ML20084C924

Suppl to Ao:On 740301,unit Diesel Tripped Due to Differential Fault.Caused by Design Failure,Allowing Improper Alignment of Fuse Clips.Fuse Clip Holder Door Modified by Adding Threetwist Locks

ML20084C924
Person / Time
Site:	Dresden
Issue date:	06/04/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
397-74, 5218, NUDOCS 8304080357
Download: ML20084C924 (1)

Text

{{#Wiki_filter:' q CImmh:lth Edison One First t....cnal Plata. Chicago. Ilhnois b 1 Address Reply to: Post Office Box 767 Chicago, Illinois 60690  ; Dresden I!uclear Power Station R. R. #1 Morris, Illinois 60450

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bp ' C. ) YE- g u Mr. J. F. O'Loary, Director 6 JUN111974 x $ Directorate of Licensing u. m: w:r ,Q 4W1 / U. S. Atemic Energy Comission SN: 50 237 $, / Washington, D.C. 20545 ,q

SUBJECT:

LICE'!SE DPR-19 DRESDEI! I'UCLEAR PC'e'ER STATICU Ut'IT 2. SUPPLWEI;TARY II?C7.!'ATICi! TO REPCRT 07 AR'ICR:'AL CCCURREIICE PER SECTIC" 6.6.B.2 CP TH;' TECH!!ICAL SPECIFICATIC::S. _UTTIT 2 DIESEL GE::E3ATOR TRIP

Reference:

Report of Abnormal Occurrence to 15. J. F. O' Leary of the Atomic Energy Comission dated March 8,1974.

Dear Mr. O' Leary:

This letter is to furnish supplementary informatien to our report of March 8,1974, concerning Unit 2 Diesel Generator Trip. In that report we :tated that the fuse clic holders wouhi ha mMiNM neh that they would be permanently installed in the circuit. On further inspection it was discovered that the failure as reported was due to a desien failure. The original design of the fuse clip door was such that when closed it allowed improper alignment of the fuse clips. The improper aliennent was due to the fact that when the door was closed it was secured in only one corner. Being secured in only one corner allowed the door to bow slightly causing misaligned fuse clips. To correct the bow a modification to the fuse clip holder door was performed. The modification did not permanently install the fuses in the circuit as reported. Instead it added three tuist locks to the door such that when closed it would be secured evenly. As of this date the twist lecks have been installed on the unit 2, 3 and 2/3 diesel generators. Sincerely, f/ / bA&5%?+ II.'B. S,tephenson Superintendent BBS:TEL:ju b L l cc: TEL v' U,g 62.13 AEC Corr. Cat. I 1jf 4)

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8304000357 740604 PDR ADOCK 05000237 009'Y SENT REGION _ _ / - S PDR

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                                          ,ional Plaza Chicago, Illmois             O Adaress Reply to: Post Othee Box 767 Chicago, Illinois 60690 WPW Ltr.#175-74                                           Dresden Nuclear Power Station R. R. #1 Morris, Illinois         'v W March 8, 1974 p        Mh ,';   g b-4
                                                                                                                        .s Mr. J. F. O' Leary, Director Directorate of Licensing
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U. S. Atomic Energy Commission L .a m Washington, D. C. 20545  % m sas -

SUBJECT:

• LICENSE DPR-19, DRESDEN NUCLEAR POWER STATION ' REPORT OF ABNORMAL OCCURRENCE PER SECTION 6.6.B.2 0F THE TECHNICAL SPECIFICATIONS.

UNIT 2 DIESEL GENERATOR TRIP.

References:

1) Notification of Region III of AEC Regulatory Operations.

Telephone: Mr. F. Maura, 1420 hours on March 4, 1974.

