Part 1 of 3 Parts
In the south of France, the International Thermonuclear Experimental Reactor (ITER) is slowly moving towards completion. It is scheduled to be switched on in 2035. It will be the biggest fusion reactor ever constructed.
The ITER is based on the tokamak design which uses magnetic fields to compress and heat plasma in a donut shaped reaction chamber. The fuel for the popular tokamak design consists of two isotopes of hydrogen. Deuterium has a neutron in addition to a proton in its nucleus. Tritium has two neutrons in addition to the proton in its nucleus and is radioactive. When the isotopes in the fuel fuse in a turbulent plasma hotter than the surface of the sun, a huge amount of clean energy is released which is then converted to electricity. That is the plan but there is a big problem. By the time that ITER is switched on, there may not be enough fuel to operate it.
Like most of the most prominent experimental nuclear fusion reactors, ITER needs a steady supply of both deuterium and tritium. Deuterium is present in seawater at about one percent, so it is easily available. On the other hand, tritium is very rare. Atmospheric levels of tritium peaked in the 1960s before the international ban on atmospheric testing of nuclear weapons was implemented. According to the latest estimates, there are less than forty four pounds of tritium on Earth right now. As the construction of ITER drags on, years behind schedule and billions of dollars over budget, the best sources of tritium needed to fuel it and other experimental fusion reactors are slowly disappearing.
Currently, the tritium used in fusion experiments comes from a very specific type of nuclear fusion reactor known as a heavy-water moderated reactor. Unfortunately, many of these reactors are nearing the end of their working life. There are currently twenty such reactors in Canada, four in South Korea and two in Romania. Each of these reactors is producing about one hundred grams of tritium per year. (India has plans to construct more of these reactors but it is doubtful that India will make any tritium they produce available for fusion experiments in other countries.
This is not a viable long-term solution. The whole point of nuclear fusion is to provide a cleaner and safer alternative to conventional nuclear fission power. Ernesto Mazzucato is a retired physicist who has been an outspoken critic of ITER, and nuclear fusion more generally. He said, “It would be an absurdity to use dirty fission reactors to fuel ‘clean’ fusion reactors.”
A second major problem with tritium supplies is that it decays quickly. It has a half-life of about twelve years. This means that when ITER is ready to operate, in about twelve years, half of the tritium that exists today will have decayed into helium-3. This problem will only get worse after ITER begins operating because several more deuterium-tritium (D-T) fusion reactors are planned and they will need tritium.
Please read Part 2 next