Electrochemical approach to stress corrosion cracking of zirconium in boiling nitric acid solution

Yamamoto, Masahiro; Kato, Chiaki; Ishijima, Yasuhiro; Kano, Yoichi*; Ebina, Tetsunari*

no journal, , 

Zirconium had been used in nuclear fuel reprocessing plants, because of its superior corrosion resistance in nitric acid solution. However, stress corrosion cracking (SCC) was reported at highly concentrated nitric acid solution. In this report, electrochemical measurements were utilized to clarify the criteria of SCC occurrence of zirconium in boiling nitric acid solutions. For the relations between potentials and SCC susceptibilities, SCC behavior of zirconium was attributed to tarnish rupture model. The observations of fractured surfaces and cross sections of cracks also supported the validity of the model. SCC susceptibility of zirconium was mainly affected by the thick oxide film formation at the surface. In our whole observations, SCC of zirconium occurred only at transpassive regions. When a reprocessing plant made of zirconium operates in the passivity state, there is no SCC occurrence in the equipment.