05000440/LER-2003-003, Regarding Unrecognized Diesel Generator Inoperabililty During Mode Changes
| ML033010367 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 10/20/2003 |
| From: | Kanda W FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| PY-CEI/NRR-2738L LER 03-003-00 | |
| Download: ML033010367 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4402003003R00 - NRC Website | |
text
FENOC FirstEnergy Nuclear Operating Company Perry Nuclear Power Plant 10 Center Road Perry, Ohio 44081 WMram R. Kanda Vice President - Nuclear 440-280-5579 Fax: 440-280-8029 October 20, 2003 PY-CEI/NRR-2738L United States Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Perry Nuclear Power Plant Docket No. 50-440 LER 2003-003-00 Ladies and Gentlemen:
Enclosed is Licensee Event Report (LER) 2003-003, Unrecognized Diesel Generator Inoperability During Mode Changes. This event is being reported in accordance with I OCFR50.73(a)(2)(i)(B), as an operation or condition prohibited by Technical Specifications. There are no regulatory commitments contained in this letter. Any actions discussed in this document that represent intended or planned actions, are described for the NRC's information, and are not regulatory commitments.
If you have questions or require additional information, please contact Mr. Vernon K. Higaki, Manager-Regulatory Affairs, at (440) 280-5294.
Very truly yours Enclosure: LER 2003-003 cc:
NRC Project Manager NRC Resident Inspector NRC Region III i-1, E,; 3 --A
Abstract
.Atti206,.August 21,.2003, with the reactor in MODE 1 at approximately 13 percent power, the monthly 'Diesel Generator Start and Load" surveillance was performed and the starting output voltage was discoveredt o belset-aVt approximately 4534 volts. This value was greater than the Technical Specification acceptance criteria band of-3900 to 4400 volts AC and resulted in the Division 1 diesel generator [DG] being declared inoperable.
The conditions initiating this event were traced to the reverse power trip of the Division I diesel generator and its output breaker at 1813, August 14, 2003, while restoring the Division 1, Class 1 E, 4160 volt AC electrical bus to its offsite power supply. Subsequently, the plant changed MODES two times on 8/20/03 with an inoperable diesel generator. The two MODE changes were made in violation of Technical Specifications, i.e. one at 0150 to MODE 2 at 0 percent power and the second at 2146 to MODE 1 at approximately 8 percent power. This condition is reportable per I OCFR50.73(a)(2)(i)(B).
The root causes of this event are a less than adequate questioning attitude concerning the operability of the Division 1 diesel generator including the need to restart the diesel generator to verify proper voltage adjustment; and a deficient procedure that neither addresses operation outside normal bands nor contains sufficient guidance to recover a tripped diesel and ensure voltage is properly adjusted prior to restoring the diesel to an operable status.
(if more space is required, use additional copies of NRC Farn 366A) (17)
I.
DESCRIPTION OF OCCURRENCE:
At 1206, August 21, 2003, with the reactor in MODE 1 at approximately 13 percent power, the monthly 'Diesel Generator Start and Load' surveillance was being performed and the starting output voltage was found to be approximately 4534 volts. This value is outside of the Technical Specification (TS) acceptance criteria band of 3900 to 4400 volts AC.
A root cause investigation traced the initiating event of this condition to a reverse power trip of the Division I diesel generator [DGJ and its output breaker [BKR] that occurred at 1813, August 14, 2003.
On August 14, 2003, the Perry Nuclear Power Plant was recovering from a loss of offsite power condition (Perry LER 2003-002). The Division 1, Class I E (nuclear safety related), 4160 volt electrical bus [ED] was being powered from the Division 1 diesel generator. As part of this recovery, the diesel generator was being paralleled with the Division 1 preferred power supply, the offsite source [JX], in preparation for transferring the safety bus from the diesel generator to the offsite source per the system operating instruction (SOI).
The offsite source was at a higher than normal voltage. The Division I diesel generator was prepared for paralleling with the offsite source. During the restoration, the Division I diesel generator output voltage was matched to the preferred source voltage. The syncroscope [SYN] was adjusted to rotate 'slowly in the clockwise direction" as directed in the SOI, and then the preferred source breaker was closed at approximately 12 o'clock on the syncroscope. The diesel generator began to immediately lose load as the breaker was closed, which is expected due to the diesel generator speed and voltage control reverting from the isochronous to the droop mode of operation.
At 1813, August 14, 2003, the Division 1 diesel generator and its output breaker tripped on reverse power, and the Division 1 electrical bus remained energized by the offsite source.
This diesel generator reverse power trip occurred prior to the completion of the SOI steps that would have shutdown the diesel. As such, the diesel generator shutdown step that has the operator adjust the voltage regulator to between 4100 and 4200 volts prior to shutdown was marked 'not applicable" by the control room
~-staff as-it could not be performed with the diese! generator already shutdown.-The diesel generator-trip-was._
reset and the diesel generator was placed in standby readiness at 1835, August 14, 2003.
At 1152, August 21, 2003, the Division I diesel generator was started for the performance of the 'Diesel Generator Start and Load" monthly surveillance. At 1206, it was found that the starting voltage stabilized at approximately 4534 volts, which is above the maximum allowed 4400 volts, and the diesel was declared inoperable. During the shutdown to standby readiness of the diesel generator, the step of the SOI that instructs the operator to adjust the voltage regulator [RG] between 4100 and 4200 volts was performed by the control room staff, which restored the Division 1 diesel generator to the desired voltage band. The diesel generator was stopped at 1227 and shutdown to standby readiness at 1246, per the SOI.
The system engineer recognized that there was a connection between the reverse power trip on August 14 and the starting voltage being high on August 21. Computer traces of the reverse power trip were obtained.
These traces indicated that the bus voltage was at this high level when the diesel generator tripped on reverse power on August 14, 2003. Since the Division 1 diesel generator voltage was not properly restored on August 14, 2003, the Division 1 DG voltage remained high outside of TS limits and unrecognized by the plant operators until its discovery on August 21, 2003.
(if more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
==CORRECTIVE ACTIONS==Remedial Actions A lessons learned discussion of this event was conducted on October 9, 2003 with the diesel generator responsible system engineers and other plant engineering section engineers.-
V. PREVIOUS SIMILAR EVENTS
A review of plant operating experience did not reveal any past events where diesel generator output voltage was left out of Technical Specification allowable band as a result of a reverse power trip.
A review of Perry's corrective action program from January 1, 2000 through September 9, 2003 revealed one condition report documenting a 2001 reverse power trip of the Division 1 diesel generator (condition report #
01-1099, Division 1 Diesel Generator Reverse Power Trip). This condition occurred during a post maintenance run used to vent the governor hydraulics after a new governor actuator was installed on the diesel generator. A corrective action for that event provided for the control room operators to review the investigation for sensitivity of governor control issues.
Additionally, it was identified that another reverse power trip of the Division 1 diesel generator occurred during testing in refueling outage 9 (RFO9). This occurrence was not logged in a condition report, but it was documented in the responsible system engineers RFO9 logbook. This second reverse power trip also occurred during tuning and testing of the diesel generator governor when it was inoperable for maintenance.
DG operability was not an issue in either case since both trips occurred while the DG was inoperable for maintenance under conditions where DG voltage had been within the acceptable band prior to the trip.
A similar condition was documented in Perry Licensee Event Report (LER) 2001-005-01 (CR 01-4350). This documented that as a result of normal surveillance testing, the high pressure core spray (HRCS) diesel [DG]
was found to have been impro p
ie ng-th,rcovery Fromna Level 2 reactor protection system actuation and subsequent HPCS diesel start. The cause of this event.was attributed.to the.operator over __
adjusting the governor prior to opening the generator output breaker. The over-adjustment resulted in the diesel generator failing to meet Technical Specification 3.8.1 surveillance allowable value for rated speed and frequency start time. The system operating instruction for the Division 3 diesel generator was changed to include steps to verify the diesel generator speed prior to stopping the diesel.
VI. Component Failure There were no structures, systems, or components that were inoperable at the start of this event and contributed to the event.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].