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Nuclear Fusion

First published with A Safer Nuclear Path? in Cleantech magazine 2011 Issue 3. Copyright Cleantech Investor Ltd.

The nuclear process at the heart of stars and the H-bomb, fusion, still appears to be several decades away from commercial power generation. Unlike fission, in which energy is released when large atomic nuclei split, fusion reactions release tremendous amounts of energy when two light atomic nuclei fuse to form a heavier nucleus. The light nuclei used are isotopes of hydrogen – deuterium and tritium – and are abundantly available in seawater or derived from lithium. Nuclear fusion promises cheap, safe and plentiful energy without greenhouse gas emissions, pollution, or radioactive waste.

However, nuclear fusion has to overcome huge technology barriers in terms of the energy required to initiate fusion (eg a plasma at a temperature around ten times greater than the core of the sun), and developing a means of containing the reaction.

While the energy input is great, the energy output is an order of magnitude greater. In terms of containment, magnetic containment has been at the core of major programmes like the Joint European Torus (JET) and its successor, ITER, scheduled for completion in Cadarache, France in 2018. Both rely on a tokamak (a doughnut-shaped steel chamber weighing 5,500 tonnes for ITER) with an immensely strong magnetic field  providing the confinement that prevents the superheated plasma from coming into contact with the walls of the chamber and melting them. While JET produced a peak of 16MW for less than a second, ITER is expected to produce 500MW sustained for up to 1,000 seconds.  A different approach, laser inertial confinement, is under way at the United States National Ignition Facility (NIF) and the European Union High Power Laser Research (HiPER) facility. Inertial confinement involves initiating the fusion reaction by heating a target containing deuterium and tritium (in a microcapsule, for example, or cryogenically cooled pellet) with an immensely powerful laser. The heated outer layer explodes, the reaction force compressing the remainder of the fuel pellet inwards with such great force that fusion occurs.The NIF system, brings its 192 beam petawatt laser system to bear on an air-gun pellet sized target is currently undergoing testing.

General Fusion, a Canadian company, combines magnetic and inertial fusion approaches in its magnetised fusion concept. The plasma is confined in a magnetic field and then compressed to thermonuclear conditions.  General Fusion aims to demonstrate net energy gain within four years and commercialisation by the end of the current decade. General Fusion recently announced that it has raised US$19.5 million in Series B funding from investors including Cenovus Energy and Bezos Expeditions. The company’s existing investors, Chrysalix Energy Venture Capital, GrowthWorks, Braemar Energy Ventures, Entrepreneurs Fund, Business Development Bank of Canada and SET Venture Partners also participated in the investment round. 

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