ML19332C939

Requests Concurrence to Deviate from Action 7 of NRC Bulletin 88-010, Nonconforming Molded-Case Circuit Breakers

ML19332C939
Person / Time
Site:	Quad Cities
Issue date:	11/20/1989
From:	Richter M COMMONWEALTH EDISON CO.
To:	Ross T Office of Nuclear Reactor Regulation
References
IEB-88-010, IEB-88-10, NUDOCS 8911290203
Download: ML19332C939 (16)

Text

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1 November-20, 1989 L'

-Mr. Thierry Ross Nuclear Reactor Regulation

.U.S. Nuclear Regulatory Commission

=Hashington, D.C. 20555 i

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Subject:

Molded-Case Circuit Breaker Replacements for Quad Cities Unit 1, t

'NBC Docket No. 50-254

Reference:

NRC Bulletin 88-10,' Nonconforming Holded-Case Circuit Breakers, dated November 22, 1988.

4 Mr. Ross:

l During the course.of the current refueling outage for Quad Cities Unit 1,

it'became.necessary to use three molded-case circuit breekers (HCCBs) from

' stock which were restricted from use by Action 7 of NRC Bulletin'88-10 (the Bulletin). As indicated in previous discussions.with'the NRC on thisomatter, these breakers have been tested in accordance with the Bulletin'(as.well ast additional station testing).

During these discussions, the NRC requested Commonwealth Edison (Edison) to submit a report on these: breakers prior'to unit startup. The Attachnents to-this letter provide an evaluation for the Luse of the three breakers.

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Hith this letter, Edison is requesting concurrence to deviate from Action-l -

7 of the Bulletin for the three breakers discussed in the Attachments. The_

breakers supply power to the following motor-operated valves; RCIC Cooling Hater to Lube Oil Cooler and Turbine Barometric l

Condenser Valve, HPCI Upstream Suction from Suppression Pool Valve, and

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RWCU System Return to Reactor Header Isolation Valve.

7EZ I 8911290203 891120 PDR ADOCK 05000254 r (

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e iti: p It is expected that traceable replacement breakers (which satisfy Action 7

of the Bulletin) for the RCIC and HPCI applications will be obtained by the end of January, 1990.

Following receipt and testing of these breakers, they will be= installed during the first unit outage of sufficient duration (not to

. exceed the next refueling outage).

It is expected that a traceable replacement breaker (which satisfies Action 7 of_the Bulletin)'for the RHCU application will be obtained by the end of December, 1989. Following receipt and testing of this breaker, it will be installed at the first available opportunity which will not jeopardize or impact the operation of the unit (not to exceed the next refueling outage).

It is Edison's understanding, per a teleconference with the NRC on

__ November 20, 1989, that preliminary approval has been granted on tnis matter.

Pending a more detailed review, the NRC will provide a formal response.

Please direct any questions on this matter to this office.

1 Respectfully, b

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M.H. Richter Generic Issues Administrator Attachments: A - Molded-Case Circuit Breaker Replacement for RCIC System B - Molded-Case Circuit Breaker Replacement for HPCI System C - Molded-Case Circuit Breaker Replacement for RHCU System 0322k.23

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A.B. Davis, Regional Administrator, Region III Resident Inspector, Quad Cities Station

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AIIACHMENT A 3

OUAD CITIES UNIT 1 MOLDED-CASE CIRCUIT BRE8KER REPLACEMENT Breaker Location:

250V DC Reactor Building MCC Rx #1B, Compt. 01 s

- Equipment Fed:

RCIC Cooling Hater to Lube.011 Cooler and Turbine Barometric Condenser Valve M0-1-1301-62 Breaker

Hestinghouse-Cat. No,' FA3035M, 5 Amp, Adjustable Magnetic - only, Molded-Case Circuit Breaker-During the current Quad Cities Unit I refueling outage, a molded-case circuit breaker (MCCB) in the above location falled during. manual cycling.

The only available replacement breakers in the Commonwealth Edison Company (CECO) system existed at Quad Cities-Station, however, those breakers were restricted from use by Actior. 7 of-Bulletin 88-10 (the Bulletin). A new breaker, which meets the requirements of the Bulletin, is being pursued but cannot be obtained in time to avoid an operational impact on the unit. One of the available replacement breakers at Quad Cities Station has successfully passed the testing delineated in the Bulletin, as well as additional CECO

-testing.

Based on.the results of the testing performed, the replacement breaker has demonstrated that it can be expected to support safe plant operation.

The following paragraphs address the Breaker Failure, System Design Considerations, Replacement Breakers, Breaker Testing, Operability Evaluation and Follow-up Actions.

1 l

BREAKER Fall.URE The installed breaker failed mechanically on September 25, 1989, when the plastic operating' handle broke during manual; cycling of the breaker to perform an operational test on motor operated valve 1-1301-62 (M0-1-1301-62).

The failure no longer allowed the breaker to be operated in the normal, safe y

manner using the through-the-door operating mechanism of the Motor Control Center (MCC) compartment.

This breaker normally remains closed during all l,

Lplant modes and is only opened when taking the valve out-of-service, l'

S15.LEtLDUlGtLC0f!11QERATIONS L

The breaker scpplies power to the control circuit and motor of M0-1-1301-62, RCIC Cooling Hater to Lube 011 Cooler and Turbine' Barometric

-Condenser.

This valve is normally closed but is required to be open during I

RCIC System operation.

The valve is normally cycled twice a month, during valve operability and RCIC System operability surveillances.

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m; The RCICLSystem at Quad Cities Station is not a' safety-related system j

'F but does perform an accident. mitigating, core cooling function for which no

{ credit. is-taken in-the design basis accident analysis.

To accomplish this i

function _.the motor'must.be able to open M0-1-1301-62 reliably.without-

, l tripping the breaker..

' The breaker supplies power to the valve from a O ass li 250V DC MCC.

-The safety. function of the breaker is to trip open on'a downstream short circuit to prevent'the upstream feed to this Class IE MCC Bus from. tripping

-(and'to mitigate the effects of the fault)..As such, the breaker's Interrupting. rating is designed to exceed the available short circuit current,

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and thel breaker is adjusted and tested to trip instantaneously on currents above'the maximum starting current of-the valve motor, but below the trip Lsetting of the MCC. feed 4 REPLACEMENT BREAKERS for the circult breaker that failed, there were no spare breakers of.

the.same'model fn stock at Quad Cities Station, or at any other CECO facility, which were traceable to the circuit breaker manufacturer in accordance'with the requirements of Action 7 of the Bulletin.

A review of unassigned MCC compartments at Quad Cities Station also revealed that no spare breakers of the same model were available.

The failed circuit breaker is an obsolete model (FA type) for which

' direct (like-for-like) replacements are available only as refurbished from

-Westinghouse. Replacement breakers of a later model (FB type) can also be obtained but require a different mounting plate which is not yet seismically qualified for installation at Quad Cities Station.

Either of these options require a-long lead time (approximately 6 to 12 weeks), and neither is the preferred option by CECO. Ceco bas been pursuing a permanent replacement L

. program for the obsolete Westinghouse breakers (FALand EH models) at-Quad Cities Station. An engineering evaluation has recommended the use of, Westinghouse Series C, type HFD breakers (which is a new series line)'for the replacement program.

These breakers-are seismically qualified, however, seismic mounting issues are presently being evaluated.

It is expected that a Hestinghouse HFD breaker for M0-1-1301-62 can be obtained by the end of 1

lanuary, 1990. CECO prefers. utilizing the Hestinghouse HFD breaker for l

consistency purposes with the permanent replacement program.

l Quad-Cities Station had two Hestinghouse FA3035M replacement I

breakers, however, these breakers were procured from Westinghouse Electric l

Supply Company through HLC Electric Supply Company and are nr.'. traceable to the circuit breaker manufacturer.

In response to NRC Informa tion Notice 88-46 (and Bulletin 88-10), these breakers were made unavailable for replacement purposes.

Since these are the only direct replacement breakers readily available, Quad Cities Station tested-these breakers to assess whether one of them could be expected to perform reliably.

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ME$ERTESTING 4

The two replacement bieakers at Quad Cities Station were tested in accordance with the applicable tests of Attachment I to the Bulletin. One of these breakers failed the Instantaneous Trip Test (at the maximem trip setting) whtn the center pole tripped at 80 percent of the rated trip current.

This breaker was not made available for this applicat'cn and controls to prevent usage remain in effect. The ottet breaker passed all of the applicable Bulletin tests and was chosen as the replacement breaker.

The following Bulletin tests were performed cm the replacement breaker;

- mechanical test.

- millivolt drop test.

- rated current hold-in test,

- overload test.

- adjustable instantaneous tilp test (for the maximum arid minimum settings), and

- diele(.tric test.

Subsequent to the Bulletin testing, Quad Cities Station performed additional testing on the replacement breaker in accordance with station procedure QEPM 200-4 (HCCB Inspection and Test).

This procedure is performed on a MCCS prior to installation in a safety-related application and includes t*w test and adjustment of the instantaneous trip element to its installed setting.

The testing of the instantaneous trip element is based on the following two premises:

The largest load the MCCB should be expected to carry without tripping is the motor starting current plus an adequate margin for reliable operation.

The procedure defines 9 times the motor nameplate full load current as the value at which the MCCB should not trip, and 15 times the motor nameplate current as the value at which the MCCD should trip.

The instantaneous trip element of a MCCD is not manufactured as a high precision device, as supported by the tolerances (120% and 25%)

allowed by the manufacturer (and the Bulletin test requirements) at e

the maximum and minimus trip settings.

This has led Quad Cities Station to require-a more precise method of setting the trip element to its particular installed application.

The station procedure adjusts the MCCB to a specific trip condition point to ensure thct the best match exists between providing reliable service to the equipment supplied while still providing maximum protection from domstream short circuit faults.

The procedure (which determines the instantaneous trip current by multiplying the rated equipment current by 12) o was performed in the following manner to adjust the instantaneous trip setting

. for the replacement breaker.

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i With the breaker's instantaneous trip adjustment dial at the maxitua setting, a test current (51 amps), which is 15 times the motor nameplate full load current, was momentarily applied to the MCCB.

If the MCCB did not trip, the trip setting was decreased by one increment and the test repeated using the same test current.

This

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' test / trip adjustment" sequence was repeated until each pole tripped upon application of the test current.

Utilizing the instantaneous trip setting at which each pole tripped, the test current was decreased to a value which is 9 times the motcr nameplate full load current (30.6 amps), and each pole was verified to remain closed upon application of the test current.

Thus, this breaker testing not only verified the proper operation of the trip device, but also optimized its setting to the particular application.

QRIMDILIILEVALVA110N As presented previously, the safety function of the breaker for M0-1-1301-62 is to clear short circuit faults from the Class IE MCC.

The testing of the replacement breaket demonstrated that the breaker will trip on fault currents which are a suitable margin above the anticipated normal' surge currents associated with motor starting and valve seating / unseating.

Additionally, there is assurance that the breaker will successfully clear a fault by the high dielectric resistance readings (5,000 Megohms or greater) between line and load sides at 2500 volts DC.

The high dielectric strength measured between poles (2,500 Megohms or greater) also demonstrated insulation intryv)ty and provides assurance that the replacement breaker itself will not create a fault on the MCC.

Another important function of the breaker for M0-1-1301-62 is to provide reliable power to the valve's circuit. Once again, the testing of the replacement breaker demonstrated this function.

The breaker remained closed under 100 percent rated current for at least one hour witt, no observable detrimental effects.

The breaker remained closed at a surge current which was 9 times greater than the motor nameplate full load current.

The low and consistent voltage drop readings of the poles at full current (approximately 540 millivolts at 5 amps) indicate that the breaker contacts are in good condition, and can supply full voltage to all three phases of the motor with minimal losses.

In addition, M0-1-1301-62 is cycled to demonstrate its operability subsequent to the breaker replacement, and during monthly surveillance testing, providing additional assurance that the replacement breaker can provide the required electr'eal power to the valve.

The results of the testing on the replacement breaker demonstrate that the breaker can be expected to perform its intended safety function.

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[DLLON-UP ACTI.QNS A new breaker (Westinghouse type HFD), traceable to the circuit breaker manufacturer, is being pursued at this time for M0-1-1301-62.

As indicated previously, seismic mounting issues are presently being evaluated.

Following receipt (expected by the end of January 1990) and testing of this traceable breaker, it will be installed during the first unit outage of sufficient duration (not to exceed the next refueling outage).

CONCLU110M Although the replacement breakt does not meet the requirements of Action 7 of Bulletin 88-10 (and in fact has been traced to HLC Electric Supply Company), the breaker has demonstrated through physical testing that it can be expected to perfctm its intended safety function (and support safe plant operation) until a new, traceable breaker becomes available for use.

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AUKiBKMLB QUAD CITIES UNIT 1 MQLDED-CASE CIRCUIT BREAKER REPLACEMERI Breaker Location:

250V DC Reactor Building MCC Rx #1A, Compt. J1 Equipment Fed:

HPCI Upstream Suction from Suppression Pool l

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Valve MO-1-2301-36 Breaker:

Westinghouse Cat. No. FA3190M, 25 Amp, Adjustable Magnetic - only, Molded-Case Circuit Breaker i

During the current Quad Cities Unit I refueling outage, a molded-case circuit breaker (HCCB) in the above location failed during manual cycling.

The only available replacement breaker in the Commonwealth Edison Company (CECO) system existed at Quad Cities Station, however, that breaker was restricted from use by Action 7 of Bulletin 88-10 (the Bulletin). A new bre.Ker, which meets the requirements of the Bulletin, is being pursued but cannot be obtained in time to avoid an operational impact on the unit.

The available replacement breaker at Quad Cities Station has, with one exception, i

successfully passed the testing delineated in the Bulletin, as well as additional CECO testing.

Based on the results of the testing performed, the replacement breaker has demontirated that it can be expected to support safe plant operation.

The following paragraphs address the Breaker Failure, System Design Considerations, Replacement Breakers, Breaker Testing, Operability Evaluation and Foilow-up Actions.

1 l

BREAKER FAILURE The installed breaker failed mechanically on October 17, 1989, when the plastic operating handle broke during manual cycling of the breaker to perform an operational test on motor operated valve 1-2301-36 (H0-1-2301-36).

The failure no longer allowed the breaker to be operated in the normal, safe l

manner using the through-the-door operating mechanism of the Motor Control l

Center (HCC) compartment.

This breaker normally remains closed during all plant modes and is only opened when taking the valve out-of-service.

S1SIEtLDISIGR_CORSIDERATIORS The HPCI System at Quad Cities Station is a safety-related system l.

which performs an accident mitigating, core cooling function.

The breaker that failed supplies power to the control circuit and motor of H0-1-2301-36, HPCI Upstream Suction from the Suppression Pool.

This valve is normally l

closed but is required to open upon low level in the Contaminated Condensate Storage Tank or high level in the Suppression Pool.

Additionally, the valve receives isolation signals for closure under certain conditions.

This valve is normally cycled once a month during a valve operability surveillance.

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The breaker supplies power to M0-1-2301-36 from a Class IE 250V DC l

MCC.

73 accomplish its safety function, the breaker must be able to:

1) allow this valve to open/close reliably without tripping, and 2) trip to clear a downstream short circuit fault to prevent the upstream feed to the MCC from tripping (and to mitigate the effects of the fault).

