ML19273B420
| ML19273B420 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/09/1979 |
| From: | Gilleland J TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML19273B418 | List: |
| References | |
| NUDOCS 7904060333 | |
| Download: ML19273B420 (1) | |
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<a ENCLOSURE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 REDUCED SIS FLCW AT LOW REACTOR COOLANT SYSTEM LEVELS - NCR 1011 FINAL REPORT Description of Deficiencv Blowdown testing of the Safety Injection System accumulators 4t Sequoyah revealed an inj ection piping flow resistance (f L/D factor), as calculated from the test results, that varies with backpressure at the injection points to the reactor coolant system.
The variation is apparently due to the backpressure ef fect on cavitation occurring downstream of the injection line orifice. Reduced backpressures (caused by lcw reactor coolant pressures) result in cavitation which reduces the expected inj ection ' flow rates.
The flow may be reduced enough to invalidate injectica water assumptions made in the LOCA analysis by Westinghouse.
Because of the similarity of the Watts Bar design to the Sequoyah design,
.this deficiency also affects the Watts 3ar Nuclear Plant.
Safety Implications Had this deficiency. remained uncorrected, the actual accumulator injec-tion flow rates would not have been consistent with those assumed in the ECCS analysis for mitigation of the affects of a LOCA. This would have led to some uncertainty in the response of the plant under LOCA conditions.
Corrective Action TVA and Westinghouse have designed and installed a modified orifice. A retest of the system has been performed successfully.
Expected flow rates compared f avorably with results obtained from the test data. Westinghouse has evaluated the data from the retest based on the plant safety analysis and has app ~aved the results.
790406C M