ML17056B413

Summary of 910904 Meeting W/Util in Rockville,Md Re Root Causes of Failures of UPS During 910813 Event.List of Attendees & Licensee Handout Matl Encl

ML17056B413
Person / Time
Site:	Nine Mile Point
Issue date:	09/30/1991
From:	Brinkman D Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 9110040170
Download: ML17056B413 (74)

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Docket No. 50-410 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 September 30, 1991 LICENSEE:

FACILITY:

SUBJECT:

Niagara Mohawk Power Corporation Nine MIile Point Nuclear Station Unit 2 MEETING MINUTES REGARDING THE SEPTEMBER 4, 1991, MEETING TO DISCUSS ROOT CAUSES OF FAILURES OF UNINTERRUPTIBLE POWER SUPPLIES (UPS)

AT NINE MILE POINT NUCLEAR STATION, UNIT 2, DURING THE AUGUST 13,

1991, EVENT A meeting was held at the NRC One White Flint North Office in Rockville, Maryland, with Niagara Mohawk Power Corporation (NMPC) and NRC staff representatives to discuss the root causes of failures of uninterruptible power supplies (UPS) at Nine Mile Point 2 during the August 13, 1991, event.

The licensee had requested this meeting.

Enclosure 1 is a list of the meeting attendees.

The handout material used by the licensee during the meeting is attached as Enclosure 2.

During the meeting the licensee provided a description of the operation of the five UPS that failed during the August 13, 1991., event and a comparison with the five UPS that did not fail during this event.

The logic power supply for the five failed UPS was from the "B" phase of the maintenance supply while the other five units received logic power from DC power supplies.

The licensee also described the preventive maintenance activities that had been performed on the UPS units in the past as well as proposed improvements for the future which include yearly replacement of the UPS internal batteries.

The licensee also presented the results of its investigation of the failures of these UPS.

The licensee evaluated three potential causes for the failures:

(1) Voltage transient on normal AC distribution system; (2) Propagation of high frequency noise from transformer fault; and, (3) Voltage transient on station ground system.

The licensee determined that potential cause (2) was unlikely since preoperational testing had demonstrated that the UPS are not sensitive to radio frequency unless the panel doors are open and an RF source is in close proximity; also, high frequency noise from the fault would not have been transmitted through the AC distribution system since it would have been filtered away by the multiple intervening transformers.

Proposed cause (3) was also considered unlikely by the licensee since all five failed UPS displayed common behavior and furthermore other station equipment did not display failures which would have been expected if there had been a voltage transient on the station ground system.

The licensee then presented a

summary of its evaluation of the voltage transient on the normal AC distribution system and the transients effect on the UPS.

The licensee concluded that the cause of the UPS trips was due to this voltage transient (which caused the UPS logic to 9110000170 910930 PDR

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September 30, 1991 trip all five units) in combination with the degraded condition of the internal batteries.

The licensee also concluded that the UPS vendor manual was deficient in that (1) its preventative maintenance section neglects the internal batteries, (2) the four-year battery replacement statement is not included in the preventative maintenance

section, and (3) the function of the internal batteries is not clear.

The licensee presented its corrective action program.

The UPS logic power supply has been modified to make the inverter output the primary power source for the logic with the maintenance supply the backup source.

All internal logic supply batteries have been replaced and an appropriate service life/replacement schedule has been established.

On a longer term basis (post restart) the licensee will evaluate further modifications to improve access to the internal batteries and the characteristics of the circuit for switching power sources.

No decisions were reached during this meeting;

however, the NRC staff evaluated the information presented by the licensee as well as information submitted in'etters dated September 10 and 11,

1991, and subsequently issued its safety evaluation as an attachment to a memorandum dated September 16, 1991, for James M. Taylor, from Thomas E. Murley.

Enclosures:

1. List of Attendees

2. Licensee Handout Material Donald S.

Brinkman, Senior Project Manager Project Directorate I-1 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation cc w/enclosures:

See next page

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2 September 30, 1991 trip all five units) in combination with and the degraded condition of the internal batteries.

The licensee also concluded that the UPS vendor manual was deficient in that

1) its preventative maintenance section neglects the internal batteries, (2

the four-year battery replacement statement is not included in the preventative maintenance

section, and (3) the function of the internal batteries is not clear.

The licensee presented its corrective action program.

