ML18036A754

Insp Repts 50-259/92-15,50-260/92-15 & 50-296/92-15 on 920420-24,0504-08 & 0518-22.Violations Noted.Major Areas Inspected:Design of Electrical Sys & Related Engineering & Maintenance Activities

ML18036A754
Person / Time
Site:	Browns Ferry
Issue date:	06/17/1992
From:	Breslau B, Julian C NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
Shared Package
ML18036A752	List: ML18036A751 ML18036A753 ML18036A754
References
50-259-92-15, 50-260-92-15, 50-296-92-15, NUDOCS 9207010346
Download: ML18036A754 (50)

See also: IR 05000259/1992015

Text

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UNITEDSTATES

NUCLEAR REGULATORY COMMISSION

REGION II

101 MARIETTASTREET, N.IN.

ATLANTA,GEORGIA 30323

Report Nos.: 50-259/92-15,

50-260/92-15,

and 50-296/92-15

Licensee:

Tennessee

Valley Authority

6N 38A Lookout Place

1101 Harket Street

Chattanooga,

TN

37402-2801

\\

Docket Nos.:

50-259,

50-260,

and 50-296

License Nos.:

DPR-33,

DPR-52,

and

DPR-68

Facility Name:

Browns Ferry Units 1, 2,

and

3

. Inspection

Dates: April 20-24,

Hay 4-8,

and Hay 18-22,

1992

Inspectors:

. Breslau,

Team Leader

Team Hembers:

P. Fillion

G. HacDonald

E. Christnot

S. Rudisail

Da e Signed

NRC Consultants:

F. Nuzzo,

AECL

B. Pendelbury,

AECL

G. Skinner,

AECL

A. Gibson, Director, Division of Reactor Safety

C. Julian, Chief, Engineering

Branch

C. Patterson,

Senior,

Resident

Inspector

H. Shymlock, Chief, Plant Systems

Section

J. Williams, Project Hanager,

NRR

ate S'gned

Approved by:

C.

u ian, Chief

Engineering

Branch

Division of Reactor Safety

Accompanying

NRC Representatives

Hay 21-22,

1992:

SUHMARY

Scope:

This Special

announced

inspection

was conducted

in the areas of design of

electrical

systems

and related engineering

and maintenance activities.

NRC

Temporary Instruction 2515/107,

"Electrical Distribution System Functional

Inspection

(EDSFI)", issued

October 9,

1990, provided guidance for the

inspection.

920701034b

920bi8

PDR

ADOCK 05000259

8

PDR

Results:

In the areas

inspected,

one violation was identified.

The violation involved

failure to have

an adequate

procedure for setting the Unit Station Service

Transformer tap setting switch (paragraph 2.2.1.2).

A summary of team findings is provided in Appendix A and will be identified as

Inspector

Fol 1 ow-up Item'IFI) 50-259,260,296/92-15-02.

TABLE OF

CONTENTS

PAGE

EXECUTIVE SUMMARY................................=.......................

1 .0

INTRODUCTION..........................................4...........

2.0

ELECTRICAL SYSTEMS......................................

2.0. 1

EDS Description.............................

2.0.2

EDS Review..................................

Concluslonsooooooo

~ .oo...oo.ooooooo...

~ ....oo.oo.o

0ffsite power.....................................

2.2. 1 Degraded

Grid Voltage Protection............

2.2. 1. 1 Calculations for Bus Voltage During

Sequencing.'.....................

2.2. 1.2 Procedures for Setting

The

USST Load

Changer Selector Switch.........

2.2. 1.3 Surveillance Instructions for Calibr

the Degraded

Voltage Relays.....

2.2. 1.4 Available Equipment Terminal Voltage

Degraded

Grid Conditions........

2.3

Medium Voltage and Safety Related

480 Volt Systems

2.3. 1'Short Circuit Calculations..................

2.3.2 Containment Electrical Penetrations...

.. ..

2.3.2. 1 Continuous Loading............ .....

2.3.2.2 Short Circuit Loading...............

2.3.2.3 Protective

Device Coordination......

2.3.3

Medium Voltage Protection

and Coordination..

2 .3.4 480 VAC.....................................

2.3.4. 1 Short Circuit Anal'ysis....

. .......

2.3.4.2 Protective

Device Coordination......

2.3.4.3

Load Voltages.......................

2.3.4.4

Ground Fault Detection System.......

2.3.5 120/208 VAC.................................

2.3.5. 1 Short Circuit Analysis..............

'2.3.5.2 Protective

Device Coordination......

2.3.5.3

Load Voltages.......................

2.4

Emergency Diesel

Generators. r.....................

2.4. 1 Static Loading Analysis.....................

2.4.2 Dynamic Loading Analysis....................

2.4.3

DG Protection

and Controls..................

2 .5

DC Systems........................................

2.5. 1 Short Circuit Analysis......................

2.5.1.1

250 VDC.........................

2.5. 1. 2 '125 VDC..............................

2.5.2 Batteries

and Battery Charger...............

2.5.2.1

250 VDC.............................

2 ~ 5 ~ 2 ~ 2 125

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Device Coordination..............

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Load Voltages...............................

2.5.4. 1 250 VDC.............................

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2.5.4.2

125 VDC.......................................

16

2.5.4.3

DC Systems

Ground Fault Protection............

17

3.0

HECHANICAL SYSTEHS....................................

3..1

Concl usi ons

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.2

Diesel Loading...................................

3.3

Diesel Air Start System....'..'....................

3.4

Jacket

Cooling System............................

3.5

Emergency

Equipment Cooling Mater System.........

3.6

Diesel Oil System........................-.......

3.7

Heating Ventilation and Air Conditioning........

3.7. 1 Diesel Generator

Room Ventilation.........

3.7.2 Tornado Generated

Missile Strike and Depre

protection................................

3.7.3

DG Room Battery

Fume Hood.................

3.7.4 Battery

Rooms

152 Ventilation Requirements

3.7.5 Diesel

Engine Intake

and Exhaust Piping An

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21

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21

4.0

HAINTENANCE, TESTING,

CALIBRATION, AND CONFIGURATION CONTROL

.1

Conclusions...........................................

4.2

Equipment Walkthroughs................................

4.3

Equipment Haintenance,

Testing,

and Calibration.......

4.4

Emergency Diesel Generator

Preventative

Haintenance...

...

22

...

22

...

23

...

25

...'6

5.0

ENGINEERING AND TECHNICAL SUPPORT............

5.1

Conclusions............................

5.2

Organization

and Staff.................

5.3

Haintenance

and Operations Support.....

5.4

Problem Identification and Resolution..

5.5

Hodifications..........................

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6.0

EXIT HEETING............................................-.........

229

Appendix A: Findings

Appendix B: Acronyms

and Abbreviations

Appendix C: Persons

Contacted

EXECUTIVE SUMMARY

A Nuclear Regulatory

Commission

(NRC) team conducted

an Electrical

Distribution System Functional

Inspection

(EDSFI) at the Browns Ferry nuclear

station.

This inspection

was performed

by Region II staff and consultants

from April 20 to May 22,

1992.

The objective of this inspection

was to assess

the capability of the

EDS to perform its intended functions during all plant

operating

and accident conditions.

A secondary

objective was to assess

the

performance of the licensee's

engineering

and technical

support groups in

activities related to the design,

maintenance

and operability of the

EDS.

The team's

inspection

addressed

design, calibration, maintenance,

and the "as

installed" configuration of the

EDS including associated

mechanical

systems

and equipment.

The areas

inspected

by the .team were the 500

kV and

161

kV

transmission

systems

and switchyard; the 500- to 20.7-kV and 20.7- to 4.16kV

unit station service transformers;

the 161- to 4. 16

kV common station service

transformers;

the 480

V system;

the 250/125

VDC systems;

and the

120

VAC

instrument

buses.

Mechanical

systems

included electrical

equipment

rooms,

HVAC, the emergency diesel

generators,

and support 'systems.

The team's

conclusions

and findings for the systems

and, areas

inspected

are

summarized

in

the following paragraphs.

The team concluded that offsite power

was flexible and reliable

and that the

onsite

EDS was generally in compliance with the TS/FSAR/SER.

Design

documentation

including calculations

and analyses

were available

and

retrievable.

The design

was supported

by a knowledgeable

team

and

a

comprehensive

set of calculations.

However,

a few calculations

contained

errors or omissions,

but these

were considered

exceptions

to an otherwise

good

quality calculation program.

In addition, the team noted that

some procedures

relative to the operation

and surveillance of the

EDS could have resulted

in

unanalyzed

or undesired

operating conditions.

A violation was identified in

this area.

Design of mechanical

systems

supporting the

EDS was adequate.

However, the

air start

system relied

on

a single check valve as

a pressure

boundary for the

safety related portion.

The licensee

had independently identified the

weakness

and initiated

a revision to their Surveillance Instruction.

In the area of seismic qualification, the air receivers

in the

DG air start

system were not formally qualified to sustain

seismic events.

Even though the

EECW was adequately

protected

from external flooding events,

the dewatering

sump

pump and the grating at the top of the concrete

were not qualified.

Also

the

DG Room Battery

Fume

Hood was not seismically qualified.

However, all

DG

support

systems

came under

NRC Unresolved Safety Issues

A-46.

Several

undocumented

assumptions,

inconsistencies

and reference

errors

were

noted in the calculation that determined

hydrogen concentration

in Battery

Rooms

1

& 2.

The licensee

revised the calculation;

a review of the

preliminary calculation indicated that the ventilation was adequate.

In the area of configuration control, the team identified several

discrepancies

between the "as installed" molded case circuit breakers

and the

design drawings.

The team noted

a potential configuration control problem

with br'eaker

change

out in the 480

V shutdown boards.

The licensee identified-

two non IE General Electric type AK circuit breakers

located in 1E shutdown

boards.

A,problem evaluation report

had already

been issued.

Several

instances

were noted of improperly terminated

spare wiring in the

250

VDC RNOV boards

and in several

main bank battery chargers.

Additionally, two

SDB battery charger

disconnect

switches

were incorrectly left in the "on"

position.

Two drawing discrepancies

were noted in the thermal

overload

setting drawings.

The team noted

a weakness

in the fuse control program

regarding fuse labelling.

The licensee initiated corrective actions.

Walkthrough inspections

determined that the material condition of the plant

equipment

was good.

However, cracked

thermal 'overload relays were found in

the 480

V and

250

VDC RNOV boards

and

a cracked

fuse block was found in a 480

V RMOV board.

Additionally the

SDB battery

C had

a degraded intercell jumper

cable.

The licensee initiated corrective actions.

Housekeeping

was generally

good in the switchgear,

motor control centers

and

electrical cabinets.

The equipment

was clean

and properly maintained.

An

exception

was battery board

2 where several

examples of poor housekeeping

and

excessive dirt were noted.

In the area of preventive

maintenance,

the team noted that the bus insulation

on the

4 kV shutdown

boards

was not being inspected.

.The licensee

was

utilizing thermography for checking

bus connections,

and this was identified

as

a strength.

The team noted that the maintenance

records

and procedures

for

4

kV and 480

V switchgear maintenance

were adequate.

Protective relays were being calibrated

on

a scheduled

basis.

In the area of

testing

and surveillance the team noted that the licensee

had implemented

an

adequate

program for testing molded case circuit breakers

which encompassed

all safety related breakers.

Battery discharge tests

revealed that several

batteries

were nearly at the

replacement

point.

The licensee

indicated that they had design

change

packages

to replace

many of the batteries

during the upcoming refueling

outage.

A procedure

inconsistency

in battery post terminal torque

requirements

was noted in the

DG battery discharge test procedure.

In the area of testing

and surveillance for the

DGs, the team found these

functions were adequately

accomplished.

Maintenance

and operations

support

was adequate.

The System -Engineering

group

in particular was cognizant of system

and component function and performance.

The group provided strong support for EDS activities

and involvement in

problem identification and resolution

was good.

Planned modification

activities were appropriately controlled

and documented.

In general,

responses

and proposed corrective actions

were appropriate.

1.0

INTRODUCTION

'revious inspections

o'f nuclear

power plants

by NRC teams,

and various

LERs have identified conditions in the

EDS at various operating

plants

that could compromise the design safety margins of the. plants.

This

resulted, .in part, from a lack of proper engineering

and technical

support,

which resulted in the introduction of various design

deficiencies during the initial design or subsequent

design

modifications of the station

EDS.

Examples of some of these

deficiencies

were unmonitored

and uncontrolled load growth on s'afety-

related

buses,

inadequate

modifications, technically inadequate

calculations,

incorrect facility configuration,

inadequate

testing,

improper application of, commercial

grade

components,

lack of fuse

control,

and improperly installed electrical

connections.

The primary objective of this inspection

was to assess

the capability of

the Browns Ferry

EDS to perform its intended functions during plant

operating

and accident conditions.

A secondary

objective

was to assess

the capability 'and performance of the licensee's

engineering

organization in providing engineering

and technical

support to'DS

activities.

The team reviewed the Browns Ferry

EDS design with respect to regulatory

requirements,

licensing

commitments

and pertinent industry standards.

The

EDS components

reviewed included the 500

kV and

161

kV transmission

system

and switchyard; the 20.7

kV system;

4. 16

kV system;

the 480

VAC

system;

the 250/125

VDC systems;

and the

120

VAC instrument

buses.

