ML051050342

Re Actuation of an Unit 1 Emergency Diesel Generator (EDG)

ML051050342
Person / Time
Site:	Palo Verde
Issue date:	04/06/2005
From:	Danni Smith Document Control Desk
To:	Arizona Public Service Co
References
102-05243-DMS/SAB/DJS LER 05-001-00
Download: ML051050342 (9)

Text

10CFR50.73 LAM Palo Verde Nuclear Generating Station A subsidiary of Pinnacle West Capital Corporation David M. Smith Plant Manager Tel: 623-393-6116 Nuclear Production Fax: 623-393-6077 email: DSMITHIO@apsc.com Mail Station 7602 PO Box 52034 Phoenix, Arizona 85072-2034 102-05243-DMS/SAB/DJS April 6, 2005 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit I Docket No. STN 50-528 License No. NPF 41 Licensee Event Report 2005-001-00 Attached please find Licensee Event Report (LER) 50-528/2005-001-00 prepared and submitted pursuant to 10 CFR 50.73. This LER reports an event resulting in the actuation of one of the Unit 1 emergency diesel generators.

In accordance with 10 CFR 50.4, a copy of this LER is being forwarded to the NRC Region IV Office and the Senior Resident Inspector. If you have questions regarding this submittal, please contact Daniel G. Marks, Section Leader, Regulatory Affairs, at (623) 393-6492.

Arizona Public Service Company makes no commitments in this letter.

Sincerely, DMS/SAB/DJS/ca

-r64qq 49",

1-14-1 A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Comanche Peak

• Diablo Canyon

• Palo Verde

• South Texas Project

• Wolf Creek

ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Licensee Event Report 50-528/2005-001-00 Page 2 Attachment cc:

B. S. Mallet, Region IV Administrator G. G. Warnick, Sr. Resident Inspector M. B. Fields, PVNGS Project Manager (all w/attachment)

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007 (6-2004)

Estimated burden per response to comply with this mandatory collection request 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />. Reported lessons learned are Incorporated Into the licensing process and fed back to Industry. Send comments regarding burden estimate to the Records and FOIAlPrivacy Service Branch (To5 F52). U.S.

LICENSEE EVENT REPORT (LER)

Nuclear Regulatory Commission. Washington, DC 20555-0001, or b Internet e-mail to lnfocollects@nrc.gov, and to the Desk Officer, Office Of In ormation and Regulatory Affairs, NEOB-10202, (3150-0104). Office of Management and Budget, Washington. DC 20503. If a means used to Impose an Information (See reverse for required number of collection does not display a currently valid OMB control number, the NRC may fo v r each blocknot conduct or sponsor, and a person Is not required to respond to, the digits/characters for each block)

Information collection.

1. FACILITY NAME

2. DOCKET NUMBER

3. PAGE Palo Verde Nuclear Generating Station (PVNGS) Unit 1 05000528 1 OF 7

4. TITLE Actuation of an Unit I Emergency Diesel Generator (EDG)

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED SEQUENTIAL REVFACILITY NAME MONTH DAY YEAR YEAR NUMBER NO.

MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 02 06 2005 2005 - 001 -

00 04 06 2005

9. OPERATING MODE 11.THIS REPORT ISSUBMITTEDPURSUANTTO THEREQUIREMENTS OF 10 CFR§: (Check allthatapply) o 20.2201(b) 0l 20.2203(a)(3Xi)

D 50.73(aX2)(i)(C)

El 50.73(a)(2)(v0i) 1 0

20.2201(d)

D 20.2203(a)(3Xii)

El 50.73(aX2)(ii)(A)

El 50.73(aX2)(vfii)(A) o 20.2203(a)(1)

El 20.2203(a)(4)

[I 50.73(a)(2)(ii)(B)

E 50.73(a)(2)(viii)(B) 0O 20.2203(a)(2)(i)

El 50.36(c)(1XIXA)

El 50.73(a)(2)(iii)

El 50.73(aX2)(ix)(A)

10. POWER LEVEL 0

20.2203(a)(2)(ii)

El 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A) 0l 50.73(aX2)(x)

El 20.2203(a)(2)(iii) 0l 50.36(c)(2)

El 50.73(aX2)(v)(A)

El 73.71(a)(4)

El 20.2203(a)(2)(iv)

El 50.46(a)(3Xii)

El 50.73(aX2)(v)(B)

