Development of Innovative Methods for Measuring Pipe Displacements in NPP Krško

Ensuring the structural integrity of high-energy piping systems is a critical requirement for the safe operation of nuclear power plants. This paper presents the design, imple-mentation, and three-year operational validation of a novel three-dimensional dis-placement monitoring system installed on the Steam Generator Blowdown pipeline of the Krško Nuclear Power Plant. The system was developed to confirm plant operating procedures will not cause excess dynamic displacements during operation. The measurement system configuration utilizes three non-collinear inductive dis-placement transducers (HBM WA/500 mm-L), mounted via miniature universal joints to a reference plate and to a defined observation point on the pipeline. The arrangement enables real-time monitoring of X, Y, and Z displacements within a spherical meas-urement volume of approximately 0.5 m. Data are continuously acquired by an HBM QuantumX MX840B amplifier and processed using CATMAN Easy-AP software through a fiber-optic communication link between the containment and control areas. The system has operated continuously for more than three years under elevated tem-perature and radiation conditions, confirming its reliability and robustness. The corre-lation of measured displacements with process parameters such as flow rate, pressure, and temperature provides valuable insight into transient events and contributes to predictive maintenance strategies. The presented methodology demonstrates a practical and radiation-tolerant approach for continuous structural monitoring of nuclear plant piping systems.