Superconductor work progresses for Iter

Wednesday, 21 March 2012

Milestones have been reached in the preparatory work for the international next generation fusion reactor, Iter, as Chinese and Italian suppliers complete the construction of key manufacturing facilities and trial versions of parts for the superconducting magnets.

In late February China completed and shipped its first major component for the project - 660 metres of toroidal field dummy conductor; while in Italy in early march the Italian Consortium for Applied Superconductivity (ICAS) completed the commissioning of the jacketing line facility, as well as equipment needed for the manufacturing of conductors.

Dummy superconductor coiling being made in Hufei; and offloaded in Fukuoka

The superconducting magnets are some of the highest value and most essential components of the Iter reactor, which is soon to start construction at Cadarache in Southern France. The reactor is to be a kind of tokamak – a doughnut-shaped vacuum vessel which, when operational, will confine and heat a plasma of deuterium and tritium ions to achieve sustained nuclear fusion.

Confinement of the plasma is maintained through the toroidal field system which keeps the plasma moving around the chamber, and a poloidal field which pinches the plasma and keeps it away from the walls. In total Iter will require 16 toroidal field and six poloidal field coils. Each D-shaped toroidal coil contains multiple strands of superconducting cable, and weighs in at about 363 tonnes. Each cable consists of about 1000 strands of a special alloy of niobium and twisted together and encased in a steel jacket.

The 'dummy' version replaces this alloy with copper so as to qualify the cabling and jacketing process without wasting the more valuable superconducting material. In the jacketing process long sections are welded together into a line about 750 metres long and the cable is drawn through it, allowing weld quality to be checked and repaired if necessary.

Member contributions

Twenty kilometres outside of Turin, ICAS – a consortium of ENEA, Tratos Cavi and Criotec – has just completed the commissioning of a facility to fabricate and test superconductor. An 800 metre jacketing platform has been assembled just outside this. The consortium intends to produce three superconducting dummies, with two dummies produced by the end of June this year. ICAS will eventually produce 27 production lengths, measuring approximately 20 kilometres, for the Iter toroidal field coils and will supply jacketing for 22 kilometres worth of the poloidal field coil.  

The Chinese dummy magnet conductor was constructed at a facility in Hefei. It reached Fukuoka on 10 March having departed from a port in Shanghai on 26 February. The dummy conductor will be stored at the Wakamatsu site awaiting further processing. This is the first shipment of a major component to be completed component between Iter member countries.

Iter is overseen by seven domestic agencies representing China, the European Union, India, Japan, Russia, South Korea and the United States. It relies upon in-kind contributions from these member agencies for component work packages which have been divided between them. This international scientific collaboration is the largest in the world.  

The schedule for the Iter project looks set to be delayed by a year, in part due to the disruptive influence of the natural disasters that struck Japan last March. However the project remains on track to meet costs targets established in an extraordinary meeting in July 2010. The first major part is due to arrive at the site in 2014 and first plasma remains nominally slated for 2019.

Research and written
by World Nuclear News