In the south of France, ITER is nearing completion. When it is finally fully operational in 2035, the International Thermonuclear Experimental Reactor will be the largest device of its kind ever created and a flagship for fusion.
Inside a donut-shaped reaction chamber called a tokamak, two types of hydrogen called deuterium and tritium will be broken together as they merge into a rotating plasma hotter than the sun’s surface, releasing enough clean energy to power dozens thousands of homes – an unlimited source of electricity, built directly from science fiction.
Or at least that’s the plan. The problem – the white elephant in the room – is that while ITER is ready, there may not be enough fuel left to run.
Like many of the most well-known experimental fusion reactors, ITER relies on a steady supply of both deuterium and tritium for its experiments. Deuterium can be extracted from seawater, but tritium – a radioactive isotope of hydrogen – is incredibly rare.
Atmospheric levels peaked in the 1960s, before the ban on nuclear weapons testing, and there are recent estimates that there is less than 20 kg (44 pounds) of tritium on Earth today. And as ITER drags on, years behind schedule and billions over budget, our best sources of tritium for its fuel and other experimental fusion reactors are slowly disappearing.
Currently, the third used in fusion experiments such as ITER and the smaller JET tokamak in the UK comes from a very specific type of nuclear fission reactor called a heavy water reactor. But many of these reactors are nearing the end of their service life, and there are less than 30 to 20 worldwide in Canada, four in South Korea and two in Romania, each producing about 100 grams of tritium a year. (India has plans to build more, but is unlikely to make its tritium available to fusion researchers.)
But this is not a viable long-term solution – the whole point of fusion is to provide a cleaner and safer alternative to traditional fission energy. “It would be absurd to use dirty fission reactors to fuel ‘pure’ thermonuclear reactors,” said Ernesto Matsukato, a retired physicist who is a staunch critic of ITER and fusion in general, although he spends much of his time his working life in training tokamaks.
The second problem with tritium is that it breaks down quickly. It has a half-life of 12.3 years, which means that when ITER is ready to start deuterium-tritium operations (as it happens, about 12.3 years), half of the tritium available today will decompose to helium-3. . The problem will only get worse after the inclusion of ITER, when several more deuterium-tritium (DT) successors are planned.
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