Manufacturing of superconducting magnets weighing more than 350 tons

Key figures

25m

Diameter of the biggest superconducting magnets

44
km

Cumulative length of superconducting cable wounded by CNIM

50

CNIM's employees involved on the project

The international ITER program, based in Cadarache (Bouches du Rhône, France) is a major international scientific project demonstrating the power of fusion as a large, unlimited and safe energy source. CNIM is actively contributing to this project through several design, manufacturing and installation contracts..

In 2015, F4E entrusted CNIM with the Poloidal Field Coil Manufacturing contract for the manufacturing of 4 of the 6 Poloidal Field Coils (PF Coils) superconducting magnets designed to create the "magnetic cage" which will help maintain the shape and stability of the plasma in the reactor. They measure between 18 and 25 meters in diameter and weigh up to 384 tons.

7_manufacturing_stations_PF_Coil_Foreground_superconducting_cable_coil-light_(c)F4E.jpg

7 manufacturing stations for the PF Coils : a dedicated workshop on ITER's site © F4E, ITER ORG

Maintaining the shape & the stability of the plasma

PF Coils are poloidal field magnets designed to keep the ultra-hot plasma (150 million degrees Celsius) away from the walls of the reactor and contribute to its shape and stability.

Six PF Coils in total will be positioned outside the toroidal magnetic structure: 2 are manufactured by Chinese and Russian companies, the 4 central magnets, the biggest, are manufactured by CNIM and ASG.

 

Picture : 6 PF Coils (in blue) positioned horizontally around the ITER vacuum vessel. The 4 biggest are manufactured by CNIM and ASG © ITER Org

 

A complex manufacturing process

The largest coils are manufactured by CNIM in collaboration with ASG, an Italian company specialized in the production of magnets, on the ITER site in a dedicated 250 m long building, the PF Building. The PF Building is composed of 8 manufacturing stations, each station is dedicated to a specific task.

Each magnet consists of "double pancakes" made of niobium-titanium superconducting cables.

Section of the superconducting niobium-titanium cable © CNIM

Delivered in 20-tons spools, the conductor is uncoiled and straightened before passing through cleaning and sandblasting machines that prepare its surface to receive several layers of glass-fibre insulating tape. Rotating tape heads enter into action as the conductor, fed from two spools simultaneously, joins the tooling table to be "turned" into the precise dimensions required for each coil. A double pancake is thus formed.

 

Winding operation of the superconducting cable © CNIM

The double pancake is transported by overhead crane to the vacuum pressure impregnation station and lowered into a custom-fit mold. Epoxy resin, injected over the course of several hours, fills all gaps and hardens the glass tape under the effect of heat and pressure. The resulting structure is rigid and homogeneous, providing excellent electrical insulation and mechanical strength.

The manufacturing process of a PF Coil - from winding activities to final assembly - will take approximately two years per coil.

 

Picture : Impregnation station, one of the 8 building stations © CNIM

Constant adaptability

CNIM has demonstrated its ability to set up a manufacturing workshop on its client's site in Cadarache and to work in a multi-contract and multilingual environment.

CNIM works upstream the product's life to manufacture very high precision "double pancakes" on the first 4 stations. CNIM’s team must make constant adjustments given the highly innovative nature of the project. CNM is also in charge of the production and supply of parts for the manufacture and assembly of PF Coils: purchasing and/or welding and/or pre-assembly.

Indeed, CNIM has been working on the ITER site for many years now and is involved in numerous contracts, including the contract for the manufacture of radial plates. Innovation and adaptability are part of our DNA.

Tests were carried out at different scales to validate the processes and verify the proper functioning of machines.

 

Picture : PF Coils building stations on ITER's site © ITER Org, F4E

A dedicated team set up on site

More than 50 CNIM employees are working in Cadarache to ensure the success of the ambitious PF Coil project.

CNIM has set up a complete team of experts dedicated to the success of the project: station operators, supervisors, welders, quality controllers, workshop manager, planner, scheduling, methods, project manager, etc. The key skills of our teams are mobilized for the success of this ambitious project.

Project management is at the heart of CNIM' DNA, our teams are able to design, industrialize and manufacture projects from A to Z with high added value.

 

Photo : Winding of a supraconducting magnets © CNIM

The project progresses

CNIM and ASG have finalized the production of double pancakes to form two PF Coils and will launch in mid-July the production of the third Poloidal Field Coil.

PF Coil 5, the first PF Coil manufactured by CNIM and ASG, measures 18 meters in diameter. The component will go into cryogenic testing in September 2020 (cold testing in order to simulate the thermal stresses and the work conditions that will be experienced during operation). The performance of the superconducting magnet will be tested before their installation in the ITER machine.

Representatives of F4E, ITER Organization welcoming the sixth Poloidal Field coil on-site, ITER site, Cadarache, June 2020 (c) F4E_ITER ORG.jpg

Picture : Representatives of F4E, ITER Organization welcoming the sixth Poloidal Field coil on-site, ITER site, Cadarache, June 2020 © F4E

The last PF Coil will be finished at the autumn 2023. The 6 PF Coils will be installed in the tokamak using the lifting beam system designed and manufactured by CNIM as part of the contract Purpose Built Tool. The lifting beam system is a specific tooling for handling components up to 700 tons and 17m high.