Information Notice 1998-36, Inadequate or Poorly Controlled, Non-Safety-Related Maintenance Activities Unnecessarily Challenged Safety Systems: Difference between revisions

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{{#Wiki_filter:~0- f9AcreUNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555-0001September 18, 1998NRC INFORMATION NOTICE 98-36: INADEQUATE OR POORLY CONTROLLED, NON-SAFETY-RELATED MAINTENANCE ACTIVITIESUNNECESSARILY CHALLENGED SAFETY SYSTEMSAddresseeAll holders of operating licenses for nuclear power reactors.purposeThe U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to alertaddressees to several recent events in which inadequate or poorly controlled, non-safety-related maintenance activities resulted in unnecessary challenges to safety systems. It isexpected that recipients will review the information for applicability to their facilities and consideraction, as appropriate to avoid similar problems. However, suggestions contained in thisinformation notice are not NRC requirements; therefore, no specific action or written responseis required.
{{#Wiki_filter:~0- f 9 Acre UNITED STATES NUCLEAR REGULATORY


==Description of Circumstances==
COMMISSION
BRAIDWOOD UNIT 2On January 18, 1996, with Braidwood Unit 2 operating at full power, .offsite power was lost.Inadequately secured roofing repair materials located on the roof of the adjacent servicebuilding were blown off the roof during a rain storm, causing a phase-to-ground arc on one oftwo station auxiliary transformers (SATs). As designed, the second SAT tripped when the firstSAT failed. Both emergency diesel generators (EDGs) automatically started and all safe-shutdown loads automatically sequenced on to the engineered safety feature (ESF) buses. Allautomatic bus transfers occurred as designed, maintaining power to non-ESF buses from theunit auxiliary transformers (UATs). The reactor remained stable at full power throughout theevent. To restore offsite power to Unit 2, the licensee cross-tied both Unit 2 ESF buses to therespective ESF buses of Unit 1, which also remained at full power throughout the event.Inspection of the faulted SAT revealed damage to (1) the Phase B and C bushings and (2) agas detector relay on top of the transformer where heavy arcing occurred. The licenseedetermined that the Initiating event was a Phase C arc-to-ground, followed by a Phase B tovNOrT g NO -98T- goz 98 0e 8<9809 td n


f IN 98-36September 18, 1998 Phase C arc. A 345-kilovolt switchyard breaker, Which connected the SAT to the switchyardring bus, was also damaged. Approximately one square foot of the Phase B bushing wasblown out.BYRON UNIT IOn May 23, 1996, with the Unit 1 reactor shut down In excess of a month for a refueling outage,offsite power was lost when one of the two Unit I SATs Isolated because of a Phase A toPhase B current differential relay operation. The second SAT tripped as designed when thefirst SAT failed. Both EDGs automatically started and all safe-shutdown loads automaticallysequenced on to the ESF buses. Because the reactor was shut down, power to non-ESFbuses was lost and two service water pumps and a station air compressor common to bothByron units tripped. Without the service water pumps, Unit 2, which was operating at fullpower, had no cooling water to many loads, including the main generator auxiliaries, station aircompressors, condensate pumps, and condensate booster pumps. Subsequently, Unit 2 wasmanually tripped.The licensee determined that the SAT that initially tripped underwent a phase-to-ground fault ona Phase B insulator. The failed insulator was located outdoors, about halfway between the SATand the auxiliary building. After Initiating, the arc continued down the bus bar, Increasing inwidth until It involved the other two phases. Air and water present in the bus bar duct washeated by the arc and resulted in pressurization of the duct.Chronic water leakage through inadequately caulked Insulator mounting holes and through animproperly compressed gasket caused degradation of the insulator metal inserts and Insulatormaterial between these inserts. Eventually, the bus flashed to ground through the degradedinsulator and initiated the transient.PERRYOn June 5, 1997, Perry was operating at full power when an automatic reactor scram occurredfollowing a three-phase fault in one of two high-voltage secondary winding terminationcompartments of the UAT. The fault resulted in the actuation of the auxiliary transformer phasedifferential relay, a main generator lockout, a main turbine trip, and fast closure of the turbinecontrol valves.At the time of the transient, safety-related electrical loads were being supplied by the in-servicestartup transformer. The non-safety-related electrical loads supplied by the transformerautomatically transferred to the startup transformer except for the bus that was faulted.Operators stabilized the plant without major complication.The licensee determined that the fault had developed as a result of an accumulation of moistureand dust that had entered the termination compartment housing where a 2-Inch-long piece ofgasket material was missing from the compartment housing-to-transformer sealing surface.The missing piece of gasket material may have been lost during work performed when
===OFFICE OF NUCLEAR REACTOR REGULATION===
WASHINGTON, D.C. 20555-0001 September


K>1IN 98-36September 18, 1998 replacing the auxiliary transformer following failure of the transformer on May 30, 1996. Thecause of that failure was attributed to Inadequate original design or poor assembly practices orboth.POINT BEACH UNIT IDuring a severe storm on January 8, 1998, a ground In the low-voltage-side bus duct causedthe failure of the Unit I SAT. This failure and a failure of the 13.8-kilovolt automatic bus transferto the Unit 2 SAT resulted in the loss of normal power to the Unit I safeguards buses. TheEDGs subsequently started and restored power to the buses. Unit I remained at 98 percentpower throughout the transient. Unit 2 was in cold shutdown.The licensee attributed the failure of the transformer to the buildup of condensation internal tothe buses and long-term insulation degradation In the bus duct on the low-voltage side of thetransformer. Before the transformer failed, the circuit breaker for a heater designed to keep thebus duct dry would not remain closed. Consequently, in August 1996, the licensee left thecircuit breaker open and wrote a work order for its repair. However, work schedulers did notrecognize that the bus duct heater was inoperable with the circuit breaker open, and the workorder was erroneously classified as "minor maintenance" and given low priority. At the time thetransformer failed, the work order was in the "backlog' of maintenance Items. In addition to theinoperable heater, the:licensee determined that the lack of a routine inspection program for thebus ducts may have contributed to the event. Inspection of the bus ducts after the transformerfailed revealed insulation breakdown that would likely have been Identified through a periodicInspection program.DiscussionThese events illustrate the potentially significant consequences of inadequate or poorlyperformed maintenance activities on non-safety-related plant components. Unnecessarychallenges to plant safety systems or control room operators or both could result frominadequate control or inattention to detail during non-safety-related maintenance activities. Thepotential impact on safety systems of such activities as the re-roofing of nuclear power plantsupport buildings, the Installation of gaskets, or the caulking of outdoor components, couldeasily be overlooked. In addition, several of the events discussed here highlight the need forlicensees to have better control over the maintenance activities of contractor and non-stationutility employees, and the need for thorough periodic walkdowns or preventive maintenance onauxiliary transformers and the associated outdoor bus ducts.
18, 1998 NRC INFORMATION


IN 98-36September 18, 1998 This information notice requires no specific action or written response. However, recipients arereminded that they are required to consider Industry-wide operating experience (including NRCINs) where practical, when setting goals and performing periodic evaluations under Section50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclear PowerPlants," of Part 50 of Title 10 of the Code of Federal Regulations. If you have any questionsabout the information In this notice, please contact one of the technical contacts listed below orthe appropriate Office of Nuclear Reactor Regulation (NRR) project manager.eJack , Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: Mike Kunowski, Region IlIl John Neisler, Region IlIl630-829-9816 630429-9718E-mail: mak3@nrc.gov E-mail: jhn@nrc.govAttachment: List of Recently Issued NRC Information Notices
NOTICE 98-36: INADEQUATE


A,(ttachment 1IN 98-36September 18, 1998 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformationNotice No.Date ofIssuanceSubject98-35Threat Assessments andConsideration of HeightenedPhysical Protection Measures914/98Issued toAll U.S. NRC fuel cycle facilitiespower and non-power reactorlicensees (Safeguard issues, notfor public disclosure.)98-3498-3398-3298-31NRC Configuration ControlErrorsNRC Regulations ProhibitAgreements that restrict orDiscourage an Employee fromParticipating In Protected ActivitiesProblems Associated with Post-Fire Safe-Shutdown CircuitAnalyses8/28/9881281988126198All holders of Operating licensesfor nuclear power reactors, exceptfor those who have ceasedoperations and have certified thatfuel has been permanentlyremoved from the reactor vesselAll holders of a U.S. NuclearRegulatory Commission (NRC)license.All holders of operating licensesfor nuclear power reactors, exceptthose who have permanentlyceased operations and havecertified that fuel has beenpermanently removed form thereactorAll holders of operating licencesfor nuclear power reactors, exceptthose licensees that havepermanently ceased operationsand have certified that fuel hasbeen permanently removed fromthe reactor vessel.Fire Protection System Design 8/26/98Deficiencies and Common-ModeFlooding of Emergency Core CoolingSystem Rooms at Washington NuclearProject Unit 2OL = Operating LicenseCP = Construction Permit
OR POORLY CONTROLLED, NON-SAFETY-RELATED


-IN 98-36September 18, 1998 IN 98-xxSeptember xx, 1998  I
MAINTENANCE


}}
ACTIVITIES
 
UNNECESSARILY
 
CHALLENGED
 
SAFETY SYSTEMS Addressee All holders of operating
 
licenses for nuclear power reactors.purpose The U.S. Nuclear Regulatory
 
Commission (NRC) is issuing this information
 
notice (IN) to alert addressees
 
to several recent events in which inadequate
 
or poorly controlled, non-safety- related maintenance
 
activities
 
resulted in unnecessary
 
challenges
 
to safety systems. It is expected that recipients
 
will review the information
 
for applicability
 
to their facilities
 
and consider action, as appropriate
 
to avoid similar problems.
 
However, suggestions
 
contained
 
in this information
 
notice are not NRC requirements;
therefore, no specific action or written response is required.Description
 
of Circumstances
 
BRAIDWOOD
 
UNIT 2 On January 18, 1996, with Braidwood
 
Unit 2 operating
 
at full power, .offsite power was lost.Inadequately
 
secured roofing repair materials
 
located on the roof of the adjacent service building were blown off the roof during a rain storm, causing a phase-to-ground
 
arc on one of two station auxiliary
 
transformers (SATs). As designed, the second SAT tripped when the first SAT failed. Both emergency
 
diesel generators (EDGs) automatically
 
started and all safe-shutdown loads automatically
 
sequenced
 
on to the engineered
 
safety feature (ESF) buses. All automatic
 
bus transfers
 
occurred as designed, maintaining
 
power to non-ESF buses from the unit auxiliary
 
transformers (UATs). The reactor remained stable at full power throughout
 
the event. To restore offsite power to Unit 2, the licensee cross-tied
 
both Unit 2 ESF buses to the respective
 
ESF buses of Unit 1, which also remained at full power throughout
 
the event.Inspection
 
of the faulted SAT revealed damage to (1) the Phase B and C bushings and (2) a gas detector relay on top of the transformer
 
where heavy arcing occurred.
 
The licensee determined
 
that the Initiating
 
event was a Phase C arc-to-ground, followed by a Phase B to vNOrT g NO -98T- goz 98 0e 8<9809 td n
 
f IN 98-36 September
 
18, 1998 Phase C arc. A 345-kilovolt
 
switchyard
 
breaker, Which connected
 
the SAT to the switchyard
 
ring bus, was also damaged. Approximately
 
one square foot of the Phase B bushing was blown out.BYRON UNIT I On May 23, 1996, with the Unit 1 reactor shut down In excess of a month for a refueling
 
outage, offsite power was lost when one of the two Unit I SATs Isolated because of a Phase A to Phase B current differential
 
relay operation.
 
The second SAT tripped as designed when the first SAT failed. Both EDGs automatically
 
started and all safe-shutdown
 
loads automatically
 
sequenced
 
on to the ESF buses. Because the reactor was shut down, power to non-ESF buses was lost and two service water pumps and a station air compressor
 
common to both Byron units tripped. Without the service water pumps, Unit 2, which was operating
 
at full power, had no cooling water to many loads, including
 
the main generator
 
auxiliaries, station air compressors, condensate
 
pumps, and condensate
 
booster pumps. Subsequently, Unit 2 was manually tripped.The licensee determined
 
that the SAT that initially
 
tripped underwent
 
a phase-to-ground
 
fault on a Phase B insulator.
 
The failed insulator
 
was located outdoors, about halfway between the SAT and the auxiliary
 
building.
 
After Initiating, the arc continued
 
down the bus bar, Increasing
 
in width until It involved the other two phases. Air and water present in the bus bar duct was heated by the arc and resulted in pressurization
 
of the duct.Chronic water leakage through inadequately
 
caulked Insulator
 
mounting holes and through an improperly
 
compressed
 
gasket caused degradation
 
of the insulator
 
metal inserts and Insulator material between these inserts. Eventually, the bus flashed to ground through the degraded insulator
 
and initiated
 
the transient.
 
