ML20081M847

Interim Deficiency Rept,Item E-50 Re Annunciator Sys Replacement Light Bulbs.Initially Reported on 830823.Two Contact Blades in Drake 4390 Socket Produce Metal Shavings Causing Short Circuit.Circuits Will Be Redesigned

ML20081M847
Person / Time
Site:	Zimmer
Issue date:	11/09/1983
From:	Williams J CINCINNATI GAS & ELECTRIC CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
10CFR-050.55E, 10CFR-50.55E, E-50, LOZ-83-0199, LOZ-83-199, NUDOCS 8311170399
Download: ML20081M847 (3)

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Nam M THE CINCINNATI GAS & ELECTRIC COMPANY CINCINNAT1, OHIO 45201 November 9, 1983 s.w wawasa LOZ-83-0199 SENeon vect PRE $totNT NWCLEAR OPERA?>OseS Docket No. 50-358 U.S. Nuclear Regulatory Commission Region III 799 Roosevelt Road

' Glen Ellyn,. Illinois 60137 Attention: Mr. J.G. Keppler Regional Administrator Gentlemen RE: WM. H. . ZIMMER NUCLEAR POWER STATION - UNIT 1 10CFR50. 5 5 (e ) , ITEM E-50, ANNUNCIATOR SYSTEM REPIACEMENT LIGHT BULBS W.O. 57300, JOB'E-5590,' FILE ~NO. 956C, E-50 This letter constitutes an interim repott concerning the subject condition initially reported to the Commission on August 23, 1983 as a potentially reportable deficiency. CG&E has determined that this condition is reportable under 10CFR50.55(e).

Our last report, LOZ-83-0159, dated September 21, 1983, stated that the electrical short and resulting fire which occurred during~the bulb replacement was caused by the unclipped light bulb filament lead wires (whiskers) protruding from the solder connection at the base of the annunciator bulbs. Although

_it was found that removal of these whiskers lowered the number of short circuits, it did not completely eliminate the problem.

Further investigation leads CGEE to conclude that the two contact blades in the Drake 4390 socket are sharp and produce metal shavings from the sof t solder - terminals during the twisting motion used to insert the bulbs. These shavings apparently cause the short circuit in the socket. Since the lamps operate at 132 VDC, once the arc is initiated it is sustained and may eventually

. lead to a fire. In addition, the dimmer rheostat which limits the current flow in the lamp circuit could be contributing to this condition. Instead of being self clearing or tripping the circuit breaker protecting the lamp box during a short circuit condition, the rhaostat allows the electric current to be sustained thus creating a condition that can eventually ignite the socket.

Although the annuciator system is not a nuclear safety-related system, the annunciator lamp boxes are installed in both 8311170399 831109 PDR ADOCK 05000358 S PDR p. '7

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9 Mr. J.G. Keppler Regional Administrator-November 9,.1983 LOZ-83-0199 Page 2 safety and nonsafety related panels in the Main Control Room. A fire in an annunciator lamp box could adversely affect the safe operation of the plant if the fire grew to a size that could

. jeopardize nearby safety-related cables, panel wiring, or panel equipment, or could affect.the performance of the control room operators. The lamp socket problem is a significant deficiency in the final design of the annunciator lamp boxes and based on the above analysis is reportable under 10CFR50.55 (e) .

The corrective actions stated in our last report; using alternate bulbs and checking for the loose lead wire prior to issuance for installation will be continued. CG&E is also considering the following additional corrective actions to eliminate the annunciator fire condition:

1. Re-design of the annunciator lamp circuits.

2.- Replacement or redesign of the lamp boxes.

A follow-up report will be submitted by January 16, 1984.

We trust the above will be found acceptable as an interim report under 10CFR50.55 (e) .

Very truly yours, THE CINCINNATI GAS & ELECTRIC COMPANY By

. WILLIAMS, JR.

SENIOR VICE PRESIDENT DJS/sfr

Mr. J.G. Keppler

- Regional Administrator November 9, 1983 LOZ-83-0199 Page 3 cc NRC Office of Inspection & Enforcement Washington, D.C. 20555 NRC Recident Site Supervisor

_ ATTN W.M. Hill NRC Zimmer Project Inspector, Region III ATTN: E. R. Schweibinz L

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