Information Notice 2016-07, Operating Experience Regarding Impacts on Site Electrical Power Distribution from Inadequate Oversight of Contractor Activities: Difference between revisions

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{{#Wiki_filter:UNITED STATES
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UNITED STATES


NUCLEAR REGULATORY COMMISSION
NUCLEAR REGULATORY COMMISSION
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OFFICE OF NEW REACTORS
OFFICE OF NEW REACTORS


WASHINGTON, DC 20555-0001 June 20, 2016 NRC INFORMATION NOTICE 2016-07:                   OPERATING EXPERIENCE REGARDING
WASHINGTON, DC 20555-0001  
 
June 20, 2016  
 
NRC INFORMATION NOTICE 2016-07:  
OPERATING EXPERIENCE REGARDING


IMPACTS ON SITE ELECTRICAL POWER
IMPACTS ON SITE ELECTRICAL POWER
Line 46: Line 53:
addressees of adverse effects to off-site power availability that have resulted from inadequate
addressees of adverse effects to off-site power availability that have resulted from inadequate


licensee oversight of contractor activities. It is expected that recipients will review the
licensee oversight of contractor activities. It is expected that recipients will review the


information for applicability to their facilities and consider actions, as appropriate, to avoid
information for applicability to their facilities and consider actions, as appropriate, to avoid


similar problems. However, suggestions contained in this IN are not NRC requirements;
similar problems. However, suggestions contained in this IN are not NRC requirements;  
therefore, no specific action or written response is required.
therefore, no specific action or written response is required.


==DESCRIPTION OF CIRCUMSTANCES==
==DESCRIPTION OF CIRCUMSTANCES==
Wolf Creek Generating Station, Unit 1


===Wolf Creek Generating Station, Unit 1===
On January 13, 2012, Wolf Creek Generating Station (Wolf Creek) experienced an automatic
On January 13, 2012, Wolf Creek Generating Station (Wolf Creek) experienced an automatic


reactor trip after the catastrophic failure of the main generator output breaker. The start-up
reactor trip after the catastrophic failure of the main generator output breaker. The start-up


transformer assumed nonsafety-related loads, but subsequently experienced a differential relay
transformer assumed nonsafety-related loads, but subsequently experienced a differential relay


actuation on its B phase. This caused a lockout of the start-up transformer and a loss of
actuation on its B phase. This caused a lockout of the start-up transformer and a loss of


off-site power (LOOP). Both emergency diesel generators started and supplied power to the
off-site power (LOOP). Both emergency diesel generators started and supplied power to the


safety-related 4160 volt busses as expected.
safety-related 4160 volt busses as expected.


The LOOP resulted in several complications, including:
The LOOP resulted in several complications, including:  
*        erratic source range nuclear instrumentation indications resulting from the loss of power


to containment cavity cooling fans
*
erratic source range nuclear instrumentation indications resulting from the loss of power


ML16057A842 *         containment sump high level alarms caused by a through-wall leak in essential service
to containment cavity cooling fans *  
containment sump high level alarms caused by a through-wall leak in essential service


water (ESW) piping in containment resulting from a known issue with water hammer
water (ESW) piping in containment resulting from a known issue with water hammer
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caused by the stop-start sequence of ESW pumps following a LOOP
caused by the stop-start sequence of ESW pumps following a LOOP


*         a loss of firefighting capability for 4 hours because of the loss of power to normal fire
*  
a loss of firefighting capability for 4 hours because of the loss of power to normal fire


pumps in conjunction with the long-term inoperability of the installed diesel-powered fire
pumps in conjunction with the long-term inoperability of the installed diesel-powered fire
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pump and inadequacies with the procedure for starting a temporary fire pump
pump and inadequacies with the procedure for starting a temporary fire pump


*         a loss of reactor coolant pumps necessitating a natural circulation cooldown, and
*  
a loss of reactor coolant pumps necessitating a natural circulation cooldown, and


*         a loss of instrument air complicating operator control of pressurizer level and pressure
*  
a loss of instrument air complicating operator control of pressurizer level and pressure