As such, the breaker's interrupting rating is designed to exceed the available short circuit current, and the breaker is adjusted and tested to trip instantaneously on currents above the maximum starting current of the valve motor, but below the trip setting of the MCC feed.

REELACEMEtG_ BREAKERS f

for the circuit breaker that failed, there were no spare breakers of the-same model in. stock at Quad Cities Station, or at any other CECO f acility, which were traceable to the circuit breaker manufacturer in accordance with the requirements of Action 7 of the Bulletin. A review of unassigned MCC compartments at Quad Cities Station also revealed that no spare breakers of j

the same model were available.

The failed circuit breaker is an obsolete model (FA type) for which i

direct (like-for-like) replacements are available only as refurbished from Westinghouse.

Replacement breakers of a later model (FB type) can also be obtained but require a different mounting plate which is not yet seismically qualified for installation at Quad Cities Station.

Either of these options require a long lead time (approximately 6 to 12 weeks), and neither is the preferred option by CECO. CECO has been pursuing a permanent replacement program for the obsolete Hestinghouse breakers (FA and EH models) at Quad Cities Station.

An engineering evaluation has recommended the use of Hestinghouse Series C, type HFD breakers (which is a new series line) for the replacement program. These breakers are seismically qualified, however, seismic mounting issues are presently being evaluated.

It is expected that a Westinghouse HFD breaker for MO-1-2301-36 can be obtained by the end of January, 1990. CECO prefers utt11 zing the Westinghouse HfD breaker for consistency purposes with the permanent replacement program.

Quad Cities Station had a llestinghouse FA3190M replacement breaker, r

however, in response to Bulletin 88-10 this breaker had been determined to be non-traceable, and unavailable for replacement purposes, due to the age and lack of documentation associated with the purchase order.

Since this was the only direct replacement breaker readily available, Quad Cities Stetton tested the breaker to assess whether it could be expected to perform reliably.

0322k.7

BEEEEILIESlBG The replacement breaker at Quad Cities Station was tested in accordance with the applicable tests (shown below) of Attachment 1 to the Bulletin.

- mechanical test,

- millivolt drop test.

- rated current hold-in test

- overload test.

- adjustable instantaneous _ trip test (for the maximum and minimum settings), and

- dielectric test.

The breaker passed all of the applicable tests with the exception of the adjustable instantaneous trip test (at the minimum setting).

When set at the minimum trip setting, the breaker failed to trip upon application of 125 percent of the trip current (82 5 amps) specified by the manufacturer for that setting.

However, the failure of'this test only demonstrates that the breaker would be unsultable for use if the installed application of the breaker required the minimum trip setting to be uttitzed.

Subsequent to the Bulletin testing, Quad Cities Station performed additional testing on the replacement breaker in accordance with station procedure QEPH 200-4 (MCCB Inspection and Test).

This procedure is performed on a HCCB prior to installation in a safety-related application and includes the-test and adjustment of the instantaneous trip element to its installed setting.

The testing of the instantaneous trip element is based on the following two premises:

The largest load the MCCB should be expected to carry without tripping is the motor starting current plus an adequate margin for reliable operation.

The procedure defines 9 times the motor nameplate full load current as the value at which the MCCB should not trip, and 15 times the motor nameplate current as the value at which the MCCB should trip.

The instantaneous trip element of a HCCB is not manufactured as a l

high precision device, as supported by the tolerances (120% and $25%)

allowed by the manufacturer (and the Bulletin test requirements) at the maximum and minimum trip settings.

This has led Quad Cities Station to require a more precise method of setting the trip element to its particular installed application.

The station procedure adjusts the MCCB to a specific trip condition I

i l

point to ensure that the best match exists between providing reliable service l

to the equipment supplied while still providing maximum protection from i

downstream short circuit faults.

The procedure (which determines the instantaneous trip current by multiplying the rated equipment current by 12)

'was performed in the following manner to adjust the instantaneous trip setting for the replacement breaker.

