ML20084C125

AO 251-74-9:on 741227,newly Installed Digital Data Processing Sys Revealed Feedwater Temp Reading of Sys About 10 F Lower than Feedwater Temp Shown on Feedwater Temp Recorder.Caused by Incorrect Calibr Procedure

ML20084C125
Person / Time
Site:	Turkey Point
Issue date:	01/06/1975
From:	Schmidt A FLORIDA POWER & LIGHT CO.
To:	Case E US ATOMIC ENERGY COMMISSION (AEC)
References
AO-251-74-9, NUDOCS 8304070538
Download: ML20084C125 (3)

Text

P.O. Star $100 MIAMI, FLORfDA 33101

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/h rmoA ro.mi s tw ten .r January 6, 1975 Mr. Edson G. Case, Acting Director Office of Regulation Directorate of Licensing U. S. Atomic Energy Commission Washington, D. C. 20545

Dear Mr. Case:

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'f^O ABNORMAL OCCURRENCE NO. 251-74-9 JANUARY 6, 1975 ky( f /

OCCURRENCE DATE: DECEMBER 27, 1974 TURKEY POINT UNIT NO. 4

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FEEDWATER TEMPERATURE RECORDER C,% A' INCORRECT CALIBRATION PROCEDURE AN>,f[;' .,

qf; A. C_onditions Prior to Occurrence lY The reactor was in routine, steady-state power operation at an indicated power level of 99.9%.

B. Description of Occurrence comparison of the results of a routine secondary system calorimetric calculated by plant personnel with the results of a similar secondary system calorimetric performed by the newly installed Digital Data Processing System revealed that the feedwater temperature reading used by the Digital Data Processing System was about 10 F lower than the feed-water temperature shown on the feedwater temperature recorder.

Calculation of the secondary system calorimetric using a lower feedwater temperature results in a higher thermal power level. At an indicated thermal power of 100%, this 10 F error in feedwater temperature results in approximately 101.8%

thermal power.

When it was confirmed that the feedwater temperature measured by the Digital Data Processing System was correct, operator action was to reduce thermal power level to 100% thermal power as determined by the Digital Data Processing System calorimetri c .

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v Mr. Edson G. Case, Acting Director Page Two January 6, 1975 C. Cause of Occurrence The use of an incorrect calibration procedure for the feed-water temperature recorder system was the cause of this occurrence.

The feedwater temperature recorder uses a resistance tempera-ture detector (RTD) to measure feedwater temperature. An error of approximately 2.5 ohms was found when the overall resistance of the RTD circuit was measured. Analysis of the error concluded that the additional 2.5 ohms was equal to the resistance of one conductor between the recorder ampli-fier and the RTD. The effect of this resistance had not been considered in the RTD calibration proceclure. Therefore, when the feedwater temperature was calibrated using this procedure.

the recorder indicated a feedwater temperature that was approximately 10 F high.

D. Analysis of Occurrence The incidents analyzed and presented in the Turkey Point Unit Nos. 3 and 4 Final Safety Analysis Report assumed con-servative values for instrument calibration error, instru-ment drift, and calorimetric test error. A value of two percent was assumed for calorimetric test error.

Review, analysis, and evaluation of the operating conditions during the time that the incorrect feedwater temperature recorder calibration procedure caused an error of approxi-mately 10 F in recorded feedwater temperature, concludes the calorimetric test error was approximately 1.8%. This error is within the 2% value assumed in these safety analyses.

Therefore, neither reactor safety nor the health and safety of the public were jeopardized by this occurrence.

E. Corrective Action The procedure for calibrating the feedwater temperature recorder has been revised to inulude the resistance of the conductor between the temperature sensor and the recorder amplifier.

Calibration of the feedwater temperature re order using the revised calibration procedure will prevsat recurrence of this and similar incidents.

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Mr. Edson G. Case, Acting Director Page Three

January 6, 1975 The calibration of other RTD installations at Turkey Point Unit Nos. 3 and 4 were checked and it was determined that the correct calibration procedures were used.

F. Failure Data .

This is the first abnormal occurrence of this type experienced at Turkey Point Plant. However, the feedwater temperature recorder for Unit No. 3 was calibrated using the same pro-j cedure used for Unit No. 4 recorder. Therefore, a separate i

abnormal occurrence report will be issued to cover this inci-dent for Unit No. 3.

l Very truly yours, s.

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D. Schmidt Vice President

• Power Resources VTC/cpc cc: Jack R. Newman, Esquire l Mr. Norman C. Moseley 4