05000263/LER-1993-008

LER 93-008-00:on 930731,RPS Tripped from Reactor Low Water Level.Caused by Main Condensate Pump Trip.Condensate Pump 11 Motor Will Be Inspected & Preventive Maint Will Be Performed on Condensate Pump 11 breaker.W/930830 Ltr

ML20056G906
Person / Time
Site:	Monticello
Issue date:	08/30/1993
From:	Richard Anderson, Engelke S NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-008-01, LER-93-8-1, NUDOCS 9309070295
Download: ML20056G906 (6)

LER-2093-008,

Event date:
Report date:
2632093008R00 - NRC Website

text

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j Narthem States Power Company i 414 Nicollet Mall Minneapolis, Minnesota 55401 1927 Telephone (612) 330-5500 j August 30, 1993 Report Required by ,

10 CFR Part 50, Section 50.73 US Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 MONTICELLO NUCLEAR GENERATING PIANT Docket No. 50-263 License No. DPR-22 Reactor Protection System Actuation From Low f Reactor Level Caused by Main Condensate Pump Trin  !

I The Licensee Event Report for this occurrence is attached. This report l contains the following new NRC commitments. '

1. The No. 11 Condensate Pump motor will be inspected for any internal degradation during the 1994 refueling outage.

2. Preventive maintenance will be performed on the No. 11 Condensate  !

Pump breaker during the 1994 refueling outage. l Please contact Marv Engen, Sr Licensing Engineer, at (612) 295-1291 if you [

require further information.  !

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( ,t[ h h M 7L-Ro.er 0 Anderson i Director '

Licensing and Management Issues  ;

c: Regional Administrator - III, NP,C  !

NRR Project Manager, NRC Sr Resident Inspector, NRC State of Minnesota Attn: Kris Sanda f

Attachment l

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PDR ADOCK 05000263 OJ l i S PDR W )  ;

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f NRC FOPM 366 U S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 ,

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(See reverse for required nurnber of dig >ts/ Characters for each block) MANAGEVENT AND BJDGET. W ASHINTON, DC 20503 r i

f ACILITV NAME (1) DOCALT NUMBER (2) PAGE (3) ,

MONTICELLO NUCLEAR GENERATING PLANT 05000-263 1 OF 4  ;

t "5 8*' Reactor Protection System Actuation From Low i Reactor Level Caused by Main Condensate Pump Trin [

EVENT DATE (5) LER NUMBER (6' REPORT NUMBER (7) OTHER F ACILITIES INVOLVED (8) i St OJL N1A1 REVCON I Mus an ma vE An y.,yg, y, ex" Du vE**

05000 j f AOiUTY NMR DOCKET NUMBER  !

07 31 93 93 - 008 00 08 30 93 05000 l

f0PERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR O (Check one or more) (11) f N

MODE (9) 20 402fb) 20 405tc) m 50 73(aH2)(w) 73 71(b) ,

POWER 20 405MH1)D) 50.36(cH1) 50.73(a)(2Hvl 73.71(c)

LEVEL (10) 100 20 4cs:aln Hn) 50.asrc)(2) 50 73(aH2)(vn) OTHER I 20 4051a H1 Hm) 50 73ta)(2)(0 50.73(aH2Hvud(A) >+g m Abut ,

betow and m Test NRC f 20 4DStaH110v) 50.73(aH2)OO 50.73(a)(2Hvm](B) So,m 3m j 20 405;aH11tv) 50.73(aH2HW) 50.73taH2)(a1 (

LICENSEE CONTACT F OR THIS LER {12) I f NAMt. TELiPHONE NUMBE.h thusoe Area Coce) I Steve Engelke, Superintendent, Elec & Inst Systems Eng (612) 295-1329 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)  ;

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cut.c frsu v avw N- eANw ACM AE D CAUSE SYrEM COMPONE NT MANur ACTURE R J  !

i X SD 50 G080 Yes i i,  !

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l SUPPLEMENT AL REPORT EXPECTED (14) EXPECTED "N" D" " EAR l

YE5 NO m y.s mem rwr C'rD sa noN rcri y DATE (15) l j ABSTRACT (Umit to 1430 spaces. i e., appronmatey 15 single-spaced typeuntien knes) (16)  ;

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l During normal full power operation a Reactor Protection System trip from low  ;

i reactor water level occurred. The Standby Gas Treatment System and several {

j containment isolation groups were also initiated on lew reactor level. Normal j

post trip procedures were followed to restore stable conditions. One  ;

j condensate and one feedwater pump remained in operation during the event. f Level remained well above the ECCS initiation setpoint. There were no  !

failures or other complications. The immediate cause was a reduction in  ;

. reactor feedwater flow due to a ground fault relay trip of a main condensate {

pump. The cause of the ground fault relay trip has not been determined. l Extensive investigation and testing was conducted. No abnormal conditions  ;

were found. A motor inspection and breaker maintenance are scheduled for the I next refueling outage.