Hith the breaker's instantaneous trip adjustment dial at the maximum setting, a test current (112.5 amps), which is 15 times the motor i

nameplate full load current, was momentarily applied to the MCCB.

If the MCCB did not trip, the trip setting was decreased by one increment and the test repeated using the same test current.

This i

" test / trip adjustment" sequence was repeated until e d, p u tripped upon application of the test current.

0322k.8

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- Utilizing the instantaneous trip setting at which each pole tripped, the test current was decreased to a value which is 9 times the motor 1-nameplate full load current (67.5 amps), and each pole was verified to remain closed upon application of the test current.

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Thus, this breaker testing not only verified the proper operation of the trip device, but also optimized its setting to the particular application.

For this particular application, the breaker's minimum trip setting (which failed the Bulletin testing) is not used, and therefore, has no impact on the operation of the breaker.

QEGMll,ITY EVALUATION i

As presented previously, the breaker for H0-1-2301-36 provides a dual safety function in that it must be able to:

1) allow the valve to open/close reliably without tripping, and 2) trip to clear a downstream short circuit I

fault to prevent the upstream feed to the MCC from tripping, 1

The following testing demonstrated that the replacement breaker would be able to provide reliable power to the valve's circuit.

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The breaker remained closed under 100 percent rated current for at least one hour with no observable detrimental effects.

The breaker remained closed at a surge current which was 9 times greater than the motor nameplate full load current.

The low'and consistent voltage drop readings of the poles at full current (averaging 126 to 149 millivolts at 25 amps) indicate that the breaker contacts are in good condition, and can supply full voltage to all three phases of the motor with minimal losses.

In addition M0-1-2301-36 is cycled to demonstrate its operability subsequent to the breaker replacement, and during monthly surveillance testing, providing additional assurance that the replacement breaker can provide the required L

electrical power to the valve.

Regarding the second safety function of the breaker, the testing demonstrated that the breaker will trip on fault currents which are a suitable margin above the anticipated normal surge currents associated with motor starting and valve seating / unseating.

Additionally, there is assurance that the breaker will successfully clear a fault by the high dielectric resistance readings (3,250 Megohms or greater) between line and load sides at 2500 volts DC. The high dielectric strength measured between poles (1,250 Megohms or l

greater) also demonstrated insulation integrity and provides assurance that' L

the replacement breaker itself will not create a fault on the MCC.

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v The results of the testing on the replacement breaker demonstrate that the breaker can be expected to perform its dual safety function.

Additionally, the valve testing routinely performed (through monthly surveillances) provides further assurance that the breaker will supply reliable power to the valve for operation, j

i EOLLON:UE_ACIIONS l'

'A new breaker (Westinghouse type HFD), traceable to the circuit breaker manufacturer, is being pursued at this time for H0-i-2301-36. As indicated previously, seismic mounting issues are presently being evaluated.

Following receipt (expected by the end of January 1990) and testing of this traceable breaker, it will be installed during the first unit outage of sufficient I

duration (not to exceed the next refueling outage).

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CONCLUSION Although the replacement breaker does not meet the requirements of Action 7 of Bulletin 88-10, the breaker has demonstrated through physical testing that it can be expected to perform its intended safety function (and support safc plant operation) until a new, traceable breaker becomes available for use.

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A11AQtlERLC i

WAD CITIES UNIT 1 y

MQLDID-CASE. CIRCUIT BREAKER REPLACEMENT Breaker Location:

480V AC Reactor Building MCC 19-1 Compt. E3 Equipment Fed:

RHCU System Return to Reactor Header Isolation M0-1-1201-80 Breaker:

General Electric Cat. No. TEC 36007 Adjustable Magnetic - only, Molded-Case Circuit Breaker I

During the current Quad Cities Unit i refueling outage, a molded-case circuit breaker (HCCB) in the above location failed a surveillance test.

The only available replacement breakers in the Commonwealth Edison Company (CECO) system were restricted from use_by Action 7 of Bulletin 88-10 (the Bullettn).

