ML20084U717

AO 50-265/75-2:on 750103,excessive Force Necessary to Open Vacuum Breakers Exceeded Tech Spec Limit.Caused by Corrosion of Valve Bearing Surfaces Compounded by Counterweight Arm Design.Arm Design Modified

ML20084U717
Person / Time
Site:	Quad Cities
Issue date:	02/07/1975
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Oleary J Office of Nuclear Reactor Regulation
Shared Package
ML20084U721	List: ML20084U717 ML20084U736
References
AO-50-265-75-2, NJK-75-61, NUDOCS 8306290199
Download: ML20084U717 (3)

Text

l wealth Edison Comg.sGen:

Quad. rating Station .

P:st Othca Box 216 '

Cordova,lilinois 61242 I -

Telephone 309/654-2241 ef M NJK-75-61 $ PIN /*

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Mr. John F. O' Leary, Director Directorate of Licensing Regulation U. S. ATOMIC ENERGY COMMISSION hg'[3 Washington, D. C. 20545 PrFERENCE: Quad-Cities Nuclear Power Station Docket No. 50-265, DPR-30 Appendix A, Sections 1.0.A.4, 4.7,.A.3.b., 6.6.8.1.a.

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Dear Mr. O' Leary:

Enclosed please find Abnormal Occurrence Report No. A0 50-265/75-2 for quad-

, Cities Nuclear Power Station. This occurrence was previously reported to Region li t , Directorate of Regulatory Operations by telephone on Jant.ary 3, 1975 and to you and Region lil, Directorate of Regulatory Operations by telecoDy on January 1. 1974 This report is submitted to you in accordance with the requirements of Techni-cal Specification 6.6.B.l.a. Due to an administrative error, this report was not submitted within the specified time period. We apologize for the oversight.

Very truly yours, COMMONWEALTH EDISON COMPANY QUAD-CITIES NUCLEAR POWER ST TION

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,-j d $lh N. J. Kallvianakis Station Superintendent NJK:KLH/dkp cc: Region ill, Directorate of Regulatory Opere Ions J. S. Abel

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0306290199 750207 PDR ADDCK 05000265 S PDR -

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=A* p (3 d b REPORT NUMBER: A0 50-265/75-2 REPORT DATE: February 6, 1975 OCCURRENCE DATE: January 3, 1975 FACILITY: Quad-Cities Nuclear Power Station Cordova, IL 61242 IDENTIFICATION OF OCCURRENCE:

Failure of Unit 2 reactor building to torus vacuum breakers.

CONDITIONS PRIOR TO OCCURRENCE:

Unit 2 was in cold shutdown for the current refueling outage.

DESCRIPTION OF OCCURRENCE:

During Unit 2 refueling outage, surveillance testing was performed on the reactor building to suppression chamber vacuum breakers pursuant to the requirements of Technical Specifications 4.7.A.3.b. The test results revealed that 90 foot pounds torque was necessary to open the vacuum breakers therefore exceeding the Technical Specification limit.

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

The apparent cause of excessive force required to open the vacuum breaker is attributed to corrosion of valve bearing surfaces compounded by the two counter-wieght arm design.

ANALYSIS OF OCCURRENCE:

The safety implications of this occurrence are minimal. The 20 inch diameter vacuum breakers are designed to maintain a maximum differential pressure of 0.5 psig between the reactor building 'and suppression chamber. The resultant force translates to 163 foot pounds of equivalent torque acting en the valve shaft.

The 50 foot pound limitation was chosen as acceptable criteria to provide a margin for deterioration of performance over time and yet ensure that the valves do not develop sufficient friction to prevent proper operation. The test results indicate that the valves would have perfor,med their intended function if neces-sary with a 44% margin of safety.

CORRECTIVE ACTION: ,

A two fold corrective action program has been completed to correct and prevent repetition of this occurrence. Modification M-4-2-74-61 was completed January ,

28, 1975 which removed one of two counterweight arms and adjusted the remaining arm such that operating forces are within Technical Specification limits. Ad-ditionally, the $64celllance testing for reactor building to suppression chamber vacuum breakers has been increased to include quarterly measurement of valve tor-que.

FAILURE DATA:

This is the first failure of Unit 2 20 inch reactor building to suppression

-hamber vacuum breakers manufactured by Atwood and Morrill. Similar failures have occurred for Atwood and Morrill 16 inch suppression chamber to drywell vacuum breakers. However, the completed modifications and increased surveil-lance will preclude a recurrence of this abnormal occurrence and minimize safety implications with regards to cumulative experience.

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