05000289/LER-1977-011, Forwards LER 77-011/01T.Provides Supplemental Info

Forwards LER 77-011/01T.Provides Supplemental Info

ML19210A253
Person / Time
Site:	Crane
Issue date:	06/02/1977
From:	Herbein J METROPOLITAN EDISON CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19210A254	List: 05000289/LER-1977-011, Forwards LER 77-011/01T.Provides Supplemental Info 05000289/LER-1977-011-01, T:On 770519,engineered Safeguards Motor Control Center Tripped During Power Operation.Caused by Binding of a Phase Overload Device Tripping Stem.Preventive Maint Will Be Modified to Check for Tripping Stem Resetting
References
GQL-0764, GQL-764, NUDOCS 7910250476
Download: ML19210A253 (4)

LER-1977-011, Forwards LER 77-011/01T.Provides Supplemental Info

Event date:
Report date:
2891977011R00 - NRC Website

text

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'"NCIbTREPORT NRC DISTRIBUTION FOR PART 50 DOCKET MATERI AL I

FROM: METROPOLITAN EDISON CO.

DATE OF DCCUMENT TO: J.P.0' REILLY READING, PA.

A17/77 J.G. HERBEIN oATE RECEIVED 6/11/77 M TTER ONOTORIZED PROP INPUT FORM NUMBE R OF COPIES RECEIVEC Rl GIN AL NCLASSlFIED

DESCRIPTION

ENCLOSU RE LTR. TRANS THE FOLLOWING.........

LICENSEE EVENT REPORT FOR R.O.# 77-11/1T, ON 5/19/77 CONCERNING THE "B" ENGINEERED SAFEGUARDS MOTOR CONTROL CENTER TRIPPED DUE TO A MECHANIC /st

'D0 NOT REMOVE 8gmgG0FTHETRIPPINGSTEMON!HEOVERLOAD.

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PIANT NAME: THREE MILE' ISLAND # 1

.SAB NOTE: IF PdRSuhNEL EXPOSURE IS INVOLVED ACKNOWLEDGED 8'""""'"'

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, FOR ACTION /INFORMATION BRANCH CHIEF:

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Wif.,fe"J no au ocnss METROPOLITAN EDISON CCMPANY POST OFFICE BGX 542 READING, PENNSYLVANI A 19603 TELEPHONE 215 - 929-0601 June 2, 1977 GQL 076L lEGUE0!!Y D0c.4EIFRE C0p]

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Mr. J. P. O'Reilly, Director g

Office of Inspections and Enforcement, Region 1 Il,g gf

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031 Park Avenue 40 q,.

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Dear Sir:

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Operating License :To. sPR-50 In accordance with the Technical Specifications of our Three Mile Island Nuclear Station Unit I (TMI-1), we are reporting the follcwing reportable occurrence.

(1) Report :iumber: 77-ll/lT (2a) Required Report Date: 06-02-77 (2b) Date of Occurrence:

05-19-77 (3) Facility: Three Mile Island IIuclear Station - Unit I (h) Identificatien cf Occurrence:

Title: Engineered Safeguards Motcr Centrol Center Tripped During Power Operation Type: A reportable occurrence as defined by Technical Specification 6.9 2.A.(2) in that, the 13 l'ngineered Safeguards Motor Centrol Center Tripped during power operaticns, thus, leading to cperation of that system with a parameter subject to a limiting ecndition for operation less conservative 'han the least conservative aspect cf that limiting ecndition for operaticn established in Technical Specification 3.7.2.F.

1 A76 A6 7716'W N

J. P. O'Reilly 6/2/77 GC; 076h (5) Condition Prior to cecurrence:

Power:

Core 18GO 'S d 75',1 Elec. 620 MWe RC Plow:

ikk x 106 RC Pressure:

2170 psi __

RC Temp:

580 PPZR Level:

219 inches PRZR Temp:

655cy (6) Description of Occurrence:

While attempting to start the 13 'nctrument Air Cc= pressor (IA-P-13), the feeder breaker to the 13 Engineered Safeguards Motor Control Center tripped. The =0 tor centrol center breaker apparently tripped incorrectly due to the air compressor =ctor starting current.

The motor control center was out of service for approximately eleven (11) minutes resulting in a violation of Technical Specification 3.7.2.f.

(7) Apparent Cause of Occurrence:

The cause of this occurrence has been determined to te material in that the tripping stem en the A phase overload device was binding.

When the current through the breaker exceeds the long delay pickup setting, the tripping stec =cves up tavard the trip bar.

If current is reduced before the tripping stem reaches the trip bar, the breaker will not trip and the tripping stem should return to its " reset" positicn. Mechanical binding prevented the A phase device from reset-ting cn the feeder breaker to 13 ES MCC.

The motor current inrush frem starting IA-P-13 caused the total current to exceed the icng delay pickup cetting ot 1000 anpc and the overlcad device trip.jed the breaker before the starting current de-creased.

(8) Analysis of Occurrence:

The 13 ES MCC being cut of service resulted in a losc of re-dundancy en scme Engineered Safeguards equiptent. Adequate redundant equipment was available to provide the required safeguarco functicns in the event of an accident.

3cced on the short time the 13 ES MCC was cut of service, and the ava.alability of redundant equipment, it is concluded that the event did not result in a threat to the health and safety of the public or to station personnel.

(It should be noted that the ES lcada ccnstitute a small pcr-tion of the lead on the 13 ES CC.

It is unlikely that block loading would have caused the breaker to trip. )

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G;l 0762

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J. P. O'Reilly 6/2/77

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(9) Corrective. Action:

DSEDIATE: A visual inspection was made in an attempt to deter-mine the cause for the trip. No apparent faults were observed and the

=ctor control center was re-energized. The normal leads frc: the

=ctor control center were re-energized (except for the 13 Instrument Air Cc pressor).

LONG TERM:

1.

The 13 Instrument Air Cc presscr motor was tested to verify that no faults were present.

2.

Visual inspection of the 13 ES MCC feeder breaker indicated an overload device tripping ste: nct fully reset.

(With the tripping ste: not reset the breaker could trip in less than the required time if current were abcVe the pickup value.)

The =ctor control center was removed frc service for a short period of time to permit removal of the suspect breaker for test-ing.

The breaker was replaced with a tested spare.

3 Testing of the breaker removed frc service confirmed that the tripping ste: was binding on the A phase overicad device.

Scre binding was also noted on the C phase device.

h.

The preventive maintenance procedure will be =cdified to include a chec'- for the tripping ste resetting.

The Plant Cperations Review Cc ittee and Unit Superintendent have reviewed and approved the above ccrrective action and have taken steps to assure its cc=pletion.

(10) Failure Data:

Wectinghouse DB 50 Circuit 3reaker 1600 Amps, 600 V AC Series overcurrent trip device 1000 Arp, 60 cycle, #2hX6h5883

Similar Events

Th-26 13 ES "00 Tripping Sincerely,

/

J. G. Herbein Vice President JCH:DGM:js nnc10 sura 74censee 37 ant Pe o +.

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