Iter & West: Nuclear Fusion Gaining Momentum at Cadarache

Nuclear fusion is advancing rapidly, including within France. On one hand, the CEA’s WEST reactor has completed its experimental campaign by setting a new record. On the other hand, the final poloidal field coil for ITER has been delivered.

WEST, standing for Tungsten (chemical symbol “W”) Environment in Steady-state Tokamak, is a research tokamak for magnetic confinement nuclear fusion, located at the CEA site in Cadarache. It utilizes tungsten as the material for lining the interior walls. This material, due to its high heat resistance, could be best suited for future fusion power plants. A few kilometers from this site is ITER. Involving more than 35 countries, it is the most ambitious nuclear fusion project, benefiting from all the studies conducted worldwide (including those partially from WEST) in this field.

A New Record

After just under four months of experimental campaign, the WEST tokamak has set its new fusion record. The plasma reached a temperature of 50 million degrees Celsius for a duration of six minutes and four seconds (with 1.15 gigajoules of power injected). This represents 15% more energy than the previous configuration of the tokamak with twice the plasma’s electron density.

Beyond the record, this campaign provided an opportunity to achieve new advancements, which in the future could potentially be implemented for the operation of ITER. Firstly, an X-ray diagnostic method, developed by researchers from the Princeton Plasma Physics Laboratory (PPPL), enabled efficient measurement of the electron temperature within the plasma and the density of impurities, largely composed of tungsten eroded from the wall, which could affect the tokamak’s operation. Secondly, experimental scenarios were also conducted to explore the temperature distribution within the plasma to improve the lifespan of the components facing the plasma.

New Coil for ITER

The sixth and last poloidal field coil has been completed and delivered to the ITER site in Cadarache. These large circular coils correspond to giant magnets, positioned around the vessel, which will help confine the plasma so as to keep it away from the walls. This sixth coil, PF3, is the largest of the lot as it measures 24.7 meters and weighs 384 tonnes. It is one of the four that were manufactured in the winding facility near the Cadarache site with the participation of numerous European companies. The two smaller ones were produced in China and Russia.

The completion of this final project has shown that the F4E (Fusion for Energy) teams have experienced a real increase in expertise throughout, contributing to a significant time-saving on the entire project. Indeed, as explained by Enrico Vizio, the Acting Magnets program leader at F4E, it took “about 2 years and 9 months to complete PF3, which is about 15% less time than PF4 and about 40% less than PF5.” The PF3 coil has now joined the reserve, alongside three others, awaiting installation on the tokamak. Two coils have already been installed. ■

By François Terminet (Sfen)

Photo: Inside the WEST tokamak, Source: ©CEA-IRFM