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| Entered date | Event description | |
|---|---|---|
| ENS 54431 | 10 December 2019 09:52:00 | This report describes an invalid actuation of the Unit 2 Turbine Driven Auxiliary Feedwater Pump that occurred on October 31, 2019. This report is being made in accordance with 10CFR50.73(a)(1), which states, in part, 'In the case of an invalid actuation reported under 10CFR50.73(a)(2)(iv), other than actuation of the Reactor Protection System (RPS) when the reactor is critical, the licensee may, at its option, provide a telephone notification to the NRC Operations Center within 60 days after discovery of the event instead of submitting a written LER.' On October 31, 2019, Comanche Peak Nuclear Power Plant Unit 2 was in Mode 1 operating at 100% power. At 1919 CDT, the Main Steam Line 2-01 steam supply valve to the TDAFWP opened due to a loss of continuity between the fuse supplying control power to the valve positioner and the fuse clips. Operators initiated a 50MW load reduction to maintain power less than 100%. The steam supply to the TDAFWP was closed, the TDAFWP was stopped, and the fuse clips were tightened. Unit 2 was returned to full power at 2055 CDT. The specific train and system that actuated was the third AFW train on Unit 2. The train actuation was complete and during the TDAFWP start the system started and functioned correctly. The NRC Resident Inspector was notified. |
| ENS 44439 | 25 August 2008 16:27:00 | This report describes an invalid actuation of the Unit 1 Turbine Driven Auxiliary Feedwater (TDAFW) pump that occurred on June 28, 2008. This report is being made in accordance with 10CFR50.73(a)(1), which states, in part, 'In the case of an invalid actuation reported under 10CFR50.73(a)(2)(iv), other than actuation of the Reactor Protection System (RPS) when the reactor is critical, the licensee may, at its option, provide a telephone notification to the NRC Operations Center within 60 days after discovery of the event instead of submitting a written LER.' On June 28, 2008, Comanche Peak Nuclear Power Plant Unit 1 was in Mode 1 operating at 100% power. At 1904 CDT, the steam supply valve from Main Steam Line 1-04 to the TDAFW pump opened due to a failed diaphragm. Turbine load was subsequently reduced from 1207MWe to 1150MWe per Operations procedures. The upstream isolation valve for the steam supply to the TDAFW pump was closed and the TDAFW pump was stopped. Unit 1 was returned to full power at 2120 CDT and the failed diaphragm was subsequently replaced. The specific train and system that actuated was the third AFW train on Unit 1. The train actuation was complete and during the TDAFW start the system started and functioned correctly. The licensee has notified the NRC Resident Inspector. |
| ENS 43354 | 10 May 2007 15:22:00 | This report describes three invalid actuations of the Unit 2 Turbine Driven Auxiliary Feedwater (TDAFW) pump that occurred on March 12,2007. This report is being made in accordance with 10CFR50.73(a)(1), which states, in part, 'In the case of an invalid actuation reported under 10CFR50.73(a)(2)(iv), other than actuation of the reactor protection system (RPS) when the reactor is critical, the licensee may, at its option, provide a telephone notification to the NRC Operations Center within 60 days after discovery of the event instead of submitting a written LER.' On March 12, 2007 at 2027, while performing operator rounds, Operations personnel heard a venting noise coming from the vicinity of the Main Steam Line 2-04 to Auxiliary Feedwater Pump Turbine Steam Supply Valve. One of the Operators put his hand close to the exhaust pilot valve, restricting the venting air flow, which increased the sensing pressure on one of the valve's ports. The valve swapped, exhausting the diaphragm. This caused the TDAFW steam supply valve to fail open and the TDAFW pump started and reached full flow. Operations responded to the event by manually running back the Main Turbine load to 1100 Mew to ensure Reactor Power remained less than 100%. The TDAFW pump was secured and the steam supply valve hand switch was placed in AUTO. At 2056, an I&C technician was leak checking the valve actuator and tubing joints. The I&C technician got within close proximity of the Main Steam Line 2-04 to Auxiliary Feedwater Pump Turbine Steam Supply Valve and restricted the venting air flow, which increased the sensing pressure on one of the exhaust pilot valve's ports. The pilot valve swapped, exhausting the diaphragm. The TDAFW Steam Supply Valve failed open again and the TDAFW pump started a second time and reached full flow. At 2100, Shift Operations placed the steam supply valve in pullout and declared the TDAFW inoperable. To prevent further inadvertent starts, Operations decided to close the upstream isolation valve. While in the process of closing the isolation valve, the Operator heard air venting from the vicinity of the Main Steam Line 2-04 to Auxiliary Feedwater Pump Turbine Steam Supply Valve. The Operator put his hand under the exhaust pilot valve such that the air flow was restricted, which increased the sensing pressure on one of the valve's ports. The pilot valve swapped, exhausting the diaphragm. The TDAFW steam supply valve failed open again and the TDAFW pump started a third time. Since the upstream isolation valve was partially closed, the TDAFW pump only reached a partial flow of 235 gpm. Shift Operations initiated a clearance to prevent further inadvertent TDAFW pump starts and a work order was initiated to determine the failure mechanism. On March 13, 2007 at 2223, Shift Operations declared the TDAFW pump operable. The specific train and system that actuated was the third AFW train on Unit 2. During each of the three TDAFW pump starts, the system started and functioned correctly. During the first two pump starts, the train actuation was complete. As described above, on the third start the train actuation was partial due to less than full flow being developed. The second and third TDAFW pump starts took place during trouble shooting and clearance isolation activities, respectively, which occurred prior to the cause being identified. The three AFW invalid actuations occurred due to incorrect setup of the exhaust pilot valve for the Main Steam Line 2-04 to Auxiliary Feedwater Pump Turbine Steam Supply Valve. The NRC Resident Inspector will be notified of this report. |