The cause of the LOOP was the actuation of protective relaying resulting from a short between
The cause of the LOOP was the actuation of protective relaying resulting from a short between


two taps on the high side current transformers. During the previous year, the licensee had
two taps on the high side current transformers. During the previous year, the licensee had


contracted with a vendor to replace electrical seal assemblies in the start-up transformer that
contracted with a vendor to replace electrical seal assemblies in the start-up transformer that


experienced oil leakage. This vendor performed the majority of the work in accordance with
experienced oil leakage. This vendor performed the majority of the work in accordance with


established instructions and practices, but failed to install insulating sleeves on 2 of the 37 wiring connections. These sleeves are required to prevent terminal-to-terminal contact. The
established instructions and practices, but failed to install insulating sleeves on 2 of the 37 wiring connections. These sleeves are required to prevent terminal-to-terminal contact. The


investigation that followed determined that the licensee failed to satisfy the requirements of
investigation that followed determined that the licensee failed to satisfy the requirements of
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verification of contracted work was conducted to verify that it was performed in accordance with
verification of contracted work was conducted to verify that it was performed in accordance with


applicable work orders. After the event, the licensee installed the missing insulation sleeves, and updated station procedures regarding the oversight of contractors performing work on
applicable work orders. After the event, the licensee installed the missing insulation sleeves, and updated station procedures regarding the oversight of contractors performing work on


risk-significant components.
risk-significant components.


This IN provides no new information on this event. The condition described was summarized
This IN provides no new information on this event. The condition described was summarized


from previously-released reports prepared by an NRC Augmented Inspection Team (AIT)
from previously-released reports prepared by an NRC Augmented Inspection Team (AIT)  
chartered shortly after the event in 2012 to review the facts surrounding the LOOP, and the
chartered shortly after the event in 2012 to review the facts surrounding the LOOP, and the


complications that resulted. Additional information can be found in Licensee Event Report
complications that resulted. Additional information can be found in Licensee Event Report


05000482/2012-001, Failure of 345 kV Switchyard Breaker due to Internal Fault Resulting in
05000482/2012-001, Failure of 345 kV Switchyard Breaker due to Internal Fault Resulting in
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System (ADAMS) Accession Nos. ML12109A049, ML12095A414, and ML12227A919, respectively).
System (ADAMS) Accession Nos. ML12109A049, ML12095A414, and ML12227A919, respectively).


===Arkansas Nuclear One, Unit 1 and Unit 2===
Arkansas Nuclear One, Unit 1 and Unit 2  
 
On March 31, 2013, at Arkansas Nuclear One (ANO) during its Unit 1 outage, an inadequately
On March 31, 2013, at Arkansas Nuclear One (ANO) during its Unit 1 outage, an inadequately


designed temporary lifting rig failed while moving the Unit 1 main generator stator out of the
designed temporary lifting rig failed while moving the Unit 1 main generator stator out of the


turbine building. The 525-ton stator fell onto the turbine deck and then continued falling
turbine building. The 525-ton stator fell onto the turbine deck and then continued falling


approximately 30 feet into a train bay that is shared between Units 1 and 2. The collapse of the
approximately 30 feet into a train bay that is shared between Units 1 and 2. The collapse of the


lifting rig resulted in one fatality and injured eight others. The impact of the dropped stator on
lifting rig resulted in one fatality and injured eight others. The impact of the dropped stator on


the turbine deck damaged the Unit 1 non-vital electrical switchgear connecting plant vital busses
the turbine deck damaged the Unit 1 non-vital electrical switchgear connecting plant vital busses
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to off-site power, causing a LOOP to Unit 1 for six days.
to off-site power, causing a LOOP to Unit 1 for six days.


At the time of the event, Unit 2 was operating at 100 percent power. Vibrations from the stator
At the time of the event, Unit 2 was operating at 100 percent power. Vibrations from the stator


drop and temporary lift rig collapse caused a Unit 2 reactor coolant pump breaker to trip, resulting in an automatic reactor trip of Unit 2. Water spray from a ruptured fire water pipe migrated into the ANO-2 non-vital switchgear area located just off the train bay causing an
drop and temporary lift rig collapse caused a Unit 2 reactor coolant pump breaker to trip, resulting in an automatic reactor trip of Unit 2. Water spray from a ruptured fire water pipe migrated into the ANO-2 non-vital switchgear area located just off the train bay causing an


electrical fault inside the non-vital Unit 2 electrical switchgear approximately 90 minutes after the
electrical fault inside the non-vital Unit 2 electrical switchgear approximately 90 minutes after the


stator drop. This fault caused a lockout of start-up transformer 3 and a partial LOOP for Unit 2.
stator drop. This fault caused a lockout of start-up transformer 3 and a partial LOOP for Unit 2.


Loss of power to all four reactor coolant pumps necessitated a natural circulation plant
Loss of power to all four reactor coolant pumps necessitated a natural circulation plant
Line 157: Line 169:
LOOP.
LOOP.


