Investigation of ultrasonic inspection of the inner radius of a nozzle

Various ultrasonic inspection techniques have been developed and are used for inspection of the nozzles of nuclear power plant vessels. However, it seems that radial/axial cracks in the inner part of the nozzles can still remain undetectable due to the complex geometry of the nozzle. The objective of this work was to determine the positions and orientations of the transducers and the incident angles needed to inspect the inner radius of a nozzle and to estimate which part of the inner radius can be inspected. The investigations were carried out using modelling with the CIVA software and by a model developed by us in Matlab. It is shown that most of the inner radius zone can be inspected using the proposed set of transducers. The positions of the transducers and the parameters suitable for the detection of defects in the inner radius zone were determined. It is necessary to underline that the wedges for the transducers should be different as different incident angles are required. The investigations demonstrated that a certain zone exists in the inner radius that cannot be inspected using a conventional pulse-echo technique.