ML17173A289

Forwards LER 78-055/01T-0

ML17173A289
Person / Time
Site:	Dresden
Issue date:	10/13/1978
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML17173A290	List: ML17173A289 ML20027A180
References
NUDOCS 7810200092
Download: ML17173A289 (3)

Text

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Commonw._. Edison Dresden R.R. #1 Nucle~wer Morris, Illinois 60450 Telephone 815/942-2920 Station October 13, 1978 BBS Ltr. #78-1368 James G. Keppler, Regional Director Directorate of Regulatory Operations - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137.

Reportable Occurrence Report #78-055/0lT-O, Docket #050-237 is hereby submitted to your office in accordance with Dresden Nuclear Power Station Technical Specification 6~6.B.l.(e), failure or malfunction of one or more components which prevents or could prevent, by itself, the fulfillment of the functional requirements of system(s) used to cope with accidents analyzed in the SAR.

Station Superintendent Dresden Nuclear Power Station RBS/deb Enclosure cc: Director of Inspection & Enforcement Director of Management Information & Program Control File/NRC REGU\AlORY DO&Kll fl\! COPY

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! @IIJ I While performing DOS 2300-3 (HPCI Turbine Quarterly Surv.) the HPCI turbine tripped i *.

CIITI. o~ low pump suction pressure of 11.*S psig which exceeds the Dresden setpoint of 9. 4 ITE ib. Hg vacuum increasing. Safety significance was reduced since redundant Isolation CQTIJ Condenser and Auto* Depressurization Systems were operable. No previous similar I C§]IJ events at Dresden. I

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J The cause was attributable to instrument drift of pressure switch PS *2-2360._~T~h_e"------'

switch was recalibrated to trip at -9.4" Hg increasing. The switch will be checked in tw~ months to ensure its continued acceptability.

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ATTACHMENT TO LICENSEE EVENT REPORT 78-055/0lT-0 COMHONWEALTH EDISON COMPANY (CWE)

DRESDEN UNIT-2 (ILDRS-2)

DOCKET ff 050-237 While conducting the HPCI Turbine Quarterly Surveillance DOS 2300-3, the HPCI Turbine tripped on low pump suction pressure sensed by pressure switch PS-2-2360. The switch tripped at 11.5 psig which is considerably above the Dresden setpoint of 9.4" Hg vacuum increasing. The safety significance of the event was reduced since the redundant Isolation Condenser and Automatic Depressurization Systems were operable.

In the surveillance procedure, normally closed MO valves 2-2301-14 (Flow to Torus), 2-2301-10 (Flow to 2/3B Contaminated Condensate Storage Tank), and 2-2301-49 (HPCI bypass iine) are all opened and the HPCI turbine is started against little backpressure. Using a temporary procedure change, valve 2301-10 was closed to restrict the pumps discharge and HPCI started normally. Valve' 2301-10 was subsequently throttled and proper flows and pressures were obtained to satisfactorily demonstrate operability in accordance with the surveillance requirements.

However, after subsequent management review on the next normal working day, it was concluded that HPCI might not have been operational under all accident conditions and should have been reported inoperable in accordance with Technical Specifications 6.6.B.1.e.

The cause of the trip was instrument drift of PS2-2360. The switch was

. recalibrated to trip at 9.4 inches Hg vacuum in:::reasing. These switches have been calibrated each refueling outage in the past, and a review of records indicates no unusual tendency for excessive drifting of the switch setpoints. The switch will be checked in two months to ensure its continued acceptability.

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