ML20046B898

LER 93-013-00:on 930629,high Pressure Core Spray Pump Failed to Start & Run During Surveillance Test Due to Failed Overfrequency Relay.Relay Tested & Installed in Switchgear. W/930729 Ltr

ML20046B898
Person / Time
Site:	River Bend
Issue date:	07/29/1993
From:	Booker J, Lorfing D GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-013, LER-93-13, RBG-38805, NUDOCS 9308090001
Download: ML20046B898 (5)

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GULF STATES UTILXTIES COMPANY  ;

fovea MND LTA? ION POST OrflCE 80 A 220 ST TRANC6SvtLLE. LOUISIAN A 70775  ;[

AHf A CODE f>O4 6% 6'M4 .34fi B651 July 29, 1993 j RBG- 38805 File Nos. G9.5, G9.25.1.3 U.S. Nuclear Regulatory Commission ['

Document Control Desk Washington, D.C. 20555 Gentlemen:

River Bend Station - Unit I  !

Docket No. 50-458 i

4 Please f'md enclosed Licensee Event Report No.'93-013 for River Bend Station -

Unit 1. This repon is submitted pursuant to 10CFR50.73. I i

Sincerely, l

J. E. Booker Manager - Safety Assessment and Quality Verification ,

River Bend Nuclear Group ,

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cc: U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 NRC Resident Inspector P.O. Box 1051 St. Francisville, LA 70775 INPO Records Center  :

700 Galleria Parkway l Atlanta, GA 30339-5957 Mr. C.R. Oberg ,

Public Utility Commission of Texas 7800 Shoal Creek Blvd., Suite 400 North Austin, TX 78757 Department of Environmental Quality -

Radiation Protection Division  !

P.O. Box 82135 l Baton Rouge, LA 70884-2135 ATTN: Administrator P

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[idRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 e sa EXPIRES 5/31/95 ESTIMATED RURDEN PER AESPONSE TO COMPLY WITH THIS LICENSEE EVENT REPORT (LER) ECT"Ms "EoS$'a'EnDTEuaTEiO""I,N5 M AND RECORDS MANA3EMENT BHANCH (MNBB 7714), US. NLICLFAR HEGULATORY COMMISSION. WASH!NGTON, DC 200%-0001, AND TO THE PAPERWORK REDVCTION PROJECT (3150 4104, OrFICE OF (See reverse for required number of digits / characters for each block) MANAGEMENT AND BUDGET, WASHINGTON, DC 20503. j FACILITY NAME (1) DOCKET NUMBER (2)

RIVER BEND STATION 05000 458 PAGE p) 3 3 or

=W TRIP OF HIGH PRESSURE CORE SPRAY PUMP BREAKER FOLLOWING START DUE TO FAILED OVER FREQUENCY RELAY EVENT DATE (5) LER NUMBER (6 > REPORT NUMBER (7) OTHER FACILITIES INVOLVED (e)  !

MONTH DAY YEAF YEAR MONTH DAV YEAR r 0 j OG 29 93 93 - 013 00 07 29 93 ]50O OPERATING y THIS REPORT IS SUBMITTED PURSUANT To THE REOUIREMENTS OF to CFR i: (Check one or more) (11) p MODE (9) 20 402(b) 20 405(c) 50.73(aH2)(rv) 73.71(b)  ;

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i LEVEL (10) 20 405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vn) OTHER i 20 405ta)(1)(iii) 50.73(a)(2)(i) 50.73(a)(2Mviii)(A) mcifv % Abstect f 20 405(a)(1)(iv) 50.73(a)(2)(n) 50.73(a)(2)(vinHB) 3 A j 20 405(aH1)(v) 50.73(a)(2)(in) 50.73(a)(2)(x}  !

LICENSEE CONTACT FOR THIS LER (12)

NAMs TELF PHONE NUMHEH Imeboe Area Godel  !

