Theoretical study on the hydrogen distribution and diffusion at the PuO₂/α-Pu₂O₃ interface.

Area of Science:

• Materials Science
• Nuclear Materials Science
• Surface Science

Background:

• Interfaces between oxides of different valence states are critical in plutonium's surface oxide layer.
• Understanding hydrogen behavior at these interfaces is crucial for managing plutonium.

Purpose of the Study:

• To systematically investigate hydrogen distribution and diffusion at the PuO2/α-Pu2O3 interface.
• To elucidate the energetic favorability of hydrogen capture mechanisms at the interface.

Main Methods:

• Utilized a first-principles approach based on Density Functional Theory (DFT).
• Analyzed hydrogen interaction with oxygen atoms and oxygen vacancies (OVs) at the interface.

Main Results:

• Hydrogen is captured by both PuO2's oxygen atoms and α-Pu2O3's OVs, with OV capture being more energetically favorable.
• Diffusion barriers for hydrogen increase towards the interface from both PuO2 and α-Pu2O3 sides.
• Pre-existing hydrogen in OVs enhances further hydrogen capture.
• Interface formation slightly reduces OV capture ability in α-Pu2O3 but minimally affects hydrogen capture by PuO2 oxygen.

Conclusions:

• The formation of PuO2/α-Pu2O3 interfaces does not disrupt hydrogen behavior in either oxide.
• Differences in hydrogen behavior stem from altered atomic environments and ion valence states due to OVs.
• This research enhances understanding of hydrogen in plutonium oxides and aids corrosion prevention strategies.