ML19325C285

LER 89-004-00:on 890907,reactor Trip Occurred as Result of Lightning Induced Voltage Transient Affecting Rod Control Sys.Caused by Lightning Striking Containment.Rod Control Sys Devices reset.W/891006 Ltr

ML19325C285
Person / Time
Site:	Braidwood
Issue date:	10/03/1989
From:	Lawson D, Querio R COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BW-89-1173, LER-89-004-09, LER-89-4-9, NUDOCS 8910160019
Download: ML19325C285 (4)

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October 6,1989- 1

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BW/89-1173. ,

h U .S. Nuclear Regulatory. Commission

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Document Control Desk

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Dear Sir:

l The enclosed Licensee Event Report from Braldwood Generating  ;

Station is being transmitted to you in accordance with the requirements of .;

10CFR50.73(a)(2)(iv) which requires a 30 day written report. l This report is number 89-004-00; Docket No. 50-457. u Very truly yours, .;.

cr/AM  !

.. . Querto Station Manager.

Braidwood Nuclear Station REQ /AJS/jfe

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Enclosure:

Licensee Event Report No. 89-004-00 o .

E ctL - cc: NRC Region III Administrator NRC Resident inspector INPO Record Center

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N 1 . 8910160019 891003 PDR ADOCK 05000457 S PDC

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y,.7 LICENSEE EVENT REPORT (LER) ~ ,

facility Name;(1)f Docket Number (2). . A ge (3)

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g Title (4)' Reactor Trip'As;a Result of Lightning Induced Voltage Transient

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y -- Af fecting Pod Control System .

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_ Lyt 3LDut 6) _ L LfLhst.E_(6) ReppdJdt (7) 01her racilities Involved (81

, Month. Day .Yeart Year / Sequential Revision Month Day Year Facility Names Jpdtt Number (s)

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._01 9- ~ 01 7 81 9. 31. 9.. __.l.Ql0l4 01 0 110 _Ql 3 81 9 01 5.L Q.l_QL91_LL .i THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS Of 10CrR OPNM. (Check one or more of the followino) (11) p, '

__ 20.402(b)' 20.405(c) )L 50.73(a)(2)(iv) _ 73.71(b)

POWER _ 20.405(a)(1)(1) _ 50.36(c)(1) ._ 50.73(a)(2)(v) .__ 73.71(c) -

20.405(a)(1)(11) 50.36(c)(2) 50.73(a)(2)(vil) Other (Specify g LEVEL 3 y _ _ _ _

in Abstract

'(10): 8 1 9I 9 __ 20.405(a)(1)(iii) _ 50.73(a)(2)(i) ___ 50.73(a)(2)(viii)(A)

////////////////////////// __._ 20.405(a)(1)(iv) ___ 50.73(a)(2)(li) __ 50.73(a)(2)(vill)(B) below and in

/////////////r//////////// _ _ 20.405(a)(1)(v) _ 50.73(a)(2)(lit) ._._ 50.73(a)(2)(x) Text)

LICENSEE CONTACT FOR THIS LER (12)

TELEPHONE NUMBER Name David R. Lawson, Technical Staff Engineer 2492 g g g- 9 g; ,; pg g COMPLETE ONE LINE FOR EACH COM NN FAILURE DESCRIBED IN THIS REPORT (131 l' COMPONENT MNUT AC- ' REPORTABLE CAUSE SYSTEH COMPONENT MANUFAC- REPORTABLE CAUSE SYSTEN TURER TO NPRDS TURER TO NPRDS s I I I I I lI No l l l l l l l )

I I I I I I I I I I I I l l SUPPLEMENTAL REPORT EXPECTED (14) Expected Month l Day.1.,ytn Submission

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lYrJ_(If ves. c2mP.lete EXPECTED SUBH H HQM_QATE) X l NO l ll ll '!

ABSTRACT (Limit to 1400 spaces. i.e, approximately fif teen single-space typewritten lines) (16)

A cf At approximately 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />, September 7, 1989 a severe thunderstorm was in the area of Braidwood Station. ,

. video recorder had been set up to monitor the effects of atmospheric events, f rom 2029 to 2036 sixty-three

. lightning. flashes were recorded by the camera. Four of these lightning strikes hit station structures. The Unit 2. Auxiliary Building Vent Stack was struck twice. The Braidwood Station Switchyard was struck. At 2031:44 the Unit 2 containment was struck. At 2032 all ten Rod Control System (RD) Po-er Cabinet overvoltage l

Protection. devices actuated. This caused the static- ery gripper coils of the control rods to deenergize and the rods dropped into the core. The rapid flux decrease was sensed by the nuclear instrumentation wMch generated a Power Range fluxrate High Reactor Trip. The Reactor Trip Breakers opened, the Turbine tripped, and Feedwater Isolation occurred. The shrink effect on Steam Generator Level instrumentation resulted in an auto start of the Auxiliary feedwater pumps on low water level. The cause of this event was a lightning '

ilnduced voltage transient. The RD overvoltage protection devices were retst. The RD system was tested. A 4 time delay has been added to the overvoltage protection devices. Recommendations on additional corrective

' measures are being evaluated. There have been two previous occurrences. Previous corrective actions were 4

not applicable.

