Nuclear fusion as alternative energy source: Wieland supplies high-performance copper alloys for the ITER research reactor

Superconductor bronze for international nuclear fusion project

A possible answer to future energy needs is to be provided by the international ITER project. ITER stands for International Thermonuclear Experimental Reactor – a research project to demonstrate the feasibility of nuclear fusion for large-scale energy production. For this purpose a research reactor is being constructed as from 2009 in Cadarache, France, by the European Union and Switzerland, Japan, the People’s Republic of China, India, the Republic of Korea, the Russian Federation and the USA. The € 10 billion project aims at researching whether and how nuclear fusion can be harnessed as a long-term alternative source of energy. An essential component for the acceleration of the atoms to be fused is a strong magnet made of superconducting wire. Superconductors conduct electricity without resistance and – at least theoretically – make a cost-effective operation of fusion reactors possible. The pre-material for the superconducting wire used is supplied by Wieland. Using high-performance copper alloys and the special spray-forming process Wieland provides part of the technical basis for the ITER project.

The nuclear fusion technology emulates the sun’s processes. A fusion power plant using heavy water nuclei (deuterium) produces larger amounts of energy than conventional nuclear power plants – and this with a much higher level of plant safety and almost no radioactive waste. Energy is generated through the controlled fusion of the nuclei of hydrogen atoms which are shot against each other at high speed. Extremely high magnetic fields are required to accelerate the atomic nuclei. These magnetic fields can only be produced with superconducting wire. The elements niobium and tin in the form of the alloy Nb3Sn are used as superconductors. This alloy is produced via the so-called bronze route – a time-consuming and complex process in which the material is formed considerably. A niobium rod several millimetres thick is inserted into a sectional tube made of tin bronze and then multiple bundles of such tubes are hot worked and cold drawn with intermediate anneals. This process places high demands on the homogeneity and the working properties of the bronze.

Spray-formed Wieland bronzes for superconductors
To produce these special bronzes Wieland-Werke AG, Ulm, Germany, uses the modern spray-forming technology. In spray forming a metal melt is atomised into fine droplets with an inert gas. Prior to complete solidification, the droplets impinge on a rotating substrate to form a billet. As the cooling rate in the atomised jet is very high, there are almost no segregation processes. The decisive advantage of spray-formed Wieland bronzes is that they are very homogeneous, i.e. the tin is evenly distributed, the grains are fine and the precipitate structures are optimised. From the beginning, Wieland superconductor components made by spray forming are used in the ITER project. The materials used are Wieland-BD3 (CuSn14.5Ti), Wieland-BC1 (CuSn15.5Ti) and Wieland-BD9 (CuSn16Ti).

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