ML18093A553

LER 87-015-00:on 871127,engineering Review of Plant Electrical Sys Revealed Potential for Inadequate Voltage in Motor Control Circuits to Pickup Starter Coil.Caused by Inadequate Design Review.Circuits corrected.W/871224 Ltr

ML18093A553
Person / Time
Site:	Salem
Issue date:	12/24/1987
From:	Pollack M, Zupko J Public Service Enterprise Group
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
LER-87-015-02, LER-87-15-2, NUDOCS 8801040591
Download: ML18093A553 (6)

Text

NllC Fet., . . .U.1. NUCLIAll llEGULAl'ORY COMlllDION l~l ...-ovED Oli9 NO. 31111-0104 LICENSEE EVENT REPORT CLER)

PACILITY NAME 111 IDOCKIT fllUMaEll 121 I r-~E (;JI Salem Generating Station - Unit 2 I O I 5 I O I O I O h I 1 I 1 I 1 IOFI n Ii; TITLE (4)

Potential for certain SW MCC control circuits to oick-uo*starter coil* In~n. n~~;nn R~v-IVINT DATI 1111 Liii NUll9Ell l*l

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-- ID.731all211U I0.7Slall211UI I0.731all2Hllll LICENSEE CONTACT FOR THll LEll 1121 foiAME AREA CODE M. J. Pollack LER Coordinator 6 10 I 9 3 I 31 91- 14 I 0 12 12 COMPLETE ONE LINE FOii EACH COMPOfoiENT FAILUllE DHCllllED IN THll llEl'OllT llSI CAUSE SYSTEM COMPOfoiENT MANUFAC*

TUR ER I I I I I I I I I I I I I I I I I I 1* I I I I I I I I I MONTH DAY 'fJAR EXPECTED n YES (If,.... i:omplfto EJCPECTEO SU!lllSS/ON OATEJ hcl NO SUBMISSION DATE 1151 I I I On November 27,

• 1987 an Engineering review of Salem electrical systems revealed that with a degraded grid condition, a LOCA and assuming the 13.8 KV to 4 KV station power tap changer fails to function, certain MCC control circuits {EDl may not have adequate voltage to pick-up their respective MCC starter coil. To assure pick-up by the starter coil, 89% of the 115 VAC is required as per manufacturer specifications. The root cause of this event is inadequate design review of control circuits for degraded voltage conditions. As applicable, modifications to correct the electrical concerns included the addition of interposing relays to lessen the control circuit voltage drop and enhancement of the power circuit conductor. size which increased the bus voltage available at the MCC. The Unit 2 analysis and modifications are complete. The Unit 1 analysis is continuing and modifications are being*made as applicable. *Unit 1 is currently in a refueling outage and will not .*be returned to service until ~completion of the

.eneineering analysis and applicable design modifications.

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LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 87-015-00 2 of 5 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as f xxl IDENTIFICATION OF OCCURRENCE:

Potential for certain Service Water (SW) Motor Control Center (MCC}

control circuits to not have adequate voltage to pick-up their respective MCt starter coil - Inadequate Design Review Event DatE:: 11/27/87 .**. 1 Report Date: 12/24/87 This reporL was initiated by Incident Report Nos.87-458 and 87-471 CONDITIONS PRIOR TO OCCURRENCE:

Unit 1(2} - Mode 6 Defueled (5) Reactor Power 0% Unit Load 0 MWe DESCRIPTION OF OCCURRENCE:

On November 27, 1987 an Engineering review of Salem electrical syste~s revealed that with a degraded grid condition, a LOCA and assuming ths 13.8 KV to 4 KV station power tap changer fails to function, certain MCC control ci1cuits {ED} may not have adequate voltage to pick-up their respective MCC starter coil. To assure pick-up by the starter coil, 89% of the 115* VJ..C is required as per manufacturer specifications. Upon discovery of the MCC control circuit concerns, a

four hour no~ification" to the Nuclear Regulatory Commission was made at 1655 hours0.0192 days <br />0.46 hours <br />0.00274 weeks <br />6.297275e-4 months <br /> on November 27, 1987 in accordance with 10CFR 50.72(b) (2) (iii} (D).