PERRY On June 5, 1997, Perry was operating
 
at full power when an automatic
 
reactor scram occurred following
 
a three-phase
 
fault in one of two high-voltage
 
secondary
 
winding termination
 
compartments
 
of the UAT. The fault resulted in the actuation
 
of the auxiliary
 
transformer
 
phase differential
 
relay, a main generator
 
lockout, a main turbine trip, and fast closure of the turbine control valves.At the time of the transient, safety-related
 
electrical
 
loads were being supplied by the in-service
 
startup transformer.
 
The non-safety-related
 
electrical
 
loads supplied by the transformer
 
automatically
 
transferred
 
to the startup transformer
 
except for the bus that was faulted.Operators
 
stabilized
 
the plant without major complication.
 
The licensee determined
 
that the fault had developed
 
as a result of an accumulation
 
of moisture and dust that had entered the termination
 
compartment
 
housing where a 2-Inch-long
 
piece of gasket material was missing from the compartment
 
housing-to-transformer
 
sealing surface.The missing piece of gasket material may have been lost during work performed
 
when
 
K>1 IN 98-36 September
 
18, 1998 replacing
 
the auxiliary
 
transformer
 
following
 
failure of the transformer
 
on May 30, 1996. The cause of that failure was attributed
 
to Inadequate
 
original design or poor assembly practices
 
or both.POINT BEACH UNIT I During a severe storm on January 8, 1998, a ground In the low-voltage-side
 
bus duct caused the failure of the Unit I SAT. This failure and a failure of the 13.8-kilovolt
 
automatic
 
bus transfer to the Unit 2 SAT resulted in the loss of normal power to the Unit I safeguards
 
buses. The EDGs subsequently
 
started and restored power to the buses. Unit I remained at 98 percent power throughout
 
the transient.
 
Unit 2 was in cold shutdown.The licensee attributed
 
the failure of the transformer
 
to the buildup of condensation
 
internal to the buses and long-term
 
insulation
 
degradation
 
In the bus duct on the low-voltage
 
side of the transformer.
 
Before the transformer
 
failed, the circuit breaker for a heater designed to keep the bus duct dry would not remain closed. Consequently, in August 1996, the licensee left the circuit breaker open and wrote a work order for its repair. However, work schedulers
 
did not recognize
 
that the bus duct heater was inoperable
 
with the circuit breaker open, and the work order was erroneously
 
classified
 
as "minor maintenance" and given low priority.
 
At the time the transformer
 
failed, the work order was in the "backlog'
of maintenance
 
Items. In addition to the inoperable
 
heater, the:licensee
 
determined
 
that the lack of a routine inspection
 
program for the bus ducts may have contributed
 
to the event. Inspection
 
of the bus ducts after the transformer
 
failed revealed insulation
 
breakdown
 
that would likely have been Identified
 
through a periodic Inspection
 
program.Discussion
 
These events illustrate
 
the potentially
 
significant
 
consequences
 
of inadequate
 
or poorly performed
 
maintenance
 
activities
 
on non-safety-related
 
plant components.
 
Unnecessary
 
challenges
 
to plant safety systems or control room operators
 
or both could result from inadequate
 
control or inattention
 
to detail during non-safety-related
 
maintenance
 
activities.
 
The potential
 
impact on safety systems of such activities
 
as the re-roofing
 
of nuclear power plant support buildings, the Installation
 
of gaskets, or the caulking of outdoor components, could easily be overlooked.
 
In addition, several of the events discussed
 
here highlight
 
the need for licensees
 
to have better control over the maintenance
 
activities
 
of contractor
 
and non-station
 
utility employees, and the need for thorough periodic walkdowns
 
or preventive
 
maintenance
 
on auxiliary
 
transformers
 
and the associated
 
outdoor bus ducts.
 
IN 98-36 September
 
18, 1998 This information
 
notice requires no specific action or written response.
 
However, recipients
 
are reminded that they are required to consider Industry-wide
 
operating
 
experience (including
 
NRC INs) where practical, when setting goals and performing
 
periodic evaluations
 
under Section 50.65, "Requirements
 
for Monitoring
 
the Effectiveness
 
of Maintenance
 
at Nuclear Power Plants," of Part 50 of Title 10 of the Code of Federal Regulations.
 
If you have any questions about the information
 
In this notice, please contact one of the technical
 
contacts listed below or the appropriate
 
Office of Nuclear Reactor Regulation (NRR) project manager.eJack , Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
contacts:
Mike Kunowski, Region IlIl John Neisler, Region IlIl 630-829-9816
630429-9718 E-mail: mak3@nrc.gov
 
E-mail: jhn@nrc.gov
 
Attachment:
List of Recently Issued NRC Information
 
Notices
 
A,(ttachment
 
1 IN 98-36 September
 
18, 1998 LIST OF RECENTLY ISSUED NRC INFORMATION
 
===NOTICES Information===
Notice No.Date of Issuance Subject 98-35 Threat Assessments
 
and Consideration
 
of Heightened
 
Physical Protection
 
Measures 914/98 Issued to All U.S. NRC fuel cycle facilities
 
power and non-power
 
reactor licensees (Safeguard
 
issues, not for public disclosure.)
98-34 98-33 98-32 98-31 NRC Configuration
 
Control Errors NRC Regulations
 
Prohibit Agreements
 
that restrict or Discourage
 
an Employee from Participating
 
In Protected
 
Activities
 
Problems Associated
 
with Post-Fire Safe-Shutdown
 
Circuit Analyses 8/28/98 8128198 8126198 All holders of Operating
 
licenses for nuclear power reactors, except for those who have ceased operations
 
and have certified
 
that fuel has been permanently
 
removed from the reactor vessel All holders of a U.S. Nuclear Regulatory
 
Commission (NRC)license.All holders of operating
 
licenses for nuclear power reactors, except those who have permanently
 
ceased operations
 
and have certified
 
that fuel has been permanently
 
removed form the reactor All holders of operating
 
licences for nuclear power reactors, except those licensees
 
that have permanently
 
ceased operations
 
and have certified
 
that fuel has been permanently
 
removed from the reactor vessel.Fire Protection
 
System Design 8/26/98 Deficiencies
 
and Common-Mode
 
Flooding of Emergency
 
Core Cooling System Rooms at Washington
 
Nuclear Project Unit 2 OL = Operating
 
License CP = Construction
 
Permit
 
-IN 98-36 September
 
18, 1998 This information
 
notice requires no specific action or written response.
 
However, recipients
 
are reminded that they are required to consider industry-wide
 
operating
 
experience (including
 
NRC INs) where practical, when setting goals and performing
 
periodic evaluations
 
under Section 50.65, "Requirements
 
for Monitoring
 
the Effectiveness
 
of Maintenance
 
at Nuclear Power Plants," of Part 50 of Title 10 of the Code of Federal Regulations.
 
If you have any questions about the information
 
in this notice, please contact one of the technical
 
contacts listed below or the appropriate
 
Office of Nuclear Reactor Regulation (NRR) project manager.Jack W. Roe, Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
contacts:
Mike Kunowski, Region IlIl 630-829-9816 E-mail: mak3@nrc.gov
 
John Neisler, Region IlIl 630-829-9718 E-mail: jhn@nrc.gov
 
Attachment:
List of Recently Issued NRC Information
 
Notices*See previous concurrence
 
C,,tt & e.**E-mail concurrence
 
c<f()DOCUMENT NAME: G:\NICK\REGION.IN
 
To receive a copy of this document, indicate in the box C=Copy wlo attachment/enclosure
 
E=Copy with attachmentlenclosure
 
N = No copy OFFICE PECB I Tech Ed I Reg III Reg [ il I PECB I C:PECB l_ji D M NAME NFields* RSanders*
MKunowski**
JNeisler**
RDennig* JStolz* JRo DATE 09/03/98 08/26/98 09/03/98 Ii09/03/98
09/14/98 J 09/14/98 \/98 OFFICIAL RECORD COPY
 
IN 98-xx September
 
xx, 1998 This information
 
notice requires no specific action or written response.
 
However, recipie are reminded that they are required to consider industry-wide
 
operating
 
experience (includ g NRC INs) where practical, when setting goals and performing
 
periodic evaluations
 
under ection 50.65, "Requirements
 
for Monitoring
 
the Effectiveness
 
of Maintenance
 
at Nuclea ower Plants," of Part 50 of Title 10 of the Code of Federal Regulations.
 
