The newly designed PIMMS 2000 scanning mechanism allows for the examination of welds in straight pipe as well as in conical and pipe-to-elbow configurations, and can be used with various commercially available UT data acquisition systems. Appropriate UT transducers were selected to account for the austenitic grain structures in both homogeneous narrow gap welds and bimetallic nozzle to safe-end welds. For each weld type, several transducers were assembled into customized probe frames to minimize both mechanical manipulations and effective scanning time.

The qualification process for the UT examination procedure and the equipment was conducted according to the European methodology developed within ENIQ, and was assessed by an ad hoc Qualification Body. A technical justification document, involving both experimental evidence and physical reasoning, was prepared to demonstrate the capability of the UT system. Relevant examples from the open trials shall be presented to illustrate the excellent examination capability of the applied methods.

The first on-site intervention with the new system was performed in the KKB 2 unit, in September 1999, during the preservice inspection of the welds performed in the framework of the steam generator replacement: 14 main coolant piping welds were examined within a 90 hour time frame. Detailed interpretation of all UT examination data was finalised and reported less than 48 hours after completion of the last scanning sequence.