D.N. Lorfing, Supervisor ~ Nuclear Licensing (504) 381-4157 l l

COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCalBED IN THIS REPORT (13)

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cAUSE SvrEV COVDONENT MANUFACTUAER CAUSE SYSTEM COMPONENT MANUFACTURCA N D x BG 81 G080 Y t i

SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH N W ^H YES

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pt yea, co+ei ExnEcTED SUBMGSION DATE6

• DATE (15)

ABSTRACT (Limit to 1400 spaces, i c., approximately 15 single-spaced typewntten lines) (16) f At 0933 on June 29,1993, with the plant at 100 percent power (Operational Condition 1), the high pressure core spmy pump failed to stan and nm during a surveillance test due to a failed over-  !

frequency relay. This report is submitted pursuant to 10CFR50.73(a)(2)(v) as a condition that alone i could have prevented the fulfillment of a safety function.

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GSU perfonned extensive testing on the over frequency relay. The testing revealed that the relay would consistently trip at a lower frequency value than its design setpoint, indicating relay failure as ,

the root cause of the event. A new relay was obtained from the warehouse, tested satisfactorily, and ,

installed in the switchgear. The HPCS pump motor was sucessfully started and operability was '

verified. Due to redundancies inherent in the ECCS system design, failure of the HPCS pump to start is bounded by the safety analysis.

NRC F04M 366 8 971

REQUIRED NUMBER OF DIGITS / CHARACTERS  ;

FOR EACH BLOCK j BLOCK NUMBER OF E

NUMBER DIGITS / CHARACTERS 1 UP TO 46 FACluTY NAME

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6 ^ I p pE B OCK REPORT DATE UP TO 18 - FACILITY NAME f

8 8 TOTAL - DOCKET NUMBER OmER FACMIES NOWED 3 IN ADDITION TO 05000 9 1 OPERATING MODE 10 3 POWER LEVEL II REQUIREMENTS OF 10 CFR i CHECK BOX THAT APPLIES UP TO SO FOR NAME 12 LICENSEE CONTACT 14 FOR TELEPHONE CAUSE VARIES 2 FOR SYSTEM ,

13 4 FOR COMPONENT EACH COMPONENT FAILURE 4 FOR MANUFACTURER NPRDS VAR!ES ,

I4 SMEMER REN NECTED CHECK BOX THAT APPLIES 15 EXPECTED SUBMISSION DATE 2 PER BL CK I

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• i YRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 (5 s2)

EXPIRES 5/31/95 ESTlMATED BURDEN PER RESPONSE TO COMA Y W'TH TH:S LICENSEE EVENT REPORT (LER) E%E*REo #NoTRoEfSEobEE

' AND RECORDS MANAGEMENT BRANCH (MNBB 7714h U.S. NUCLEAR TEXT CONTINUATION REcutATony CoMM:sseN. WAssNoToN. DC 2mssem. ANo so THE PAPERWORi( REDUCTON PRNECT mtS0C10dh OFFICE OF M ANAGEVENT AND BdDGET, WASHfNGTON, DC 20$C3 FACILITY NAME (1) DOCRET NUMBER (2) LER NUMBER W PAGE (3) a SEQubNhA' Hb# ON YEAR NUMBER NL'MBER 05000 OF RIVER BEND STATION 458 93 - 013 -

00 2 3 tex,e mw. G.= v. w . u .. m m a a wC m on REPORTED CONDITION At 0933 on June 29,1993, with the plant at 100 percent power (Operational Condition 1), the high ,

pressure core spray (*BG*) pump (*P*) failed to start and run during a surveillance test due to a failed over-frequency relay (*81*). This report is submitted pursuant to 10CFR50.73(a)(2)(v) as a condition that alone could have prevented the fulfillment of a safety function.

INVESTIGATION The over frequency relay (*81*) was removed from the switchgear (*SWGR*) and taken to the relay l shop for testing. The initial bench test of the relay revealed a minimum pickup value 60.59 Hertz. The >

design setpoint of the relay (Drawing BE-230D) is 63 Hertz. Since the bus frequency was 60 Hertz, additional testing was performed. By simulating installed conditions (relay installed in an enclosed case  :

and the capacitor in an enclosed case), the relay would consistently trip at 60 Hertz, which was below the 63 Hertz design value. This demonstrated that the relay had failed.

Operations personnel observed that indicated amps increased to approximately 300 amps, followed by receipt of the tripped indication. This observation is feasible due to inrush current during the motor start and is not a concern.

On 7/9/93, using the guidance provided in NUREG-1022, " Licensee Event Report System," it was determined that this failure of the HPCS pump to operate was reportable under 10CFR50.72 as a 4-hour non-emergency event notification and the appropriate notification was made by the Shift Supervisor.