28772(100689)/2

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• M i[H$tt EVENT REPORT (LER) TEXT CONTINUATION- Fore Re,y_L9_

DOCKET NUteER (2); i LER NUteER (6) __ _Pagt (3) y ' FACILITY NAME (1)1 3

Year- fj//f

/ Sequential /// ' Revision

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> Jhidwood 2 0 1 5 1 0 1 0.1 0 1 41 ] 7 e19 -

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TEXTc Energy Industry, Identification System (Ell $) codes are identified in the text as (XX)

I (A; ' PLANT CONDITIONS PRIOR,TO EVENT:

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- . Unit: -Braidwood 2; Event Date: September 7, 1989; Event ilme: 2033; o

, = Mode: s 1; Power Operation;- Rx Power: -1001;-

-RCS [AB]ITempera'ture/ Pressure: - NOT/NOP.

U Bi DESCRIPTION OF EVENT:

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, .There were no systems or components' inoperable at the beginning of the event which contributed to the. severity of.

the event.

At approximately'2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />,I$eptember 7,1989 a severe thunderstorm was in the area of Braidwood Nuclear -

Generating $tation, 'A. video camera connected to a video cassette recorder had been set up to monitor the effects af atmospheric events.on station.structuees. The camera and recorder.were in operation for this event. i b

From 2029 to 2036. sixty-three lightning flashes were recorded by the camera. Four of these lightning strikes have i

'b;en identified as striking station structures.

At 2030 the Unit 2- Aux 111ary Building Vent Stack was' hit.

At 2031:09 the Unit 2. Auxiliary Building Vent Stack was hit for a second time.

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At 2031!44 one of the Lightning rods on the Unit 2 containment was struck by Lightning.

IAt 2032, a Rod Control. Urgent alate occurred. This was due to the actuation of all ten Rod Control system (RD)

, [AA) Power Cabinet Positive Low Voltage Power Supply Overvoltage Protection devices. This caused a loss of

' control power to'the Rod Drive control cards. On the loss of control power the stationary gripper coils of the'  !

control rods ldeenergize causing the-rods to insert into the core as designed. The rapid Neutron Flux decrease was

. sensed by the. Power Range Nuclear Instrumentation (NI) (IG) which generated a Power Range Flumrate High Reactor l I

Trip. 'The: Reactor. Trip Breakers opened,-the lurbine tripped, and feedwater Isolation occured as designed.

-Numerous' spurious alarms were received but immediately cleared. These were attributed to the voltage transient.

The rapid reduction in the steam flow from the Turbine Trip caused a shrinir effect on Steam Generator level

' instrumentation. . This resulted in an auto start of the Auxiliary Feed =ater (BA) pumps on indicated Low low Steam .;

iC Generator Water Level as anticipated. ' Stable plant conditions were established. Operator actions neither j i increased.nor decreased the severity of this event.

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.'At ! 2245 t'e h appropriate notification via the ENS phone system was made pursuant to ICCFR50.72(b)(2)(ii).

.This event'Is being reported pursuant to 10CFR50.73(a)(2)(iv) - any event or condition that resulteo in manual or automatic actuation of any Engineered $afety Feature, including the Reactor Protection System.

7 12877r.(100689)/3

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[9 u;O' (k t EENSEE' EVENT REPORT (LER) TEXT CONTINUATION- ~ Fore Rev 2.0 h' FACILITY NAME. (1)!. '

. DOCKET .NVPBER (2) _LL!LNLL@LR f 6) _ f r e.f31 h i" [*'

., Year fj/

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fff Revision

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!h LTEXT; , Energy. Industry Identification-System (E!!$) codes'are identified in the tent as (XX).

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po C.i CAUht OF.EVENTiL '

i The root'cause'of_this event .nas'a voltage transient. It is believed that the lightning that struct the Unit g > 2 Containment caused a voltage surge in the station ground system. This caused a sudden voltage surge in the j

L. LRD power supplies which actuated the RD overvoltage protection and caused the Control Rod stationary gripper q Jcrils to deenergize.

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D,. $AFETY ANALYSIS:

g. This event had no effect on tne safety.of the plant or the.oublic. All systems operated as designed. Both

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l trains -of Reactor Protection' tad ESF were operablo and performed their. functions as designed.

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The worst case condition it a Unit operating at 1007. power with a Rod Control f ailure. The Rod Control 1 system is designed to be inherently safe as rod insertion results on loss of power as was the case in this

Ltwent'.

E.; CORRECTIVE ACTIONS:

The' Rod Control system Power Cabinet Positive Low Voltage Power Supply Overvoltage Protection devices were 4 reset. The RD system was tested by withdrawing each bank of rods 12 steps and then reinserting the bank, br Y ~ During the performance-of this test a fuse in one of the power cabinets was found to be blown. The fuse was y r:placed. All rods performed satisf actorily. ,

. A time delay' has been added to the overvoltage protection devices for the RD Power Cabinet Positive Low Voltage Power $upplies on Unit 1 and Unit 2.

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h lightning arrestor, consul

• ant has made recommendations on additional corrective measures for the station, '

r these reconenendations are being evaluated fo applicability. This will be tracked to completion by action p item 457 "60-80-07501.

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• PREVIOUS OCCURRENCES:

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'There have been two previous occurrences of Reactor trip from lightning induced voltage transients affecting

'the.-Rod Control system.

, .DYR Number Titie t, <  ;

20-1-88-240/88-023 Instrument Failures on Unit I and Reactor Trip on Unit 2 f rom tightning Induced

~D cket 456' voltage Transients.

3 20-1-89-104/89-006 Unit I and Unit 2 Reactor Trip as a Result of Lightning Induced Voltage Transient Docket 456- Af f ecting Rod Control System.

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~ Previous corrective actions are not applicabate to this event.

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G. COMPONENT FAILURE DAiA:

The event was not the result of component f ailure nor did any components f all as a result of this event.

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