The UPS logic power supply has been modified to make the inverter output the primary power source for the logic with the maintenance supply the backup source.

All internal logic supply batteries have been replaced and an appropriate service life/replacement schedule has been established.

On a longer term basis (post restart) the licensee will evaluate further modifications to improve access to the internal batteries and the characteristics of the circuit for switching power sources.

No decisions were reached during this meeting;

however, the NRC staff evaluated the information presented by the licensee as well as information submitted in letters dated September 10 and 11, 1991, and subsequently issued its safety evaluation as an attachment to a memorandum dated September 16, 1991, for James M. Taylor, from Thomas E.

Mur ley.

Donald S. Brinkman, Senior Project Manager Project Directorate I-1 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation

Enclosures:

1. List of Attendees

2. Licensee Handout Material cc w/enclosures:

See next page DISTRIBUTION:

NRC 5 Local PDRs F. Miraglia, 12/G/18 J. Partlow, 12/G/18 S.

Varga J.

Calvo PD I-1 Reading CVogan R. A. Capra D. Brinkman OGC E. Jordan, MNBB 3701 NRC Participants ACRS (10)

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Hr. B. Ralph Sylvia Niagara Mohawk Power Corporation Nine Mile Point Nuclear Station Unit 2 CC:

Mr. Mark J. Wetterhahn, Esquire Winston 8 Strawn 1400 L Street, NW.

Washington, D.C. 20005-3502 Mr. Richard Goldsmith Syracuse University College of Law E. I. White Hall Campus

Syracuse, New York 12223 Resident Inspector Nine Mile Point Nuclear Power Station P. 0.

Box 126

Lycoming, New York 13093 Mr. Gary D. Wilson, Esquire Niagara Mohawk Power Corporation 300 Erie Boulevard West

Syracuse, New York 13202 Mr. David K. Greene Manager Licensing Niagara Mohawk Power Corporation 301 Plainfield Road

Syracuse, New York 13212 Hs.

Donna Ross New York State Energy Office 2 Empire State Plaza 16th Floor

Albany, New York 12223 Supervisor Town of Scriba R.

D. 84

Oswego, New York 13126 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, Pennsylvania 19406 Char lie Donaldson, Esquire Assistant Attorney Genera'I New York Department of Law 120 Broadway New York, New York 10271 Mr. Richard M. Kessel Chair and Executive Director State Consumer Protection Board 99 Washington Avenue

Albany, New York 12210 Mr. Hartin J.

McCormick Jr.

Plant h1anager, Unit 2 Nine Nile Point Nuclear Station Niagara Mohawk Power Corporation P. 0.

Box 32

Lycoming, NY 13093 Mr. Joseph F. Firlit Vice President - Nuclear Generation Nine Mile Point Nuclear Station Niagara Mohawk Corporation P. 0.

Box 32

Lycoming, New York 13093

ENCLOSURE 1

ATTENDANCE LIST p b, 199 ~g

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Causes of UPS Failures at NNP-2 on August 13, 1991 NAVE Donald S. Brinkman Robert A. Capra Curtis Cowgill John T.

Conway B. Ralph Sylvia Richard B. Abbott Joseph F. Firlit S.

'W. Wilczek Jr.

Bob Crandall Jack Rosenthal Tom Hurley Jim Partlow S.

A. Varga Scott Newberry Faust Rosa Kerry Johnson Angelo Harinos Tom Pohida Amil K. Julka John G. Roberts Jack C. Scarborough Nark Wetterhahn Elizabeth L. Doolittle Dave Trimble John Vinquist Darrell Eisenhut Carl Terry I. Ahmed W. Pansom D. J.

Hess Rudi Hachilek Michael Grady Kim tli1 1s Ernie Rossi Ashok Thadani Frank Ashe Al Chaffee Bob Dennig Roger Woodruff POSITION Sen>or Project llanager Director, Project Directorate I-1 Chief, Projects Branch I Region I Hanager Technical Support Executive Vice President Hgr. Engineering NN!P2 Vice Pres.

- Nuclear Generation

'ice Pres.

