RBG-24546, Special Rept:On 870724,seismic Monitor 1ERS-NBE1B Declared Inoperable When Surveillance Interval Expired Per Tech Spec 4.0.3 & Action Statement Entered.Monitor Will Still Register Seismic Events.No Such Events Have Occurred at Facility

Special Rept:On 870724,seismic Monitor 1ERS-NBE1B Declared Inoperable When Surveillance Interval Expired Per Tech Spec 4.0.3 & Action Statement Entered.Monitor Will Still Register Seismic Events.No Such Events Have Occurred at Facility

ML20238C822
Person / Time
Site:	River Bend
Issue date:	09/02/1987
From:	Booker J GULF STATES UTILITIES CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
RBG-24546, NUDOCS 8709100397
Download: ML20238C822 (3)

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i' GULF STATES UTILITIES COMPANY HIVER BIND ST ATION POST OFFICt BOX 220 St FRANCISVILLE LOUIStAlyA 70776 ARCA CODE bod 636 6094 346 8061 September 2, 1987 RBG - 24546 File Nos. C9.5, G9.25.1.4 U.S. Nuclear Regulatory Commission Document' Control Desk Washington, D.C.-20555 Gentlemen:

River' Bend' Station - Unit 1 Docket No.'50-458 Enclosed is Gulf States Utilities Company's Special' Report concerning Seismic Monitoring at River Bend Station. This. report is being submitted pursuant to Technical Specifications 3.3.7.2.a and 6.9.2.

Sincerely,

.E. Jh/9

. E. Booker Manager, River Bend Oversight River Bend Nuclear Group JEB/TFP/I C/D h cc: U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 NRC. Resident Inspector P.O. Box 1051 St. Francisville, IA 70775 4/

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8709100397 870902 i PDR ADOCK 05000450-B. PDR

SPECIAL REPORT Per River Bend Station (RBS) Technical Specification 3.3.7.2, this Special Report is being submitted to provide the details concerning seismic monitor IERS-NBElB being inoperable for greater than 30 days.

Discussion The 18 month channel calibration required by RBS Technical Specification 4.3.7.2.1 for seismic monitor IERS-NBElB is pe-formed under Surveillance Test Procedure (STP)-557-4202. This instrument is located at elevation 232' 0",

azimuth 308' on the inside of the Shield Building wall in the Reactor Building annulus. During power operation, the entrances to the annulus are very difficult to open because the area is maintained at a negative pressure.

This negative pressure holds the doors closed. Therefore, the unit must be shutdown for the performance of the STP. For the plant to be shutdown solely to perform surveillance on the subject seismic monitor would cause an unnecessary thermal transient on the plant. In addition, the monthly channel check and semi-annual channel functional test, as well as one previous 18 month channel calibration, have previously been successfully performed.

The RBS Technical Specifications require performance of STP-557-4202 by 7/24/87 to maintain OPERABILITY of IERS-NBElB. However, the next refueling outage is scheduled to start on 9/15/87. RBS Technical Specification 3.3.7.2 Action (a) states that with one or more of the seismic monitoring instruments inoperable for more than 30 days, prepare and submit within the next 10 days a Special Report to the Commission outlining the cause of the malfunction and the plans for restoration. This is the only action that is applicable to strong motion time-history acceleration sensor IERS-NBElB being inoperable. On 7/24/87, the subject instrument was declared inoperable when the surveillance interval expired per Technical Specification 4.0.3 and the associated Action statement was entered. This has been determined to have no safety impact on the plant since these inst rument s provide no control functions and are not required for the safe shutdown of the unit.

Additionally, declaring IERS-NBElB inoperable does not affect any other instruments or records in the Seismic Moaitoring System as listed in RBS Technical Specificaiton Table 4.3.7.2-1.

Analysis The RBS Final Safety Analysis Report (FSAR) Section 3.7.4A describes the non-safety related seismic monitoring instrumentation system installed at RBS, pursuant to Regulatory Guide 1.12, " Instrumentation for Earthquakes", to monitor and record the motion and behavior of the plant in the event of an earthquake. This data is needed for post-event comparison with the data used for the Design Basis Earthquake (DBE) to determine the seismic response of )

plant systems important to safety following the seismic event. Regulatory {

Guide 1.12 does not specify the method used for this post-event analysis.

Even though sensor IERS-NBElB is administrative 1y declared inoperable, it will still continue to provide a signal to the data recorder should a seismic l event occur during this period. As of the date of this Special Report, no j

seismic event has occurred at RBS. However, if prior to 9/15/87 an event were to occur, the Calibration Report generated by the STP for IERS-NBElB would be used to correct the data for any inaccuracies found for the required analysis. Additionally, declaring IERS-NBElB inoperable does nat affect any other instruments or records in the Seismic Monitoring System as listed in RBS Technical Specification Table 4.3.7.2-1. Post-event analysis of the data ,

recorded by these other instruments may well render the data from IERS-NBElB unnecessary, depending upon the severity of the earthquake. Also, there is a technical basis for believing that seismic monitor IERS-NBElB would function as required well beyond the established surveillance frequency. The vendor supplied channel calibration surveillance procedure states, "This test should be performed every 18 months or at refueling." This frequency is based on the sensors not being subject to time related drift due to their simple mechanical design.

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