On Active Diagnostics Method for Assessment of Technical Condition of Nuclear Facility Components

Abstract

An active diagnostics method intended for identification of technical condition of pipelines and other components of nuclear facilities is considered. This method is based on detection of structural anomalies in components by observing changes in static and dynamic behavior of component structure which are registered during special tests. Static behavior is analyzed as response to time-independent mechanical or temperature loading. Dynamic behavior can be analyzed through studying fields of vibration displacements, velocities and accelerations when sinusoidal mechanical oscillations are generated. Structural anomalies can be presented as deviations of stiffness, geometry and inertial parameters from their nominal (design) values. Impact of these deviations on structural response may be bigger in spatial scale than anomaly dimensions. Therefore there is a theoretical possibility to detect structural anomaly in the areas which are inaccessible for direct observing by registration of structure response parameters in observable areas. The paper describes the theoretically basis and results of the experimental and numerical studies on detection of a hidden crack-like anomaly in pipe components. Experimental study of dynamic and static response is carried out by coherent optical methods, and numerical analysis — by finite element method. Theoretical and experimental data have a good agreement and allow to reveal anomaly position and to estimate roughly its dimensions. Application of the method to welded joint in pipe specimen which corresponds to real nuclear facility pipeline is under investigation now.