Historically, United States (US) nuclear power plant inspections of the reactor vessel bottom-mounted-instrument (BMI) penetrations have been limited to visual verification via a combination of walk-downs and pressure tests. However in France, more than 18 UT and weld-surface VT campaigns had been performed to inspect the BMI penetration nozzles and welds since 1992 with no observed failures through 2002. In April 2003, South Texas Project Unit 1 discovered apparent leakage from two nozzles during a bare-metal examination. Based on the French inspection experience, Framatome ANP was selected for inspection and repair services to address the leaking nozzles. Inspection activities included ultrasonic examination (UT) of the tube, enhanced visual test (VT) and eddy current testing (ECT) of the J-groove weld, bobbin ECT and profilometry of the tube ID, helium leak test, phased-array UT, borescopic VT, and boat-sample removal with destructive metallurgical analysis. Repair activities included sealing the top portion of the penetration, cutting out the old nozzles, and welding in new nozzles. This presentation discusses BMI inspection and repair technology focused particularly on the South Texas Project experience.

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