05000311/LER-2002-001
| Salem Generating Station Unit 2 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown |
| 3112002001R00 - NRC Website | |
DOCKET (2) R
PLANT AND SYSTEM IDENTIFICATION
Westinghouse — Pressurized Water Reactor Emergency Diesel Generator (EDG) {DV-} * Energy Industry Identification System {EIIS} codes and component function identifier codes appear as (SS/CCC)
CONDITIONS PRIOR TO OCCURRENCE
Salem Unit 2 was in Mode 1 at 100% power prior to the Technical Specification required shutdown.
Mode 3 (Hot Standby) was entered at 0836 on January 11, 2002. The 2A EDG was declared operable at 1242 hours0.0144 days <br />0.345 hours <br />0.00205 weeks <br />4.72581e-4 months <br /> on January 12 and the cool down to Mode 5 was halted.
No structures, systems or components were inoperable beyond the 2A EDG at the time of the occurrence that contributed to this event.
DESCRIPTION OF OCCURRENCE
On January 8, 2002, at 0303 hours0.00351 days <br />0.0842 hours <br />5.009921e-4 weeks <br />1.152915e-4 months <br />, the 2A emergency diesel generator (EDG) {EK/-} was taken out of service for a scheduled maintenance window to last 44 hours5.092593e-4 days <br />0.0122 hours <br />7.275132e-5 weeks <br />1.6742e-5 months <br />. Limited Condition for Operation (LCO) action 3.8.1.1.b was entered which states, "...with one diesel generator...inoperable,... restore the inoperable diesel generator to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
On January 9, at approximately 2244 hours0.026 days <br />0.623 hours <br />0.00371 weeks <br />8.53842e-4 months <br />, the 2A EDG displayed erratic speed and voltage control when attempting to perform post maintenance surveillance testing. A team was then assembled to assist in the troubleshooting of the EDG.
On January 10, at 1821 hours0.0211 days <br />0.506 hours <br />0.00301 weeks <br />6.928905e-4 months <br /> and 1950 hours0.0226 days <br />0.542 hours <br />0.00322 weeks <br />7.41975e-4 months <br /> the 2B and 2C EDGs, respectively, were started and loaded to comply with TS action 3.8.1.1.b which states, "...determine the two remaining OPERABLE diesel generators are not inoperable due to a common cause failure or perform Surveillance Requirement 4.8.1.1.2.a.2 within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />...".
At 0303 on January 11, the 72-hour action statement time expired and preparations were made to take the unit offline. At 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br />, power reduction was commenced to comply with the Technical Specifications. Troubleshooting of the 2A EDG continued through the power reduction. At 0836, DOCKET (2) DESCRIPTION OF OCCURRENCE (cont'd) Salem Unit 2 entered Mode 3 in accordance with the requirements of the Technical Specifications.
Plant cool down to Mode 5 (COLD SHUTDOWN) was commenced.
During the day shift on January 11, the voltage regulator board for the 2A EDG was replaced. At 2138 hours0.0247 days <br />0.594 hours <br />0.00354 weeks <br />8.13509e-4 months <br />, the EDG was run unloaded and all parameters were determined to be satisfactory. The EDG was stopped at 2212 and preparations for voltage regulator and governor tuning commenced.
At 0355 on January 12, the 2A EDG was started to complete the tuning. Prior to reaching the last step of the tuning process, the 2-hour unloaded run limit was reached. Per procedure, the EDG either needs to be loaded or shutdown. An attempt was made to load the EDG, however, the output breaker {EK/BKR} tripped on reverse power and the EDG was stopped at 0612. Troubleshooting was conducted and identified that there were no mechanical failures that caused the reverse power. The 2A EDG was started at 0847 with no problems noted. The operability run of the EDG commenced at 1019. The plant cool down reached 210°F reactor coolant temperature (lower end of Mode 4) at 1032. At 1242, the 2A EDG was declared operable and the shutdown to cold shutdown was stopped.
