05000390/LER-2003-006
| Watts Bar Nuclear Plant, Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) |
| 3902003006R00 - NRC Website | |
2. DOCKET
�
UMBER
PLANT CONDITIONS:
Watts Bar Nuclear Plant Unit I was in Mode I at approximately 36% reactor power and was returning to service following the completion of the Cycle 5 refueling outage.
II DESCRIPTION OF EVENT
A. Event
In preparation for the WBN Unit I Cycle 5 refueling outage, 6.9KV Shutdown Board breaker, 1-BKR-72-10 (EllS Code BKR), for Containment Spray System (CSS) Pimp (EIIS Codes BE/P) 1B-B was disconnected in accordance with Step 3 of Appendix C, 'Mode 4-to-Mode 5 Activities,' of General Operating (GO) Instruction 6, 'Unit Shutdown from Hot Standby to Cold Shutdown." On October 21, 2003, WBN Unit 1 was returning to service after completion of the outage and the unit was in Mode 1 at approximately 36% reactor power, when it was established that 1-BKR-72.10 was not connected and was not available to supply power to CBS Pt.rnp 1B-B. In accordance with LCO 3.6.6, `CSS,' Pump 18-B Is required to be operable in Mode 4. The restoration of the breaker should have been performed in accordance with Section 5.2.8 of General Operating (GO) Instruction 1, "Unit Startup from Cold Shutdown to Hot Standby,' and verified in accordance with Step 6 of Appendix B, 'Mode 5-to-Mode 4 Review and Approval," of GO-1.
Due to the CSS pump not being operable as the unit transitioned from Mode 5 to 1, the mode change restrictions of LCO 3,04 were not met. The total time CSS Pump 1B-B was inoperable was approximately 113.6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />s_ Considering this, Action A of LCO 3.6.6, 'CSS," requires that an inoperable CSS train be restored within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
When this action is not met, Action C.1 requires that the Unit be in Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. Neither of these actions were met. The failure to comply with the requirements of LCO 3.0.4 and LCO 3.6.6 is being reported as a violation of the Technical Specifications in accordance with 10 CFR 50.73 (a)(2)(i)(B) Problem Evaluation Report (PER) 03-018343-000 was initiated to document this event in the TVA Corrective Action Program.
B. Inoperable Structures, Components, or Systems that Contributed to the Event Except for the breaker (1-BKR-72-10) feeding CSS Pump 1B-B, there were no structures, components or systems inoperable at the start of the event that contributed to the event.
C. Dates and Approximate Times of Major Occurrences Date & Time Occurrences October 16, 2003 - 16.01 The clearance for the CSS was released. The system should have been placed in 'Standby Readiness," with the breaker connected in accordance with the System Operating instruction.
October 16, 2003 - 23:48 Entered Mode 4.
October 17, 2003 - 18'50 Entered Mode 3.
S.
October 19, 2003 - 23.18 Entered Mode 2 DESCRIPTION OF EVENT (continued) C. � Dates and Approximate Times of Major Occurrences (continued) ..._. � - � _ Date & Time - Occurrences r October 20, 2003 - 13:30 Entered Mode 1 October 21, 2003 - 09:20 LCA 3.6.6 is entered when Operations finds that the breaker feeding CSS Pump 1B-B is not connected.
October 21, 2003 - 09:35 CSS Pump 1 B-B is declared operable and LCO 3.6.6 is exited.
D. Other Systems or Secondary Functions Affected
No other systems or secondary functions were affected by this event.
E. Method of Discovery
The disconnected breaker was identified by System Engineering personnel monitoring the Bypassed and Inoperable System Indication (6151) function of the Integrate Computer System (ICS)
F. Operator Actions
Once it was identified that CSS Pump 1B-B was inoperable, the Operations staff acted appropriate!), and entered Action A of LCO 3.6.6 for one train of the CSS being inoperable. Subsequent to this, action was taken to connect breaker 1-BKR-72-10 and return CSS Pump 1B-B to service. The alignment of both trains of the CSS was verified to establish that the system was in "standby readiness." Once these actions were completed, LCO 3.6.6 was exited.
G. Safety System Responses
There were no automatic or manual safety system responses and none were necessary.
Ill. � CAUSE OF EVENT A, � Human Performance Cause and Circumstances - 10 CFR 50.73(b)(2)(ii)(J).
Revision 28 of GO-1 was issued on June 7, 2002. This revision allowed the use of a Caution Order (CO) instead of a Hold Order (HO) when the CSS was made inoperable and removed from service. This portion of the GO had not been used until the Cycle 5 refueling outage and during the outage; the CSS was placed in service several times for various outage activities. The CO was used to reduce administrative burden associated with the temporary lift of hold orders. The CO did not require the removal of the control power fuses from the circuit.
licensed operators:
1. The inappropriate approval of Step 5.2.8 of GO-1. This step was intended to ensure the CO had been removed and the CSS was In '`standby readiness" in accordance with System Operating Instruction (S01) 72.01, "Containment Spray System.
CAUSE OF EVENT (continued) 2. The inadequate verification that the CO had been removed. This verification is required by Step 6 of Appendix B, 'Mode 5-to-Mode 4 Review and Approval,' of GO-1 TVA's assessment of the first error found that the individual who approved Step 5.2.8 assumed the CSS was operable because he was aware it had been used during outage evolutions. For the second error, the assessment found that verification was performed by a walkdown of the Main Control Boards to verify the CO had been removed. In addition a clearance report was reviewed to establish that required approvals had been made.
