Exel Composites and CNIM collaborate on glass fiber components for world's most ambitious fusion project


Global pultrusion company Exel Composites is collaborating with French industrial contractor CNIM on the manufacture of fiberglass components for the magnet support structure of the International Thermonuclear Experimental Reactor (ITER), the world’s largest experimental fusion facility. To satisfy the stringent quality demands for the pre-compression rings, Exel Composites successfully solved the challenge of producing defect-free pultruded profiles of around 3 km in length.

The €18 billion ITER under construction in Saint-Paul-lez-Durance, France, is designed to demonstrate that fusion power can be produced on a commercial scale, providing a safe, environmentally sustainable energy source. The ITER will use hydrogen fusion, controlled by superconducting magnets, to produce massive heat energy. In the commercial machines that will follow, this heat will drive turbines to produce electricity.

The composite pre-compression rings are the cornerstone of the ITER’s magnet system support structure. They will ensure the operation of the toroidal field coils employed to create a magnetic ‘cage’ to confine the super-hot (150 million °C) plasma. To reduce fatigue and deformation of the coils resulting from the powerful magnetic fields, three pre-compression rings will be placed on top of them and three below. An extra set of three will be manufactured in case replacement becomes necessary in future. The pre-compression rings are required to withstand maximum hoop stresses of up to 500 MPa at room temperature. Glass fibre epoxy composite with a high fibre content was selected as the most suitable material to withstand such extreme loads, avoid circulation of electromagnetic currents and deliver a long service life. The composite rings will have a diameter of approximately 5 m, a cross-section of nearly 30 cm x 30 cm and will weigh slightly more than 3 tons.

Engineers at CNIM’s workshop in Toulon have been tasked with developing a manufacturing process for the spare pre-compression rings, and their subsequent production. The novel process relies on pultruded composite profiles produced by Exel Composites. Each ring will be produced by winding a 2 mm thick, 2.8 km long, flat pultruded profile around a metal tool. A 0.12 mm thick epoxy adhesive tape is wound over each layer. The completed ring lay-up is cured and then machined to the required final dimensions.

CNIM selected Exel Composites for this project based on the company’s proven capability in the manufacture products of superior quality for the most demanding applications. Exel formulated a high performance epoxy resin system to meet the mechanical specifications for the pre-compression rings and ensured that the 3 km profiles supplied were defect-free along their entire length by means of online non-destructive testing (NDT). The handling of this length of profile presented a further challenge, which Exel solved by winding the product on a customised bobbin for supply to CNIM.

CNIM has already manufactured a series of prototypes, which are currently undergoing NDT and qualification tests. Production of the full-scale pre-compression rings will begin later this year. “We are proud to support the ground-breaking ITER demonstrator as it prepares the way for the fusion power plants of tomorrow,” states Kari Loukola, Senior Vice President, Sales & Marketing, Exel Composites. “This represents a further example of Exel’s commitment to innovation and collaboration with our customers in the pursuit of new applications for composite materials.” The ITER facility itself is now 50% complete, with First Plasma (machine switch on) scheduled for 2025. ITER scientists predict that fusion plants could start to come on line as soon as 2040.

Notes for Editors

Fusion research is aimed at developing a safe, abundant and environmentally responsible energy source. Fusion is the process that powers the sun and the stars: when light atomic nuclei fuse together to form heavier ones, a large amount of energy is released. Fusion energy is carbon-free and environmentally sustainable, yet much more powerful than fossil fuels. A pineapple-sized amount of hydrogen offers as much fusion energy as 10,000 tons of coal.

The ITER is designed to demonstrate the scientific and technological feasibility of fusion power and will be the world’s largest experimental fusion facility. It is the most complex science project in human history. The hydrogen plasma will be heated to 150 million °C, ten times hotter than the core of the Sun, to enable the fusion reaction. The process happens in a donut-shaped reactor called a tokamak, which is surrounded by giant magnets that confine and circulate the superheated, ionized plasma, away from the metal walls. The superconducting magnets must be cooled to -269°C, as cold as interstellar space. The ITER facility is being built by a scientific partnership of 35 countries. Its specialized components, roughly 10 million parts in total, are being manufactured in industrial facilities all over the world. Each of the seven ITER members – the European Union, China, India, Japan, Korea, Russia, and the United States – is fabricating a significant portion of the machine. For more information on the ITER please visit www.iter.org.

Exel Composites

Exel Composites is a leading composites technology company specialising in the design and manufacture of composite solutions for demanding applications. Exel Composites provides superior customer experience through continuous innovation, world-class operations and long-term partnerships. The core of Exel’s operations is the company’s proprietary technology, product range and strong market position in selected market segments where it holds a strong quality and brand image. Profitable growth is pursued by a relentless search for new applications and development in cooperation with customers. Exel Composites Plc shares are listed on Nasdaq Helsinki Ltd. For further information visit exelcomposites.com.


Founded in 1856, CNIM is a French equipment manufacturer and industrial contractor operating on a worldwide basis. The group provides products and services to major public and private sector organizations, local authorities and national governments in the environment, energy, defense and high technology markets. Technological innovation is at the core of the group’s equipment and services, which contribute to producing cleaner and more competitive energy, limiting environmental impacts of industrial activities, securing sensitive facilities and infrastructures, and protecting individuals and nation states. CNIM is listed on the Euronext exchange in Paris. For further information visit cnim.com.

Further information

Mr. Kari Loukola, Senior Vice President, Sales & Marketing, Exel Composites tel. +358 40 5040 755 kari.loukola@exelcomposites.com