The temporary lifting rig collapse resulted from errors in contractor design calculations. The
The temporary lifting rig collapse resulted from errors in contractor design calculations. The


basic lifting rig design had been used by the contractor for stator lifts at other nuclear power
basic lifting rig design had been used by the contractor for stator lifts at other nuclear power


plants; however, the design of the rig had been modified for use at ANO. The licensee failed to
plants; however, the design of the rig had been modified for use at ANO. The licensee failed to


perform an adequate review of the contractors modified design calculations, and failed to
perform an adequate review of the contractors modified design calculations, and failed to
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require the contractor to perform a load test in accordance with site procedures and applicable
require the contractor to perform a load test in accordance with site procedures and applicable


regulations. These failures were the result of inadequate oversight by the licensee. The
regulations. These failures were the result of inadequate oversight by the licensee. The


licensee repaired the damage to the plant and updated procedures to provide guidance on
licensee repaired the damage to the plant and updated procedures to provide guidance on
Line 179: Line 191:
Generator Stator Temporary Lift Assembly Results in a Fatality, Multiple Injuries, a Plant Scram, a Notification of Unusual Event, and Dual Unit Structural Damage, dated August 22, 2013 (ADAMS Accession No. ML12109A049).
Generator Stator Temporary Lift Assembly Results in a Fatality, Multiple Injuries, a Plant Scram, a Notification of Unusual Event, and Dual Unit Structural Damage, dated August 22, 2013 (ADAMS Accession No. ML12109A049).


===Comanche Peak Nuclear Power Plant, Unit 1 and Unit 2===
Comanche Peak Nuclear Power Plant, Unit 1 and Unit 2  
 
On December 4, 2013, Comanche Peak Nuclear Power Plant (Comanche Peak) experienced a
On December 4, 2013, Comanche Peak Nuclear Power Plant (Comanche Peak) experienced a


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transformer was mistakenly cut while the other start-up transformer was out of service for
transformer was mistakenly cut while the other start-up transformer was out of service for


modifications. Both units remained at full power as nonsafety-related loads (including reactor
modifications. Both units remained at full power as nonsafety-related loads (including reactor


coolant pumps) continued to receive power from the main generator through the unit auxiliary
coolant pumps) continued to receive power from the main generator through the unit auxiliary


transformer. All four emergency diesel generators started automatically and re-energized the
transformer. All four emergency diesel generators started automatically and re-energized the


safety-related busses.
safety-related busses.
Line 196: Line 209:
Comanche Peak was in the process of implementing a modification to start-up transformer
Comanche Peak was in the process of implementing a modification to start-up transformer


XST-1. In preparation for the work, contract personnel had walked down the cables for XST-1 to ensure the correct cables were identified. However, an incorrect assumption about the layout
XST-1. In preparation for the work, contract personnel had walked down the cables for XST-1 to ensure the correct cables were identified. However, an incorrect assumption about the layout


of the cable bus enclosure routing, combined with a failure to use design drawings to facilitate
of the cable bus enclosure routing, combined with a failure to use design drawings to facilitate
Line 202: Line 215:
the walkdown, contributed to the contractors misidentifying a feeder cable for the other start-up
the walkdown, contributed to the contractors misidentifying a feeder cable for the other start-up


transformer, XST-2, rather than the cable for XST-1. The licensee did not validate the resulting
transformer, XST-2, rather than the cable for XST-1. The licensee did not validate the resulting


work plan provided by the contractors. The contract electricians performing the work raised
work plan provided by the contractors. The contract electricians performing the work raised


questions about the accuracy of the cable identification, but failed to pursue the issue, contrary
questions about the accuracy of the cable identification, but failed to pursue the issue, contrary


to station procedures. The licensee repaired the cut cable to restore off-site power, and
to station procedures. The licensee repaired the cut cable to restore off-site power, and


improved procedures regarding the design change development, review, and oversight
improved procedures regarding the design change development, review, and oversight
Line 222: Line 235:
Violation, dated August 6, 2014 (ADAMS Accession Nos. ML14043A089 and ML14218A072, respectively).
Violation, dated August 6, 2014 (ADAMS Accession Nos. ML14043A089 and ML14218A072, respectively).


===Joseph M. Farley Nuclear Plant, Unit 2===
Joseph M. Farley Nuclear Plant, Unit 2  
 
On October 14, 2014, a lightning strike on a 500kV line caused a partial LOOP to Joseph M.
On October 14, 2014, a lightning strike on a 500kV line caused a partial LOOP to Joseph M.