The following factors contributed to this issue:
1. The Main Control Room (MCR) handswitch indicating lights were illuminated because the control power fuses were not removed. Thus the Operator could not use the lights as a means to determine that the breaker was disconnected.
2. The Integrated Computer System (ICS) Bypassed and Inoperable Status Indication (BISI) system was used to determine that the breaker was disconnected. This system is available to the Operations staff on the ICS.
However, there was no requirement for it to be used to verify the configuration of a system .
3. S01-72.01 requires that the proper liquid level in the header be verified. However, the instruction only addressed placing the pump in service if the line was required to be filled Considering the above, the root cause of this event was determined to be:
An erroneous assumption that the Containment Spray system was configured normal due to the presence of control power lights on the MCR handswitch, use of the system during the outage for various activities, and the verification of the standby alignment via the removal of the CO.
IV. ASSESSMENT OF SAFETY CONSEQUENCES
The breakers feeding the two trains of the Containment Spray System (CSS) pumps were disconnected in preparation for the Unit 1 Cycle 5 refueling outage. This action was performed in accordance with Step 3 of Appendix C, 'Mode 4-to-Mode 5 Activities,' of General Operating (GO) Instruction 6, 'Unit Shutdown from Hot Standby to Cold Shutdown.' However, during the startup process atter the outage and subsequent re-entry into Mode 4, the breaker for CSS Pump 1B-B was not reconnected. The restoration of the breaker should have been performed in accordance with Section 5.2.8 of General Operating (GO) Instruction 1, "Unit Startup from Cold Shutdown to Hot Standby,' and verified in accordance with Step 6 of Appendix B, 'Mode 5-to-Mode 4 Review and Approval,' of GO-1.
Two CSS trains are required to be operable in Modes 1, 2, 3, and 4. However, only one train is required to operate following a design basis event for the CSS to perform its design basis accident mitigation function. The Operation's Lags were reviewed to assure that the opposite train. C55 Pump 1A-A, was available for accident mitigation during the time period when the breaker for the 1B-B pump was disconnected. This review also included Train A of the Emergency Raw Cooling Water (ERCW EIIS Code Ell) system and Train A of the Emergency Diesel Generators (EDGs - ElIS EK), as these systems would be required to support operation of CSS Pump 1A-A The review of the log was performed to determine if the following Technical Specification (TS) Limiting Conditions for Operations (LCOs) were entered during the time period between Mode 4 re-entry on October 16, 2003, at 23:48 and October 21, 2003, at 09:35 when CSS Pump 1B-B was returned to operable status:
V. ASSESSMENT OF SAFETY CONSEQUENCES (continued) LCO 3.6.6, "CSS," for Train A of the CSS.
LCO 3.7.8, "ERCW," for Train A of the EF CW LCC) 3.8.1, "AC Sources - Operating,' for Train A of the EDGs.
The review determined that there were no entries into the three LCOs and based on this it was concluded that Train A of the CSS was operable and available for the system to perfonn its design basis accident mitigation function. Therefore, the safety consequences of this event were not significant.
V. C CORRECTIVE ACTIONS A. C Immediate Corrective Actions 1. Breaker, 1-BKR-72-10, was reconnected to return CSS Pirnp 1B-B to service.
2. The alignment of both trains of the CSS was verified in accordance with Section 5.0, "Standby Readiness,' of System Operating Instruction (SO!) 72.01, 'Containment Spray System.
B. C Corrective Actions to Prevent Recurrence - (TVA does not consider these items to constitute regulatory commitments. TVA's corrective action program tracks completion of these actions.) 1. The Operator involved in the event was counseled for not verifying assumptions.
2. The event was covered with all Operations' crews stressing the need to verify configuration versus assuming that it is in the correct configuration.
3. The Unit Supervisor involved in the event was counseled to ensure computer generated alarms are responded to as appropriate.
4. The Operations staff will receive additional training on the use of the ICS BISi computer function and its practical uses.
5. Operations has revised the general operating procedure to strengthen the requirements to verify the CSS is configured correctly following release of a Caution Order.
VI_ ADDITIONAL INFORMATION A. F Failed Components There were no failed components involved in this LEA.
WIC FORM 366A (1-2001) The following is a listing of the LERs which have been initiated for Watts Bar clue to violations of the Technical Specifications:
LER Number Cause of Event 1. 390/1996.02 The instruments retied on by the operators to verify Surveillance Requirement 3.5.1.2 were inaccurate.
2. 390/1996-24 The detail contained in the Maintenance configuration log of a Work Order was inadequate to ensure the component was restored to the proper configuration.
3. 390/1997-16 This LER documented a situation where the handswitches for both fuel oil transfer pumps for the 213-B Emergency Diesel Generator were mispositioned. Atter a thorough review the specific cause of the mispositioned switches could not be determined.
4. 390/2000-02 This LER resulted from a change in the scope of a Problem Evaluation Report which was implemented without appropriate reviews and approvals.
As indicated in Section III, "Cause of Event,' LER 390/2003-06 resulted from an erroneous assumption that the CSS was operable prior to the planned mode changes. Based on the above comparison of the causes of previous events, the recurrence controls established for the listed LERs would not have prevented the Technical Specification violation documented by LER 390/2003-06_ C. Additional Information.
None.
D. Safety System Functional Failure This event did not involve a safety system functional failure as defined in NE1-99-02, Revision 0.
E. Loss of Normal Heat Removal Consideration This event is not considered a scram with loss of normal heat removal.
VII. COMMITMENTS
None