ML17328B014

LER 91-004-00:on 910313,reactor Tripped as Result of Turbine Trip Generated by Moisture separator-reheater High Water Level Trip.Caused by Ice & Snow Damaging Transmission Lines. Insp Performed on Governor & Steam traps.W/910412 Ltr

ML17328B014
Person / Time
Site:	Cook
Issue date:	04/12/1991
From:	Blind A, Carteaux P INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-004, LER-91-4, NUDOCS 9104180309
Download: ML17328B014 (6)

Text

ACCELERATED STRIBUTION DEMONSTRATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9104180309 DOC.DATE: 91/04/12 ,NOTARIZED: NO DOCKET ¹ FACIL:50-316 Donald C. Cook Nuclear Power Plant, Unit 2, Indiana & 05000316

. AUTHOR AFFILIATION AUTH. NAME CARTEAUX,P.F. Indiana Michigan Power Co. (formerly Indiana & Michigan Ele BLIND,A.A. Indiana Michigan Power Co. (formerly Indiana & Michigan Ele RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 91-004-00:on 910313,reactor tripped as result of turbine trip generated by level trip. Caused moisture separator-reheater high water by ice & snow damaging transmission lines.

Insp performed on governor & steam traps.W/910412 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), ncident Rpt, etc.

NOTES COPIES RECIPIENT ID CODE/NAME COPIES LTTR ENCL 'DRECIPIENT CODE/NAME LTTR ENCL PD3-1 LA 1 1 PD3-1 PD 1 1 COLBURN,T. 1 1 INTERNAL: ACNW 2 2 AEOD/DOA 1 1 AEOD/DS P/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB11 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPBll 2 2 NRR/DST/SELB SD 1 1 NRR/DST/SICB 7E 1 1 PLBSD1 1 1 NRR/DST/SRXB SE 1 1 RE I E ILE 01 02 1 1

1 1

RES/DSIR/EIB 1 1 EXTERNAL EG&G BRYCE i J H~ 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MAYS,G 1 1 NSIC MURPHYiG A 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL "RIDS" RECIPIENTS PLEASE HELP US TO REDUCE iVASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOP,I PI-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED'TTR 31 ENCL 31

Indiana Michigan~

Power Company~

Cook Nuclear Plarn One Cook Place Bridgrnan. Ml 49406 616 465 5901 lMDIANA NICHlGAN POWER April 12, 1991 United States Nuclear Regulatory Commission Document Control Desk Rockville, Maryland 20852 Operating Licenses DPR-74 Docket No. 50-316 Document Control Manager:

In accordance with the criteria established by 10 CFR 50.73 entitled Licensee Event Re ortin S stem the following report is being submitted:

91-004-00 Sincerely, vj. oe A.A. Blind Plant Manager AAB:sb Attachment c: D.H. Williams, Jr.

A.B. Davis, Region III E.E. Fitzpatrick P.A. Barrett B.F. Henderson R.F. Kroeger B. Walters Ft.'ayne NRC Resident Inspector T. Colburn NRC J.G. Keppler M.R. Padgett G. Charnoff, Esq.

Dottie Sherman, ANI Library D. Hahn INPO S.J. Brewer/B.P. Lauzau B.A. Svensson e10q13030g 910412 ADOCK 05000316 PDR PDR gpP

NRC FORM 366 (669) t LICENSEE EVENT REPORT ILER)

APPROVED OMB NO. 3)504))04 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH IP630), V.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31504104), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, OC 20503.

DOCKET NUMBER (2) IIA E 3 Nuclear Plant - Unit FACILITY NAME (1)

D. C. Cook 2 p p p p p 3 1 6 ~ pF0 4 Jfeactor Protection System Actuation Due to Lines Ice and Snow in Off-Site Electrical Transmission

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Dama .

EVENT DATE IS) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (4I c)P?I SSOVENTIAL r'ccc RE vtc lore MONTH DAY YEAR FACILITYNAMES DOCKET NUMBER(SI MONTH DAY YEAR YEAR ?g4 NVMSER ~a.; NVMSSR p 5 p p p 0 3 1 3 9'1 9 1 0 0 4 0 0 0 4 1 2 9 1 p 5 p p p THIS REPORT IS SUBMITTED PURSUANT 7 0 THE RLOUIREMENTS OF 10 CFR (It IChech one ot more of the fotlowfnf) (11 OPERATING MODE (9) ] 20.402(S) 20.406(cl 50,73( ~ ) (2) (iv) 73.71(S) 20.405 ( ~ ) (1) Bl 50.34(c) (1) 50.7$ ( ~ )(2)N) 73.71(c)

POWER LEYEL OTHER ISpeclfy In Abttrect PO) 1 0 0 20.405(e) (1)(ii) 50.$ 6(cl(2) 50.73(e) (2) (vS) below enrf ln Text, HRC Form

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LICENSFE CONTACT FOR THIS LER (121 NAME TELEPHONE NUMBER P. F. Carteaux Safety and Assessment AREA CODE Superintendent 6 1 6 4 6 5 5 9 0 1 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFAC.