- l'luclear Support System Engineer IIT Team Leader Director, Office of NRR NRR Associate Director Director, Peactor Projects - I/II Chief, Instrumentation Branch Chief, Elec Systems Branch Vice President Section Chief, Section 18 Electronics Engineer Supv-Elect Design New York State - DPS Technical Assistant Office of Commissioner Rogers Attorney Technical Assistant Office of Commissioner Pemick Technical Assistant Office of Commissioner Curtiss President Senior Vice President Vice President

- Nuclear Eng Senior Electrical Engineer Director Customer Support Director Power Systems Group Manager Technical Support Reporter Director, Division of Operational Events Assessment Director, Division of Systems Technology I!T Team t1ember Chief, Events Assessment Branch Section Chief Engineer ORGANIZATION

~klRC NRR PDI-I NRC/NRR/PD I-1 NRC/Region I tliagara Mohawk Niagara Mohawk Niagara Mohawk Niagara Mohawk tliagara Nlohawk Niagara Mohawk NRC/AEOD NRC/NRR NRC/NRR NRC/NRR NRC/NRR NRC/NRR Failure Prevention, Inc.

NRC/NRR NRC/NRR Niagara Mohawk tlew York State OCN/KR Winston 5 Strawn OCN/FR Oct'1/JC MATS, Inc NUS Corp.

Niagara Mohawk NRC/NRR Exide Electronics Exide Electronics Exide Electronics Exide Electronics Associated Press NRC/NRR NRC/NRR NRC/NRR NRC/NRR NRC/NRR NRC/NRR

NAME ET>zabeth Lesly Ram S. Bhatia Masashi Yokota Gerald R. Mazetis Mary O'Driscoll Frank L. Ingram James Taylor POSITION eporter Reactor Engineer Manager Regional Coordinator Reporter Public Affairs Officer EDO ORGANIZATION 11 Journal/Post Standard NRC/Region I TEPCO NRC/EDO The Energy Daily NRC/GPA NRC/EDO

ENCLOSURE 2 NIAGARAMOHAWKPOWER CORPORATION NINE MILE POINT UNIT 2 NUCLEAR STATION NRC UPS MEETING SEPTENIBER 4, '1991

I'

AGENDA OPENING REMARKS/PURPOSE B. R. Sylvia UPS OVERVIEW R. J. Crandall ROOT CAUSE OF UPS FAILURE J. T. Conway UPS LOAD EVALUATION A. K. Julka/

R. B. Abbott CLOSING REMARKS B. R. Sylvia

UPS OVERVIEW

UPS - FUNCTIONS 3 - PHASE INPUT CHARGER SECTION - AC to DC INVERTER SECTION - DC to AC STATION BATTERIES LOSS OF NORMAL AC TRIPS - 10 (INVERTER ONLY)

Page 4

4

UPS FUNCTIONS (CONT'D)

MAINTENANCESUPPLY (3-Phase)

TRANSFERS IVIANUAL AUTOMATIC INVERTER TO MAINTENANCEIVIONITOR Page 5

NINE MILE POINT UNIT 2 UNINTERRUPTIBLE POWER SUPPLY TYPICAL SERIES (IA, IB, IC, 1D, IG)

STORAGE BATTERY l25VOC BATTERY DISCONNECT CIRCUIT BREAKER CB2 INVERTER OUTPUT CIRCUIT BREAKER CB3 DC TO AC INVERTER I

CBI

INPUT

-PHASE VOLTS AC I

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= 2V LF~ GND o>

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-28V POWER SUPPLY UPS I

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I UPS ICIRCUIT AC TO DC INPUT IBREAKfR CONVERTER MAINT.

SUPPLY CIRCUIT REAKER CB4 I

I STATIC SNITCH I

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AC OUTPUT TO CRITICAL LOAD 288-l28V 3-PHASE 688V 3-PHASE TRANSFORMER R

288-l28V 3-PHASE REGULATOR 288-l28V 3-PHASE MAINTENANCE SUPPLY

NINE MILE I-uINT UNIT 2

'NINTERRUPTIBLE POWER SUPPLY TYPICAL SERIES (IA, IB, IC, 1D, IG)

STORAGE BATTERY I25YOC I

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INPUT

-PHASE VOLTS AC I

I OC TO AC INVERTER INVERTER OUTPUT CIRCUIT BREAKER CB3 COMPARE I

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I BATTERY DISCONNECT CIRCUIT BREAKER CB2 MAINT.

