ML20072F256
| ML20072F256 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/16/1983 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20072F254 | List: |
| References | |
| NUDOCS 8303230433 | |
| Download: ML20072F256 (3) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMEN 0HENT NO. 27 TO FACILITY OPERATING LICENSE DPR-77 i
AND AMENDMENT NO.16 TO FACILITY OPERATING LICENSE DPR-79 TENNESSEE VALLEY AUTHORITY INTRODUCTION Tennessee Valley Authority (TVA) forwarded a letter dated September 17, 1982, requesting an amendment to their operating license to allow an extension of the j
time interval required to conduct analog channel operational tests of the Engi-neered Safety Features Actuation System (ESFAS) and Reactor Trip System (RTS) from one month to three months.
The staff's evaluation is based upon data accompanying the original request, supplemental infonnation provided in a December 29, 1982, letter, and the independent analysis of additional data provided by the licensee.
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EVALUATION The plant Technical Specifications require that analog channel operational tests be conducted monthly.
These tests verify the operability of the analog channel bistable devices and include adjustment of setpoints, if required, to assure that safety actions will be initiated within the limits of the allowable values speci-fled in the plant Technical Specifications.
The frequency specified for conduct-ing these tests is that indicated in NUREG-0452, Rev. 4, " Standard Technical Specifications for Westinghouse Pressurized Water Reactors". The September 17 letter forwarded the results of test data and requested that the plant Technical Specifications for selected ESFAS and RTS bistables be changed to permit testing at quarterly rather than monthly. intervals.
Review of the September 17 submittal disclosed that no units failed and only minor changes in setpoints were made due to drift in any given month.
The staff requested additional data from the licensee as to whether trends were observed or drift rates calculated by which it could be inferred that a unit would not drift beyond the allowable value in three months.
The December 29 letter indicated that no trends were found and that drif t rates would not have exceeded the allowable value if the test interval were extended to three months.
The staff conducted an independent review of a random sample of test data which consisted of 1500 out of 3700 pages.
The review confirmed that the bistable set-points are very stable with time. Drift rates where found to be randon did not exhibit any trends.
Most units exhibited a slight burn-in drift usually under 0.25% and of less than three months' duration.
After burn-in some units showed a drift of less than 0.107. but most units showed zero drift rate.
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< Therefore, we conclude that extension of the test interval to quarterly should not result in setpoints drifting beyond the allowable values specified in the Technical Speci fications.
The September 17 submittal and the Westinghouse Owners' Group Subcommittee on Tech-nical Specifications have presented several additional considerations. When the instrument channel is in test the plant is in a 1/2 trip condition.
In this state it is more vulnerable to spurious safeguards actuation caused by single failures or operator error.
The proposed change would reduce operation in this state by 392 hours0.00454 days <br />0.109 hours <br />6.481481e-4 weeks <br />1.49156e-4 months <br /> per year.
Setpoint checking is labor intensive in terms of instrument mech-anic time and unit operator time.
If the testing is reduced it would save 2058 man-hours and $51,450.00 per year.
The constant cycling of equipment for testing purposes can shorten conponent lifetines and contribute to early onset of failure.
Sensitivity studies have demonstrated that extending test intervals fraa monthly to quarterly only decreases channel reliability by 8.6%. but since all systems have redundant channels and require 2 out of 3 or 2 out of 4 channels to trip, the over-all impact on reliability is even less.
The slight reliability gain relative to the economic burden imposed is a valid con-sideration for a decision in favor of extending the interval for bistable setpoint surveillance.
The extension of test interval for the selected RTS and ESFAS bistables, identified in the Septanber 17 transmittal, from one month to three months (quarterly) for Sequoyah Units 1 and 2 is acceptable.
This would not jeopardize the safety of the plant, and could actually result in improved safety by reducing the possibility of human error or inadvertent actuation of safety systems.
ENVIRONMENTAL CONSIDERATION We have determined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any signif-icant environmental impact.
Having made this determination, we have further con-cluded that the amendment involves an action which is insignificant from the stand-point of environmental impact and, pursuant to 10 CFR @51.5(d)(4), that an environ-mental impact statement or negative declaration and environmental impact appraisal i
need not be prepared in connection with the issuance of this amendment.
CONCLUSION We have concluded, based on the considerations discussed above, that: (1) because the amendment does not involve a significant increase in the probability or con-l sequences of accidents previously considered, does not create the possibility of an accident of a type different from any evaluated previously, and does not i
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8 involve a significant decrease in a safety nargin, the a:sendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regu-lations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of tim public.
Date: March 16, 1983 Principal Contributors: Pelanie 11111er, Licensing Branch No. 4,DL Carl Stahle Licensing Branch No. 4, DL Rudy Karsch, Instrumentation and Control Systems Branch, DSI
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