This 60-day report as allowed by
10 CFR 50.73 (a)(2)(iv)(A) to describe an invalid actuation of a specified system, specifically the
Auxiliary Feedwater System (
AFW). This event involved an invalid actuation of the Motor Driven
Auxiliary Feedwater pump 2B during routine Unit 2 Auxiliary Safeguards Testing on 8/8/06. The system was properly aligned and did inject water into
Steam Generators 2C and 2D as designed to perform a complete actuation of
AFW pump 2B.
The motor driven auxiliary feedwater pumps will automatically start and provide the minimum required feedwater flow within one minute following any of these conditions:
1. Two out of four low-low level alarms in any one of the four steam generators.
2. Loss of both main feedwater pumps
3. Initiation of safety injection signal
4. Loss of station normal auxiliary electric power
5. AMSAC signal
Since none of the five auto-start parameters were met at the time of the system actuation the signal was determined to be invalid.
Engineering reviewed the CA Pump Start circuit to determine which equipment failures could cause the switchgear breaker for the AFW Pump 2B to close and start the pump. These included reviewing sequencer start signals, manual pushbuttons, and associated contacts and breakers. The failure of the fluke meter used during the testing was considered, also. In addition, the Operations Test Group performed an analysis of the human performance aspects of this testing. Based on these investigations potential equipment failures have been ruled out and based on the correspondence in time with when the inadvertent start occurred and when the meter reading was taken, it is believed that the inadvertent start is due to an anomaly with the Fluke 189 meter or issues when taking the measurement. The measurement is taken across an energized circuit, which can be susceptible to inadvertent actuations. The test procedure has been revised to open links on the circuit to prevent inadvertent operation.
The licensee notified the NRC Resident Inspector.
