05000390/LER-2011-002
| Watts Bar Nuclear Plant | |
| Event date: | 06-22-2009 |
|---|---|
| Report date: | 06-10-2011 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3902011002R00 - NRC Website | |
A. Event
On June 22, 2009 at 21:30 Eastern Daylight Saving Time (EDT) with Watts Bar Nuclear Plant, Unit 1 (WBN) in Mode 1, while performing Surveillance Instruction 1-SI-67-1 the Unit Operator discovered that both Primary Essential Raw Cooling Water (ERCW) Supply Valve (2-FCV-67-66) and the Backup ERCW Supply Valve (2-FCV-67-68) [EIIS Code Sir to the 2A-A Emergency Diesel Generator (EDG) heat exchangers [EIIS Code EK ] were open. With both supply valves open, the system was not properly aligned, and ERCW supply headers 1A and 2B were cross-connected, which caused both trains of ERCW to be inoperable.
Under normal operating conditions, 2-FCV-67-66 is open and 2-FCV-67-68 is closed. Because 2-FCV-67-68 was not in the required position, SR 3.7.8.1, which requires verification that ERCW valves are in the correct position, could not be met. Because this surveillance requirement could not be met, according to SR 3.0.1, WBN did not meet LCO 3.7.8. Because both trains were inoperable, no LCO 3.7.8 actions applied, and LCO 3.0.3 applied, which required initiation of action within one hour and entry into MODE 3 within seven hours.
DatAWare, TVA's process data acquisition software reflected that the misalignment occurred at approximately 12:25 on June 22, indicating that from the time the valve was opened until it was closed more than nine hours had passed. Because the duration of the condition exceeded LCO 3.0.3 action times, WBN was in a condition prohibited by TS. The plant exited LCO 3.0.3 immediately after closing 2-FCV-67-68 at 21:37 on June 22. The event was documented in TVA's Corrective Action Program as Problem Evaluation Report (PER) 174704. A reportability evaluation (RE) determined that no safety function was lost, because there was sufficient ERCW capacity to supply all safety related loads with both of these ERCW supply valves open.
WA initially considered this item not to be reportable because the RE determined that even in its misaligned condition ERCW could perform its safety function and provide all necessary cooling water for both trains.
However, the NRC issued non-cited violation 05000390/2011008-001 as part of the WBN Problem Identification and Resolution (Pl&R) Inspection in January of 2011. The NRC Pl&R inspection report stated that with ERCW header 1A and 2B cross connected, the system did not meet TS 3.7.8 requirements and was inoperable, noting that the RE failed to identify that operating for 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> with the system inoperable exceeded LCO 3.0.3 action time and thus placed the unit in a condition prohibited by TS, which is a reportable event. In a letter dated May 11, 2011, WA agreed to provide this report within thirty days.
B. Inoperable Structures, Components, or Systems that Contributed to the Event.
Misalignment of the ERCW system was due to inadvertent opening of 2-FCV-67-68 as a result of human error, which resulted in cross-tying ERCW supply headers 1A and 2B, and rendered ERCW inoperable. No other structures, systems, or components contributed to the event.
C. Dates and Approximate Times of Major Occurrences Date Time (EST) Event 06/22/2009 12:25 Drop in ERCW flow recorded in DatAWare 06/22/2009 21:30 Enter LCO 3.0.3 because both 2-FCV-67-66 and 2-FCV-67-68 were open which cross connected ERCW supply headers 1A and 2B.
06/22/2009 21:37 Exit LCO 3.0.3, after closing 2-FCV-67-68.
Performance of Surveillance Instruction (SI) 1-SI-67-1, "ERCW Valves Serving Safety Equipment Position Verification.
F. Operator Actions After the Unit Operator was notified that flow control valve 2-FCV-67-68 was not closed, operators were dispatched to the 2A-A EDG room to verify valve position. Flow control valve 2-FCV-67-68 was found in the open position. Valve was then closed in accordance with SI 1-SI-67-1.
G. Safety System Responses Although flow control valve 2-FCV-67-68 was inadvertently open, which placed a greater load on ERCW train B, analysis showed that the required flow to the safety related equipment served by the ERCW system was not compromised. This event did not require any safety system response.
III. CAUSE OF EVENT
The most likely cause of this event was determined to be that painters in the area inadvertently contacted and actuated the local push buttons associated with flow control valve 2-FCV-67-68. Workers recalled working near the push buttons but were not aware of contacting push buttons. For this reason the instance was not immediately reported to Operations. Apparent cause was failure of the workers to maintain proper awareness of their surroundings and take adequate precautions.
IV. ANALYSIS OF THE EVENT
The local push buttons for 2-FCV-67-68 in the 2A-A Emergency Diesel Generator Room were inadvertently contacted which caused the flow control valve to open. The control panel is located in a tight area that provides access to the backside of the EDG. No protective cover was provided for the local push buttons to prevent inadvertent actuation.
When flow control valve 2-FCV-67-68 opened, it diverted additional ERCW flow to DG 2A-A heat exchangers which increased the load on ERCW Train B. As discussed in Section V below, the additional load on ERCW Train B did not jeopardize plant safety.
V. ASSESSMENT OF SAFETY CONSEQUENCES
The Reportability Evaluation (RE) concluded that the condition identified in PER 174704 would not have resulted in loss of design bases safety functions requiring ERCW support. Both ERCW Trains A and B were capable of performing their design bases functions during the conditions that existed while flow control valve 2-FCV-67-68 was open. The ERCW system would also have fulfilled its design bases functions if there had been a loss of Train A or Train B. Consequently the WBN accident analysis would not have been adversely impacted by this condition.
A. Immediate Corrective Actions
1. Entered LCO 3.0.3 2. Closed flow control valve 2-FCV-67-68, which isolated the 2B ERCW supply header and returned ERCW system to its proper alignment.
3. Exited LCO 3.0.3 after securing 2-FCV-67-68 in the closed position.
B. Corrective Actions to Prevent Recurrence
1. Briefed Modifications and Facilities organizations on this event, stressing maintaining awareness of surroundings and proper self-checking techniques.
2. Installed protective devices for pushbutton switches to prevent inadvertent operation.
3. Dynamic Learning Center training to emphasize attention to detail and more rigorous use of Human Error Prevention Tools, including use of the two-minute rule, to ensure a more in depth look at the work area, critical components, adjacent equipment, and if any local controls are present.
VII. ADDITIONAL INFORMATION
A. Failed Components
None B. Previous LERs on Similar Events A search of LERs and PERs documenting misalignment of the ERCW at Watts Bar Unit 1 found no LERs, but one previous similar PER. PER 123228 documented the identical misalignment for the 1A-A Emergency Diesel Generator, with the crosstie between 1A and 2B ERCW headers. In both cases, analysis indicated safety function was not adversely impacted. TVA identified the cause in both cases to be human error, but resolution of the failure to properly perform procedural steps in the first event was not applicable to prevent the inadvertent actuation that occurred during the June 22, 2009 event.
C. Additional Information:
None.
D. Safety System Functional Failure This event did not involve a safety system functional failure as defined in NEI 99-02, Revision 5.
E. Loss of Normal Heat Removal Consideration None.
VIII.COMMITMENTS None.