ML20247K412

Special Rept 89-002:on 890414,signal from Triaxial Time History Accelerograph Located Inside Drywell Determined to Contain Excessive Amount of Noise & Declared Inoperable for More than 30 Days.Cause of Event Not Determined

ML20247K412
Person / Time
Site:	Hatch
Issue date:	05/24/1989
From:	Hairston W GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
89-002, 89-2, HL-547, NUDOCS 8906010291
Download: ML20247K412 (5)

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p s < e.M HL-547-0150V X7GJ17-H540 May'24, 1989' U. S. Nuclear Regulatory Commission ATTN

Document Control-Desk Hashington, D. C.

20555 PLANT HATCH - UNIT 2 NRC DOCKET 50-366 OPERATING LICENSE NPF-5 SPECIAL REPORT 89-002 SEISMIC MONITORING' INSTRUMENT INOPERABLE FOR LONGER THAN 30 DAYS RESULTS IN SPECIAL REPORT AS REOU MED BY TECHNICAL SPECIFICATIONS Gentlemen:

~In accordance with the ' requirements of the Plant Hatch Unit 2

. Technical. Specifications Section 3.3.6.2,-

Georgia Power Company is-submitting the enclosed Special Report (SR). concerning. an : event where a seismic menitoring instrument was-inoperable longer than 30. days.

This event occurred at Plant Hatch - Unit 2.

Sincerely, N.). /L~/

2C H. G. Hairston, III DPR/ct

Enclosure:

SR 50-366/1989-002 c:

(See next page.)

t e9o6o2o291 89 524

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$DR ADOCK05h00366 PDC

U. S. Nuclear Regulatory Commission May 24, 1989 Page Two c: Georaia Power Comoany Mr. H. C. Nix, General Manager - Nuclear Plant Mr. L. T. Gucwa, Manager Engineering and Licensing GO-NORMS U. S. Nuclear Reaulatory Commission. Hashinaton.

D._ C1 Mr. L. P. Crocker, Licensing Project Manager - Hatch U. S. Nuclear Reaulatory Commission. Reaion II Mr. S. D. Ebneter, Regional Administrator Mr. J. E. Henning, Senior Resident Inspector - Hatch l

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0150V

6 ENCLOSURE.

j PLANT HATCH - UNIT 2.

NRC DOCKET 50-366 q

OPERATING LICENSE NPF-5

-1 SPECIAL REPORT 89-002 SEISMIC HONITORING 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" 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 (s) STATUS AT TIME OF EVENTS On 5/14/89, Unit 2 was in the run mode at an approximate power-level of ' 2326 MHt (approximately' 95 percent of-rated ' thermal power).

C.

DESCRIPTION OF EVENT

~ On 4/14/89, at approximately 1500 CDT, plant Instrument and Control personnel were performing plant procedure 57SV-L51-003-0S (Seismic Instrumentation Functional Test and Calibration).

The signal from the triaxial time-history accelerograph (2L51-N004), located inside the drywell on ~the feedwater inlet line to the reactor pressure vessel, was determined to contain an excessive amount of noise.

Therefore this seismic instrument was declared inoperable, and Limi ti ng " ~~~ '

Condition for Operation (LCO) 2-89-166 was initiated to track the status of the instrument.

Maintenance Work Order (MHO) 2-89-2034 was written to repair or replace 2L51-N004.

l 0150V HL-547 E-1

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ENC'LOSURE (Continued)-

SEISMIC MONITORING INSTRUMENT-IN0PERABLE FOR ~

LONGER THAN 30 DAYS RESULTS IN SPECIAL REPORT AS REOUIRED BY TECHNICAL SPECIFICATIONS The necessary maintenance cannot be performed until Unit 2 is -

shutdownL since the instrument is in the drywell which is not-accessible during' power operation.

Consequently on -5/14/89 2L51-N004 was still-inoperable and this special report is required.

D.

CAUSE OF EVENT The root _cause cannot be conclusively determined until access to the drywell can be obtained and a root cause investigation conducted into the seismic instrument's malfunction.

Based. on the evidence available, the root cause of this event appears to be component failure.

E.

ANALYSIS OF EVENT Four strong motion tricxial time-history accelerographs are-installed at appropriate locations to enable. prompt determination of the severity of any earthquake which may be experienced.

One of ~the 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 accelerographs 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 drywell on u the feedwater discharge line into the reactor' pressure vessel.

The signals of the four accelerographs 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 the Unit 2 seismic design basis.

In this event the accelerograph located on the feedwater discharge line was declared inoperable due to excessive noise in its output signal.

However, the other three accelerographs would provide sufficient data should a seismic event occur.

The accelerographs have no other design functions.

0150V HL-547 E-2

A es '

s ENCLOSURE (Continued)

SEISMIC MONITORING INSTRUMENT INOPERABLE FOR

["

-LONGER THAN 30 DAYS RESULTS IN SPECIAL REPORT

'AS REOUIRED BY TECHNICAL SPECIFICATIONS Based 'on 'the above information, it is concluded that this event had no adverse impact on nuclear safety.

The above analysis ~is applicable to'all power levels.

F.

CORRECTIVE ACTIONS-The corrective actions for this event include:

(-

1.

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

2.

Scheduling. HWO 2-89-2034 for completion during the next Unit 2 outage which will end in approximately December, 1989.

3.

Completing a root cause investigation into the seismic instrument malfunction prior.to the end of the next. Unit 2 outage.

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0150V HL-547 E-3

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