ML20085K191

Ao:On 731109,during Routine Monthly surveillance,2/3 Core Height Water Level Sensors LITS-263-73A & B Found to Have Setpoints Above Tech Spec.Caused by Setpoint Drift.Switches Reset

ML20085K191
Person / Time
Site:	Dresden
Issue date:	11/19/1973
From:	Worden W COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085K183	List: ML20085K181 ML20085K186 ML20085K188 ML20085K191
References
862-73, NUDOCS 8310200275
Download: ML20085K191 (2)

Text

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a Com worith Edison One Fir bonal Plaza, Chicago. Ilknois Address 7eply to: Post Office Box 767 Chicago. Clinois 60690 WFW Ltr.f862-73 Dresden Nuclear Power Station d

R. R. #1 Morris, Illinois 60450 November 19, 1973 A

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Washington, D. C.

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SUBJECT:

LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3, s

REPORT OF ABNORPAL OCCURRENCE PER SECTION 6.6.B.1 0F THE w

I TECHNICAL SPECIFICATIONS.

2/3 CORE HEIGHT LEVEL SENSORS OUT OF CALIBRATION.

References:

1) Letter from W. P. Worden to A. Giambusso dated January 19, 1973 concerning same subject.

2) Notification of Region III of AEC Regulatory Operations Telephone: H. Dance 1550 hours0.0179 days <br />0.431 hours <br />0.00256 weeks <br />5.89775e-4 months <br /> on November 9, 1973 Telegram:

J. Keppler 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on November 9,1973

3) Dwgs: P & ID M-26(SF)

Dear Mr. O' Leary:

This letter is to report a condition relating to the operation of the unit at about 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on November 9, 1973. At this tisce, the 2/3 core height water level sensors LITS-263-73A and B were found to have i

setpoints above the Technical Specification of 1257" decreasing.

1 This malfunction is contrary to Table 3.2.2 of the Technical Specifications which requires that the containment spray system be inter-locked to prevent operation if reactor level is at or below 2/3 of the core height.

PROBLEM During routine monthly surveillance of the 2/3 core height containment spray interlock level switches, LITS-263-73A and B, the setpoints were found to be 261" H2O dP and 262" H O dP respectively.

2 The Technical Specifications require that these switches operate at i

f257" H O dP.

The switches were inunediately set to 254.5" H O dP and 2

2 255.0" H O dP.

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edry November 19, 1973 INVESTICATION The switches in question are Yarway number 4418EC devices. Past surveillance history indicates that they are normally very reliable devices which seldom drift.

Switch LITS-263-73B was last calibrated on October 28, 1973 as a post maintenance check af ter a valve manifold was replaced. The switch setpoint was found to have drifted 9" after only 12 days. Therefore, it is concluded that an increased surveillance schedule will not guarantee consistant cocpliance with the Technical Specification setpoint.

Previous to this Technical Specification violation. LITS 3-263-73A has failed four times since September,1971 with the last failure occurring in January, 1973. Each month since January, the switch was found to be within Technical Specification limits.

Switch LITS-3-263-73B has failed three times since September, 1971 with the last failure occurring on August 3, 1972 when both switch A and B failed.

CORRECTIVE ACTION The switches were immediately reset to comply with Technical Specification requirements. The problem now will be to determine the cause of this sporadic change in setpoint. The following steps will be taken to resolve the problem.

1.

Consult the manufacturer for assistance in solving the problem.

2.

Analyze the procedure used by the Instrument Mechanics uho set the switches to determine if errors in technique are causing the problem.

EVALUATION Normal setpoint of these switches is 96/144ths core height.

The out of specification trip points would have been 91/144ths and 92/144ths.

For all practical purposes this is still 2/3 core height and therefore it is concluded that the safety of the plant personnel or the general public was not jeopardized as a result of this setpoint drif t.

Sincerely,

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W. P. Worden Superintendent WPW:do

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Mr. Dennis L.

Ziemann, Chief Operating Reactors - Branch 2 l

Division of Rcactor Licensing U.S. Nuclear Regulatory Commission Washington, D.C.

20555

Subject:

Dresden Station Units 1, 2, and 3 Hydraulic Snubber -

Technical Specifications-.g' 3

NRC Dkts. 50-10, 50-237, and 50-249/

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Dear Mr. Ziemann:

In response to your letter dated July 9, 1975 concerning this subject, we are preparing Technical Specifications for Dresden Units 1, 2, and 3.

These specifications are currently undergoing review and we expect submittal by September 19, 1975.

.If further delays occur, you will be notified promptly.

Very truly yours, G. A. Abrcll Nuclear Licensing Administrator Boiling Water Reactors y

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