In the relentless pursuit of carbon-free energy, nuclear fusion stands as a beacon of hope. However, the journey to harnessing this power is fraught with challenges, particularly when it comes to the materials that must withstand the harsh conditions of fusion reactions. Recent research published in Nuclear Materials and Energy, led by L. Corso of CEA, IRFM, and Aix Marseille Univ, CNRS, CINAM, sheds new light on one of these challenges: the damaging effects of helium irradiation on tungsten, a promising material for fusion reactors.
Tungsten, with its high melting point and resistance to sputtering, is a prime candidate for the walls facing the plasma in fusion reactors. However, the bombardment of helium ions during operation can lead to the formation of helium bubbles within the material, which can significantly degrade its mechanical properties and reduce its lifespan. Understanding how these bubbles form and grow is crucial for developing materials that can withstand the rigors of fusion environments.
Corso and his team employed a cutting-edge technique called grazing incidence small angle X-ray scattering (GISAXS) to study the real-time nucleation and growth of helium bubbles in tungsten during helium bombardment at 1273 K (approximately 1000°C). By carefully adjusting the X-ray incident angle, the researchers could distinguish between the contributions of the surface and the bubbles, providing a clearer picture of the processes at play.
“The occurrence of tilted diffuse scattering rods proves the presence of facetted bubbles buried inside the tungsten matrix,” Corso explained. This observation is a significant step forward in understanding the behavior of helium bubbles in tungsten. The team’s analysis of the time evolution of X-ray diffuse scattering revealed that the growth kinetics of these bubbles are dominated by a process called migration-coalescence, where bubbles move and merge with one another. This process is hindered by the nucleation of ledges at the bubble facet surface, a finding that could have important implications for material design.
The insights gained from this research could pave the way for developing more resilient materials for fusion reactors. By understanding the mechanisms behind helium bubble formation and growth, scientists can engineer materials that are better equipped to handle the harsh conditions of fusion environments. This could lead to longer-lasting, more efficient reactors, bringing us one step closer to the realization of practical fusion power.
As Corso noted, “A close comparison with analytical modelling of the growth process suggests a growth kinetics dominated by the migration-coalescence of bubbles.” This understanding could inform the development of new materials or treatments that slow down or even prevent the deleterious effects of helium irradiation. The potential commercial impacts are vast, as the energy sector eagerly awaits the day when fusion power becomes a viable, large-scale energy source.
The study, published in Nuclear Materials and Energy, titled “Real-time helium bubble growth in tungsten by in-situ GISAXS,” represents a significant advancement in our understanding of materials for fusion energy. As we continue to push the boundaries of what is possible, research like this will be instrumental in shaping the future of energy.
