ML20037B518

Discusses Two Incidents That Occurred at Power Plant That Indicated Deficiency in Control Circuit Design.Requests That Licensee Perform Review of Control Circuits of safety- Related Equipment

ML20037B518
Person / Time
Site:	Dresden, Oyster Creek, Quad Cities
Issue date:	12/22/1972
From:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
To:	Brian Lee COMMONWEALTH EDISON CO.
Shared Package
ML20037B519	List: ML20037B518 ML20037B520 ML20037B521
References
NUDOCS 8010140635
Download: ML20037B518 (2)

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UNITED STATES ATOMIC ENERGY COMMISSION

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• WASHINGTON. D.C. 20545 y5 Decenber '22,1972 Docket Nos. 50-10,, 50-237, 50-249, 50-254 and 50-265 Commonwealth Edison Company ATTN:

Mr. Byron Lee, Jr.

Assistant to the President Post Office Box 767 Chicago, Illinois 60690 Gentlem3n:

'iko' incidents have occu. ed at a nuclear power plant that indicate a

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deficiency in the acntrol circuit design that warrants a review of the control circuits ;f all facilities to assure that these types of deficiencies do not exist or are cormeted if they do exist. Both incidents involved the inadvertent disabling of a conponent by mcking ouf the circuit b::naker for a different cc ponent.

In ene case, this caused the loss of capability to isolate secondary centairmant when this capability was required.

In the second case, the racking out of a bmaker for ene pu p disabled not cnly the pump being mmoved fron service but also its mdundant counterpart. Both of these occurrences resulted from the use of auxiliary contacts on the rcvable por:1cn of the circuit breakers in the control circuits of other cc penents. Wnen the breaker is racked out, the contml. circuit exploying these contacts is opened and may be rendered inopemble. A copy of the licensee's mports on these two occurrences a:e enclosed for your infc.mtion.

'T.e licensee's cor::ective m3asums for both of these cases included redesign of the control circuits so that racking out the breakem would not render the control circuits of other equipment inoperable.

As a result of these occurrunces, we request that you perfom a review cf the centrol circuits of all safety mlated equipm3nt at the plant to assure that disabling of one cc ponent does not, throu@ incorporation in other interlocking or sequencing centrols, render other components inoperable. All redes of test, opemtion, and failure must be considered.

It appears that in the cases cited above, the m0ked out positicn of breakers had not been included in the failure rode analysis of those c:ntml circuits.

Also, your procedures should be reviewed to ensure they provide that, whenever pam of a redundant system is rennved from service, the por-tien remaining in service is functionally tested i:=ediately after the disabling of the affected portion and, if possible, before. disabling of the affected portien.

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-2 Tne msults of your myiew a.m mouested within sixty days.

Eis infometien s'. uld be providad with a.e sig.ed original and thir:y-nine additional copies.

Sincemb,

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P *' Y E.aldJ Skovholt Assistant Dimetor for Operating Reac'ers Dimatorate of Licensing Ehclosums:

Licensee's mports en occurrences cc w/ enclosure:

Mr. Charles 'inittore President and Chairman Iowa-Illinois Gas and Electric Company 206 Eas t Second Avenue Davenport, Iowa 52801 Johr. W. Rowe, Esquire Isham, Lincoln 6 Beale Counselors at Law One First National Plaza Chicago, Illinois 60670 k