Nuclear fusion is considered a potential energy source of the future. It's clean nuclear energy. But what is it, exactly and why is it so difficult to generate? Let's start with the difference between classical nuclear fission and nuclear fusion.
Nuclear fission means that radioactive isotopes, like uranium or plutonium are being split up and turned into other highly radioactive isotopes that then have to be deposited or reprocessed.
Nuclear fusion means that two isotopes of hydrogen - called deuterium and tritium - merge together - they "fuse." And that leaves behind only non-poisonous helium and one single neutron, but no nuclear waste.
Nuclear fusion takes place in the sun for example - or in a hydrogen bomb - and that's the big challenge for engineers - how do you control the high energy fusion process in a power plant?
That's what scientists have been working on since the 1960s. One model-fusion-reactor called Wendelstein 7-X has just started operating in the northern German town of Greifswald. It is not designed to generate a nuclear fusion reaction yet - so far it's just a specific reactor design that's being tested.
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