Patent Number: 045487839
Section: summary

BACKGROUND OF INVENTION 1. Field of Invention This invention relates to a tool for servicing a nuclear reactor pressure vessel and specifically a tool for permitting closure of a normally submersed fluid outlet in a reactor pressure vessel. During a refueling and maintenance outage of a nuclear boiling water reactor, there is a need to facilitate isolation and drainage of the recirculation suction piping without draining the reactor vessel. In the past, maintenance and repair activity in the recirculation suction piping has required that the reactor vessel be drained to a level below the elevation of the side mounted recirculation outlet nozzle. Because the outlet nozzle is generally located at an elevation below the radioactive core, the entire core must be off loaded before the cooling fluid can be drained. This procedure is undesirable because it is costly, requires handling and storage of radioactive materials and is time consuming. 2. Description of the Prior Art In the past, valves in the outlet piping have been provided adjacent the outlet nozzle of the recirculation loop. However, such valves are in need of periodic maintenance which cannot be performed when such a valve is in use. Moreover, such valves have also been found to be subject to fluid leakage if not maintained. Heretofore, it has not been believed practical to provide means for closing off the submersed inlet to the first valve due to the relatively high pressures, close side wall tolerances of a reactor vessel and irregularities in the nozzle throat thought to prevent secure sealing and blockage. SUMMARY OF THE INVENTION According to the invention, an apparatus is provided for blocking the outlet nozzle coupled to a cooling fluid recirculation loop in a nuclear reactor pressure vessel for isolating the recirculation loop from the reactor which comprises a frusto-conical plug which mates the generally beveled seat of the outlet nozzle, gasket means mounted to the face portion of the plug which is sufficiently compliant to seal the plug against the possibly irregular seat surface, means for positioning the plug in confronting relation to the nozzle and means for remotely urging the plug into position abutting the nozzle. In specific embodiments, the gasket means is a double O-ring, each of which is remotely inflatable, and the urging means is a hydraulic jack with an end pad for abutting to a structural surface within the reactor pressure vessel which faces the nozzle. The apparatus is collapsible into a compact space which permits it to be lowered into the cooling fluid and deployed in the relatively tightly spaced region adjacent the nozzle. Cables are provided for suspending the apparatus, and fluid filled control lines are coupled to the apparatus for gasket inflation and jack extension functions. The invention will be better understood by reference to the following detailed description taken in connection with the accompanying drawings.