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SUPPLEMENTAL REPORT EXPECTED(14) MONTH DAY YEAR EXPECTED SUBMISSION DATE (15I YES Ilfyet, complete EXPECTED SVBhtISSIOII DATEI NO ABSTRACT ILlmlt to f400 epecet, I.e., epptoxlmetely frfteen tingle tpece typewritten linn) (16)

On March 13, 1991 at 0651 hours0.00753 days <br />0.181 hours <br />0.00108 weeks <br />2.477055e-4 months <br />, the Unit 2 reactor tripped as a result of a turbine trip generated by a moisture separator-reheater (MSR) high water level trip. The turbine-generator trip and reactor trip were a result of off-site electrical transmission system disturbances. Ice and snow damaged 765 KV transmission lines which caused a significant load rejection on the main turbine. The closing of the main turbine control valves in response to the load rejection created a MSR pressure transient which actuated the MSR high water level trip and tripped the main turbine and reactor. The plant was stabilized in Mode 3.

Abnormalities noted during the event included the electronic overspeed trip of the turbine driven auxiliary feedwater pump, closure of one of the four main steam isolation valves, and apparent slow closure of the ¹4 combined intercept valve. All equipment malfunctions were reviewed with no unreviewed safety questions and the reactor was returned critical on March 15, 1991 at 1113 hours.

NRC Form 366 (689)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED 0MB NO. 31500104 (64)9)

EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REQUEST! 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION ANO REPORTS MANAGEMENT BRANCH (P4)30), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31504)104), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, 00 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

D. C. Cook Nuclear Plant SEQUENTIAL W'o RFYISION NUM88R 'OSS NUM88R Unit 2 o s o o o 3 1 6 9 1 0 0 4 0 0 0 2 QF0 4 TEXT /I/ more epece /4 rer/or)ed, ore eddio'one/P/RC Forrrr 3664'4/ (12)

Conditions Prior to Occurrence Unit 2 in Mode 1 at 100 percent, of Rated Thermal Power (RTP).

Descri tion of Event On March 13, 1991 at 0651 hours0.00753 days <br />0.181 hours <br />0.00108 weeks <br />2.477055e-4 months <br />, the Unit 2 reactor (EIIS/JE) tripped as a result of a turbine (EIIS/TA) trip generated by a moisture separator-reheater (MSR) (EIIS/SB-MSR) high water level trip. The turbine-generator trip and reactor trip were a result of off-site electrical transmission system disturbances. Ice and snow damaged 765 KV transmission (EIIS/FK) lines which caused a significant load rejection on the main turbine (greater than 504 steam flow with no load). The closing of the main turbine control valves (EIIS/TA-FCV) in response to the load rejection created a Moisture Separator-Reheater (MSR) pressure transient which actuated the MSR high water level trip and tripped the main turbine and reactor. The time from the most severe electrical transient to the MSR high level trip was 11.5 seconds.

The main turbine control .system (EIIS/TA-HCU) includes a speed governor driven by gears in the front standard and receives inputs from the load-limiter, operating device, acceleration limiter, steam pressure limiter, and control, valve position feedback; The acceleration limiter (EIIS/TA-SCO) prevents the turbine from tripping on overspeed on a load rejection by reacting more quickly than the governor and thereby limiting the maximum speed reached by the turbine.

acceleration reaches 47 RPM per second, corresponding to a 50%

If the turbine load rejection, the, acceleration limiter will close the high pressure control valves and low pressure intercept valves.

I It is believed that the 765 KV line disturbances, prior to the turbine trip, caused a significant load rejection and actuated the acceleration limiter. The unequal closing times of the control valves and intercept valves created a MSR pressure transient which lifted the MSR safety valves and actuated a 5-second time delayed MSR high level trip.

Following the turbine trip/reactor trip sequence, [tuibine (EIIS/TA-TRB) trip, opening or the reactor trip breakers (EIIS/JE-BKR), insertion of reactor control rods (EIIS/AA-ROD),

feedwater isolation (EIIS/JB), and automatic starting of the motor driven auxiliary feedwater pumps (EIIS/BA-P)], Operations personnel immediately implemented Emergency Operating Procedure 2 OHP 4023.E-O'to verify proper response of the automatic protection system and to asses plant conditions for indicated appropriated recovery actions.

