Headquarters Daily Report OCTOBER 24, 1996 *************************************************************************** REPORT NEGATIVE NO INPUT ATTACHED INPUT RECEIVED RECEIVED HEADQUARTERS û REGION I û REGION II û REGION III û REGION IV û PRIORITY ATTENTION REQUIRED MORNING REPORT - HEADQUARTERS OCTOBER 24, 1996 MR Number: H-96-0079 NRR DAILY REPORT ITEM SIGNIFICANT EVENTS Subject: FAILURE OF GENERAL ELECTRIC MAGNE-BLAST CIRCUIT BREAKER AT DRESDEN 3 CAUSED BY GREASE HARDENING On October 15, 1996, the NRR/AEOD/RES Events Assessment Panel classified the June 11, 1996, low pressure coolant injection circuit breaker failure at Dresden 3 to be a Significant Event for the NRC Performance Indicator Program. The basis for classifying this event as a Significant Event is the evident deficiency in the licensee maintenance program. On June 11, 1996, at Dresden 3, a 4.16-kV GE Magne-Blast circuit breaker that supplies power to a low-pressure coolant injection pump motor failed to open on demand from the control room following a surveillance run of the pump. Examination of the failed breaker showed hardened grease in the breaker mechanism. In subsequent testing of four similar spare breakers, all tripped at required low voltage conditions. However, two of the breakers showed the potential for unreliable operation because their trip latch roller bearings did not freely rotate. The cause was hardened grease. During bench testing of breakers pulled from the cubicles to date, two additional breakers failed to trip on required low voltage. Both breakers exhibited hardened grease conditions in trip latch roller bearings. Only one of the three failed bearings to date have shown the presence of fiber particles. The licensee identified 23 safety-related breakers in Dresden 3 as susceptible to this failure mechanism. On June 20, 1996, the licensee initiated a shutdown of Dresden 3 and contracted with GE Nuclear Energy to completely overhaul each of these 23 breakers and the similar ones in Dresden 2. In 1989, during the NRC maintenance team inspection at Dresden, the team found a lack of lubrication of these same breakers. At that time, the licensee instituted a preventive maintenance program as a corrective measure. Subsequent NRC review of that program showed that the licensee had not fully implemented recommendations of the manufacturer, GE Specialty Breaker Plant (SBP). The GE SBP instruction book applicable to the horizontal-drawout Magne-Blast circuit breakers used at Dresden (GEI-88771D), a similar book applicable to vertical-lift breakers used elsewhere (GEK-7320F), and GE Service Advice Letter (SAL) 354.1, dated August 25, 1995, recommend that these breakers be lubricated once every 2 years. The licensee had planned to implement the SAL recommendation during the next refueling outage, but that has now been rescheduled for March 1997. The licensee had been using a six-year maintenance period and had not maintained (cleaned and lubricated) the failed breaker for six and a half years. The following factors may have contributed to the aging and hardening of grease over this protracted maintenance period: (1) Contamination of grease by an HEADQUARTERS MORNING REPORT PAGE 2 OCTOBER 24, 1996 MR Number: H-96-0079 (cont.) aerosol degreaser during maintenance in 1989, (2) prevention of the light-weight lubricating oil applied during maintenance in 1989 from reaching internal bearing surfaces and refreshing the grease by a preceding application of a light coating of grease, not required by the vendor, to external surfaces, (3) premature aging of grease from cubicle heaters, and (4) presence of fibrous material in the one affected bearing. The NRC review of maintenance of Magne-Blast breakers at component and system levels with reference to the maintenance rule at 10 CFR 50.65 indicates that the breaker involved in this event or the system containing it should be monitored and maintained under section (a)(1). In general, however, licensees are not necessarily expected to monitor performance of Magne-Blast breakers at the component level but would be expected to monitor performance at the train or system or plant level, depending on risk significance. CONTACT: V. Hodge, NRR/DRPM/PECB (301) 415-1861 _