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Asked by sonya on 10 Dec 2021.
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Charlie Boswell answered on 29 Nov 2021: last edited 29 Nov 2021 12:58 pm
The most dangerous part of nuclear fusion is the fuel we use. It is a gas called Tritium, but it is dangerous because it is radioactive. That means that if we ever let it out, people might get sick. We also can’t go inside the machine because the insides get radioactive over time. So, we use robots to go inside and do any work we need to do.
We also use a really really really big laser beam to heat up the fuel sometimes. This is quite dangerous too, because if we miss the gas we might make a big hole in the side of our machine!
Apart from that, fusion is very safe. If we lose control of the star inside, it might bang quite hard against the side of the wall but after that it will get smaller and disappear. It is really hard to keep the star there, so without everything being just right it quickly goes away.
We’re really careful about not letting anything dangerous happen. We have lots of people working to make sure it doesn’t happen, and even more computers and robots stopping the humans from doing anything accidentally.
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Hermione Salter answered on 7 Dec 2021:
Like everything fusion has some risks, however we’ve puts lots of time and energy into making it as safe as possible. In reality we have so many safety systems and procedures that fusion is no more dangerous than any factory or power plant.
The fuel we use (Tritium) is radioactive and so we have to be careful with it, however we use such tiny amounts of it (less than the weight of a postage stamp in the reactor at one time) that it couldn’t cause a big disaster. Everywhere the fuel goes we keep it protected using things called layers of containment so even if it gets through one, the other layers still stop it getting out.
Unlike other types of nuclear, a fusion reactor is really hard to get going and needs completely perfect conditions to make the plasma for fusion to happen. Because of this we can’t have anything dangerous like a chain reaction happening because even a slight instability causes the plasma to shut itself off and return to a safe state!
Similarly the lasers I worked on (which we use to measure the plasma) have some really thorough safety systems to make sure they can’t harm people or break things. We use things called interlocks which prevent the laser from firing unless everything is in place and working perfectly. Inside the machine there is a thing called a beam dump that the laser fires into that safely absorbs all the energy 🙂
Sometimes the plasma behaves unexpectedly, we call this a disruption. During a disruption the plasma can hit the wall of the reactor. We have things called limiters which are like silver bananas on the inside of the walls, that have been designed to take these forces a bit like crash barriers. This means the plasma can’t damage anything important.
While the plasma is super hot, we have such a small amount of fuel that the total energy is not enough to cause much damage. Picture dropping a match into a bucket of cold water, even though the match was really hot when you started, it wont be enough to heat up the water. Similarly the tiny amounts of super hot plasma do not affect the temperature of the whole machine.
All of these things (and many more I’ve not mentioned) work together to make fusion a really safe process. Like everything it is impossible to get rid of all dangers so we just have to make sure we have safety systems in place and fusion has lots and lots of these! 🙂
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