El 73.71(aX5) 100

[

20.2203(a)(2)(v) a 50.73(a)(2)(i)(A)

D 50.73(a)(2)(v)(C)

D OTHER El 20.2203(a)(2)(vi) 0 50.73(a)(2Xi)(B)

El 50.73(a)(2)(v)(D)

Specify In Abstract below or In NRC Form 366A

12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (Indude Area Code)

Daniel G. Marks, Section Leader, Regulatory Affairs 623-393-6492

13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSE SYSTEM COMPONENT MANU-REPORTABLE CAUSE SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX X

EA BU G080 I

14. SUPPLEMENTAL REPORT EXPECTED i15.

EXPECTED MONTH DAY YEAR SUBMISSION E YES (If yes, complete 15. EXPECTED SUBMISSION DATE) 0 NO DATE ABSTRACT (Umit to 1400 spaces, I.e., approximately 15 single-spaced typewritten lines)

On February 6, 2005, at approximately 22:19 Mountain Standard Time (MST) a valid actuation of the PVNGS Unit 1 Train 'B' EDG occurred as a result of under-voltage on its respective safety bus (PBB-S04). EDG 'B' started and loaded as designed to energize PBB-S04. The loss of power to the safety bus was the result of a fault associated with a 13.8KV load breaker cubicle which caused the breaker for the normal power supply to switchgear 1 E-NANS06 to trip open on over-current. The PVNGS Fire Department and Auxiliary Operators responded to a report of smoke and upon arrival found no fire. The Fire Department verified the fire was completely extinguished and there were no secondary fires.

Unit 1 entered Technical Specification LCO 3.8.1, Condition 'A', for one (of two) required offsite circuits inoperable.

Various other Technical Specifications LCO's were momentarily entered and exited for PBB-S04 being de-energized for approximately 7 seconds. No Emergency Plan declaration was made and none was required. Unit 1 was at approximately 100% power, at normal operating temperature and pressure prior to and following the EDG actuation.

No other ESF actuations occurred and none were required. The event did not adversely affect the safe operation of the plant or the health and safety of the public.

Previous similar events have been reported in LERs 50-528/2004-006, 50-529/2004-003-00 and 50-530/2003-004.

NRC FORM 366 (6-2004)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (6s4)

LICENSEE EVENT REPORT (LER)

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE YEAR SEQUENTAL REVISION Palo Verde Nuclear Generating Station 0 I

NUMBER NUMBER Unit 1 05000529 2

F 7 Unit 12005 001 00

17. NARRATIVE (if more space is required, use additional copies of NRC Form 366A)

1.

REPORTING REQUIREMENT(S):

Pursuant to 10 CFR 50.73(a)(2)(iv)(A), this LER reports an event that resulted in the valid automatic actuation of one of the Unit 1 emergency diesel generators (EDGs) [EIIS Code:

EB].

Pursuant to 10 CFR 50.72(b)(3)(iv)(A), Arizona Public Service Company (APS) made notification of this event to the NRC Headquarters Operations Officer on February 7, 2005 (reference ENS 41379).

2.

DESCRIPTION OF EVENT RELATED STRUCTURE(S), SYSTEM(S) AND COMPONENT(S):

Onsite Power System [EIIS Codes: EA, EB &EC]

Offsite sources of power provide preferred power to the three units through the secondary windings of three startup transformers. The onsite power system of each unit is divided into two separate systems: the non-Class 1 E power system and the Class 1 E power system which is divided into two separate load groups. Power is supplied to the auxiliaries at 13.8 kV, 4.16 kV, and 480V levels. The onsite power system includes the Class 1 E power system which provides auxiliary ac and dc power for equipment used to shut down the reactor safely following a design basis event. The Class 1 E busses of each unit must be energized in order to provide preferred or standby power to the safety-related loads of each unit.

Standby Power Supply [EllS Code: EK]

The standby power supply for each safety-related load group consists of one emergency diesel generator (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.

NRC FORM 366A (7-2001)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (6.24)

LICENSEE EVENT REPORT (LER)

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE YEAR I SEQUENTAL I REVISION Palo Verde Nuclear Generating Station 05000529 NUMBER NUMBER 3 OF 7 Unit 12005 001 00

17. NARRATIVE (If more space is required, use additional copies of NRC Form 366A)

3.