ANALYSIS OF OCCURRENCE
A team was assembled to assist in the troubleshooting of the 2A EDG upon the failure of the EDG to satisfactorily run following planned maintenance. At the time the 2A EDG failed the post maintenance operability run there were only 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> remaining in the action statement time. Investigation into the oscillations of the EDG began immediately, however, a formal 'Technical Issues' process evaluation (a detailed comprehensive issue assessment methodology) was not performed in parallel with the initial troubleshooting activities. Upon failure of the initial troubleshooting activities to correct the EDG oscillations the technical issues process was formally started approximately 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> after the original oscillation problem was reported. Upon implementing the Technical Issues process, a plan was developed which lead to the repair (replacement of the voltage regulator board) of the 2A EDG and restoring the 2A EDG to operable status on January 12, 2002 at 1242 hours0.0144 days <br />0.345 hours <br />0.00205 weeks <br />4.72581e-4 months <br />.
CAUSE OF OCCURRENCE
The cause of the shutdown of Salem Unit 2 was attributed to a failure to diagnose and repair the cause of the EDG oscillations within the remaining LCO time following planned maintenance.
The oscillations of the EDG appear to have been from a failed voltage regulator board, further evaluation of the failed regulator board is ongoing. Upon replacement of the voltage regulator board, the oscillations were corrected. A review of maintenance records for the EDG voltage regulators identified that no preventive maintenance is performed on this component.
DOCKET (2)
MRABER
CAUSE OF OCCURRENCE (cont'd) The cause of the EDG breaker to trip on reverse power is attributed to personnel error. The equipment operator did not immediately increase load on the EDG following closure of the breaker as stated in the procedure. The procedure contains a caution to alert the operator that not immediately increasing load may cause tripping of the breaker on reverse power. The equipment operator was not aware that the reverse power trip timer for the breaker was only set for nine seconds following closure of the breaker.
PRIOR SIMILAR OCCURRENCES
A review of LERs for Salem Unit 1, Salem Unit 2 and Hope Creek over the past three years identified no other instances of a Technical Specification (TS) shutdown due to failure to diagnose an equipment failure prior to exceeding the TS action statement time. The only other TS required shutdown in the past three years occurred at Hope Creek as reported in LER 354/01-001-00 when both trains of main steam isolation valve sealing steam were inoperable at the same time due to excessive leakage in one train and an emergent equipment failure in the other train.
SAFETY CONSEQUENCES AND IMPLICATIONS
Although the 2A EDG was inoperable for greater than allowed action statement time specified in the Salem Unit 2 Technical Specifications, there was no impact to the ability to either safely shutdown the plant or respond to a design basis accident. In the event that a design basis accident occurred during the time the 2A EDG was inoperable, the two sources of offsite power to the safety related busses remained operable. In the event of an accident, the required mitigation equipment would have been supplied power from the offsite power source and therefore the entire complement of accident mitigation equipment remained available. However, in the case of a design basis accident with a loss of offsite power, the two remaining EDGs were operable and capable of supplying emergency power to their respective busses. As stated in the Salem UFSAR section 8.3.1.5, any two diesel generators and their respective busses can supply sufficient power for operation of the required accident mitigation equipment. Based on the above, there was no impact to the health and safety of the public.
A review of this condition determined that a Safety System Functional Failure (SSFF) has not occurred as defined in Nuclear Energy Institute (NEI) 99-02.
DOCKET (2)
CORRECTIVE ACTIONS:
1. The voltage regulator card on the 2A EDG was replaced and the EDG was returned to an operable status. A review will be performed of the preventive maintenance program for the EDGs to determine if changes to the preventive maintenance being performed are necessary.
Completion of this action is being tracked in accordance with PSEG Nuclears Corrective Action Program.
2. This event will be reviewed by the Operations Training Review Group to evaluate appropriate changes to the Equipment Operator Training Program. This action is being tracked in accordance with PSEG Nuclear's Corrective Action Program.
3. Improvements are being made to procedure SH.OP-AP.ZZ-0101, "Post-Transient Response Requirements", covering TARP team responsibilities to address the implementation and integration of the Technical Issues process and field troubleshooting. Completion of this action is being tracked in accordance with PSEG Nuclear's corrective action program.
4. Lessons learned from this event will be discussed with TARP team leaders and line managers.
Completion of this action is being tracked in accordance with PSEG Nuclear's corrective action program.
COMMITMENTS
The corrective actions cited in this LER are voluntary enhancements and do not constitute commitments.