ML19261F219

RO 76-38/3L:on 761027,during Surveillance Procedure 1303-4.1 High Reactor Coolant Temp Trip Bistable for Channel C Failed to Trip at Required Setpoint.Caused by Dirty Connector on Bistable Module Causing in Higher Connector Resistance

ML19261F219
Person / Time
Site:	Three Mile Island
Issue date:	11/12/1976
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
GQL-1570, NUDOCS 7910250639
Download: ML19261F219 (4)

Text

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METROPOLITAN EDISON COMPANY : . -r=-_- - --

POST OFFICE BOX 542 RE ADING. PENNSYLVANI A 19603 TELEPHONE 215 - 929-2601 November 12, 1976 .

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Mr. J. P. O'Reilly, Director Office of Inspection and Enforcement, Ragion 1 U. S. Nuclear Regulatory Co==ission 631 Park Avenue King of Prussia, Pennsylvania 19h06 -

Dear Sir:

Docket No. 50-289 -

Operating License No. DPR-50 In accordance with the Technical Specifications of our Three Mile Island Nuclear Station Unit 1 (TMI-1), we are reporting the following reportable occurrence.

(1) Report Number: 76-38/3L (2a) Required Report Date: Novemb er 26, 1976 (2b) Date of Occurrence: October 27, 1976 (3) Facility: Three Mile Island Nuclear Station, Unit I (h) Identification of Occurrence:

Title:

Failure of the High Reactor Coolant Temperature Trip 31stnble to Trip During a Test.

Type: A reportable occurrence as defined by Technical Specification 6.9.2.B.(1) in that the high reactor coolant temperature trip bistable for Reactor Protection System (RPS) Channel "C" failed to trip at the required setpoint, thus leading to the RPS instrument settings being less conservative than those established by the technical specification, as listed in Table 2.3-1, but not preventing the fulfill =ent of the functienal requirements of the system.

(5) Conditions Prior to Occurrence:

Power: Core: 2531 Wt x ... U u O Elec.: 851 W Gross RC Temp.: 579CF

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Mr. J. P. O'Reilly hs Report Number 76-36/3L .

RC Flow: lho x 106 lbs/hr RC Pressure: 2155 psi PRZR Level: 225 inches 0

PRZR Temp.: 650 F (6) Description of Occurrence:

At 9:00 on October 27, 1976, while conducting routine testing per Surveillance Procedure 1303 h.1, " Reactor Protection System Surveillance",

the high reactor coolant temperature trip bistable for RPS Channel "C" failed to trip at the required cetpoint as listed in Table 2.3-1 (Page 2-9) of the Technical Specific itions.

TABLE 2.3-1 ACTUAL TRIP CHANNEL BISTABLE Maximum Trin SETPOINT C High Temperature 619 F 620.807 I= mediate investigation shoved that the bistable adjustment was proper, and cleaning of the connectors on the bistable module eliminated the problem. The applicable section of 1303 h.1 was repeated and the bistable tripped within Technical Specification limits. The high reactor coolant temperature trip setpoint for the remaining three (3)

RPG Channels was checked and verified as being within Technical Specification limits.

(7) Designation of Apparent Cause of Occurrence:

The cause of this occurrence has been determined to be material in that a dirty connector en the bistable =cdule resulted in a higher than normal connector resistance.

(8) Analysis of Occurrence:

It has been determined that the failure of the high reactor coolant temperature trip bistable to trip at the required setpoint did not constitute a threat to the health and saf ty of the public since the high te=perature trip feature for the rr c2ining three (3) RPS Channels was checked and the bistables were fcur. to trip within Technical Specification limits.

(9) Corrective Action:

In additien to the i= mediate action described above, the connectr.- problems are currently being discussed with the vendor to determine whether the present cleaning practices are acceptable.

The Plant Cperations Review Ccemittee and " nit Superintendent have reviewed and approved the abcVe corrective act .on and have taken steps i

to assui its completien.

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Mr. J. P. O'Reilly Report himber 76-38/3L -

(10) Failure Data:

Bailey Meter Co.

Blue Ribbon Connector Part No. 691371A1 Similar Events:

None Sincerely, t

R. C. Arnold Vice President RCA:DGM:tas G

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