Optimization of TOFD Detection for Thick-Walled Nuclear Pressure Vessel with Inner Surface Defect

The 20° probe is proposed in order to optimize the TOFD detection. Acoustic wave characteristics, detection signal and image feature of 20° probe are analyzed. The optimal frequency is determined by comparing 2.25MHz and 5MHz. Through TOFD detection of artificial inner surface defect, the optimum detections are demonstrated, which are fit for detecting thick-walled nuclear pressure vessel with inner surface defect. The experimental results show that:（a） for thick-walled nuclear pressure vessel with inner surface detect, 20° probe and 5MHz frequency are optimization.（b） By this optimization detection, artificial inner surface defect with height of 2mm can be effectively distinguished in nuclear pressure vessel with thickness of 120mm.