INITIAL PLANT CONDITIONS:

On February 6, 2005, at approximately 22:19 Mountain Standard Time (MST), Unit 1 was in Mode 1 (POWER OPERATION), operating at approximately 100 percent power.

There were no major structures, systems, or components that were inoperable at the start of the event that contributed to the event. There were no failures that rendered a train of a safety system inoperable and no failures of components with multiple functions involved.

4.

EVENT DESCRIPTION:

On February 6, 2005, at approximately 22:19 Mountain Standard Time (MST) a valid actuation of the Palo Verde Nuclear Generating Station Unit 1 Train 'B' Emergency Diesel Generator (EDG) occurred as a result of under-voltage on its respective safety bus (PBB-S04). EDG 'B' started and loaded as designed to energize PBB-S04. The loss of power to the safety bus was the result of a fault associated with 13.8KV breaker NAN-S06J cubicle which caused breaker NAN-S06H (normal power supply), to trip open on over-current. This action resulted in the de-energization of NAN-S06, NAN-S04, and PBB-S04. Circuit breaker NAN-SO6J (EOF & TSC Bldg power supply) was also found in an open state.

The PVNGS Fire Department and Auxiliary Operators responded to a report of smoke and upon arrival found no fire. The Fire Department verified the fire was completely extiriguished and there were no extensions (secondary fires).

Unit 1 entered Technical Specification LCO 3.8.1, Condition 'A', for one (of two) required offsite circuits inoperable. Various other Technical Specifications LCO's were momentarily entered and exited for PBB-S04 being de-energized for approximately 7 seconds. No Emergency Plan declaration was made and none was required. Unit 1 was.at approximately 100% power, at normal operating temperature and pressure prior to and following the EDG actuation. No other ESF actuations occurred and none were required. No major equipment was inoperable prior to the event that contributed to the event.

NRC FORM 366A (7-2001)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (64CO4)

LICENSEE EVENT REPORT (LER)

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE YEAR SEQUENTAL REVISION Palo Verde Nuclear Generating Station I

NUMBER NUMBER nit 205000529 4

F0 7 Uni 12005 001 00

17. NARRATIVE (If more space is required, use additional copies of NRC Form 366A)

5.

ASSESSMENT OF SAFETY CONSEQUENCES:

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 condition would not have prevented the fulfillment of any safety function and did not result in a safety system functional failure as defined by 1 OCFR50.73(a)(2)(v).

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.

6.

CAUSE OF THE EVENT:

The direct cause of the 1 E-NAN-S06 power failure was an electrical fault in cubicle 'J' within the line side primary disconnect assembly (rosette) compartment above the circuit breaker. This electrical fault initiated as a 'C" phase to ground fault and transitioned to a three phase to ground fault. The electrical fault was terminated by the normal bus feeder circuit breaker 1 ENANS06H opening due to protective relaying. Most probable root/contributing causes for the direct cause are: contamination with tracking over the exterior of the rosette, high resistance bushing-finger connection within the rosette, rosette cracked porcelain, water intrusion or a combination of these.

7.

TRANSPORTABILITY:

Circuit breaker 1ENANS06J is located in an outdoor 13.8 KV GE switchgear enclosure.

There are the following similar GE switchgear enclosures at PVNGS:

• Twelve (4/unit) outdoor 13.8 KV Non-lE switchgear enclosures (E-NAN-S0314/516);

37 breaker cubicles.

• Six (2/unit) indoor 13.8KV Non-1E switchgear enclosures (E-NAN-S01/2); 66 breaker cubicles.

NRC FORM 366A (7-2001)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (Q2004) '

LICENSEE EVENT REPORT (LER)

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE YEAR SEQUENTAL I REVISION Palo Verde Nuclear Generating Station 05000529 NUMBER NUMBER 5OF7 Unit 2005 --

001 00

17. NARRATIVE (If more space is required, use additional copies of NRC Form 366A)

Six (2/unit) indoor 4.16 KV 1 E switchgear enclosures (E-PBANB-S03/4); 81 breaker cubicles.

Six (2/unit) indoor 4.16 KV Non-1E switchgear enclosures (E-NBN-SOl/2); 51 breaker cubicles.

Note, indoor 13.8 KV QAG switchgear enclosure AE-NAN-S07 has a different bus structure and the five respective vacuum circuit breakers are racked in horizontally; hence initial indications are this failure is not transportable to AENANS07.

