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Primary water stress corrosion cracking (PWSCC) of Alloy 600 remains an important degradation phenomenon in PWRs. In particular, the susceptibility to the PWSCC initiation at 290°C is of recent interest because that is one of the typical temperatures of the primary water in contact with Alloy 600 which remains in PWRs. In this paper, oxide film formed on Alloy 600 in simulated primary water at 290°C was analyzed by X-ray absorption fine structure (XAFS) measurements at the Fe K-edge. For the preparation of the oxide film, Alloy 600 was immersed in simulated primary water with dissolved hydrogen (DH) concentration of 5 or 30 ml/kg-H2O. The near edge region of the XAFS suggested that the oxide film for 5 ml/kg-H2O DH had a larger Fe3+/Fe2+ ratio than for 30 ml/kg-H2O DH. Additionally, the extended region of the XAFS revealed that Fe3+ mainly occupied the octahedral site of the spinel oxide. Previous reports indicate that an Fe3+-rich spinel oxide is less defective and protective against PWSCC initiation. Therefore, our results suggest that the lower DH concentration (5 ml/kg-H2O) could potentially mitigate the susceptibility of Alloy 600 to the PWSCC initiation at 290°C. [ABSTRACT FROM AUTHOR]

X-ray absorption spectroscopy measurements were performed for the C K-edge of Pt nanoparticles on Ar+-irradiated carbon supports in order to elucidate the origin of improved catalyst performance after the introduction of vacancies into the carbon support. We observed a change in the electronic structure at the interface between the Pt nanoparticles and the carbon support after vacancy introduction, which is in good agreement with theoretical results. The results indicated that vacancy introduction resulted in a drastic change in the Pt–C interactions, which likely affected the d-band center of the Pt nanoparticles and led to the enhancement of the oxygen reduction reaction in catalysts. [ABSTRACT FROM AUTHOR]

The ion beam-induced defects in carbon supports for platinum (Pt) nanoparticles have been found to enhance the catalytic activity. Highly oriented pyrolytic graphite (HOPG) was irradiated with 380 keV argon ions (Ar + ), and Pt nanoparticles were then deposited on it by a radio frequency (rf) magnetron sputtering method. The Pt nanoparticle size on Ar + -irradiated HOPG and the carbon structure at the interface were investigated by transmission electron microscope (TEM) and Raman spectroscopy, respectively. The observed size of Pt nanoparticles on the irradiated HOPG was larger than that on the non-irradiated HOPG. Raman spectra indicated that vacancy-like defects were formed on the HOPG surface by Ar + -irradiation at the fluences between 1.0 × 10 12 and 1.0 × 10 13 ions/cm 2 , and sp 3 defects were induced by irradiation more than 5.0 × 10 13 ions/cm 2 . These defective structures on the HOPG would promote the Pt particle growth. [ABSTRACT FROM AUTHOR]