ML19308A500
| ML19308A500 | |
| Person / Time | |
|---|---|
| Site: | Three Mile Island  |
| Issue date: | 06/03/1974 |
| From: | METROPOLITAN EDISON CO. |
| To: | |
| Shared Package | |
| ML19308A499 | List: |
| References | |
| NUDOCS 7910250700 | |
| Download: ML19308A500 (2) | |
Text
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_N'1 ..: ABNORMAL OCC1)RRENCE REPORT
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- 1. Report No. .
.' '50.-220/74-8 t2a. .Date . ' . ./ June.3,~1974 2b. Occurrence Date '
iMay 31, 197,4
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.3. Facility ,
.Nine Hile Point Nuclear Station Unit 1
/4. Ident'ification of Occurrence DhQO '
5etpcint drift on Drywell High Pressure ,, hgg l
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- Conditions Prior to Occurrence M3 T '
- Unit .1 was shutdown for annual refueling
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- 26. Descriptien of Occurrence During routine surveillance testing en May 31., Ic74 at approximately 1600 hours, two Barton Instru:ents used in the trywell High Pressure
-(3.5 psig) RPS were found to ha' v e drifted .'20 'ssi. higher than required. ,
'The surveillance test consists of operating the switch thru regulated
'(tercury cancreter) air signal to 'the sensor. The two Barten Instruments
>Hodel 289,.E.P. 8RE04A4D are in separato RPS trip systems. ,
- With reactor in refuol mode and the drywell under atmospheric conditions v no operator action was necessary, as the plant was in a safe condition.
- 7. ' Designation of Accarent Cause of the Occurrence Setpvint. drift ,- -
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- 8. : Analysis of occurrence ,
'The high drywell pressure trip requires a ono.out of two twice logic to. actuate the protective function. One channel in each trip systen
'would havo actuated at the required setpoint and thus produced the
. protective function. Therefore,.no hazard would have been presented l to the general public or station had the protective function been srequired.
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.9. . Corrective Action The im=ediato co rective action involved recalibration of the Barton
. switch. The normal valvo of setpoint is 3.S + .053 psig. A modif-ication has been made to the Barton switch. I'new switch plate lacking device to prevent setpoint drift has been installed. (AOR 74-1) . This modification should reduce setpoint drift problems with this switch.
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- 10. - Fallure Data - ..w ,- .
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'. iNo previous setpoint drifting has cccurred on these switches this
.. .Eyear. AOR 74 '1 concerning a Barten switch setpoint drift is the only
.fother drift in setpoint taidate.in
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1974.
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