ENS 52254
ENS Event | |
|---|---|
06:21 Sep 21, 2016 | |
| Title | Discharge Check Valve Failure to Seat Causes Trip of Component Cooling Water Pump |
| Event Description | At 0221 [EDT] on 9/21/16, Operators at Unit 2 Secured the 21 Component Cooling Water (CCW) Pump for planned maintenance while 22 and 23 CCW pumps were in operation. When the 21 pump was secured, the discharge check valve failed to seat. This resulted in a low system pressure and reverse rotation of the 21 CCW Pump due to the discharge of the 22 and 23 CCW pumps to a common header. When system pressure dropped below 107 psig the 21 CCW pump received an auto start signal. Due to the reverse rotation, the 21 CCW pump tripped on overcurrent. Reactor Operators directed Field Operators to manually shut the 21 CCW Pump discharge valve. The 21 CCW pump Discharge Valve was closed at 0223 [EDT]. This action was successful in stopping the reverse flow and restoring system parameters. During this two minute period the CCW system was declared inoperable and LCO 3.0.3 was entered. Unit 2 exited LCO 3.0.3 at 0223 [EDT] after observing system pressure and flow return to normal. The declaration of inoperability on the CCW system is considered a Loss of Safety Function for purposes of reporting under 50.72(b)(3)(v)(D). There was no reduction in power while in LCO 3.0.3 and no other issues arose.
The Licensee notified the NRC Resident Inspector. The Licensee notified the Public Service Commission.
Indian Point Unit 2 is retracting the 8-hour non-emergency notification made on September 21, 2016, at 0920 EDT (EN#52254). The notification on September 21, 2016, reported a safety system functional failure (SSFF) as a result of declaring the Component Cooling Water System (CCW) inoperable due to failure of the 21 CCW pump discharge check valve (761C) to close. This condition was discovered during planned maintenance after securing the 21 CCW pump while the 22 and 23 CCW pumps were in operation. When the 21 CCW pump was secured, the discharge check valve failed to seat. This resulted in a low system pressure and reverse rotation of the 21 CCW pump due to the discharge of the 22 and 23 CCW pumps to a common header. Condition was reported as a safety system functional failure (SSFF) under 10 CFR 50.72(b)(3)(v)(D). After further investigation of the condition, a revised calculation was prepared for the CCW hydraulic model which is used to analyze CCW system performance for normal and DBA [design basis accident] modes of operation and documented in a calculation. The new calculation included the as-found condition of the 21 CCW pump discharge check valve failure to seat. Based on the results of the new calculation, the CCW system is capable of performing its design basis heat removal function during a design basis accident. Calculated flow rates with CCW aligned for Post-LOCA recirculation demonstrates that with failed open check valve 761C, the 22 CCW pump and 23 CCW pump have adequate NPSH margin, are operating below analyzed pump run out and deliver flow to the CCW system that is significantly greater than the flow required for post-LOCA recirculation. Therefore the CCW system was operable and a safety system functional failure (SSFF) did not occur as a result of failed open 21 CCW pump discharge check valve 761C. The licensee has notified the NRC Resident Inspector and will be notifying the New York Public Service Commission. Notified R1DO (Bickett). |
| Where | |
|---|---|
Indian Point  New York (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+2.98 h0.124 days <br />0.0177 weeks <br />0.00408 months <br />) | |
| Opened: | Chris Hassenbein 09:20 Sep 21, 2016 |
| NRC Officer: | Jeff Herrera |
| Last Updated: | Nov 18, 2016 |
| 52254 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |