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- f 9 Acre UNITED STATES NUCLEAR REGULATORY
{{#Wiki_filter:Acre


COMMISSION
~0-        f9 UNITED STATES


===OFFICE OF NUCLEAR REACTOR REGULATION===
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 20555-0001 September


18, 1998 NRC INFORMATION
OFFICE OF NUCLEAR REACTOR REGULATION


NOTICE 98-36: INADEQUATE
WASHINGTON, D.C. 20555-0001 September 18, 1998 NRC INFORMATION NOTICE 98-36: INADEQUATE OR POORLY CONTROLLED, NON-
                                          SAFETY-RELATED MAINTENANCE ACTIVITIES


OR POORLY CONTROLLED, NON-SAFETY-RELATED
UNNECESSARILY CHALLENGED SAFETY SYSTEMS


MAINTENANCE
Addressee


ACTIVITIES
All holders of operating licenses for nuclear power reactors.


UNNECESSARILY
purpose


CHALLENGED
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to alert


SAFETY SYSTEMS Addressee All holders of operating
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


licenses for nuclear power reactors.purpose The U.S. Nuclear Regulatory
expected that recipients will review the information for applicability to their facilities and consider


Commission (NRC) is issuing this information
action, as appropriate to avoid similar problems. However, suggestions contained in this


notice (IN) to alert addressees
information notice are not NRC requirements; therefore, no specific action or written response


to several recent events in which inadequate
is required.


or poorly controlled, non-safety- related maintenance
==Description of Circumstances==


activities
===BRAIDWOOD UNIT 2===
On January 18, 1996, with Braidwood Unit 2 operating at full power, .offsite power was lost.


resulted in unnecessary
Inadequately secured roofing repair materials located on the roof of the adjacent service


challenges
building were blown off the roof during a rain storm, causing a phase-to-ground arc on one of


to safety systems. It is expected that recipients
two station auxiliary transformers (SATs). As designed, the second SAT tripped when the first


will review the information
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


for applicability
automatic bus transfers occurred as designed, maintaining power to non-ESF buses from the


to their facilities
unit auxiliary transformers (UATs). The reactor remained stable at full power throughout the


and consider action, as appropriate
event. To restore offsite power to Unit 2, the licensee cross-tied both Unit 2 ESF buses to the


to avoid similar problems.
respective ESF buses of Unit 1, which also remained at full power throughout the event.


However, suggestions
Inspection of the faulted SAT revealed damage to (1) the Phase B and C bushings and (2) a


contained
gas detector relay on top of the transformer where heavy arcing occurred. The licensee


in this information
determined that the Initiating event was a Phase C arc-to-ground, followed by a Phase B to


notice are not NRC requirements;
vNOrT    g          NO        -98T-  goz 98 0e 8
therefore, no specific action or written response is required.Description
<9809            td        n


of Circumstances
f IN 98-36 September 18, 1998 Phase C arc. A 345-kilovolt switchyard breaker, Which connected the SAT to the switchyard


BRAIDWOOD
ring bus, was also damaged. Approximately one square foot of the Phase B bushing was


UNIT 2 On January 18, 1996, with Braidwood
blown out.


Unit 2 operating
===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


at full power, .offsite power was lost.Inadequately
Phase B current differential relay operation. The second SAT tripped as designed when the


secured roofing repair materials
first SAT failed. Both EDGs automatically started and all safe-shutdown loads automatically


located on the roof of the adjacent service building were blown off the roof during a rain storm, causing a phase-to-ground
sequenced on to the ESF buses. Because the reactor was shut down, power to non-ESF


arc on one of two station auxiliary
buses was lost and two service water pumps and a station air compressor common to both


transformers (SATs). As designed, the second SAT tripped when the first SAT failed. Both emergency
Byron units tripped. Without the service water pumps, Unit 2, which was operating at full


diesel generators (EDGs) automatically
power, had no cooling water to many loads, including the main generator auxiliaries, station air


started and all safe-shutdown loads automatically
compressors, condensate pumps, and condensate booster pumps. Subsequently, Unit 2 was


sequenced
manually tripped.


on to the engineered
The licensee determined that the SAT that initially tripped underwent a phase-to-ground fault on


safety feature (ESF) buses. All automatic
a Phase B insulator. The failed insulator was located outdoors, about halfway between the SAT


bus transfers
and the auxiliary building. After Initiating, the arc continued down the bus bar, Increasing in


occurred as designed, maintaining
width until It involved the other two phases. Air and water present in the bus bar duct was


power to non-ESF buses from the unit auxiliary
heated by the arc and resulted in pressurization of the duct.


transformers (UATs). The reactor remained stable at full power throughout
Chronic water leakage through inadequately caulked Insulator mounting holes and through an


the event. To restore offsite power to Unit 2, the licensee cross-tied
improperly compressed gasket caused degradation of the insulator metal inserts and Insulator


both Unit 2 ESF buses to the respective
material between these inserts. Eventually, the bus flashed to ground through the degraded


ESF buses of Unit 1, which also remained at full power throughout
insulator and initiated the transient.


the event.Inspection
PERRY


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
On June 5, 1997, Perry was operating at full power when an automatic reactor scram occurred


where heavy arcing occurred.
following a three-phase fault in one of two high-voltage secondary winding termination


The licensee determined
compartments of the UAT. The fault resulted in the actuation of the auxiliary transformer phase


that the Initiating
differential relay, a main generator lockout, a main turbine trip, and fast closure of the turbine


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
control valves.


f IN 98-36 September
At the time of the transient, safety-related electrical loads were being supplied by the in-service


18, 1998 Phase C arc. A 345-kilovolt
startup transformer. The non-safety-related electrical loads supplied by the transformer


switchyard
automatically transferred to the startup transformer except for the bus that was faulted.


breaker, Which connected
Operators stabilized the plant without major complication.


the SAT to the switchyard
The licensee determined that the fault had developed as a result of an accumulation of moisture


ring bus, was also damaged. Approximately
and dust that had entered the termination compartment housing where a 2-Inch-long piece of


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
gasket material was missing from the compartment housing-to-transformer sealing surface.


outage, offsite power was lost when one of the two Unit I SATs Isolated because of a Phase A to Phase B current differential
The missing piece of gasket material may have been lost during work performed when


relay operation.
K>1 IN 98-36 September 18, 1998 replacing the auxiliary transformer following failure of the transformer on May 30, 1996. The


The second SAT tripped as designed when the first SAT failed. Both EDGs automatically
cause of that failure was attributed to Inadequate original design or poor assembly practices or


started and all safe-shutdown
both.


loads automatically
===POINT BEACH UNIT I===
During a severe storm on January 8, 1998, a ground In the low-voltage-side bus duct caused


sequenced
the failure of the Unit I SAT. This failure and a failure of the 13.8-kilovolt automatic bus transfer


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
to the Unit 2 SAT resulted in the loss of normal power to the Unit I safeguards buses. The


common to both Byron units tripped. Without the service water pumps, Unit 2, which was operating
EDGs subsequently started and restored power to the buses. Unit I remained at 98 percent


at full power, had no cooling water to many loads, including
power throughout the transient. Unit 2 was in cold shutdown.


the main generator
The licensee attributed the failure of the transformer to the buildup of condensation internal to


auxiliaries, station air compressors, condensate
the buses and long-term insulation degradation In the bus duct on the low-voltage side of the


pumps, and condensate
transformer. Before the transformer failed, the circuit breaker for a heater designed to keep the


booster pumps. Subsequently, Unit 2 was manually tripped.The licensee determined
bus duct dry would not remain closed. Consequently, in August 1996, the licensee left the


that the SAT that initially
circuit breaker open and wrote a work order for its repair. However, work schedulers did not


tripped underwent
recognize that the bus duct heater was inoperable with the circuit breaker open, and the work


a phase-to-ground
order was erroneously classified as "minor maintenance" and given low priority. At the time the


fault on a Phase B insulator.
transformer failed, the work order was in the "backlog' of maintenance Items. In addition to the


The failed insulator
inoperable heater, the:licensee determined that the lack of a routine inspection program for the


was located outdoors, about halfway between the SAT and the auxiliary
bus ducts may have contributed to the event. Inspection of the bus ducts after the transformer


building.
failed revealed insulation breakdown that would likely have been Identified through a periodic


After Initiating, the arc continued
Inspection program.


down the bus bar, Increasing
Discussion


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
These events illustrate the potentially significant consequences of inadequate or poorly


of the duct.Chronic water leakage through inadequately
performed maintenance activities on non-safety-related plant components. Unnecessary


caulked Insulator
challenges to plant safety systems or control room operators or both could result from


mounting holes and through an improperly
inadequate control or inattention to detail during non-safety-related maintenance activities. The


compressed
potential impact on safety systems of such activities as the re-roofing of nuclear power plant


gasket caused degradation
support buildings, the Installation of gaskets, or the caulking of outdoor components, could


of the insulator
easily be overlooked. In addition, several of the events discussed here highlight the need for


metal inserts and Insulator material between these inserts. Eventually, the bus flashed to ground through the degraded insulator
licensees to have better control over the maintenance activities of contractor and non-station


and initiated
utility employees, and the need for thorough periodic walkdowns or preventive maintenance on


the transient.
auxiliary transformers and the associated outdoor bus ducts.


