ML20236B588

Special Rept:On 870610,loose Parts Monitoring Sys Channels Went Into Alarm & Could Not Be Reset.Caused by Flow Noise from Reactor Recirculation Sys Flow Control Valve in Throttled Position.Alarm Temporarily Disabled

ML20236B588
Person / Time
Site:	Clinton
Issue date:	07/17/1987
From:	Spangenberg F ILLINOIS POWER CO.
To:	Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
NUDOCS 8707290163
Download: ML20236B588 (2)

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ILLINDIS POWER 00MPANY July 17, 1987 hCFR5b 6# cm>( Uu113G 1

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Docket No. 50-461 ci l

Mr. A. B.. Davis b Regional Administrator FILE _QQ, Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois '60137

Subject:

Special Report: Loose Parts Monitoring System Out of Service

Dear Mr. Davis:

I Requirement )

On June 10, 1987, one of the Loose Parts Monitoring System (LPMS) channels went into alcrm and could not be reset. It was determined that l this alarm was not caused by a loose part. With this channel in alarm, it masked any alarms from other channels and prevented the entire system e from passing its required surveillance. At 2212 on June' 10, 1987, the: '

system was declared Anoperable. On July 10, 1987, the Limiting Condition for Operation expired. Clinton Power Station (CPS) Technical Specification 3.3.7.10 requires that if one or more channels of the.LPMS is inoperable for more then 30 days, a report shall be sent to the Commission pursuant to Specification 6.9.2, SPECIAL REPORTS, within 10 days. This report is written in accordance with Regulatory Position C.5.A.b of Regulatory Guide 1.133.

Cause of Malfunction The LPMS was declared inoperable when the channel 4 monitor,.

loceted on the discharge piping for the "B" recirculation loor, alarmed and could not be reset. Troubleshooting and calibration of the system determined it was functioning correctly _ The instrument output was evaluated by the Nuclear Station Engineering Department (NSED) and the-equipment manufacturer (Rockwell). This evaluation determined'that the cause of the alarm was not due to a loose part, but a result of flow

l. coise from the Reactor Recirculation System flow control valve which was l in a throttled position. This evaluation is based on _no impact noises being detected and no signs of impact on the strip chart recordings.. .

Also, similar phenomena were noted at other plants while throttling the

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Reactor Recirculation System flow control valve.

8707290163 M 870717 s ADOCM 0500 1 JUL 2 2 1987

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- I Plans to Restore System to Operational On July 15, 1987, a Temporary Modification was initiated to disable ~

the alarm function for the channel 4 monitor. This will allow the other 5 channels to alarm in the Main Control Room if the alert level is I reached. However, these actions will not allow the system to meet the Technical Specification definition of operable.

NSED is working with Plant Staff and the equipment manufacturer to prepare a Plant Modification to restore this equipment to operable i status. Currently no Plant Modification has been completed. A l supplemental report describing the Plant Modification used to restore l the LPMS to operable status will be submitted when the Plant i Modification is complete.

Additional Information l No LPMS Alert Level alarms were detected when the Enactor Recirculation System was operating with the pumps in slow speed. The equipment manufacturer stated that past experience indicates that the high levels of background noise currently experienced will diminish as the flow control valve is opened. It is anticipated that when the flow control valve position is between 65% and 75% open, the background noise will reduce sufficiently to clear the alarm. j If there are any questions on this matter, please contact me.

Sincerely yours, ck- ]

i F. A. Spangenbe g, III Manager - Licensing and Safety GSL/ckc cc: B. L. Siegel, NRC Clinton Licensing Project Manager NRC Resident Office Illinois Department of Nuclear Safety Document Control Desk i

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