ML20005B348
| ML20005B348 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/26/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20005B347 | List: |
| References | |
| NUDOCS 8107070519 | |
| Download: ML20005B348 (3) | |
Text
St.FETY EVALUATION REPORT BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 7 TO FACILITY OPERATING LICENSE DPR-77 TENNESSEE VALLEY AUTHORITY NUREG - 0737 Requirement (Item II.K.3, C.3.10)
For Westinghouse-designed reactors. if the anticipatory reactor trip upon turbine trip is to be modified to be bypassed at power levels less than 50 percent, rather than below 10 percent as in current design, demonstrate that the probability of a small break LOCA resulting from a stuck open POR7 is not significently changed by this raodification.
Discussion Analyses performed for the Sequoyah Units have shown thst a 26 psi margin between peak system transient pressure and the PORY actuat h n setpoint is predicted for turbine trip without anticipatory reactor trip at R percent of rated power.
The LOFTRAN computer code used to perform these predictions for Sequoyah Units 1 and 2 is under review by the staff and has been used by Westing-house in previous comparisons (one of these being Farley-Unit 2) with plant startup tests for 50 percent load rejection where code predictions were found to be conservative relative to test results. Neither the tests j
nor the predictions have resulted in, or shown the occurrence of. PORV chall.enges.
The predictions computed for the Sequoyah units are further supported by the most recent results measured in a turbine trip test performed at 50% power on the Farley-Unit 2 plant, which is similar in licensed power level and design to the Sequoyah units.
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j This Farley test, performed to verify analytical predictions, demonstrated a peak transient pressurizer pressure of 2260 psia, allowing a 90 psi margin to the PORY setpoint pressure. The predicted margin had been 50 psi, so that the predicted peak pressure was shown to be conservative.
Based on the computed predictions for Sequoyah Units 1 and 2, and the tests results obtained from another similar licensed plaat, it is concluded that operation of the plant at 50 percent rated power or below without the anticipatory reactor trip tie to the turbine trip will no.t significantly change the probability of a small break LbCA due to a stuck open PORV, thereby satisfying the reouirements of this item of the Action Plan.
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 significant environmental impact. Having made this determination, we have further concluded that the amendment involves an action which is insigni-ficant from the standpoint of environmental impact and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact statement or negative declaration and environmental impact appraisal 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 prob-ability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration; (2) there is reasonable assurance that the
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the healtn 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 regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public~.
Date: June 26, 1981 i
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