Another concrete step for Iter

6 February 2009

Testing has begun on one of Iter’s key components – The Divertor Test Platform Facility (DTP2).

The design and manufacture of the full-scale prototype, recently assembled in Tampere, Finland, has taken four years and has cost €7 million ($9 million), half of which was funded by the Euratom programme. It is the culmination of efforts from scientists all over Europe, working together with four industrial partners based in Finland, Luxemborg and Spain.

Director general for research at Euratom, Octavio Quintana Trias, described the start of DTP2 prototype testing as: “another concrete step towards the realisation of a project that has been dreamed of for years.”

The divertor is one of the key components that will be found inside the fusion reactor. Its function will be to extract heat, “helium-ash” – the products of the fusion reaction – and other impurities from the plasma, in effect acting like a giant exhaust pipe. It will comprise two main parts: a supporting structure made primarily from stainless steel and the plasma facing component, weighing about 700t in total. The plasma facing component will be made of a high refractory material such as tungsten-carbon fibre composite.

As the divertor will be a plasma facing component, subject to extreme conditions (the deuterium and tritium gases need to be heated to 100 million degrees centigrade for sustainable fusion) it will suffer from erosion. In fact, it is estimated that the divertor will need to be replaced at least three times during the reactor's proposed 20-year lifetime. For maintenance purposes, the divertor will be made up of 54 sections or cassettes.

Since the conditions inside the vacuum containment - where the divertor will be located - will be harsh due to neutron radiation/tritium presence, it will be inaccessible to humans. Therefore any maintenance or vital repairs must be carried out in a remote manner, which is where the DTP2 platform comes in.

The purpose of the DTP2 facility is to test and demonstrate all the remote handling operations of the Iter divertor, providing input to the final specifications of the maintenance platform.

The main element of the platform is the Divertor Region Mock-Up (DRM), a large structure that replicates the geometry of the lower part of Iter’s vessel and one radial port. The DRM provides the radial and toroidal rails to support the divertor cassettes, and the rails for remote handling equipment which carry out the divertor maintenance. Such equipment includes prototypes of the Cassette Multi-functional Mover (CMM) and the Secondary Cassette End Effector (SCEE). The CMM, weighing 65t, will run on a 20m supporting structure, transporting the divertor cassettes (9 to 10t each) along rails to and from Iter’s plasma chamber.

The design and manufacture of the CMM and SCEE prototypes were carried out by the Spanish company Telstar Tecnologia Mecanica SL at its facility in Terrassa, near Bacelona. VTT Systems Engineering and Tampere University of Technology (members of the Finnish fusion association Tekes) constructed the mock-up that replicates a section of the Iter divertor region. The components used were manufactured by companies in Finland (TP-Konepajat Oy) and Luxembourg (Gradel SA). While the CMM was being constructed in Spain, scientists from Tampere University of Technology were developing and testing the software necessary to control it. This was achieved by linking the control hardware, supplied by a second Spanish company, Procon Systems SA, to a virtual model of the CMM.

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