Apparatus and method for inspecting a control rod drive mechanism

Abstract

Apparatus and method for inspecting a tubular member for degradation, which tubular member may be a control rod drive mechanism (CRDM) penetration tube of the kind typically found in nuclear power reactor pressure vessels. The CRDM penetration tube includes a thermal sleeve concentrically disposed therein, the sleeve being radially rotatable and axially translatable within the tube. However, the sleeve may be nonhomogeneous, which nonhomogeneity could undesirably mask the inspection signal as the inspection sensor is radially and axially moved in order to inspect the tube. The apparatus includes a support body sized to be disposed in the sleeve, an expandable bladder connected to the support body to engage the sleeve for securing the support body to the sleeve, one or more sensors connected to the support body for sensing the degradation in the tube, and a rotator connected to the support body for simultaneously rotating the support body, the bladder, the sensor and the sleeve in the tube to radially scan the tube. A pusher/puller mechanism is also provided, the pusher/pusher mechanism being connected to the support body for simultaneously translating the support body, the bladder, the sensor and the sleeve to axially scan the tube. As the support body is rotated and translated, the sleeve is stationary with respect to the sensor because the bladder secures the sleeve to the support body; thus, as the support body, and the sensor connected thereto are rotated and translated, the sleeve will be rotated and translated to a like extent. In this manner the material properties of the sleeve are radially and axially invariant relative to the sensor, for obtaining a more precise inspection of the tube.