ML19327C256

LER 89-022-00:from 891016-27,scrams Experienced on Channel B Reactor Protection Sys Electric Assemblies & Nuclear Steam Supply Shutdown Sys Isolated,Resulting in Loss of Shutdown Cooling.Assemblies & Output Voltages reset.W/891115 Ltr

ML19327C256
Person / Time
Site:	Hope Creek
Issue date:	11/15/1989
From:	Hagan J, Merrell A Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-022-01, LER-89-22-1, NUDOCS 8911220002
Download: ML19327C256 (6)

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o Pubhc Service Electric and Gat Company P.O. Box 236 . Hancocks Bndge, New Jersey 08038

, Hope Creek Operations -

8 i L .I November 15, 1989.

'U.:S.' Nuclear' Regulatory Commission T '

DocumentsControl' Desk'

,( Washington; DC !0555

Dear. Sir:

HOPE CREEK GENERATING STATION DOCKET No.'50-354' UNIT.NO. l' '

' LICENSEE EVENT REPORT 89-022-00

ThisLLicensee Event ~ Report is being submitted pursuant to.

the' requirements: of 10CFR50.73 (a) (2) (iv) .

Sincerely, t _

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. J. agan Gene Manager -

,.' Hope Creek Operations i AM/'

O' Attachment

-SORC Mtg.89-132 C Distribution

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LICDISEE EVDfr FIRRT s

FACILITY NAME (1)' DOCKET IDSER (2) ' FAGE (3)=

'10PE CREEK GDERATING STATIcel- 0' 5 0 0 0 3 .5 4 01 & 05  :

. TI'112 (4): loss of Shutdown Cooling Due To Reactor Protection System (RPS) Actuation - the of Deficient w

EVDTT DAE (5) 13 IOSIR (6) REPORT DATE (7) Cf!11ER FACILITIES INVOLVED (8) lOmi DAY' YEAR YEAR ** }UBER ** PIV tumi DAY YEAR FACILITY NAME(S)- DOCKET IGBER(S)

F 10 1 6 8 9 8 9 0 2 2 0 0 1 1 1 5 8 9 4, OPERATING THIS REPORT IS SUE 9GTTED PUPSUAfft 'ID '11tE PJDUIRD'.DrrS T 10CFR: '(chirk WE OR }0RE BELOW)(11) 100E (9) 5 20.402(b) 20.405(c) 50.73(a)(2) (iv) ,,_X_73.71(b)

POWER 20.405(a)(1) (i) 50.36(c)(1) 50.73(a) (2) (v) 73.71(c)

LEVEL 0 0 :0 10.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) onHR (Specify in 20.405(a) (1) (iii)- 50.73(a) (2)(i) 50.73(a) (2)(viii) (A) Abstract below

\\\\\\\\\\\\\\\\\ 20.405(a)(1) (iv) 50.73(a)(2)(ii) .__ 50.73(a)(2)(viii) (B) and in Text)

\\\\\\\\\\\\\\\\\ 20.405(a) (1) (v) 50.73(a) (2) (iii) 50.73(a) (2)(x)

LICDisEE awrACT RR WIS 13 (12)

NAME> TELEPIDE IGBER A. Herrell, Lead Engineer - Technical 6 0 9 3 3 9 5 2 3 9 (EMPLETE WE LINE KR EACl! CWR2iDTT FAIMPI IUTED IN THIS PIPORT (13)

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SUPPLDIDTTAL REKRT irru;1w? (14) YESI I folXX DATE t a u;1 w (15) 10ml DAY YEAR \\\\\\\\\\\\\\\\\\

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~ ABS'liAct (16)

On: October 16, 1989 at 1503 hours0.0174 days <br />0.418 hours <br />0.00249 weeks <br />5.718915e-4 months <br />, the "B" channel RPS Electric Protection Assemblies (EPA's) opened,.resulting in a "B" channel half scram, a "B"