SUPPLY CIRCUIT BREAKER CBI I

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AC OUTPUT TO CRITICAL LOAL 288-l28V 3-PHASE 688V 3-PHASE TRANSFORMER R

288-l28V 3-PHASE REGULATOR 288-l28V 3-PHASE MAINTENANCE SUPPLY

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LOGIC POWER EXIDE -

UPS1A UPS1B UPS1C UPS1D UPS1G B-PHASE MAINT. DC ELGAR - VPS2A UPS2B DC to DC ELGAR - UPS3A UPS3B DC to DC EXIDE -

UPS1H DC to DC Page 7

INDICATOR LIGHTS 1)

DC Undervoltage (DCUV) 2)

DC Overvoltage (DCOV) 3)

Inverter Leg Fuse Blown 4)

AC Undervoltage (ACUV) 5)

AC Overvoltage (ACOV) 6)

Frequency Failure 7)

Logic Failure Breaker Trip Logic Alarm 8)

Clock Failed 9)

Logic Power Supply Failure 10)

Overload (10 minute delay)

Module Trip

I 8'

UPS PREVENTIVE MAINTENANCE SHIFT ROUNDS FILTERS CLEANING SCR HEAT SINK GREASE ZERO CROSSING, SETPOINTS LOADS TRENDED AMBIENTTEMPERATURE (32-104 F)

ROOM TEMPERATURE 93-97 F MAX(WITHOUT HVAC)

Page 8

UPS PREVENTIVE MAINTENANCE (CONT'D)

DEVIATION/EVENTREPORT (4/3/91)

BATTERIES NOT RELIABILITY INDICATION WEIGH PERSONNEL RISK VS BENEFIT Page 9

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2. 3 INVERTER The rectifier/charger or battery OC output is the inverter input power.

This OC voltage is filtered by shunt capacitors contained in OC capacitor assemblies.

The quantity of capacitor asse&lies required varies with the KA rating of the UPS nodule, as listed here:

~M ~t~niM 30 60

100, 180 250 330

400, 450 Ca acitor Assemblies A15 A15, A16 A15 A15, A16 A15, A16, A17 A15, A16, A17 A18 OC is converted to AC by SCR switching action of the fnverter~egs-,

A1, etc.

Each adjacent pair of legs (f.e.,

A1 and A2, etc.) constitutes a bridge circuit which supplies quasi-square-wave AC to one of the primary windings of the power transformers, T1 or T2.

The 30 and 60 N modules have only one power trans-former, T1.

Component designators for 300 lQ and larger inverters are preceded by the numeral 2; e.g., 2T2.. Refer to Figure 2-2.

Secondary windings of Tl and T2 are connected so that the resultant output fs a balanced 3-phase voltage.

Each line-to-line and line-to-neutral voltage would

~ appear-as a near sine wave consisting of 12 steps.

This'wave form is filtered to provide a good sine wave at the output termfnals by the filtering action of AC output fflters, A21 (if used, A22 through A24). and by reactors, L3 through LB, connected between adjacent pairs of.inverter legs.

The inverter senses fts output voltage and regulates within 1% tolerance for a wide varfatfon fn load and OC input voltage.

Various other sensing circuits provide protectfon alarm indications.

See Tables 2-1 and 2-2 for alarm descriptions.

A redundant logfc supply, powered by the fnverter output, a separate 120 VAC bypass source.

and/or internal rechargeable sealed batterfes.

allows logic testing with no input power applfed and keeps alarms indicating for as long as any source of AC control pear fs avaflable.

A static fiCae~}ter fs part of the fnverter sensing circuits.

Whenever an UPS module irfpi. ft ast be disconnected automatically and fainedfately from the crftfcai Toaf bus.

Not providing feaeffate disconnection could result in out-of-tolereei dfsturbance of the-senA$ ve cHtfcal load.

The UPS module provides instantaneous output isolation vfa internal logfc responding to any one of a neaber of control or protectfon sfgnals that 'prograas off" all of the fnverter legs.

Thfs produces a force-coeeutated fnterruptfon of the fnverter output, assessing pmar contfnufg at the load.

Ttw following fs a lfst of ~or fnverter coeponents and hrfef description of their functfons.

2-5

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A primary function is the storage, via R-S flip-flops, of mos:

alarms and all trip functions ana one display oi

$.Iicse c--":.;.-

on card-vaunted LEOs.

2.3.2.10 Static Switch Control A13A34.

This control determines the condition of the inverter, bypass

source, and critica1 load.