- Mechanical

systems

reviewed included electrical

equipment rooms'VAC,

~the emergency diesel

generators,

and support

systems.

Within this report

FINDINGS are identified and are defined

as follows:

FINDINGS are facts or conclusions related to how well the electrical

distribution system meets its intended function.

FINDINGS may indicate

a requirement

or an accepted

industry practice that was not fully

implemented.

FINDINGS may indicate discrepancies

or omi'ssions

in

documents

where these

problems

could credibly result in the intended

functions being compromised.

The licensee's

working knowledge of the

design

as well as their control of design

documents

may be the subjects

of FINDINGS.

'FINDINGS typically make statements

about the need for

corrective actions.

2.0

ELECTRICAL SYSTEMS

2.0. 1

EDS Description

The Browns Ferry Nuclear Station

was connected

to the transmission

system through

seven lines serving the

500

kV switchyard

and two lines

serving the -161

kV switchyard.

Power was supplied to Units

1 and

2

through several

shared

components

and systems.

During normal operation,

auxiliary loads were supplied

by the main generators

through four. USSTs,

two per unit, which in turn power six 4 kV Unit Boards

and two 4

kV

Recirculation

Pump Boards.

ESF loads of both units were supplied from

two shared

4 kV shutdown

busses.

The normal supply for Shutdown

Bus

1

was the

X winding of USST

1B via Unit Board lA.. The normal supply for

Shutdown

Bus

2 was the

X winding of USST 2B via Unit Board

2A.

The

1B

and'B transformers

were equipped with load tap changers

to regulate

voltage

on the shutdown busses.'ach

shutdown

bus supplied two 4 kV

Shutdown Boards,

designated

A,B,C, and D, from which all

4 kV and 480

VAC ESF loads were supplied.

Each of the four shutdown

boards

were

provided with emergency

standby

power from its own diesel

generator set.

The Unit 3 auxiliary power system

was similar to that described for

Units

1 and

2 with interties to the other units at several

levels in the

distribution system.

Unit 3 was served

by an additional four diesel

generators

which were relied upon for Unit 2 shutdown

under certain

circumstances.

A number of 480

VAC SDBs had

been provided to supply essential

motor

loads,

feeders to HCCs,

and to

MG sets.

480

VAC RHOV boards

2A,2B, and

2C were supplied directly from SDB whereas

RMOV boards

2D and

2E were

supplied via

HG sets

which existed to prevent propagation of a fault to

a SDB.

Transfer of power to an alternate

source

was performed manually

except that for the

HG sets,

transfer from normal to alternate

sources

was automatic, with a'manual

reset.

Additiona'l loads were carried

by

480

VAC diesel auxiliary boards

A and

B for Units

1 and 2,

and

3A and

3B

for Unit 3.

The 480

VAC systems

were ungrounded

and ground detection

equipment

was provided at each

SDB.

Unit

1 and

3

SDB were similar to

those in Unit 2.

The 480

VAC SDB provided power to two safety related

120

VAC systems

via

the

IEC and the

RPS systems.

The former was to provide two independent

class

1E sources of power for each unit to the vital IECs,

and the

latter, through

HG sets,

provided two independent

power sources for the

operation of neutron instrumentation

and solenoid valves for scram

initiation.

To support the operation of the 480

VAC auxiliary system,

three safety

related

250

VDC battery systems

were provided

on a plant basis with five

250, VDC safety related battery systems

associated

with the

4 kV and 480

VAC SDB.

Each of the eight

DG had its own 125

VDC battery system for

essential

starting

and running loads,

each battery having its own

battery charger

and instrumentation

monitoring the status of the system,

including ground fault detection

equipment.

2.0.2

EDS Review

The team reviewed the offsite-power sources

feeding the safety related

ESF busses,

to determine availability of offsite power.

The team also

reviewed the

4

kV ESF system to ensure that electrical

power of

acceptable

voltage, current,

and frequency would be available to

equipment supplied

by the

EDS.

Additionally, the

Emergency Diesel

Generators

were reviewed to assess

both their steady state

and transient

loading capabilities.

Review of the 480

VAC auxiliary system consisted of load center

switchboard

SDB 2B and

HCC switchgear

fNOV Boards

2D and 2E; due to the

interrelationship

between the boards,

the review included parts of other

, boards.

Factors

such

as available short circuit currents,

equipment

capacity,

coordination of protective equipment,

and voltages at the

loads were examined.

Compliance with GDC 17 and the single failure

criterion,

and conformance with separation

requirements

were also

factors considered

by the team.

At the

120

VAC level, only class

1E systems

were considered.

For the

DC

system only the 250 and

125

VDC class

lE subsystems

were included, with

the 48 and

24

VDC subsystems

being excluded

from the review.

In all

cases,

the factors outlined above were examined to ensure

adequacy

.of

'design.

2.1

Conclusions

The team concluded that the offsite power was flexible and reliable

and

that the

EDS was generally in compliance with the TS/FSAR/SER.

Design

documentation

including calculations

and analyses

were available

and

, retrievable.

These

documents

demonstrated

that equipment

and systems

were appropriately selected

and applied

so that the

EDS was capable of

providing adequate

power to essential

loads.

The design

was supported

by a knowledgeable

team

and

a comprehensive

set of calculations.

However,

a few calculations

contained errors or omissions,

but these

were considered

exceptions

to an otherwise

good quality calculation

program.

In addition, the team noted that

some procedures

relative to

the operation

and surveillance of the

EDS could have resulted

in

unanalyzed

or undesired

operating conditions

as noted below..

2.2

Offsite Power

2.2. 1

Degraded

Grid Voltage Protection

The, team noted the following problems in calculations

and procedures

relating to Degraded

Grid Voltage Protection.

/

2.2. 1. 1

Calculations for Bus Voltage During

LOCA Load Sequencing

Calculation

ED-Q2000-870026,

"4. 16 kV and 480

V Busload

and Voltage Drop

Calculations with Offsite Power", Revision 9, did not contain sufficient

data to determine that the relay would reset following voltage dips.

In

response,

the licensee

provided additional

computer runs which enabled

th t

t

'fyp

p

p

ti

fthm

ly. ~SA

d'

Findin

1

2.2.1.2

Procedures

for setting the

USST Load Tap Changer Selector,

Switch

Instructions in SOP 6055

and 0-GOI-3001 for setting the

USST tap changer

selector switch did not require the switch to be set to monitor the

winding supplying the shutdown

bus.

This was

an operating constraint

identified in calculation

ED-f2000-870026,

"4. 16kV and Busload

and

Voltage Drop Calculations with Offsite Power", Revision 9.

The

calculation demonstrated

that adequate

safety system operation

was only

possible

when the load tap changer selector switch was monitoring the

.

winding supplying the Shutdown Board.'owever,

SOP 6055

and 0-GOl-3001

collectively specified that the most heavily loaded winding shoul'd

be

monitored,

which could be the winding supplying non-essential

loads.

If the tap changer control

was not monitoring the winding supplying the

SDB when

a

LOCA occurs,

the tap changer

would not properly respond to

the voltage drops resulting from LOCA load. sequencing.

This could

result in actuation of the undervoltage

protection

scheme

which would

isolate the preferred (offsite) source

from the SDBs.

A walkthrough of

the control

room revealed that the selector switch for USST

1B was

actually set to monitor the winding not supplying the shutdown

bus.

In

response,

the licensee

revised the procedure to require that the

selector

switch be set to monitor the winding supplying the shutdown

bus.

This item is identified as

VIO 50-259

260 296 92-15-01.

2.2. 1.3

Surveillance Instructions for Calibration of the Degraded

Voltage Relays

The acceptance

criteria in Surveillance Instruction 3-SI-4;4.A.4.c(I),

Revision

1, did not reflect the

26

V tolerance

determined

in calculation

ED-(2211-890144,

"Setpoint

and Scaling Calculations

4 kV Bus Degraded

Voltage Relays

(ITE 27N)", Revision 4,

as follows:

Instructions

allowed the relay reset voltage to be left as high as

3987.7

V, which would permit drift above the

TS limit of 3999 V.

Instructions did not provide

a lower limit for the reset voltage.

The limit could have

been set close to the dropout value.

This

would permit convergence

of the dropout

and reset

due to setpoint

drift.

Instructions

allowed the dropout voltage to be left as low as

3911.25

V, which would permit drift below the

TS allowable limit

of 3900 V.

In response,

the licensee

revised the setpoint calculation

and

surveillance instruction to assure that the settings

would not allow

drift outside

TS allowable values.

See

A

endix A

Findin

2

2.2.1.4

Available Equipment Terminal Voltage=Under Degraded

Grid

Conditions

Calculation

ED-(2000-870027,

"460

V Class

1E Motors and Equipment Volt

Drop", Revision 3, demonstrated

that two motors did not have the minimum

required terminal voltage of 414

V (90% of 460 V) stated in section

8.4.8. 1.4 of the

FSAR.

In response,

the licensee

included the necessary

corrections to their next

FSAR submittal to allow departures

from the

90% criteria.

See

A

endix A

Findin

3

In the cases

noted

above,

the calculation, relied on equipment design

margins to justify voltage below manufacturer's

recommended

minimums

rather than removing

known conservatism

or correcting circuit

deficiencies.

In addition, the justification'id not evaluate

the

ff

f

1

d

t t

d

d

tt'g .~gg

df

A

Findin

4

The team also noted the following items relative to degraded grid

voltage calculations:

Bus voltages

used in calculation

ED-(2000-870027

used to calculate

equipment terminal voltages

were not correct in some cases..

Calculation

ED-(2211-890144 incorrectly concluded that two

Degraded

Voltage Relays would not drift in the negative direction

simultaneously.

Calculation

ED-(2211-890144

used

an incorrect value for minimum

steady state voltage.

Calculation

ED-(2211-890144 incorrectly concluded that degraded

voltage relay dropout

and reset

would always drift in the

same

direction.

The team determined that these

anomalies

did not have

a significant

adverse effect on the results of the calculations

and the licensee

corrected

them during the inspection.

See

A

endix A

Findin

4

2.3

Medium Voltage and Safety Related

480 Volt Systems

2.3. 1

Short Circuit Calculations

The team reviewed calculation ED-(2000-87-0029,."4

kV Short Circuit

Calculation", Revision 5,

and determined that equipment

was adequately

sized for existing fault duties.

Ratings for medium voltage switchgear

provided adequate

margin of 5.6% over interrupting fault duty and

2.2%

over momentary fault duty.

2.3.2

Containment Electrical Penetrations

2.3.2. 1

Continuous

Loading

The team reviewed in particular, penetrations

where the heat loadings

exceeded

the

recommended

values of IEEE 317-1983.

In the case of

penetrations

EB and

EE, test data from the Conax Corporation indicated

that

a loading of 54 watts/foot

had

been

achieved

where the measured

temperature

at the steel/concrete

interface

had not exceeded

150 degrees

F.

In the case of penetrations

EA and

EF,

a document

from the G.E.

Company indicated that

a value of 56 watts/foot could be used

as

an

upper limit in the allocation of current to the conductors.

In all

cases,

the calculated current loading was found to be less than these

limits.

For all other penetrations

the, heat loading was well below the value of

30 watts/foot

and the team concluded that all penetrations

were

adequately

designed

and that circuit currents

had

been

chosen

conservatively.

2.3.2.2

Short Circuit Loading

I

The team noted that short circuit currents

as calculated at the various

penetrations

were based

on the conservative

assumption that

a bolted

fault would occur

on the containment

side of the penetration,

of a

magnitude

based

on the maximum current available at the beginning of the

circuit under consideration,

and modified to take into account the

effect of extra

impedance of the feeder cables

from the nearest

bus to

the penetration.

The penetration

conductor insulation was rated at 90

degrees

C. continuous

and

an increase to 250 degrees

C. was allowed on

'hort

circuit of the conductor.

Values of I't used in the calculations

for the design of the penetrations

were the

same

as given in table

A5 of

standard

IEEE 317-1983,

and in no case

were these

values

exceeded.

The

team, therefore,

concluded that the penetrations

were adequate

to

withstand the thermal effects of a short circuit current.

Both calculations

considered

only the heating effect's of short circuit

and continuous currents,

but not the mechanical

strength of the

penetr ations subject to the electromagnetic

effects of short circuit

currents

in the conductors.

This subject

was discussed

with the

licensee

and details of the high energy penetrations

containing

1000

HCH

conductors

were sought.

The licensee

produced

a notarized partial test

report dated April 23,

1970, indicating that short circuit tests of the

P.S.L. penetrations

(Type AA-AF) had

been

conducted

up to a peak value

of 35 kA, compared with a maximum available current of 3500 amperes

symmetrical.

The team concluded that the penetrations

would not incur

mechanical

damage

from the effects of short circuit currents flowing in

the penetration

conductors.

2.3.2.3

The team reviewed the suitability of circuit breakers

and fuses. in

protecting the conductors of the electrical penetrations

against

the

effects of sustained

overloads or of short circuits;

and found that all

conductors

wer'e adequately

protected

from damaging effects

by the

primary protective device.

2.3.3

Hedium Voltage Protection

and Coordination

The team reviewed calculation

ED-(2000-870548,

"Cable

and

Bus

Protection/Breaker

Coordination

For

4 kV Switchgear

and 480

V Load

Centers",, Revision

10, which determined

medium voltage relay settings.

The calculation demonstrated

appropriate

equipment protection

and

coordination of protective devices.