.cnd."D" Nuclear Steam Supply Shutoff System (NSSSS) isolation and a loss

'of'"B" RHR which had been operating in shutdown cooling mode. Following this event, troubleshooting was initiated which included monitoring the "B EPA with external test equipment. During this troubleshooting inter-vvel, nine' (9) other identical or very similar events occurred. The i

.. troubleshooting identified the cause of the' EPA trips to be an under- l voltage signal from the Motor-Generator (MG) set. After the MG output 1

,ivoltage was adjusted using a digital volt meter, no further NSSSS iso-l12tions have occurred. These events were of minimal safety significance.

'The root'cause was determined to be resetting the MG sets voltage output E :ucing the panel meter. A contributing cause was deficient procedures.

Corrective actions include procedure changes and trending of MG sets output voltage.

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LICDISEE EVDff REPORT (IJR) '!1XT CONTDERTION -

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FACILITY NAME (1)i DOCKLT NUMBER '(2) 12R NLIBER (6) - PEE '(3) .

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- HOPE CRLIK GDERATING !TTATION '05000354 . .

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i 1y PLANT AND SYSTEM' IDENTIFICATION 9

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" General Electric -

Boiling Water: Reactor -(BWR/4)

> .ReactoriHeatJRemoval .(EIIS Designation: BO) piiMi . .

. IDENTIFICATION OF, OCCURRENCE D }2 .

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T Loss of Shutdown Cooling Due'.To Reactor Protection' System (RPS) j ,

, LActuation! nUse of.DeficientLProcedure

• - . Event D' ate: October 16, 1989 (first eccurrence)' /'

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f Event' Time: 1503: 89-144, '

i6 > ThisiLER'was initiated by Incident Report Nos.89-140, ,

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89-149,89-150,: 89-151,89-152 and 89-153 ,

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- " CONDITIONS PRIOR'TO OCCURRENCE

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Plant'in OPERATIONAL: CONDITION 15'(Refueling) Reactor Power- 0%,

Unit Load'O MWe'. Second refueling outage in progress.

. DESCRIPTION OF OCCURRENCE

' ..On October'16,.1989~at 1503 hours0.0174 days <br />0.418 hours <br />0.00249 weeks <br />5.718915e-4 months <br />, the "B". channel RPS Electric st >

' Protection Assemblies- (EPA's)' opened, .resulting- in a "B"

i channel. half-scram, a "B" and "D" Nuclear Steam Supply Shutoff System 4(NSSSS) isolation and a loss .of "B" RHR which had been operating in shutdown cooling mode. Following this event, lg , troubleshooting was initiated which included monitoring the "B" Motor-Generator'(MG) set EPA with external test equipment. The "B"5RPS. bus was placed on alternate power supply in an attempt torproclude further trips. On October 25, 1989 the "A" MG set

? l EPA's tripped, demonstrating that it was not possible to j , ' prevent.. EPA trips by resetting the RPS power supply switch. To

& . facilitate' troubleshooting, the MG sets were left in service.

(9) other identical or very similar

=During this; time, nine C A fevents occurred on the following dates and times:

October 19, 1989 2100 hours i hours ("A" channel trip) m , October'25, 1989 1710 ,

"4 October 25, 1989 2227 hours 7' October 26, 1989 2145 hours 4

October.27, 1989 0332 hours

.' October 27, 1989 0347 hours [

October 27, 1989 0927 hours t ' October 27, 1989 1119 hours ,

F October 27, 1989 1208 hours j

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iDESCRIPTION OF~ OCCURRENCE CONTINUED) d m~L.% n,

- Following the. last ' EPA trip, shutdown cooling-isolations-(which j

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.are not required:in OPERATIONAL CONDITION 4 or'5)'were disabled'

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,to. prevent;thefrepeated RHR pump trips and' system isolations.-

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The troubleshooting. identified.the cause of the EPA tripsoutput to be- v

'an under-voltageisignal from the MG set. After the MG ,.

