ML17328A228

Followup Part 21 Rept Re Westinghouse molded-case Circuit Breakers Observed to Trip Before Allowable Time Band,Per Generic Ltr 88-10.Initially Reported on 891207.Breakers Purchased Prior to 1989 Purchase Order Not Subj to Problems

ML17328A228
Person / Time
Site:	Cook
Issue date:	12/12/1989
From:	Alexich M INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-89, REF-PT21-89-200-000 AEP:NRC:0971G, AEP:NRC:971G, GL-88-10, PT21-89-200, PT21-89-200-000, NUDOCS 8912200198
Download: ML17328A228 (12)

Text

RATED 31 BUTION DEMONSTR ON SYSTEM REGULATOR~ NFORMATION DISTRIBUTION TEM (RIDS) 4 ACCESSION NBR:8912200198 DOC.DATE: 89/12/12 NOTARIZED: NO DOCKET FACIL:50-315 Donald C.- Cook Nuclear Power Plant, Unit 1, Indiana 6 05000315 50-316 Donald C. Cook Nuclear Power Plant, Unit 2, Indiana 6 05000316 AUTH. NAME AUTHOR AFFILIATION ALEXICH,M.P. Indiana Michigan Power Co. (formerly Indiana 6 Michigan Ele RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Part 21 rept re molded case circuit breakers that tripped before allowable time.

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DISTRIBUTION CODE: IE19D COPIES RECEIVED:LTR ENCL SIZE:

TITLE: Part 21 Rept (50 DKT) D (

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD3-1 LA 1 0 PD3-1 PD 1 1 h GIITTERgJ. 1 1 INTERNAL: AEOD/DOA 1 1 AEOD/DSP/TPAB 1 '1 IRM TECH ADV 1 1 NRR CRUTCHFIELD 1 1 NRR VARGAiS 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OGCB11 1 1 NRR/DRIS/RVIB9D 1 1 N - 8E2 1 1 NUDOCS-ABSTRACT 1 1 EG FIL 01 1 1 RES/DSIR/EIB 1 1 R 1 1 RGN2 1 1 RGN3 1 1 RGN4 1 l.

RGN5 1 1 EXTERNAL: INPO RECORD CTR 1 1 LPDR 1 1 NRC PDR 1 1 NSIC SILVER,E 1 1 h

TOTAL NUMBER OF COPIES REQUIRED: LTTR 24 ENCL 23

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Indiana Michigan Power Company P.O. Box 16631 Columbus, OH 43216 R

AEP:NRC:0971G 10 CFR 21.21 Donald C. Cook Nuclear Plant Units 1 and 2 Docket Nos. 50-315 and 50-316 License Nos. DPR-58 and DPR-74 10 CFR 21 REPORT: WESTINGHOUSE FB3125L MOLDED-CASE CIRCUIT BREAKERS U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Attn: T. E. Murley December 12, 1989

Dear Dr. Murley:

Introduction (10 CFR 21.21(b)(3)(i), (ii) and (iii))

This letter constitutes a follow-up report, as required by 10 CFR 21.21, of information provided to your staff via telephone on December 7, 1989. This report is being submitted by Indiana Michigan Power Company, P. 0. Box 16631, Columbus, Ohio 43216. The 10 CFR 21 report concerns Westinghouse FB3125L (125-amp) molded-case circuit breakers, which have been observed to trip before the allowable time band given the time-current characteristics curve for this breaker. The subject circuit breakers were purchased from Westinghouse in 1989 to replace non-traceable circuit breakers identified in our review per NRC Bulletin No. 88-10, "Nonconforming Molded-Case Circuit Breakers."

There are five of these FB3125L circuit breakers installed in safety-related applications at the Donald C. Cook Nuclear Plant.

A 125-amp circuit breaker feeding turbine room sump pump ¹2 failed due to a loose connection. The failed circuit breaker was replaced with an FB3125L circuit breaker from stock. The new circuit breaker would not hold on starting of the sump pump. Two more breakers were drawn from stock and subsequently failed to hold on starting of the sump pump.

All three of the circuit breakers that would not hold on starting of the sump pump were purchased under the above 1989 Westinghouse purchase order. Finally, the 125-arop circuit breaker feeding turbine room sump pump ¹3 was exchanged with the circuit breaker installed in the circuit for sump pump ¹2. After exchange, the circuit breaker feeding sump 8~i a00iWS Bei2i2 PDR ADQCI( 05000315 S PNU

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Dr. T. E. Murley AEP:NRC:0971G pump ¹2 held on starting and the pump was returned to service after satisfactory testing. The circuit breaker now feeding sump pump ¹3 would not hold on starting, as had occurred during testing with the circuit breaker feeding sump pump ¹2.

After three FB3125L circuit breakers tripped while starting a turbine room sump pump, two of the three circuit breakers were bench tested at Cook Nuclear Plant. Bench testing over a range of input currents led us to conclude that both circuit breakers were tripping before the time span given by the Westinghouse time-current characteristics curve for this circuit breaker.

In order to determine whether the above problem was generic to all Westinghouse circuit breakers purchased with the 1989 purchase order, a sample of circuit breakers, including a variety of current ratings, was tested at Cook Nuclear Plant. This in-house testing indicated that the FB3090L (90-amp) circuit breakers were also tripping before their allowable time band.

Since field testing is not considered an accurate measure for determining the time-current characteristics (per NEMA standards), the circuit breakers were returned to Westinghouse for verification of our test results. On December 5, 1989, two FB3125L and two FB3090L circuit breakers were tested by the circuit breaker manufacturer at their facilities. This testing led to the conclusion that:

1) The FB3090L (90-amp) circuit breakers were performing satisfactorily.

