ML19270F059
| ML19270F059 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/19/1978 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML19270F058 | List: |
| References | |
| NUDOCS 7901250097 | |
| Download: ML19270F059 (1) | |
Text
ENCLOSURE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 REDUCED SI' ELOW AT L0h REACTOR COOLANT SYSTEM LEVELS NCR 1011 SECOND INTERIM REPORT Interin Progress TVA and Westinghouse have completed the installation of the modified orifice design.
Procedures for conducting retest of the accumulators are presently being reviewed and approved.
Retest of the accumulators should be completed by late February.
79012500 %
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TENNESSEE VALLEY AUTHORITY CH ATT ANOOG A. TENNESSEE 374o1 830 Power Building UC,1171973 Mr. James P. O'Reilly, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Cocnission Region II - Suite 3100 101 Marietta Street Atlanta, Georgia 30303
Dear Mr. O'Reilly:
SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 - REDUCED SIS FLOW AT LOW REACTOR COOLANT SYSTEM LEVELS - NCR 1011 - FIRST INTERIM REPORT The subject deficiency was initially reported to NRC-OIE Inspector J. K. Rausch on September 18, 1978.
Enclosed is our first interim aport. We will transmit our next report to your office by December 15, 1978.
If you have any questions concerning this matter, please get in touch with M. R. Wisenburg at FTS 854-2581.
Very truly yours, f J. E. Gille and Assistant nager of Power Enclosure ec:
Mr. John G. Davis, Acting Director (Enclosure)
Office of Inspection and Enforcement U.S. Nuclear Regulatory Cocnission Washington, DC 20555 62 :Ilv og;3p,~
VIDUOre.u,"*'.y
'??c.F.'a An Equal Opportunity Employes
ENCLOSURE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 REDUCED SIS FLOW AT LOW REACTOR COOLANT SYSTEM LEVELS - NCR 1011 FIRST INTERIM REPORT Description of Deficiency Blowdown testing of the Safety Injection System accumulators at Sequoyah revealed an injection pipirg flow resistance (f L/D factor),
as calculated from the test results, that varies with backpressure the injection points to the reactor coolant system. The variation atis apparently due to the backpressure effect on cavitation occuring downstream of the injection line orifice.
Reduced backpressures (caused by low reactor coolant pressures) result in cavitation which reduces the expected injection flow rates.
The flow may be reduced enough to invalidate injection 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 Bar Nuclear Plant.
Corrective Action Westinghouse has proposed a modified orifice design which includes a new orifice at the accumulator nozzle. This new design should eliminate the cavitation and its effects on the injection line flow resistance.
Subsequent tests will verify the adequacy of the action.
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