APPARENT CA.USE OF OCCURRENCE:

The root cause of this event is inadequate design review of control circuits for degraded voltage conditions.

The Salem Generating Station Updated Final Safety Analysis Report (UFSAR) Section 8.3, "ONSITE POWER SYSTEM"_ states:

"The Offsite Power System in combination with the onsite distribution has beeri shown by analysis and test to possess sufficient capacity and capability to automatically start and subsequently operate all safety loads within their voltage ratings for anticipated transients and accidents . . . . . "

ANALYSIS OF OCCURRENCE: -~~*

Engineering investigations of the degraded voltage concerns have shown certain equipment motor control center starters to potentially not be operable due to a potentially degraded voltage of ~ 102 Volts. The

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LICENSEE EVENT REPORT (LER} TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 -5000311 87-015-00 3 of 5 ANALYSIS OF OCCURRENCE: (cont'd) control circuits may not pick-up the starter coil should a degraded voltage condition exi~t on the 4KV Bus. The studied worst case included the 4KV Bus voltage to be at the 91.6% of 4160 volts which is the setting of the degraded grid protection relay. If the degraded voltage is less than 91.6%, the degraded grid relay would pick-up and transfer all loads to the Emergency Diesel Generator which would restore the 4KV Bus voltage back to 100% of rated voltage.

The equipment motor control center starters which could be affected by the degraded voltage condition include the following:

All SJ54 valves ("Accumulator Outlet Valves"} - these motor operated valv2s are normally open during plant operation and are not normally operated during any phase during the recovery from a

~ass cf Coolant Accident (LOCA);

During a small break LOCA, the SJ54 valves are closed in order to allow faster Reactor Coolant System (RCS) {AB}

depressurization so the RCS leak can be isolated. However,*

if the valves do not close, then leak isolation will take longer and greater RCS will be released to Containment.

Both SJ49 valves ("RHR Discharge Valves to Cold Legs"} - these motor operated valves are normally open during plant operation; upon initiation of cold leg recirculatior. (approximately 14 minutes post LOCA), one of the SJ49 valves is closed in order to supply a containment spray header; The Containment Spray System is 100% redundant to the Containment Fan Coil Units in providing Containment depressurization and cooling after a LOCA. Therefore, if the one SJ49 valve does not close, Containment cepressurization and temperature control will be maintained.

All three (3) Con~rolled Area Air Conditioning System (CAACS)

Supply Fans {VI} - these fans supply the Controlled Access Area with filtered air conditioned air; during a LOCA, the Control Room is supplied separately with high efficiency filtered air via the Emergency Air Conditioning System (EACS} supply fan; Nos. 11(21} and 13{23) Service Water Ventilation Exhaust Fans -

these 10 hp fans are designed to maintain the SW Intake Structure ambient temperature to less than 95°F during worst case summer conditions to ensure the continued reliable operation of the SW Pumps.

No. 14(24) RHR Sump Pump - This pump is one of four (4) pumps used to control the RHR Sump level to protect the RHR Pump Room from flooding. There are two sump pumps per RHR sump; During a LOCA, the RHR Sump Pumps are locked out for the first twenty minutes or until the SEC and the 230 volt MCC is reset.

LICENSEE EVENT REPORT (LER} TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 87-015-00 4 of 5 ANALYSIS OF OCCURRENCE: (cont'd}

The other RHR Sump Pumps are not effected by the.voltage degradation due to their circuit links being longer. The voltage drop to the pump motor starter is less.

No. 11(21) Control Room Emergenc-y Air Conditioning Supply (CREACS} {VII Fan - This fan is required to operate in the event of a LOCA, however, No. 12(22) CREACS Fan is not affected by the degraded voltage concern and is 100% redundant; All SW20 valves (Service Water Header Supply Valves"} - These motor operated butterfly valves are normally open. The 11(21) and 13(23) valves are on the Turbine-Generator supply header

{which isolate on receipt of the SI signal) and the 12(22} and 14(24) valves are on the nuclear header; If the Turbine-Generator supply header valves do not close upon receipt of the SI signal and a single active failure involving the SW26 valve {"Turbine Area SW MOV Stop Valve")

failure to close occurs, SW to SI equipment cannot be guaranteed until either the SW26 or the SW20 valves are manually closed.

