Understanding the interface interaction between U₃Si₂ fuel and SiC cladding

Area of Science:

• Nuclear Engineering
• Materials Science
• Computational Materials Science

Background:

• Advanced accident-tolerant fuels are crucial for enhancing nuclear reactor safety.
• Triuranium disilicide (U3Si2) and silicon carbide (SiC) composites are promising candidates for next-generation nuclear fuel cladding.
• Understanding the chemical compatibility between U3Si2 fuel and SiC cladding is essential for operational and accident scenario assessments.

Purpose of the Study:

• To comprehensively investigate the chemical interactions between U3Si2 fuel and SiC cladding.
• To determine the thermodynamic driving forces for interfacial phase formation and defect generation.
• To validate computational predictions with experimental diffusion couple results.

Main Methods:

• Density functional theory (DFT) calculations were employed to determine reaction energies and defect formation energies.
• Diffusion couple experiments were conducted to observe interfacial reactions between U3Si2 and SiC.
• Thermodynamic analysis was used to assess the stability of the fuel-cladding system.

Main Results:

• DFT calculations predicted the potential formation of triuranium pentasilicide (U3Si5), uranium carbide (UC), U20Si16C3, and uranium silicide (USi) phases at the interface.
• Calculations revealed a thermodynamic driving force for defect generation in both U3Si2 and SiC when interfacial phases form.
• Diffusion experiments confirmed restricted formation of U3Si5, UC, and U20Si16C3/USi, indicating limited continuous interfacial reactions.

Conclusions:

• The U3Si2 and SiC fuel-cladding system exhibits substantial stability due to a diminishing driving force for defect formation.
• The limited interfacial reactions observed suggest a robust performance under operational and potential accident conditions.
• This study demonstrates the potential of U3Si2/SiC as an accident-tolerant fuel system for light water reactors.