ML20064K601

Discusses 810126 Loss of Annunciation Event at Facility. Caused by Capacitor Shorting.Licensee Will Review Event as Addressed in IE Bulletin 79-27, Loss of Non-Class IE Instrumentation & Control Power Bus During Operation

ML20064K601
Person / Time
Site:	05000000, Sequoyah
Issue date:	01/30/1981
From:	Chiramal M NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
To:	NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
Shared Package
ML082180533	List: IR 05000336/1981026 ML19281E000 ML20027A692 ML20027A705 ML20064J872 ML20064J908 ML20064J926 ML20064K223 ML20064K341 ML20064K366 ML20064K454 ML20064K601 ML20064K609 ML20064K611 ML20064K688 ML20064K756 ML20064K760 ML20064K777 ML20064K791 ML20064K810 ML20064K856 ML20064K866 ML20064K899 ML20064K912 ML20064K923 ML20064K962 ML20064L009 ML20064L056 ML20064L092 ML20064L134 ML20064L148 ML20064L178 ML20064L182 ML20064L247 ML20065E334 ML20065E354 ML20065E375 ML20065E396 ML20065E429 ML20065E466 ML20065H043 ML20065H107 ML20065H219 ML20065H233 ML20065H323 ML20065H444 ML20065H468 ML20065H526 ML20065H662 ML20065H674 ... further results
References
FOIA-82-261 IEB-79-27, NUDOCS 8103050987
Download: ML20064K601 (1)

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tg UNITED STATES y

NUCLEAR REGULATORY COMMISSION E

WASHJ N GTON, D. C. 20555 AE0D/E102 e

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JAN 3 0 1981 This is an internal, pre-

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decisional document not necessarily representing a position of AE0D or NRC.

Fadility:

Sequoyah 1 Event:

Loss of Unit 1 Annunciation Date of Event:

January 26,.1981 l

Discussion:

The event began with the loss of (non-class 1E) which supplies power to Unit 1 and commo'n annunciators only (Unit 2 has a separate inverter for its annunciators).

Inverter failure was due to a capacitor shorting that led to two wave-shaping SCR failures also. As a result of this, the

--output breaker of the inverter tripped.

Alternate. manual transfer was

.. available and 'was used thYee minutes later to re-energize the annunciators.

(The inputs to the inverter are from Class IE 125 Y de battery bus and 600 Y ac bus).

Licensee had overlooked the review of such an event in their response to.

IEB 79-27 (IE had also overlooked this).

Licensee will be doing this review now and will also address other means of supplying rnnunciator power.

[

This inverter, is also by the same manufacturer as the Class IE inverters.

l The inverters have ben subject to several failures in the past.

Licensee has been working on improving the relability of all inverters.

(Ongoing NRC review on inverter failures is continuing).

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The loss of this particular inverter 'does not affect safe opera' tion of the

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plant -- however, the operator would be without annunciators. There is an alarm recorder that will (and did) monitor the loss of the bus. The IEB 79-27 review and subsequent operator training on such an event would improve the situation.

Matthew Chiramal Office for Analysis and Evaluation of Operational Data Gi

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