Validation 3D Ray Tracing for UT Examination of the Nozzle Inner Blend Region

Abstract

The inner blend regions of some pressure vessel nozzles are examined ultrasonically from the outside surface of the nozzle or of the vessel. Design and interpretation of these examinations are complicated because of multiple curvatures of the inside and outside surfaces and because the sound beam must be oriented properly with respect to the flaw in order for an echo to be detected at the transducer. In a previous paper [1], the software system (WARay3D) for designing and verifying wedges to be used in detecting flaws in the inner blend region of nozzles by corner reflection or by normal incidence was discussed; see Figure 1. The present paper describes experimental validation of 3D geometric modeling of nozzles and pressure vessels and raytracing to compute and display sound paths of UT inspections. A series of experiments was conducted at the EPRI NDE Center on a 20-inch diameter BWR nozzle specimen containing six artificially-induced flaws. WARay3D was used to determine specific search unit positions, beam angles and skew angles for manual ultrasonic detection of each flaw from both sides. All flaws were detected from both sides with high signal-to-noise ratio and with close correlation between the predicted and actual search unit locations and metal paths.