ML20012B433

LER 90-001-00:on 900206,reactor Tripped as Result of Loop Low Flow Condition Following Trip of Reactor Coolant Pump a, Causing Feedwater Isolation & Auxiliary Feedwater Actuation Signals.Caused by High Differential current.W/900308 Ltr

ML20012B433
Person / Time
Site:	Wolf Creek
Issue date:	03/08/1990
From:	Bailey J, Mike Williams WOLF CREEK NUCLEAR OPERATING CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-001, NO-90-0075, NUDOCS 9003140392
Download: ML20012B433 (4)

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L' I W4)NUCLEAROPERATING John A, Beney .

vise Preensent - )

Nuclear operemons 1

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March 8, 1990 >

1 e s NO 90-0075 .

U. S.. Nuclear Regulatory Commission ATTN: Document Control-Desk

-Hail: Station P1-137-

-Washington, D.-C.-20555-Subjects. Docket No. 50-482:= Licensee Event Report 90-001 00

",, Gentlemen:-

The -attached Licensee Event Report (LER) is. submitted pursuant to 10 CPR d

+ 50.73'.(a)!(2)-(iv) concerning an Engineered Safety Features actuation, q

Very truly:yours, 7

, L, y

d John A. Bailey.

,' Vice President Nuclear Operations  :

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Attachment

-ccs.E. J. Holler (NRC), w/a I L R. D. Martin (NRC), w/a i f D. V. Pickett (NRC), w/a .1 p M. E. Skow (NRC), w/a j%S33SoEE d['

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.. , .i P.O. Box 411/ Burtmoton, KS 66839 / Phone: (316) 364-8831 /1 An Equal opportunny Ernpeoyer uf/HCNET I k j

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l 9 ACittiv NAME fu DOCEtt NUMetR (21 PAGE 53i Wolf Creek Generating Station 0 l 5 l 01 o l 0 l 418 l 2 1 l0Fl0 13 Reactor Trip As A Result Of Reactor Coolant Pump Trip Caused By An Indicated High Differential Current Condition SVENT DATE (S) LIR NUM81R (Gl REPORT DAf t til OTHth 7 ACILITit$ INVOLVED lei l MONTH day vtAn vtAR 56$$$^4 [yffy MONTH OAv vtAR ' AC' Liv s hauts DOCKt1 NUMDt'ti8 016l0l0l0 1- l l 0h 0l2 0l6 9 0 9l0 0l 0l1 0l 0 0 l8 9l0 o isio t o i ci i i THIS REPORT 88 $USMITit0 PURSUANT TO THE REQUlmtMENTS OF 10 Cf R $ (Chece on. or mory of fee tottemng) till

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On February 6,1990, at approximtely 0906 CST, a Reactor trip occurred frun 100 percent power as a result of a loop low flow condition following a trip -

of Reactor Coolant Punip (RCP) "A". In aMition, a Feedwater Isolation Signal, an Anviliary Feedwater Actuation Signal, and a Steam Generator Blowdown and Sample Isolation Signal actuations occurred as designed. All required safety related equignant perfomed as designed. l

- 'Ihe trip of RCP "A" ms caused by an indicated high differential current on l the "A" phase. 'Ihe differential current relay as tested and no I l abnormalities were detected. Extensive troubleshooting efforts were L

unsuccessful in identifying the root cause for the relay actuation.

Following installation of temporary ramtvlarst to monitor inputs to the i

relay, RCP "A" ma restarted at approximately 1630 CST. No significant almormalities associated with punp operation were detected and the next day, ,

! on February 7, 1990, the unit e s restarted, entering Mode 2, Startup, at l L 1631 CST.

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I OF MANAGEMENT AND OUDGEt, WASHINGTON. DC 70603.