Farley Nuclear Plant (Farley), Unit 2. A power circuit breaker opened to clear the fault, and
Farley Nuclear Plant (Farley), Unit 2. A power circuit breaker opened to clear the fault, and


experienced an internal fault on the bus side of the main contacts. The high-fault current
experienced an internal fault on the bus side of the main contacts. The high-fault current


exposed a loose connection, creating a high resistance and differential current signal that led to
exposed a loose connection, creating a high resistance and differential current signal that led to
Line 233: Line 247:
isolation of the 2B start-up auxiliary transformer (SAT), and a LOOP to its associated B train
isolation of the 2B start-up auxiliary transformer (SAT), and a LOOP to its associated B train


power bus. The 2B emergency diesel generator was out of service at the time for scheduled
power bus. The 2B emergency diesel generator was out of service at the time for scheduled


maintenance, and was unable to assume the B train safety-related loads. One of these loads
maintenance, and was unable to assume the B train safety-related loads. One of these loads


was the B train of component cooling water, which was supplying cooling water to reactor
was the B train of component cooling water, which was supplying cooling water to reactor


coolant pump oil coolers and seal coolers at the time of the event. In accordance with the
coolant pump oil coolers and seal coolers at the time of the event. In accordance with the


abnormal operating procedure for loss of component cooling water, operators inserted a manual
abnormal operating procedure for loss of component cooling water, operators inserted a manual
Line 247: Line 261:
The loose connection that caused the isolation of the 2B SAT resulted from improper wiring that
The loose connection that caused the isolation of the 2B SAT resulted from improper wiring that


was introduced during installation of a power circuit breaker 18 months earlier. The breaker
was introduced during installation of a power circuit breaker 18 months earlier. The breaker


installation was part of a design change package for the high-voltage switchyard implemented
installation was part of a design change package for the high-voltage switchyard implemented
Line 253: Line 267:
by the grid operator to replace and upgrade several power circuit breakers and their control
by the grid operator to replace and upgrade several power circuit breakers and their control


relay packages. Testing during the implementation verified the correct installation of the current
relay packages. Testing during the implementation verified the correct installation of the current


transformers and associated wiring. However, inadequate verification practices failed to identify
transformers and associated wiring. However, inadequate verification practices failed to identify


a missing nut on one of the terminals during the installation. This led to a loose connection that
a missing nut on one of the terminals during the installation. This led to a loose connection that


was adequate for normal testing and operational purposes, but not for the conditions
was adequate for normal testing and operational purposes, but not for the conditions


experienced during a ground fault isolation. A contributing cause of this event was the
experienced during a ground fault isolation. A contributing cause of this event was the


licensees failure to fully understand the extent of differences in verification practices performed
licensees failure to fully understand the extent of differences in verification practices performed
Line 269: Line 283:
The missing nut on the power circuit breaker current transformer was installed, and the
The missing nut on the power circuit breaker current transformer was installed, and the


transformer primary and secondary protective relaying functions were tested satisfactorily. In
transformer primary and secondary protective relaying functions were tested satisfactorily. In


addition, the licensee worked to strengthen the application of verification procedures used by
addition, the licensee worked to strengthen the application of verification procedures used by
Line 280: Line 294:


==DISCUSSION==
==DISCUSSION==
Licensees often rely on contractors and supplemental personnel to perform work. This is
Licensees often rely on contractors and supplemental personnel to perform work. This is


especially the case during scheduled outages. This work includes specialized, low-frequency
especially the case during scheduled outages. This work includes specialized, low-frequency


tasks involving one-time modifications or the overhaul of major equipment. The NRC has
tasks involving one-time modifications or the overhaul of major equipment. The NRC has


previously issued several other INs regarding contractor oversight issues, such as IN 97-74, Inadequate Oversight of Contractors During Sealant Injection Activities, and IN 00-11, Licensee Responsibility for Quality Assurance Oversight of Contractor Activities Regarding
previously issued several other INs regarding contractor oversight issues, such as IN 97-74, Inadequate Oversight of Contractors During Sealant Injection Activities, and IN 00-11, Licensee Responsibility for Quality Assurance Oversight of Contractor Activities Regarding
Line 296: Line 310:
assurance expectations of plant process controls and, for safety-related equipment, the
assurance expectations of plant process controls and, for safety-related equipment, the


