Study of corrosion-related defects of zirconium alloys with slow positron beam

• Published in: Journal of nuclear materials Vol. 508; pp. 12 - 19
• Main Authors: Zhu, Zhejie, Yao, Meiyi, Shi, Jianjian, Yao, Chunlong, Lu, Eryang, Cao, Xingzhong, Wang, Baoyi, Wu, Yichu
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2018; Elsevier BV
• Subjects: Aqueous solutions; Corrosion; Corrosion rate; Corrosion tests; Deceleration; Defect; Defects; Diffusion layers; Diffusion rate; Oxidation; Oxidation rate; Oxygen; Oxygen atoms; Positron annihilation; Positron beams; Spectroscopy; Steam; Zircaloy; Zirconium; Zirconium alloys; Zirconium base alloys; Defect; Positron annihilation; Zircaloy; Corrosion
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2018.05.022

The corrosion behavior of Zr-4 and N5 alloy specimens corroded in 0.01 mol/L LiOH aqueous solution at 360 °C/18.6 MPa and in super heated steam at 400 °C/10.3 MPa for 1, 3 and 14 days were investigated by slow positron beam based Doppler broadening spectroscopy. Results showed that there was an evident interfacial layer with pre-existed vacancies and voids in uncorroded Zr-4 specimens, while in uncorroded N5 specimen, the interfacial defect layer can not be identified or a thin interfacial layer was only contained. When the specimens were corroded in super heated steam at 400 °C/10.3 MPa for a few days, the existence of the interface layer in the Zr-4 specimen would delay the diffusion rate of the oxygen atoms and decelerated the oxidation rate of the corrosion process. However, at very early stage of the corrosion, as Zr-4 and N5 specimens were corrded in 0.01 mol/L LiOH aqueous solution at 360 °C/18.6 MPa, the effect of Li+ accelerated the diffusion rate of the oxygen atoms, while the effect of the interface defect layer became a minor effect. •Slow positron beam is a sensitive tool to characterize the corroded layer.•Vacancy-type defects were produced at very early stage of the corrosion.•Pre-existed interface layer would delay corrosion process in super heated steam.•Effect of Li+ would accelerated corrosion process in LiOH aqueous solution.•A positron trapping model was suggested to explain corrosion mechanism.