05000445/LER-2003-003, For Comanche Peak Unit 1 Reactor Trip on Units 1 & 2 Due to Grid Disturbance

For Comanche Peak Unit 1 Reactor Trip on Units 1 & 2 Due to Grid Disturbance

ML032040042
Person / Time
Site:	Comanche Peak
Issue date:	07/14/2003
From:	Walker R TXU Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
10010, CPSES-200301393, TXX-03115 LER 03-003-00
Download: ML032040042 (9)

LER-2003-003, For Comanche Peak Unit 1 Reactor Trip on Units 1 & 2 Due to Grid Disturbance

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
4452003003R00 - NRC Website

text

7 fhTXU TXU Energy Comanche Peak Steam Electric Station RO. Box 1002 (EO1)

Glen Rose,TX 76043 Tel: 254 897 8920 Fax 254 897 6652 lance.terry@txu.com C. Lance Terry Senior Vice President &

Principal Nuclear Officer Ref: 10CFR50.73(a)(2)(iv)(A)

CPSES-200301393 Log# TXX-03115 File # 10010 July 14, 2003 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)

DOCKET NOS. 50-445 AND 50-446 REACTOR TRIP ON UNITS 1 AND 2 DUE TO GRID DISTURBANCE LICENSEE EVENT REPORT 445/03-003-00 Gentlemen:

Enclosed is Licensee Event Report (LER) 03-003-00 for Comanche Peak Steam Electric Station Units 1 and 2, "Reactor Trip on Units 1 and 2 due to Grid Disturbance."

This communication contains no new commitments regarding CPSES Units 1 and 2.

3

L -1,F:5 0

Q TXU TXX-03 115 Page 2 of 2 Sincerely, TXU Generation Company LP By:

TXU Generation Management Company LLC, Its General Partner C. L. Terry Senior Vice President and Principal Nuclear Officer By:

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.e iRo~

D. Walker Regulatory Affairs Manager JDS/js Enclosure c -

T. P. Gwynn, Region IV W. D. Johnson, Region IV D. H. Jaffe, NRR Resident Inspectors, CPSES

Enclosure to TXX-03115 FNRC FORM 366 U.. NUCLZAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150104 (7-2001)

EXPIRES 6713112004 Eatimated buden per response to comply wish this mandatory hiflirnusin. collestin requent: 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />. Repsued lessons learned A incorporazed ao the licensing pacess and fed back to kidusoy. Send comients regarding burden estimate o the Reods LICENSEE EVENT REPORT (LER) or.40 by nr ail ngov and so the Desk Officer, Offic of Infoiaion and Replatry Axfs NEOB-10202 (315040104) Of ficee of Mgm and Budget. Washington. DC 20503If a faa used 6o Impose Inforbntin collection does a display a currently valid OMB comesl iunber. the NRC May nt conduct Or Donsor. and a n is not ued torespo to, the infirnnainn collectine.

Facility Name (1)

Docket Number (2)

Page (3)

COMANCHE PEAK STEAM ELECTRIC STATION UNrr 1 05000445 1 OF 7 Tle (4)

REACTOR TRIP ON UNITS 1 AND 2 DUE TO GRID DISTURBANCE Event Dote (

lE Number 6)

Repost Date (7)

Olher Facilits Involved ()

Month Dy Yer Year Sequential Revision onh DAY Y

FlityNam DokiiNumbers JNumber

• INumber l

CPSES UNIT 2 05000446 05 1 15 03 03 00 07 14 03 05000 Mode (9)

£ 20.2201(b) 20.2203(aX3Xi)

I S0.73(aX2)(iXC) 50.73(aX2Xvii)

Power 202201(d) 20.2203(aX3ii) l 50.73(aX2)iiXA) 50.73(aX2XviiiXA)

LUve 100 20.2203(aX)(

l 20.2203(aX4) l 50.73(aX2)(fiXB) 50.73(aX2Xviii)(B) 20.2203(aX2Xi) 50.36(cX2XiXA) 50.73(aX2Xiii) 50.73(aX2)(ix)(A) 20.2203(aX2Xii) 50.36(CXIXiiXA)

X S.73(aX2)(iv)WA) 50.72(aX2)(x) 20.2203(a)(2iii) 50.36(cX2) 50.73(aW2XvXA) 73.71(a)l4) 20.2203(a)(2Xiv) 50.46(aX3Xii)

S0.73(aX2XvWB) 73.71(aX5) 20.2203(aX2Xv) 50.73(aX2XiXA) 50.73(aX2Xv XC)

OTHER 20.2203(aX2Xvi) 50.73(aX2XiXB) 50.73(aW2X)(vD)

Specify in Abstract below or in =

SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES On May 15, 2003 at 0252 a B-phase to ground fault occurred on the Parker line approximately four miles from the CPSES 345kV switchyard. The failure of the switchyard breaker protection to adequately recognize and clear the fault resulted in a total loss of the 345kV switchyard. The fault detector relays (EIIS: (FK)(5 1)) in both the primary and backup protection schemes of the CPSES Parker line circuit breaker did not function properly. Due to the failure of the primary and backup protection schemes for the CPSES to Parker transmission line breaker, the fault resulted in a total loss of the CPSES 345kV switchyard approximately 20 seconds after the fault began.

