Powerful superconducting magnets being constructed for the ITER fusion reactor are proving to be some of the largest and most complex ever built.
The magnets will be used to hold the reactor’s plasma - expected to reach 150 million degrees Celsius - in stasis in order to prevent it from touching the walls of the vessel it is contained in, which would be destroyed if exposed to the extreme temperatures.
The ITER fusion reactor is being constructed in southern France and is overseen by Fusion for Energy (F4E), a collaborative body with input from 35 nations.
It will be the first power-generating facility of its type and has the potential to produce virtually unlimited, eco-friendly energy using reactions similar to those which take place in the heart of the Sun.
The facility uses a magnetic fusion device that has been designed to prove the feasibility of fusion technology at a large-scale.
The new magnet, which will form part of ITER's first Toroidal Field coil (TF), is 14m high, 9m wide and 1m thick. Its weight is approximately 110,000kg - around the same weight as a Boeing 747.
ITER will eventually require 18 TF coils in order to operate, but the construction of the first one has involved at least 26 companies and 600 employees.
Winding, sandblasting and heat treatment have been some of the main steps taken in order to fit the conductor into stainless steel plates, known as radial plates.
Piece by piece the conductor had to be lifted, wrapped, insulated and placed back in the grooves of the plates before being covered. Then, the structure containing the conductor has been laser welded and wrapped with insulating material, before going through impregnation.
To create the inner-core of the TF coil, a pack of seven of these structures had to be stacked, electrically jointed, wrapped, insulated and impregnated.
Pipes have also been added, through which cold liquid helium will circulate inside the magnet to help it reach a superconducting state and instruments to measure its performance.
Alessandro Bonito-Oliva, F4E’s manager for magnets, said: “Thanks to our determination to meet the tight planning for magnets and the excellent collaboration between F4E and its suppliers we are heading towards Europe’s first TF coil, which also happens to be a first for ITER.
“Seeing a magnet of such complexity taking shape suggests that we can deliver some of the most technically challenging systems of ITER.
“Sharing expertise and good communication between F4E, ITER International Organization and Japan’s Domestic Agency for ITER have been fundamentally important for the achievement of this milestone and will continue to be as production is still ongoing.”
Efforts to get fusion reactor to operational status are still in progress. In March, the production of radial plates accelerated, reaching 45 out of a total of 70. Meanwhile, the manufacturing of the components of the second TF coil have been completed paving the way for its assembly.
Last September, some 200km of superconducting cables were manufactured for the project.
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