requirements of the plants NRC-approved quality assurance program. While the work activities
requirements of the plants NRC-approved quality assurance program. While the work activities


discussed in this IN were associated with non-safety related equipment, each event placed the
discussed in this IN were associated with non-safety related equipment, each event placed the
Line 306: Line 320:
Industry operating experience has shown the importance of licensee programs designed to
Industry operating experience has shown the importance of licensee programs designed to


ensure effective station oversight of contractor activities. Establishing clear lines of
ensure effective station oversight of contractor activities. Establishing clear lines of


accountability within the licensee organization that maintains sufficient knowledge and technical
accountability within the licensee organization that maintains sufficient knowledge and technical


expertise to exercise an appropriate level of oversight of the design, maintenance, modification, or refurbishment activities performed by contracted personnel is essential. This includes
expertise to exercise an appropriate level of oversight of the design, maintenance, modification, or refurbishment activities performed by contracted personnel is essential. This includes


verification that procedures and work instructions contain sufficient detail, and that supplemental
verification that procedures and work instructions contain sufficient detail, and that supplemental
Line 319: Line 333:


==CONTACT==
==CONTACT==
This IN requires no specific action or written response. Please direct any questions about this
This IN requires no specific action or written response. Please direct any questions about this


matter to the technical contacts listed below, or the appropriate Office of Nuclear Reactor
matter to the technical contacts listed below, or the appropriate Office of Nuclear Reactor
Line 325: Line 339:
Regulation (NRR) project manager.
Regulation (NRR) project manager.


/ra/                                                   /ra/
/ra/  
Michael C. Cheok, Director                             Louise Lund, Director
 
/ra/  
 
Michael C. Cheok, Director
 
Louise Lund, Director
 
Division of Construction Inspection
 
Division of Policy and Rulemaking
 
and Operational Programs
 
Office of Nuclear Reactor Regulation
 
Office of New Reactors
 
Technical Contacts: Rebecca Sigmon, NRR
 
Jesse Robles, NRR
 
301-415-0895
301-415-2940
E-mail: Rebecca.Sigmon@nrc.gov E-mail: Jesse.Robles@nrc.gov
 
Note:  NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under NRC Library.
 
ML16057A842    *via email
 
TAC: MF7293 OFFICE
 
TECH EDITOR
 
NRR/DIRS/IOEB/TL
 
NRR/DIRS/IOEB/TL
 
NRR/DE/EEEB/BC
 
NRR/DIRS/IOEB/BC
 
NAME
 
JDougherty*
RSigmon*
JRobles*
JZimmerman*
HChernoff*
DATE
 
03/11/2016
05/16/2016
05/18/2016
05/25/2016
05/18/2016 OFFICE
 
NRR/DIRS/D
 
NRR/DPR/PGCB/PM
 
NRR/DPR/PGCB/LA
 
NRR/DPR/PGCB/BC


Division of Construction Inspection                    Division of Policy and Rulemaking
NRO/DCIP/D


and Operational Programs                            Office of Nuclear Reactor Regulation
NAME


===Office of New Reactors===
SMorris*
Technical Contacts:    Rebecca Sigmon, NRR                    Jesse Robles, NRR
ASchwab*
ELee*
SStuchell*
MCheok


301-415-0895                          301-415-2940
DATE
                        E-mail: Rebecca.Sigmon@nrc.gov        E-mail: Jesse.Robles@nrc.gov


Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under NRC Library.
05/27/2016
05/27/2016
05/31/2016
05/31/2016
06/20/2016 OFFICE


ML16057A842      *via email                                      TAC: MF7293 OFFICE  TECH EDITOR            NRR/DIRS/IOEB/TL      NRR/DIRS/IOEB/TL      NRR/DE/EEEB/BC    NRR/DIRS/IOEB/BC
NRR/DPR/D


NAME     JDougherty*            RSigmon*              JRobles*              JZimmerman*        HChernoff*
NAME
DATE    03/11/2016            05/16/2016            05/18/2016            05/25/2016        05/18/2016 OFFICE  NRR/DIRS/D            NRR/DPR/PGCB/PM        NRR/DPR/PGCB/LA      NRR/DPR/PGCB/BC    NRO/DCIP/D


NAME    SMorris*              ASchwab*              ELee*                SStuchell*        MCheok
LLund


DATE     05/27/2016            05/27/2016            05/31/2016            05/31/2016        06/20/2016 OFFICE  NRR/DPR/D
DATE


