05000272/LER-2002-004, For Salem Generating Station Unit 1 Regarding Manual Reactor Trip & Automatic Auxiliary Feedwater Actuation on Low Steam Generator Level Due to Feedwater Pump Runback
| ML030230273 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 01/13/2003 |
| From: | Waldinger L Public Service Enterprise Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LR-N03-0001 LER 02-004-00 | |
| Download: ML030230273 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2722002004R00 - NRC Website | |
text
PSEG Nuclear LLC P.O Box 236, Hancocks Bridge, New Jersey 08038-0236 0 PSEG
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January 13, 2003 LR-N03-0001 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 LER 272 i 2002- 004 - 00 SALEM GENERATING STATION UNIT 1 FACILITY OPERATING LICENSE DPR-70 DOCKET NO. 50-272 This Licensee Event Report entitled "Manual Reactor Trip and Automatic Auxiliary Feedwater Actuation on Low Steam Generator Level due to Feedwater Pump Runback" is being submitted pursuant to the requirements of 10CFR50.73(a)(2)(iv)(A). The attached LER contains no commitments.
Sin L. H. Waldinger Director Site Operations Attachment
/WJM C
Distribution RTL 3E.111 95-2i68 REV. 799
Abstract
On November 12, 2002, Salem Unit I was manually tripped due to a Steam Generator Feedwater Pump (SGFP) runback resulting from voltage decrease in the control power to its governor. The undervoltage occurred when a technician inadvertently grounded the power circuit for a valve limit switch during troubleshooting. The runback was not annunciated in the control room; a level alarm was received several minutes later. Operators initiated main turbine runback and reduced reactor power. As level continued to decrease to the trip setpoint, operators initiated a manual reactor trip. Auxiliary feedwater (AFW) pumps started automatically as expected, and plant shutdown was achieved without complications.
The root causes are silent SGFP runback that requires manual operator action, inadequate error prevention while taking voltage readings, and lack of recognition of the risk of troubleshooting. Corrective actions include design changes to minimize and improve plant response to SGFP runbacks, review of the human performance aspects of the root causes and procedural improvements for managing risk of work activities.
Operator actions were in accordance with procedures and the plant responded as designed to the manual reactor trip. There were no safety consequences associated with this event. This event is reported pursuant to 1 OCFR50.73(a)(2)(iv)(A) due to reactor trip and AFW system actuation.
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- - U.S. NUCLEAR REGULATORY COMMISSION (6-1998)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION DOCKET (2)
FACILITY NAME (1)
NUMBER (2)
L ER NUMBER (6)
P AGE ( 3)
SEQUENTIAL REVISION YEAR NUMBER NUMBER Salem Generating Station Unit No. 1 05000272 2002 0 0 00 2 OF 4]
TEXT (If more space is required, use additional co pies of NRC Form 366A) (17)
PLANT AND SYSTEM IDENTIFICATION
Westinghouse - Pressurized Water Reactor Feedwater System - ElIS Identifier {BF/--}
- Auxiliary Feedwater System {BA/--}
Control Rod Drive System {AA/--}
Feedwater/Steam Generator Water Level Control System {JB/--}
Plant Protection System {JC/--}
- Energy Industry Identification System {EIIS} codes and component function identifier codes appear as (SS/CCC)
CONDITIONS PRIOR TO OCCURRENCE Mode 1 - 100% power. No structures, systems, or components were inoperable at the time of the occurrence that contributed to the event. The Control Rod Drive System {AA} was in manual to support axial flux difference target value determination.
DESCRIPTION OF OCCURRENCE At approximately 0945 on November 12, 2002, 11 Steam Generator Feedwater Pump (SGFP) {BF/P}
began a runback in response to a momentary voltage decrease in the control power to its governor
{JB/GRL}. The undervoltage condition occurred when a technician inadvertently grounded the power circuit for the 11 SGFP warm-up valve limit switch during troubleshooting of the valve's position indication. Initiation of SGFP runback is not annunciated in the control room. Operators were alerted to the transient several minutes later by the control console alarm for steam generator level program deviation that is activated if level in any steam generator is +/- 5% from the program value. Operator actions included manual main turbine runback followed by tripping the 11 SGFP to initiate automatic turbine runback. Control rods were inserted via manual control until rod control was placed in automatic, after which rod insertion continued to reduce reactor power.
