Patent Number: 061378534
Section: abstract

A method and an apparatus for ultrasonically inspecting the welds which attach the differential pressure and liquid poison nozzles to the bottom head of the reactor pressure vessel in a boiling water reactor. The scanning apparatus is seated on the upper taper of the nozzle outer tube and incorporates a stationary frame having a cutaway section which allows installation from the side. The apparatus has vertical and circumferential positioning mechanisms which are operated remotely to scan an ultrasonic transducer package over the circumferential welds and heat-affected zones thereof. The rotating frame has a transducer carriage mounted thereon which is vertically displaceable relative to the rotating frame. The vertical and angular motion motors can be controlled together to provide the desired path for the ultrasonic transducer around the stub tube. The tool also includes a vessel contour follower which follows the contour of the inclined surfaces of the reactor pressure vessel bottom head. The vessel contour follower is linked to the ultrasonic transducer to ensure that the transducer follows the contour of the weld, in position and angle.