===NAME    LLund===
06/20/2016}}
DATE    06/20/2016}}


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

Latest revision as of 02:42, 10 January 2025

Operating Experience Regarding Impacts on Site Electrical Power Distribution from Inadequate Oversight of Contractor Activities
ML16057A842
Person / Time
Issue date: 06/20/2016
From: Michael Cheok, Louise Lund
Division of Construction Inspection and Operational Programs, Generic Communications Projects Branch
To:
Schwab A
References
IN-16-007
Download: ML16057A842 (6)
v • d • e


ML16057A842

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

OFFICE OF NEW REACTORS

WASHINGTON, DC 20555-0001

June 20, 2016

NRC INFORMATION NOTICE 2016-07:

OPERATING EXPERIENCE REGARDING

IMPACTS ON SITE ELECTRICAL POWER

DISTRIBUTION FROM INADEQUATE

OVERSIGHT OF CONTRACTOR ACTIVITIES

ADDRESSEES

All holders of an operating license or construction permit for a nuclear power reactor under

Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of

Production and Utilization Facilities, except those that have permanently ceased operations

and have certified that fuel has been permanently removed from the reactor vessel.

All holders of and applicants for a power reactor combined license under 10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants.

PURPOSE

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

addressees of adverse effects to off-site power availability that have resulted from inadequate

licensee oversight of contractor activities. It is expected that recipients will review the

information for applicability to their facilities and consider actions, as appropriate, to avoid

similar problems. However, suggestions contained in this IN are not NRC requirements;

therefore, no specific action or written response is required.

DESCRIPTION OF CIRCUMSTANCES

Wolf Creek Generating Station, Unit 1

On January 13, 2012, Wolf Creek Generating Station (Wolf Creek) experienced an automatic reactor trip after the catastrophic failure of the main generator output breaker. The start-up

transformer assumed nonsafety-related loads, but subsequently experienced a differential relay

actuation on its B phase. This caused a lockout of the start-up transformer and a loss of

off-site power (LOOP). Both emergency diesel generators started and supplied power to the

safety-related 4160 volt busses as expected.

The LOOP resulted in several complications, including:

erratic source range nuclear instrumentation indications resulting from the loss of power

to containment cavity cooling fans *

containment sump high level alarms caused by a through-wall leak in essential service

water (ESW) piping in containment resulting from a known issue with water hammer

caused by the stop-start sequence of ESW pumps following a LOOP

a loss of firefighting capability for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> because of the loss of power to normal fire

pumps in conjunction with the long-term inoperability of the installed diesel-powered fire

pump and inadequacies with the procedure for starting a temporary fire pump

a loss of reactor coolant pumps necessitating a natural circulation cooldown, and

a loss of instrument air complicating operator control of pressurizer level and pressure

The cause of the LOOP was the actuation of protective relaying resulting from a short between

two taps on the high side current transformers. During the previous year, the licensee had

contracted with a vendor to replace electrical seal assemblies in the start-up transformer that

experienced oil leakage. This vendor performed the majority of the work in accordance with

established instructions and practices, but failed to install insulating sleeves on 2 of the 37 wiring connections. These sleeves are required to prevent terminal-to-terminal contact. The

investigation that followed determined that the licensee failed to satisfy the requirements of

written procedures to ensure that (1) field activities were adequately monitored, and (2) periodic

verification of contracted work was conducted to verify that it was performed in accordance with

applicable work orders. After the event, the licensee installed the missing insulation sleeves, and updated station procedures regarding the oversight of contractors performing work on

risk-significant components.

This IN provides no new information on this event. The condition described was summarized

from previously-released reports prepared by an NRC Augmented Inspection Team (AIT)

chartered shortly after the event in 2012 to review the facts surrounding the LOOP, and the

complications that resulted. Additional information can be found in Licensee Event Report

05000482/2012-001, Failure of 345 kV Switchyard Breaker due to Internal Fault Resulting in

Reactor Trip and Coincident Loss of Offsite Power, dated April 9, 2012, in Wolf Creek Nuclear

Operating Corporation-NRC Augmented Inspection Team Report 05000482/2012008, dated

April 4, 2012, and in the NRC Augmented Inspection Team Follow-Up Report

05000482/2012009, dated August 6, 2012 (Agencywide Documents Access and Management

System (ADAMS) Accession Nos. ML12109A049, ML12095A414, and ML12227A919, respectively).

