Safety of fusion magnets: Model experiments to high current arcs at ITER busbars and feeder lines

• Published in: Fusion engineering and design 2012-08, Vol.87 (5-6), p.675-679
• Main Authors: Klimenko, Dmitry, Pasler, Volker
• Format: Article
• Language: English
• Subjects: Electric arc; Magnet safety
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2012.02.005

► Arcing at an ITER busbar inside its feeder tube was simulated in small scale model experiments. ► Arc splitting in the presence of conducting structures will avoid long, huge power arcs in ITER. ► Surrounding structures do not impact arc burning down and propagation speed of the busbar cable end. ► Arcing may set free H and O from insulation resin and ignite it with delay outside the shielding tube. Electric arcs moving along the power cables (the so-called busbars) of the toroidal field (TF) coils of ITER may reach and penetrate the cryostat wall. Model experiments with the VACARC (VACuum ARC) device were initiated to investigate the propagation and destruction mechanisms of busbar arcs in small scale. These experiments are intended to support the development and validation of a numerical model. The present setup simulates the fact that the busbar is contained by an inner and an outer feeder tube which absorb radiated energy and will be in contact with hot metal melt from the busbar. The tubes may also direct the hot plasma jet flow of the arc as long as they are intact. Experiments at scaled values for tube diameter, wall thickness and expected power density suggest serious damage to the inner feeder tube by the arc. This asks for further investigations that include the outer tube, too. The extent of damage to the tube samples depends on arc power, as expected. At high currents an additional luminous effect takes place, which is attributed to a reaction of oxygen and hydrogen probably set free from the dissociation of the insulation resin by the heat of the arc.