ML19327C065

LER 89-005-00:on 891006,intermediate Range High Level Trip Signal Unexpectedly Generated During Course of Routine Source Range Channel Calibr.Caused by Loose Connection of Input/Output Cable.Connection tightened.W/891106 Ltr

ML19327C065
Person / Time
Site:	Point Beach
Issue date:	11/06/1989
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-89-139 LER-89-005-01, LER-89-5-1, VPNPD-89-578, NUDOCS 8911150188
Download: ML19327C065 (3)

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I J' VPHPD-89-578 NRC-89-139 November 6, 1989 U. S. NUCLEAR REGULATORY COMMISSION L Document Control Desk Mail Station P1-137 Washington, D. C. 20555 Gentlemen EQgEET 50-301 LICENSEE EVENT REPORT 89-0005-00 INTERMEDIATE RANGE HIGH FLUX TRIP SIGNAL POINT BEACH NUCLEAR PLANT, UNIT 2 Enclosed is Licensee Event Report 89-005-00 for Point Beach Nuclear Plant, Unit 2. This report is provided in accordance with 10 CFR 50.73 (a) (2) (iv) , "Any event or condition that resulted in the' manual or automatic actuation of any

, engineered safety system including the reactor protection system." ,

This report describes a reactor trip signal. The trip signal l was a result of an unexpected intermediate range high flux l signal caused by a loose connection while the unit was shut '

down for refueling.  ;

If you have any questions regarding this LER, please contact us.

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l. Very truly yours,

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, C. W. Fay l Vice President  ;

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} uo l l l On October 6, 1989, at 10:02 a.m., while in the refueling shutdown with the reactor trip breakers open, an intermediate range high level trip signal was unexpectedly generated during the course of a routine source range channel calibration.  !

Subsequent investigation revealed a connection for the input / output cable to intermediate range channel N35 power supply NQ203 was ,

approximately 3/4 turn loose. Power supply NQ203 feeds the ,

intermediate range bistable.

The connection was tightened and the connections for the remaining intermediate range and source range detectors were checked. The cther connections for this unit checked " tight." A Maintenance Work Request was issued to complete the investigation and check the tightness of intermediate and source range connections on Unit 1 after the refueling shutdown in spring 1990.

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01 0 O! 2 012 DESCRIPTION OF OCCURRENCE:

Unit 2 was shut down for its annual refueling and maintenance outage. On October 6, 1989, at 10:02 a.m., with the reactor trip breakers open, an intermediate range high level trip signal was unexpectedly generated during the course of a routine source range channel calibration. The equipment that is required to operate when the trip signal is generated operated as expected. '

APPARENT CAUSE OF THE OCCURRENCE:

Subsequent investigation revealed the connection for the input / output '

cable to the intermediate range channel N35 power supply NQ203 was approximately 3/4 turn loose. Power supply NQ203 feeds the inter-mediate range bistable. It is believed that a momentary open and reclosed circuit at the described connection caused the trip signal to be generated.

IMMEDIATE CORRECTIVE ACTION:

The connection was tightened and calibration was completed. This intermediate range was found to be in calibration. The remaining intermediate range and source range connections for Unit 2 were checked for tightness. No other loose connections were discovered.

CORRECTIVE ACTION:

A Maintenance Work Request was issued to check the intermediate range power supply cables involved and complete the investigation of the connections. A Maintenance Work Request was also issued to verify connection tightness for the Unit 1 intermediate range power supply cables after the spring 1990 refueling shutdown.

SAFETY ASSESSMENT:

There were no safety implications to the public because the unit was shut down. Nonetheless, the trip signal was inadvertently generated and all equipment required to operate, that had not been procedurely disabled for the outage, operated. This is the first occurrence of this type at Point Beach.

REPORTABILITY:

This report is submitted in accordance with the requirements of 10 CFR 50.73 (a)(2)(iv) which requires reporting of any event or condition that resulted in manual or automatic actuation of any engineered safety feature.

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