ML20206G509

SER Supporting Employee Concern Element Rept 23706, Gassing of Current Transformers

ML20206G509
Person / Time
Site:	Sequoyah
Issue date:	11/04/1988
From:	NRC OFFICE OF SPECIAL PROJECTS
To:
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References
NUDOCS 8811220301
Download: ML20206G509 (2)

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SAFETY EVALVATION REFORT BY THE OFFICE OF SPECIAL PROJECTS EMPLOYEE CONCERN ELEMENT REPORT 23706 "GASSING Or CURRENT TRANSFORMERS

TEhNESSEE VALLEY AUTHORITY i

SEOUOYAH htCLEAR POKER PLANT. UNITS 1 AND 2 j DOCKET f:05. 50-327 AND 50-328 a  !. SUBJECT Category! Engineering (20,000) bbcategory: Electrical Protection Design (23700) '

i Elenent: Gassing of Current Transforrers (23706)

Employee Concernt W!-85-060-hC2 j

The basis for elewnt ceport 23706. Rev. O. dated October 10. '906, is a -

generel TVA employee concern Wi-85-060-h02 which states:

• TVA's problen with gassing of current transformers has led to outages of Ifre ,

and bus ties to obtain oil samples and determine gassing condition." j r

This concern was evaluated by TVA and TVA ccLeluded that these are not 1E (

l 4 safety systers, that ru1tiple cf fsite sources of electricity exist at Sequoyah.

I trd that the complete loss of offsite power is a design basis condition.

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!!. SUM 9ARY OF ISSUE l

TVA evaluated the current transformer's contribution to the safety operation of the Sequoyah plant and cencluded that the cts are in nonsafety systems ard therefore should not be considered as a Sequoyah restart item.  !

'!! EVALUATION I htC and its consultant. SAIC. reviewed the TVA employee concern report. The TVA recort discusses the nor-1E nature of the current transforners, the multiple offsite sources of power to Sequeyah and the requirement that loss cf l offsite power is a design basis accident for Sequoyah. The NRC requested a

' more detailed explanation of the cts that have the gas failure problems  :

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! including voltage, type, vendor, and location (application) of cts at the Secucyah plant. TVA addressed this recuest in a February 10, 1987, meetino ,

s itt MC ir th T'.1 cf fiers in Bethesda. TVA explained that this probler Is

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Q cnly found with the 161 KV current transforwers used in the electrical switch-yards. TVA discussed CT failure reports which showed that 161 KV from all vendors have been randomly failing at aThelarge number reports of that show fossil and this 161nuclear KV CT p} ants at TVA and at other utilities.

issue is an electrical industry problem and that the problem resolution has not TVA discussed the multiple offsite sources with yet been firmly established.

Secuoyah electrica. drawings showing the location of the 161 KV cts and also discussed the diesel generator capabilities as mitigating features should this problem develop at Senuoyah during operation. 4

!V. CONCLUSION Based on the current transforcer failure data and industry data presented at the February 10. 1987, reeting. NRC has concluded that the problem is confined tc the 161 KV application only. Bated on the NRC review of the Sequoyah one i line diagrams, this voltage only exists in the Sequoyah switchyard, hRC believes that cultiple offsite tources exist at Sequoyah to accetredate this problem should it develop, Additionally, the diesel generator is available ,

Hence, this concern is to provice a safe and orderly shutdown at Sequoyah.

censidered to be satisfactorily resolved for Sequoyah.

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