Abstract
Synchrotron high-energy XRD measurements and ab-initio DFT calculations were employed to investigate microstructural degradation of copper upon exposure to sulfide-containing anoxic groundwater simulating nuclear waste repository. After two-month exposure, the high-energy XRD measurements revealed heterogeneous lattice deformation in the microstructure and lattice expansion in near-surface regions. The DFT calculations show that sulfur promotes hydrogen adsorption on copper. Water causes surface reconstruction and promotes hydrogen insertion into the microstructure, occurring via interstitial sites next to vacancies leading to lattice dilation and metal bond weakening. Hydrogen infusion in the presence of sulfur caused lattice degradation, indicating a risk for H-induced cracking.
Highlights
A large amount of spent fuel is produced every year from commercial nuclear power plants, 1% of the nuclear waste is highly radioactive and its safe disposal is as important as nuclear safety
We report synchrotron high-energy X-ray diffraction (HEXRD) measurements in transmission mode and ab-initio density functional theory (DFT) calculations to investigate the effect of exposure to simu lated anoxic groundwater containing sulfide on the lattice degradation of copper
The Cu surface was modelled by a six-layer slab orien tated at 110, which contains 36 Cu atoms, which is commonly used in DFT calculations of Cu
Summary
A large amount of spent fuel is produced every year from commercial nuclear power plants, 1% of the nuclear waste is highly radioactive and its safe disposal is as important as nuclear safety. There is a need to gain a deep understanding of the role of sulphur and hydrogen in stress corrosion cracking (SCC) and hydrogen embrittlement of copper in the ground water containing sulphide. To achieve an atomistic understanding of the mechanism of the SCC and hydrogen embrittlement, it is necessary to study corrosion-induced lattice degra dation of copper, the role of sulfur and hydrogen. To our knowledge, this has not been done before. DFT calculations of Cu-S-H sys tems ( in water) were carried out to provide an atomistic under standing of the surface adsorption, dissociation, and infusion of hydrogen that lead to degradation of the Cu lattice
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