During a LOCA the accident analysis assumes that a passive fQilure will not occur for the first thirty minutes after initiation of the accident. Therefore, a SW nuclear header pipe break cannot be assumed to occur for the first 30 mirnites.

All SW17 valves ("SW Pump Discharge Header Crossover Valve"} -

These motor operated butterfly valves, one per Service Water Header (two (2) headers), provide cross connection or isolation of the headers as needed. They are normally open; and Nos. 11(21) and 12(22} Service Water Screen Well Sump Pump -

Each of these pumps remove water from a respective SW Bay to protect the SW Pumps from flooding concerns.

It should be noted that if a LOCA condition existed, all Safety Injection {SI) equipment loads would have started prior to the subsequent Generator trip and Group Bus transfer from the Auxiliary Power Transformer to the Station Power Transformers {SPTs). This would indicate that a degraded 4KV Bus voltage condition would not have existed at the onset of the LOCA. From previous plant operation-and testing; it is apparent that all equipment {starters) would operate {pick-up) as required during the initiation of an SI since the 4KV Bus voltages would recover to 100-105% after SI equipment motor starting. Approximately 30 seconds after the SI, a Generator trip and group bus transfer would occur. This will cause the steady state 4KV Bus recovery voltage to drop to approximately 94%. If the SPTs automatic tap changer was non-functional and should a degraded 500 KV System condition occur during this time, it is possible to be at a point where the 4KV System voltage would be depressed to its *,.*.

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Sale~ Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 87-015-00 5 of 5

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design limitaticn of 91.6% and would not be assurred of recovery back to 100% when no credit is taken for the automatic tap changer.

The PSE&G Engineering review has indicated that most of the equipment which has been modified would have operated as required with degraded voltage conditions as discussed above. PSE&G testing has indicated that size one and size two starters pick-up at voltages between 70 and SO volts inste~d of the "guaranteed" voltage of 102 volts. Size three starters ~ave been shown to pick up at volfages between 90 and 96 volts. Also, the conservative nature of the calculations was the basis for accep~ance. For example we have modeled the control circ~its at high2r than expected temperatures and the control power transformer resistance has been modeled at higher than expected temperatures thereby giving a very conservative control circuit voltage drop analysis.

CORRECTIVE ACTION:

The Unit 2 SJ valves, CAACS Supply Fans, the RHR Sump Pump, and I

Control Room EACS Supply Fan starters have been modified by the .. 1 I

addition of interposing relays to lessen the control circuit voltage drop.

The Unit 2 SW valves and the SW Screen Well Sump Pumps starter concerns have been addressed by enhancement of the power circuit by increasing the power circuit conductor size thereby increasing the bus voltage available at the MCC.

The Unit 2 starter concerns for the SW Vent Fans was addressed by using bo~h corrective actions stated above.

EngiLcering analysis of the Salem 0nit 1 electrical systems is not complete. As a mininu~ the modificatidns made to the Unit 2 equipment, identified above, will be made to the comparable Unit 1 equipment as applicable. Currently, Unit 1 is in a refueling outage and will not be returned to service until completion of the engineering analysis and applicable design modifications.

Gen<t:'t:!:-9

• Salem Operations MJP:pc SORC Mtg.87-114

e OPS~G Public Service Electric and Gas Company P.O. Box E Hancocks Bridge, New Jersey 08038 Salem Generating Station

• December 24, 1987 U. S. Nuclear Regulatory Commission Docu~ent Control Desk Washing~on, DC 20555 SALEM GENERATING STATION LICENSE NO. DPR-75 DOC~~T NO. 50-311 UNIT NO. 2 LICEN~EE EVENT REPORT 87-015-00 This License~ Event Report is being submitted pursuant to the requ.ir::::::1*:2r::.~.s cf Nuclear Regulatory Commission requiremer.ts 10CFR

50. 7 J ( <::.) ( .'.2) ( ::._) ( B} . This report is required within thirty days of Sincerely yours, General Manager-Salem Operations MJF:pc Distribution The Energy People 95-2189 111 MJ 12-84