FBG-based methodology for in-situ crack growth characterization of electrical penetration assembly in nuclear power...

Cracks are critical defects in glass-metal electrical penetration assemblies (G-M EPA), compromising mechanical strength and hermeticity in nuclear power plants. A feasible real-time crack growth detection method utilizing an embedded fiber sensing technique was presented in this research. The glass-metal sealing model with embedded FBG sensors was investigated to evaluate the crack growth behavior under harsh environments. The FBG spectrum was distorted because the crack caused the local strain to vary dramatically, and what we believe to be two novel spectrum parameters-reflectivity ratio Rc(λ)/Ru(λ) and cross-correlation C_R. The experimental and numerical results demonstrated that the distorted spectrum could be applied as a practical indicator to quantify crack growth in G-M EPA. In addition, an effective global uniformly distributed FBG array configuration method was proposed to monitor all potential cracks in the entire region of G-M EPA. This technique aims to enhance the accuracy and reliability of monitoring systems in nuclear engineering applications.