Help, My Fusion Reactor’s Making A Weird Noise


This is the control room for JET, the Joint European Torus at Culham Centre for Fusion Energy. JET is a nuclear fusion experiment, a scientific research facility that's hopefully one step on the journey to plentiful, clean fusion power. When it's running, the reactor vessel is literally the hottest place in the solar system, ten times hotter than the core of the sun, and right now, we are just a couple of minutes away from an experiment — or as they call it here, a pulse. We're running a series of experiments at the moment looking at disruptions. Plasmas really don't want to be there. When they cease to be, they create quite a lot of mechanical energy which can shake the machine, and in future power plants we really want to try and mitigate against these problems. So right now, enormous, 700-tonne flywheels are being spun up to provide enough energy for the experiment.

Less than a hundredth of a gram of gas is already in a vacuum vessel next to the torus, and when the pulse starts, it'll be pushed in and heated: by enormous magnets, by injecting hydrogen atoms, and just by dumping huge amounts of radio frequency power into it, making it into a superheated plasma. And then it'll hit about a hundred million degrees Celsius, and we will start to see nuclear fusion. With fission, you're always trying to slow it down and control that reaction. And we have exactly the opposite thing. And therefore it's not possible to see a situation where you could have a large-scale accident as you could with fission. Now, there are huge numbers of machine protection systems watching the experiment. If anything goes wrong, power gets cut and the whole system just stops. But if something's more subtly wrong, there's one safety feature you might not expect. Up in the ceiling are surround-sound speakers, hooked up to microphones in the reactor hall, where no human is allowed.

Those speakers relay the sound from the experiment to the crew here in the control room in real time, as if they were standing — as if this point where I'm standing right here — was in the middle of the torus. And all the high-tech machine protection equipment here is necessary, every single bit of it. Computers can react so much faster than us: that human delay between incident and response could be the difference between a safe shutdown and some rather expensive repair bills. But if something is subtly wrong, like when you get a faint, weird noise in your car, humans might be able to notice before computers do. A couple of years ago, we had a disruption and we could hear this clanging noise. And we were able to pinpoint the exact area, and what we believed it was which was a clamp which held a pipe, and we were immediately able to walk into the area, go to where we believed it was, and found it — and then could replace it. The engineers here: they're taken a human ability — that feeling that's been honed by hundreds of millions of years of evolution, that something is just subtly wrong, something is off — and they've put it to work on one of the most incredible things that humanity has ever constructed.

All right. Here goes the pulse. [Five, four, three, two, one, zero…] [Translating these subtitles? Add your name here!].