Patent Number: 054266807
Section: abstract

A method for removing a CRD with the position indicator probe in place. The method allows probe removal to be performed in a low-dose area, thereby effectively reducing the exposure received by the crew removing the probe to nearly zero. An electronic monitoring tool is provided for continuous CRD uncoupled monitoring during drive removal, using the position indicator probe to verify that the drive is uncoupled. The tool is mounted on the CRD removal equipment. The monitoring circuit is connected to selected position switches inside the position indicator probe. These switches are closed when a ring magnet on the drive piston is in proximity to the respective switch. The detected state of the switches can be used to determine whether the index tube/drive piston assembly is being extended as the CRD is lowered out of the housing. Indicator lights are activated to annunciate a coupled condition wherein the index tube is displacing relative to the piston tube as the CRD is lowered. In response to this annunciation, removal will be discontinued until the drive has been uncoupled.