Hydrogen isotope transport in plasma-facing components is a critical issue for nuclear fusion devices, as it directly affects fuel retention, permeation, and material integrity. In ITER-like divertor designs, tungsten monoblocks are bonded to copper-based heat sinks, forming W/Cu interfaces that play a key role in hydrogen migration from the plasma-facing surface toward the coolant. At the atomic scale, such interfacial regions present additional challenges, as interstitial diffusion is inherently more complex than in bulk materials due to asymmetries in the energy landscape and modified atomic coordination. This asymmetry restricts the development of macroscopic kinetic models, as it requires considering a large number of flux balance equations. Consequently, metallic interfaces are often assumed to be in local thermodynamic equilibrium, ensuring chemical potential continuity. These assumptions, widely employed in macroscopic rate equations codes, are examined in this study. A methodology is proposed to reduce the number of equations needed for flux balance across metallic interfaces, eliminating the necessity of assuming local thermodynamic equilibrium or chemical potential continuity while enabling implementation in reaction diffusion codes. Given its relevance for nuclear fusion devices, we apply the approach to hydrogen diffusion at the tungsten/copper interface as a case study. The resulting reduced kinetic model accurately reproduces both the time to reach steady-state conditions and the hydrogen concentration profile.

Close

PrevNext

View figure in article

• Electronic structure of atoms & molecules
• Interstitials
• Kinetic theory
• Interfaces
• Solid-solid interfaces
• Density functional theory
• First-principles calculations