Contamination with tracking - Inspection of other bus side primary disconnect assemblies (rosettes) in 1 ENANS06 cubicles and the line (load) side rosettes in cubicle 1 ENANS06K found reasonably clean conditions (low contamination to contribute to tracking) and no degraded conditions. The outdoor enclosures are the most challenged by dust and are cleaned each refueling cycle. Based on the condition of the rosettes inspected in 1 ENANS06, contamination is not deemed an immediate transportability concern.

High resistance connection - Industry operating experience (IOE) consolidated and reviewed found very few incidence of primary disconnect assembly (rosette) failure. The applicable IOE identified high resistance overheating of the connection between primary disconnect assembly (rosette) fingers and circuit breaker bushing due to old hardened grease, misalignment and missing silver plating. The fingers within the interior of the bus and line rosettes in the outdoor 13.8 KV switchgear are inspected and cleaned each refueling cycle as per maintenance procedure 32MT-9ZZ91. Proper rosette finger and circuit breaker stab contact is validated during circuit breaker alignment as per maintenance procedure 32MT-9ZZ33. Based on these procedure actions, there is reasonable assurance of a good circuit breaker bushing to rosette fingers connection; therefore rosette high resistance connections are not deemed an immediate transportability concern. Industry operating experience indicates thermography may be utilized to find primary disconnect high resistance by detecting the related heat on an adjacent sheet metal compartment wall/cover.

NRC FORM 366A (7-2001)

I

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (6%-2gw4)

LICENSEE EVENT REPORT (LER)

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE YEAR I SEQUENTAL REVISION Palo Verde Nuclear Generating Station I

NUMBER NUMBER Unit 1 05000529 6 OF 7 2005 --

001 00

17. NARRATIVE (If more space Is required, use additional copies of NRC Form 366A)

Cracked porcelain - Industry operating experience (IOE) consolidated and reviewed found no incident of primary disconnect assembly (rosette) porcelain failure. If rosette cracked porcelain is the most probable cause for this failure; the probability of more rosettes with porcelain cracked at PVNGS is very low based on no failures of this type identified during IOE. Therefore rosette cracked porcelain is not deemed an immediate transportability concern.

Water Intrusion - No initial evidence of water was found; nor was rain a challenge to the switchgear enclosure just prior to or during the event. Additionally, rain occurred during restoration of the switchgear enclosure; no water intrusion into the circuit breaker cubicles occurred during restoration of the switchgear enclosure.

8.

CORRECTIVE ACTIONS:

The following maintenance/repairs activities were completed prior to 1 ENANS06 being re-energization:

CMWO 2775016 - primary disconnect assembly (rosette) inspection, bus inspection, circuit breaker H & K inspect/adjust, circuit breaker alignment verification, control wiring replacement.

CMWO 2755660 - 52Y anti-pump relay replacement on circuit breaker 1 ENANS06H.

CMWO 2755688 - 52Y anti-pump relay replacement on circuit breaker 1 ENANS06K.

DFWO 2776409 - 1 ENANS06 bus repair in cubicles H, J and K; cubicle J control wiring isolation.

T-Mod 2775284 - EOF & TSC temporary power from 1 ENANS05K.

T-Mod 2776424 - Control wiring and line side bus connections to cubicle 1 ENANS06K.

The following condition was evaluated after 1 ENANS06 being re-enerqizated:

DFWO 2782601 - Conditional Release for T-Mod 2775284 (EOF & TSC temporary power from 1 ENANS05K) without protective 1 ENANS06J trip inputs.

NRC FORM 366A (7-2001)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (62D04) i-'

LICENSEE EVENT REPORT (LER)

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE YEAR SEQUENTAL REVISION Palo Verde Nuclear Generating Station I

NUMBER NUMBER Unt105000529 7OF 7 Unit 2005-001 00

17. NARRATIVE (If more space is required, use additional copies of NRC Form 366A)

9.

PREVIOUS SIMILAR EVENTS:

Switchyard and EHV grid events that have affected PVNGS have been reported in LERs 50-528/2004-006-00, 50-529/2004-003-00 and 50-530/2003-004-00. However, these previous events or conditions did not involve the same underlying concern or reason as this event, such as the same root cause, failure, or sequence of events.

There have been no previous similar events in the past three years that had a similar failure mechanism or that should have prevented this event from previously implemented corrective actions.

NRC FORM 366A (7-2001)