ML20085H151

AO BFAO-50-259/7446W:on 740910,average Power Range Monitor Channel D Flow Bias Scram Calibr Error Discovered.Caused by Personnel Error.Instrument Mechanics Instructed on Importance of Following Surveillance Instructions

ML20085H151
Person / Time
Site:	Browns Ferry
Issue date:	09/20/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Case E US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8308300261
Download: ML20085H151 (2)

Text

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r, Ir A Mr. Edson G. Case li:n sesma ( (

Acting Director of Licensing g . o' Office of Regulation . -

N U.S. Atonic Energy Co=nission Washington, DC 20545

Dear Mr. Case:

TDINESSEE VALLEY AUTHORITY - 3ROWHS FERRY NUCLEAR PIANT UNIT 1 -

DOCKET NO. 50-259 - FACILITY OPERATING LICEISE DPR AENORMAL ,

OCCURRE!0E REPORT BFAO-50-259/7446W The enclosed report is to provide details concerning Average Power Range Eonitor (APRM) channel "D" flow bias scram calibration error and is sub=itted in accordance with Appendix A to Regulatory Guide 1.16, Revision 1, October 1973. This event occurred on Browris Ferry Nuclear Plant unit 1 on September 10, 1974.

Very truly yours, TEIDESSEE VALLEY AUTHORITY 4$(sil

.cmas Jrpetor of Power Production Enclosure CC (Enclosure):

Mr. Iiornan C. Poseley, Director Region II Regulator /' Operations Office, USAEC 230 Peachtree Street, NW., Suite 818 Atlanta, Georgia 30303 e

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Report No.: 3FAO-50-259/7446W Report Date: September 20, 1974 '

Occurrence Date: September 10, 1974 Facility: Browns Ferry nuclear Plant unit 1 Identification of Occurrence .

Average Power Range Monitor (APRM) channel "D" flow bias seren calibration error.

I Conditions Prior to Occurrence The reactor was increasing power after recovering from a scram.

I Descriution of Occurrence ~

During review of the APRM flow bias calibration surveillance data, channel "D" flow bias scram trip was found to exceed the trip level setting in the region of cero recirculation flow by less than 1 percent. This situation '

occurred several times during the last two power ascensions, which covered a period of about 14 days.

Analysis of Occurrence .

The flow bias scran was not adjusted below the calculated limiting value as required by the technical specifications and' as specifically stated in the surveillance instructions. Because of the difficulty in adjusting the scran trip below the calculated limiting setroint and still allow adequate operating margin, the cero recirculation flow end of the scran trip was permitted to exceed the calculated limiting value slightly. This action was repeated on - - - ~

several occasions by different personnel. The difficulty in adjusting the circuitry is attributed to an i=:: roper calibration of the flow centrol trip reference unit, but it did not prevent cc=pliance to technical specification requirements. Failure to follow proper written instructions was the cause.

1 The reactor protection systen ability to function properly was not compromised because the other redundant APFJi channels' seren trips were adjusted below the calculated 14 4 ting values. There were no adverse effects on the health or' safety of the public as a result of this failure.

Corrective Action Twediately upon discovery, the channel "D" flow bias circuitry was properly adjusted. The other channels were tested and found within limits.

A meeting was held with all instrument mechanics.to ree=phasize the importance of following surve' lance instructions. It was pointed out that while perforring surveillance testing, the precedure must be in hand and perfor=ed exactly as written or changed in accordance with official procedures. -

Failure Data l Kone -

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