Utility Week

Utility of the Future: climate change 10 | 20TH - 26TH SEPTEMBER 2019 | UTILITY WEEK Nuclear fusion In search of limitless cheap electricity Nuclear fusion is seeing a surge of activity and investment. Greg Jones visited the UK's Culham Science Centre and spoke to a start-up to find out whether energy's Holy Grail is within grasp. S ince the concept was first envisaged in the 1930s, the dream of generating elec- tricity through nuclear fusion has been one of boundless energy from effectively lim- itless fuel. Despite its potential, and plenty of research, we still have not reached the desti- nation. In fact, it has become something of a joke in the industry that fusion is always "30 years away". So where are we now? As the technology continues its long development, the fusion start-up scene is seeing increased interest. Co-ordinated government-funded research efforts con- tinue to strive to deliver what is the ultimate green energy prize. Alongside this, private investors have emerged in recent years as companies across the world explore more experimental methods promising faster results than the conservative estimates of government-backed initiatives. The biggest player in the UK is the Cul- ham Centre for Fusion Energy (CCFE) in Abingdon, Oxfordshire, located on the site of a former Royal Navy Air Station. The CCFE hosts both Britain and Europe's foremost fusion research programmes and the com- plex is situated on a wide, flat field, where 75 years ago hangars housed Supermarine Seaf- ires and Hawker Sea Furies. Today, the buzz of propeller planes has been replaced by more terrestrial engines. Within the buildings, however, operations are far from mundane. CCFE houses two tokamak (see box, p14) fusion reactors, the Joint European Torus (JET) and the Mega Ampere Spheri- cal Tokamak (MAST). The goal is to clear the way for cheap, clean energy production at a scale we have yet to see on Earth. Making the science stack up At the Culham Centre for Fusion Energy, the fusion reactors use fuel composed of an equal mixture of deuterium and tritium, two isotopes of hydrogen. This is because the fusion reaction between these two requires the least energy and is easiest to initiate. Deuterium and tritium have one and two neutrons respectively in their nuclei, in contrast to the zero found in hydrogen. Under the right conditions, they join to form helium, a single neutron, and with it the release of energy. The issue is that, despite this being the easi- est reaction to make happen, attempts up till now consume more energy than is released. The process needs to become much more efficient before viable generation is a reality. One of the main problems with fusion reac- tors thus far is maintaining plasma stability for extended periods. Plasma is a superheated gas that becomes a cloud of ions and free electrons, and is the environment necessary for fusion to occur. Crucially the plasma can only be held stably in a vacuum, suspended by a powerful magnetic field, as it cannot come into contact with the materials of the reactor. JET's magnets are made with copper coils, which start to overheat due to the huge amount of electricity required to operate them. Pres- ently, you get "about a minute", and a‡er that "you literally can't run the machine longer than that, otherwise there's no machine", says Colin Walters, the director of National Fusion Technol- ogy Platform. At the moment, JET can only produce plasma pulses lasting seconds. Looking toward ITER, one if its main purposes is to achieve longer pulses that run for minutes at a time, "to a point where you can get reliable quantities of heat, Nuclear fusion is the means by which our Sun produces the heat and light that sus- tains us, reaching 15 million degrees Celsius at its core. Here, hydrogen atoms are fused to form helium. This reaction is exothermic, meaning it has a net positive energy release, which results in the radiation the sun emits. This energy release is the basis for fusion generation. Theoretically, a controlled fusion reaction would be able to produce energy far more efficiently than fission reaction or the burning of fossil fuels, with the added ben- efits of a plentiful fuel supply and markedly less environmental and safety concerns. As it stands, it requires more energy to continued overleaf

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