Simulation of ultrasonic phased array inspection of CANDU pressure tubes

H Zhao, A Gachagan and G Dobie
Centre for Ultrasonic Engineering, University of Strathclyde, Glasgow, UK

Pressure tube inspection within CANDU nuclear reactors is a critical maintenance operation to identify and track the growth of defects and utilises a suite of six ultrasonic single-element transducers in the sensor head. Ultrasonic phased array technology is replacing single-element transducer configurations in many applications and this work investigates potential array configurations for a new sensor head design.

A hybrid simulation platform for ultrasonic phased array transducer inspection has been developed and experimentally validated, which combines the benefits of finite element modelling and analytical extrapolation. This approach has been used to study a range of practical phased array designs for the detection and sizing of two typical defect types using the total focusing method (TFM) imaging approach. The 10 MHz array demonstrated the highest resolution for depth measurement, while the 5 MHz array presented the strongest penetration performance for outer surface inspection. Moreover, a 32-element configuration, the largest aperture is this study, realised the most accurate defect size measurement. Based on the simulated TFM imaging results, a sensor head containing two orthogonal array transducers is recommended for the replacement of current single-element sensor configuration.

Keywords: hybrid simulation platform, ultrasonic inspection, phased array technology, total focusing method, pressure tube.