Localization of loose part impacts on the general 3D surface of the nuclear power plant coolant circuit components

A fundamental monitoring system in nuclear power plants is the so called loose part monitoring system (LPMS) detecting, localizing and specifying the loose parts (such as rivets, nuts, …) within the reactor coolant system. The loose parts could drift along the coolant flow and cause damage to the coolant system components, leading to power plant failure. One of the main tasks is a precise localization of the loose part impacts in order to identify the loose part and trace its motion in the system. Current localization methods are based on the time-of-arrival evaluation of mechanical waves travelling through mostly metal components from the impact place to the sensor positions. Diverse methods have been proposed, such as hyperbola or circle intersection methods, which are more or less analytical methods with a low grade of algorithmization, thus requiring a portion of manual effort. The proposed 3D localization method is flexible and efficient based on an algorithm for computing the shortest path along a general surface of components. This paper also presents a deeper insight into the mechanisms of the 3D localization method by analyzing its error and structural limitations. In the end, results obtained in an experiment on a real reactor vessel are presented.