A REMOTE STEAM GENERATOR GIRTH-WELD INSPECTION AND REPAIR SYSTEM

PRESENTLY, 18 PRESSURIZED WATER REACTOR (PWR) STEAM GENERATORS IN SERVICE IN THE U.S. HAVE CRACKS IDENTIFIED IN THE GIRTH WELDS. EXPERTS BELIEVE THAT THIS NUMBER WILL GROWMUCH LARGER. THE TWO STEAM GENERATOR MODELS THAT HAVE EXPERIENCED GIRTH-WELD CRACKING THUS FAR, THE WESTINGHOUSE MODEL 44 AND WESTINGHOUSE MODEL 51, ARE IN WIDESPREAD SERVICE. (MORE THAN 100 OPERATE IN THE U.S. AND CLOSE TO 160 OPERATE OUTSIDE THE U.S.). INSPECTION AND REPAIR PROGRAMS ARE VERY COSTLY TO U.S. UTILITIES. A RECENTLY COMPLETED INSPECTION AND REPAIR PROGRAM, WHICH INVOLVED ONLYGRINDING TO REMOVE SURFACE CRACKS AND NO WELD REPAIR, COST THE UTILITY ABOUT $5 MILLION, RESULTED IN ABOUT 250 PERSON-REM OF EXPOSURE, AND SUBSTANTIALLY INCREASED THE LENGTH OF THE OUTAGE BEYOND THAT FOR INSPECTION. A ROBOTIC SYSTEM CAPABLE OF PERFORMING ANY OR ALL OF THESE INSPECTION AND REPAIR TASKS CAN GREATLY BENEFIT THE UTILITIES. EXISTING ROBOTIC SYSTEMS ARE INCAPABLE OF ADDRESSING THIS NEED BECAUSE OF THE SEVERE LIMITATIONS IMPOSED BY THE RESTRICTED SPACE, COMPLEX GEOMETRY, AND UNSTRUCTURED ENVIRONMENT IN WHICH THE SYSTEM MUST FUNCTION. THIS PHASE IPROJECT IS DEVELOPING A CONCEPTUAL DESIGN FOR A SYSTEM CAPABLE OF REMOTELY PERFORMING (1) VISUAL INSPECTION, (2) WELD BUFFING, (3) ULTRASONIC AND DYE PENETRANT TESTING OF THE STEAM GENERATOR GIRTH WELD AND THE HEAT-AFFECTED ZONES, AND (4) LIGHT GRINDING TO REMOVE SURFACE FLAWS.