Arkansas Nuclear One, Unit 1 and Unit 2

On March 31, 2013, at Arkansas Nuclear One (ANO) during its Unit 1 outage, an inadequately

designed temporary lifting rig failed while moving the Unit 1 main generator stator out of the

turbine building. The 525-ton stator fell onto the turbine deck and then continued falling

approximately 30 feet into a train bay that is shared between Units 1 and 2. The collapse of the

lifting rig resulted in one fatality and injured eight others. The impact of the dropped stator on

the turbine deck damaged the Unit 1 non-vital electrical switchgear connecting plant vital busses

to off-site power, causing a LOOP to Unit 1 for six days.

At the time of the event, Unit 2 was operating at 100 percent power. Vibrations from the stator

drop and temporary lift rig collapse caused a Unit 2 reactor coolant pump breaker to trip, resulting in an automatic reactor trip of Unit 2. Water spray from a ruptured fire water pipe migrated into the ANO-2 non-vital switchgear area located just off the train bay causing an

electrical fault inside the non-vital Unit 2 electrical switchgear approximately 90 minutes after the

stator drop. This fault caused a lockout of start-up transformer 3 and a partial LOOP for Unit 2.

Loss of power to all four reactor coolant pumps necessitated a natural circulation plant

cooldown, which was complicated by additional equipment unavailability due to the partial

LOOP.

The temporary lifting rig collapse resulted from errors in contractor design calculations. The

basic lifting rig design had been used by the contractor for stator lifts at other nuclear power

plants; however, the design of the rig had been modified for use at ANO. The licensee failed to

perform an adequate review of the contractors modified design calculations, and failed to

require the contractor to perform a load test in accordance with site procedures and applicable

regulations. These failures were the result of inadequate oversight by the licensee. The

licensee repaired the damage to the plant and updated procedures to provide guidance on

review of calculations, quality requirements, and standards associated with third party reviews.

The NRC chartered and dispatched an AIT to review the facts of the event. Additional

information can be found in Licensee Event Report 05000313/2013-001, Collapse of a Main

Generator Stator Temporary Lift Assembly Results in a Fatality, Multiple Injuries, a Plant Scram, a Notification of Unusual Event, and Dual Unit Structural Damage, dated August 22, 2013 (ADAMS Accession No. ML12109A049).

Comanche Peak Nuclear Power Plant, Unit 1 and Unit 2

On December 4, 2013, Comanche Peak Nuclear Power Plant (Comanche Peak) experienced a

LOOP to safety-related busses when an energized cable feeding the in-service start-up

transformer was mistakenly cut while the other start-up transformer was out of service for

modifications. Both units remained at full power as nonsafety-related loads (including reactor

coolant pumps) continued to receive power from the main generator through the unit auxiliary

transformer. All four emergency diesel generators started automatically and re-energized the

safety-related busses.

Comanche Peak was in the process of implementing a modification to start-up transformer

XST-1. In preparation for the work, contract personnel had walked down the cables for XST-1 to ensure the correct cables were identified. However, an incorrect assumption about the layout

of the cable bus enclosure routing, combined with a failure to use design drawings to facilitate

the walkdown, contributed to the contractors misidentifying a feeder cable for the other start-up

transformer, XST-2, rather than the cable for XST-1. The licensee did not validate the resulting

work plan provided by the contractors. The contract electricians performing the work raised

questions about the accuracy of the cable identification, but failed to pursue the issue, contrary

to station procedures. The licensee repaired the cut cable to restore off-site power, and

improved procedures regarding the design change development, review, and oversight

processes.

Additional information can be found in Licensee Event Report 05000445/2013-003, Auto Start

of Both Units' Auxiliary Feedwater Pumps and Emergency Diesel Generators Due to a Loss of

Both Units' Safeguards Electrical Power, dated January 30, 2014 and in Comanche Peak Nuclear Power Plant-NRC Integrated Inspection Report 05000445/2014003 and Notice of

Violation, dated August 6, 2014 (ADAMS Accession Nos. ML14043A089 and ML14218A072, respectively).

Joseph M. Farley Nuclear Plant, Unit 2

On October 14, 2014, a lightning strike on a 500kV line caused a partial LOOP to Joseph M.

Farley Nuclear Plant (Farley), Unit 2. A power circuit breaker opened to clear the fault, and

experienced an internal fault on the bus side of the main contacts. The high-fault current

exposed a loose connection, creating a high resistance and differential current signal that led to

isolation of the 2B start-up auxiliary transformer (SAT), and a LOOP to its associated B train

power bus. The 2B emergency diesel generator was out of service at the time for scheduled

maintenance, and was unable to assume the B train safety-related loads. One of these loads

was the B train of component cooling water, which was supplying cooling water to reactor

coolant pump oil coolers and seal coolers at the time of the event. In accordance with the

abnormal operating procedure for loss of component cooling water, operators inserted a manual

reactor trip.

