ML20012E468

Special Rept 2-90-002:on 900321,seismic Monitoring Instrument Inoperable for Longer than 30 Days.Cause Not Determined.Seismic Instrument Declared Inoperable & Tracking of Limiting Condition for Operation Established

ML20012E468
Person / Time
Site:	Hatch
Issue date:	03/26/1990
From:	Hairston W GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
2-90-002, 2-90-2, HL-1009, NUDOCS 9004050215
Download: ML20012E468 (4)

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u. , March 26. 1990 1 U.S. Nuclear Regulatory Commission 'l m '

ATTN: Document Control Desk j

, . Washington, D.C. 20555 )

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' PLANT tiATCH - UNIT 2 NRC DOCKET 50-366 1 i OPERATING LICENSE NPF-5 l SPECIAL REPORT 90-002 SEISMIC MONITORING INSTRUMENT INOPERABLE .

L' FOR LONGER THAN 30 DAYS RESULTS IN SPECIAL REPORT AS REOUIRED BY TECHNICAL SPf1IFICATIONS

Gentlemen

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1 In accordance with- . the requirements of the Unit 2 Technical :l lM.

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Specificatlons Section 3.3.6.2, Georgia Power Company is submitting the 1 enclosed Special Report concerning an event'where a Seismic Monitoring '

Instrument s was inoperable for longer than 30 days. This event occurred at L

y Plant Hatch - Unit 2. -

6 If you have any questions in this regard, please contact this office at '

. any time. -

,. 1 Sincerely, 1

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I' W. G. Hairston, II; i

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Enclosure:

Special Report i

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f March 26, 1990 p' Page Two i

c: Georaia Power Company Mr. H. C. Nix, General' Manager - Nuclear Plant Mr. J. D. Heidt, Manager Engineering and Licensing - Hatch ,

GO-NORMS U.S. Nuclear Reaylatory Commission. Washinoton. D.C.

Mr. L. P. Crocker, Licensing Project Manager - Hatch U.S. Nuclear Reaulatory Commission. Reaion 11 Mr. S. D. Ebneter, Regional Administrator Mr. J. E. Menning, Senior Resident Inspector - Hatch Y

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j ENCLOSURE I i

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PLANT HATCH - UNIT 2 NRC DOCKET 50-366 OPERATING LICENSES NPF-5  !

SPECIAL REPORT 2-90-002 SEISMIC MONITORING INSTRUMENT INOPERABLE FOR LONGER THAN 30 DAYS RESULTS IN SPECIAL REPORT AS REOUIRED BY TECHNICAL SPECIFICATIONS A. REQUIREMENT FOR REPORT This report is required per Unit 2 Technical Specifications section 3.3.6.2. This section of the Technical Specifications states ,

that the seismic monitoring instrumentation shall be operable at all times. Action statement "a" of this section states that with one or ,

more of the required seismic monitoring instruments inoperable for

• more than 30 days, a Special Report is required to be submitted within the next 10 days outlining the cause of the malfunction and the plans for restoring the instrument to operable status.

B. UNIT STATUS AT TIME OF EVENT On 3/21/90, at approximately 0606 CST, Unit 2 was in the Run mode at an approximate power level of 2436 CMHT (approximately 100 percent of .

rated thermal power). "

C. DESCRIPTION OF EVENT ,

1 l On 2/19/90, at approximately 0930 CST, plant Instrument and Control l

personnel were performing plant procedure 57SV-L51-003-0S, " Seismic >

Instrumentation Functional Test and Calibration." The signal from triaxial time-history accelerometer 2L51-N004, located inside the drywell, on a carbon steel plate rigidly attached to the feedwater inlet line to the reactor pressure vessel, was determined to contain an excessive amount of noise. Therefore, the seismic instrument was declared inoperable and Limiting Condition for Operation (LCO) 2-90-084 was initiated to track its status. Also, Deficiency Card (DC) 2-90-0548 was written to document the condition.

Since the instrument is located in the drywell, an area inaccessible during power operation, and since the unit was operating at power, repair could not be effected before the 30 day time limit expired.

Consequently, on 3/21/90, 2L51-N004 was still inoperable, and this Special Report is required.

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D. CAUSE OF EVENT  :

j The root cause cannot be determine conclusively until access to the 1 drywell can be attained and an investigation conducted.

E. ANALYSIS OF EVENT Four strong-motion triaxial time-history accelerometers are installed at appropriate locations to enable prompt determination of the '

severity of any earthquake which may be experienced. One of the Li instruments is installed in the switchyard to measure the free-field-ground acceleration and another is installed in the Diesel Generator Building. The other two accelerometers are located in the Reactor Building: one on the east side of the Reactor Building drywell pedestal at elevation 87 feet, and the other inside the s drywell on a carbon steel plate rigidly attached to the feedwater inlet line into the Reactor Pressure Vessel.

The signals of the four accelerometers are recorded on magnetic tape in the main control room. Following a seismic event, this data would be processed to enable the comparison of the measured seismic response with tne Unit 2 seismic design basis.

In this event, the accelerometer located on the feedwater discharge line was declared inoperable. However, the other three accelerometers are operable and would provide sufficient data should  :

a seismic event occur. The accelerometers have no other design functions.

Based on the above information, it is concluded that the event has no adverse impact on nuclear safety. The above analysis is applicable to all operating conditions.

F. CORRECTIVE ACTIONS Corrective actions for this event include:

1. Declaring seismic instrument 2L51-N004 inoperable and establishing a tracking LCO.

2. Initiating an engineering evaluation of the feasibility of relocating 2L51-N004 and/or replacing the instrument to improve reliability.

3. Returning 2L51-N004 to operable status during the next Unit 2 outage of sufficient duration.

10271

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