It then logically determines whether or not the critical load should be transferred to the bypass source.

It also determines whether the UPS can or should be restarted depending on the UPS condition and the critical load bus.

2.3.3 Control Panel A14 This panel contains control and status display components for the entire UPS mod&-.

See Figure 2-3 5 Table 2-3 for location and description of each.

2.3.4 DC Capacitor Module, AI5 {some modules up to A18, see paragraph 2.3)

Each slide-in module contains DC filter capacitors that are fused in groups of seven capacitors.

2.3.5 AC Out ut Filter Panel A21 These Ac capacitors are connected in delta across the inverter output to filter output waveform.

The capacitors have integral interrupt overcurrent protect-ion.

2.3.6 Load Division and Interface Panel A26.

This panel provides interface beheen the card cage, A13, and the following:

a.

Load-division current transformer loop {contains burden resistors and loop-shorting relays.

b.

Coaeutation-lie)t current transforaars '(contains burden resistors}.

c.

?nverter voltage sens'.;.

(potential transformers, 3-phase).

d..Sfgaal synchron5zing node {aeunts sync node transformer).

$1own log fust sensing (contains optocoupled electrical blown fuse sensing).

R.3.7 Lo ic Power and Rel Panel A27.

Thfs panel contains positfve and negative 20 VQC paver supplies

{PSI and PS2).

These pet supplies are powered through relay A27Q, which selects inverter output (preferrod) or bypass (alternate) source.

Pos)tive and negative 18-V sealed batteries (A27BTI-ST5) are counted on this panel and are kept charged by the pe>or suppl1es.

C)rcu)t breaker A27CSI Nsconnects the battery from R-ID

>'r

iog c p~'er bus

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and iog'c plJ<el supply swircn 47SI oisconnects tne power supply's 120 VAC fnput power.

The panel also contafns card-mounted (A27AI) r lays whfch fnterface the A13 controls wfth external ftems such as cfrcuft breaker motor operators, shunt trfp cofls, and rerete monftor panel functfons..

Control battery dfscharge sensfng fs located on the A27A1 card.

(These batterfes should be replaced at 4-year fntervals.)

2.3.8 S

tern Termfnal Board Panel A30.

Thfs panel contafns termfnal boards for all external control connections.

2.3.9 Remote Alarm A30A1.

The remote alarm panel provfdes fndfcatfons of the UPS module status and has no control functfon.

Alarms fnftfated by the UPS module are as follows:

a.

TRANSFERRED TO BYPASS b.

BATTERY DISCHARGE c.

UPS MINOR ALARM d.

UPS MAJOR ALARM e,

OC UNDERVOLTAGE MARNING.

Dry contact relay closure fndfcates alarm condftfon.

Contact r atfng fs 10 VA max.,

100 Y max., 0.1 A max., res4stfve.

2.3.10 Statfc Swftch L

A33.

The statfc swftch leg contafns statfc swftch power SCRs, SCR gate drfvers, and overtemperature sensfng cfrcufts.

The statfc switch leg provfdes an unfnterrupted transfer of crftfcal load between the fnverter source and the utflfty bypass source.

2.3.11 Statfc Swftch Control Panel A34.

Thfs control panel sensei crftfcal load and bop'ss source busses for feedfng statfc swftch control card A13A34..

Power supp'lees (PSI and PS2) produce posftfve aa4 negatfve 20 VDC for statfc swftch leg (A33) and remote monftor.

2.3.12 AC Ff1ter Reactor L3-L8.

Each reactor fflters the AC output of each fnverter leg to power transformer

- Tl (and T2 when used).

2.3.13 AC Out ut Fflter Karaenfc Reactors Lg thro LII.

These reactors (fn caebfnatfon wfth A21) fflter the output waveforla.

2-11

SECTION 3

MAINTENANCE ANO TROUBLESHOOTING

3. 1 PREVENTIVE HAINTENANCE.

3. 1. I Geeera1.

7.g-A A record log should be kept which should include periodic meter readings, maintenance, and any alarms and subsequent actions taken.

Early recognitior of deteriorating performance is important DANGER HIGH VOLTAGE ONLY QUALIFIED PERSONNEL SHOULD ATTEHPT TO. SERVICE THIS EQUIPMENT.

IF INJURY DOES

OCCUR, APPLY STANDARD TREA01ENT FOR ELECTR ICAL SHOCK.

