Tungsten - Material of Choice for the Burning Chamber
Scientists report positive results with new wall materials at PSI 2012 conference
Aachen/Jülich, 23 May 2012 – Wall components made of tungsten will play a central role in future fusion reactors. This is the most important insight discussed at the 20th International Conference on Plasma Surface Interactions in Controlled Fusion Devices (PSI 2012), held in Aachen from 21st to 25th May and organized this year by Forschungszentrum Jülich. Based on the design for the ITER fusion reactor under construction in south of France, similar wall components made of tungsten and beryllium have been installed in the European tokamak JET. The experiments done with this new wall have been reported at the conference for the first time. The results show a positive experience with the ITER wall, which is a large step forward for a successful operation of ITER.
The lining of the burning chamber is one of the key issues in constructing future fusion reactors. In order for the reactors to be operated in a continuous, fail-safe and cost-effective manner, the walls will have to withstand extreme conditions over a number of years. Inside the burning chamber, the temperature is above 100 million degrees. The materials used must be robust, the erosion and their impact on the fuel gas mixture comprising the hydrogen isotopes of deuterium and tritium must be minimised.The fusion experiments built to date had protective shields made of graphite, as used in spacecraft for re-entry into the earth’s atmosphere. However, this material does not fulfil the requirements for ITER, which is due to go into operation in 2020 in Cadarache in the south of France and future fusion reactors. Therefore, the “first wall” for ITER will be constructed from beryllium and tungsten – the element with the highest melting point at 3422 °C.
Nevertheless, tungsten as impurity in the fusion plasma needs to be minimised and the interplay of beryllium and tungsten as wall materials must be clarified. For this reason, experiments with an ITER-Like Wall have been carried out at JET since September 2011, coordinated by EFDA – European Fusion Development Agreement. The new design envisaged for ITER contains a tungsten structure that weighs two tonnes and is constructed from 10,000 individual components. It was developed and assembled by Forschungszentrum Jülich with a budget of € 10 million.
At the 20th International Conference on Plasma Surface Interactions (PSI 2012), fusion researchers have presented the – positive – results of the first test period for the very first time. Undesired contamination of the fusion plasma with oxygen and residual carbon was greatly reduced. The erosion of tungsten from the new wall structure is substantially lower than from its graphite counterpart. Most importantly, the new wall materials retain much less fuel gas compared with graphitic wall components.
Dr. Guy F. Matthews, Culham Centre for Fusion Energy, Culham Science Centre, UK
Tel. +44 1235464523
Dr. Sebastijan Brezinsek, Institute of Energy and Climate Research – Plasma Physics, Forschungszentrum Jülich, Germany and chairman of the PSI 2012
Tel. +49 2461 61-6611
Dr. Volker Philipps, Institute of Energy and Climate Research – Plasma Physics, Forschungszentrum Jülich, Germany
Tel. +49 2461 61-6331
Tobias Schlößer, Corporate Communications, Forschungszentrum Jülich, Germany
Tel. +49 2461-61-4771