2.3.4

480

VAC

2.3.4. 1

Short Circuit Analysis

The short circuit currents potentially available in the Unit 2 480

V

system

are derived in calculation

ED-f2000-870030 Revision 4, which

takes

a conservative

approach

using the

MVA method,

and neglecting all

cable

impedances

that would result in lower values of current.

In

addition, the 4160/480 volt transformers

supplying the various

switchgear

boards

were

assumed to supply all induction motor loads of a

magnitude equivalent to the

FA rating of the transformer,

and with short

circuit reactance

values of 0.25 p.u..

The reactance

of a

transformer'hat

was

assumed

to control the short circuit current from the source

was taken

as the minimum of the set of values

determined for that class

of -transformer.

The maximum three

phase

short circuit current,

calculated

at the bus supplied

from a

1

MVA transformer

was 21.9

kA

symmetrical

compared with a circuit breaker interrupting capacity of 22

kA.

The team considered

the basis

and accuracy of the calculation to be

satisfactory.

2.3.4.2

Protective

Device Coordination

Calculation

ED-(2000-870548

Revision 10,

examined the coordination of

the protective devices

and feeder cables to and from the

4 kV switchgear

and the 480

V SDB load centers.

For the motor loads,

the calculation

used.

as

a design basis,

the relationship that the long term setting of

the molded case circuit breakers

had to be greater

than or equal to the

full load cur rent of the motor multiplied by factors

1.28

and 1.39 for

motor service factors of 1.0

and

1. 15 respectively.

The team noted that.

the motor powering the Control

Bay Water Chiller B did not meet this

criterion,

and that operation at the minimum bus voltage of 445

V would

produce

a motor load current that would lie in the tripping region of

the circuit breaker.,

See

A

endix A Findin

5

All other motors, with the exception of three non-lE cases

were

satisfactory

and the long term pickup settings of the circuit breakers

were adequate.

The team examined the coordination curves for all loads

and considered

that coordination

between the board

2B circuit breakers,

the supply feed circuit breakers

from the

4 kV shutdown boards,

and the

outgoing feede'r cables,

were satisfactory.

The team reviewed calculation

ED-(2000-870549

Revision

11,

and in

particular,

the protective devices for the 480

V RMOV boards

2B and

2D,

the Control

Bay Vent Board

B, the -Diesel Auxiliary Board

B, and the

Standby

Gas Treatment

board.

In general,

the load cables

were protected

against

the effects of overcurrents

by the associated circuit breakers,

but in a few cases,

where conformance to the normally accepted

upper

limit on conductor temperature

could not be achieved,

the

licensee'tated

that the conductor insulation would be below the auto-ignition

temperature

of the material.

Extensive

use of "Flamemastic",

a fire

retarding material,

would ensure that fire, if it occurred,

would not

propagate

to conductors of other .loads.

The team accepted this position.

Coordination

between

the circuit breaker

on load center

SDB 2B supplying

circuit breakers

on 480

V RMOV Board 2B; and between

SDB 3A and circuit

breakers

on the Control

Bay Vent Board B; and between

MG sets

2DN,

2DA

and circuit breakers

on

RMOV Board 2D; was also found to be

satisfactory.

In general,

motor overload heater tripping curves

and

motor starting curves

were not shown

on the coordination curves.

However, the team was able to ascertain that overload heate'rs

had

been

selected correctly and that motor starting currents

would not trip the

protective circuit breakers.

2.3.4.3

Load Voltages

The team reviewed calculation

ED-(2000-870027

Revision 6, which examined

the voltages at the 460

V class

1E motors

and other loads

such

as the

Standby

Gas Treatment

and

DG heaters

and battery chargers,

under

degraded grid voltage conditions.

For the worst case voltages at the

480

V busses,

the calculation identified two Unit 3 loads

(Control

Room

Air Handling Unit A and

El 593 Air Handling unit 3A), supplied

from

Control

Bay Vent Board A, which just failed to meet the running voltage

criterion of 0.9 p.u.

In discussions

with the team,

the licensee

stated

that the Board

Room Emergency

Supply

Fan

3B load

had

been mistakenly

included in the calculation

and that the Unit 3 Chilled Water

Pump A,

which also failed the criterion,

was not required for Unit 2 operation.

The team examined,

in particular,

the voltages available at the

SDB

battery chargers

SB-A,B,C,D,

and

3EB for which the input voltages

were

below the manufacturer's

specified figure of 480

V less 7.5/, or 444 V.

The licensee

had performed

a separate

test

on one of the chargers,

indicating that

an output of 266

VDC at

12 amperes

had

been

observed for

an input voltage of 391 V, with a ripple content of less

than the 1.3

volts quoted in the equipment specification.

The minimum bus voltage at

the 480

V RMOV board

1B which supplies this charger,

was calculated

at

438

V giving a charger voltage of 419

VAC, at the

DC output conditions

referred to above.

The team concluded that since =the float voltage

was

260

VDC and the continuous loading on this battery

was

11 amperes,

the

above

low voltage condition would be satisfactory,

though there will

probably

be

no capability of equalizing the battery under this condition

-of degraded

voltage.

However, since this low voltage condition was post

accident,

the team accepted this uncertainty.

All other loads were

considered

acc'eptable

by the team.

2.3.4.4

Ground Fault Detection

System

The 480

V auxiliary system

was ungrounded,

supplied through

1000

KVA

4160/480

V delta-delta

connected

transformers.

Ground fault detection

equipment

was provided

on each

480

V SDB board in the form of three

single

phase

480/120

V transformers

connected

in a wye-wye configuration

with a grounded

secondary

neutral

and supplying loads of one

incandescent

lamp per phase.

A test switch used for connecting the

primary and secondary neutrals,

and protection fuses

per phase

complete

the system.

The test

and indication equipment

were mounted

on each

480

volt SDB board

and

a ground test

was performed

once per shift.

The team raised the question of continuity of monitoring for ground

'faults, with the particular consequence

of maintenance

induced

ground

faults at isolated

loads remaining undetectable

with the existing design

of the ground fault detection-system.

The licensee

stated that the

bridge

and megger testing

was the last activity performed after

completion of maintenance

work, and that any ground faults occurring at

that time would be discovered.

The team reviewed maintenance

instructions

ECI-0-000-HOV001

and ECI-0-000-NOTOOl and considered

the

present

design to be acceptable.

2.3.5

120/208

VAC

2.3.5. 1

Short Circuit Analysis

.

The team reviewed calculation

ED-f2000-870031

Revision

3 in which the

values of short circuit current for the

I&C and the

RPS systems for Unit

2 had

been determined.

The calculation

used

a conservative

approach,

ignoring impedances,

and in accordance

with the standard

IEEE 141-1986,

used the three phase'olted

fault approach for the grounded neutral

system.

For Unit 1,2 and

3

I&C busses,

the magnitude of the short circuit

current

was found to be 3390 amperes

under normal operating conditions

with the regulating transformer in circuit, and 6980 amperes

with this

transformer

bypassed.

All circuit breakers

in this system

had

an

interrupting rating of 10 kA and the busses

had a.withstand capability

of 25 kA.

For the

RPS system,

the largest short circuit current

was found to be

6670 amperes

when the alternate

feed from the 480/120

VAC regulating

transformer

was used.

All circuit breakers

in this system

had

an

interrupting rating of 10

kA and the busses

had

a withstand capability

of 25 kA.

The team concluded that there were

no problems with the short circuit

ratings of protective equipment in .these

systems.

2.3.5.2

Protective

Device Coordination

Calculation

ED-92000-880086,

Revision 7, examined the coordination

between various protective devices

and cable withstand capabilities for

the

120

VAC I&C and

RPS systems.

Protection of these class

1E circuits

which are required for normal-operation "and

.a safe -shutdown of Unit 2,

had

been considered

in this calculation, together with non-required

loads

powered from 1E sources.

The team ascertained

that all non-class

1E loads were protected

by class

lE circuit breakers.

The team examined the circuit from the 480

V SDB 2B to the 480-120/208

V

3 phase

75 KVA transformer,

hence to the 208-208/120

V 3 phase

50

KVA

regulating transformer

and to the

I&C bus

B of battery board 2, panel

8,

as being typical.

Feeders

to circuit breaker

board 9-9 cabinet

3 of

10

Unit 2; to the alternate

input to circuit, breaker

board 9-9 cabinet

3 of

Unit 3;

and to the non-class

lE battery chargers for the unit 24

VDC

battery system,

completed the circuit.

Adequate coordination existed

between all circuit breakers

in these circuits,

and cable

and

transformer'sizes

had

been

chosen

such that there would be no damage to

these

components prior to clearance

of a fault by the appropriate

circuit breaker.

However, in the case of the

RPS system,

the calculation

showed that

coordination

was not achieved

between the

MG set output generator

circuit breaker

and particular load circuit breakers

mounted in the

RPS

bus panel at the battery board.

The calculation offered

an acceptable

solution but stated that this would not 'be implemented prior to the

restart of Unit 2.

The licensee

stated that the change

had not been

installed,

and after further discussions,

the team concluded that this

would not present

a problem in this particular case.

The

MG set itself

was

a non-class

lE component

and suppli'ed

a number of solenoid valves

for scram initiation, together with neutron instrumentation for powe'r

measurements.

Channels

A and

B were provided, with a loss of one

channel

leading to a half scram condition which initiated implementation

of operating

procedure

2-AOI-99-1.

A loss of AC supply to either or

both sets of loads

on one channel

produced the

same effect,

and the'team

concl'uded that the absence

of coordination

was

no worse than the loss of

the non-class

lE

MG set.

2.3.5.3

Load Voltages

'The team reviewed calculation

ED-(2000-870028,

Revision 7, which

determine

the worst case voltage distribution on class

IE systems,

I&C

buses,

and the

RPS, during operation

and shutdown of the Unit 2 reactor.

Some

common loads

on the

IKC buses for Units

1 and

3 were required for

Unit 2 and

had

been included.

The team checked

the voltages at the

RPS

bus

2A; at the panels 9-15 and

25-5A buses;

at the scram pilot valves;

and at the scram discharge

volume drain

and vent valve, which had

been derived using

a computer

program

VOLTDROP/VD21.

The calculation took a conservative

approach

by

assuming

conductor temperatures

of 60 degrees

C. for current loadings

up

to 8 amperes

and

90. degrees

C. for power conductors;

by taking the

longest conductor lengths

and

maximum current draw;

and with 25/ of

deenergized

loads considered

to be energized.

The maximum load occurred

at bus

2A and was calculated

as ll KVA.

The minimum voltage

was

determined

as 112.5

V at the scram valve solenoids with 0.98 p.u. at the

generator,

and this compares

favorably with a requirement of 102

V

minimum for these valves.

The team found that all loads in the

RPS

system were adequately

supplied with voltages at the loads higher than

the minimum required.

2.4

Emergency Diesel

Generators

2.4. 1

Static Loading Analysis

The team reviewed calculation

ED-92000-870071,

Revision 8, which

determined

the loading

on the diesel

generators

during the shutdo'wn of

Unit 2 with a loss of offsite power,

and with or without a concurrent

LOCA.

The team noted that Diesel Generator

A would be loaded in excess

of its continuous rating during the two hour period following a

LOOP/LOCA (2781

kW loading vs.

2600

kW rated).

This loading was below

its

2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> rating of 2860

kW but the calculation did not analyze loading

after

2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

The licensee

stated that it was highly likely that the

loading would be reduced

below the continuous rating within the two hour

limit and that operating

procedures

provided for paralleling additional

diesel

generator

sets to the shutdown

boards during

an emergency.

In

addition, the diesel

generators

have

a short time rating of 2900

kW for

200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br />.

Based

on current plant operating configurations

and the

diversity of onsite

and offsite power sources,

these justifications were

deemed

acceptable.

2.4.2

Dynamic Loading Analysis

A formal dynamic loading analysis

had not been performed.

In lieu of

calculations,

the licensee

had performed extensive transient

load

testing,

including regulator/exciter

and governor calibration.

The

results of these tests

were reported in TVA Memorandum

B22 '89 00117

010,

Browns Ferry Nuclear Plant

(BFN) - Diesel

Generator

Evaluation

Report,

dated January

17,

1989.

The testing adequately

demonstrated

the

ability of DG sets to start

and accelerate

the required

sequenced

loads

following a

LOOP/LOCA.

The team note'd that

a severe voltage dip

(46% of

nominal)

occurred during

RHR Pump motor starting.

This was

demonstrated

to be within 'the capabilities of the diesel

generators

by

the testing,

and was determined

not to have adverse effects

on connected

480

V loads

by calculation

ED-(2082-880557,

"Undervoltage Analysis of

BFN Electrical Auxiliary System During Diesel

Generator

Sequencing",

Revision

1.

However, the team noted that the existing analyses

and testing only

justified starting the

RHR Pump upon closing of the diesel

generator

breaker with n'o other

4 kV loads connected

and

480

V loads in an

initially deenergized

state.

A review of operating

procedures

revealed

that there

was

no prohibition against restarting the

RHR Pump while

other loads were connected

following load sequencing.

In response,

the

licensee

stated that

a revision would be made to the applicable

p

tungi

t

ti

t

dd **th

. ~Adi

A

~Fi di

6

2.4.3

DG Protection

and Controls

The team noted that the alarm response

procedure for a diesel

generator

ground fault annunciation,

O-XA-55-23A, Revision

11,

Panel 9-23,

window

10, did not provide adequate

guidance

as to the possible

causes

of the

12

alarm or corrective actions.

