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But while progress on fusion is inching slowly forwards, there's one big problem: the fuel supply. One of the main fuels for fusion reactors is expected to be tritium, a rare version of hydrogen that's already in short supply.
But researchers at Los Alamos National Laboratory in the US have been exploring ways to use nuclear waste from existing fission reactors to make tritium for future fusion reactors. “Right now, the value of commercial tritium is about $15 million per pound [$33 million per kilogram], and the U.S. doesn’t have any domestic capability to create it,” says Terence Tarnowsky, a Los Alamos physicist who has been leading the work, which is being presented at a meeting of the American Chemical Society this week. “So, we have this tritium supply shortage.”
Tritium occurs naturally in the upper atmosphere. And the current major commercial source is fission reactors in Canada. “The total tritium inventory on the planet is about 55 plus or minus 31 pounds [25 plus or minus 14 kilograms],” says Tarnowsky. “Making some assumptions, 55 pounds [25 kilograms] is enough tritium to power more than 500,000 homes for six months. This is more than the residential units in Washington, D.C.”
Tarnowsky ran computer simulations to assess the feasibility of using nuclear waste to generate tritium. His design uses a particle accelerator to jump-start a reaction in the nuclear waste, causing atoms to divide and eventually become tritium. Although the basic principles of the design are not new, advances in technology could make it more efficient than when it was first considered in the 1990s and early 2000s, says Tarnowsky.
He estimates that this theoretical system running on 1 gigawatt of energy, or the total annual energy needs of 800,000 homes in the US, could produce about 2 kilograms of tritium per year. A key advantage to Tarnowsky’s system would be the efficiency of tritium production. He projects that the design would produce more than 10 times as much tritium as a fusion reactor at the same thermal power.
In future work, Tarnowsky will work out the dollar cost for tritium production, and evaluate the efficiency and safety of the hypothetical reactor design.
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