PERRY On June 5, 1997, Perry was operating
IN 98-36 September 18, 1998 This information notice requires no specific action or written response. However, recipients are


at full power when an automatic
reminded that they are required to consider Industry-wide operating experience (including NRC


reactor scram occurred following
INs) where practical, when setting goals and performing periodic evaluations under Section


a three-phase
50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power


fault in one of two high-voltage
Plants," of Part 50 of Title 10 of the Code of Federal Regulations. If you have any questions


secondary
about the information Inthis notice, please contact one of the technical contacts listed below or


winding termination
the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.


compartments
, Acting Director


of the UAT. The fault resulted in the actuation
eJack


of the auxiliary
Division of Reactor Program Management


transformer
Office of Nuclear Reactor Regulation


phase differential
Technical contacts: Mike Kunowski, Region IlIl        John Neisler, Region IlIl


relay, a main generator
630-829-9816                      630429-9718 E-mail: mak3@nrc.gov              E-mail: jhn@nrc.gov


lockout, a main turbine trip, and fast closure of the turbine control valves.At the time of the transient, safety-related
Attachment: List of Recently Issued NRC Information Notices


electrical
A,(ttachment 1 IN 98-36 September 18, 1998 LIST OF RECENTLY ISSUED


loads were being supplied by the in-service
NRC INFORMATION NOTICES


startup transformer.
Information                                            Date of


The non-safety-related
Notice No.            Subject                          Issuance Issued to


electrical
98-35            Threat Assessments and                914/98  All U.S. NRC fuel cycle facilities


loads supplied by the transformer
Consideration of Heightened                    power and non-power reactor


automatically
Physical Protection Measures                  licensees (Safeguard issues, not


transferred
for public disclosure.)
98-34            NRC Configuration Control            8/28/98  All holders of Operating licenses


to the startup transformer
Errors                                        for nuclear power reactors, except


except for the bus that was faulted.Operators
for those who have ceased


stabilized
operations and have certified that


the plant without major complication.
fuel has been permanently


The licensee determined
removed from the reactor vessel


that the fault had developed
98-33            NRC Regulations Prohibit              8128198  All holders of a U.S. Nuclear


as a result of an accumulation
Agreements that restrict or                    Regulatory Commission (NRC)
                  Discourage an Employee from                    license.


of moisture and dust that had entered the termination
Participating In Protected Activities


compartment
98-32            Problems Associated with Post-        8126198  All holders of operating licenses


housing where a 2-Inch-long
Fire Safe-Shutdown Circuit                    for nuclear power reactors, except


piece of gasket material was missing from the compartment
Analyses                                      those who have permanently


housing-to-transformer
ceased operations and have


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


when
permanently removed form the


K>1 IN 98-36 September
reactor


18, 1998 replacing
98-31            Fire Protection System Design        8/26/98  All holders of operating licences


the auxiliary
Deficiencies and Common-Mode                  for nuclear power reactors, except


transformer
Flooding of Emergency Core Cooling            those licensees that have


following
System Rooms at Washington Nuclear              permanently ceased operations


failure of the transformer
Project Unit 2                                and have certified that fuel has


on May 30, 1996. The cause of that failure was attributed
been permanently removed from


to Inadequate
the reactor vessel.


original design or poor assembly practices
OL = Operating License


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


bus duct caused the failure of the Unit I SAT. This failure and a failure of the 13.8-kilovolt
-    IN 98-36 September 18, 1998 This information notice requires no specific action or written response. However, recipients are


automatic
reminded that they are required to consider industry-wide operating experience (including NRC


bus transfer to the Unit 2 SAT resulted in the loss of normal power to the Unit I safeguards
INs) where practical, when setting goals and performing periodic evaluations under Section


buses. The EDGs subsequently
50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power


started and restored power to the buses. Unit I remained at 98 percent power throughout
Plants," of Part 50 of Title 10 of the Code of Federal Regulations. If you have any questions


the transient.
about the information in this notice, please contact one of the technical contacts listed below or


Unit 2 was in cold shutdown.The licensee attributed
the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.


the failure of the transformer
Jack W. Roe, Acting Director


to the buildup of condensation
Division of Reactor Program Management


internal to the buses and long-term
Office of Nuclear Reactor Regulation


insulation
Technical contacts: Mike Kunowski, Region IlIl                  John Neisler, Region IlIl


degradation
630-829-9816                          630-829-9718 E-mail: mak3@nrc.gov                  E-mail: jhn@nrc.gov


In the bus duct on the low-voltage
Attachment: List of Recently Issued NRC Information Notices


side of the transformer.
*See previous concurrence                                                                        & e.