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i REQUIRED NUMBER OF DIGITS / CHARACTERS  !

FOR EACH BLOCK j BLOCK NUMBER OF NUMBER DIGITS / CHARACTERS 1 UP TO 46 FACILITY NAME  ;

2 DOCKET NUMBER I

- m ADDITiOf4 o 05000 3 VARIES PAGE NUMBER I

4 UP TO 76 TITLE 5 DATE 2 PER BLOCK 7 TOTAL 6 LER NUMBER 3 FOR SEQUENTIAL NUMBER 2 FOR REVISION NUMBER 6 TOTAL -

7 REPORT DATE  !

2 PER BLOCK  !

UP TO 18 - FACILITY NAME

• I 8 OTHER FACILITIES INVOLVED 8 TOTAL- DOCKET NUMBER 3 IN ADDITION TO 05000 l t

r 9 1 OPERATING MODE l I

l 10 3 POWER LEVEL f 1

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'I REQUIREMENTS OF 10 CFR I CHECK BOX THAT APPLIES UP TO 50 FOR NAME

$- 12 LICENSEE CONTACT 14 FOR TELEPHONE CAUSE VARIES 2 FOR SYSTEM 13 4 FOR COMPONENT EACH COVPONENT F. ALLURE

] 4 FOR MANUFACTURER l

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1 i 14 SUPPLEMENT AL REPORT EXPECTED t CHECK BOX THAT APPLIES i c

6 TOTAL 15 EXPECTED SUBMISSION DATE 2 PER BLOCK i

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TEXT CONTINUATION PEGULATON COMM $3CN W ASNtNGTON, DC 20558Kr#1. AND TO i TME PAPERWORK MLDUCT)N PROJECT (315H10dj, OFFICE OF MANAGEMEN'T AND BJD3ET, WASM;NGTON. DC 20503 4

7 ACIUTY 84AME (1) DOCKE1 NUMBER (2) LER NUMBER (6) I P AGE (3)

SEQUENTA. HE vtSON ,

NVMBER WUVBER 05000 -263 op l Monticello Nuclear Generating Plant 93 - 008 -

00 2 4 f

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Description i i

On July 31, 1993, at 0234 hours0.00271 days <br />0.065 hours <br />3.869048e-4 weeks <br />8.9037e-5 months <br />, with the plant at 100% thernal power, the j Reactor Protection System (EIIS System: JC) tripped from reactor low water level. The low water level also initiated the Standby Gas Treatment System (EIIS System: BH). Secondary Containment (EIIS System: NG), Reactor Water l Cleanup (EIIS System: CE)(Group 3) and Primary Containment (Group 2) ,

isolations.

9 The event began when a ground fault relay tripped (EIIS Component: 50) the No. '

11 Condensate (EIIS System: SD) pump. This subsequently resulted in a low suction pressure trip of No. 11 Reactor Feedwater (EIIS System: SJ) pump. In response to the condensate pump trip, the control room operator initiated a j reduction of reactor recirculation flow to reduce reactor power and thereby reduce feedwater requirements to within the capability of the remaining pumps.  :

However, the feedwater pump tripped and reactor level reached the scram ,

I setpoint before a sufficient reduction was achieved. The operating crew I l performed normal post scram and isolation follow-up procedures to place the plant in a stable condition and restore isolated systems. l The event is reportable per 10CFR50.73 as an unplanned automatic actuation of Engineered Safety Features.  !

Cause The cause of the condensate pump ground fault trip is unknown. The breaker was inspected, the pump motor and leads were meggered, resistance of each '

phase was measured, the ground fault current transformer was inspected and tests were conducted to verify proper operation. The ground fault relay was tested for setpoint and sensitivity to mechanical shock. An induction motor l rotor c. .dition test was conducted. A sample of the motor oil was analyzed.

4KV bus .itages prior to and during the event, as recorded by the plant computer, were evaluated. Cable terminations and connections were inspected.

I Everything indicated that the pump, motor and associated electrical equipment were operating properly. Subsequent operation of the pump appears normal.