A new breaker, which meets the requirements of the Bulletin, has been ordered but cannot be obtained in time to avoid an operational impact on the unit.

One of the available replacement breakers at Quad Cities Station has successfully passed the testing delineated in the Bulletin, as well as additional Ceco testing.

Based on the results of the testing performed, the replacement breaker has demonstrated that it can be expected to support safe plant operation, j

The following paragraphs address the Breaker Failure, System Design Considerations, Replacement Breakers, Breaker Testing, Operability Evaluation and foilow-up Actions.

BREAKER FAILURE The installed breaker for motor operated valve 1-1201-80 (M0-1-1201-80) failed Quad Cities Surveillance QEMS 250-11-S1 (MCCB Environmental Qualification Inspection and Test) on September 18, 1989.

The surveillance is part of the Environmental Qualification (EQ) surveillance test program and is routinely performed on breakers in Motor Control Centers (MCCs) subject to the station's EQ Program.

The installed breaker (General Electric TEF 136M1005, 5 ampere breaker) failed the surveillance during the testing of the instantaneous trip

element.

The failure occurred when one pole of the breaker tripped when 75 percent of the instantaneous trip current (9 times the motor nameplate full load current) was applied.

SYSTEM QESIGH_COElEERATIONS The breaker supplies power to the control circuit and motor of M0-1-1201-80, kHCU Systam Return to Reactor Header Isolation.

This valve is open during operation of the RHCU System.

The breaker is normally closed during all modes of plant operation and is only opened to take the valve out-of-service.

The RHCU System at Quad Cities Station is not a l

safety-related system, nor does MO-1-1201-80 perform a containment isolation or any other safety function.

However, the valve closes under certain

' isolation signals and should be able to operate reliably without tripping the breaker.

0322k:11 J

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+ c The breaker supplies power to the. valve from a Class IE 480V AC HCC.

.The safety function of the breaker is to trip open on a downstream short circuit to prevent the upstream feed to this Class 1E MCC Bus from tripping.

As such, the breaker's interrupting rating is designed to exceed the available short circuit current, and the breaker is adjusted and tested to trip instantaneously on currents above the maximum starting currer.t of the valve motor, but below the trip setting of the MCC feed.

REf1ACEMENT BREAERS The failed circuit breaker (General Electric TEF 136H1005) is an obsolete model for which direct (like-for-like) replacements are not available. Due to this fact, CECO had previously evaluated, and approved for use, qualified replacement breakers of a later model.

In this instance, a seven ampere-breaker (General Electric TEC 36007) is the replacement for the installed breaker which failed.

However, the only available replacements in the CECO system were restricted from use by the requirements of the Bulletin.

li CECO presently has two outstanding orders which contain the replacement breaker (TEC 36007). One order, which originated prior to failure L

of.the installed breaker (TEF 136H1005), had been generated to restock the station's depleted breaker inventory.

Subsequent to the failure of the installed breaker, a second order was placed with another supplier to ensure a traceable replacement breaker (TEC 36007) is made available for installation at the earliest opportunity.- It is expected that a traceable replacement breaker will be obtained by the end of December 1989.

Quad Cities Station had two General Electric TEC 36007 replacement breakers, however, in response to the Bulletin these breakers had been h

determined to be non-traceable, and unavailable for replacement purposes.

Since these were the only replacement breakers readily available, Quad Cities Station tested one of these breakers to assess whether it could be expected to perform reliably.

RBEAKER TElilNG The replacement breaker at Quad Cities Station was tested in accordance with the applicable tests (shown below) of Attachment I to the Bulletin.

- mechanical test,

- millivolt drop test,

- rated current hold-in test,

- overload test,

- adjustable instantaneous trip test (for the maximum and minimum settings). and

- dielectric test.

l The replacement breaker passed all of the applicable Bulletin tests.

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Subsequent to the Bulletin testing, Quad Cities Station performed additional testing on the replacement breaker in accordance with station surveillance QEMS 250-11-S1 (HCCB EQ Inspection and Test).