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INDGUCTIN ,

On February 6, 1990, at approximately 0906 CST, a Reactor (AB-RCT] trip occurred fran 100 percent power following a trip of Reactor Coolant Punp (RCP) [AB-P] "A". In addition, a Feedwater Isolation Signal ( NIS), an Auxiliary Feedwater Actuation Signal (AFAS), and a Steam Generator Blowdown and Sanple Isolation Signal (SGBSIS) actuations occurred as designed. %e required safety related equignant perfomed as designed. %is event is being reported pursuant to 10CFR50.73(a)(2)(iv) as automatic actuations of Engineered Safety Features (ESF) (JE) equipnent.

DESCRIITIW T EVI9fIS Prior to the trip, the unit was in Mode 1, Power Operation, at 100 percent power, with the Reactor Coolant System (RCS) (AB) at normal operating tanperature and pressure. Feedwater flow was being provided by Main Feedwater Punps (MPP) "A" and "B" (SJ-P) in autanatic control. Each Main Feedwater Control Valve (SJ-FCV) was open and in autanatic control.

Containment Cooling Fan "D"-[BK-FAN) was out of service for breaker maintenance as allowed by the plant's %chnical Specifications.

On February 6, 1990, at 0906 CST, RCP "A" tripped as a result of an indicated high differential current on the "A" phase. Because the unit was operating above 48 percent power (the P-8 pennissive), the resultant loop

, low flow condition resulted in a Reactor trip and Main Turbine [TA 'IRB]

l trip. FWIS, AFAS and SGBSIS actuations occurred as expected. Following the

! trip, the Control Roan operators verified proper operation of safety systens I

and took actions to stabilize the plant at normal operating temperature and  ;

i pressure in accordance with procedures DG E-0, " Safety Injection," and DG ES-02, " Reactor Trip Response". At approximately 0930 CST, the operators  ;

transitioned to normal operating procedure GEN 00-005, " Plant Shutdown fran 20% Minimum Ioad to Ibt Standby".  ;

he handswitch for RCP "A" was placed in " pull-to-lock" and troubleshooting l efforts were initiated to determine the cause of the RCP motor trip. A visual inspection of RCP "A" identified no almonnalities. %e notor was ir%euxd and bridged with satisfactory results, i.e., there were no indications of notor degradation. We differential current relay was checked and no problems were identified. Readings fran the current transfonners associated with the differential current relay were obtained.

RCP "C" was secured at 1541 CST to obtain current transformer readings for i

canparison with those obtained fran RCP "A". W ere were no significant I discrepancies between the two sets of readings.

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• OF MANAGEMENT AND DVDGET WASHINGTON. DC 70603

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W e results of these troubleshooting efforts were discussed with the RCP l supplier, Westinghouse Electric Corporation. During the discussion, it was l concluded that there were no further troubleshooting activities that could be performed to identify the root cause of the RCP trip. It was further concluded that a restart of RCP "A" coilld be attanpted without a substantial risk for pung damage.  !

Recorders to monitor all three phases of inputs to the differential current relays on RCP ".A" were installed and RCP "A" was restarted at approximately 1630 CST. No abnormalities associated with the RCP's operating characteristics were detected. Oil was added to RCP "C" and it was restarted at 2254 CST.

%e "D" Containment Cooling Fan was restored to service at 0121 CST on February 7, 1990. In the absence of any abnormal irrlications frtzn RCP "A",

the unit was restarted, entering Mode 2, Reactor Startup, at 1631 CST on February 7.

HOT CAUSB AIO 00RRECTIVE ACTICBE We extensive troubleshooting efforts were unsuccessful in identifying the root cause of the trip of RCP "A". It is planned to leave the temporary ramrrlarm installed on the differential current relay inputs until the

& ng irefueling outage which will begin in March, 1990.

During the refueling outage, it is planned to Ks:ryr and perform a current test on the current transfouners, to inspect all the connections in the circuit, and, as a precautionary measure, to replace the differential current relay. Additional activities planned during the refueling outage include a check of the capacitors associated with RCP "A", and another bridge and megger test of the RCP "A" motor.

ADDITI@AL INF@MATI@

All safety systens functioned p.vrufly during this event, thus preventing developnent of conditions that could have posed a threat to the health and safety of the public.

Were have been no previous similar occurrences.

N (C Form 386A (6493

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