There was one person near the back side of the breaker at the time of the trip. A review of the movements of this individual indicated that the breaker cabinet containing the ground fault relay was not bumped.

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EXPIRES 5/31/95  ;

ESTIMMED BJRDEN PER RESPONSE To COMPLY W'TH THIS INFoRMATON COLLECTON HEQUEST: S:: 0 HHS. FORWARD LICEf1SEE EVEtJT REPORT (LER) covuons RE2 ara,NG BUR 3tN Ec.ucs Tas NucaAR x.), u,NroRMcCN TEXT CONTINUATION """ "E

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REGJLATORY """" E"",# 8New mBB m ESCN WASHrNGTON. DC 205S5-0001, AND TO THE F APERWORK REDUCTON PROJECT (3160 0104;. OFFICE oF i MANAGEMENT AND BJDGET. WuHtNGToN. DC 20S33 l 1

f ACIUTY NAME (1) DOCKET NUMBER (2) LER HUMBER (6) FAGE (3) l EEQJENTAL RE w4CN l l

NUMBER NUMBER i 05000-263 OF l Monticello Nuclear Generating Plant 93 008 00 3 4 l TEXT w n,w ,w. a nw.a .aonsm . n8c w m on l Analysis This event represents an unnecessary challenge to the reactor protection and isolation systems and an unnecessary plant transient. It occurred at full l rated power which is the most severe condition for a loss of feedwater. l l Iloweve r , all systems responded as designed and all parameters remained within l l analyzed values. The No. 12 Condensate and No. 12 Feedwater pumps remained in l set ice during the event. Reactor level remained well above the ECCS in;;iation lesel. Therefore, there were no consequences directly affecting ,

! pu ile health and safety. j i

Corrective Actions The following activities were performed to determine immediate corrective $

actions. However, no abnormal conditions were found. j i

l 1. Megger of the motor and leads from the breaker cubicle. l l

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2. Rcsistance checks of each phase of the motor from the breaker cubicle. l

3. Breaker tests including mc s , contact resistance, and close/ trip operation.

l 4 Set point verification of the ground fault relay. l l

S. Visual inspection of the ground fault cucrent transformer, bresker terminations, and current transformer cabling at the breaker cubicle.

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6. Current transformer test with data compared to previous data.

7. An induction motor rotor condition test.

8. Motor oil sample analysis.

9. Evaluation of 4KV. bus voltage levels prior to and during the event, as recorded by the plant computer.

l l 10. Inspection of cable connection condition at the *3rmination box.

11. With the ground fault relay isolated, it was jarred . etermine sensitivity to mechanical shock.

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 5 83 i

. EXPlRES S/31/95 ESTIMA*ED BURDEN PE A RESPONSE To c0MPLY Wr!H THIS INFORMATON cOMI N N REQUEST; 50.0 HRS. FORWARD i LICENSEE EVENT REPORT (LER) COMME,c5 REaAeN2 oun0EN ESTum To TsE ~FoRucow TEXT CONTINUATION AND RECOFOS MANAGEMENT BRANCH (MNBB 7714), U.S NUCLEAR i REcuuToa< covu:ESow. wASesTm. oc ms.omi. ANo To  :

1 TME PAPERWORK REDUCTON PRNECT 13150C104), OFFICE or +

u ANAGEMENT AND BJDGET, WASH!NGTON. DC 20503 I F ACluTY NAME (1) DOCKET NUMBEH (2) LE R HUMBE R (5) PAGE(3) bEQJENT4AL Ftyrs.ON g

NUMBER NUMBER 05000 - 263 OF

93. ~ 008 Monticello Nuclear Generating Plant 00 4 4 i Ttma mw ,P.e <, ,aw.m a. . mon ees e wc ram ym o r;  ;

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12. The individual near the breaker when it tripped was interviewed. ,

13. Vibration testing and thermographic inspection cf the motor and breaker cubicle after restarting the motor.

The following actions are scheduled for completion during the 1994 refueling ,

outage:

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1. The motor will be inspected for any internal degradation.

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2. Preventive maintenance will be performed on the breaker '

i Additional Information Failed Nmponent Identification:

l A Ground Fault Rely i Manufacturer: General Electric -

Model: 12PJC11AVIA a "*evious Simulator Events:

1 Ne previous event, Licensee Event 87-009, Scram Following Closure of  ;

i sV Preaker Door, involved a trip of the condensate pump breaker. '

Ilowever, unlike the recent event, that event cas caused by a forceful l closure of the breaker door which initiated the condensate pump trip relays.

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