Operators observed steam generator level was decreasing toward the low-low reactor trip setpoint of 14% and initiated a manual reactor trip. All three auxiliary feedwater pumps {BANP} started as designed on low-low steam generator water level after the reactor trip. Plant response was as expected and operators commenced shutdown in accordance with operating procedures.
- - 7 1'U.S. NUCLEAR REGULATORY COMMISSION (6-1998)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION DOCKET (2)
FACILITY NAME (1)
NUMBER (2)
LER NUMBER (6)
PAGE (3)
SEQUENTIAL REVISION YEAR NUMBER NUMBER Salem Generating Station Unit No. 1 05000272 2002 0 0 4
00 3 OF 4 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
CAUSE OF OCCURRENCE The root causes of this event are 1) the design feature of the SGFP control system that allows SGFP runback without annunciation and requires manual operator action to recover steam generator level.
The operators were not alerted to the transient until steam generator level had begun to decrease as indicated by the program deviation alarm. 2) Failure of the technician to use error prevention techniques that would have prevented the initiating event (i.e., shorting the valve limit switch circuit that resulted in undervoltage at the SGFP governor). 3) Lack of risk recognition associated with troubleshooting. The Control Room Supervisor, Work-It-Now (WIN) team Senior Reactor Operator (SRO), maintenance supervisor and technician did not adequately recognize and manage the risk associated with taking voltage readings at the valve limit switch.
PRIOR SIMILAR OCCURRENCES Recent SGFP runbacks have occurred at Salem but they did not require actuation of the reactor protection system. In April 2001 a SGFP runback without annunciation occurred at Salem Unit 1 during a reduction in reactor power. The pump runback was due to a momentary overvoltage condition associated with transfer of the SGFP control power supply inverter. In April 2002 a Salem Unit 2 SGFP runback without annunciation occurred after a bus transfer between two station power transformers. The bus transfer was performed while the SGFP's control power supply inverter was aligned to its alternate source, resulting in a momentary undervoltage condition. Corrective actions included governor power supply conditioning to prevent pump runback due to voltage spikes, and improved procedural controls for inverter alignment and bus transfers. In both prior events, the operators promptly responded to the transient and recovered steam generator level before the low-low level setpoint was reached.
Review of Salem and Hope Creek LERs over the past two years did not identify any events resulting from inadequate error prevention techniques or lack of risk recognition associated with troubleshooting.U.S. NUCLEAR REGULATORY COMMISSION (6-1998)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION DOCKET (2)
FACILITY NAME (1)
NUMBER (2)
LER NUMBER (6)
PAGE (3)
SEQUENTIAL REVISION YEAR NUMBER NUMBER Salem Generating Station Unit No. 1 05000272 2002 0 0
4 00 4 OF 4 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
SAFETY CONSEQUENCES AND IMPLICATIONS
There were no safety consequences associated with this event. Plant response to the manual reactor trip was normal. The auxiliary feedwater pumps started as designed and maintained adequate flow to the steam generators. Operator actions to safely shut down the plant were in accordance with procedures.
A review of this event determined that a Safety System Functional Failure (SSFF) as defined in Nuclear Energy Institute (NEI) 99-02 has not occurred.
This event is being reported pursuant to 1 OCFR50.73(a)(2)(iv)(A) due to manual reactor trip and automatic actuation of the auxiliary feedwater system.
CORRECTIVE ACTIONS
- 1. PSEG is evaluating design changes that would reduce the likelihood of and improve plant response to SGFP runbacks.
- 2. Human performance aspects of the root causes of this event have been addressed in accordance with PSEG company policy.
- 3. Work management and maintenance procedures are being revised to improve guidance for managing work activities with regard to risk.
COMMITMENTS
The corrective actions cited in this LER are voluntary enhancements and do not constitute
commitments