ML19261F243

Environ Rept 76-30/3L:on 760901,associated Control Rod Drive Breaker in Reactor Protection Sys C Failed to Trip,Leading to Operation in Degraded Mode.Caused by Linkage Binding Due to Dirt or Hardened Grease

ML19261F243
Person / Time
Site:	Three Mile Island
Issue date:	10/01/1976
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
GQL-1376, NUDOCS 7910250668
Download: ML19261F243 (4)

Text

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U.S. NUCLE A R R E GULATOR Y C' t G310N DOCKET NUM BE f t (2 70s 50-289-NFC DISTRIBUTION FOR PART 50 DOCKET MATERI AL "77"NbT CI - REFORT ,

To: J.P 0"REILLY FROM: METROPOLITAN EDISON CO.* OATE Cr DOCUVENT READING, PA. 10-1-76 R.C. ARNOLD _ oATE nECEivEo 10-13-76 ELETTER OnoTonizEo enoP INPUT FORM NUMBER OF COPIES RECEIVED

@RIGIN AL QUNCLASSlFIEo CCcPy 1 DESCRIPTION ENCLOSU RE LTR.PROVIDING REPORTABLE OCCURRENCE # 76-30/3L OTc.9-1-76, CONCERNING THE FAILURE OF CONTROL RCD DRIVE BREAKER TO TRIP ON A REACTOR PROTECTION SYSTEM TEST SIGNAL'.......

ACKNO R EDGED

( 1 SIGNED CY. RECEIVED)

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Mr. J. P. O'Reilly, Director -p i - i Office of Inspections and Enforce lent,JitegiO -

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Docket No. 50-289 Operating License No. DFR-50 In accordance with the Technical Specifications of our Three Mile Island Nuclear Station Unit 1 (CG-1), we are reporting the following reportable cccurrence.

(1) Report Number: ER 76-30/3L (2a) Required Report Date: October 1, 1976 (2b) Date of Occurrence: September 1, 1976 (3) Facilicy: Three Mile Island Nuclear Station - Unit I (h) Identification of Occurrence:

Title:

Failure of Control Red Drive Breaker to trip on a Reacter Protection Systen Test signal.

Type: A reportable occurrence as defined by Technical Specifications 6.9 2.3 (2) in that while performing routine surveillance testing on Reactor Protecticn System (RFS) Channel C, one (1) of the associated Centrol Rod Drive (CRS) Ereakers failed to trip leading to operatien in a degraded =cde permitted by a limiting condition for operation as defined by Technical Specificaticn 3.5.1.6 leas:

Mr. J. P. O'Reilly, Director GQL 1376 (5) Ccnditions Prior to Occurrener-Power: Cere: 98.5 Elec: 838 MWe RC Flcv: 139 x 106 lbs/hr RC Pressure: 2180 psig RC Te=p: 5790F FRZR Level: 230 in.

PRZR Te=p: 650 F (6) Description of Jecurrence:

At 0110 hours0.00127 days <br />0.0306 hours <br />1.818783e-4 weeks <br />4.1855e-5 months <br /> en Septe=ber 1, 1976 while performing surveillance Procedure 1303 h.1 en RPS Channel C, one of the associated CRD Breakers (CB-2) failed to trip.

Inmediately the failed breaker was tripped within the required thirty (30) minutes. The failed breaker was exercised, retested and returned to service. The remaining trip breakers were then tested within the eight (8) hear time allotment.

(7) Designation of Apparent Cause of Occurrence:

The cause of this cccurrence has been determined to be material in that dirt or hardened grease appeared to bind the operating linkage. The under voltage device was replaced to preclude the possibility of a weak spring in the UV device. Satisfactory operation was achieved after cleaning and lubricating the linkage and rechecking the latch adjust =ent.

(8) Analysis of Occurrence:

It has been determined that this occurrence did not constitute a threat to the health and safety of the public. Although the failure cf the breaker to trip resulted in a less of redundancy, it would not have prevented a reactor trip.

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4 Mr. J. P. O'Reilly, Director GQL 1376 (9) In addition to the i==ediate action described above, trip tests for CE-2 as outlined in the operating procedure will be performed bi-monthly for a period of six months.

The Plant Operations Review Co==ittee and Station Superintendent have reviewed and approved the abcve corrective action and have taken steps to ensure its implementation.

Sincerely, f

't R. C. u old Vice President RCA:DGM:rk

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