ML20011F550

LER 90-001-00:on 900124,reactor Tripped When MSIV Failed to Reopen Automatically at 10% Closed Position,As Designed & Indicator Illuminated & Position Indication Lost.Caused by Failed Fuses.Fuses Replaced & Switch adjusted.W/900223 Ltr

ML20011F550
Person / Time
Site:	Vogtle
Issue date:	02/23/1990
From:	Hairston W, Odom R GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ELV-01340, ELV-1340, LER-90-001-02, LER-90-1-2, NUDOCS 9003060244
Download: ML20011F550 (6)

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Georgia Pow Comgaany '

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333 Pecaniont Avenue- '

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. 40 inverne% center Pa4way _

Pot,t Oftce Box 1295 -

.,  ! ,v Bamingham, A!atema 35201

' lelephone 205 808-558i'

. February 23, 1990 u mu:"edeve mwn ,

j -J- ' W. G. Hairston, lli ,

• Sen or Vce Prodent.

Nuclear Operat o,s ,

ELV-01340-0241 Docket No. 50-424 U. S.-Nuclear Regulatory Commission i ATTN: : Document Control Desk ..

Washington,- D. C. 20555 Gentlemen:

V0G'TLE ELECTRIC GENERATING PLANT LICENSEE EVENT REPORT 1

REACTOR ~ TRIP DUE TO INADVERTENT CLOSURE OF MAIN.

STEAM ISOLATION VALVE In accordance with'10 CFR 50.73, Georgia Power Company hereby submits the i enclosed. report related to'an event which occurred on January 24, 1990.

Sincerely, LU ll W. G. Hairston,'III ,

WGHilII/NJS/gm s

Enclosure:

.LER 50-424/1990-01 1 xc: Georoia Power Company -i Mr. C. K. McCoy Mrs G. Bockhold, Jr.

• Mr.-R. M. Odom Mr P.-D. Rushton 3 NORMS t

7 U. S. Nuclear Reuttlatory (pmmission e

- Mr. S. D. . Ebneter, Reg iornal Administrator H Mr.. D.'B.:Matthews, Director, Project Directorate II-3

'Mr. R. F. Aierlo, ' Senior Resident Inspector u

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LICENSEE EVENT _ REPORT (LER)

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-V0GTLE ELECTRIC GENERATING PLANT - UNIT 1- oIsIo1oIoi4l214 1 loFl 0 l5 TICLE tal REACTOR TRIP DUE TO INADVERTENT CLOSURE OF MAIN STEAM ISOLATION VALVE EVENT DAf f (Si LER NUMBER (61 REPORT DAf t (71 OTHER F ACILITit$ INVOLVED (8)

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NAME TE LEPHONE NUMBER ARI A COOf R. M. ODOM/ NUCLEAR SAFETY AND COMPLIANCE 41014 8121 61-13 12101 1 COMPLETE ONE LINE FOR E ACH COMPONENT F AILURE DESCRIBIO IN THit REPORT (131 naPoRta e CAust SYSTEM COMPONtNT Mjjf,AC y qpn CAust SYSTEM COMPONENT "j%^C REPORf y pp A E l

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On 1-24-90, partial stroke testing of a Main Steam Isolation Valve .(MSIV) was in progress. During a previous test, the valve had failed to reopen automatically at the 10% closed position as designed. ' As a result, plant personnel were prepared to install a jumper to reopen the valve if it failed to reopen automatically. The test began and an indicator illuminated at approximate 1y'10%

closed; however, unknown to the personnel involved, there were two . limit switches which were not adjusted to actuate concurrently. Consequently, when the indicator. illuminated, the other limit switch had not yet actuated and it l appeared that the valve would not reopen automatically. The jumper was l installed to initiate valve reopening; however, position indication was lost and the MSIV went fully closed. MSIV closure resulted in a rapid decrease in water level in Steam Generator (SG) #4 to the low-low level setpoint and an automatic reactor trip occurred at 0133 CST.

l An investigation determined that when the jumper was installed, the MSIV control L fuses failed, which caused the valve to close.

L Corrective actions include: a) fuse replacement, b) procedure revision to include a caution that the indicator may light prior to the valve receiving the l.' reopen signal, and, c) limit switch adjustment to obtain concurrent actuation. .

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i A. REQUIREMENT FOR REPORT This report'is required per 10.CFR 50.73 (a)(2)(iv) because an unplanned i actuation of the Reactor Protection System occurred. ,

B. UNIT STATUS AT TIME OF EVENT p,

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' At the time of this event, Unit I was operating in Mode 1 (Power Operation) at 90% of rated thermal: power. Other than that described herein, there was-

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no inoperable equipment which contributed to the occurrence of this event. ,

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C. DESCRIPTION OF EVENT j 1

On 1-24-90, partial stroke testing of Main Steam Isolation Valve (MSIV) j 1HV-3036A was-in progress in accordance with Procedure 14842-1, " Main Steam 1' Isolation Valves Partial Stroke Inservice Test". 'During a previous quarterly test in August 1989, the valve did not automatically reopen as  !

designed when it reached the 10% closed position. Electricians had been 1 assigned to the auxiliary relay-panel to assist during the test. Their responsibility was to install a jumper to reopen the valve if it did not-automatically reopen at the 10% closed position. If the valve reopened as a

. result of the jumper, this would. confirm that a failed contact was the.cause of the failure to reopen automatically. The test began and at approximately 10% closed, the blue light indicator came on in the control room but the >

valve continued to close because the limit switch which initiates reopening  ;

had not yet actuated. The electricians were advised and they-installed the jumper to initiate valve reopening. As they installed the jumper, position

~ indication was lost and the MSIV continued to the full closed position.

t' Closure of the MSIV resulted in a rapid decrease in water level in Steam Generator (SG) #4. The level decreased to the low-low water level setpoint and an automatic ~ turbine / reactor trip occurred at 0133 CST. The Main Feedwater System isolated-and the Auxiliary Feedwater System actuated as designed. Atmospheric Relief Valve (ARV) 1PV-3030 opened' to control pressure in SG #4. Control room operators responded properly to control SG

. water levels. Steam dump valve ITV-500C indicated not fully closed and g control room operators initiated a Main Steam Line Isolation (MSLI) on the remaining three steam lines to limit the Reactor Coolant System (RCS) cooldown rate.

