Partial canister mockup monitoring using fiber optic acoustic sensors and ultrasonic excitation

Metal storage canisters play an important role in the nuclear industry for the safe storage and transport of spent nuclear fuel and radioactive waste. These metal canisters are typically constructed from stainless steel, are structurally robust and are hermetically sealed and welded to ensure effective radiation shielding. They are widely used in dry cask storage systems, with thick reinforced concrete layers for additional protection and radiation shielding. The structural integrity of these canisters is crucial for preventing leaks, ensuring containment, and complying with stringent nuclear regulatory standards throughout their service life. This work presents a real-time nondestructive evaluation (NDE) of stainless-steel canisters using fiber-optic acoustic sensing system employing Lamb-wave excitation. The study utilizes a stainless-steel Partial Canister Mockup (PCM) with simulated flaws including circumferential and axial seam-welds. The dispersion characteristics of the guided Lamb waves and resulting acoustic profiles are investigated experimentally and numerically, achieving good consistency in terms of propagation and acoustic characteristics. Through excitation and monitoring of the fundamental anti-symmetric (Ao) wave-mode, we successfully demonstrate the detection of polished circumferential weld in the PCM. The experimental findings are validated using numerical simulations, showing strong agreement in wave arrival times and echo signatures. The fiber-optic sensing approach enables long-range, high-resolution monitoring in remote or inaccessible environments, providing a scalable solution for ensuring the long-term integrity and safety of spent nuclear fuel canisters.