In the quest for sustainable and abundant energy, nuclear fusion remains a tantalizing prospect. Researchers at the CEA, IRFM in Saint-Paul-Lez-Durance, France, led by C. Guillemaut, are delving into the intricacies of plasma start-up conditions, a critical phase in the fusion process. Their recent findings, published in the journal Nuclear Fusion, could significantly impact the design and operation of future fusion power plants, including the much-anticipated ITER project.
The study focuses on the WEST (W Environment in Steady-state Tokamak) facility, which has been instrumental in testing different first wall materials. Until recently, WEST featured a full high Z (high atomic number) first wall, primarily composed of tungsten. In 2020, the team introduced boron nitride tiles to the central part of the inner and outer limiters, effectively creating a low Z environment. This shift aimed to understand how different materials influence plasma start-up conditions and overall efficiency.
Guillemaut and his team observed a notable reduction in tungsten impurity sources and radiated power after the switch to boron nitride. However, the benefits were not without caveats. Over time, the low Z materials degraded with increased plasma exposure, highlighting the challenges of maintaining a low Z environment. “The different plasma facing elements of the main chamber do not influence equally the radiated power during start-up,” Guillemaut noted, underscoring the complexity of material interactions in fusion reactors.
The research also revealed a non-linear relationship between the start-up radiated power and the outer limiter tungsten impurity source, suggesting that tungsten plays a significant role in core radiation. This finding is crucial for optimizing plasma start-up scenarios and material choices in future fusion reactors.
The legacy of boron powder drops on start-up plasmas provided additional insights. While boron initially showed promise in reducing radiated power, its effectiveness waned when the first wall was covered with tungsten. This indicates that the interaction between different materials and their long-term effects on plasma performance need careful consideration.
The implications of this research are profound for the energy sector. As the world seeks cleaner and more sustainable energy sources, understanding and optimizing plasma start-up conditions could pave the way for more efficient and reliable fusion power plants. The findings from WEST could guide the design and material selection for future reactors, potentially accelerating the commercial viability of nuclear fusion.
By publishing these results in Nuclear Fusion, the international journal of fusion energy research, Guillemaut and his team have contributed to a global effort to harness the power of the stars. Their work underscores the importance of material science in fusion research and highlights the need for continuous innovation in this rapidly evolving field. As we stand on the brink of a fusion energy breakthrough, every step forward brings us closer to a future where clean, abundant energy is a reality.
