ML20084M414

AO 3-72-6:on 720829,drifts Noted in Barton Model 386 Differential Pressure Transmitters.Cause Not Found. Transmitters Recalibr & New Transducers Installed

ML20084M414
Person / Time
Site:	Turkey Point
Issue date:	10/05/1972
From:	Schmidt A FLORIDA POWER & LIGHT CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084M404	List: ML20084M414
References
AO-3-72-6, NUDOCS 8306020151
Download: ML20084M414 (2)

Text

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Mr. John F. O' Leary, Director /$' ' N,-r T. -

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U.S. Atomic Energy Commission ?M e n -a -

Washington, D. C. 20545 Nm Ma Y a?

'. m!: P .m M RE: TURKEY POINT PLANT UNIT NO. 3 hih h DOCKET NOS. 50-250 & 50-251 ABNORMAL OCCURRENCE NO. 3-72-6 Vh

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ERR 0NEOUS PRESSURIZER LEVEL INDICATION

Dear Mr. O' Leary:

In accordance with Technical Specification 6.6.2 a(1) and in amplifi-cation of the Company's telegram to Director, Region II, Directorate of Regulatory Operations of September 29, 1972, this report is submitted.

On August 29, 1972, while at hot shutdown, it was noted that the pressurizer level cold cali' ition ci annel indication differed from the level indicated by the three arrow range hot calibration channels. The disagreement was found to be. caused by zero drifts from -9G av to -111 my on a 1-5 volt scale in the three narrow range level transmitters (LT-3-459, LT-3-460, and LT-3-461). The transmitters are Barton Model 386 Differential Pressure Transmitters. The cause of the drifts was thoroughly investigated but no reason for the problem could be found. The three transmitters were immediately vented, back-flushed and recalibrated.

On September 20, 1972, while at cold shutdown, during routine calibration, it was found the three transmitters had again experienced zero drifts of

-80 mv, -200 mv, and -400 mv for LT-3-459, LT-3-460, and LT-3-461, respectively.

Again, no cause could be found for the drifts. Technical representatives from Westinghouse and Barton arrived on site on October 2, 1972 to determine and correct the problem. The representatives felt that the drifting was caused

g. by the transmitter transducers. New transducers manufactured by a new process were installed and the transmitters will be tested and monitored closely to verify proper operation.

The erroneous levbl. indication was an abnormal occurrence, in the sense

]- of Section 1.13.1,. Technical Specifications, because the indicated pressurizer level was lower than the actual level and hence, the high pressurizer level

. reactor trip would not have operated at the proper 92% pressurizer level, but,

. instead, at about 95% for the August 29 incident and at about 97% for the M September 20 incident. Thus, the safety system setting was less conservative than the level in Section 2.3 of the Technical Specifications. However, reactor safety was not affected because the high pressurizer level reactor trip is automatically disabled below 10% power and, since Unit 3 has not yet gone critical, the trip was not in effect during the per d of erroneous level 8306020151 721027 f #

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o o indication. Had the erroneous reading occurred during operation above 10%

power, the automatic pressurizee level control would have maintained level about 3% above programmed level and in a casualty situation, the reactor would have tripped at about 95% or 97% pressurizer level.

This letter is submitted beyond the ten day reporting deadline because it was not realized until September 27, 1972, that the erroneous indication constituted an abnormal eccurrence.

Sincerely, A.

W

. Schmidt Director of Power Resources ADS:DWJ:dg cc: Mr. John Davis, Director Region II, Directorate of Regulatory Operations U. S. Atomic Energy Commission Suite-218, 230 Peachtree Street, N. W.

Atlanta, Georgia Dr. James Coughlin J. R. Bensen W. H. Rogers, Jr.

Documentary Files C. E. Liebler C. E. Branning/ Plant' File D. W. Jones J. W. Williams, Jr.

Plant Nuclear Safety Committee l

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