What major international experimental fusion reactor, located in France, achieved its first plasma in December 2025?

The major international experimental fusion reactor located in France, which was projected to achieve its first plasma in December 2025, is known as ITER. This ambitious project, whose name is Latin for "the way," is a collaborative effort involving 35 nations, including China, the European Union, India, Japan, South Korea, Russia, and the United States. Its primary goal is to demonstrate the scientific and technological feasibility of fusion power as a large-scale, carbon-free energy source.

ITER is being constructed in Saint-Paul-lès-Durance, France, and is designed to be the world's largest magnetic confinement plasma physics experiment, using a tokamak device. The concept of fusion power aims to replicate the process that powers the sun and stars, where light atomic nuclei combine under immense heat and pressure to release vast amounts of energy. Achieving "first plasma" is a critical initial step in the reactor's operational timeline, involving the creation of a superheated, ionized gas within the tokamak to test the machine's magnetic confinement system and other vital components.

This milestone marks the beginning of a long experimental campaign, moving towards eventually demonstrating sustained fusion reactions. The successful operation of ITER is considered essential for advancing fusion energy research and developing the technologies needed for future commercial fusion power plants. The project represents a monumental international scientific and engineering endeavor, striving to unlock a potentially limitless (Review) and environmentally responsible energy source for humanity.