ML20005G459

Special Rept:On 891121,loose Parts Monitoring Sys Channel 7, Main Steam Line 252 Degrees Azimuth Found in Alert Condition & Declared Inoperable on 891130 in Order to Ensure Valid Alert Signal Could Be Detected from Other Channels

ML20005G459
Person / Time
Site:	River Bend
Issue date:	01/09/1990
From:	Booker J GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RBG-32072, NUDOCS 9001190180
Download: ML20005G459 (3)

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~ a VFR BtND STAltON , . POST OFFICE 80).120 , StJ RANO.SvlLLE. LOUISIANA 70775 -

i AREA CODE bo4 ' ' 636 6094-3' 346 8651 E,

p' January 9,1990

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, - UU S': Nuclear. Regulatory Commission

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I' Gentlemen:'- . -

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< River Bend' Station - Unit'1'

' Docket No. 50-458 '

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~ Enclosed Iis Gulf 2S' t ates' Ut111 ties Company's Special Report o, concerning~ an; inoperative' 1oose-part detectf on system channel'at

,' River Bend -Station.~ This report is being submitted, pursuant to RiverJBend Station-Technical Specification 3.3.7.9 and'6.9.2.

A _ Sincerely, L i g J. E' Bookdr Manager-River Bend-Oversight  !

. River Bend Nuclear Group

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JEB/TFP W/DNL/DC N /ch c'c : U. S. Nuclear Regulatory Co'mmission=

Region IV 1 611 Ryan Plaza Drive, Suite:1000 3 0 ,

. Arlington, TX 76011 1 NRC. Resident Inspector Post Office Box 1051  ;

7; St. Francisville, LA 70775 r

Enclosure 9001190180 900109 PDR ADOCK 05000458 S PDC b \\

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'SPECIAL REPORT l t

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Reported-Condition. 4

0n November 21, 1989,. the loose ~ parts monitoring (LPM) system channel 7, main; steam line 252 degrees azimuth, was found in an alert condition by Operations.

Since the loose part annunciator is common to the eight LPM channels,'the constant alarming of LPM-7 may have prevented any alert signal generated by-the: remaining seven (7). channels.from being detected by plant operations-

. personnel. -To ensure'that a valid alert signal from the other LPM channels could be' detected, the hi-alarm on channel 7 was disabled and declared n '

. inoperable in accordance with Technical Specification 3.3.7.9 on November 30,

/ 1989. This Special Report-is hereby submitted pursuant to Technical ,

Specification 3.3.7.9.

Investigation ,

Following the discovery'of the problem, signal plots were collected and

, transmitted to the-system vendor, Babcock & Wilcox'(B&W) for review. Based on these plots, B&W concluded the signals were not a~ result of a valid loose part inside the vessel and suggested raising the setpoint of this channel to

' eliminate the nuisance alarm. In addition, GSU's troubleshooting efforts has-verified that the LPM-7 detector's electronic circuits are satisfactory.

During a planned outage (P0.89-02), a drywell entry was made which allowed '

verification that the channel 7 sensor and it's mounting strap were secure. ,

During-the subsequent startup, the channel 7 alarm started coming-in when reactor power reached approximately 80 percent. The frequencies observed varied _and.had no. apparent relationship-to other plant parameters; Additionalsignallplotswereobtainedduringthe'startupatdifferentreactor-power levels and were sent to B&W for. review. Again,-B&W does not believe the signals were caused by a loose part, as all the impact signals contain a 2.2 KHz- resonant- frequency, which could be caused- by steam flow noise. A metal to

metal impact would generally excite many different frequencies instead of only one: frequency.

lCorrectiveAction

'GSV Engineering is evaluating recommendations from B&W to raise the channel 7

-setpoint and widen the filter frequency range to include 2.2 KHz. A permanent

-setpoint change will be implemented to restore the channel to an operable condition by March 31, 1990. The final corrective actions to restore channel operability will be reported in a supplement to this report by April 30, 1990.

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- Since? the signal' plots- reviewed by the vendor have indicated that the signals

,-- ' from the LPM-7Jchannel contain a 2.2 KHz resonant frequency and not multiple

. frequencies typical of metal-to-metal: impact, GSU concludes that these signals.

lare not due to loose parts-inside'the vessel.' The alarming channel (LPM-7)

has- been disabled and. declared -inoperable per Technical Specification 3.3.7.9~'

'(Thus, a legitimate alert signal from any of-the remaining channels can be detected by> the common annunciator. Therefore, the health and safety of the public:and safety;of the plant _are not adversely affected..

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