ML17304A196

LER 88-015-00:on 880512,automatic Actuation of Reactor Protection Sys Occurred.Power Supply Found to Be Varying in Amplitude Intermittently Which Could Cause Varying Removal & Reinstatement of Buck & Boost voltage.W/880606 Ltr

ML17304A196
Person / Time
Site:	Palo Verde
Issue date:	06/06/1988
From:	Haynes J, Shriver T ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
192-00381-JGH, 192-381-JGH, LER-88-015, LER-88-15, NUDOCS 8806140442
Download: ML17304A196 (14)

Text

v REGULA )Y INFORMATION D I STR I BUT I(. SYSTEM ( R I DS )

ACCESS'ION NBR: 8806140442 DOC. DATE: 88/06/06 FACIL: STN-50-528 Palo Verde Nuclear Stations Unit NOTARIZED: NO ii DOCKET Arizona Publi 05000528 I

AUTH. NAME, AUTHOR AFFILIATION SHRIVER. T. D. Arizona Nuclear Power ProJect (Formerly Arizona Public Serv HAYNESI J. G. Arizona Nuclear PolUer ProJect (Formerly Arizona Public Serv REC IP. NAME RECIPIENT AFFILIATION

SUBJECT:

LER 88-015-00: on 880512'utomatic actuation oF reactor protection sos occurred. Poeer supply Found to be varying in amplitude intermittently which could cause varying removal 5 reinstatement oF buck 8c boost voltage. W/880606 ltr.

DISTRIBUTION CODE: IESBD COPIES RECEIVED: LTR Q ENCL g. SIZE:

TITLE: 50. 73 Licensee Event Report (LER)i Incident Rpti etc.

NOTES: Standardized plant. 05000528 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1 LICITRA> E 1 1 DAVISI M 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 AEOD/DOA 1 1 AEOD/DSP/NAS 1 1 AEOD/DSP/ROAB 2 2 AEOD/DSP/TPAB 1 1 ARM/DCTS/DAB 1 DEDRO 1 1 NRR/DEBT/ADS 7E 1 0 NRR/DEST/CEB 8H 1 NRR/DEST/ESB 8D 1 1 NRR/DEST/ICSB 7 1 1 NRR/DEST/MEB 9H 1 NRR/DEST/MTB 9H 1 1 NRR/DEST/PSB 8D 1 NRR/DEST/RSB 8E 1 1 NRR/DEBT/SGB 8D 1 1 NRR/DLPG/HFB 10 .1 1 NRR/DLPG/GAB 10 1 1 NRR/DOEA/EAB 11 1 1 NRR/DREP/RAB 10 1 1 NRR/DREP/RPB 10 2 2 NRIV-DRCN- - IB 9A 1 1 NUDOCS-ABSTRACT 1 1 CREE~ OE 1 1 RES TELFORDi J 1 1 RES/DE/EIB 1 RES/DRPS DEPY 1 1 RGN5 FILE 01 1 EXTERNAL: EGSG WILLIAMS>S 4 4 FORD BLDG HOYLE A 1 1 H ST LOBBY WARD 1 1 LPDR 1 1 NRC PDR 1 NSIC HARR IS> J 1 1 NSIC NAYS> G 1 1 NOTES:

TOTAL NUMBER OF COPIES REQUIRED: LTTR 47 ENCL 46

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NRC Form 366 U.S. NUCLEAR AfGULATOAYCOMMISSION IS 63)

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MONTH YEAR ispp SSQUENTIAL REVISKyv FACILITYNAMES DOCKET NUMBER(S)

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NAME TELEPHONE NUMBER AREA CODE Timothy D. Shriver, Compliance Manager COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13) 602393 2521 CAUSE SYSTEM COMPONENT MANUFAC TVRER REPORTABLE TO NPRDS ggg4g$ 4ysYk.: CAUSE SYSTEM COMPONENT MANUFAC. EPORTABLE oO~pif jPQ TVRER J X X999 N Wkk4>>!

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SVPPLfMENTAL REPORT EXPECTED (14) MONTH DAY YEAR EXPECTED SUBMISSION YES /I/ yn, complsrs fXPE CTE D SUdMISSIOII DA TE/ NO DATE (15I AssTAAGT /Limit to I400 rpscn. /.i., sppronmirsly IUriin tinpli Ipsci typiwntrin linn/ (16)

At 1315 NST on Hay 12, 1988, Palo Verde Unit 1 was in Mode 1 (POWER OPERATION) at approximately 91% power when an automatic actuation of the Reactor (RCT)(AC) Protection System (RPS)(JC) occurred. Surveillance test 36ST-9SB04 (Plant Protective System (PPS)(JC) Functional Test-RPS/Engineered Safety Feature Actuation Systems (ESFAS)(JE)) was in progress when the reactor (RCT)(AC) trip occurred.

