Joint European Torus: towards nuclear fusion

We’ve heard of nuclear fission - splitting the atom in common parlance - but there is another form of nuclear power, one that boasts the potential of being almost limitless and is said to be safer and cleaner. That’s nuclear fusion. Rather that breaking atoms apart, fusion involves pushing smaller atoms together to make bigger ones. It’s the process that powers the Sun, so we know it works. The challenge is trying to recreate the conditions inside a star, that make fusion possible, here on Earth! One of the places where they’re trying to do this, with some success now, is JET - the Joint European Torus, at Culham. Evelyna Wang went to take a look around...

Fernanda - Fusion happens when two light elements fuse and release more energy than what they had before.

Evelyna - That was Fernanda Rimney, a plasma physicist and JET's senior exploitation manager. JET stands for Joint European Torus. The shape of the reactor is included in the name. JET is a torus, or a donut. This shape is essential for the research.

Fernanda - The way we confine this very hot plasma, the very hot fuel that we need to produce fusion, is by using magnetic fields. The plasma is made of ironized particles. They stick to the magnetic field.

Evelyna - The fuel, or plasma, needs to be extremely hot, over a hundred million degrees Celsius, if the atoms are to gain enough energy to fuse. However, it isn't so simple. As the plasma heats up, it wants to expand outwards - it wants to collide with other matter which, in turn, cools it back down. The solution is to trap it with big magnets, forcing it to spiral around the reactor. The researchers here at JET have had success. At the end of last year, the team set a new record for longest fusion ever recorded: five seconds. I was keen to get a closer look at JET, but the first stop on my tour was the control room.

Fernanda - The glow that you can see on the screens, there, that's plasma. We have cameras looking inside the vessel. The simple view that you get here is just to check that everything is alright.

Evelyna - Am I allowed to ask what experiments they're running now?

Fernanda - Now they're running the clean up experiments; so, fairly low power, very low temperature experiments. From tomorrow, we go back to running some of the higher temperature experiments. We will put in some additional heating in the plasma, and then we go on with those until the end of the week.

Evelyna - We still need to work out the optimal conditions for experimenting with plasma. As funny as it sounds, that was JET's original purpose. It was built to study plasma. These experiments will better inform the nuclear fusion reactors of the future to allow us, one day, hopefully, to smash the current record.

Fernanda - Most of the experiments are a scan of something. You have your basic plasma and then you slightly change the heating power, the density of the plasma slightly, the magnetic fields. You try to change one parameter at a time.

Evelyna - Everyone looks so busy!

Evelyna - From the control room, it was a quick walk to the next building where the fusion reactor actually was.

Fernanda - It's going to be very noisy.

Evelyna - Okay. Wow.

Fernanda - Behind those yellow doors (is where that's coming from). Because the machine is operating, these doors are closed and there is another shield, a secondary shield.

Evelyna - The assembly room was a huge warehouse bustling with people moving around large boxes. There was even a giant crane plonked in the centre. Because JET is constantly in use, I wasn't able to get my hands on the actual reactor, but I did get to see the next best thing.

Fernanda - You can see the mock-up, up there.

Evelyna - That's the replica?

Fernanda - It's not just a replica. JET is built in sections like an orange - it's built out of eight octants. When they built it, they built nine. They built an extra one as a test. It was, full size, and it's that one.

Evelyna - From where I was standing, the replica looked like a metal donut propped up by big metal scaffolding. Compared to the real reactor, the mock-up was missing all of the external wiring, thick tubing for cooling water, and giant magnets. But still, I went up the stairs and pressed my face against the window.

Fernanda - This is the size of JET.

Evelyna - It's about the size of four shipping containers arranged in a cube. On the inside, it was a big hollow donut. Metal plates lined the walls like scales. Curiously, inside the mock-up, there was a large boxy looking robot. Fernanda told me that maintenance inside the reactor is carried out by the remote handled robot named Mascot. The replica of the reactor is used to train operators in manoeuvring that robot. To get a sense of what she meant, we went into the remote handling room.

Fernanda - This is the remote handling control room.

Evelyna - This is so cool!

Fernanda - Yeah, this is one of the coolest things ever.

Evelyna - Inside, there are two handles in the middle of the room, and on the walls were several big TV screens.

Fernanda - Basically, there would be one person controlling it from here.

Evelyna - So, they just stand right there and use the handles?

Fernanda - They use the handle, and the manipulator, and the mascot gets into the torus, and does whatever is needed from taking tiles of unscrewing things and then putting things on again. The mascot has got cameras, so there is a full view of what the person is doing. It is not an accident that the people who designed JET were all people with dual physics and engineering backgrounds. It was really at the core of the design and of the exploitation ever since.

Evelyna - The lessons and experiments done at JET inform the design of ITER or International Thermonuclear Experimental Reactor, a new fusion reactor being built in France that is twice as big.