Online monitoring of zirconium alloy components of pressurised heavy water reactors by advanced NDE techniques

A brief overview of the international and national scenario on quality management of zircaloy components, used in PHWRs has been presented. The work carried out at IGCAR on the development of intelligent Eddy current imaging scheme for quantitative defect characterisation and the use of ultrasonic velocity measurements for detection of intermetallics has been highlighted. The results of acoustic emission and thermographic studies during end cap welding of nuclear fuel elements carried out as part of the DST project have been presented. AE analysis could clearly reveal the formation of defects during the welding stage itself. Thus AE is one of the most suited technique for online monitoring of end cap welding. In case of thermal imaging, good welds were characterised by uniform isothermal widths and symmetrical isothermal patterns while bad welds were characterised by uneven isothermal widths and patterns. Thermography helped in the location of weld defects