Star power: the Irish role in a French nuclear reactor

Irish scientists on the Iter nuclear fusion project in Provence are helping to build the world’s most complex machine

An aerial shot of the Iter site this year

An aerial shot of the Iter site this year

Thu, Jul 25, 2013, 10:26

The world’s most complex machine is being built on a hilltop in the south of France. It aims to recreate the power of stars through nuclear fusion (not fission) and promises boundless energy with no greenhouse gases. Irish scientists and engineers are key players in this ambitious project, helping to develop the reactor in the Provence countryside.

The reactor, dubbed Iter (International Thermonuclear Experimental Reactor), will heat a dense soup of gas particles to 150 million degrees. Hydrogen nuclei will then bang together and fuse, releasing nuclear energy. It poses none of the risks of regular nuclear power, the scientists promise, but critics deride the machine as a colossal waste of money.

We know fusion works because it powers the sun, where hydrogens combine due to gravity and high temperature to produce helium and the energy released we’ve enjoyed this summer. Here on Earth, scientists will hold searing hot plasma in place using giant superconducting magnets, which will keep it away from the walls of its vacuum chamber.

“When you heat gas up sufficiently, it becomes ionised, so you end up with free electrons and positively charged ions,” says Miles Turner, director of the National Centre for Plasma Science and Technology in DCU. “So you get nuclear chemistry rather than your ordinary electron chemistry.”

Releasing the power of an atomic nucleus means more energy. In fact, it will release almost a million times more binding energy than burning coal, which just moves electrons around. Just a single gram of two types of hydrogen nuclei will generate the same energy as 8,000 litres of oil.

‘A soup of particles’
One way the plasma is fizzed up is by sending a beam through the magnetic field.

Irish scientist Deirdre Boilson heads up this effort in Iter. “Plasma is like a big soup of particles. When my beam goes in there it inevitably collides with these other particles and so gives energy to them,” the Castlebar native says. Boilson first got involved in fusion science in DCU, before she moved to sunny Aix-en-Provence to work on the Iter project.

Temperature for a scientist such as Boilson is a measure not of heat but of the average speed of particles. As a room warms, atoms and molecules increase their velocity.

Smashing two types of hydrogen – deuterium and tritium – produces high- energy neutron particles. It is difficult even to test materials’ ability to withstand these particles because they are not present naturally and cannot easily be produced.

Brian Macklin, a graduate of NUI Galway, is responsible for installation of the vacuum vessel, the heart of the reactor. A special route has been developed - with roads upgraded and widened – to allow the colossal parts be convoyed in from a port close to Marseille.

The size and weight of components and the fact that they have to be aligned so precisely poses a major engineering challenge, says Macklin.

“There are 17m-high components weighing, say, 400 tons that require alignment precision of two to three millimetres. Just parking your car to two to three millimetres’ precision would be a challenge for most people,” he says.

The machine comprises about a million parts. These will be made all around the world and shipped to the French site for assembly, which will involve about 4,000 construction workers.

The eyes and ears of Iter
Once the plasma is burning, getting the energy out without damaging the reactor’s steel walls is one of the really big problems yet to be solved, explains Turner. “It is about making sure the power flux is as equally distributed over the walls of the reactor as possible.”

And here again another Irish scientist is at work on a critical issue. Michael Walsh from Cork is head of Iter diagnostics, “the eyes and ears of Iter”, as he explains.

Visible light and infrared-sensitive cameras will monitor the walls of the device and colour changes in lasers will be analysed for temperature, he says. Monitoring devices are essential to get the plasma large enough, without touching the walls, and at the right temperature. As radioactive tritium is used in the reactor, people will not be able to enter.

The Iter club counts Japan, South Korea, India, China, Russia, the US and the European Union as members. It courted controversy within Europe when costs escalated recently to about €15 billion in total.

“The cost is not cheap,” says Walsh, “but the actual amount of money is very small compared to the amounts countries spend every year on energy.”

Technology spin-offs
There are also expected technology spin-offs from Iter, and DCU is already benefiting from its fusion know-how. Low-temperature plasma gas – low here means 20,000 degrees or so – can etch transistors on to silicon wafers, a technology Intel uses, Turner says. Intel in future will likely need precise plasma measurements in their fab plants, he adds, and his plasma centre is contributing to this research.

Fusion fans acknowledge a fusion energy plant is a long-distance endeavour, akin to a Mars expedition, perhaps. The first plasma will be generated in 2020 and fusion is planned for about 2030.

This is an experiment, and multiple fusion power plants will certainly not be built before 2050.

“The promise of fusion is large-scale energy supply without the problems of long-term radioactive waste management associated with traditional nuclear power,” says Turner. “In that context this has high relevance to Ireland.”

Fusion energy: The future or folly?
Nuclear energy’s stock has fallen after the Fukushima disaster in Japan. However, instead of splitting uranium or plutonium, as in conventional nuclear fission (splitting the atom), a fusion reactor joins two hydrogen nuclei together as they whizz through a vacuum chamber. Is it safe?

“I don’t think anybody can think of a catastrophic accident scenario involving a fusion reactor,” says physicist Miles Turner of DCU. “Fission reactions can get out of control, but there doesn’t seem to be any risk of this with fusion. Rather the opposite is the case: we might not get it going.”

Iter’s plasma would store the energy equivalent of about 700 kettles of boiling water. Once fusion begins it will be self-sustaining, but cannot run out of control, say scientists. If the plasma cools, fusion stops.

Fusion research has gone on since the 1940s and critics say it is as unachievable as ever, but Iter scientists insist fusion is doable. Unfortunately it will be some time before we see if this is the energy of the future or grand folly.