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nxw- w.e e-.a. .~ mc r- , saw nm p As:the generator tripped off the grid, unit power transferred from the Unit-Auxiliary Transformers (UATs) to the Reserve Auxiliary Transformers.(RATS). .

However, a non-safety related 4160 volt bus, INA04, failed to transfer.and..

;. power was lost to its connected loads. These included the Turbine Plant-Cooling Water (TPCW) pump-#1 discharge valve, air compressors, and condenser vacuum breakers. While attempting to re-connect the loads to other buses, l control room operators found they were. unable to open breaker INA04-09, so this was done locally.

Additional' discrepancies noted were a low flow alarm from the Auxiliary-Component Cooling Water (ACCW) System, and a Service Air System failure to isolate.

D. CAUSE OF EVENT

1. A review of the MSIV design revealed that there' are two limit switches ,

which were not adjusted to actuate concurrently. When the blue light

-illuminated as the result of one limit. switch actuating, the other limit I switch had not yet actuated and it appeared that the valve had f ailed to reopen. When the electricians installed the jumper,-the MSIV control power fuses failed, resulting in closure of the MSIV.

2. The MSIV closed when its actuator fuses blew. ' Although a simulation of l the event failed to duplicate the blown fuses and MSIV closure, it is our engineering judgement that the Georgia-Power Company electricians inadvertently created a momentary electrical short which led to the blown fuses. - This apparent cognitive personnel error was not the result

, 'of failing to follow approved procedures' or the result-of any unusual characteristics of the work location.-

3. The cause of the INA04 bus failure to transfer was due to the failure of the alternate feeder breaker from the RAT to close. This was the result of burnt relay contacts which did not allow an adequate electrical connection. The burnt contacts were due to the relay being out of ,

adjustment.

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1. 4. Steam dump valve ITV-5000 closed properly. However, the position  ;

indication was faulty due to a limit switch being out of adjustment, t

5. The inability of the control room operators to open breaker INA04-09 was j

, due to a faulty.handswitch. An examination'of the handswitch concluded ,

that the failure was an isolated incident.  !

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6. The cause of the ACCW low flow alarm was a momentary loss of power which  !

occurred during load transfer.

7. The failure of the Service Air System to isolate will be investigated l during the refueling outage which is scheduled to begin February 23, k 1990.

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E.' ANALYSIS OF EVENT i

The'MSIV went:to its safe (fail close) position upon loss of power when the  ;

control power- fuses blew. Main Feedwater isolated and Auxiliary Feedwater  !

' actuated as-designed and a normal reactor trip occurred. Control room l

operators responded properly to stabilize SG water levels during the trip l recovery. Based on these considerations, there was no adverse effect on

' plant safety or the health and safety of the public~as a result of this

• event, j

-F. CORRECTIVE ACTIONS i

' 1. The blown fuses were replaced and Procedures 14842-1 and 14842-2 have' been revised to require that the MSIV control room handswitch be moved to the "open" position upon receipt of blue light indication. This indication ensures that the. valve has actuated and represen_ts completion j of the ' quarterly stroke test. Initiation of the automatic reopening is '

not required to be tested. Additionally, a caution note will be added to the procedure stating that the blue light'may actuate prior to the  !

valve receiving the reopen signal. Finally, during the 1990 refueling l outages (Units 1 and 2),. the appropriate limit switches will be adjusted -[

to actuate concurrently.

2. The electricians involved have been counseled regarding the necessity of -!'

exercising caution when testing circuits having the potential for causing a reactor trip.

3. The relay with the burnt contacts in the RAT feeder breaker has been

replaced and the new relay has been adjusted to prevent recurrence of this failure, f 4. The steam dump valve limit switches were readjusted. '

5. 'The faulty handswitch which resulted in the inability to open breaker INA04-09 has been replaced.

6. A design change is being investigated to eliminate the ACCW low flow

':7 alarm as a result of a momentary loss of power. We expect to have a course of action identified by 3-1-90.

7. Corrective actions to prevent recurrence of the Service Air System's failure to isolate will be based on the results of the investigation to

, be performed during the refueling outage which is scheduled to begin 2-23-90.

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1 G,' ADDIT 10NAL INFORMATION-7 L1)- Failed Components: 3

.a) 'INA04-09 Handswitch manufactured by Electro Switch Corp, rA.

Model #-32762M-105- d b). INA04 Relay manufactured by Gould Controls l Model # 191921T6-R.2 .

2) Previous Similar Events: , I

-LER 50-424/1989-018, dated 10-30-89. q Although this 1989. event progressed similarly following fuse failure,

'there was no personnel involvement, and the corrective actions were not Lapplicable- to- the prevention of the 1-24-90 event.

13) Energy Industry Identification System Code:

lc. iMain-Steam System - SB  :

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ll Service Air System - LF- -

Main Feedwater System - SJ ,

Reactor: Coolant System - AB 1?

L Auxiliary Feedwater System - BA 4

4160 Non-lE Electrical System - EA Turbine Plant Cooling Water System - KB D Auxiliary Component Cooling Water System - CC  ;

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