The loose connection that caused the isolation of the 2B SAT resulted from improper wiring that

was introduced during installation of a power circuit breaker 18 months earlier. The breaker

installation was part of a design change package for the high-voltage switchyard implemented

by the grid operator to replace and upgrade several power circuit breakers and their control

relay packages. Testing during the implementation verified the correct installation of the current

transformers and associated wiring. However, inadequate verification practices failed to identify

a missing nut on one of the terminals during the installation. This led to a loose connection that

was adequate for normal testing and operational purposes, but not for the conditions

experienced during a ground fault isolation. A contributing cause of this event was the

licensees failure to fully understand the extent of differences in verification practices performed

by an outside organization.

The missing nut on the power circuit breaker current transformer was installed, and the

transformer primary and secondary protective relaying functions were tested satisfactorily. In

addition, the licensee worked to strengthen the application of verification procedures used by

the utility performing the switchyard maintenance.

Additional information can be found in Licensee Event Report 05000364/2014-002, Manual Reactor Trip due to Loss of 2B [Start-up] Auxiliary Transformer and Loss of Offsite Power, dated December 12, 2014 (ADAMS Accession No. ML14346A391).

DISCUSSION

Licensees often rely on contractors and supplemental personnel to perform work. This is

especially the case during scheduled outages. This work includes specialized, low-frequency

tasks involving one-time modifications or the overhaul of major equipment. The NRC has

previously issued several other INs regarding contractor oversight issues, such as IN 97-74, Inadequate Oversight of Contractors During Sealant Injection Activities, and IN 00-11, Licensee Responsibility for Quality Assurance Oversight of Contractor Activities Regarding

Fabrication and Use of Spent Fuel Storage Cask Systems.

Although the performance of particular tasks, including the development and execution of work

instructions and procedures, may be delegated to outside organizations, the licensee retains overall responsibility for ensuring that the procedures and their execution meet the quality

assurance expectations of plant process controls and, for safety-related equipment, the

requirements of the plants NRC-approved quality assurance program. While the work activities

discussed in this IN were associated with non-safety related equipment, each event placed the

plant in a LOOP condition and challenged the operability and reliability of safety-related

equipment.

Industry operating experience has shown the importance of licensee programs designed to

ensure effective station oversight of contractor activities. Establishing clear lines of

accountability within the licensee organization that maintains sufficient knowledge and technical

expertise to exercise an appropriate level of oversight of the design, maintenance, modification, or refurbishment activities performed by contracted personnel is essential. This includes

verification that procedures and work instructions contain sufficient detail, and that supplemental

personnel are familiar with site work control processes and expectations for procedure

adherence.

CONTACT

This IN requires no specific action or written response. Please direct any questions about this

matter to the technical contacts listed below, or the appropriate Office of Nuclear Reactor

Regulation (NRR) project manager.

/ra/

/ra/

Michael C. Cheok, Director

Louise Lund, Director

Division of Construction Inspection

Division of Policy and Rulemaking

and Operational Programs

Office of Nuclear Reactor Regulation

Office of New Reactors

Technical Contacts: Rebecca Sigmon, NRR

Jesse Robles, NRR

301-415-0895

301-415-2940

E-mail: Rebecca.Sigmon@nrc.gov E-mail: Jesse.Robles@nrc.gov

Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under NRC Library.

ML16057A842 *via email

TAC: MF7293 OFFICE

TECH EDITOR

NRR/DIRS/IOEB/TL

NRR/DIRS/IOEB/TL

NRR/DE/EEEB/BC

NRR/DIRS/IOEB/BC

NAME

JDougherty*

RSigmon*

JRobles*

JZimmerman*

HChernoff*

DATE

03/11/2016

05/16/2016

05/18/2016

05/25/2016

05/18/2016 OFFICE

NRR/DIRS/D

NRR/DPR/PGCB/PM

NRR/DPR/PGCB/LA

NRR/DPR/PGCB/BC

NRO/DCIP/D

NAME

SMorris*

ASchwab*

ELee*

SStuchell*

MCheok

DATE

05/27/2016

05/27/2016

05/31/2016

05/31/2016

06/20/2016 OFFICE

NRR/DPR/D

NAME

LLund

DATE

06/20/2016


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