ML19269E411

LER 79-054/01T-0 on 790615:cracks in 4,160 Volt Emergency Sys Nonsegregated Bus Insulation Sleeving Observed.Caused by Incompatibility Between Lexan Sleeving Matl & Versa-Fab Varnish Tape.Cracks Repaired W/Recommended Tape

ML19269E411
Person / Time
Site:	Crystal River
Issue date:	06/15/1979
From:	Cooper J FLORIDA POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19269E409	List: ML19269E408 ML19269E411
References
LER-79-054-01T, LER-79-54-1T, NUDOCS 7906280146
Download: ML19269E411 (2)

Text

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tvcNT cESCnierioN ANo enesasLt CosstCVENCES h g ;On 15 June 1979 it was determined that the insulation cracks observed durine I i

, the inspection of the 4160V E.S. non-segregated Bus insulation sleeving I

, , , , could have been caused by material incompatibility. This created an event I

, , , reportable under Technical Specification 6.9.1.8.i' Redundancy NA. No g g ,effect upon public health and safety as the plant was in a safe shutdown I

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,Lexan sleeving material and the Versa-Fab varnish tape. The cracks were i repaired with a manufacturer's recommended tape and the Bus Hi-pot tested i g gunder modification 79-5-73. The 4160V E.S. Bus will be resleeved in another l y

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SUPPLEMENTARY INFORMATION Report No.: 50-302/79-054/0lT-0 Facility: Crystal River Unit #3 Report Date: 15 June 1979 Occurrence Date: 24 May 1979 (determined at plant 15 June 1979)

Identification of Occurrence:

Possible degradation of the 4160V Engineered Safeguards Bus insulation.

Conditions Prior to Occurrence:

Mode 5 cold shutdown.

Description of Occurrence:

On 15 June 1979 it was determined that the insulation cracks, observed during the 24 May 1979 inspection of the 4160V E.S. non-segregated Bus insulation sleeving could have been caused by material incompatibility. This created a condition reportable under Technical Specification 6.9.1.8.1. All deficient areas on the 4160V E.S. Bus were repaired with a manufacturer's approved tape under modifica-tion M79-05-73.

Designation of Apparent Cause:

The cause of this event may be attributed to an incompatibil-ity between the Lexan insulation sleeving and the Versa-Fab varnish tape.

Analysis of Occurrence:

No effect upon public health and safety as the plant was in a safe shutdown condition. Emergency diesel generators were available and operable.

Corrective Action:

The 4160V E.S. Bus was repaired by adding additional manufact-urer approved taping. Hi-pot testing was performed to assure reliability. The insulation sleeving will be replaced under another modification during the next scheduled refueling outage.

Failure Data:

This is the first occurrence of this type reported.

/rc 2172 172