In response,

-the licensee

revised the

procedure to provide appropriate

guidance.

See

A

endix A

Findin

6

2.5

DC Systems

2.5. 1

Short Circuit Analysis

2.5.1.1

250

VDC

The team reviewed calculation

ED-(2000-870045,

Revision 5, which covered

all battery systems.

In general,

the calculations

were conservative

in

assuming

cable temperatures

of 25 degrees

C., circuit breakers

and fuses

and

DC busses

having zero resistance;

and that all battery chargers

and

continuous rated motors would contribute to the fault current.

The team

concu} red with the assumption that the contribution from the

50

HP

DC

motors driving the

120

VAC HG sets

and the Turbine Emergency

Bearing Oil

Pumps would be zero,

because

of the introduction of blocking diodes

preventing

a reverse flow of power into a fault on the

DC system.

In

both cases,

the loads were not considered

to be extreme

and excessive

voltage rise at the motor would not be

a problem.

The calculation

was

based

on

a battery terminal voltage of 2

V per cell

and

an electrolyte temperature of 77 degrees

F.

The team concurred with

the first of these

assumptions,

but the question

was raised of increased

short circuit current at

a higher electrolyte temperature

of 96 degrees

F., which had

been recorded during

a daily check.

The licensee

stated

that

a test

had been

conducted

by TVA in conjunction with other industry

groups.

The results of which indicated that

a rise in electrolyte

temperature

would increase

the capacity of the battery but not the

magnitude of the short circuit current,

and that pre-fault voltage

considerations

would also not affect the magnitude.

A submittal

had

been

made to the

IEEE committee responsible for standard

IEEE 946 to

have these findings incorporated into the next revision.

The calculation'also

considered

the pre-fault voltages at the

DC motors

to be 240

VDC, whereas

the team considered that this voltage would be

closer to the equalizing voltage of the battery of 279 V.

The licensee

agreed

on this point and presented

the team with a revised calculation

which incorporated

the

new motor voltages.

There were no significant

change to the 'conclusions

arrived in the calculation

and the worst case

value of short circuit current remained

below the circuit breaker

and

bus rating of 20 kA.

The short circuit currents

were determined for each safety related

bus

when supplied from appropriate

normal

and alternate

sources,

and

when

supplying the required loads during

a shutdown of Unit 2 and for

maintaining Units

1 and

3 in a cold shutdown (de-fuelled) condition.

A

maximum short circuit current of 18.3

kA was obtained,

at main board

1

as expected,

with smaller currents of 16.3

kA at main boards

2 and 3.

The busways

and associated

circuit breakers

had withstand or

interrupting ratings of 20 kA, and fuses in the system

had interrupting

ratings of 10,

20, or 100 kA.

The team confirmed that all equipment

13

could adequately, withstand or interrupt the short circuit currents

available at each location,

using inputs

as predicated

in the

'alculation.

The team was concerned,

however, that the calculated short circuit

current from'he large 300 ampere battery chargers

connected to the main

battery systems,

had

been determined at the current limit settings of

llOX of full load capacity i.e.

330 amperes.

Since this type of charger

used silicon controlled rectifiers for rectification and control; it had

been postulated that the short circuit output current of the charger

could be up to ten times its full load rating for a period of 8

milliseconds.

The team was informed that this issue

had also

been

presented

to the

IEEE for clarification.

2.5.1.2

125

VDC

Calculation

ED-(2000-870048,

Revision 3,

used the conservative

assumptions

of conductor temperatures

being at

25 degrees

F.

and the

resistance

of DC busses,

circuit breakers

and fuses

being zero

ohms.

All sources of fault current from the batteries,

and battery chargers

operating at

a current limit setting of 150/ of rated output,

were

included.

The maximum short circuit current

was found to be,

as

expected,

at the bus of the largest battery system

(3D) and

had

a value

of 2680 amperes;

well below the withstand rating of the bus of 10 kA,

and the interrupting capacity of associated

circuit breakers

and fuses

of at least

5 kA.

The team considered that the equipment

connected

to

these battery systems

were adequate

to handle

a short circuit on the

system.

The team again raised the issue of short circuit currents

related to electrolyte temperature

(maximum recorded electrolyte

temperature

of 95 degrees

F.),

and considered

that the disposition of

this item will be as for the 250

VDC battery.

2.5.2

Batteries

and Battery Chargers

2.5.2.1

250

VDC

The team checked calculation

ED-(2000-870041,

Revision 8, in which the

sizing of the main plant class

1E batteries

were developed.

The plant

conditions were postulated to be Unit 2 in normal operation with Units

1

and

3 in a col'd shutdown condition (de-fuelled);

and when Unit 2 was

subjected

to a loss of offsite power followed by a

LOCA event.

The

computer

program

BATCALC, an in-house

program employing Lotus 123,

was

used to size both the batteries

and battery chargers.

The team noted

that the calculation modelled motor starting loads

as constant

resistance

loads

and motor running loads

as constant

power loads; .that

motor operated

valves were modelled

as

an inrush current for 2 seconds

followed by

a running current for one minute;

and that

pump motors

reached their operating

speed

in 5 seconds.

The team considered

the

assumptions

to be acceptable.

14

The calculation

used the method of sizing, batteries

described

in IEEE 485-1983,

and included

a temperature

correction factor of 1.1

(60

degrees

F.),

and

an aging factor of 1.25.

The maximum demand

on battery

1 system

was with battery

3 out of service

and

on battery

3 system with

battery

2 out of service.

The selection of 16 positive plates/cell for

battery

1 and

14 positive plates/cell for batteries

2 and

3 gave

'apacity

margins of 48,36,

and 23K respectively for batteries

1,2,

and

3;

The minimum voltage of the batteries

was found to be 214.8

VDC- for

battery

3 with battery

2 out of service

compared with a committed value

of 210

VDC given in the

FSAR.

For the battery chargers,

the method given in IEEE 946-1985

was used

resulting in a requirement for a 300 amperes'harger

with a battery

recharging time of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />

and

no margin in the worst case of battery

3

with battery

2 out of service.

The team concurred with these

findings.'he

sizing of the 250

VDC control

power batteries

SB-A,B,C,D,

and

3EB

were handled in calculation

ED-Q2000-870042,

Revision 4, along with the

sizing of the battery chargers.

Again the team concurred

with the

methods

used in the calculation,

and the findings of a capacity margin

of 18/ for battery

SB-3EB and

155 for the remainder,

together with a

margin of 71% for the sizing of the

20 amperes

battery charger.

The

minimum voltage of the batteries

was found to be 214.8

VDC for battery

SB-A compared with a committed value of 210

VDC given in the

FSAR.

2.5.2.2

125

VDC

The sizing of the

DG class

lE batteries

was handled in calculation

ED-

Q2000-870046,

Revision 4, which examined

two duty cycles of.30 minutes

each,

one with two attempted starts of the diesel

generator

followed by

a successful

start at the beginning of the cycle,

and the other in which

the attempted

plus successful

starts fall at the end of the duty cycle.

In each

case,

the sta'rting of the

DG was enveloped

by a

1 minute supply

of starting current with a small continuous current for the remainder of

the period.

The number of attempted starts

was considered

by the team

to be conservative

when related to the

TS requirements for DG starts.

Also conservative,

was the assumption of a minimum electrolyte

temperature

of 40 degrees

F. since

a check of historical data over the

past

5 years

showed

a minimum measured electrolyte temperature

of 60

degrees

F.

The calculation

used the method of sizing batteries

described

in IEEE 485-1983,

including temperature

correction factors of

1.3

(40 degrees

F.),

and

an aging factor of 1.25.

The choice of 4

positive plates/cell for the

100 A-H battery,

gave

a margin of 4.4X over

the required capacity after the correction factors

had been included.

In a similar manner,

the choice of 3 positive plates/cell for the

240 A- .

H battery gave

a margin of 871. over the required capacity.

The team

found the calculation to be accurate

and the battery sizing acceptable.

The minimum voltages for the

100 and

240 A-H batteries

were calculated

to be 105.7

V and 110;8

VDC respectively at

an electrolyte temperature

of 40 degrees

F.

and for old batteries,

which compares

favorably.-with an

FSAR commitment of 105 VDC.

15

For the battery chargers,

the method given in IEEE 946-1985

had

been

used -in the calculation to size the battery chargers,

using

a

5 amperes

continuous

load and

a time to re-charge of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

Based

on the fact

that the batteries

were not substantially discharged

during the duty

cycl'e,'

charger size of 20 amperes

was considered

by the team to be

acceptable.

2.5.3

Protective

Device Coordination

2.5.3.1

250

VDC

The team checked calculation

ED-(2000-870550,

Revision 7, which examined

the coordination of the protective circuit breakers

and fuses,

and the

feeder

cable sizes.

Coordination

between the various

bus circuit

breakers

and fuses

were found to be acceptable,

as were the feeder cable

'sizes,

with the exception of a few conductors,

sized

14 to 10

AWG, for

which the cable

damage

curves intersected

the circuit breaker operation

curves.

On discussing this point with the licensee,

the team

was told

that these

cables

were acceptable

under the

10 CFR 50 Appendix

R

requirements,

which allowed greater conductor temperatures

on short

circuit than the

150 and

250 degrees

C. considered

as industry accepted

figures.

The'team

found that the cables

had

been

sprayed with

"Flamemastic",

a thermoplastic resin, containing flame retarding

chemicals

and inorganic incombustible fibers,

and that fire damage, if

created,

would be confined to

a particular cable.

On this basis,

the

team accepted

the calculation.

2.5.3.2

-

125

VDC

The team reviewed calculation

ED-(2000-880085,

Revision 3, which

examined the coordination of the protective devices in the

DG battery

systems

A-D and 3A-3D.

Fuses

were used as-protective

devices at the

higher current levels.

The team found that coordination

had

been

achieved

between the various circuit breakers

and fuses

and that

conductors

supplying the various loads were protected

from possible

overcurrent situations.

I

2.5.4

Load Voltages

2.5.4.1

250

VDC

The team reviewed the minimum and maximum voltages at all the loads

on

the

250

VDC systems,.-and

in particular at the 250 -VDC RMOV.boards

2A,2B,

and

2C; the

4 kV SDB A,B,C,

and

D; the 480

V SDB lA,1B,2A,

and

2B; the

4

kV cooling tower switchgear

boards A,B,C, and D; and the

4 kV RPT boards

2-I and 2-II.

The determination of these

load voltages

was given in

calculation

ED-92000-870054,

Revision 2, which utilized results

from

auxiliary calculations

ED-(2000-870043,

Revision 6,

and ED-(2000-870044,

Revision 9.

Assumptions

adopted for the calculation were that conductor

temperatures

would be at 60 degrees C.'or the control circuits;

that'he

minimum voltage at the

250

VDC

RMOV boards

2A,2B,

and

2C would be at

16

210

V (the minimum FSAR value);

and that maximum voltages of 279.6

V

(the battery equalizing voltage)

would occur at all points in the

system.

All assumptions

were found acceptable..

All loads at the

various switchboards

had guaranteed

operating voltages

below the

calculated figures with the exceptions of solenoids fitted to the

condensate

drain pot valve LSV-73-8 and the

RCIC Turbine Speed Control.

Calculated voltages of 205 and

208

VDC respectively

were compared with

requirements

of 225 and

220

VDC.

For the drain valve, the licensee

stated that this only operated

in a standby

mode

and that any condensate

would be adequately

removed

by the turbine exhaust drain line,

so that

valve actuation

would not be required during HPCI.

For the Turbine

Speed Control, the team found that

a memorandum

from the Moodward

Governor

Company advised that

a minimum voltage of 220

VDC was required

to prevent potential instability, overspeed

or shutdown of the turbine.

The licensee

advised that the

RCIC Turbine Speed

Control

was not

required for accident conditions but was required to meet

SBO

conditions.

The team examined the relevant portion of calculation

ED-

f0999-890059,

Revision 2,

and concluded that sufficient voltage

was

available at the

RMOV board

2B to activate this control unit for the

four hour

SBO condition.

In the case of maximum voltages existing at the loads during battery

float or equalizing

charg'e periods,

the calculation

showed that

auxiliary relays,

contactor coils,

and valve solenoids

had

a specified

maximum of 275

VDC and circuit breaker anti-pumping relays

had

a

specified

maximum of 260

VDC when energized

continuously.

Because of

the conservatism

adopted in the calculation,

the team accepted

the

licensee's

position that overvoltages

would r aise the coil temperatures

slightly but that there would not be

a catastrophic failure of these

components.

2.5.4.2

=

125

VDC

Calculation

ED-(2000-870047,

Revision 7, determined

the maximum and

minimum voltages at the loads

on the

125

VDC battery systems for the

DG.

As part of the design basis for the calculation,

the minimum voltage was

expected to occur during starting'f the diesel

generators

under plant

accident conditions with the battery chargers

inoperative,

and the

maximum voltage

was expected to occur

when only the continuous

load was

being supplied

and the battery charger

was delivering the equalizing

voltage of the battery.

The calculation considered all eight battery

systems,

and

used conservative

assumptions

such

as conductor

temperatures

of 60 degrees

C. for intermittent loads

,

and

90 degrees

C.

for continuous

loads,

when determining

minimum load voltages;

and

25

degrees

C. when determining

maximum load voltages.

