United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #:  9705140175

                       LICENSEE EVENT REPORT (LER)



FACILITY NAME:  Quad Cities Unit One                      PAGE: 1 OF 5



DOCKET NUMBER:  05000254



TITLE:  The Residual Heat Removal Service Water System was made

        inoperable due to uncertainties related to 4 KV Air

        Magne-Blast Horizontal Gas (AMHG) circuit breakers, which

        had experienced cracks in the auxiliary switches mounting

        channels.



EVENT DATE:  04/09/97   LER #:  97-011-00   REPORT DATE:  04/30/97



OTHER FACILITIES INVOLVED:  Quad Cities 2           DOCKET NO:  05000265



OPERATING MODE:  1   POWER LEVEL:  100



THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR

SECTION:

50.73(a)(2)(i), 50.73(a)(2)(v)



LICENSEE CONTACT FOR THIS LER:

NAME:  Charles Peterson, Regulatory         TELEPHONE:  (309) 654-2241

       Affairs Manager,  ext. 3609



COMPONENT FAILURE DESCRIPTION:

CAUSE:  B   SYSTEM:  EB   COMPONENT:  52   MANUFACTURER:  G168

REPORTABLE NPRDS:  N



SUPPLEMENTAL REPORT EXPECTED:  NO



ABSTRACT:



The 4 KiloVolt (KV) circuit breakers at buses 13, 14, 23 and 24 were

declared inoperable on 040997 at 1330 hours due to cracks in 4 KV Air

Magne-Blast Horizontal Gas (AMHG)circuit breaker auxiliary switches.  The

affected breakers included Residual Heat Removal (RHR) Service Water (SW)

and offsite power distribution breakers.  The apparent cause of the event

was a improper manufacturer's switch mounting design.  Unit one was shut

down due to Technical Specification 3.8.A.  Action 1.d for both RHR SW

subsystems being declared inoperable.



A design change has been completed to install a mounting strap around

auxiliary switches for all affected Unit 14 KV breakers and the Unit 24

KV breaker which provide a path for backup power to Unit 1 from the Unit

2 Reserve Auxiliary Transformer.  The same design will be completed for

the remaining Unit 2 breakers prior to start up from Q2R14.



The impact on Safety was minimal in that power would have always been

available to Alternating Current (AC) powered Emergency Core Cooling

(ECCS) Equipment from Diesel Generator Supplied 4 KV Essential Service

buses 13-1, 14-1, 23-1 and 24-1.



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END OF ABSTRACT



TEXT                                                          PAGE 2 OF 5



PLANT AND SYSTEM IDENTIFICATION:



General Electric - Boiling Water Reactor - 2511 MWt rated core thermal

power.



EVENT IDENTIFICATION: The Residual Heat Removal Service Water System was

made inoperable due to uncertainties related to 4 KV AMHG breakers, which

had experienced cracks in the auxiliary switches mounting channels.



A.   CONDITIONS PRIOR TO EVENT:



     Unit: One           Event Date: 040997            Event Time: 1330

     Reactor Mode: 1     Mode Name: POWER OPERATION    Power Level: 100%



     POWER OPERATION Mode (1): Mode switch in the Run position with

     average reactor coolant temperature at any temperature.



     Unit: Two           Event Date: 040997            Event Time: 1330

     Reactor Mode: 5     Mode Name: REFUELING          Power Level: 000%



     REFUELING Mode (5): Mode switch in the Shutdown or Refueling

     position with average reactor coolant temperature < 140 degrees F

     and fuel in the reactor vessel with one or more vessel head closure

     bolts less than fully tensioned or with the head removed.



B.   EVENT DESCRIPTION:



     On 040197 during installation and construction testing of new Sulfur

     Hexaflouride (SF6) Air Magne-Blast Horizontal Gas (AMHG) 4 KV

     Circuit Breakers [EB] on Unit 2 at Bus 23-1, a breaker auxiliary

     switch (52 AUX/UPPER) was found broken loose from the mounting

     bracket.  These breaker auxiliary switch contacts are used in the

     breaker trip circuits, breaker close circuits, breaker anti-pumping

     circuit, breaker position indication circuits and for various other

     control functions depending on the switchgear cubicle in which the

     breaker is installed.  These AMHG 4 KV Circuit Breakers are being

     installed in the General Electric Air Magne-Blast Horizontal (AMH)

     Type Switchgear to replace the existing General Electric AMH 4KV

     Circuit Breakers.  This was the third broken auxiliary switch found

     on AMHG breakers.  The first auxiliary switch was found during

     factory production testing at Pacific Breaker Systems (PBS) on

     021197.  The broken switch was replaced at the factory.



     The second broken auxiliary switch was found at Quad Cities Station

     on 030597 after the breaker had been staged on the turbine floor

     prior to installation.  Problem Identification Form (PIF) 97-0822

     was prepared in response to this.



     Additionally, 12 installed, in-service auxiliary switches were found

     to be cracked.  These switches were installed at buses 23 and 24.

     These cracked switches were found during a field walkdown/inspection

     on 040897.



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TEXT                                                          PAGE 3 OF 5



     An operability determination determined that all the breakers on

     buses 13, 14, 23 and 24 [EB] were inoperable on 040997 at 1205

     hours.  A shutdown was commenced at 1330 hours on Unit one due to

     Technical Specification 3.8.A.  Action 1.d for both Residual Heat

     Removal (RHR) [BO] Service Water (SW) [BI] subsystems inoperable.

     The 4 KV AMHG breakers installed at buses 13 and 14, which include

     all four RHRSW pump breakers and off-site power distribution

     breakers, had been determined to be inoperable due to cracked

     auxiliary switch mounting channels.  Operations made an ENS

     notification at 1337 hours due to the Technical Specification

     required shutdown per 10CFR50.72.b.1.i.A and the inoperable RHRSW

     subsystem per 10CFR50.72.b.2.ii.B.