NRC PORM 366A (1-20DI)

Enclosure to TXX-03115 NRC FORMM 3GM U

NUCLEAR REGULATORY COMMSION LICENSEE EVENT REPORT (LER)

Faciliy Name (I)

Docket LER Number (6)

PAgc(3)

Year S

mimi i

l Rei COMANCHE PEAK STEAM ELECTRIC STATION UNIT 1 05000445 m

Number 0500445 03H003 H 00 1 3OF 7 NARRATIVE (If mre space requred. use addital copies of NRC Po 366A) (17)

The Reactor Coolant Pumps (EIIS:(AB)(P)) sensed low voltage due to the loss of non-safety related ac power and Units 1 and 2 reactors tripped at approximately 1.5 seconds after failure of the switchyard breaker protection.

Both unit generator breakers (EIIS:(TB)(BKR)) tripped due to generator distance relaying actuating generator lockout relays (EIIS:(TB)(86)) and subsequent load rejection protection circuits tripped both turbines.

All plant actuations occurred as designed. The Reactor Coolant Pumps tripped as expected due to the loss of non-safety bus voltage and the Reactor Coolant Pumps coasted down. The Auxiliary Feedwater Pumps actuated and provided auxiliary feedwater to the steam generators (SG) as designed. The Reactor Operators controlled AFW (Auxiliary Feedwater) flow and maintained the SG water levels. Main Feedwater isolation occurred immediately following the reactor trip as expected.

Natural circulation flows were established within one minute and adequate subcooling maintained. The reactors were maintained in Mode 3 under natural circulation until the Reactor Coolant Pumps were started at 0533 for Unit 1 and 0625 for Unit 2.

The system response of the Unit 1 and Unit 2 trips and the operator actions were consistent with the plant design and the supporting analyses presented in CPSES Final Safety Analysis Report (FSAR).

E.

THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE, OR PROCEDURAL OR PERSONNEL ERROR Control board indicators and alarms alerted the reactor operator (utility, licensed) in each unit that the generator breakers were open, the reactor trip breakers were open, and the Reactor Coolant Pumps were tripped.

IL COMPONENT OR SYSTEM FAILURES A.

FAILURE MODE, MECHANISM, AND EFFECTS OF EACH FAILED COMPONENT The trip of Units 1 and 2 as a result of a disturbance on one of the 345kV transmission lines was not expected. TXU Energy believes that the primary and backup fault detection circuit relays did not function as designed.

L REE.D ULNA {1.-

- I

- n

Enclosure to TXX-031 15 (If me ie i required. use aidional copies of NRC Fom 366) (17)

B.

CAUSE OF EACH COMPONENT OR SYSTEM FAILURE Management oversight of switchyard activities, maintenance practices, and protective circuit design contributed to a high resistance build-up on the contacts of the fault detection circuit relays which prevented successful isolation of the grid disturbance.

C.

SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED BY FAILURE OF COMPONENTS WITH MULTIPLE FUNCTIONS Not applicable -- no failure of components with multiple functions have been identified.

D.

FAILED COMPONENT INFORMATION

Manufacturer:

General Electric NSS/A-Model Number:

Model 12CHC21A2A Fault detector relays m.

ANALYSIS OF THE EVENT

A.

SAFETY SYSTEM RESPONSES THAT OCCURRED

1. The reactor trip breakers opened.

2.

The main turbine tripped (turbine stop valves closed).

3.

The control rod drive mechanism allowed all the control rods to fully drop into the core.

4.

All auxiliary feedwater (AFW) pumps started automatically and delivered water to all steam generators as required.

5.

The Atmospheric Relief Valves (ARVs) actuated to control steam line pressure, and thus RCS temperature as designed.

6.

The Unit 1 Safety Related 6.9kV busses preferred power supply was slow transferred to its alternate power supply as designed.

NRC FURM 366A (1-2001)

Endosure to TXX-031 15 If more spae is requied. me uilitional copies of (If mespcei mqureds edito pes of NRC em366A) (17)

VL

PREVIOUS SIMILAR EVENTS

Although there have been previous events that resulted in RPS actuation due to a grid disturbance (refer to LER 445/91-013-00, LER 445/91-019-00, LER 445/91-021-00, and LER 445/91-022-00), the evaluation performed during the aforementioned LERs did not consider the impact on the fault detector relays.

Therefore, corrective actions taken to resolve the root causes of the previous events would not have prevented this event.