[en] Some of the techniques considered for in-service inspection of SGHWR pressure tubes, to determine the extent of any service-induced defects are considered and the development work is described. Current practice is to use a pitch and catch ultrasonic technique examining from the tube bore. The probes can be switched to pulse-echo to complement the basic information if necessary. Proving trials have demonstrated a capability to detect longitudinal defects of 0.5mm or greater depth. Sizing of such defects can be made up to 2.5mm depth by reference to calibrations obtained on spark machined slots. Further work is in progress to consolidate the data on other forms of defect and to optimise probe size, frequency and geometry. (UK)