     The breaker auxiliary switch is a subcomponent of the 4 KV breakers.

     The affected breakers are all the SF6 AMHG circuit breakers provided

     with these switches.  These circuit breakers are installed and in

     service on Unit 1 at safety related busses 13, 14 and on Unit 2 at

     safety related buses 23 and 24.  They are presently being installed

     on Unit 2 at safety related buses 23-1 and 24-1.  Installation is

     scheduled for Unit 1 safety related buses 13-1 and 14-1 during the

     next Unit I refueling outage (Q1R15).  These breakers are also

     installed and in service at non-safety Station Black Out (SBO) buses

     61 and 71.



     On 041197 Golden Gate Switchboard Company issued a Notification of

     Potential Defect under the Requirements of 10CFR21.21b.



C.   APPARENT CAUSE OF THE EVENT:



     The apparent cause of the event was an improper manufacturer's

     switch mounting design.  There is a design weakness in the auxiliary

     switch mounting that manifests itself in cracks in the switch

     mounting channels.  In extreme cases sufficient cracking can occur

     to cause the switch to separate from the mounting plate.



     A failure of the auxiliary switch mounting can result in a failure

     of these auxiliary contacts to reposition following opening or

     closing the breaker which may disable the circuit in which the

     switch is wired.  For example, if the normal power supply breaker,

     Transformer 11 to Bus 14 (Main Feed), spuriously trips open the

     Transformer 12 to Bus 14 (Reserve Feed) breaker would not receive

     the auto-close signal if the auxiliary contacts fail to reposition.



     The manufacturer of the Breakers (Merlin Gerin) is investigating the

     cause of the event.  The results of this investigation will be

     reported per the requirements of 10CFR21.21.



D.   SAFETY ANALYSIS OF THE EVENT:



     The consequences of this event are considered minimal.  There was no

     effect on the public or the control room personnel due to this

     event.



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TEXT                                                          PAGE 4 OF 5



     During a design basis accident, the RHRSW system functions to

     support the RHR system to limit suppression pool temperatures as

     required to maintain Emergency Core Cooling Systems (ECCS) pump

     suction head.  In addition, there are two RHRSW pumps for each RHR

     heat exchanger to provide redundancy.  During a design basis

     accident one RHRSW pump provides adequate cooling water flow to the

     associated RHR heat exchanger.  No in-service breaker failures

     actually occurred at Quad Cities, so the likelihood of losing all

     four RHRSW pumps when needed during an event due to breaker failure

     from this phenomenon or a random failure is extremely low.



     The breakers for the 4 KV Essential Service buses 13-1, 14-1 and

     24-1 have not been replaced.  The breakers for 4 KV service for 23-1

     were in the process of being replaced when the problem was

     identified.  These four buses supply power to all of the AC

     Emergency Core Cooling System (ECCS) Equipment.  These buses have

     backup power supplied from Emergency Diesel Generators (EDGs).  Thus

     when the Units were operating, AC power was never in question for

     the ECCS equipment as a result of this issue.



E.   CORRECTIVE ACTIONS:



     Corrective Actions Completed:



     1.   PIF 97-1276 was written to investigate the cause of the

          improper manufacturer's switch mounting design.  A level 2

          investigation for PIF 97-1276 is in progress.



     2.   All 4 KV breakers which utilize a Merlin Gerin auxiliary switch

          were declared inoperable, and a shutdown on Unit 1 was

          completed.



     3.   Breakers were sent to corporate Materials Engineering Group for

          additional testing and the performance of a failure mode

          assessment.  This testing identified that the breakers could

          have performed their design function with cracking present in

          the switch mounting plastic and that a design change to install

          a strap on the auxiliary switches would be effective.



     4.   On April 11, 1997, Golden Gate Switchboard Company issued a

          "Notification of Potential Defect under the Requirements of

          10CFR21.21(b)."



     5.   A design to install a mounting strap around the rear of the

          upper and lower auxiliary switches to ensure they remain

          securely fastened to their mounting brackets was performed for

          all affected Unit 1 4 KV breakers and the Unit 2 4 KV breaker

          which provide a path for backup power from the Unit 2 Reserve

          Auxiliary Transformer to Unit 1.  Unit 1 was completed by

          Design Change Package (DCP) 9700134.  The Unit 2 breakers were

          completed by DCP 9700141.



     6.   Operations Department has implemented periodic inspection

          requirements to visually check the position indicator flag on

          each circuit breaker and weekly log the number of breaker

          cycles to ensure that the number of cycles for which the repair

          has been tested and qualified is not exceeded.



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TEXT                                                          PAGE 5 OF 5



     7.   Maintenance department has implemented periodic inspection

          requirements to visually check the mounting straps on the upper

          and lower auxiliary switches.



     Corrective Actions to be Completed



     1.   Complete DCP 9700144 to install a mounting strap for Unit 2

          breakers prior to start up from Q2R14.  (NTS # 2541809701101)



     2.   Evaluate the feasibility of extending the qualification of the

          mounting strap design by the end of Q1R15 (NTS 2541809701102)

          and Q2R15 (NTS 2541809701103 and NTS 2541809701104).



F.   PREVIOUS EVENTS:



     There have been no previous reportable events regarding failure of

     the auxiliary switches for the 4 KV AMHG breakers.



G.   COMPONENT FAILURE DATA:



     Component Description: 4 KV Breaker Auxiliary Switch

     Manufacturer:  Merlin Gerin

     Breaker Model  Number: (Fluarc FG2) AMHG

     Part Numbers:  Upper switch 7183404A, Lower switch 7183401B



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