Bringing mythical electrical power to MITICA

o heat up ITER’s plasma at 150 million ˚ C, roughly ten times the temperature at the core of the sun, we will need powerful heating systems using high-energy beams.  By raising the temperature of the hot gas we accelerate the speed of the two nuclei (deuterium and tritium) to make them crush in order to trigger off a fusion reaction. The principle is simple. In practice, however, this requires the fabrication and testing of new equipment before manufacturing the components for ITER. For this reason a facility has been set up at the premises of Consorzio RFX in Padua (Italy) to develop and test a Neutral Beam Injector (NBI) prototype.  MITICA, which stands for Megavolt ITER Injector and Concept Advancement, relies on the in-kind contributions of F4E, ITER Organization, the ITER Domestic Agencies of India and Japan, plus Consorzio RFX. And just like its acronym suggests, in this ITER facility there will be tests performed with “mythical” levels of beam energy and electrical power.

F4E and Siemens started working together 3 years ago in order to develop three units that will be part of the power supplies for the Neutral Beam Injection system. Each unit is made of: i) an electrically insulated box, so-called “High Voltage Deck”, that hosts the power supplies for the ion source of the injector, ii) a gas-insulated bushing, called “High Voltage Bushing Assembly”, bringing the electrical power through the transmission line all the way to the ion source. To reach the required high voltage insulation levels of 1 MV they are using SF6, a potent greenhouse gas, as electric insulator.

The insulated box is distributed over two floors covering a surface of 150 m².  Think of it as a Faraday cage that can maintain a level of voltage of 1 MV isolating the power supplies of the ion source from the ground. Inside its shiny metallic shell there are transformers, power distribution systems, converters and control cubicles weighing approximately 50 T. The box rests on eight insulated “columns” which are more than 6 m high above the floor. The installation of the High Voltage Deck has now been completed. It has successfully passed the electrical acceptance tests in a factory, and has concluded the mechanical, structural and seismic tests at the MITICA facility.

Meanwhile there has been excellent progress on the bushing assembly, supplied by Siemens and its subcontractor HSP GmbH, which is connecting the power supplies of the ion source to the transmission line. The equipment has been fully installed and all tests required have been properly completed. It is now ready to be connected to the transmission line supplied by Japan and then to proceed with the final tests of the entire system.

“The bushing is a-first-of-a-kind equipment which was not available on the market at the time of procurement.  We collaborated closely with our industrial partners to manufacture it and worked out together the challenging logistics for its installation at the MITICA facility. The bushing assembly has a height of 12 m and weighs approximately 19 T. This European equipment will be connected to the transmission line which has been designed and built by Japan. This is the outcome of strong international collaboration which is in line with the spirit of the ITER project” explains Muriel Simon, F4E’s Technical Responsible Officer following the contract with Siemens.

Michael Krohn, Project Manager of Siemens, explains that “the involvement of our company in this project offered us the opportunity to bring in our experience in global business together with our excellent technical expertise delivering standard and customised solutions. Thanks to our collaboration with F4E, we have become familiar with the ITER project and fusion for energy.”

Tullio Bonicelli, Head of F4E’s Neutral Beam and Electron Cyclotron, Power Supplies and Sources, highlights that “the successful delivery and installation of these “beyond the state-of-art” components at the MITICA facility paves the way for more tests that will be performed during the second half of the year after the equipment is connected to the transmission line. The operation of such extensive system at 1 MV is not only challenging but also unprecedented. The fusion community will be looking at us for answers in order to take our next step towards the fabrication of the ITER Neutral Beam components.”