This surveillance is performed on a MCCB prior to installation in a MCC subject to the station's EQ Program, and includes the test and adjustment of the instantaneous trip element to its installed setting.

The testing of the instantaneous trip element is based on the following two premises:

The largest load the MCCB should be expected to carry without tripping is the motor starting current plus an adequate margin for reliable operation.

The procedure defines 9 times the motor nameplate full load current as the value at which the MCCB should not trip, and 15 times the motor nameplate current as the value at which the MCCB should trip.

The instantaneous trip element of a MCCB is not manufactured as a high precision device, as supported by the tolerances (120% and 125%)

allowed by the manufacturer (and the Bulletin test requirements) at the maximum and minimum trip settings.

This has led Quad Cities Station to require a more precise method of setting the trip element to its particular installed application.

The station surveillance adjusts the MCCB to a specific trip condition point to ensure that the best match exists between providing reliable service to the equipment supplied while still providing maximum protection from downstream short circuit faults.

The surveillance (which determines the instantaneous trip current by multiplying the rated equipment current by 12) was performed in the following manner to adjust the instantaneous trip setting for the replacement breaker.

With the breaker's instantaneous trip adjustment dial at the maximum setting, a test current (42 amps), which is 15 times the motor nameplate full load current, was momentarily applied to the MCCB.

If the MCCB did not trip, the trip setting was decreased by one increment and the test repeated using the same test current.

This

" test / trip adjustment" sequence was repeated until each pole tripped upon application of the tett current.

Utilizing the instantaneous trip setting at which each pole tripped, the test current was decreased to a value which is 9 times the motor nameplate full load current (25.2 amps), and each pole was verified to remain closed upon application of the test current.

Thus, this breaker testing not cnly verified the proper operation of the' trip device, but also optimized its setting to the particular application.

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Q DEERABILITY EVALUAIION As presented previously, the safety function of the breaker for H0-1-1201-80 is to clear short circuit faults from the Class IE MCC.

The testing of the replacement breaker demonstrated that the breaker will trip on fault currents which are a suitable margin above the anticipated normal surge currents associated with motor starting and valve seating / unseating. Additionally, there is assurance that the breaker will successfully clear a fault by the high dielectric resistance readings (7,000 Megohms or greater) between line and load sides at 2500 volts DC.

The high dielectric strength measured between poles (2,400 Megohms or greater) also demonstrated insulation integrity and provides assurance that the replacement breaker itself will not create a fault on the MCC.

Another important function of the breaker for M0-1-1201-80 is to provide reliable power to the valve's circuit. Once again, the testing of the replacement breaker demonstrated this function.

The breaker remained closed under 100 percent rated current for at least one hour with no observable detrimental effects.

The breaker remained closed at a surge current which was 9 times greater than the motor nameplate full load current.

The low and consistent voltage' drop readings of the poles at full current (approximately 170 millivolts at 7 amps) indicate that the breaker contacts are in good condition, and can supply full voltage j

to all three phases of the motor with minimal losses.

In addition, M0-1-1201-80 is cycled to demonstrate its operability subsequent to the breaker replacement providing additional assurance that the replacement breaker can provide the required electrical power to the valve.

l The results of the testing on the replacement breaker demonstrate that the breaker can be expected to perform its intended safety function.

E0LLOMP__ACILONS A new breaker (General Electric TEC 36007), traceable to the circuit breaker manufacturer, has been ordered for M0-1-1201-80.

Following receipt I

(expected by the end of December, 1989) and testing of this traceable breaker, it will be installed at the first available opportunity which will not jeopardize or impact the operation of the unit (not to exceed the next refueling outage).

CONCLUSION Although the replacement breaker does not meet the requirements of Action 7 of Bulletin 88-10, the breaker has demonstrated through physical testing that it can be expected to perform its intended safety function (and support safe plant operation) until a new, traceable breaker becomes available for use.

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