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On May 7, 2007, the 1D residual heat remov … On May 7, 2007, the 1D residual heat removal pump breaker, a 4 kV Merlin Gerin AMHG model breaker, tripped open while operations personnel attempted to place the pump in service using QCOP 1000-10, Torus Water Transfer to the Main Condenser Via the Condensate Demineralizers. The licensee developed and implemented a detailed troubleshooting plan and was able to identify that the breaker cubicle mechanism operated cell switch linkage assembly cam follower rod length was slightly out of tolerance. This caused the attached cam follower to come in contact and apply a load to the breakers spring discharge roller. Strike marks (minor wear marks) were made on the cam follower due to contact with the breakers spring discharge roller. The spring discharge roller then applied a pre-load to the breakers trip paddle which made the breaker very susceptible to tripping during breaker movement. The licensees extent of condition review for Unit 1 included an inspection of all 48 4 kV Merlin Gerin AMHG model breaker cubicles before completion of the 2007 refueling outage. In addition, the licensee was in the process of implementing an inspection schedule for Unit 2 and had inspected 10 of the 47 4 kV breaker cubicles that contained the 4 kV Merlin Gerin AMHG model breakers by the conclusion of the inspection period. The inspectors noted that the licensee found strike marks on the 4 kV breaker cubicles cam followers for the Unit 12 emergency diesel generator feed to Bus 13-1, the 1A core spray pump, the 1B residual heat removal pump, the 1D residual heat removal service water, and the 1C condensate booster pump. Once identified, the licensee implemented a design change to remove a small portion (approximately 1/4 inch) of the cam follower in the location where strike marks were being found. This was implemented for cam followers in all breaker cubicles that had been inspected and for those that were to be inspected. The removal of the material will allow a larger gap between the cam follower and breakers spring discharge roller to add margin and prevent the breaker from tripping due to the physical contact between components. The inspectors consider the licensees corrective actions appropriate to prevent recurrence regarding this failure mode. At the conclusion of the inspection period, the inspectors had several unanswered questions regarding the causes of and contributors to the 4 kV Merlin Gerin breakers failure to remain in the closed condition. Based on the unanswered questions, the inspectors determined that this item should be unresolved pending review of the licensees final apparent cause evaluation report (URI 05000254/2007003-06; 05000265/2007003-06).05000254/2007003-06; 05000265/2007003-06).
23:59:59, 30 June 2007 +
23:59:59, 30 June 2007 +
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R Langstaff +, T Bilik +, M Ring +, W Slawinski +, R Winter +, A Koonce +, K Streit +, D Melendez Colon +, Karla Stoedter +, Robert Orlikowski +, Robert Daley +, John Bozga +, Randy Baker +, Gregory Kolcum +, M Kurth +, R Ganser +, Z Falevitsa + and Barkera Koonce +
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00:32:18, 21 February 2018 +
R Langstaff +, T Bilik +, M Ring +, W Slawinski +, R Winter +, A Koonce +, K Streit +, D Melendez Colon +, Karla Stoedter +, Robert Orlikowski +, Robert Daley +, John Bozga +, Randy Baker +, Gregory Kolcum +, M Kurth +, R Ganser +, Z Falevitsa + and Barkera Koonce +
23:59:59, 30 June 2007 +