Performance of 36ST-9SB04 involves a separate power supply (JX)(JC) utilized only during testing to "hold" the bistable and matrix relays from actuation during the test. The power supply was found to be varying in amplitude intermittently which would cause varying removal and reinstatement of the buck and boost voltage. This caused the trip of the RAH and "DA Reactor Trip Circuit Breakers.

Immediate corrective action was to replace the power supply with a properly operating power supply. A precaution was added to 36ST-9SB04 to ensure that the test performer is aware that the power supply may exhibit instabilities as indicated by lamp "flickering".

8806140442 880606 PDR ADOCK 05000528 8 PDR NRC form 366

NRC Fosm 3SIA (9831 U.S. NUCLEAR REOULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVEO OM8 NO 1150 0(04 EXPIRES: 8/31/88 FACILITY NAME (11 OOCXET NUMSER (21 LER NUMSER (81 ~ AOE (31 SYoS SSOUSNTIAL @~1 A(VISION NUM I SI NUllOSA Palo Verde Unit 1 o s o o o 5 2 8 8 8 0 1 5 0 0 0 2 OF 0 5 TEXT /// moss sooco ie /oqoswf. s/Ps /RM/'oos/HRC fo/m 388A's/ ((TI I. DESCRIPTION OF WHAT OCCURRED:

A. Initial Conditions:

At 1315 MST on May 12, 1988, Palo Verde Unit 1 was in Mode 1 (POWER OPERATION) at approximately 91% power when an automatic actuation of the Reactor Protection System (RPS)(JC) occurred. Surveillance test 36ST-9SB04 (Plant Protective System (PPS)(JC) Functional Test-RPS/Engineered Safety Feature Actuation Systems (ESFAS)(JE)) was in progress when the reactor (RCT)(AC) trip occurred.

B. Reportable Event Description (Including Dates'nd Approximate Times of Major Occurrences):

Event Classification: Automatic Actuation of the Reactor Protection System At 1315 HST on May 12, 1988, Palo Verde Unit 1 was operating at approximately 91% power. Instrument and Control Technicians were performing portions of 36ST-9SB04 as a retest .prior to declaring channel UC"'og power (IG) operable. The log power channel was taken out of service to perform troubleshooting in an attempt to determine why channel "CU did not respond to an increase in neutron flux during plant start-up as did channels RA", "BR and "D".

Reactor Trip Breakers (BKR)(JC) "A" and "DU opened, resulting in a reactor trip. As the Control Element Assemblies (CEA)(AA) fell into the core (AC), the Core Protection Calculators (CPC)(CPU) generated penalty factors due to multiple CEA deviations. These penalty factors were large enough to initiate Low Departure from Nucleate Boiling Ratio (DNBR) trips on .all four CPCs. At that point Reactor Trip Breakers RB" and "C" opened. The Assistant Shift Supervisor performed a diagnostic evaluation in accordance with the approved procedure, 41EP.-1ZZ01 (Emergency Operations), and diagnosed the event as an uncomplicated reactor trip. The plant was stabilized in Mode 3 (HOT STANDBY) within approximately 5 minutes.

Performance of the matrix relay (RLY)(JC) tests in 36ST-9SB04 involves a separate power supply (JX)(JC) which is utilized only during testing to "hold" the bistable and matrix relays from actuation 4AC S 0AM 3(OA I9 83i

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NRC Form 3SSA (a831 U.S, NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVEO OMS NO 3150 0(05 EXPIRES(813(/SS FACILITY NAME (11 QOCKET NUMSER (11 LER NUMSER (8) ~ AGE (3)

POK SEGVENTrAL @w rl5 v r5 ro N 6XO NUM 5 R ..SM NVM TA Palo Verde Unit TEXT (ifmore N>>co 1 o s o o o 5 2 8 8 8 0 1 50 0 0 3oF05 ir ooewerE rroo orFpooon>>F ArIIC Form 3(5(ASF (\TI during the test. Actuation of the Hold Pushbutton applies a "boost" voltage to the hold coils (CL) of the selected matrix relays. This boost voltage will hold the relays in their energized position during the deactivation of the primary matrix relay coils. The selected parameter bistable trip relays will drop out due to the "buck" voltage applied as the channel trip select switch (HS) is rotated through each of the parameters. The test requires a "boost" voltage to hold the matrix relays during deactivation of the bistable relays and to prevent a matrix initiation. During this event the power supply perturbations caused the boost voltage to become unstable allowing the matrix relays to deenergize resulting in the channel RA" and RDR trip initiation.

