ML20084P900

Ao:On 740321,suppression Chamber Water Level Exceeded Tech Specs.Caused by Malfunction of Level Transmitter LT-1-1626. Calibr Procedure Will Include Backflushing of Sensing Lines During Each Calibr

ML20084P900
Person / Time
Site:	Quad Cities
Issue date:	03/29/1974
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084P904	List: ML20084P900 ML20084P917 ML20084P935
References
NJK-74-18, NUDOCS 8306130067
Download: ML20084P900 (2)

Text

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/g Quad-CL/ Generating Station Post Office Bex 216 (d) p (D

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Farch 29, 1974 NJK-74-18 h /

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. xa se:na N J. F. O' Leary, Director s g Directorate of Licensing ... ,

U. S. ATOMIC E'.7EGY CC'24ISSION Washington, D. C. 20545

REFERENCE:

Quad-Cities Nuclear Power Station, Unit I Docket #50-254, License DPR-29, Appendix A, Section 1. 0. A .2. , 1.0. A .4. , 3 7. A .l.b. ) 6. 6.B.1.a.

Dear Mr. O' Leary:

The purpose of this letter is to infom you of the circumstances that caused the Unit 1 suppression chamber water level to exceed Technical Specification 3.7.A.l.b. The cause of the occurrence was due to a malfunction of level transmitter LT-1-1626. This was reported to you as an abnor=al occurrence by telegram en March 21, 1974 and was dis-cussed with Re;; ion III, Directorate of Regulatory Operations also on March 21, 1974 by telephone.

PROBLD: A%D I .'.TSTIGATIO::

On March 21,197L, with Unit 1 operating at 740 MWe, the quarterly calibration check on suppressien chamber level transmitter LT-1-1626 was performed. The as-found check revealed that the transmitter was  ;

out of calibration. Followin:; recalibration, the suppression chamber level indicatien showed the level to be tco high. The sensing lines to the trans=itter were backflushed and the transmitter was again re-calibrated. Subsequently, the suppression chamber level indicated

-4", thus exceeding Technical Specification 3.7.A.l.b.

Filling of the suppression chamber was cermenced at 3:00 p.m. At 8:00 p.m. , the suppression chamber water level "HIGH/LON LEVEL" alarm c1 cared.

At 8:15 p.m. , the " SUPPRESSION CHAEBER HIGH LEVEL" alam was received.

Simultaneously the High Pressure Coolant Injection (HPCI) systm suc-tion valves autcmatically switched from the condensate storage tank to the suppression chamber. Both HPCI suction valves were open since this was the path being utilized to add water to the suppression chamber by gravity flow. 'dhen the valve change-over occurred, water flow to the suppression chamber was thus terminatcd. These actions occurred at +5" suppression chamber level. Draining of the torus back to its nor:al level was ccmmenced immediately.

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J.F. O' Leary, Director March 29, 1974 -

Calibration of level transmitter LT l-1626 was thoroughly checked again.

After backflushing the sensing lines to the transmitter several times and running eight separate checks, the transmitter was returned to ser-

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vice at 6:15 a.m. on March 22, 1974. A clear plastic tube attached to the sensing lines from the suppression chamber was used to verify the actual level. When the transmitter was returned to service the sup-pression chamber level was +21/4 inches. The level was finally re-turned to normal at 8:15 a.m. on that same day.

SAFETY EVALUATION The maximum suppression chamber level reached +5 inches during this abnorcal occurrence. This corresponds to approximately 2600 ft3 which is less than 33 greater than the 115,655 ft) limit in Technical Speci-fication 3 7.A.l.b.

Since the limiting condition for operation was exceeded by less than 3 per cent, the intent of the design basis was not violated, and the capability of the suppression chamber to perform its design function was not significantly reduced.

EVALUATION AND COFSELTIVE ACTION The suppression chamber level transmitter pressure lines tap directly into the suppression chamber. Water pressure is transmitted through a Bellows systc= to oil pressure which operates the level transmitter.

This calfuncticn of LT-1-1626 is attributed to accumulation of dirt and debris around the Sellows which impeded operation of the instrument.

Several corrective actions are being implemented to corruct the cause of this occurrence. The suppression chamber level transeitter cali-bration procedure will include backflushing the sensing lines during each calibration. Surveillance for this instrument is being increased to once a month for a six month pericd. Also, it is planncd to in-stall a sight glass indicating actual suppression chamber level to aid in calibration of the level transmitter.

CUMUIATIVE EXPERIE::CE There have been no previous failures of the suppression chamber level transmitter at Quad-Cities Station. The probability of a re-occurrence of this failure will be reduced by implementation of the corrections specified above.

Ve ruly yours, 8

Ju7 .

N. Kalivianskis, .

Superintendent

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) NJK-74-18 i cc: Regional Directord f

Directorate of Regulatory Operations - Region III (c_ '

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