ENS 40890
ENS Event | |
|---|---|
03:20 Jul 22, 2004 | |
| Title | Technical Specification Required Shutdown: Non-Vital Component Cooling Water Leak Inside Containment |
| Event Description | On July 21, 2004, with Unit 1 operating in Mode 1 (Power Operation) at approximately 100 percent power, a non-vital component cooling water (CCW) leak was identified inside containment. It was conservatively concluded that the leak could potentially disable both vital CCW loops, and thus the LCO for Technical Specification (TS) 3.7.7 "Vital CCW System" would not be met. Given there is no associated action for both vital loops inoperable, operators entered TS 3.0.3 at 1900 PDT, a unit shutdown was commenced at 20:20 PDT.
The leak was identified at a cracked weld to the RCP 1-3 lube oil cooler, and is estimated at approximately 0.1 gallons per minute. While the leak is in the non-vital CCW loop and is stable, not currently a challenge to the function of the CCW system, and is not damaging plant equipment, based on the potential for the condition to rapidly degrade under loading such as a seismic event, operators applied TS 3.7.7. It is planned to place Unit 1 in Mode 3 (Hot Standby), restore both vital CCW loops to OPERABLE status by isolating the CCW supply to the RCP 1-3 lube oil cooler, and exit TS 3.0.3. The unit will be returned to service following repair of the cracked weld. Reactor Coolant Pump (RCP) 1-3 CCW pipe diameter is 3 inches. Leak was first noticed by increasing containment sump level. Personnel entered containment and discovered the cracked weld on the 3 inch CCW piping. The maximum leak if the CCW pipe completely shared off would be greater than 200 gallons per minute (CCW system can handle a maximum leak rate of approximately 200 gallons per minute). The other three Reactor Coolant Pump CCW lube oil cooling piping were checked and no leaks were discovered. All emergency core cooling systems and the emergency diesel generators are fully operable if needed. The electrical grid is also stable. At 2357 EDT Unit 1 was at a power level of 50% and decreasing. The NRC Resident Inspector was notified of this event by the licensee. |
| Where | |
|---|---|
Diablo Canyon  California (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | |
| LER: | 05000275/LER-2004-002 |
| Time - Person (Reporting Time:+-2.38 h-0.0992 days <br />-0.0142 weeks <br />-0.00326 months <br />) | |
| Opened: | Jeff Knisley 00:57 Jul 22, 2004 |
| NRC Officer: | John Mackinnon |
| Last Updated: | Jul 22, 2004 |
| 40890 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |