05000528/LER-2005-006

LER-2005-006, A subsidiary of Pinnacle West Capital Corporation
N
Palo Verde Nuclear
Generating Station
Cliff Eubanks Mail Station 7602
Vice President Tel (623) 393-6116 PO Box 52034
Nuclear Operations Fax (623) 393-6077 Phoenix, Arizona 85072-2034
102-05473-CE/SAB/DJS
April 25, 2006
ATTN: Document Control Desk
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
Dear Sirs:
Subject:N Palo Verde Nuclear Generating Station (PVNGS)
Unit 1
Docket No. STN 50-528
License No. NPF 41
Licensee Event Report 2005-006-01
Attached please find a supplemental Licensee Event Report (LER) 50-528/2005-006-01
prepared and submitted pursuant to 10 CFR 50.73. This LER reports a shutdown required by
Technical Specifications (TS) based on the inability to return "A" Emergency Diesel Generator to
operable status following a failed routine surveillance test within the TS action completion time.
In accordance with 10 CFR 50.4, copies of this LER supplement are being forwarded to the
NRC Regional Office, NRC Region IV and the Senior Resident Inspector. If you have questions
regarding this submittal, please contact James Proctor, Section Leader, Regulatory Affairs, at
(623) 393-5730.
The corrective actions described in this LER are not necessary to maintain compliance with
regulations.
Arizona Public Service Company makes no commitments in this letter.
Sincerely,
CE/SAB/DJS/gt
Attachment
cc:N B. S. MallettN NRC Region IV Regional Administrator
M. B. FieldsN NRC NRR Project Manager
G. G. Wamick NRC Senior Resident Inspector for PVNGS
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1. FACILITY NAME 2. DOCKET NUMBER 3. PAGE
Palo Verde Nuclear Generating Station (PVNGS) Unit 1 05000528 1 OF 6
4. TITLE
TS Required Reactor Shutdown on EDG "A" Failure to Start During Post Maintenance Testing

Docket Number
Event date:	03-18-2005
Report date:	04-25-2006
Reporting criterion:	10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function
Initial Reporting
ENS 41502	10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown
5282005006R01 - NRC Website

1. REPORTING REQUIREMENT(S):

This LER (50-528/2005-006-00) is being submitted pursuant to 10 CFR 50.73(a)(2)(i)(A), to report the completion of a reactor shutdown required by Technical Specifications. Specifically, on March 18, 2005 Control Room personnel completed a reactor shutdown because the load rejection retest of DG "A" is prohibited in Modes 1 through 4. LCO 3.8.1b which requires two Emergency Diesel Generators (EDG) — (EllS:EK), each capable of supplying one train of the onsite class 1E alternating current (ac) power distribution system, be operable. (Reference: ENS call # 41502)

2. DESCRIPTION OF STRUCTURE(S), SYSTEM(S) AND COMPONENT(S):

The standby power supply for each safety-related load group consists of one EDG, complete with its accessories and fuel storage and transfer systems. The standby power supply functions as a source of alternating current (ac) power for safe plant shutdown in the event of loss of preferred power and for post-accident operation of engineered safety feature (ESF) loads.

3. INITIAL PLANT CONDITIONS:

On March 18, 2005 Palo Verde Unit 1 was in Mode 1 (Power Operations), operating at approximately 100 percent power. At the start of the event EDG "A" was inoperable due to a pre-planned routine maintenance outage. No other major structures, systems, or components were inoperable at the start of the event that contributed to the event.

4.�EVENT DESCRIPTION:

Prior to the event, on March 16, 2005, at 04:00 MST Unit 1 entered LCO 3.8.1 to conduct pre-planned routine maintenance on EDG 'A.' On March 17, 2005 at 04:11 MST the Unit 1 EDG "A" failed to start during its post maintenance retest. The Diesel Generator tripped on incomplete sequence during an exception Test Mode start/run. Prior to tripping, an Area Operator reported that the diesel reached approximately 100 rpm for 15 seconds. The engine was quarantined for Root Cause Analysis. Subsequently, Unit 1 was shutdown because the load rejection retest of the replaced governor for DG "A" is prohibited in Modes 1 through 4. At that point in time, Unit l's only operable EDG was the "B" train EDG.

Technical Specification 3.8.1 condition "B" requires the following actions to be completed with one EDG inoperable:

"B.1 Perform SR 3.8.1.1 for the operable required offsite circuit(s) within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter and, B.2 Declare required feature(s) supported by the inoperable DG inoperable when its redundant required feature(s) is inoperable within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> from discovery of condition B concurrent with inoperability of redundant required feature(s) and, B.3.1 Determine OPERABLE DG is not inoperable due to common cause failure within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (or) B.3.2 Perform SR 3.8.1.2 for OPERABLE DG within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and, B.4 Restore DG to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and within 6 days from discovery of failure to meet LCO.

5. ASSESSMENT OF SAFETY CONSEQUENCES:

With one EDG inoperable, the remaining operable EDG and offsite circuits are adequate to supply electrical power to the onsite class lE ac power distribution system.

The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> completion time takes into account the capacity and capability of the remaining ac sources, a reasonable time for repairs, and the low probability of a Design Basis Accident (DBA) occurring during this period.

The event did not result in any challenges to the fission product barriers or result in the release of radioactive materials. Therefore, there were no adverse safety consequences or implications as a result of this event and the event did not adversely affect the safe operation of the plant or health and safety of the public.

The event did not result in a transient more severe than those analyzed in the updated Final Safety Evaluation Report Chapters 6 and 15. The event did not have any nuclear safety consequences or personnel safety impact.

The condition would not have prevented the fulfillment of any safety function and did not result in a safety system functional failure as defined by 10 CFR 50.73(a)(2)(v).

6. CAUSE OF THE EVENT:

The cause of the EDG "A" failure was due to a governor failure. The governor's speed controller showed signs of contaminated oil. The contamination was the result of water intrusion into the governor internals and an extended period of time in which this governor was stored in this condition. This led to the formation of rust particles which migrated to key internal components such as the servo piston, other tight tolerance areas, and internal pump check valves.

The cause of the late Licensee Event Report (LER) was cognitive error. The cognitive error appears to have been a "mental lapse," in that the LER requirement to report the completion of a shutdown was not recognized, even though ENS 41502 to report the initiation of a shutdown was recognized and performed.

Normally, the "POTENTIALLY SIGNIFICANT Maintenance Rule Functional Failure (MRFF)" Condition Reports/Disposition Request (CRDR) # 2782680 would be returned to the CRDR Review Committee for reclassification to "SIGNIFICANT" when the condition becomes reportable. A review of CRDR 2782680 determined that it was not reclassified until 04/01/2005 when it was determined to be (solely) a Maintenance Rule Functional Failure (MRFF) (SIGNIFICANT EQUIPMENT ROOT CAUSE OF FAILURE normal shutdown. A review of CRDR 2783081 determined that it was only classified as supporting the "mental lapse" theory.

7.�CORRECTIVE ACTIONS:

The governor on EDG "A" was replaced and all retests were completed satisfactorily.

The Unit was started and synchronized to the grid on March 21, 2005.

A significant investigation into the EDG "A" governor failure has been completed resulting in the following corrective actions:

• PVNGS changed governor vendors in the 4th quarter 2000. The failed governor was refurbished from the previous vendor (pre - 4th quarter 2000).

There have been no instances of water introduction noted with several governor actuators that have been refurbished by the new vendor.

• Governor oil samples were analyzed, for all three unit's diesel generators, with acceptable results.

• Receipt procedures have been written and implemented to put oil in new/refurbished speed regulating governor actuators and over speed governors as they are received in the warehouse to prevent water intrusion in the spare governors.

• Oil from the spare governors will be sampled before installation in an EDG.

• Master Instruction (WSLMI) 245877 has been revised to obtain two oil samples of speed regulating governors (one for water, and one for wear metals and other parameters) for the installation of a replacement governor.

• Since it could not be determined whether the water contamination of the oil occurred at PVNGS or at the vendor, the next vendor audit scope will include foreign material exclusion measures.

The late LER submittal was a cognitive error. All members of the Regulatory Affairs group were counseled regarding this omission to report the completion of a TS required plant shutdown.

8.�PREVIOUS SIMILAR EVENTS:

In the past three years, Palo Verde reported reactor shutdowns required by Technical Specifications but none associated with the same root cause.