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| Entered date | Event description | |
|---|---|---|
| ENS 47361 | 20 October 2011 14:32:00 | At 08:00 CDT on 10/20/2011 Essential Chilled Water Loop B was declared inoperable while turbine driven Emergency Feedwater Pump AB was out of service for planned maintenance. Operability of Essential Chilled Water Loop B was restored at 08:50. During this time period, the application of cascading technical specifications rendered motor driven Emergency Feedwater Pump B inoperable. The remaining operable Emergency Feedwater Pump A is a design rated 50 percent pump; therefore, this event could have prevented fulfillment of the Residual Heat Removal safety function. Offsite power and Train A safety related equipment and systems were verified operable. Essential Chilled Water Loop B was declared inoperable because Essential Chiller B failed to automatically restart from a load recycle. The shift crew took action to align Essential Chiller AB to restore operability to Essential Chilled Water Loop B. The cause for the failure of Essential Chiller B is not yet known. Restoration of operability to Essential Chilled Water Loop B concurrently restored operability to Emergency Feedwater Pump B. No plant transient or safety system actuations occurred. Plant operation continues stable at 100 percent power. The licensee notified the NRC Resident Inspector. |