ML20085C862

AO 50-254/74-39:on 741216,rod Worth Minimizer Stall Alarm & Block Rod Inoperable Withdrawal Failed.Caused by Error in Spring 1974 Procedure Mod.Procedure & Startup Surveillance Changed

ML20085C862
Person / Time
Site:	Quad Cities
Issue date:	12/26/1974
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Oleary J Office of Nuclear Reactor Regulation
Shared Package
ML20085C865	List: ML20085C862 ML20085C867
References
AO-50-254-74-39, NJK-74-439, NUDOCS 8307130167
Download: ML20085C862 (3)

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Post O'fice Box 216 Cordova, Illinois 61242

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Hr. John F. O' Leary, Director Directorate of Licensing Regulation

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Reference:

Quad-Cities Nuclear Power Station, Unit I Docket No. 50-254, DPR-29, Appendix A Sections 1.0.A.2, 3.3.0.3.b, 6.6.B.I.a

Dear Mr. O ' Leary:

Enclosed please find Abnorraal Occurrence Report No. A0 50-254/74-39 for Quad-Cities Nuclear Power Station. This occurrence was previously reported to Region 111, Directorate of Regulatory Operations by telephone on December 16, 1974, and to you and Region t il, Directorate of Regulatory Operations by telecopy on December 16, 1974.

This report is submitted to you in accordance with the requirements of Technical Specification 6.6.B.I.a.

Very truly yours, COMM0!NEALTH EDISON COMPANY QUAD-CITIES NUCLEAR POWER STATION y [

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N. J. Kalivianakis Station Superintendent NJK/BBP/jeh cc: Region iII, . Directorate of Regulatory Operations J. S. Abel

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REPORT NUMBER: A0 50-254/74-39 l l

REPORT DATE: 12/23/74 OCCURRENCE DATE: 12/16/74 FAClllTY: Quad-Cities Nuclear Power Station Cordova, Illinois 61242 IDENTIFICATION OF OCCURRENCE:

Rod worth' minimizer inoperable below 10% power without operator substitution in violation of Technical Specification 3.3.B.3.b.

CONDITIONS PRIOR TO OCCURRENCE:

Unit 1 in the start-up mode with a power level of approximately 5%, and reactor water temperature of approximately 450 F.

DESCRIPTION OF OCCURRENCE:

On December 16, 1974, prior to start-up, the rod worth minimizer (RWM) was initialized and verified operable. The reactor was made critical at 5:40 a.m.

In rod group 4 At approximately 7: 15 a.m. while withdrawing rod L-5 the RWM stalled. Normally a RUM stall should alarm in the control room and block rod withdrawal, neither of which happened. The operator being unaware of the RWM failure continued withdrawing control rods, thus exceeding Technical Specifi-cation 3.3.B.3.b. At approximately 8:45 a.m. the reactor operator mistakenly selected and withdrew an out of sequence control rod. This was five rods af ter the computer stall. At 8:55 a.m. a technical staf f nuclear engineer noted the rod wi thdrawal error. Rod J-10 which should have been at position 00 was at position 48 and rod J-7 which should have been at position 48 was at position

00. The out of sequence rods were positioned at their in-sequence positions and the start-up was halted until the source of the RWM failure was determined.

DESlCNATION OF APPARENT CAUSE OF OCCURRENC,E,:

Procedure -

The cause of this occurrence is attributed to an error in the procedure for initializing the RVM. The Unit i RVM was modified during the spring 1974 refuel-ing. At that time the procedure for initializing the RWM was rewritten and a step requiring that computer room console mode switch to be turned to the off position as the last step of initialization was leftout. With the console in the local _ position, the control room receives no indication of a computer stall, and no rod blocks following the stall. This was the cause of. the RWM failure.

-ANALYSIS OF OCCURRENCE:

The' safety implications of this occurrence were minimized by the fact that neither of the Quad-Cities Units has ever had an uncoupled control rod. The rod drop accident which forms the bases for the RWM technical specification would require a

A0 50-254/74-39 Dscembsr 23, 1974

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'a high worth rod to be uncoupled, the rod to stick in when the drive is withdrawn, and then the rod to fall before the rod is found to be uncoupled by the over travel check and the drive inserted. This is a very unlikely set of events. Since there was no rod drop there was no abnormal core transient as a result of this occurrence.

CORRECTIVE ACTION The procedure for initializing the RWM has been changed to require the console switch to be left in the off position after initialization.

A caution has been added to the RWM operating procedure, that if the RWH falls to update as the rod selected changes the RWM is not functioning.

The RWM start-up surveillance has been changed to require that a check be made that the computer room console mode switch be in the off position.

FAILURE DATA No failure of this type has occurred before at Quad-Cities Station.

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