ML20071H427
| ML20071H427 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 02/24/1982 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-82 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8203080411 | |
| Download: ML20071H427 (2) | |
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TENNESSEE VALLEY AUTHORITY CHATTANOOGA TENNESSEE 374o1 400 Chestnut Street Tower II N
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February 24, 1982 g
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BLRD-50-438/81-08 cn BLRD-50-439/81-08
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U.S. Nuclear Regulatory Commission Region II Attn:
Mr. James P. O'Reilly, Regional Administrator 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303
Dear Mr. O'Reilly:
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 - SOLID STATE AC VOLTAGd RELAYS -
BLRD-50-438/81-08, BLRD-50-439/81 FOURTH INTERIM REPORT The subject deficiency was initially reported to NRC-0IE Inspector M. Thomas'on January 2, 1981 in accordance with 10 CFR 50.55(e) as NCR BLN BLP 8012. This was followed by our interim reports dated February 2, May 14, and September 11, 1981. Enclosed is our fourth
-interim report. We expect to submit our next report by August 4, 1982. We consider 10 CFR Part 21 to be applicable to this deficiency.
If you have any questions concerning this matter, please get in touch with R. H. Shell at FTS 858-2688.
Very truly yours, TENNESSEE VALLEY AUTHORITY 0
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L. M. Mills, Manager Nuclear Regulation and Safety G
Enclosure cc:
Mr. Richard C. DeYoung, Director (Enclosure)
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ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 SOLID STATE AC VOLTAGE RELAYS BLRD-50-438/81-08, BLRD-50-439/81-08 10 CFR 50.55(e)
FOURTH INTERIM REPORT Description of Deficiency The solid state ao voltage relays used en the 6.9 kV Class IE switchgear require a source of do control power for proper operation. The present design configuration of the relays utilizes a contact from the undervoltage relay to energize an auxiliary relay upon detection of an undervoltage condition. The auxiliary relay initiates alarms and breaker trips.
However, when do control power is lost and then restored (such as might accompany a bus transfer), the auxiliary relay will become energized long enough to initiate the supply feeder breaker trip sequence even though an actual undervoltage condition does not exist.
If this were to occur at a time when offsite power was not available and the source of power was the emergency onsite power source (diesel generator), this condition would lead to the inadvertent isolation of a 6.9 kV Class IE switchgear board. In this instance, the boards would have to be manually reconnected.
The 6.9 kV switchgear was designed and supplied by Gould-Brown Boveri, Westminster, Maryland.
Interim Progress The vendor (Brown Boveri Electric) is in the process of factory modifying these undervoltage relays to eliminate dropping out on loss of de voltage.
Instruction manuals for modified type 27 relays have been approved by TVA. The completion date for these modifications has been scheduled for June 1982. TVA is requesting the vendor to improve the schedule.
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