Failure Analysis of CRDINiCr Butterfly Valves for Nuclear Power Plant Applications

Abstract

Corrosion-resistant iron with nickel and chromium (CRDINiCr) is often used in butterfly valves for flow control at nuclear power plants, where resistance to corrosion, oxidation, and wear is significant. In this study, a failure analysis of a CRDINiCr alloy butterfly valve was performed by combining morphology characterization and in situ elemental composition analysis of failure of various regions of the valve. Based on the testing and analysis conducted in this study, it was determined that the inspected valve body material exhibited several defects, including poor graphitization, porosity, and the presence of eutectic carbides. These imperfections compromised the required plasticity criteria, resulting in significant embrittlement of the material. Therefore, under the impact stresses applied during the pressure testing, these vulnerabilities facilitated rapid crack initiation and propagation. The presence of such defects significantly compromised the material’s resistance to fracture under dynamic loading conditions, underscoring the critical importance of stringent quality control in the production of such materials to ensure their reliability and performance in operational settings at nuclear power plants.