The calculation also

considered

a minimum battery voltage of 105

VDC in calculating

minimum

load voltages in accordance

with the commitments

made in the

FSAR.

The team checked

the results of the calculation

and noted the

conclusions

in the calculation that the air start solenoid valves

and

the exciter breaker auxiliary relays for the

DG A,B,C, and

D did not

meet the criteria.

On further review, the team agreed with the licensee

17

that the voltage at the auxiliary relays would be greater

than the

minimum required voltage at the time the breaker closed.

For the air

start solenoid valves,

the calculation

had

assumed

a status

inconsistent

with the operating conditions,

and

a reevaluation of'the voltage drop

calculation 'for these

elements,

showed that the voltage at the solenoids

would be greater

than the minimum 'specified

by the manufacturer. 'he

team accepted

that the minimum voltages at all loads were adequate.

2.5.4.3

DC Systems

Ground Fault Protection

The system at the

BFN uses

inverse logic, where

an operator conducting

a

daily check, interprets

a zero reading

as

a "no ground fault "

situation,

whereas

a zero reading

may also

be the consequence

of a

faulty meter or open circuited connections.

Checking

and calibration of

the meter was at three year intervals,

and results

from BFN indicated

that the incidence of faulty meters

was approximately

28%.

The )earn concluded that this system would not effectively monitor

grounds

having higher impedances.

The licensee

stated that

a weekly

test

may be initiated after further evaluation is conducted.

~See-

A

endix A Findin

7

3.0

MECHANICAL SYSTEMS

The team reviewed

and evaluated

the adequacy of mechanical

systems

required to support the

EDS during normal operations

and postulated

accidents.

These

systems

included the

DG and

DG support

systems,

e.g.,

diesel

fuel oil storage

and transfer, starting air, cooling water,

lubricating oil, and the air intake

and exhaust

systems.

Also reviewed

were the nuclear service water system interface with the

DGs

and the

HVAC for spaces

containing safety related electrical

equipment.

The

basis for the mechanical

load values

used in the

DG loading calculations

was evaluated.

Documents

reviewed included applicable portions of the

FSAR, engineering

and vendor

documentation,

operating

and maintenance

procedures,

mechanical

system calculations

and drawings,

pump performance

curves,

equipment

performance

data sheets,

and

EDS related modification-

packages.

3.1

Conclusions

The team concluded that the design of mechanical

systems

supporting the

EDS was adequate.

.However,

the=team

noted that the air start

system

'elied

on

a single check valve as

a pressure

boundary for the safety

related portion.

The Licensee

had independently identified the weakness-

and initiated

a revision to Surveillance Instruction (O-SI-4.9.A.l.a) to

conduct leak checks.

In the area of seismic qualification, the air receivers

in the

DG air

start

system were not formally qualified to sustain

seismic events.

Additionally, even

though the

EECW Cooling System

was adequately

18

protected

from external

flooding events,

the dewatering

sump

pump and

the grating at the top of the concrete

were not qualified.

Also, the

DG

Room Battery

Fume

Hood was not seismically qualified.

However, all

DG

support

systems

were under

NRC Unresolved Safety Issues

A-46 and will be

reviewed accordingly.

Several

undocumented

assumptions,

inconsistencies

and reference

errors

were noted in the calculation that determined

hydrogen concentration

in

Battery

Rooms I & 2.

The licensee

revised the calculation;

a review of

the, preliminary calculation indicated that the ventilation was adequate.

3.2

Diesel

Loading

The team noted that the mechanical

loads,

based

on the mechanical

load

study,

were within the

DG ratings,

except for DG A.

The team observed

that even though diesel

A was below the

2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> rating

(2857 KW), the

figure was nevertheless

above the engine continuous rating

(2600 KW).

The Licensee

explained that these diesels

were also rated

2960

KW for

200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br /> per year

and according to operating

procedures,

the Unit 3

diesels,

which were loaded to approximately

50 / of their full capacity

were to be aligned, within ten minutes from the onset of the accident

with the corresponding

Unit 2 diesels,

effectively. absorbing

any

overload.

3.3

Diesel Air Start System

The

DG Air Start System

was credited with supplying enough air for one

engine start attempt per pair of air motors

on each side of the engine.

If the system failed to start the engine,

the air system would

automatically

be disabled,

both electrically and mechanically

and the

Diesel

Generator

becomes

unavailable.

The Licensee

could not locate the air receivers'izing

calculation,

however,

the licensee

made available

a baseline test requirements

document

BFN-BTRD-002, Revision

2 for the Diesel Starting Air System

and

an Air Start System Test Report

2-BFN-RTP-082 describing five

consecutive

diesel starting tests

aimed at proving the system

reliability.

Beginning at

a pressure

below the minimum recharging

set

point, the first three tests

were conducted with closed injectors to

prevent the engine from starting but allowing it to reach the required

starting

speed

(cranking only).

The last two tests

were conducted

allowing the system to actually start the engine.

The team accepted

this test

as sufficient evidence of size

adequacy for the air receivers.

The team questioned

the system capability to maintain its minimum

required pressure

since it relied on

a single check valve as pressure

boundary of the safety related portion.

The Licensee

had independently

identified the weakness

and initiated

a revision

by means of a Site

Standard

Practice

SSP-2.3

procedure to add steps to their Diesel

Generator

Monthly Operability Test Surveillance Instruction (0-SI-

4.9.A. l.a).

When 'in place,

the procedure will permit inspection of the

Diesel Air Start Compressor

discharge

check valves for air leaks.

19

Currently, the licensee

normally maintains the low pressure

set point at

a level

much higher than the actual

minimum allowable air start pressure

and monitors compressor

cycling:

an increased

operating

frequency would

indicate

a leak in the system

and.maintenance

action will be taken

as

soon

as reported.

The team regarded

the present practice in concurrence

with the

new steps

in the Surveillance Instruction

as adequate

protection against

check valve failures.

In the area of seismic qualification, the team noted that the air

receivers

in the DG,air start system did not appear to have adequate

seismic supports.

The team expressed

concern regarding this weakness

.

and questioned

the inconsistency

between the proper seismic

qualification of the piping on the one hand

and the lack of

qualification of the air receiver supports

on the other.

The licensee

responded

that all

DG support

systems

came under

USNRC NUREG-1030

regarding the seismic qualification of Equipment in operating nuclear

power plants

(Unresolved Safety Issue A-46), and

NUREG-1211,

"Regulatory

Analysis for Resolution of A-46" as well

as Generic Letter 87-02.

The licensee

stated that air receiver supports will be adequately

assessed

and possibly modified as

soon

as the

USNRC qualification

procedure or guidelines

are finalized and issued.

In conclusion the team found the measures

taken

by the licensee,

such

as,

set points with safety margins,

good maintenance

procedures,

and

'urveillance

and tests

conducted

were satisfactory in guaranteeing

an

adequate

air start

system performance.

3.4

Jacket

Cooling System

The team questioned

the simplified procedure

used to hand calculate the

jacket water outlet temperature

in calculation

BWP H2-NCR BWP-8213-3.

The average

temperature

across

the heat

exchanger

and therefore

the

overall transfer coefficient

(U) was not iterated

and sufficiently

,

converged.

The temperature

was critical and needed to be more precisely

calculated.

The Licensee

agreed

the calculation

was approximate

and

submitted another

more recent

computerized calculation HD-(2067-88021,

prepared

to map

EECW flow rates

versus

number of tubes

plugged at

various jacket water temperatures.

This calculation indicated that the

overall heat transfer coefficient U(T) was adequately iterated

and

temperatures

properly converged.

3.5

Emergency

Equipment Cooling Mater System

The team reviewed the design

and layout of the

EECM system

and the

RHRSW

pumps which provide cooling water to the Diesel Jacket

Cooling system.

Twelve

RHRSW pumps support various station cooling water systems,

four

of these

pumps

powered

by safety boards

are dedicated to .feeding two

redundant

EECM headers,

the North and South Headers,

which in turn feed

the

DG jacket cooling heat exchangers.

20

The team concluded that the

EECW Cooling System

was adequately

protected

from external

flooding events.

The only apparent

weakness

was again in

the area of seismic protection.

Two items in particular were noted,

namely the dewatering

sump

pump and the grating at the top of the

concrete.

The licensee reiterated,

as for other seismic issues,

that

the state of seismic qualification of these

items fell within the'cope

addressed

by Unresolved Safety Issues

A 46.

Consistent with the intent

of the A 46 document,

the existing safety equipment

was currently

presumed to have sufficient margin of seismic capability.

In addition,

the licensee

maintained that based

on TVA's own engineering

experience,

the equipment

was basically the

same

as

had

been qualified in subsequent

TVA plants.

The team accepted

the analysis

as adequate for the

immediate term.

3.6

Diesel Oil System

After reviewing the

TS requirements,

the diesel

consumption tests,

the

fuel oil sampling procedure,

the 7-Day storage

tank sizing calculation,

the scaling

and set point document,

the team identified several

inconsistencies

in the diesel

fuel oil consumption.

On page

2 of

calculation HD-(2018-870164,

the design

consumption rate

was

assumed

to

be

213 Gal/Hr with no reference

to specific gravity.

On page

10 it

became

206 Gal/hr and

on page

20 A, 210 gal/hr was mentioned.

In

another

document,

the Incident Investigation

and Root Cause Analysis,

II-B-91-059 concerning

DG oil consumption,

the measured

consumption rate

of Unit 3 Diesels,

3C and

3D were reported

as being

as high as

235

gal/hr and

210 gal/hr respectively,

at full load.

However,

since the

total electrical

accident

loads for Unit-3 diesels

were approximately

50% of their rating, the Unit 3 Diesels would experience

a lower than

full load consumption.

The team determined that the fuel oil available in the 7-day storage

tanks with the present refilling procedure

was sufficient to=warrant

7

days of continuous operation

under accident condition in Unit 2.

3.7

Heating Ventilating and Air Conditioning

3.7.1

Diesel

Generator

Room Ventilation

Reviewing the Diesel

Generator

Room ventilation requirements,

the team

noted that calculation MD-003-870558,

as were other selective

HVAC

calculations of safety related

rooms,

was

based

on

a maximum design

basis

ambient temperature

of 95 degree

F instead of 97 degree

F as

required

by the

FSAR.

Other calculations

were left with the 97

F

temperature

assumption.

The licensee

explained that in 1989,

a licensee

exception request

and approval

form was issued to revise design criteria-

BFN-50-715 Table l. 1-1 allowing the use of 95 degrees

F dry bulb and

75

degree

wet bulb temperatures

in the sizing calculations of HVAC

equipment required for unit 2 restart.

These temperatures

were

based

on

chapter

24 of the

ASHRAE Handbook.

The team reviewed the record of

temperatures

at the site in the past two years

and noticed that

temperatures

above

95 degree

F occurred

13 times in the period 1974-87.

21

The highest concentration

resulted in the year

1980 with 7 occurrence

at

97 degrees

F and

1 occurrence

at

100 F.

The licensee

adequately justified their position by stating that

abnormal

temperatures

in the diesel

room above the

120 degree

F design

could occur

as

a result of outside temperature

excursions.

These

conditions could exist for up to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> per excursion

and they would

only occur for less

than

1 X of the plant life.

3.7.2

Tornado generated

missile strike and depressurization

protection:

The team reviewed the tornado protection

study. from missile strike of

the diesel

generator

rooms

and found that three tapered

areas of the

building itself did not have sufficient thickness to resist tornado

missile penetration spalling

as defined in FSAR section 12.2.2.9.2

and

design Criteria BFN-50-C-7101.

The licensee's

position was that Browns

Ferry had sufficient redundancy

in the diesel

generator

design to

support Unit 2 operation

and for a single missile strike,

several

additional

events

would have -to occur before affecting the safe

shutdown/cooldown capability of the station.

The combined probability

of occurrence of all additional

events

reduced

the tornado generated

missile strike contribution to crippling the safety systems of the

station

by two orders of magnitude

below the calculated

frequencies

and

would not significantly alter the public risk factor.

This position was

adequately

documented

in calculation

BFN RAG2-003.

The team also noted that the

DG room air intake

and outlet dampers

did

not have

a tornado depressurization

qualification.

The Licensee

generated

a new preliminary calculation

showing that there should

be no

damper failures at the pressure differential

imposed

by a tornado event

and that the

DG room dampers

would not pose

a damage threat to the

safety equipment in the room.

3.7.3

DG Room Battery

Fume

Hood

/

The team expressed

concern regarding

a non qualified fume hood above the

batteries

in the

DG room.

The fume hood posed

a potential

impact to the

integrity of t'e safety related batteries

below.

The licensee

was

aware

of this deficiency

and restated,

as for other seismic issues,

that the

battery

fume hood seismic qualification was

an item that will be

reviewed to A 46.

3.7.4

Battery

Rooms

1

& 2 Ventilation Requirements

The team identified many undocumented

assumptions,

inconsistencies

and

reference

errors in the

room hydrogen concentration

calculation

HD-

93031-880242.

The licensee

recognized there were numerous errors

and

initiate revision to correct all deficiencies.

To quickly evaluate

the

possible influence

on the adequacy of existing equipment,

the licensee

conducted

a preliminary conservative calculation which indicated that

22

the maximum hydrogen generation

rate would be no'ore than 4.2 cubic

feet per hour with no adverse

consequences

on the equipment installed.

The team accepted

the justification.