During the reenactment of 36ST-9SB04 only one reactor trip breaker, RD", opened. It was determined that this verified the cause of the reactor trip due to the intermittent failure characteristics discovered to be present in the power supply. The power supply was found to be varying in amplitude intermittently which would cause varying removal and reinstatement of the buck and boost voltages. In the trip event, this caused the trip of both RAR and RDR reactor trip circuit breakers. Due to the spurious nature of power supply instabilities, during the reenactment only the RDR breaker opened.

C. Status of structures, systems, or components that were inoperable at the start of the event that contributed to the event:

No other structures, systems, or components were inoperable at the start of the event that contributed to the event other than log power channel RCR as discussed previously.

D. Cause of each component or system failure, if known:

An Engineering Evaluation Request has been initiated to perform a root cause of failure analysis on the power supply.

E. Failure known:

mode, mechanism, and effect of each failed component, if The power supply is utilized during testing only and is not in the circuit during normal operations. The power supply output was varying in amplitude intermittently. This caused the "buck" and "boost" voltages to vary intermittently thereby causing a trip initiation of the RAR and RDR Reactor Trip Circuit Breakers.

For failures of components with multiple functions, list of systems or secondary functions that were also affected:

Not applicable - the power supply does not have multiple functions.

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NRC form 34iA 19831 U.S. NUCLEAR RECULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMS NO 3148 CIDe EXPIRES> 8/3(/88 FACILITY NAME (11 DOCKET NUMSER (1)

LER NUMSER (41 PACE LTI pe>> SeoveNT>AL (RT

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6, For failure that rendered a train of a safety system inoperable, estimated elapsed time from the discovery of the failure until the train was returned to service:

Not applicable - no safety systems were rendered inoperable.

H. Method of discovery of each component or system failure or procedural error:

Troubleshooting in accordance with an approved work control document identified the power supply failure.

I, Cause of Event:

The power supply was found to be varying in amplitude intermittently which would cause varying removal and reinstatement of the buck and boost voltages. This caused the trip of both "A" and "D" Reactor Trip Circuit Breakers.

J. Safety System Response:

Reactor Protection System trip.

There were no other Engineered Safety Feature (ESF)(JE) or RPS actuations and none were required.

K. Failed Component Information:

Manufacturer - Todd Products Corporation Model Number - SW 12-15 II. ASSESSMENT OF THE SAFETY CONSE(UENCES AND IMPLICATIONS OF THIS EVENT:

As described above, the reactor tripped as designed and all safety responses necessary to place the plant in a stable condition functioned properly. There were no ESF actuations and none were required. Based on the above, this event had no impact on the health and safety of the public.

I I I. CORRECTIVE ACTIONS:

A. Immediate:

The faulty power supply was replaced with a properly operating power supply. A precaution was added to 36ST-9SB04 to ensure tha't the test performer is aware that the power supply may exhibit instabilities as indicated by lamp "flickering".

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'CENSEE NAC form 3SEA 19831 EVENT REPORT (LER) TEXT CONTINUATION U.S, kUCLEAR AEPULATOAY COMM/SSIP/I APPAPVEO OMS HO EXPIRES: 8/31/88 3150M/Pi FACILITY /IAME III OOCKET NUMSER ITI LER MUMSER IS) ~ AOE 131 ssovsr/T/AL rLor rrsvrsrPrr

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B. Action to Prevent Recurrence:

Previous indications of potential Todd power supply instabilities has prompted the initiation of a Design Change Package (DCP) to replace Todd power supplies with more reliable power supplies. This DCP was not a result of this event; however, the DCP will be expedited in an attempt to prevent recurrence of this event.

IV. PREVIOUS SIMILAR EVENTS:

No previous similar events have been reported.

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Arizona Nuclear Power Project P.O. BOX 52034 ~ PHOENIX. ARIZONA 85072-2034 192-00381-JGH/TDS/JEM June 6, 1988 U. S. Nuclear Regulatory Commission NRC Document Control Desk Washington, D.C, 20555

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit 1 Docket No. STN 50-528 (License No. NPF-41)

Licensee Event Report 88-015-00 File: 88-020-404 Attached please find Licensee Event Report (LER) No. 88-015-00 prepared and submitted pursuant to 10CFR 50.73. In accordance with 10CFR 50.73(d), we are herewith forwarding a copy of the LER to the Regional Administrator of the Region V office.

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

Very truly yours, t/4 J.

~~

G. Haynes Vice President Nuclear Production JGH/TDS/JEM/kj Attachment cc; 0. M. DeMichele (all w/a)

E. E. Van Brunt, Jr.

J. B. Martin T. J. Polich E. A. Licitra A. C. Gehr

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