Our 2010 School Lecture presenter Dr Melanie Windridge on her lecture tour and fusion reaction.
My fusion tour around Scotland took me to Glasgow, Edinburgh, Aberdeen and Inverness on consecutive days, so I’ve had busy days of talking and travel. There wasn’t time to see much of the cities, but I did get to see lots of beautiful countryside in between and the weather wasn’t nearly so bad as forecast. We drove down past Loch Ness (I didn’t see Nessie) and past Ben Nevis and spent the weekend on the beautiful Isle of Mull, staying at Lip Na Cloiche – a lovely little B&B with an amazing garden and view over Loch Tuath. We went beachcombing for pretty and interesting objects and ate lots of seafood. On Monday we drove through the mist and rain to Tobermory, where I spoke at the school, and on Tuesday we reluctantly took the early ferry back to the mainland and headed back home.
In the last fusion blog we were talking about JET, the biggest tokamak in the world. This week I’m going to tell you a bit about ITER, the next-step fusion machine that is even bigger than JET and is currently being built in France.
ITER is a worldwide collaboration of seven major parties – China, the European Union, India, Japan, Korea, Russia and the USA. It is a huge project that aims to prove the technical feasibility of fusion by getting ten times as much energy out of the fusion reactions as is put in to start them. It will also operate in similar conditions to those in a future fusion power plant and will test important reactor technologies such as helium extraction, tritium breeding and remote maintenance.
ITER is a huge machine that is about twice as big as JET and with ten times the plasma volume. It will be over 30m tall and will weigh 23,000 tons, see Picture 1 (spot the man in the bottom right corner). The building to house it will stand 57m tall (that’s almost as tall as a twenty story building). 10,000 tons of magnets will control the plasma: 18 magnetic coils to create the toroidal field that traps the charged plasma particles; 6 coils to create the poloidal field that pulls the plasma away from the walls and can shape and move the plasma. Visit http://www.iter.org/mach for an interactive diagram of the ITER tokamak to find out more about the different components of ITER.
The ITER vacuum vessel and magnets will sit inside a huge coolbox – the cryostat – that will cool the superconducting magnets using helium at -269°C. Superconducting magnets are needed for long or continuous operation. An experimental plasma shot in JET lasts only about 30 seconds and is limited by the copper magnetic coils. As currents flow through the copper coils to make the magnetic field the coils heat up due to resistance. If JET ran for too long the coils could melt, and they must also cool down again before the next shot can start. Superconductors are materials that have zero electrical resistance and so don’t heat up, but the phenomenon of superconductivity only occurs in some materials below a certain, characteristic temperature near absolute zero.
Using superconductors for ITER means that the experimental shots will be able to run for much longer and that no energy will be wasted in the coils, so the power consumption will be next to nothing compared with JET’s copper coils. However, the design of ITER will have to be a lot more complicated because of the cooling system for the superconductors. Superconducting coils are also much more expensive. Picture 2 shows the ITER magnets.
ITER was originally designed as an even larger machine back in the late 1980s to early 90s, but by the end of that decade the Soviet Union had collapsed, research funding had dropped so much that the USA had pulled out of the project and the Japanese economy was struggling. The ITER project was delayed and scaled back to cut costs. In 2001 the newly-designed ITER was 75% of the size of the original design and budgeted at €5bn. Clearing of the site near Aix-en-Provence began in 2008 and construction has now started, but since 2001 commodity prices have increased, costs in the power market have escalated and the cost of ITER is now estimated to be €13bn.
ITER is a costly project, but it is also major technological feat. Succeeding in fusion relies on the collaboration of scientists from many disciplines, such as materials science, engineering and plasma physics. It requires the development of sophisticated systems – for example vacuum and cooling systems – and advanced materials to withstand high temperatures and lots of fast, energetic neutrons. Fusion research and tokamak development pushes the boundaries of technology and stimulates innovation. Culham Centre for Fusion Energy promotes this and helps start-up companies using spin-off technology in areas such as Magnetic Resonance Imaging, cheaper space travel by spaceplane and low-weight rechargeable batteries, to name just a few.
The roadmap to fusion sees the next-step fusion experiment, ITER, operating through the 2020s, demonstrating net power output and bringing together new technologies for reactor design. The 2030s should see a demonstration power plant (DEMO) produce electricity at the end of the decade, with commercial fusion plants to follow.
In the next blog we’ll be talking about robots being developed at JET – a technology essential to fusion reactor maintenance – and I’ll be visiting Yorkshire and Derbyshire.