3.7.5

Diesel

Engine Intake and Exhaust piping analysis

Reviewing the diesel

exhaust

system seismic qualification calculation

,

'D-(0031-8818838,

the team noted that the exhaust

pipe was not analyzed

using the applicable

code equations of piping analysis

but rather using

an approximate structural

method

and

a high

7 X damping factor.

The

licensee

acknowledged that the methods of piping analysis

would have

been

more. appropriate

in this case,

but the method

used

was conservative

since the analysis calculated

the frequency of the exhaust piping,

applying the moment of inertia of the smaller

end in determining the

acceleration

value -and conservatively'treating

the duct as simply

supported

instead of fixed.

The damping value of 7 5 was

based

on

a TVA

seismic test

program documented

in TVA report MA2-79-1.

The tea'm

accepted this explanation with no further questions.

4.0

MAINTENANCE, TESTING,

CALIBRATION, AND CONFIGURATION CONTROL

The team performed walkthrough inspections of the

EDS to identify the

material condition of the electrical

equipment

and panels.

Portions of

'he

"as installed" configuration of the

EDS were examined to determine

its compliance with design drawings

and documents.

The electrical

maintenance

program,

procedures,

surveillances,

and work orders

were

reviewed to ensure

the

EDS was being properly maintained to function for

the life of the plant.

Data sheets

from completed calibration

and

surveillance

procedures

were reviewed to verify the

EDS operates

in

accordance

with design specifications

and requirements.

The method

used

.for fuse control

was examined to determine if the correct sizes

and

types were installed.

Relay setting sheets

and drawings were reviewed

to determine if an effective -program had

been developed

and implemented

for controlling setpoints for protective relays,

overload relays,

circuit breakers,

switchgear

and timing relays.

Testing

and

surveillance

procedures

for the emergency diesel

generators, were

reviewed to determine if specifications

were being met.

4.1

Conclusions

In the area of configuration control, the team identified several

discrepancies

between the "as installed" molded case circuit breakers

and the design drawings.

The team noted

a potential configuration

control problem with breaker

changeout

in the 480

V SDBs.

The licensee

identified two non lE General Electric type AK circuit breakers

located

in IE shutdown boards.

A problem evaluation report

had already

been

issued.

The team found several

instances

of improperly terminated

spare wiring

in the 250

VDC RHOV boards

and in several

main bank battery chargers.

Additionally, two SDB battery charger disconnect

switches

were

incorrectly left in the "on" position.

Two drawing discrepancies

were

23

noted in the thermal overload setting drawings.

The team noted

a

weakness

in the fuse control

program regarding fuse labelling.

During 'the walkthrough inspections,

the team noted that the material

condition of the plant equipment

was good.

However,

cracked thermal

overload relays were found in the 480

V and

250

VDC fNOV boards

and

a

cracked fuse block was found in a 480

V RHOV board.

Additionally the

team noted that

SDB battery

C had

a degraded intercell jumper cable.

These conditions were adequately

addressed

by the licensee.

Housekeeping

was generally

good in the switchgear,

motor control centers

and electrical cabinets.

The equipment

was clean

and properly

maintained.

An exception

was battery board

2 where several

examples of

poor housekeeping

and excessive dirt were noted.

In the area of preventive maintenance,

the team found that'the

bus

insulation

on the

4 Kv shutdown

boards

was not being inspected.

The

licensee

was utilizing thermography for checking

bus connections,

and

this was identified as

a strength.

The team noted that the maintenance

records

and procedures

for 4 Kv and

480

V switchgear

maintenance

to be

adequate.

The team verified that the protective relays were being calibrated

on

a

scheduled basis.'n

the area of testing

and surveillance,

the team

noted that the licensee

had implemented

an adequate

program for testing

molded case circuit breakers

which encompassed

all safety related

breakers.

Review of the battery discharge tests

revealed that several

batteries

were nearly at the replacement'oint.

The licensee

indicated that they

had design

change

packages

to replace

many of the batteries

during the

upcoming refueling outage.

A procedure

inconsistency

in battery post

terminal torque requirements

was noted in the

DG battery discharge test

procedure.

Overall, maintenance,

testing, calibration

and configuration control

was

being adequately

accomplished.

4.2

Equipment Walkthroughs

3

The electrical

components

examined during inspection walkthroughs

included fuses,

overload heaters,

motor contactors,

protective relays,

circuit breakers,

switchgear,

batteries,

chargers,

HG sets,

cables,

cable trays, transformers,

cubicles

and panels.

The team primarily

examined Unit 2 equipment or shared

equipment required for Unit 2

operation.

The team inspected

the

4 Kv SDBs

and found them to be clean,

well

maintained,

and in conformance with plant'design

requirements.

The 480

V SDBs were also clean

and well maintained.

However breaker

changeout

had led to two non-lE breakers

being placed into the

1E 480

V SDBs.

24

The non-1E breakers

were determined

by the licensee to have

been

installed in safety related

480

V SDB 2A cubicle

3D and 480

V SDB 3A

cubicle 2B.

The licensee

had already

issu'ed

a problem evaluation report

BFPER920039 to investigate.

The breaker in SDB 3A was still installed.

This is identified as

a finding which the resident

inspectors wil'l

follow.

See

A

endix A

Findin

8

During the inspection of the 480

V RMOV boards the team identified

several

configuration control discrepancies.

On 480

V RMOV board

2A the

inboard

and outboard core spray valves (cubicles

13B and

14B) had 30

ampere

molded case circuit breakers

instead of the

7 ampere

breaker

called for on drawing 2-45E751-1.

'RHOV board

2B cubicle

15E for inboard

core spray valve had

a 30 ampere

breaker instead of the

7 ampere

breaker-

called for by drawing 2-45E751-3.

The licensee initiated

a

SCAR

BFSCA920006

and work requests

to replace the breakers.

The team

determined that the oversize

breakers

would not impact operability of

the core spray valves.

See

A

endix A

Findin

9

The team noted several

instances

of degraded

equipment in the 480

V RMOV

boards.

In cubicle

4E of RMOV board

2E,

a cracked fuse block was found..

The licensee

issued, work request

C111446 to repair.

During inspection

of 480

V RMOV board

2A the team found cracked

thermal

overload relays-in

cubicles

4E,

10A,

and

17A.

Work requests

C105431,

C105439,

and

C105438

were issued to repair.

Additionally, the team noted cracked

thermal

overload relays in 250

VDC RMOV board

2A, cubicle

3D and

RMOV board

2B

cubicle 5B.

The team determined that the cracked

components

would not

impact equipment operability.

The licensee

issued

work requests

C104029

and

C104030 to correct.

See

A

endix A

Findin

10

The team noted two drawing discrepancies

while inspecting

thermal

overload relays in the 480

V RMOV boards.

RMOV board

2A cubicle

6B had

the correct overload heater installed.

However, the thermal

overload

setting drawing incorrectly specified the heater.

The licensee

issued

potential

drawing discrepancy

PDD 92-200 to correct the drawing.

Cubicle

7B of RMOV 2A was

shown wired for 3 thermal

overloads while the

installed configuration was

3 thermal

overloads with the

B phase

not

wired.

Potential

drawing discrepancy

PDD 92-201

was issued to correct

the drawing.

See

A

endix A

Findin

9

During the inspection of the

DGs, the team noted that the circuit

breaker for DG start circuit

1 had

a 50 ampere

breaker while drawing 0-

761E580-1 calls for a 30 ampere breaker.

See

A

endix A

Findin

9

During the plant walkthrough improperly terminated

spare cables

were

found inside

250

VDC battery chargers

1,2A,2B,3 and 4.

Additionally,

the team noted improperly terminated wiring in 250

VDC RMOV board

2A

cubicle 7A.

The licensee

issued

work requests

C10344 through

C10348

and

C10431 to correct.

See

A

endix A

Findin

9

The team noted spare battery charger disconnect

switches for SDB battery

chargers

B and

C left in the "on" position.'rawing

0-45E709-1

25

indicated that the disconnect

switches

should

have

been in the "off" .

position.

See

A

endix A

Findin '9

I

During the inspection of batteries,

the team found

a degraded intercell

jumper cable

between cells

60 and

61 of 250

VDC SD battery

C.

Approximately 50 X of the cable's

conductor strands'ere

broken.

Due to

the cable size

and ampacity rating the remaining conductors

would ensure

battery operability.

The licensee

issued

work request

C104393 to repair

the cable.

The team reviewed the fuse control program

SSP 12.56.

The team

identified several

weaknesses

in 'the program.

The licensee

was in the

process of revising the fuse labelling in the plant.

New labelling was

being installed but old labels

were not always being removed.

As many

as three labels for the

same fuse existed in some panels.

Cleared

fuses

were to be replaced

by referring to the fuse label for fuse

identification.

Confusion over which label

was correct could result.

Procedure

DS-E 1.2.3 referred to in the fuse control program requires

special

instructions

such

as

"Do not substitute" to be indicated

on fuse

labelling.

Licensee

personnel

were not aware of the special

instructions to be indicated

on class

lE fuse labelling.

The licensee

revised

SSP 12.56 to require that the Site Engineering

issued Electrical

Fuse'abulation

Drawings

be utilized to determine correct fuse data for

replacement 'of 1E fuses..rather

than the fuse labels.

4.3

Equipment Maintenance Testing

and Calibration

The team reviewed the preventive

maintenance

for switchgear,

motor

control centers,

batteries

and battery chargers.

Maintenance

procedures

for the

4 Kv and 480

V switchgear

were considered

adequate.

Thermography

was being utilized to inspect the swi,tchgear.

This is

considered

a program strength.

The team noted that inspection of bus

bar insulation of 4 Kv switchgear

was not included in the routine

maintenance

of the switchgear.

GE publication GEH-1802,

Metal Clad

Switchgear which is included in manual

BFN-VTM-G080-6060 on 4 Kv

switchgear

recommends

annual

inspection of the bus bar insulation.

Also

recommended

is resistance

measurement

for bus bar insulation for phase

to ground

and phase to phase.

The procedure 'for preventive maintenance

of motor control centers

was

reviewed.

The molded case circuit breaker testing

was found adequate.

All safety related

molded case circuit breakers

were included in the

test program.

Relay calibration for 4 Kv and 480

V systems

were adequate.

Calibration

procedures

and intervals were satisfactory.

The team noted that relays

are not always returned to mid-band during calibration if not found out

of acceptable

range.

For instance,

the overcurrent relay for the

RHR

pump

1D has

an acceptable

range of 36. 1 to 39.9 amperes.

The relay. was

found at 39.8

and left at 39.8 during the last calibration.

Relay

calibration is on

a 48 month frequency.

26

The team reviewed the testing

and surveillance

procedures

and results of

last, surveillances for the

DGs.

The results

and the surveillance,

procedures

were determined to be acceptable.

During the review of battery discharge testing the team noted that

several

batteries

were very close to the

80% capacity replacement

criteria.

DG

C battery was determined to be at 80.67Ã capacity,

DG 3C

battery

was at 86.31. capacity,

and Main Bank 3 battery

was at 89.9X

capacity.

The licensee

indicated that design

change

packages

had

been

prepared to replace

many of the batteries

during the next refueling

outage.

The following DG batteries

were scheduled for replacement:

DG

battery A,B,C,D,3A,3B, and

3C.

The following SD batteries

were

scheduled for replacement:

SD battery A,B,C,D,and 3EB.

Hain Bank 2 and

Hain Bank 3 batteries

were also scheduled for replacement

at the next

refueling outage.

This finding will be followed by the resident

inspectors.

See

A

endix

A

Findin

11

The team noted

an inconsistency

in the battery post terminal torque

requirements for DG battery

3D in the battery discharge test procedure.

One section of the procedure calls for a terminal torque of 10 inch

pounds while another

section requires

110 inch pounds.

The licensee

issued

a procedure

change

NIC-08 to correct the procedure.

4.4

Emergency Diesel

Generator

Preventive

Maintenance

The team reviewed the licensee's

mechanical

preventive maintenance

activities for the

DGs.

A total of 73 maintenance

procedures

were

identified by the licensee

as applicable to the eight DGs.

The

procedures

were written in accordance

with applicable

vendor manuals,

were clearly written and contained

adequate

sign off spaces.

During the team inspection,

the licensee

performed the yearly, three

year,

and six year

PH of the

3C

DG and

a follow-up maintenance

and

a

modification on the

D DG.

The follow-up maintenance

on the

D machine

involved the bolted connection tightness

check required to be performed

six months after the six year

PH.

The modification involved

ECN H7844

and implementing

WP 0031-92 which removed eight of 10 air receiver tank

relief valves.

The. team noted that during the activities involved with the

3C

DG a

voltage regulation failure occurred which drove the voltage to maximum

and also caused

a speed

decrease.

The system engineers

initiated

a TD

which described

the voltage

and

speed

excursion during the performance

of procedure 3-SI-4.9.A. I.d(3C), "Diesel Generator .Annual Inspection".

The

TD originally addressed

the failure in the accident

mode of the DG-

SINGLE UNIT.

The team asked

about the effect of the failure on the

other two modes of the

DG - UNIT IN PARALLEL and

PARALLELED W/SYSTEM.

The system engineers

revised the

TD to include

a discussion of the

effects of the failure on all three

modes.

The team noted that the

failure would have

an effect on all modes

and that

a loss of standby

power under certain conditions would occur.

The item was being reviewed

for possible follow-up.

