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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 49426 | 10 October 2013 19:19:00 | 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | Incomplete Brazing of Contacts for Diesel Generator Control Relay | On August 5, 2013, annunciators were received for diesel generator (DG) 2B low lube oil inlet and outlet temperature. Investigation revealed that a control relay in motor control center cubicle 2EMXF F02D was not operating as expected. A work order was generated to replace the relay. While working the work order, a relay contact pad was found resting next to the relay. An inspection of the relay revealed that the contact pad came from the backside of the left movable contact. With the relay coil in the energized state and the contact pad missing, the relay contact would not engage. This prevented the lube oil heaters from energizing. The failed relay was sent to the Duke Energy Metallurgy Laboratory. It was observed that the gold brazing material was miniscule where the pad should have been attached. The laboratory observed the same brazing issue with the adjacent relay contact pads that were still attached on the failed relay. The material could barely be seen under the pads: it should have protruded out the edges for good brazing. It was determined that the overseas manufacturer of the relays had insufficiently bonded the relay contact pads to the movable contact arms for at least one known batch of relays. The failed relay is a Cutler-Hammer relay, Model Number 9575H3A000. The failed relay had been installed on July 30, 2013 to replace obsolete relay Model Number 9575H2612A. The replacement relay type was purchased by Duke Energy as a commercial grade item and dedicated for use in safety related applications. The failed relay batch number is 1111AF. Similar relays had been installed in the DG lube oil sump tank heater and the DG jacket water heater applications for DGs 2A and 2B. Duke Energy concluded that for these two installed applications, no substantial safety hazard existed, as DGs 2A and 2B were determined to be operable. (The heaters operate while the DGs are in standby to maintain required lube oil and jacket water temperature. Failure of these heaters to automatically start would be detected by alarms and the DGs could be started to maintain temperature. The heaters do not operate when the DGs are running.) However, because similar affected relays were in inventory, they theoretically could have been utilized in other safety related applications (even though they were not actually utilized in any other safety related applications). The most significant safety related applications where the affected relays could have been utilized were in circuitry associated with safety related ventilation system fans. Had they been utilized in these systems, a failure could have prevented the affected ventilation system fan from starting on an actuation signal. Catawba's evaluation that concluded that this issue could have resulted in a substantial safety hazard was completed on October 7, 2013. However, there was no actual impact to public health or safety. The required company officer notification was made on October 9, 2013. Catawba is the only Duke Energy site that had the affected relays. In addition, none of the affected relays were sold or transferred to other utilities by Duke Energy. Notifications will he made to the Catawba NRC Resident Inspector and to the required state and local agencies. The licensee will also be notifying North and South Carolina State, York, Gaston, and Mecklenburg Counties. |