A STEAM GENERATOR UPPER BUNDLE INTERTUBE INSPECTION AND MAINTENANCE ROBOT

STEAM GENERATOR TUBE FOULING IS DEGRADING THE PERFORMANCE OF ONE IN THREE U.S. PRESSURIZED WATER REACTORS. THE SEVERITY OF THE TUBE FOULING AND THE NUMBER OF PLANTS AFFECTED ARE EXPECTED TO INCREASE AS THE PLANTS AGE. AS THEY BUILD UP ON TUBE SURFACES, CORROSION PRODUCTS ACT AS AN INSULATOR AND REDUCE HEAT TRANSFER IN THE STEAM GENERATOR. FOR EXAMPLE, ONE UTILITY HAS EXPERIENCED A 12 MW LOSS IN ELECTRICAL OUTPUT. FURTHERMORE, THE MAGNITUDE OF THE LOSS IS INCREASING BY ABOUT 4 MW PER YEAR. OVER THE NEXT 10 YEARS, THE LOST POWER FROM THIS ONE PLANT WILL COST MORE THAN $36 MILLION. CORROSION PRODUCTS FROM THE FEEDWATER SYSTEM COLLECT ON TUBE SUPPORT PLATES AND TUBE SURFACES IN THE STEAM GENERATOR, ACCELERATING TUBE CORROSION AND REDUCING HEAT TRANSFER. CURRENTLY, SLUDGE ACCUMULATION IN THE TUBESHEET REGION CAN BE REMOVED BECAUSE ACCESS PORTS ARE AVAILABLE. HOWEVER, NO MEANS EXIST TO ACCESS THE TIGHT INTERTUBE REGIONS IN THE UPPER PORTIONS OF THE STEAM GENERATOR TO REMOVE SLUDGE DEPOSITS. SLUDGE REMOVAL FROM ALL AREAS OF THE STEAM GENERATOR WILL INCREASE THE LIFE OF THE STEAM GENERATORS. IN THIS PROJECT, THE PHASE I EFFORT INVESTIGATES NOVEL WAYS TO ACCESS THE SEVERELY RESTRICTED INTERTUBE AREAS IN THE UPPER TUBE BUNDLE OF STEAM GENERATORS AND REMOVE SLUDGE DEPOSITS. ACCESS INTO THIS REGION IS POSSIBLE THROUGH A TUBESHEET HANDHOLE AND FLOW SLOTS IN THE TUBE SUPPORT PLATES. ONCE AT THE UPPER REGIONS, INSPECTION AND MAINTENANCE EQUIPMENT MUST BE INSERTED THROUGH THE TIGHT TUBE GAPS, REQUIRING DEVELOPMENT OF INNOVATIVE TECHNOLOGY AND MEANS OF LOCOMOTION.