ML20030C149
| ML20030C149 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/24/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-81 10CFR-050.55E, 10CFR-50.55E, NCR-SWP-79-S-5, NUDOCS 8108250435 | |
| Download: ML20030C149 (2) | |
Text
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TENNESSEE VALLEY AUTHORITY adC.C
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CH ATTANOOGA. TENN ESSEE 374ol
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400 Chestnut Street Tower II W,.
r nf March 24. 1981
,l l9QE%7c A b'O Mr. James P. O'Reilly, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region II - Suite 3100 101 Marietta Street Atlanta, Georgia 30303
Dear Mr. O'Reilly:
SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 - EXCESSIVE OUTPUT FLUCTUATIONS OF FOXBORO INSTRUMENTATION - NCR SWP-79-S SIXTH INTERIM REPORT The subject deficiency was initially reported to NRC-0IE Inspector M. J. Gouge on August 28, 1979, in accordance with 10 CFR 50.55(e).
Interim reports were submitted on September 26 and October 30, 1979, February 5, and August 11, 1980, and February 9, 1981. Enclosed is our sixth interim report. We expect to submit our next report by July 2, 1981. We consider 10 CFR 21 applicable to this deficiency.
If you have any questions, please get in touch with D. L. Lambert at FTS 857-2581.
.Very truly yours,
, TENNESSEE VALLEY AUTHORITY
. %3ALA L
M. Mills, Manager Nuclear Regulation and Safety Enclosure
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cc:
Mr. Victor Stello, Director (Encicsure)
Office of Inspection and Enforcement l
U.S. Nuclear Regulatory Commission
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Washington, DC 20555 i
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i ENCLOSURE SEQUOYAH' NUCLEAR PLANT I"'ITS 1 AND 2 EXCESSIVE OUTPUT FLUCTUATIONS OF FOXBORO INSTRUMENTATION NCR SWP 79-S-5 10 CFR 50.55(e)
SIXTH INTERIM REPORT Description of Condition Personnel at Sequoyah Nuclear Plant have noted erroneous output' signals coming from Foxboro equipment containing magnetic amplifiers (current /
. current repeaters and square root converters). This instrumentation was supplied by Westinghouse on the NSSS contract. The equipment is not per-forming according to the specifications in the.Foxboro Equipment Manual
'which specifies this' equipment to have an accuracy of +.5 percent with input voltage variations of. +10 percent.
Tests have sho.wn that a 1.5 and-4.5 percent input variation resulted in a 5.0 and 15.5 percent output current change. These excessive output variations have caused spurious operations of plant equipment by producing erroneous safety injection
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signals. Some of the Foxboro units are used to actuate safeguards equipment and to initiate reactor trip signals. There are 168 modules per.
unit containing magnetic amplifiers at Sequoyah Nuclear Plant.
Interim Progress Westinghouse has developed and tested a field modification kit for the Foxboro instruments that function as current / current repeaters.. The pre-liminary test results indicate. a significant. improvement in performance.
The modification involves regulating the output of the module's de power supply which was determined to be the primary source of magnetic amplifier instability. It appears likely that with this modification the instruments will function acceptably for the. life of the plant. TVA, however, will perform further testing before accepting this change as a permanent -
solution. ~A similar modification kit is bein6 developed for the square root converter instruments.
In order to alDu full power operations, new voltage inverters have been installed at Sequoyah Nuclear Plant units 1 and 2 to reduce the voltage v
fluctuations s'een by the Foxboro modules. Tests have verified that these' new inverters guarantee a closely regulated. voltage to the Foxboro module and that the Foxboro module will p'erform acceptably for Sequoyah Nuclear-Plant units 1 and 2.in.the interim until a permanent solution is implemented for the Foxboro. equipment.
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