion to produce energy is that it doesn’t work – yet. It has come a long way from when it was invented over 50 years ago, but even the highly advanced Alcator is only used in two second bursts and is not yet hooked up to the grid. There is an international team being assembled to work on the International Thermonuclear Experimental Reactor, or ITER, which will the most advanced machine of its kind when it is finished in the next decade or so. So while fusion energy is not yet here it is being worked on, and when and if they finally succeed it has the potential to solve almost all of the world’s energy problems for the next billion years or so.