ML20214U069

Special Rept 87-006:on 870429,seismic Monitoring Instrumentation Channel Declared Inoperable & Remained Out of Svc for More than 30 Days.Caused by Faulty Voltage Regulating Printed Circuit Board.Board Will Be Replaced

ML20214U069
Person / Time
Site:	Wolf Creek
Issue date:	06/05/1987
From:	Withers B WOLF CREEK NUCLEAR OPERATING CORP.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
87-006, 87-6, WM-87-0161, WM-87-161, NUDOCS 8706110036
Download: ML20214U069 (3)

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WfjLF CREEK NUCLEAR OPERATING CORPORATION Bart D. Wethers Pres M and Chef Execumve ofacer June 5,1987 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington D.C. 20555 Letter: WM 87-0161 Re: Docket No. 50-482 Subj: Special Report 87-006 Gentlemen:

The enclosed Special Report is submitted pursuant to Technical Specifications 3.3.3 3 and 6.9.2 concerning inoperable seismic monitoring instrumentation.-

Very truly yours, U-1A Bart D. Withers President and Chief Executive Officer l BDW:jad j Enclosure l

cc: P0'Connor (2)

RMartin l JCummins t

i 8706110036 870605 PDR ADOCK 05000482 S PDR h

P.O. Box 411 / Burlington, KS 66839 / Phone: (316) 364-8831 I m-, E e,,mcm \

WOLF CREEK GENERATING S1RTION SPECIAL REPORF 87-906 INOPERABM SEISMIC MONITORING IIETRIBENIRTION On April 29, 1987, at approximately 1515 CDT, a seismic monitoring instrumentation channel was declared inoperable. This Special Report is being subnitted pursuant to Technical Specifications 3.3.3.3 and 6.9.2 due to the channel remaining out of service for more than thirty days.

During the performance of surveillance procedure STS IC-894, " Channel Calibration Triax Time Ilistory and Response Spectrum Recording System", the triaxial Strong Motion Accelerometer (0-SG-AE-3) on the outside wall of the reactor support structure was determined to be inoperable. During testing of 0-SG-AE-3, the accelerometer output signal remained constant regardless of the applied input test voltage.

Extensive troubleshooting of the monitor has not yet been possible due to the monitor's location. The accelerometer is mounted on the exterior side of the reactor cavity west wall at elevation 2013'-4" within the Biological Shield Wall. It is postulated that the source of the malfunction is a faulty voltage regulating printed circuit board comnon to the three ditectional acceleroneters located internal to 0-SG-AE-3.

The Strong mtion Accelerometers (SMA) are part of the Seismic Instrumentation System and are not required for the safe shutdown of the plant, but it does provide information that could indicate that a shutdown is necessary.

Triaxial Strong Motion Accelerometers (total of six) are installed at appropriate locations to provide data on the frequency, amplitude, and phase relationship of the seismic response. Data from the Strong mtion Accelerometers are fed into the spectrum analyzer. located in the Control Room to produce earthquake spectra innediately following an earthquake.

Three SMA's are located in the Reactor Building:

on the containment base slab (0-SG-AE-1);

• on the Containment Building at the operating floor level (0-SG-AE-2),

above and axially aligned with the SMA on the base slab;

• on the outside wall of the reactor support structure (0-SG-AE-3) .

In addition, as part of the seismic Instrumentation System in the Containment Building, Peak Recording Accelerographs (PRA) are provided to record the peak acceleration experienced during seismic event. Three PRA's are located in the Reactor Building:

on the containment of elevation 2119' (0-SG-AR-5);

on the steam generator C support at elevation 2047' (0-SG-AR-8);

• on the Reactor Coolant System Icop 2 cross-over leg piping at elevation 2006' (0-SG-AR-7).

Page 1 of 2

Wolf Creek Generating Station Special Report 87-006 Page 2 of 2 Based on the above, even with SMA O-SG-AE-3 inoperable, the remaining

- Seismic Instrumentation System will still provide sufficient capability to promptly determine the magnitude of _ a seismic event which is needed to evaluate whether a plant shutdown is required.

It is currently planned to replace this printed circuit board during the next refueling outage. If this replacement does not serve to restore O-SG-AE-3 to operable status, further troubleshooting and corrective actions will be performed at that time.

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