NRC Form 366A 1669)

NRC FORM SeeA (689) t LICENSEE EVENT REPORT (LER)

'EXT CONTINUATION U.S NUCLEAR REGULATORY COMMISSION INFOAMATION AND REPOATS APPROVED OMB NO. 31500104 EXPIRES: 4/30/92 ESTIMATED BUADEN PER RESPONSE TO COMPLY WTH THIS COLLECTION REOUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO, THE RECORDS MANAGEMENT BRANCH (P.530), U.S, NUCLEAR REGULATORY COMMISSION, WASHINGTON, OC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31500104). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1I DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

D. C. Cook Nuclear Plant YEAR SPS SEOUSNTIAL IIEVISION

@~/ NUM888 NUM88A 'NA:

Unit 2 o s o o o 3 l 6 9 1 0 0 4 0 0 0 30F 0 4 TEXT /Ifmom 4Pooo /4/oqowod, 844 oddrdono/HRC FomI 36543) (IT)

Following the main generator trip and transfer to reserve feed (EIIS/FK), the 345 KV bus provided a stable power supplyUnit for the Unit 2 auxiliary loads. A review of fault records for 1 showed system upsets to a lesser degree, as it was not directly linked to the 765 KV bus.

Abnormalities noted during the event included the electronic overspeed trip of the turbine driven auxiliary feedwater pump (EIIS/BA-P), closure of one of the four main steam isolation valves (EIIS/SB-ISV), and slow closure of the N4 combined intercept valve (EIIS/SB-ISV). The turbine driven auxiliary The feedwater pump was immediately reset and placed in standby.

main steam isolation valve was bel'ieved to have drifted shut and was reopened within minutes of the trip. The N4 combined intercept slow closure has been attributed to an indication problem and not valve inoperability.

Cause of Event The cause of the event was ice and snow damaging 765 KV off-site electrical transmission lines resulting in an electrical disturbance beyond the control capability of the unit.

Anal sis of Event This report is being submitted in accordance with 10 CFR 50.73, paragraph (a)(2)(iv), as a event that resulted in an unplanned automatic actuation of the Engineered Safety Features, including the Reactor Protection System.

The automatic'rotection responses, including reactor trip and its associated actuations were verified tosignal. have functioned properly as a result of the reactor trip The electronic

.overspeed trip of the Turbine Driven Auxiliary feedwater pump was immediately reset from the control the pump would have been available room if and required.

it is believed The Main that Steam Isolation Valve, which drifted shut, was reopened within minutes of the trip. The slow closure of the combined intercept valve was attributed to a limit switch which did not reflect actual valve position. Based on the above, it is concluded that the event did not constitute an unreviewed safety question as defined in 10 CFR 50.59 (a) (2) nor did it adversely impact the health and safety of the public.

NRC Form 366A (669)

NRC FORM 366A APPROVED 0MB NO. 31500104 (689)

EXPIRES: 4/30/92  !

ESTIL(ATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REOUESTI 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (PJ)30), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31500104), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (21 LER NUMBER (6) PAGE (3)

D. C. Cook Nuclear Plant YEAR i?(g SEOVENTIAI.

NUMBER

?.'o? REVISION

'Fc?I NUMBER Unit 2 o s o o o 31691 0 0 4 0 0 0 4 OF 0 4 TEXT /lfmom SOooo /4 mqoksd, ooo oddi)looo/ HRC Fono 36649/ (17)

Corrective ctions Turbine Driven Auxiliary Feedwater Pump (TDAFP)

The cause of the TDAFP electronic overspeed trip could not be conclusively determined. A through review of the event and extensive testing did not reveal the reason for the overspeed event. Post trip testing included:

o measurement'f the as found electrical trip o inspection of the governor valve linkage and stem for binding or corrosion o inspection of the governor oil for water contamination o inspection of steam traps on the steam supply piping o a functional test of the TDAFP electronic overspeed.

All tests and inspections were normal.

Main Steam Isolation Valve (MSIV) Closing A review of past Unit 1 and Unit 2 trips showed several cases where MSIVs drifted off their open seats, as was the case on this particular trip with MSIVs 421 and 422. This was the first trip identified where a MSIV closed completely, but given the secondary transient experienced, that this would occur.

it is not considered unusual Combined Intercept Valve 44 The Combined Intercept Valve 44 appeared to slow close over a 5 minute period as indicated by an intermediate valve position and the fact that the Turbine Events Recorder did not register the valve as being closed. As a condition to restart, the valve was timed in the closed direction and yielded a value of 1.2 is believed that a single limit switch did not initially seconds.'t close. This limit switch would keep the open light prevent the Turbine Events Recorder form indicating a closed lit and position.

Failed Com onent Identification None Previous Similar Events None NRC F oim 366A (BS9)