ML19210A231
| ML19210A231 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/03/1975 |
| From: | Arnold R METROPOLITAN EDISON CO. |
| To: | |
| Shared Package | |
| ML19210A232 | List: |
| References | |
| GQL-1235, NUDOCS 7910240945 | |
| Download: ML19210A231 (4) | |
Text
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CONTROL NO: 9I9O FILE: INCIEE -T EEPOPT FII:-
FROM: Metropolitan Edison co DATE OF DOC DATE REC'D LTR TWX RPT OTHER Reading, Pa 7-3-75 7-7-75 XXX R C Arnold TO ORIG CC OTHER SENT AEC PDR YY DL one signed y :.NT LOCAL PDR XX CLASS UNCLASS PROPINFO INPUT NO CYS REC'D 00CKET NO:
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50-289 DESCRIPTION:
ENCLOSURES:
Ltr reporting abnormal occurrence #75-21 v
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on 6-25-75 concerning failure of a high re-a ~vu IGM, OVE' actor coolant temperature trip bistable ACKXOTLEDGED' to trip.........
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Director
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Division of Reactor Licensing 3-U.S. Nuclear Regulatory Commission s
Washington, D.C.
20555
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Dear Sir:
Docket No. 50-289 Operating License No. DPR-50 In accordance with the Technical Specifications of our Three Mile Island Nuclear S tation Unit 1 (TMI-1), we are reporting the followi
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occu rren ce.
(1) Repr*t Number: A0 50-289/75-21 cy 3
r-(2a) Report Date: July 3, 1975 7.g., C-!
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i, (2b) Occurrence Date: June 25, 1975 h'j ag s
(3)
Facility : Three Mile Island Nuclear Station Unit l
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(4)
Identification of Occurrence:
Title:
Failure of a High Reactor Coolant Temperature Trip Bistable to trip.
Type:
An abnormal occurrence as defined by the Technical Specifications, paragraph 1.8d, in that failure of a High Reactor Coolant Temperature Trip Bistable to trip constituted failure of one or more components of an engineered safety feature or plant grotection system that threatened to cause the feature or system to be incapable of performing its intended function.
(5) Conditions Prior to Occurrence:
Power:
Core: 99%
}h h 274 Elect.: 850 MWe Gross RC Flow: 140.68 x 10 lbs/hr 7180
. RC Pressure: 2155 psig RC Temp. : 379 F PRZR Level: 240 inches PRZR Temp. : 655 F (6)
Description of Occurrence:
While conducting routine surveillance of the Reactor Protection System (RPS) the Reactor Coolant Temperature Trip Bistable for channel "C" failed to trip. The remaining three RPS channels were immediately checked and found to be operable. Further, the defective trip circuit of channel "C" was then replaced and verified to be operable.
(7) Designation of Apparent Cause of Occurrence:
The apparent cause of this occurrence has been determined to be material in that the failure of the High Reactor Coolant Temperature Trip Bistable to trip was traced to a defective printed circuit board solder joint in the signal converter. This defective solder joint prevented the trip signal from reaching the trip bistable.
(8) Analysis of Occurrence:
It has been determined that this occurrence did not represent a threat to the health and safety of the public, in that a.
the high temperature trip feature of the remaining three RPS channels was immediately verified to be within Technical Specification limits, and b.
only two high temperatura trip channels are required to function for safety protection, and three were functioning properly, and c.
the failed channel was immediately replaced, tested and returned to service.
(9)
Corrective Actions:
In addition to the immediate corrective actions listed above, the defective channel "C" signal converter was repaired and tested and the results were satisfactory.
The Plant Operations Review Committee and Station Superintendent have reviewed and approved the above listed correc tive actions.
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(10) Failure Data:
Bailey System 880 Reactor Protection System Signal Converter (E92-346)
Similar Occurrences : none Sincerely, i} n Vice-President RCA:CWS:pa ec:
Mr. J. P. O'Reilly, Director Office of Inspection and Enforcement, Region 1 U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406 File 20.1.1 7.7.3.5.1 1476 276