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| Entered date | Event description | |
|---|---|---|
| ENS 53253 | 10 March 2018 13:54:00 | HPCI (High Pressure Coolant Injection) was removed from service (unplanned) on 3/10/2018 at time 0709 (CST) by closing HPCI-MO-15, STEAM SUPPLY INBOARD ISOLATION. The inboard steam supply isolation valve is inside Primary Containment. The steam supply valve was closed in an effort to isolate (unidentified) leakage to Primary Containment from a suspected packing leak from HPCI-MO-15. After closing the HPCI-MO-15, Reactor Coolant System Leakage parameters returned to within Technical Specification (TS) LCO (Limiting Condition of Operations) 3.4.4 limits. Entered into Technical Specification LCO 3.5.1 Condition C - HPCI System Inoperable. Required Actions for Condition 'C' are to verify by administrative means RCIC (Reactor Core Isolation Cooling) System is operable within 1 hour and restore HPCI System to operable status within 14 days. RCIC was verified operable by administrative means concurrent with declaration of HPCI inoperable. Normal plant shutdown activities are being planned (for 03/11/2018 at 1200 CDT) to support entry into Primary Containment to initiate any necessary repairs. HPCI is a single train safety system. This report is submitted as a condition that at time of discovery could prevent the fulfillment of the safety function of an SSC (System, Structure, or Component) needed to mitigate the consequences of an accident. This condition has been entered into the CNS (Cooper Nuclear Station) Corrective Action Program. CR-CNS-2018-01346 LCO 3.4.4 was entered during unplanned maintenance of the HPCI system. When the HPCI-MO-15 was cycled from closed to open, unidentified leakage in the containment increased above 2 gallons per minute (gpm) in less than a 24 hour period. Also, total unidentified leakage exceeded 5 gpm. The licensee closed the HPCI-MO-15 valve resulting in a decrease in unidentified leakage below TS shutdown limit. The NRC Resident Inspector was notified. |