3. 1.2 Air Filters.

The air filters should be changed every 2 months(even more frequently if they are dirty).

The filters are coaxer cially available.

Filters may be safely replaced while the UPS is operating and without opening the doors.

Front filters (if so equipped) are accessible by loosening the two screws at the top corners of the hinged filte~ housing.

The retainer chain allows the filter housing to tilt forward approximately 15 cm (6 inches) for Wilter removal.

Bottom filters are accessible by loosening the wing bolts (two per filter) located on the front channel below the cabinet access doors.

%en the bolts are loosened (approximately 1.5 cm (4 inch), it may be necessary to reach under and pull the hinged filter door down from the front (there are three magnetic clasps).

The filter can now be easily replaced.

3.1.3 Lamp Test.

A lamp test may be perforaad with UPS operating.

3.1e4 Ph feal Ins ctfon.

It is recceaanded that the UPS be inspected annually for tightness of connections and for evfdence of component damage or overheating.

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ROOT CAUSE FAILURE OF UPS Page 10

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ROOT CAUSE INVESTIGATION COMMON MODE FOR EXIDE UNITS ASSOCIATION WITH TRANSFORMER FAULT INITIALINSPECTION INDICATED LOGIC TRIPPED WITH SOME ALARMLIGHT ANOMAIIES INITIALINSPECTION INDICATED MAINTENANCE SUPPLY BREAKERS OPEN 3 POTENTIAL CAUSES EVALUATED 1.

Voltage Transient on Normal AC Distribution System 2.

Propagation of High Frequency Noise From Transformer Fault 3.

Voltage Transient On Station Ground System Page 11

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PROPAGATION OF HIGH FREQUENCY NOISE UNLIKELYDUE TO PREOPERATIONAL RADIO FREQUENCY TESTING RADIO FREQUENCY ATTENUATIONTHROUGH STATION TRANSFORMERS LABORATORYTESTING TO DATE Page 12

VOLTAGE TRANSIENT ON STATION GROUND SYSTEM UNLIKELYDUE TO CONINION BEHAVIOR OF ALL 5 EXIDE UNITS BEHAVIOR OF OTHER STATION EQUIPIVIENT LABORATORYDESTRUCTIVE TESTING Page 13

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YOLTAGE TRANSIENT ON NORMAL AC DISTRIBUTION MAGNITUDE OF TRANSIENT IS WELL UNDERSTOOD COMMON TO ALL FIVE UNITS TRANSFORMER FAULT ON B PHASE B PHASE SUPPLY TO UPS LOGIC MAINTENANCE TRANSFER PREVENTED Page 14

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IM PLANT TROUBLESHOOTING RESULTS LOGIC TRIPS AT 17 VDC CORRESPONDING TO 85 VAC LOGIC SUPPLY TRANSFER AT 45 VAC LOGIC BACKUP BATTERIES WERE DEGRADED AC SUPPLY TRANSIENTS (100 - 200 MSEC) TRIP UNITS WITH DEGRADED BATTERIES AC SUPPLY LES DOES NOT TRIP UNITS LOGIC BATTERY IMPACT Page 15

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LABORATORY TESTING RESULTS LOGIC BATTERY FAILURE GROUND VOLTAGE TRANSIENTS EXTENSIVE LOGIC BOARD TESTING NO COMMON MODE FAILURES IDENTIFIED Page 16

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CONCLUSIONS IMPROPER LOGIC POWER SUPPLY DESIGN MAINTENANCE SUPPLY VS.

INVERTER OUTPUT LOGIC SUPPLY SWITCHING CIRCUIT LOGIC BATTERY INSTALLATION TRANSFORMER FAULT CAUSED MAINT. SUPPLY VOLTAGE TRANSIENT UPS LOADS DEENERGIZED DUE TO TRIP OF ALL FIVE UNITS TRANSFER TO MAINT. PREVENTED (BY DESIGN)

CAUSE OF UPS TRIPS DETERMINED TO BE MAINT. SUPPLY VOLTAGE TRANSIENT AND SWITCHING CIRCUIT CHARACTERISTIC

'ND DEGRADED BATTERY CONDITION Page 17

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CONCLUSIONS (CONT'O)