The Shift Supervisor on duty on June 29,1993, failed to recognize this event as reportable under 10CFR50.72. Upon reviewing 10CFR50.72(b)(2)(iii) at that time, he did not perceive this occurrence to be an " event or condition that alone could have prevented the fulfillment of the safety function of structures or systems that are needed to: (D) mitigate the consequences of an accident." He knew that this type of failure was bounded by the accident analysis, and thus did not believe it to be reportable under 10CFR50.72. During subsequent review of NUREG-1022 and the guidance provided therein, he realized his assumptions were incorrect.

ROOT CAUSE A change analysis evaluation was used in determining the root cause. Since the over frequency relay indicated that it had tripped (the target had dropped), System Engineering (SE) personnel focused their efforts on determining the reason for relay failure. When SE personnel arrived at the switchgear, the relay was not sealed in; therefore, there was some doubt as to the actual cause of the trip. Two .

conditions created this uncertainty. First, the door of the switchgear was open which would cause the environmental temperature for the capacitor (* CAP *) to change (cooler temperature) which would cause NRC FDAM 366A f5 923 -

l NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 s eri . EXPIRES 5/31/95 ESTIMAND BJRDEN PER RESPONSE TO COMPLY W:TH TH'S LICENSEE EVENT REPORT (LER) EO U N 'REGA$'~'l E DEN E 'u E 0 0 5 E 12 AND RECORDS MANAGEMENT BRANCH (MNBB 7714. U.S. NUCLEAR TEXT CONTINUATION REGULATORY COMM.SSiON, WASHfNGTON, DC 205554001, AND TO THE PAPERWORK REDUCTION PRCUECT (31504tNh OFFICE OF MANAGEMENT AND BUDGET, WASHNGTON. DC 70503.

FACIUTV NAME (t) DOCK ET NUMBER (2) LER NUMBER (s) PAGE p)

SEQUENhAL REviWON NUMBER NUMBER RIVER BEND STATION 458 93 _ 013 00 3 3 uxT m, . .e. c.w.o.. ..on. co, . .mc rom o n the setpoint of the relay to change. Second, the circuit breaker was removed from its cubicle which could change the relay logic status. Therefore, extensive testing was performed. By simulating installed conditions (relay installed in an enclosed case and the capacitor in an enclosed case), the relay would consistently trip at 60 Hertz. Therefore, the root cause of this event was the failure of the over frequency relay.

A search of plant records has indicated no previous problems or concerns with this relay. This is the only relay of this type on site. Also, a search of the NPRDS database revealed no reported failures for this type of relay.

GSU is conducting a review of previous condition reports in an effort to identify previous failures of single-train safety systems that were not reported to the NRC. The results of this review will be provided in a supplement to this report by October 1,1993. In addition, training on NUREG-1022 will be provided during Operations requali6 cation training. This training will be completed by October 5, 1993.

CORECTIVE ACTION ,

A new relay was obtained from the warehouse, tested satisfactorily, and installed in the switchgear. The HPCS pump motor was sucessfully started and operability was veri 0ed.

In addition, the test procedure for the over frequency relay, " Testing and Calibration of G.E. Relays UF-51 A" (MCP-1032), is being revised to provide better simulation of field conditions. This is to  ;

simulate actual operating conditions of the capacitor. If degradation of the capacitor is detected, then the i relay can be replaced prior to a complete failure.

SAFETY ASSESSMENT The primary purpose of HPCS is to maintain reactor vessel coolant inventory after small breaks which do not depressurize the reactor vessel. HPCS also provides spray cooling heat transfer following larger breaks.

The failure of the HPCS system has been analyzed and is bounded by the safety analysis. ,

Had a loss of coolant accident occurred, the HPCS pump would not have started; however, the River Bend Station design requires that in the event of HPCS system failure,3 low pressure coolant injection (LPCI) (*BO*) loops, the low pressure core spray (LPCS) (*BM*) & automatic depressurization systems (ADS) all be available to mitigate the cc.isequences of an accident. These systems, plus the reactor core isolation cooling system (RCIC) (*BN*) were operable at the time of the event.

NRC FOnM 36sA (5-92) ,

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