ML20195B764

Final Deficiency Rept 232-2 Re Westinghouse Type Ds Fused Disconnect Switch.Initially Reported on 880415.Mechanical Connectors Integral to Fuse Mounting Assembly Would Not Adequately Secure Some 8 Awg Wires

ML20195B764
Person / Time
Site:	Limerick
Issue date:	06/15/1988
From:	Kowalski S PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Russell W NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
232-2, NUDOCS 8806210509
Download: ML20195B764 (3)

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. PHILADELPHIA ELECTRIC COMPANY s

2301 MARKET STREET P.O. BOX 8699 PHILADELPHI A. PA.19101 (as s) 8414502 S. J. KOW ALSKI VicE PRESIDENT

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Mr. W. T. Russell, Administrator United States Nuclear Regulatory Cmmission Attention: Docisnent Control Clerk Washington, DC 20555

SUBJECT:

Limerick Generating Station, Unit 2 Significant Deficiency Report No. 232-2 Westinghouse Type DS Fused Disconnect Swltch NRC Construction Permit No. CPPR-107

REFERENCE:

1) Telecon of PECo to NRC, dated April 15, 1988

2) Interim Report, SDR No. 232-2, dated May 13, 1988 FILE: QUAL 2-10-2 SDR No. 232-2

Dear Mr. Russell:

In ccrnpi tance with 10CFR50.55Ce), we are sutmitting our final Significant Deficiency Report concerning the subject Westinghouse Type DS Fused 01sconnect Swltches.

We trust that this satisfactorily resolves the ' tem. If further information is required, please do not hesitate to contact us.

Sincerely, ddMC/GHR/06138801 Attachment Copy to: W. T. Russell, Adninistrator U.S. Niiclear Regulatory Cmmission, Region 1 631 Park Avenue King of Prussia, PA 19406 R. A. Grarrm, Senior Resident Inspector Linerick Generating Station - Unit 2 U.S. Nuclear Regulatory Conmission P.O. Box 46 Sanatoga, PA 19464 f 1

8806210509 880615 PDR ADOCK 05000353 l

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NUCLEAR ENGINEERING ENGINEERING DIVISION N2-1, 2301 Market Street Significant Deficiency Report - SDR No. 232-2' Westinghouse Type DS Fused Disconnect Switches Limerick Generating Station, Unit 2 NRC Construction Permit No. CPPR-107 Description of Deficiency OurIng the connectton of Unit 2 fleid cables to Westinghouse Type DS fused disconnect switches used in B-K electrical panels, it was noted that mechanical connectors Integral to the fuse mounting assenbly

-would not adequately secure scme 98 AWG wires although the connectors themselves were marked 914-1/0. This condition was docunented on Bechtel NCR No. 12991 and PECo SNCR S-1-E This condition has the potential to result in excessive heating of the cable connector interface, or a cable could possibly becane disconnected, thereby disabilng a circuit. The connector is designed with a set screw engaging threads within the fuse clip holder. Scrne set screws, when Inserted into the block to the maximtm depth (determined by the block's threading) do not contact the opposing face of the block.

A sample of connectors removed from Unit 2 indicated a large variation in the gap that results after setting the screw to its maximtm depth. In certain Instances, connectors with the widest gaps 1 could not be used to adequately terminate wires up to size 46 AWG, 4

At Limerick Generating Station, #10 AWG wires (the smallest used for power conductors) are terminated with a ecnpression lug and t do not use mechanical connectors. -

Corrective Action Connections using size 98 AWG and #6 AWG wires were roterminated with compression lugs similar to the #10 AWG wires.

Connections where two 58 AWG wires are in tandem on a single connector were detenninated and inspected for thread depth. If the l connector was Inproperly manufactured, the connector was replaced with a properly manufactured connector and the #8 AWG wire pair was reterminated.

In the case of the #8 AWG wire pairs, the mechanical screw could be tightened as designed and provides a good electrical connection. Corrective

' action described above was performed per disposition of the NCR and SNCR,  ;

which were closed on 4/26/88 end 4/25/88, respectively.  ;

Action to Prevent Recurrence The Limerick Generating Station Specification, Wire and Cable, Notes and Details, E-1412, Rev.15, Section 4.5 specifies conpression terminations for all power cables. The use of vendor supplied mechanical connectors in B-K electrical panels, addressed in this SDR,Is permitted by exception A to 4.5 of E-1412. Because all mechanical connector deficiencies in B-K electrical panels have been identified and corrected under Bechtel NCR No. 12991 and PECo. SNCR S-1-E, no action to prevent recurrence is required.

Safety implications These mechanical connectors are used in all four divisions of the safeguard 125 Volt D.C. systan. Loose wire connections can be postulated to cause a loss of 125 Volt D.C. paaer to all four divisions of several Class 1E circuits, thereby, Jeopardizing plant safety. Therefore, this deficiency, if left uncorrected, could have affected the safe operation of the plant.

JJMC/GHR/06138802

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