27

5.0

ENGINEERING AND TECHNICAL SUPPORT

'The team assessed

the licensee's

capability and.performance

regarding

engineering

and technical

support associated

with the

EDS.

The basis

for this assessment

included the following areas:

technical

support

organizations'taff levels,

involvement in identification and

resolution of plant problems,

support of EDS related maintenance

and

operations activities,

and modifications.

5.1

Conclusions

Engineering

and technical

support for EDS activities and design controls

for EDS systems

and components

were generally

adequate

to monitor and

maintain the design function of the

EDS.

Staffing was.adequate

to

provide required

EDS related technical

support.

Maintenance

and

operations

support

was adequate.

The System Engineering

group in

particular was cognizant of system

and component function and

performance.

The group provided strong support for EDS activities

and

involvement in problem identificati,on and resolution

was good.

Design

Engineering

and Hodifications Groups planned modification activity was

appropriately controlled

and documented.

5.2

Organization

and Staff

Engineering

and technical

support for EDS related activities reviewed

by

the team was provided by the on site engineering

organizations

during

the period preceding this inspection.

The

BFN engineering

organization

does not have

an offsite design group

and the onsite group was larger

than most facilities.

This was due to the ongoing modifications

following Unit 2 restart

and the post Unit 2 recovery deferred

items.

The on site engineering staff for Unit 2 was approximately

300 technical

personnel

broken

down as follows:

190 design engineers,

90 of which

~

were contractors with 18 design engineers

assigned

to operations

support

and

8 in the electrical

area;

90 system engineers,

of which 15 were

assigned

to Unit 3 recovery,

25 assigned

to engineering

support

and

7

assigned

to electrical,

and

24 procurement

engineers of which 9 were

assigned

to electrical

procurement~

Three offsite groups provided support

and direct hands

on activities

involving the 'EDS.

The first group was corporate engineering

which

provided oversight

and technical

support to site design engineering

in

regards

to the

EDS both

as requested

and self initiated.

The second.

group was corporate

maintenance

which provided on-site technical

support

for plant maintenance.

The third group was Transmission

and Customer

Services,

which provided direct hands

on activities involving the

EDS.

The systems

engineering

organization at Browns Ferry was established

in

mid-1986.

A total of 19 system engineers

were assigned

to the

Electrical

and

IKC group with seven

engineers

assigned

to the

EDS

section

and one within the section specifically assigned

to the

DGs.

28

5.3

Maintenance

and Operations

Support

The majority of EDS related support

was provided by the System

Engineering

group which in conjunction with the design,

procurement,

operations

and maintenance

groups provided ongoing technical

support for

parts replacement,

procedure

changes,

event management,

design

change

plant acceptance,

USNRC requirements/inquiries,

tracking of punchlist

.

items,

and trending of, EDS equipment performance.'

sample of 37 trend failure reports

from the period of 1987 to present

were reviewed to determine engineering

involvement.

The TFRs from the

earlier time frame,

1987 to 1989, indicated

a lack of analysis for

trending.

During the

1987 to 1989 time period, trending of equipment

failures was performed

by maintenance

personnel.

A TFR from 1988 stated

that

a failure of the

same specific component

on several

DGs did not

indicate

a" trend because

the failure occurred

on different DGs.

Since

1989 engineering

involvement improved.

A TFR from 1990 involving.the A,

8,

C,

D DGs fuel oil transferring resulted in a design

change,

DCN

N9092, which removed the check valves in the suction line for the eight

(two per

DG) transfer

pumps.

During the

EDSFI, the team noted that all

trending failures were performed

by the system engineers.

5.4

Problem Identification and Resolution

The team reviewed engineering

involvement in problem identification and

resolution activities associated

with the EDS..

The Incident

Investigation

Reports

program,

which was the facilities primary

mechanism for problem identification and resolution 'was reviewed to

assess

engineering

involvement.

A sample of 38 IIRs, from September

1988 to March 1992 involving the

EDS, were reviewed for aspects

of root cause

analysis,

resolution,

corrective action,

and, engineering

involvement.

The IIRs during the

earlier time frame from September

1988 to December

1989

(a total of 13

IIRs) were lacking in root cause

analysis,

resolution, corrective action

and engineering

involvement.

An example of this was IIR 88-04 which

documented

an electrical fire inside

a

4

KV circuit breaker.

The root

cause

was not determined.

The IIRs during the later time frame,

December

1990 to March 1992 (a total of 14 IIRs), the level of root

cause

analysis

and corrective actions

performance

on the IIRs was

appropriate.

An example of this was IIR 91-04, which documented

a

temporary failure of an auxiliary switch contact

on

a

DG tie breaker

to

a 4 KV shutdown board.

This resulted in the corresponding

core spray

and

RHRSM pumps not sequencing

on during

an accident signal logic

actuation.

As a result of the IIR activities, the licensee initiated

a

design

change to provide reliable load sequencing

at 4 kV SDBs.

Additional engineering

involvement was indicated

by IIRs91-158

and 92-

017, which both resulted

in the initiation of DCNs.

Implementation of

these

DCNs were to resolve

a recurring

ESF actuation

problem and

make it

e'asier for plant personnel

to determine

what caused

the circuit

protectors to trip such

as overvoltage,

underfrequency,

and

undervoltage.

5.5

Hodifications

The

BFN facility installed

numerous modifications affecting the

EDS to

support Unit 2 restart during the extended

outage

and recovery.

A

sample of these modifications were reviewed for post modification

testing,

10 CFR 50.59 safety evaluations,

material

procurement,

and the

interface

between

design

development

and installation responsibilities.

I

The team reviewed modifications installed

as

a result of trend analysis,

restart testing,

integrated

system testing

and system analysis.

Additionally, temporary modifications involving the

EDS and supporting

systems

were reviewed to determine engineering

involvement.

Appropriate

design controls were demonstrated.

The

PHTs indicated

adequate

acceptance

of the

DCN.

The team noted that

a procurement

problem was identified involving the

RHS-9 Hiero Versa Trip circuit breaker conversion kit modifications

used

in the

EDS.

This item was identified as

a result of the Unit 3 recovery

effort and

a contractors

design activities.

The team was informed by

the licensee that when the

RHS-9 trip units were procured for use in the

Unit 2 recovery effort, the procurement

documents

did not specify

an

ambient temperature

or a cabinet temperature.

The only temperature

specified

was

104 degrees

F, which was

an

Eg requirement.

The item was

being followed by the resident inspector.

6.0

EXIT HEETING

The team met with licensee

representatives

(denoted

in Appendix C) at

the conclusion of the inspection

on Hay 22,

1992, at the plant site.

There were no dissenting

comments received.

Proprietary information is

not contained

in this report,

APPENDIX A

FINDINGS

FINDING 1:

Existing Calculations

Did Not Contain Sufficient Data to Determine

LOCA Load Sequencing

Voltage Profile (paragraph

2.2. 1. 1)

DESCRIPTION:

Calculation

ED-(2000-870026,

Revision 9, "4.16 kV and Busload

and Voltage Drop

Calculations. with Offsite Power",, was intended to determine

minimum voltages

at safety

buses during

LOCA load sequencing.

However, the calculation'id not

contain sufficient data to establish

the actual voltage profile at the safety

busses

during worst case conditions.

The Licensee

provided additional

computer runs which established

the actual. profile and which demonstrated

adequate

system performance

SAFETY SIGNIFICANCE:

This calculation

was necessary

to establish that adequate

voltages

are

available during load sequencing

and that the degraded

voltage relays will

reset within required time intervals.

Failure of relays to reset

could cause

loss of offsite power to safety loads during

LOCA load sequencing

and present

unnecessary

challenges

to the standby

power systems.

FINDING 2:

Incorrect Acceptance Criteria for Degraded

Voltage Relay in

Surveillance Instruction (paragraph

2.2. 1.3)

DESCRIPTION:

The acceptance criteria in Surveillance Instruction 3-SI-4.4.A.4.C(I),

Revision

1,

"4160

V SDB 3EA and

3EB Under/Degraded

Voltage Time Delay Relay

Calibration", did not properly reflect the

26

V tolerance

applicable to the

Degraded

Voltage Relay dropout

and reset values,

as determined

in Calculation

ED-(2211-890144,

Revision 4, Setpoint

and Scaling Calculations

4 kV Bus

Degraded

Voltage Relays

(ITE 27N),

as follows:

The Surveillance Instruction,

paragraph

7.2.3. 12, allowed the relay

reset

value to be left at 3987.7

V.

Adding the tolerance

determined

in

the setpoint calculation,

the actual reset voltage could have drifted to

3987.7+26= 4013.7

V.

This is higher than the

TS allowable of 3999 V.

2.

3.

The acceptance criteria stated

in the Surveillance Instruction did not

provide

a lower limit for the reset voltage,

so that it could have

been

set close to the dropout value.

Acceptance criteria 6.1.3 stated that

reset

should

be "less than or equal to 1.5L above trip=-value."

This

could have resulted

in convergence

of the dropout

and reset

due to

setpoint drift.

The Surveillance Instruction,

paragraph

7.2.3. 13 allowed the dropout

voltage to be left as low as 3911.25

V.

Applying the tolerance

determined

in the setpoint calculation,

the actual

dropout could have

drifted as low as 3911.25-26=

3885.25

V.

This was below than the

TS

allowable of 3900 V.

The licensee

revised the Surveillance Instruction to conform to constraints

determined

in the latest setpoint calculation.

In addition, the licensee

stated that applicable administrative procedures

shall

be revised to assure

that appropriate

design inputs are

used in all Surveillance Instructions.

SAFETY SIGNIFICANCE:

Improper criteria used in this surveillance instruction could have resulted

in

operating voltages

below analyzed

minimum requirements,

or in loss of offsite

power to safety loads during

LOCA load sequencing

due to failure of Degraded

Voltage Relays to reset.

FINDING 3:

460

V Motors Do Not Have Critical Voltages Stated in FSAR

~

(paragraph

2.2.1;4)

DESCRIPTION:

Calculation

ED-(2000-870027,

Revision 3,

"460

V Class

1E Motors and Equipment

Volt Drop", Attachment

2, demonstrated

that certain motors did not have the

minimum required terminal voltage stated

in section 8.4.8. 1.4 of the

FSAR as

follows:

3M031515015

3M031515019

U3

CR AHU A

U3

EL 593

AHU3A

Component

Tag

'Description

Running Volts

Criteria 414

409.398

413.876

Percent of 460V

(90%)

(88.9%)

(89.9%)

The Licensee

demonstrated

adequate

equipment operation

based

on available

equipment design margins.

SAFETY SIGNIFICANCE:

This item represented

a deviation from a

FSAR commitment but did not have

safety significance since

adequate

equipment

performance

was demonstrated.

FINDING 4:

Calculation'Weaknesses

(paragraph

2.2.1.4)

DESCRIPTION'he

following weaknesses

were noted during

a review of various

EDS

calculations.

Calculation

ED-(2000-870027,

Revision 3,

"460V Class

lE Motors and

Equipment Volt Drop":

a 0

The calculation relied on equipment

design margins to justify

voltage below manufacturer's

recommended

minimums rather than

removing

known conservatism

or correcting circuit deficiencies,

for the following motors:

Component

Tag

3M031515015

3M031515019

Description

U3

CR AHU A

U3

EL 593

AHU 3A

, Running Volts

Criteria 414

409.398

413.876.

c ~

Section 7.0.2. justified voltage below the criteria stated

in

section 3.0 based

on adequate

torque available at 70

1. voltage for

NEMA B motors.

However, this justification did not consider the

effects of increased

current

and possible tripping of protective

devices.

In response,

the licensee

provided additional

justification which demonstrated

adequate

performance.

Calculation

ED-(2000-870027,

paragraph

3.7 stated that the

calculation tabulated

in Attachment

2 used the lowest actual

operating voltages at the various

buses

as determined

by

calculation

ED-f0999-890090.

However,

some voltages in attachment

2 did not match the lowest voltages in calculation

ED-(0999-890090.

Examples

are

as follows:

Bus

090 Calculation

Attachment

2

CB VENT BD A

434V (Table 1.2)

435V

DSL AUX BD A

446V (Table

1)

450V

The team determined that the use of non-conservative

voltages did not

affect the final results.

Calculation

ED-(2211-890144,

Revision 4, "Setpoint

and Scaling

Calculations

4 kV Bus Degraded

Voltage Relays

(ITE 27N)":

'a ~

Paragraph

8,

page

5a, stated that the

26

V tolerance

applicable to

the

DVR dropout setting-was

random

so that it was unlikely that

two relays would be subject to the maximum inaccuracy at the

same

time.

This contention,

combined with two out of three logic, was

used to justify using the actual setpoint of 3920

V as the lowest

possible

bus voltage rather than using the setting less tolerance.

However, at least

two of the factors contributing to the 26

V

tolerance

are not random

as applied to 'two separate

relays,

temperature

effect (TNe),

and power supply effect (PSEe).

This

increase's

considerably the chance that drift in the

same direction

will occur simultaneously

on two (or three) relays.

In addition,

the magnitude of drift inaccuracy

(De) is time dependent

which

could effect all relays calibrated at the

same time similarly.

Consequently,

minimum voltage

used

as the basis -for degraded

voltage calculations

should reflect actual setting less tolerance.

The team determined,

however, that using the non-conservative

voltage did not have

a significant effect on the final results of

the calculations

concerned.

C.