If you have ny questions about the information
 
in this notice, please contact one of the technical
 
con cts listed below or the appropriate
 
Office of Nuclear Reactor Regulation (NRR) project man er.Jack W. Roe, Acting irector Division of Reactor rogram Management
 
===Office of Nuclea eactor Regulation===
Technical
 
contacts:
Mike Kunowski, Region IlIl Joh eisler, Region IlIl 630-829-9816
63 -829-9718 E-mail: mak3@nrc.gov -mail: jhn@nrc.gov
 
Attachment:
List of Recently Issued NRC Info tion Notices DOCUMENT NAME: G:\NICK\REGION.IN
 
To receive a copy of this document, Indicate in the box C=Copy wlo attachmentenclosure
 
E=Copy with attachmentlenclosure
 
N = No copy OFFICE PECB. I _ Tech Ed I _ Reg I _I lI Reg 11 l 1/E "ECB (A)D:DRPM
 
lNAME NFiells' { RSanders MKu owsk Jeisler ennig l l JRoel DATE /3/98 1SW98 17/3/98 15/3198 lH/ 48 q/l98 l I /98 OFFICIAL RECORD COPY I}}


{{Information notice-Nav}}
{{Information notice-Nav}}

Revision as of 14:13, 31 August 2018

Inadequate or Poorly Controlled, Non-Safety-Related Maintenance Activities Unnecessarily Challenged Safety Systems
ML031040558
Person / Time
Site: Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant  Entergy icon.png
Issue date: 09/18/1998
From: Roe J W
Office of Nuclear Reactor Regulation
To:
References
IN-98-036, NUDOCS 9809210079
Download: ML031040558 (7)
v • d • e


~0- f 9 Acre UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 September

18, 1998 NRC INFORMATION

NOTICE 98-36: INADEQUATE

OR POORLY CONTROLLED, NON-SAFETY-RELATED

MAINTENANCE

ACTIVITIES

UNNECESSARILY

CHALLENGED

SAFETY SYSTEMS Addressee All holders of operating

licenses for nuclear power reactors.purpose The U.S. Nuclear Regulatory

Commission (NRC) is issuing this information

notice (IN) to alert addressees

to several recent events in which inadequate

or poorly controlled, non-safety- related maintenance

activities

resulted in unnecessary

challenges

to safety systems. It is expected that recipients

will review the information

for applicability

to their facilities

and consider action, as appropriate

to avoid similar problems.

However, suggestions

contained

in this information

notice are not NRC requirements;

therefore, no specific action or written response is required.Description

of Circumstances

BRAIDWOOD

UNIT 2 On January 18, 1996, with Braidwood

Unit 2 operating

at full power, .offsite power was lost.Inadequately

secured roofing repair materials

located on the roof of the adjacent service building were blown off the roof during a rain storm, causing a phase-to-ground

arc on one of two station auxiliary

transformers (SATs). As designed, the second SAT tripped when the first SAT failed. Both emergency

diesel generators (EDGs) automatically

started and all safe-shutdown loads automatically

sequenced

on to the engineered

safety feature (ESF) buses. All automatic

bus transfers

occurred as designed, maintaining

power to non-ESF buses from the unit auxiliary

transformers (UATs). The reactor remained stable at full power throughout

the event. To restore offsite power to Unit 2, the licensee cross-tied

both Unit 2 ESF buses to the respective

ESF buses of Unit 1, which also remained at full power throughout

the event.Inspection

of the faulted SAT revealed damage to (1) the Phase B and C bushings and (2) a gas detector relay on top of the transformer

where heavy arcing occurred.

The licensee determined

that the Initiating

event was a Phase C arc-to-ground, followed by a Phase B to vNOrT g NO -98T- goz 98 0e 8<9809 td n

f IN 98-36 September

18, 1998 Phase C arc. A 345-kilovolt

switchyard

breaker, Which connected

the SAT to the switchyard

ring bus, was also damaged. Approximately

one square foot of the Phase B bushing was blown out.BYRON UNIT I On May 23, 1996, with the Unit 1 reactor shut down In excess of a month for a refueling

outage, offsite power was lost when one of the two Unit I SATs Isolated because of a Phase A to Phase B current differential

relay operation.

The second SAT tripped as designed when the first SAT failed. Both EDGs automatically

started and all safe-shutdown

loads automatically

sequenced

on to the ESF buses. Because the reactor was shut down, power to non-ESF buses was lost and two service water pumps and a station air compressor

common to both Byron units tripped. Without the service water pumps, Unit 2, which was operating

at full power, had no cooling water to many loads, including

the main generator

auxiliaries, station air compressors, condensate

pumps, and condensate

booster pumps. Subsequently, Unit 2 was manually tripped.The licensee determined

that the SAT that initially

tripped underwent

a phase-to-ground

fault on a Phase B insulator.

