ML20247F771

Special Rept:On 980403 & 980503 Seismic Monitoring Sys Was Declared Inoperable.Caused by 5-volt Power Supply & Regulator Card Failure.Imd & Sys Engineering Are Continuing to Identify & Resolve Problems So Sys Can Be Operable

ML20247F771
Person / Time
Site:	Braidwood
Issue date:	05/08/1998
From:	Tulon T COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9805200044
Download: ML20247F771 (2)

Text

Commonw calth I dison Company

, ,e llr.tidwood Generating Station Route 01, llox 84 Hraces ille,11. 60107-96 l 9 Tcl H I 5-1542801 i '.

May 8,1998 United States Nuclear Regulatory Commission  !

Attention: Document Control Desk Washington, D.C. 20555-0001

Subject:

Braidwood Nuclear Power Station Units 1 and 2 Facility Operating Licenses NPF-72 and NPF-77 NRC Docket Nos. 50-456 and 50-457 Seismic Instrumentation Monitoring System Ten Day Report  ;

i l

The Braidwood Technical Specification 3.3.3.3, " Seismic Instrumentation," requires that l with one or more of the required seismic monitoring instrumentation inoperable for more than thirty (30) days, a Special Report shall be submitted to the Commission within the I next ten (10) days. This rcport is to outline the cause of the malfunction and the plans for restoring the instrument (s) to operable status.

It is the purpose of this letter to transmit such a report. The seismic monitoring system was declared inoperable on April 3,1998, and on May 3,1998 was inoperable for thirty days. Below is a summary of the seismic monitoring system status, a history of the repair progress made to-date, and the present plans for returning the system to operability.

Description of System and Failure The Seismic Monitor System consists of a Response-Spectrum Analyzer (RSA-50) and a Time-Ilistory Accelerograph which includes a Digital Cassette Accelerograph (DCA-300) and Strong Motion Reader (SMR 102). There are also six triaxial acceleration sensors located throughout the plant. All of this equipment remains inoperable.

On April 3 at 0618 the Seismic Monitoring system was declared inoperable due to erroneous output indications with multiple portions of the system. Troubleshooting determined that the 5-volt power supply and regulator card failed causing multiple card failures within the DCA-300, RSA 50, and the SMR 102. In the DCA 300 unit the power, trigger, clock, buffer and master logic circuit boards along with two other logic circuit boards have failed. In the RSA 50 unit, the CPU and the Input / Output printer board have failed. Repairs to the DCA 300 and the RSA 50 must be completed prior to troubleshooting of the SMR 102 unit.

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Document Control Desk M,ay 81998 Page 2

' Repair progress to date (E&rts & Results)

The 5-volt DC power supply is fed from a 12-volt DC supply. When the 5-volt supply failed, the system received 12 volts to all ofits circuit boards. There are approximately 20 complimentary m'etal oxide semiconductors (CMOS) and transistor transistor logic (TTL) circuits boards. As of 5/5/98 nine circuit boards have been identified as damaged.

The Instrument maintenance Department (IMD) is still identifying and repairing problems that have occurred from losing the 5-volt supply to the system.

.The problems are numerous and difficult to repair due to not having any spare circuits cards or replacement parts. Terra Technology, Inc. of Seattle Washington developed the exis'ing t seismic system configuration in the early 1970's. The vendor hasn't manufactured replacement parts for the vintage of hardware at Braidwood Station since the early 1980's. Replacement circuit boards are no longer manufactured, requiring troubleshooting ofthe failed circuit boards to the component level.

Once the components are identified, the equivalent parts will be procured.

Current Plans IMD and System Engineering are continuing to identify and resolve the problems so the seismic monitoring system can be returned to operability. The return to service date is currently estimated to be six months.

Concurrent with repair actions, Site Design-Engineering personnel are investigating altemative system replacements in its entirety. We expect that a suitable replacement will

- be identified by the end of1998.

Please address any comments or questions regarding this matter to Richard L.

Schliessmann, at (815) 458-2801 extension 2038.

Sincerely, Ti y . Tulon s Vic'ePresident raidwood Nuclear Generating Station ec: ' A. B. Beach, Regional Administrator - Rill S. N. Bailey, Braidwood Project Manager - NRR C. Phillips, Senior Resident Inspector '- Braidwood OfYice of Nuclear Facility Safety -IDNS ..

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