2) The FB3125L (125-amp) circuit breakers were tripping earlier than the time band given by the Westinghouse time-current characteristics curve for this breaker.

On December 6, 1989, the results of Westinghouse circuit breaker testing was reviewed and the condition was determined to be reportable per 10 CFR 21.

The attachment to this letter shows the observed tripping times for the two FB3125L circuit breakers during Westinghouse testing. The data show that the circuit breakers tripped before the allowable time band in the range of 400t to 500% of rated current.

We can postulate two safety hazards that could be created by the above problem:

1) The circuit breaker could trip on starting of a safety-related load, precluding the accomplishment of a safety function.

2) Breaker coordination may be lost for certain fault currents.

Dr. T. E. Murley AEP:NRC:0971G Discussion (10 CFR 21,21(b)(3)(vi) and (vii))

There are five FB3125L circuit breakers from the 1989 Westinghouse purchase order installed in safety-related applications at Cook Nuclear Plant. In all cases, the loads fed by the breaker are balance of plant (BOP). Since the balance of plant loads are fed from safety-related electrical buses, the safety function of the breaker is to protect the bus from faults on the BOP loads. Therefore, tripping early is not, a safety concern at Cook Nuclear Plant. Furthermore, the five installed circuit breakers have not tripped while energizing their attendant loads. Specifically, the FB3125L circuit breakers are installed in the following applications:

Unit ~sseem Exhaust fan for auxiliary building ventilation Control air compressor Auxiliary ]acket water heater for CD diesel generator Exhaust fan for auxiliary building ventilation Freeze protection heater for refueling water storage tank Westinghouse FB3125L circuit breakers being maintained as stored spares at Cook Nuclear Plant have been placed on "temporary hold." We are pursuing resolution of the problem with Westinghouse.

Conclusion (10 CFR 21.21(b)(3)(viii))

Westinghouse FB3125L circuit breakers have been demonstrated to trip before the time band given by the time-current characteristics curve in the 400-500% rated current region. Therefore, if this breaker is used to feed a motor with a starting current in this region, the problem-described in this 10 CFR 21 report may be encountered. We believe that Westinghouse is planning to issue some form of publication to notify applicable licensees of Westinghouse findings and recommendations regarding the concern addressed by this 10 CFR 21 report.

To date, we have no reason to suspect that Westinghouse FB3125L circuit breakers purchased prior to our 1989 purchase order are sub]ect to the problem described in this 10 CFR 21 report.

Dr. T. E. Murley AEP:NRC:0971G This document has been prepared following Corporate procedures that incorporate a reasonable set of controls to ensure its accuracy and completeness prior to signature by the undersigned, Sincerely, M, P. Alexi.

Vice President MPA/eh Attachment cc: D. H. Williams, Jr.

A, A. Blind - Bridgman R, C. Callen G. Charnoff NFEM Section Chief A. B. Davis NRC Resident Inspector - Bridgman

ATTACHMENT TO AEP:NRC: 0971G TIME-CURRENT CHARACTERISTICS CURVES FOR WESTINGHOUSE FB3125L CIRCUIT BRF~ER SHOVING TRIP POINTS FOR TWO CIRCUIT BREAKERS TESTED AT WESTINGHOUSE FACILITIES

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29-161 r Page 14 AB DE-iQN Circuit Breakers @ ~p 7eSV S'lI /)T

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Types EB, EHB: 90-100 Amperes, 2 and 3 Poles Types FB, NIARK 76 Type HFB: 90.160 Amperes, 2 and 3 Poles Current In Percent of Breaker Trip Unit Rating Te'H TCr '4/5/~

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For application and coordination purposes only. Based on 40'C ambient, cold start.

Connected with four (4) fest of rated wire (60/75'C up to 100 amps. 75'C above 100 amps) per terminal. Tested in open air with cu~rent in all poles.

I Maximum Maximum Volts Minimum Breaker Ac Volts, Dc Type 60 Hz EB 240 125/250 EHB 480 250 FB, HFB 600 250 Maximum Single

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Pole Trip Times Breaker Ratings Breaker Type Continuous Amperes Instantaneous Trip, Amperes IIO

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Breaker Symmetrical RMS Amperes Dc Amps EB EH 8 10,000 18,000

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240Volts 480Volts 600Voits 250Volts 14,000 5,000 (125/250) 10,000

. F8 18.000 14.000 14,000 10,000 HF8 65,000 25,000 18,000 10.000 O~ Single pole test data at 25'C based on NEMA Procedures for verifying perfor-mance of Molded Case Circuit Breakers. 3 O

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Types EB, EHB: 90.100 Amperas, 2 and 3 Poles Types FB, MARK 75 Type HFB: 90-150 Amperes, 2 and 3 Poles Is/5/pq Current in Percent of Breaker Trip Unit Rating

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Connected with four (4) feet of rated wire iL~ L (60175'C up to 100 amps. 75'C above 100 amps) per terminal. Tested in open air with current in all poles.

. Maximum Maximum Volts Minimum' Breaker Ac Volts. Dc Type 60 Ht EB 240 )25i250 EHB 480 250 FB, HFB 600 250

, Maximum Single Pole Trip Times Breaker Ratings at 25'C(l) Breaker Continuous Instantaneous Type Amperes Trip. Amperes t EB, EHB 90 100 See Curve II

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