ML19253A825

Final Deficiency Rept Re Corrosion of Cable Terminations in Junction Boxes Inside Containment.Corroded Class IE Terminations Will Either Be Replaced W/Insulated Splices or Restored to Original Configuration Using Brass Screws

ML19253A825
Person / Time
Site:	Sequoyah
Issue date:	08/31/1979
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19253A824	List: ML19253A823 ML19253A825
References
NCR-9P, NUDOCS 7909110454
Download: ML19253A825 (2)

Text

N ENCLOSURE -

SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 CORROSION OF CABL" TERMINATIONS IM JUNCTION BOXES INSIDE CONTAINMENT NCR 9P 10 CFR 50. 55 (es FINAL REPOR'.

Description of Condition This NCR was issued based on a problem with corrosion of cable '

terrainations within: (a) junction boxes that were randor..iy sampiec inside unit 1 primary containment, and (b) Foxboro transmitters inside unit 1 primary containment.

Junction boxes Some junction boxes house terminations for field wiring that interfaces with vendor 's equipment and components . T'/A ha s conducted a 100 percent inspection of these. boxes containing terminations in unit 1. The inspection revealed that approximately 5 percent (58 boxes) of these junction boxes contained corroded class 1E terminations. The probable cause of the corrosion is inadequate protection of terminations during. construction.

Foxboro transmitters An inspection of sume Foxboro transmitters inside unit 1 primary containment found some of the cable terminations corroded within the instrument housing.

Information from the vendor indicates that the type of cerminal block used in Foxboro transmitters with a serial number less than 3,000,000 could produce corrosive chemicals when exposed to moisture.

Safety Implications Had this condition gone uncorrected the corrosion of Class lE terminations could have led to a failure of safety-relatec circuitry, thereby advercely affecting the safe operation of the plant. ,

Corrective Action TVA's corrective action on a related NCR (EEB 79-7) is to replace terminations in junction boxes inside containment with splices for Class lE circuits required to achieve and maintain safe shutdcun g909110 f/~

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, e of the reactor for a LOCA or main steamline break (MSLB) . Thus, any corrosion concern will be eliminated when splicing is completed. These circuits will be spliced bef. ore fuel loading of the respective unit.

The remaining junction boxes with corroded Class 1E terminations will be either replaced with insulated splices or restored to their original configuration using brass screws. TVA will inspect for corrosion, all junction boxes containing Class lE terminations in unit 2. Where corroded Class lE terminations are found the same corrective action will be applied.

TVA has conducted a 100 percent inspection of Foxboro transmitters in unit 1 to verify serial numbers. Replacement terminal blocks furnished by the vendor have been' installed in all Foxboro trans-mitters with a serial number less than 3,000,000.

An inspection will be conducted in unit 2 and the terminal blocks in all Class lE Foxboro transmitters with a serial number less than 3,000,000 will be replaced before fuel loading of unit c.

To prevent recurrence of this condition, all other TVA nuclear plant design project managers are being notified of the potential corrosion problem with terminations in junction boxes and Foxboro transmitters. The managers are being instructed to: (a) take action to protect terminations during construction, and (b) ensure that vendor supplied replacement terminal blocks are installed in all Foxboro transmitters with an serial number less than 3,000,000.

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