Paragraph

8.0 stated that calculation

ED-(2000-870026

determined

the minimum steady state voltage

on

a 4 kV SD bus was 3986 V.

However, this figure could not be found in the referenced

~

~

d.

calculation.

The team determined

the actual

minimum voltage

was

4004

V which was less limiting than the referenced figure.

Paragraph

8.0 incorrectly stated that the dropout

and reset

would

drift in the

same direction

as justification for. the small

{20 V)

difference

between the two settings.

The licensee

revised the

calculation

and established

settings

which will prevent

convergence

of dropout

and reset

due to drift.

SAFETY SIGNIFICANCE:

The items noted

above were determined to be isolated

examples of weakness

in

otherwise generally conservative calculations.

None of these

items

represented

operability concerns

and all were appropriately resolved

by the

licensee

by calculation revision or other justification.

FINDING 5:

Control

Bay Water Chiller A and

B circuit breaker settings.

(paragraph

2.3.4.2)

DESCRIPTION:

Calculation ED-f2000-870548,

Revision

10, identified the analytical

basis for

the long term pick-up settings of the load center circuit breakers

{480 V).

For a motor having

a service factor of 1. 15 the calculation asserts

that the

setting should

be greater or equal to 1391 of the full load current.

This

constraint

had not been applied to all motor loads

(class

1E and non-1E)

and

in particular to the

1E load "Control

Bay Water Chiller B".

The result of this finding was that with the motor demanding full load current

at its rated terminal voltage of 460 V, the operating point on the

coordination curve lies within the tripping region of the circuit breaker.

The problem would be intensified at degraded

bus voltage conditions,

when the

motor was drawing more current.

The problem also occurs

on "Control Bay Water

Chiller A".

The licensee

stated that the circuit breaker setting

was inappropriate,

and

advised that

a safety

assessment

report

DCNGI7047A dated

September

27,

1991

had identified this condition;

and

a modification to the breaker

was being

initiated.

The circuit breaker will be fitted with a new G.E.

Type RHS-9 trip

unit set to 132/ of 'the motor full load current,

and work request

C044046

had

been written to install the unit.

SAFETY SIGNIFICANCE:

This equipment

was used to provide cooling for the control

room and equipment

rooms located

on elevation

593.

The equipment relying on the chiller for

cooling could operate for approximately

30 minutes before being adversely

affected

by the loss of cooling, giving adequate

time for operator action.

In

addition,

some cooling was available from chillers in Unit 3, which are not

subject to these possible

inadvertent trips because

of the different circuit

breaker settings.

5

FINDING 6:

Procedure

Weaknesses

(paragraph

2.4,2)

DESCRIPTION:

The following weaknesses

were noted in procedures for operating the

EDS:

l.

Alarm response

procedure I/2 ARP 9-23, Revision 12, did not provide

'dequate

guidance regarding Diesel Generator

Ground Fault Annunciation.

The diesel

generators

were grounded

using

a high resistance

scheme.

This limits the magnitude of ground fault currents

and permits continued

operation of the system during an emergency.

A ground fault was

annunciated

as

a "DIESEL GEN X GROUND FAULT".

In case of LOOP,

procedures

required transfer

back to the offsite source through the

USSTs, if it became available again.

.However,

these transformers

were

grounded

through

a low resistance

scheme

which would allow much larger

fault currents

and consequent

loss of the faulted load.

In case of'n

emergency,

continued operation with a fault limited to a small current

would be preferable to loss of the load.

However, the alarm response

'procedure

did not caution operators

against

attempting

a retransfer

.

prior to isolating the fault so that operators

could attempt to transfer

back to the preferred

source,

rather than first selective tripping

loads,

conditions permitting, to locate the fault.

In addition, the

"Probable

Cause" section of the'procedure

did not clearly alert the

operators that the fault could be anywhere

on the 4. 16

kV system,

not

just on the

DG.

The Licensee revised the procedure to address

these

concerns.

2.

Procedure

O-OI-82, Revision 35,

"Standby Diesel

Generator

System

Operating Instructions", did not provide guidance

on restarting large

loads,

in particular

a 2000 hp

RHR pump, should it become

disconnected

while being powered from a diesel generator.

In response

to this

concern,

the licensee

provided specific instructions for reducing load

on the

DGs to prevent overloading

and to check for any 480

V loads which

may be inadvertently tripped due to the voltage dip during restart.

SAFETY SIGNIFICANCE:

The above

examples

do not represent

threats to the operability of the

EDS but

could have resulted.'in

unnecessary

interruption of power to important loads.

FINDING 7:

D.C. Battery Systems

Ground Detectors

(paragraph

2.5.4.3)

DESCRIPTION:

Each class

1E battery system at the

BFN employs

a ground detection

system,

comprising principally a

DC center zero voltmeter acting

as

a null detector of

a Wheatstone

bridge, the

arms of the bridge being two resistances

connected

between the positive

and negative

poles of the battery supply, 'and the

resistance

to ground of each pole.

With no ground fault on the system the

voltmeter reading is zero.,

The system at the

BFN uses

inverse logic, where

an bperator conducting

a daily

check, interprets

a zero reading

as

a "no ground fault " situation,

whereas

a

zero reading

may also

be the consequence

of a faulty meter or open circuited

connections.

Checking

and calibration of the meter is at three year

intervals,

and results

from BFN indicated that the incidence. of faulty meters

t'o be about

28%.

A secondary

system employing meter relays

was also fitted to each battery

system,

the meter relays being energized

from non-1E

120

VAC supplies.

The

relay gives annunciation

in the control

room of a ground fault or of a relay

failure or of a loss of power to the unit.

The system

was not set to detect

a

high/medium

impedance

ground fault, and should

be self powered,

or powered

from the

DC battery, for reliable operation.

SAFETY SIGNIFICANCE:

Failure of the voltmeter or the connections

thereto, will not be recognized

during the daily check of the system,

and more than

one ground fault can occur

on the system without being detectable

by the existing monitor.

No

calculation

was available relating meter reading to ground fault resistance

but the -assessment

by the team was that

a significant ground

may occur before

the trip point setting of the associated

relay was reached

(175 volts for the

250

VDC and 240

VDC for the

125

VDC battery systems).

FINDING 8:

Improper Breaker Replacement

(paragraph

4.2)

DESCRIPTION:

The team identified that circuit breaker

changeouts

in the 480

V SDBs

had

resulted in two non-class

lE breakers

being placed in class

lE SDBs.

The

licensee identified that this improper circuit breaker

changeout

had occurred

in two instances.

The circuit breakers for 480

V SDB 2A, cubicle

3D and

480

V

SDB 3A, cubicle

2B were improperly replaced.

The licensee

issued

a problem

evaluation report

BFPER920039 to investigate this occurrence.

SAFETY SIGNIFICANCE:

Replacement

of class

1E circuit breakers with non-class

lE breakers

could

result in failure of the circuit breakers

during

a design basis

event

and

unavailability of safety related

equipment.

FINDING 9:

Configuration Control

(paragraph

4.2)

DESCRIPTION:

The team found the drawings for the

EDS correctly reflected the installed

condition of the

EDS with several

exceptions.

Instances

were found where

configuration control

had not been maintained.

In 480

V RMOV board

2A, 30

ampere

breakers

were installed for the inboard

and outboard core spray valves

of compartments

13B and

14B.

Drawing 2-45E751-1

indicated that

a 7 ampere

breaker

was required for these circuits.

In 480

V RMOV board

2B,

a 30 ampere

breaker

was installed for the inboard core spray valve.

Drawing 2-45E751-1

indicated

a

7 ampere

breaker

was required for this circuit.

The licensee

initiated work request to replace the breakers.

During the inspection of the

DGs, the team identified another incorrectly

installed circuit breaker.

Drawing 0-761E580-1 required

a 30 ampere

breaker

for the

DG start circuit 1.

The team observed

a 50 ampere breaker installed

in this circuit;

During the inspection of the battery chargers

the team observed

unterminated

and unidentified wiring in 250

VDC battery chargers

1,

2A, 2B,

3 and 4.

Improperly terminated

spare. cables

were found inside

250

VDC RHOV board

2A,

cubicle 7A.

The team noted during the inspection of the battery chargers that the position

of the

SD battery charger

spare disconnect

switch for chargers

B and

C were in

the "on" position.

Drawing 0-45E709-I indicated that the switch should

be in

the "off" position when the spare

charger

was not in use.

SAFETY SIGNIFICANCE:

Loss of configuration control

can result in lack- of plant integrity and

failure of safety

systems

to operate

in accordance

with design requirements.

FINDING 10: Cracked

Thermal

Overload Relays

(paragraph

4.2)

DESCRIPTION:

The team noted instances

of cracked

thermal overload relays.

The relays

were

found in 480

V RMOV board

2A, cubicles

4E,

10A,

and

17A.

Cracked thermal

overload relays

were also found in 250

VDC

RMOV board

2B, cubicle 5B.

Work

requests

were issued

by the licensee to replace

the cracked thermal overloads.

SAFETY SIGNIFICANCE:

Failure of thermal

overload relays could result in improper operation of the

relays

and unavailability of, safety equipment.

FINDING ll: Battery Capacity:

(paragraph

4.3)

DESCRIPTION'he

team noted that several

batteries

were nearing the replacement criteria of

80 / capacity.

Diesel

Generator

C battery

was at 80.67

% capacity.

The

licensee

indicated that during the next refueling outage the Hain Bank

2 and

Main Bank 3 batteries

were scheduled for replacement.

Also, scheduled for

replacement

were

SD batteries

A, B, C,

D,

and

3EB and

DG batteries

A, B,

C, D,.

3A, 3B,

and 3C.

SAFETY SIGNIFICANCE:

Inadequate

battery capacity could result in unavailability of battery

power to

meet design loading requirements

for the battery during loss of ac power.

AECL

A-H

ASHRAE

AWG

C

DG

ECN

EDS

~EDSFI

EECW

Eg

DCN

ESF

F

FSAR

GDC

Hp

HPCI

HVAC

IS,C

IIR

IFI

IEEE

kA

KVA

kv

kW

LER

LOCA

LOOP

MCC

MG

PM

PMT

RCIC

RHR

RHRSW

RPS

RPT

RMOV

SDB

SBO

SCAR

SER

TD

TFR

TS'SST

VAC

VDC

VIO

APPENDIX B

ABBREVIATIONS AND ACRONYMS

Centigrade

Diesel Generator

Engineering

Change Notice

Electrical Distribution System

Electrical Distribution System Function

Emergency

Equipment Cooling Water

Environmental gualification

Design

Change Notice

al Inspection

Emergency Safety Function

Fahrenheit

Final Safety Analysis Report

General

Design Criteria

Horsepower

High Pressure

Coolant Injection

Heating, Ventilation and Air Conditioning

Instrumentation

5 Control

Incident Investigation Report

Inspector Follow-up Item

'nstitute

of Electrical

and Electronic

Kiloampere

Kilovolt-Ampere

Kilovolts

Kilowatts

License

Event Report

Loss of Coolant Accident

Loss of Offsite Power

Motor Control Center=

Motor Generator

Planned

Maintenance

Post Modification Testing

Reactor

Core Isolation Coolant

Residual

Heat

Removal

Reactor

Heat

Removal Service

Water

Reactor 'Protection

System

Reactor Protection Trips

Reactor

Motor-Operated

Valve

Shutdown

Bus

Station Black Out

Significant Corrective Action Report

Safety Evaluation Report

Test Deficiency

Trend Failure Report

Technical Specification

Unit Station Service Transformer

Volts Alternating Current

Volts Direct Current

Violation

Engineers

Atomic Energy Canada,

Ltd.

Ampere Hour

American Society,

Heating, Refrigeration,

and Air Conditioning

Engineers,'nc.

American Wire Gauge

l ~

APPENDIX C.

PERSONS

CONTACTED

Licensee

Employees

J.

• H

• R

• D

D.

• C

• H

• R.

• J

T.

• S

R.

D.

H.

• R.

• D

T.

• J

F.

D.

+J

E.

R.

J.

• p

K.

B.

• S

• W.

• H.

"R.

• D

Ballard, Principle Engineer

Bajestani,

Technical

Support

Manager

Baron,

Manager Licensing

Burrell, Lead Electrical Engineer-

Byers,

System Engineer,

Diesel

Generators

Crane,

Maintenance

Manager

Crisler, Site Engineer-

Cutsinger, Civil Engineer

Dollar, Shift Operating Supervisor

Elms, Assistant Shift Supervisor

Hilmes, Supervisor

Technical

Support,

IKC

Hyde,

Procurement

Lead Engineer

Johnson,

Electrical Engineer

Jones,

.Engineering Specialist

Jones,

Operations

Superintendent

Kehoe,

gA

Langley, Principle Engineer

Maddox, Engineering

Manager

McCluskey, Vice President

Restart

Melville, Document Control

Nicely, Corporate

Senior Electrical

Engineer

Ridgell, Compliance

Engineer

Rogers,

Supervisor

Maintenance

PM

Rupert,

Manager Engineering Modifications

Salas,

Compliance

Manager

Schouten,

Bechtel Calculation Engineer

Shingleton,

Compliance

Engineer

Spencer,

Licensing Project Manager

Troutt,

gA Specialist

Turner guality Assurance

Manager

Wright, Principal Electrical

Engineer

Zerinque,

Vice President

Browns Ferry

.*Attended exit meeting