ENS 43354
ENS Event | |
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01:27 Mar 13, 2007 | |
Title | Invalid Tubine Driven Auxiliary Feedwater Pump Starts |
Event Description | 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. |
Where | |
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Comanche Peak ![]() Texas (NRC Region 4) | |
Reporting | |
10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
Time - Person (Reporting Time:+1405.92 h58.58 days <br />8.369 weeks <br />1.926 months <br />) | |
Opened: | Gary Merka 15:22 May 10, 2007 |
NRC Officer: | Jeff Rotton |
Last Updated: | May 10, 2007 |
43354 - NRC Website
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Unit 2 | |
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Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |
WEEKMONTHYEARENS 544312019-11-01T00:19:0001 November 2019 00:19:00
[Table view]10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of the Unit 2 Turbine Driven Auxiliary Feedwater Pump (Tdafwp) ENS 505622014-09-12T18:42:00012 September 2014 18:42:00 10 CFR 50.73(a)(1), Submit an LER Invalid Specified System Actuation ENS 502122014-04-22T13:30:00022 April 2014 13:30:00 10 CFR 50.73(a)(1), Submit an LER Emergency Diesel Generator Invalid Actuation ENS 484632012-10-31T11:15:00031 October 2012 11:15:00 10 CFR 50.73(a)(1), Submit an LER Sequencer Fault Resulting in System Actuations ENS 444392008-06-29T00:04:00029 June 2008 00:04:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Report for an Invalid Actuation of Unit 1 Tdafw Pump ENS 433542007-03-13T01:27:00013 March 2007 01:27:00 10 CFR 50.73(a)(1), Submit an LER Invalid Tubine Driven Auxiliary Feedwater Pump Starts 2019-11-01T00:19:00 | |