# World's Largest Nuclear Fusion Reactor Promises Clean Energy, but the Challenges Are Huge  ## About - Author: Carl Smith - Title: World's Largest Nuclear Fusion Reactor Promises Clean Energy, but the Challenges Are Huge - Tags: #articles - URL: https://www.abc.net.au/news/science/2023-03-19/nuclear-fission-iter-experiment-france-construction/102050226 ## Highlights The fusion reaction they're planning to create at ITER is dependent on having two unusual forms of hydrogen called deuterium and tritium, which, along with a proton and electron, also contain one and two neutrons respectively. Deuterium is easy: It's abundant in seawater, Dr Wauters says. "It's tritium, the second part, which is a bit more complicated." It's rarely created naturally, and ITER estimates the total current global supply of stored tritium to be [roughly 20 kilograms](https://www.iter.org/mach/TritiumBreeding). But the team at ITER hopes to use the fusion reactor itself to create more tritium as a kind of by-product of the reaction. This is known as "tritium-breeding", and involves bombarding lithium on the inner wall of the tokamak with neutrons in the plasma to create more tritium. ---