Reactor Pressure Vessel Nozzle Inner-Radius Examination

Abstract

Reactor pressure vessel nozzle inner radius (NIR) areas are identified as a specific target for ultrasound examination (UT) by many regulatory codes. This region represents a particularly challenging geometry to examine. Typically the examination is performed from inside the vessel with at least the upper internals removed. Normally the inspection is on the critical path so minimizing the schedule and vessel occupation time is important to the utilities outage planning and ultimate financial performance. Although some inspection vendors have traditional qualifications for this NIR examination under various codes, this paper addresses several advanced techniques have been developed to minimize the critical path inspection time. Technology advancements include: • Stereo-vision with laser reference for precise VT sizing of any observed indication • A Small 5 degree-of-freedom arm to precisely track a transducer set along the inner-radius surface for immersion ultrasonic examination • A simple nozzle-only tool with a passive mechanism to track the nozzle inner-radius surface for contact ultrasonic examination • Advanced software (3-D iMaV) coupled with a 5-axis robot to analyze and control transducer placements and coverage from the nozzle and shell outside (OD) The net result is a more efficient examination with shorter schedules and lower overall outage costs.