Simulation and analysis of full-coverage ultrasonic signal detection for reinforcement part of nuclear reactor pressure vessel outlet nozzle

Pressurized water reactors (PWRs) are the predominant type of nuclear power plant globally, with their reactor pressure vessels (RPVs) subject to stringent in-service inspection (ISI) requirements as mandated by regulatory standards. However, the complex curved surface of the reinforcement part presents challenges for ultrasonic testing in the outlet nozzle-to-shell weld areas, resulting in inaccessible zones that lack practical quantitative analysis methods for volume coverage. This study systematically parameterized the geometric features of the outlet nozzle reinforcement part, including the cone, fillet, and ellipse. It introduced seven categories of ultrasonic beam tangent segmentation algorithms based on spatial curves. Using Pro/E software, we developed a 3D ultrasonic beamline model of inaccessible zones and validated its accuracy against two-dimensional data obtained from AutoCAD. Building on this foundation, a fully parametric simulation model and discrete volume data were employed to plot the continuous curves of inaccessible zones’ volume on the side of the typical outlet nozzle reinforcement part as a function of ultrasonic incidence angles, elucidating the nonlinear, multi-stage superimposed impact of complex surface characteristics on the volume of inaccessible zones. This research provides vital theoretical support and a methodological basis for optimizing ultrasonic testing processes and quantitative evaluation of volume coverage in nozzle areas with complex surfaces, particularly saddle-like profiles.