Characterizing stress corrosion cracking in stainless steel using nonlinear resonant ultrasound spectroscopy

Abstract

All Rights Reserved ii iii ABSTRACT Characterizing stress corrosion cracking in stainless steel using nonlinear resonant ultrasound spectroscopy Spent nuclear fuel rods are stored in stainless steel containers and may be stored for decades. In order prevent radiation leakage, the stainless steel structure must not be compromised. These containers are susceptible to stress corrosion cracking (SCC). Traditional nondestructive evaluation methods have been developed to detect open cracks but these cannot detect the closed portion of the crack that may extend further. Nonlinear Resonant Ultrasound Spectroscopy (NRUS) is used here to determine if it can be used to quantify a cumulative amount of SCC in a structure. To induce SCC in a timely manner, cylindrical, 304L stainless steel rods are immersed in a heated 42% magnesium chloride solution. A set of rods are removed one by one after different lengths of exposure to the hot magnesium chloride solution. NRUS measurements are then conducted on longitudinal modes in the rods. Rods exposed longer did indeed result in a larger resonance frequency shift, and therefore a larger nonlinear parameter, , in NRUS measurements. It is observed that α can be used to detect SCC before visible cracks appear on the rods. iv