The failed insulator

was located outdoors, about halfway between the SAT and the auxiliary

building.

After Initiating, the arc continued

down the bus bar, Increasing

in width until It involved the other two phases. Air and water present in the bus bar duct was heated by the arc and resulted in pressurization

of the duct.Chronic water leakage through inadequately

caulked Insulator

mounting holes and through an improperly

compressed

gasket caused degradation

of the insulator

metal inserts and Insulator material between these inserts. Eventually, the bus flashed to ground through the degraded insulator

and initiated

the transient.

PERRY On June 5, 1997, Perry was operating

at full power when an automatic reactor scram occurred following

a three-phase

fault in one of two high-voltage

secondary

winding termination

compartments

of the UAT. The fault resulted in the actuation

of the auxiliary

transformer

phase differential

relay, a main generator

lockout, a main turbine trip, and fast closure of the turbine control valves.At the time of the transient, safety-related

electrical

loads were being supplied by the in-service

startup transformer.

The non-safety-related

electrical

loads supplied by the transformer

automatically

transferred

to the startup transformer

except for the bus that was faulted.Operators

stabilized

the plant without major complication.

The licensee determined

that the fault had developed

as a result of an accumulation

of moisture and dust that had entered the termination

compartment

housing where a 2-Inch-long

piece of gasket material was missing from the compartment

housing-to-transformer

sealing surface.The missing piece of gasket material may have been lost during work performed

when

K>1 IN 98-36 September

18, 1998 replacing

the auxiliary

transformer

following

failure of the transformer

on May 30, 1996. The cause of that failure was attributed

to Inadequate

original design or poor assembly practices

or both.POINT BEACH UNIT I During a severe storm on January 8, 1998, a ground In the low-voltage-side

bus duct caused the failure of the Unit I SAT. This failure and a failure of the 13.8-kilovolt

automatic

bus transfer to the Unit 2 SAT resulted in the loss of normal power to the Unit I safeguards

buses. The EDGs subsequently

started and restored power to the buses. Unit I remained at 98 percent power throughout

the transient.

Unit 2 was in cold shutdown.The licensee attributed

the failure of the transformer

to the buildup of condensation

internal to the buses and long-term

insulation

degradation

In the bus duct on the low-voltage

side of the transformer.

Before the transformer

failed, the circuit breaker for a heater designed to keep the bus duct dry would not remain closed. Consequently, in August 1996, the licensee left the circuit breaker open and wrote a work order for its repair. However, work schedulers

did not recognize

that the bus duct heater was inoperable

with the circuit breaker open, and the work order was erroneously

classified

as "minor maintenance" and given low priority.

At the time the transformer

failed, the work order was in the "backlog'

of maintenance

Items. In addition to the inoperable

heater, the:licensee

determined

that the lack of a routine inspection

program for the bus ducts may have contributed

to the event. Inspection

of the bus ducts after the transformer

failed revealed insulation

breakdown

that would likely have been Identified

through a periodic Inspection

program.Discussion

These events illustrate

the potentially

significant

consequences

of inadequate

or poorly performed

maintenance

activities

on non-safety-related

plant components.

Unnecessary

challenges

to plant safety systems or control room operators

or both could result from inadequate

control or inattention

to detail during non-safety-related

maintenance

activities.

The potential

impact on safety systems of such activities

as the re-roofing

of nuclear power plant support buildings, the Installation

of gaskets, or the caulking of outdoor components, could easily be overlooked.

In addition, several of the events discussed

here highlight

the need for licensees

to have better control over the maintenance

activities

of contractor

and non-station

utility employees, and the need for thorough periodic walkdowns

or preventive

maintenance

on auxiliary

transformers

and the associated

outdoor bus ducts.

IN 98-36 September

18, 1998 This information

notice requires no specific action or written response.

However, recipients

are reminded that they are required to consider Industry-wide

operating

experience (including

NRC INs) where practical, when setting goals and performing

periodic evaluations

under Section 50.65, "Requirements

for Monitoring

the Effectiveness

of Maintenance

at Nuclear Power Plants," of Part 50 of Title 10 of the Code of Federal Regulations.