Before the transformer
C,,tt


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
**E-mail concurrence                                                                                    c<f()
            DOCUMENT NAME: G:\NICK\REGION.IN


did not recognize
To receive a copy of this document, indicate in the box C=Copy wlo attachment/enclosure E=Copy with attachmentlenclosure N = No copy


that the bus duct heater was inoperable
OFFICE        PECB I          Tech EdI            Reg    III        [  Regil    I    PECB I        C:PECB l_ji          D    M


with the circuit breaker open, and the work order was erroneously
NAME          NFields*        RSanders*          MKunowski**          JNeisler**    RDennig*      JStolz*          JRo


classified
DATE          09/03/98        08/26/98            09/03/98            Ii09/03/98 09/14/98          J09/14/98        \/98 OFFICIAL RECORD COPY


as "minor maintenance" and given low priority.
IN 98-xx


At the time the transformer
September xx, 1998 This information notice requires no specific action or written response. However, recipie                  are


failed, the work order was in the "backlog'
reminded that they are required to consider industry-wide operating experience (includ g NRC
of maintenance


Items. In addition to the inoperable
INs) where practical, when setting goals and performing periodic evaluations under ection


heater, the:licensee
50.65, "Requirements for Monitoring the Effectiveness of Maintenance at Nuclea ower


determined
Plants," of Part 50 of Title 10 of the Code of Federal Regulations. If you have ny questions


that the lack of a routine inspection
about the information in this notice, please contact one of the technical con cts listed below or


program for the bus ducts may have contributed
the appropriate Office of Nuclear Reactor Regulation (NRR) project man er.


to the event. Inspection
Jack W. Roe, Acting irector


of the bus ducts after the transformer
Division of Reactor rogram Management


failed revealed insulation
Office of Nuclea eactor Regulation


breakdown
Technical contacts: Mike Kunowski, Region IlIl                  Joh    eisler, Region IlIl


that would likely have been Identified
630-829-9816                          63 -829-9718 E-mail: mak3@nrc.gov                    -mail: jhn@nrc.gov


through a periodic Inspection
Attachment: List of Recently Issued NRC Info                tion Notices


program.Discussion
DOCUMENT NAME: G:\NICK\REGION.IN


These events illustrate
To receive a copy of this document, Indicate in the box C=Copy wlo attachmentenclosure E=Copy with attachmentlenclosure N = No copy


the potentially
OFFICE        PECB. I _ Tech Ed I _ Reg I                  lI _I Reg 11 l            1/E    "ECB            (A)D:DRPM l


significant
NAME          NFiells'      { RSanders            MKu    owsk      Jeisler          ennig l                l JRoe


consequences
l DATE           /3/98       1SW98               17/3/98         15/3198       lH/   48     q/l98           l I /98 OFFICIAL RECORD COPY                       I}}
 
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}}

Latest revision as of 04:48, 24 November 2019

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
Office of Nuclear Reactor Regulation
To:
References
IN-98-036, NUDOCS 9809210079
Download: ML031040558 (7)
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~0- f9 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 Inthis notice, please contact one of the technical contacts listed below or

the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

, Acting Director

eJack

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 Date of

Notice No. Subject Issuance Issued to

98-35 Threat Assessments and 914/98 All U.S. NRC fuel cycle facilities

Consideration of Heightened power and non-power reactor

Physical Protection Measures licensees (Safeguard issues, not

for public disclosure.)

98-34 NRC Configuration Control 8/28/98 All holders of Operating licenses

Errors for nuclear power reactors, except

for those who have ceased

operations and have certified that

fuel has been permanently

removed from the reactor vessel

98-33 NRC Regulations Prohibit 8128198 All holders of a U.S. Nuclear

Agreements that restrict or Regulatory Commission (NRC)

Discourage an Employee from license.

Participating In Protected Activities

98-32 Problems Associated with Post- 8126198 All holders of operating licenses

Fire Safe-Shutdown Circuit for nuclear power reactors, except

Analyses those who have permanently

ceased operations and have

certified that fuel has been

permanently removed form the

reactor

98-31 Fire Protection System Design 8/26/98 All holders of operating licences

Deficiencies and Common-Mode for nuclear power reactors, except

Flooding of Emergency Core Cooling those licensees that have

System Rooms at Washington Nuclear permanently ceased operations

Project Unit 2 and have certified that fuel has

been permanently removed from

the reactor vessel.

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 John Neisler, Region IlIl

630-829-9816 630-829-9718 E-mail: mak3@nrc.gov E-mail: jhn@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

  • See previous concurrence & e.

C,,tt

    • 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 EdI Reg III [ Regil 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 J09/14/98 \/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 lI _I Reg 11 l 1/E "ECB (A)D:DRPM l

NAME NFiells' { RSanders MKu owsk Jeisler ennig l l JRoe

l DATE /3/98 1SW98 17/3/98 15/3198 lH/ 48 q/l98 l I /98 OFFICIAL RECORD COPY I


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