Utility Week

Utility of the Future: climate change UTILITY WEEK | 20TH - 26TH SEPTEMBER 2019 | 11 The Utility of the Future is being adopted as the headline theme of next year's Utility Week Live, the UK's leading utility conference and exhibiton. One of the tokamak reactors at the Culham Centre for Fusion Energy and we're talking about 500MW of heat out" for 50MW put in, explains Walters. ITER, and some start-ups, are planning to overcome this issue by using superconducting electromagnets. Here the containment system will be made with coils of specialist material that has, when cooled to cryogenic temperatures, zero electrical resistance and can operate at length without overheating. This is not without issue, as these materials must be cooled to near absolute zero in close vicinity of the reacting plasma, which can be in the area of 100 million degrees Celsius. Once stabilised for longer, the reaction can be made even more efficient by generating tritium in the reactor itself. Of the two fuels for fusion, deuterium can be harvested from seawa- ter, whereas tritium occurring naturally on Earth is rare, so it must be manufactured. The NFTP hopes to achieve this by finding the most effective ways to place lithium-6 in the reactor and bombard it with neutrons produced by the fusion reaction. This would produce tritium and, ideally, create "a sort of self-sus- taining process". The greatest material difficulty comes from plasma-facing components, with which there are two main challenges. One is the heat flux, where the internal reactor walls can experience conditions similar to a space cra' on atmos- pheric re-entry, "the other one is the neutron flux, which is very high energy neutrons". While these neutrons are very useful when they react to produce more fuel, they are less so when they react with structural metals. Components exposed to neutrons can experience "dislocation". Walters describes this as neutrons colliding with the atoms of a piece of steel at great speed and knocking them out of the cubic lattice. Like a jigsaw where you have shuffled the pieces around a hundred times; "you might not end up with the original picture". Dislocation causes change in the material's structure at an atomic level, which affects the structural integrity of components and can cause them to become brittle or lose strength, properties that are somewhat undesirable in a nuclear reactor and can mean that a reactor made of unsuitable materials may need con- stant component replacement to operate. Finding materials that can stand up to these conditions is especially difficult because "very few organisations have got the challenges we've got". The nature of the problem means CCFE must, in some cases, develop its own materials, which it does with universities, industry, and other research centres. This is another of the tasks for the NFTP, as the organisation designs tests for simulating the "extremely challenging" fusion conditions, in terms of "heat, vacuums, strong magnetic fields, massive neutron doses", and identifying construction materials that are up to task.

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