VENDOR MANUAL IS DEFICIENT PREVENTATIVE MAINT. SECTION NEGLECTS BATTERIES FOUR YEAR REPLACEMENT FREQUENCY STATEMENT FUNCTION OF BATTERIES NOT CLEAR Page 18

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CORRECTIVE ACTIONS PRIOR TO RESTART MODIFY UPS LOGIC POWER SUPPLY TO MAKE INVERTER OUTPUT PRIMARY, MAINT. SUPPLY BACKUP (COMPLETE)

REPLACE ALL LOGIC BATTERIES AND DETERMINE APPROPRIATE SERVICE LIFE/REPLACEMENT SCHEDULE (COMPLETE)

POST RESTART EVALUATE FURTHER MODIFICATIONS FOR o

IMPROVED ACCESS TO BATTERIES o

SWITCHING CIRCUIT CHARACTERISTICS ALARM LIGHT ANOMALIES Page 19

C' ll

UPS LOAD EVALUATION page 20

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5

UPS LOADS PLANTIMPACT 2VB8-UPSlA FEEDWATER, CONDENSATE, COND. BOOSTER, HEATER DRAINS MINIMUMFLOW VALVESFAILOPEN A &C TRAINS FEED PUMPS TRIP DUE TO LOW NPSH PLANTSCRAM (LOW REACTOR LEVEL)

TURBINECONTROL/

REHEATER LOADCONTROL TURBINETRIP REACTOR RECIRC FLOW CONTROL (VALVESA & B FAILLOCKED)

ROD POSITION INFORMATIONCABINET LOSS OF CONTROL ROD POSITION INDICATION ROD WITHDRAWAL INHIBIT ANNUNCIATORPOWER SUPP.LY PARTIALLOSS OF CONTROL ROOM ANNUNCIATORS MAYCAUSE LOSS OF ALL CONTROL ROOM ANNUNCIATORSWHEN ALTERNATEUPS ATTEMPTS TO PICK UP ADDITIONALLOADS IF ALLPOWER SUPPLIES ARE FULLYLOADED LOSS OF LWS COMPUTER SYSTEM (LWS, ERF, SPDS)

PARTIALL()SS ()F RADIAXBASE AND COMMUNICATION ANTENNA TURBINEBUILDINGCLOSED LOOP COOLING MAXIMUMCOOLING PORTIONS OF DRYWELL UNITCOOLERS

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UPS LOADS PLANTIMPACT 2VB8-UPS1B FEEDWATER CONTROL (VALVESFAILLOCKED)

ROD SEQUENCE CONTROL SYSTEM FULLCORE DISPLAYINOP COMBINATIONOF THE ABOVECAUSES HIGH LEVELTURBINETRIP LOSS OF PORTIONS OF DRYWELLUNIT COOLERS REACTOR RECIRC FLOW CONTROL (VALVESA & B (ROD POSITION AVAILABLE LOCKUP)

FROM 3D-MONICORE AND PMS COMPUTERS)

RECIRC PUMP DOWNSHIFT ANNUNCIATOR POWER SUPPLY PARTIALLOSS OF CONTROL ROOM ANNUNCIATORS MAYCAUSE LOSS OF ALL CONTROL ROOM ANNUNCIATORSWHEN ALTERNATEUPS ATTEMPTS TO PICK UP ADDITIONALLOADS IF ALLPOWER SUPPLIES ARE FULLYLOADED PARTIALLOSS OF PLANT PAGING SYSTEM PARTIALLOSS OF RADIAX COMMUNICATIONS PARTIALLOSS OF PAGING IN OUTLYING BUILDINGS PARTIALLOSS OF PAGING IN CONTROL BUILDINGEL. 306 INCLUDINGCONTROL ROOM (DUE TO TEMP MOD 90-057)

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UPS LOADS PLANTIMPACT 2VBB-UPS1C LOSS OF ESSENTIAL ANDEGRESS LIGHTING LOSS OF COMMUNICATION SYSTEM OPERABILITYOF MAIN STACK RADIATION MONITOR

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UPS LOADS PLANTIMPACT 2VBB-UPS1D LOSS OF ESSENTIAL AND EGRESS LIGHTING LOSS OF COMMUNICATION SYSTEM

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UPS LOADS PLANTIMPACT 2VBB-UPS1G LOSS OF PMS COMPUTERS (BOP & NSSS)

LOSS OF 3D MONICORE FUNCTIONS LOSS OF DRMS COMPUTER

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