~id a3 meter, no .further  !

/~' ' voltage:was adjusted using a digital ~ volt '

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' 'Yh dl% ' (NSSSS isolationsEhave occurred. ;l MJ LTh'elinitial event was at first determined to be non-reportable,;

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'J however<further investigation revealed that anl ambiguity in thei 1 procedural guidance. 'used in' ESF actuation determination had.

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P h' ' 4 APPARENT CAUSE'OF OCCURRENCE .s Thelproximate;cause of these events was low voltage output'from- 't

'the MG. sets-whichiallowed normal plant load variations to cause the voltage to dip-below the under-voltagebetrip setpoint of the  ;

the resetting of. "I

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l EPA's.: .The' root.cause',awas ~

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cutage using to the panel meter. A J

the.MG sets'follo'ing w W4 ,

contributing cause was deficient . procedures which specified a .t combined with a MG set voltage output .

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': tolerance which, when

. calibrated using .the panel meter, resulted in insufficient .

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< margin to the EPA under-voltage. trip setpoint.

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> "ANALYS5 ..

OCCURRENCE a L

J4' The . imperc 1 of each RPS channel was measured from the MG sets This to the it . s relays during the startup test program.

E n EPA under-voltage and j

, , !? g' , ' information was used to determine the trip points for each  !

,e ' 'over-voltage Technical Specification '

recal-N/ channel. Following the initial event, the EPAs were Tj?l .' ibrated and found to be within Technical Specifications. ,

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The bus feeding each RPS channel had been removed from service trip of the EPAs in that channel. ,

V-  : shortly before the initial restored to service following the using bus i o , . When the MG sets were at 120 VAC ky '

outages, the voltage regulators were reset required by applicable operational the panel meters as and operational procedure. Both the corrective maintenance monitoring // resetting l procedures use the MG setThese panelmeters meter in measure voltage within t

F M .theJMG output voltages. specified 2U. tolerance which, together with the tolerances fi -4

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, HOPE CREEX GENERATDG STATION 05000354

'89 .

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0 0 0 4 0F 0 5 ANALYSIS OF OCCURRENCE (CONTINUEDL

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in the procedures, resulted in insufficient margin between the MG set output voltage and the EPA under-voltage. trip setpoint.

PREVIOUS OCCURRENCES There have been no previous occurrences involving under-voltage was powered by the MG sets, trips of EPA's when the RPS

however LERs86-007.(April 20, 1986) and 87-021 (May 8, 1987) documented EPA under-voltage trips which occurred while the RPS was transferred.to the alternate power supply, rendering them vulnerable to transient voltage drops.

SAFETY SIGNIFICANCE At the time of each EPA trip, the RPS electric power monitoring

• channel was immediately restored to OPERABLE status by closing the breaker and shutdown cooling was restored to service well within the two (2) hours allowed by the Technical Specifica-tions. Since the Technical Specifications permit operation in any mode for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> with one channel inoperable, the tripping of the EPA's were.of minimal safety significance.

CORRECTIVE ACTIONS The EPA'r nere reset promptly following each trip, RPS 1

restored to operability, and shutdown cooling was restored to service well within the two (2) hours allowed by the Technical Specifications.

2. Preventive and corrective maintenance procedures which set the output voltage of the RPS MG sets have been changed to tolerance and require that the voltage be reduce the measured with a digital volt meter and the voltage set to the midpoint of the EPA trip range. The system operation procedure has been changed to require that Maintenance Department perform all checks and adjustments of the MG set. output voltages.

3. The output voltage of all RPS MG sets will be checked quarterly and adjusted if necessary until it is determined of that the output voltage is not drifting. The results these checks will be supplied to the System Engineer for trending.

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NT 11 -tion determination'will'be revised-to' correct the identi-r .fied' ambiguity..

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