ML19291A886
| ML19291A886 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/11/1979 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML19291A883 | List: |
| References | |
| NCR-MEB-79-24, NUDOCS 7908280702 | |
| Download: ML19291A886 (2) | |
Text
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I ENCLOSURE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 BARTON NARROW RANGE STEAM GENERATOR LEVEL TRANSMITTERS DO NOT MEET ACCEPTANCE CRITERIA FOR ACCURACY NCR MEB 79-24 10 CFR 50.55(e)
FIRST INTERIM REPORT Description of Deficiency This deficiency was discovered by Barton Company and reported to Westinghcuse and subsequently by Westinghouse to TVA.
Barton Company discovered this deficiency during some additional qualification testing Performed at the request of Westinghouse.
It was found by Barton Company that the output of the Lot 1 transmitters shifted with temperature.
Following this discovery, Barton developed a mathematical correlation to relate the available measured check values of output shift induced by temperature compensation to a conservatively predicted maximum inaccuracy for each transmitter in Lot 1.
Based on the Barton Company results, Westinghouse performed an evaluation of the estimated maximum inaccuracy for each transmitter against the functional requirement 2 of the transmitter as installed. As a result of this evaluation, Westinghouse has determined that a number of those Lot 1 units in the steam generator narrow range level function have excessive positive inaccuracies. This is due to the short-term accuracy requirement of this function and the special temperature-induced error characteristic of the differential pressure transmitter.
TVA considers this deficiency reportable because the steam generator narrow range level transmitters control the Auxiliary Feedwater initiation, the low steam generator level reactor trip, and input to a post-accident monitoring channel.
If the steam generator narrow range level transmitters were not corrected, the initiation of Auxiliary Feedwater and low steam generator reactor trip may not have been timely enough to prevent jeopardizing the safe operation of the two nue. lear plants involved.
Sequoyah and Watts Bar Nuclear Plants are the only TVA nuclear plants that have been identified by Barton Company as having the deficient, Lot i narrow range level transmitters. The exact cause of this deficiency is presently being investigated by Barton Company.
Safety Implications If this deficiency had remained uncorrected the steam generator narrow range level transmitters may have led to initiation of protective functions (i.e., AFW initiation and/or low steam generator level reactor trip) too late to provide protection for the plant following an accident or transient due to another cause.
-n,8 i86 7008280
Interim Progress The suspect Lot i narrow range steam generator level transmitters at Sequoyah and Watts Bar Nuclear Plants are being returned to.Barton Company.
(There are five suspect transmitters at Sequoyah and seven at Watts Bar.)
Barton Company will check the output shift over a range of temperature values to confirm whether or not the actual transmitter performance is outside the acceptable band. Where necessary, either circuitry modifica-tions will be made to bring the transmitter performance within specification or the Lot 1 transmitter will be replaced with an acceptable Lot 2 transmitter.
TVA will provide additional information in the final report.
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