If you have any questions about the information

In this notice, please contact one of the technical

contacts listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project manager.eJack , Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

contacts:

Mike Kunowski, Region IlIl John Neisler, Region IlIl 630-829-9816

630429-9718 E-mail: mak3@nrc.gov

E-mail: jhn@nrc.gov

Attachment:

List of Recently Issued NRC Information

Notices

A,(ttachment

1 IN 98-36 September

18, 1998 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Notice No.Date of Issuance Subject 98-35 Threat Assessments

and Consideration

of Heightened

Physical Protection

Measures 914/98 Issued to All U.S. NRC fuel cycle facilities

power and non-power

reactor licensees (Safeguard

issues, not for public disclosure.)

98-34 98-33 98-32 98-31 NRC Configuration

Control Errors NRC Regulations

Prohibit Agreements

that restrict or Discourage

an Employee from Participating

In Protected

Activities

Problems Associated

with Post-Fire Safe-Shutdown

Circuit Analyses 8/28/98 8128198 8126198 All holders of Operating

licenses for nuclear power reactors, except for those who have ceased operations

and have certified

that fuel has been permanently

removed from the reactor vessel All holders of a U.S. Nuclear Regulatory

Commission (NRC)license.All holders of operating

licenses for nuclear power reactors, except those who have permanently

ceased operations

and have certified

that fuel has been permanently

removed form the reactor All holders of operating

licences for nuclear power reactors, except those licensees

that have permanently

ceased operations

and have certified

that fuel has been permanently

removed from the reactor vessel.Fire Protection

System Design 8/26/98 Deficiencies

and Common-Mode

Flooding of Emergency

Core Cooling System Rooms at Washington

Nuclear Project Unit 2 OL = Operating

License CP = Construction

Permit

-IN 98-36 September

18, 1998 This information

notice requires no specific action or written response.

However, recipients

are reminded that they are required to consider industry-wide

operating

experience (including

NRC INs) where practical, when setting goals and performing

periodic evaluations

under Section 50.65, "Requirements

for Monitoring

the Effectiveness

of Maintenance

at Nuclear Power Plants," of Part 50 of Title 10 of the Code of Federal Regulations.

If you have any questions about the information

in this notice, please contact one of the technical

contacts listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project manager.Jack W. Roe, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

contacts:

Mike Kunowski, Region IlIl 630-829-9816 E-mail: mak3@nrc.gov

John Neisler, Region IlIl 630-829-9718 E-mail: jhn@nrc.gov

Attachment:

List of Recently Issued NRC Information

Notices*See previous concurrence

C,,tt & e.**E-mail concurrence

c<f()DOCUMENT NAME: G:\NICK\REGION.IN

To receive a copy of this document, indicate in the box C=Copy wlo attachment/enclosure

E=Copy with attachmentlenclosure

N = No copy OFFICE PECB I Tech Ed I Reg III Reg [ il I PECB I C:PECB l_ji D M NAME NFields* RSanders*

MKunowski**

JNeisler**

RDennig* JStolz* JRo DATE 09/03/98 08/26/98 09/03/98 Ii09/03/98

09/14/98 J 09/14/98 \/98 OFFICIAL RECORD COPY

IN 98-xx September

xx, 1998 This information

notice requires no specific action or written response.

However, recipie are reminded that they are required to consider industry-wide

operating

experience (includ g NRC INs) where practical, when setting goals and performing

periodic evaluations

under ection 50.65, "Requirements

for Monitoring

the Effectiveness

of Maintenance

at Nuclea ower Plants," of Part 50 of Title 10 of the Code of Federal Regulations.

If you have ny questions about the information

in this notice, please contact one of the technical

con cts listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project man er.Jack W. Roe, Acting irector Division of Reactor rogram Management

Office of Nuclea eactor Regulation

Technical

contacts:

Mike Kunowski, Region IlIl Joh eisler, Region IlIl 630-829-9816

63 -829-9718 E-mail: mak3@nrc.gov -mail: jhn@nrc.gov

Attachment:

List of Recently Issued NRC Info tion Notices DOCUMENT NAME: G:\NICK\REGION.IN

To receive a copy of this document, Indicate in the box C=Copy wlo attachmentenclosure

E=Copy with attachmentlenclosure

N = No copy OFFICE PECB. I _ Tech Ed I _ Reg I _I lI Reg 11 l 1/E "ECB (A)D:DRPM

lNAME NFiells' { RSanders MKu owsk Jeisler ennig l l JRoel DATE /3/98 1SW98 17/3/98 15/3198 lH/ 48 q/l98 l I /98 OFFICIAL RECORD COPY I


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