In the relentless pursuit of harnessing fusion energy, scientists are tackling some of the most formidable challenges known to physics. Among these is the problem of hydrogen isotope retention in the materials that will line the walls of future fusion reactors. A recent study, led by Yi-Wen Sun of Beihang University in Beijing, has shed new light on how tungsten, a leading candidate for these reactor walls, behaves under extreme conditions. The findings, published in Nuclear Fusion, could significantly influence the design and operation of future fusion power plants.
Fusion reactors aim to replicate the process that powers the sun, combining light atomic nuclei to release vast amounts of energy. However, the plasma— the hot, charged gas where fusion occurs—is incredibly harsh, subjecting reactor walls to intense heat and particle bombardment. Tungsten, with its high melting point and resistance to plasma damage, is a prime candidate for these walls. But how it behaves under the extreme conditions expected in a future fusion power plant remains a critical question.
Sun and her team exposed recrystallized tungsten samples to high-flux deuterium plasma, mimicking the conditions expected in the divertor region of a fusion reactor. The divertor is a crucial component that removes heat and particles from the plasma, but it also bears the brunt of the plasma’s fury. The team subjected their samples to plasma fluences up to 1 × 10^29 particles per square meter, a level expected in future reactors.
The results were revealing. Initially, the tungsten surface developed blisters as deuterium was implanted into the material. But as the fluence increased, these blisters began to burst, creating open cracks and edges. “We observed multiple bursts of blisters under the highest fluences,” Sun explained. “This suggests that the tungsten surface is dynamically evolving under high-flux plasma exposure.”
The team also measured the deuterium retention in the tungsten samples. They found that the deuterium concentration saturated with increasing fluence, reaching a maximum of 0.012 atomic fraction at a depth of about 4 micrometers. This saturation is attributed to modifications in the surface morphology and the saturation of plasma-induced defects.
The implications for fusion energy are significant. Understanding how tungsten retains deuterium under high-fluence plasma exposure is crucial for designing effective divertor materials. “Our investigation provides a valuable reference for understanding the evolution of total hydrogen isotope retention in tungsten under high-fluence plasma exposure in future fusion devices,” Sun said.
This research could influence the development of materials and strategies for managing hydrogen isotope retention in future fusion reactors. It may also guide the design of divertor components, helping to ensure they can withstand the extreme conditions of a fusion plasma. As the world looks to fusion as a potential source of clean, abundant energy, studies like this one are paving the way for its realization. The findings, published in Nuclear Fusion, mark a significant step forward in our understanding of how materials behave in the harsh environment of a fusion reactor.
