The largest project in the history of humanity is about to enter a key phase: the final assembly of the reactor core, led by an American giant.

The world’s most ambitious fusion energy project has reached a critical milestone as Westinghouse Electric Company takes charge of assembling the core of ITER’s fusion reactor. This massive international collaboration, based in Cadarache, southern France, aims to harness the power of nuclear fusion—the same process that powers our sun—to create clean, virtually limitless energy for humanity’s future.

Westinghouse leads final assembly of ITER’s tokamak core

In August 2025, ITER’s fusion project entered its most technically challenging phase yet : the final assembly of the reactor’s core. American nuclear giant Westinghouse secured a €168 million contract to lead this critical operation, which involves the precise installation and welding of nine massive steel sectors to form the tokamak’s vacuum vessel—the heart of the fusion reactor.

The tokamak’s vacuum vessel forms a donut-shaped chamber where fusion will eventually occur. Each 400-ton sector must be positioned and welded with millimeter precision to create a perfectly circular, hermetically sealed chamber. Inside this vessel, hydrogen plasma will be heated to over 150 million degrees Celsius—temperatures far exceeding those found at the center of our sun—to trigger nuclear fusion.

Westinghouse brings over a decade of ITER experience to this task. The company has worked in partnership with Italian firms Ansaldo Nucleare and Walter Tosto as part of the AMW consortium, which has already manufactured five of the nine vacuum vessel sectors. The expertise required for this assembly resembles handling forces of immense magnitude, where precision engineering must contain enormous energy safely.

Bernard Bigot, former ITER Director-General, once described this challenge as “assembling a three-dimensional puzzle on an industrial scale.” The vacuum vessel must withstand extreme thermal stresses, magnetic forces, and maintain perfect internal conditions for plasma containment—making it one of the most sophisticated engineering projects ever attempted.

Global collaboration of unprecedented scale

ITER represents an extraordinary example of international scientific cooperation, uniting 35 nations in pursuit of fusion energy. The project partners include the European Union, United States, China, Russia, Japan, India, and South Korea—together representing over half the world’s population and 85% of global GDP.

What makes ITER particularly remarkable is its collaborative structure. Each participating nation contributes specific components manufactured to exacting specifications before being shipped to France for assembly. This approach resembles a global supply chain for scientific advancement, with components traveling from facilities across four continents before reaching their final destination.

The scale of this international partnership exceeds even other massive scientific endeavors, creating a template for how humanity might tackle other global challenges. Much like scientists studying Earth’s transformative geological processes, ITER’s teams are witnessing the birth of something entirely new through collaborative effort.

Key ITER contributions include :

• Europe : Construction site, buildings, and 45.6% of components
• United States : Central solenoid magnet system and cooling water systems
• China : Correction coils and power supply components
• Japan : Toroidal field coils and central solenoid conductor
• Russia : Poloidal field coils and specialized diagnostic systems

Technical ambitions and timeline challenges

ITER’s primary technical goal is to demonstrate fusion power at commercial scale. The reactor aims to produce 500 megawatts of fusion power from 50 megawatts of input power—a tenfold return that would prove fusion’s viability as an energy source. This achievement would represent a breakthrough comparable to observing celestial phenomena through revolutionary telescopes, offering humanity a glimpse of its potential energy future.

However, the project has faced significant timeline adjustments since breaking ground in 2010. Initially targeting first plasma operations by 2018, the schedule has been revised multiple times due to technical complexities, supply chain challenges, and the sheer difficulty of coordinating contributions from dozens of countries. Current projections aim for meaningful deuterium-tritium fusion experiments by 2035.

This timeline extension reflects fusion energy’s persistent challenge : creating and maintaining the precise conditions for sustained nuclear fusion. The famous industry saying that fusion is “always 30 years away” highlights the technical hurdles that have consistently pushed commercialization timelines further into the future.

Beyond ITER : The roadmap to fusion power

ITER represents not an endpoint but a crucial stepping stone toward commercial fusion energy. Despite its immense scale, ITER remains a scientific experiment that will not generate electricity for the grid. The knowledge gained will inform the next-generation DEMO reactors, which aim to demonstrate commercial power production.

Fusion energy offers compelling advantages as a power source. Unlike conventional nuclear fission, fusion produces no long-lived radioactive waste and cannot sustain a runaway chain reaction. Its fuel sources—primarily isotopes of hydrogen—are abundant, with enough deuterium in Earth’s oceans to power civilization for millions of years.

The timeline from ITER to commercial fusion spans decades, requiring patience comparable to that needed when studying geological processes that reshape continents. Yet the potential reward—a nearly limitless, clean energy source—continues to drive international investment despite the extended timeline.

Many fusion experts believe that ITER’s success will spawn multiple approaches to commercial fusion. While ITER uses the tokamak design, alternative concepts like stellarators, inertial confinement, and magnetic mirror machines are advancing in parallel, creating a diverse ecosystem of fusion technologies that may accelerate the path to practical implementation.

As Westinghouse begins the delicate process of assembling ITER’s core, humanity moves one step closer to harnessing the power of stars. This landmark moment in the fusion energy quest represents not just a technical achievement but a testament to what international cooperation can accomplish when focused on solving our greatest challenges.