2) Dresden Station Electrical Prints 12E2334, 12E2336, and 12E2346

Dear,

Mr. g' Leary- , ,, , This letter is to report a condition relating to the operation of the unit at 1905 hours on March 1, 1974. At this time, the unit diesel tripped due to a differential fault. This malfunction is contrary to the basis for section 3.9 of the Technical Specifications which requires that an adequate supply of electrical power be available during operation. EROBLEM Following the replacement of the Unit 2 diesel generator fuel oil hose, the diesel was started and ran for an operational test. During this test, the diesel generator tripped af ter about 40 minutes of operation. At the time of the occurrence, the unit was just critical, thermal power was about 3 megawatts with the mode switch in the startup positien. INVESTIGATION An investigation into the problem revealed that a differential I trip occurred due to an intermittent open on the "B" phase of the diesel generator output. The open on "B" phase was due to a failure of the bus fuse clips which were found burnt off. B

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1 Mr. J. F. O'Leiry O O March 8, 1974 l l

          '                          On further investigation, it was discovered that the clips had been replaced during the last unit outage because the original clips
                      ' appeared burnt. The replacement clips appeared to be manufactured in a different manner than the original clips since they were slightly longer

and did not have the elasticity that the original clips had. . .

_ CORRECTIVE ACTION Since both the original and the replacement clips appeared to experience the identical problem, it was decided to modify the fuse compartment. The modification will permanently install the fuse holders in the circuit and eliminate the fuse clips. At this time a work request has been kritten which requests a modification to all three station diesels. ? EVALUATION During the occurrence of this failure, the safety of the plant and public was not in jeopardy. The loss of the unit diesel occurred when thermal power was only about three megawatts. Also at the time of

the failure, the 2/3 diesel was operable and all incoming lines were l available.

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049555P _CDT/O - . -{QQ ~/ - -- 4, v PMS :1R J AMES G KEPPLET n.~u Rr.GIOjlaL waw: 4 DIRECTOR

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!,               GLEN ELLYN IL 60137                                                                                                           U*                    '

fl SU3 JECT DPR-19 DRESDEN NUCLE AR POWER ST ATION UNIT I 2. THIS WILL CONFIRM A CONFIRMATION WITH MR. F. MAURA 0F b YO'JR OFFICE AT 1420 HOURS THIS DATE CONCERNING A TRIP 0F l THE UNIT 2 STAND BY DIESEL GENERATOR DUING AN b OPER A3ILITY TEST FOLLOWING MAINTENANCE. THE DIESEL O

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HAD OPERATED FOR APPRO XIMATELY 40 MINUTES PRIOR TO T!!E TRIP, b WHICH WAS CAUSED BY DIFFERENCIAL FAULT. IT WAS DETERMINED THAT ll O

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. A FAULTY CONNECTION ON A FUSE HOLDER CLIP FOR THE CURRENT ,- l sr-izn &WFERENCI AL RELAY CAU3ED AN ARCING FROM THE MOVA3LE FUSE C t . l 3 l l l i )

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l k j( l CLIP TO ST ATION ARY CONNECTO R. ALL FUSES ASSOCI ATED WITH THIS l i, ( RELAY (3) WERE SU3SEQUENTLY REPL ACED WITH MORE POSITIVE ! C0 !)1E CT I .1G FUSE CLIP. THIS NOTIFICATION WILL FOLLOWED WIIH A TEN b DAY REPORT l I W P WORDEN SUPERINTENDEST ( DRESDEN fl0 CLEAR POWER ST ATION COMMONWE ALTH EDISON COMPANY !( RR I MORRIS ILLINDIS i J ( , 1911 i i ' .-7 , l(' l L {. k SF-1201 (R5 89) } l k

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          #41ss 4%                                799 ROOSEVELT ROAD                            ygtzpunug GLEN ELLYN. ILLINOIS 60137                      (312)85s.2660 A. RO Inspection Report No.

Transmittal Date  : Distribution: Distribution: RO Chief, FS&EB RO Chief, FS&EB RO:HQ (5) RO:HQ (4) DR Central Files L:D/D for Fuels & Materials Regulatory Standards (3) DR Central Files Licensing (13) RO Files R0 Files B. RO Inquiry Report No. Transmittal Date  : Distribution: Distribution: R0 Chief, FS&EB RO Chief, FS&EB RO:HQ (5) RO:HQ DR Central Files DR Central Files Regulatory Standards (3) RO Files Licensing (13) RO Files C. Incident Notification From: Commonwealth Edison Co. Docket No. 50-237 (Licensee & Docket No. (or License No.) , Transmittal Date  : March 13, 1974 Distribution: Distribution: R0 Chief, FS&EB RO Chief, FS&EB RO:HQ (4) RO:HQ (4) Licensing (4) L:D/D for Fuels & Materials f DR Central Files DR Central Files RO Files RO Files i l l l 1 - 21@M 2 wy W}}