ML17305B724

Special Rept 3-SR-91-006:on 910829,Class 1E Inverter C Failed During Maint Evolutions.Caused by Momentary Ground on 120-volt Channel C Vital Ac Electrical Bus.Inverter Returned to Svc & Bus Reenergized from Associated Inverter

ML17305B724
Person / Time
Site:	Palo Verde
Issue date:	09/03/1991
From:	James M. Levine ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
192-00737-JML-T, 192-737-JML-T, 3-SR-91-006, 3-SR-91-6, NUDOCS 9109110005
Download: ML17305B724 (7)

Text

I ACCELERATED DISTRIBUTION DEMONSTION SYSTEM C

REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9109110005 DOC.DATE: 91/09/03 NOTARIZED: NO DOCKET FACIL:STN-50-530 Palo Verde Nuclear Station, Unit 3, Arizona Publi 05000530 AUTH;NAME AUTHOR AFFILIATION

-LEVINE,J.M. Arizona Public Service Co.. (formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Special Rept 3-SR-91-006:on 910829,Class 1E inverter C failed during maint evolutions. Caused bybus.Inverter momentary ground on 120-volt Channel C vital ac electrical returned to svc & bus reenergized from associated inverter. D DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR l ENCL TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt,- etc.

J SIZE: ~

NOTES:Standardized plant. 05000530 A

RECIPIENT COPIES RECIPIENT COPIES D ID CODE/NAME LTTR ENCL ~

ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD.5 PD 1 1 D TRAMMELL,C 1 1 THOMPSON,M 1 1

(

INTERNAL: ACNW 2 2 ACRS 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB10 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB8H3 1 1 /D~S SPLB8D1 1 1 NRR/DST/SRXB 8E 1 1 EG F 02 1 1 RES/DSIR/EIB 1 1 RGN FILE 01 1 1 EXTERNAL: EG&G BRYCE,J.H 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHY,G.A 1 1 NUDOCS FULL TXT 1 '

NSIC POORE,W. 1 1 NOTES: 1 1 D

A D

D NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCF, O'ASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 20079) TO IiLIiIINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED: LTTR 35 ENCL 35

Arizona Public Service Company PALO VERDE NUCLEAR GENERATING STATION P.O. BOX 52034 ~ PHOENIX. ARIZONA 85072-2034 JAMES M. LEVINE 192-00737-JML/TRB/KR VICE PRESIDENT NUCLEAR PRODUCTION September 3, 1991 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Mail Station Pl-37 Washington, D.C. 20555

Dear Sirs:

Subj ect: Palo Verde Nuclear Generating Station (PVNGS)

Unit 3 Docket No. STN 50-530 (License No. NPF-74)

Report 3-SR-91-006 'pecial File: 91-020-404.

Attached please find Special Report 3-SR-91-006 prepared and submitted pursuant to Emergency Plan Implementing Procedure (EPIP-03). This report discusses a condition requiring the declaration of a NOTIFICATION OF UNUSUAL EVENT due to a reactor shutdown required by Technical Specifications.

If you have any questions, please contact T. R. Bradish, Compliance Manager at (602) 393-2521.

Very truly yours, JML/TRB/KR Attachment cc: ~ W. F. Conway (all with attachment)

J. B. Martin D. H. Coe A. C. Gehr A. H. Gutterman 9109110005 910903 PDR ADOCK 05000530 5 PDR

0 Palo Verde Nuclear Generating, Station Unit 3 Notification of Unusual Event Docket No. 50-530 License No. NPF-74 Special Report 3-SR-91-006 This Special Report is being submitted pursuant to Emergency Plan Implementing Procedure (EPIP-03), "Notification of Unusual Event Implementing Actions" to report a condition which required the declaration of an Unusual Event for Palo Verde Unit 3 at 2015 MST on August 30, 1991. The Unusual Event was terminated at 0132 MST on August 31, 1991..

On August 29, 1991, at approximately 2032 MST, Palo Verde Unit 3 was operating at approximately 87 percent power in Mode 1 (POWER OPERATION) when the Class 1E Inverter C failed during maintenance evolutions due to a momentary ground on the 120-volt Channel C Vital A.C. electrical bus. Technical Specification (TS) 3.8.3.1 Limiting Condition for Operation (LCO) requires that:

"The following electrical busses [120-volt Channel C Vital A.C.

bus) shall be energized in the specified manner [from its associated inverter connected to the D.C. Channel C bus) with tie breakers open between redundant busses within the unit."

TS 3.8.3.1 ACTION b requires that:

"with one A.C. vital bus either not energized from its, associated inverter, or with the inverter not connected to its associated D.C. bus: (1) reenergize the A.C. vital bus within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 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 /> and (2) reenergize the A.C.

vital bus from its associated inverter connected to its associated D.C. bus within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 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 />."

At approximately 2032 MST, TS 3.8.3.1 ACTIONs b(1) and b(2) were entered. TS 3.8.3.1 ACTION b(l) was immediately exited when the 120-volt, Channel C Vital A.C. electrical bus successfully auto-transferred to the Voltage Regulator following the inverter failure. However, efforts to restore the inverter to operable and reenergize the A.C. vital bus from the inverter within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> were not successful.

Emergency Plan Implementing Procedures require the declaration of an Unusual Event for a reactor plant shutdown required by TS. By 2016 MST, on August 30, 1991, the appropriate state and local agencies were notified of the conditfon requiring the declaration of an Unusual Event (i.e., shutdown required by TS).

At approximately 2023 MST on August 30, 1991, the Nuclear Regulatory Commission (NRC) Operations Center was notified.

At approximately 2330 MST on August 30, 1991, Unit 3 Control Room personnel commenced a plant shutdown as required by TS 3.8.3.1 ACTION b(2). At

NRC Document Control Desk Special Report 3-SR-91-006 Page 2 approximately 0119 MST on August 31, 1991, the reactor was shut down in accordance with the shutdown procedure. At'pproximately 0132 MST on August 31, 1991, the Unusual Event was terminated in accordance with EPIP-03. By 0142 MST on August 31, 1991, the appropriate state and local agencies and the NRC Operations Center were notified of the termination of the Unusual Event.

Following corrective maintenance, at approximately 1902 MST on August 31, 1991, TS 3.8.3.1 ACTION b(2) was exited when the Class lE Inverter C was returned to service and the 120-volt Channel C Vital A.C. electrical bus was reenergized from its associated inverter. The ACTION requirement to be 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 /> was no longer necessary.

Further investigation into the circumstances surrounding this event is being performed in accordance with the PVNGS Incident Investigation Program.