ML19338G058

Final Deficiency Rept Re Safety Injection Sys Train B Flow Defect.Caused by Cavitation at RHR Heat Exchanger Outlet Valves.Cavitation Eliminated by Opening Valves to 79F in Safety Injection Sys Injection Mode

ML19338G058
Person / Time
Site:	Sequoyah
Issue date:	10/23/1980
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
10CFR-050.55E, 10CFR-50.55E, NCR-SQN-NEB-802, NUDOCS 8010280396
Download: ML19338G058 (2)

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3, 400 Chestnut Street Tower II October 23, 1980 Mr. James O'Reilly, Directcr Office of In ection and Enforce:nent {o - 3 U.S. Nuclear Rt, ulatory Commission Region II - Suit 3100 101 Marietta Stree Atlanta, Georgia 30 3

Dear Mr. O'Reilly:

SEQUOYAH NUCLEAR PLANT UNIT 2 - SIS IRAIN D FLOW DEFICIENCY -

NCA SQN !EB 6025 - FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector M. Thon:aa on August 22, 1980, in accordance with 10 CFR 50.55(e). An interb report was submitted on September 22, 1980. Enclosed is our final report.

If you have any questions, please get in touch with D. L. LamMet at ITS 857-2581.

Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Manager Nuclear Regulation and Safety Enclosure cc: M . Victor 'tello, Director (Enclosure)

Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555 l

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8010280 7d

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SEQUOYAH NUCLEAR PLANT UNIT 2 SIS TRAIN B FLOW DEFICIENCY NCR SQNNES8025 10CFR50.55(e) REPORT FINAL REPORT Description of Deficiene,v During the performance of preoperational test W-6.1E on the SIS System performance, the traf.n B cold leg injection. rate for all four legs simultaneously was caly 4229 gal /cin, as compared to the required -

4500-5000 gal /cin.

This is a continuation of the problem discussed in Sequoyah NCR NEB 79-3 (final report submitted on October 17, 1979). The original RHR system flow problem was pump overload from too much flow because of too little system resistance. The addition of flow restrictors solved that problem; however, low flow (4229 gal / min) occurred in unit 2 because of cavitation at the RHR heat exchanger outlet valves.

s Sa fety Imolications The flow deficiency would result in reduced SIS coolant to the Reactor Coolant System in the event of a LOCA. The flow wois1d be less than that assumed in the plant safety analysis. The reduced coolant so ths reactor, therefore, could result in degradation of the safe operation of the plant. .

Corrective Action ,

j It was determined experimentally that the problem would be solved i

if 60,tba RHRwere open, heatopened exchanger to 79ouglet valves, originally

,. Wegtinghouse designed concurred to be '

with TVA's

request to operate the vgives at 79 open in the SIS injection mode.

4 Opening the valves to 79 allowed the flow to fall in the acceptable 4500-5000 gal /cin range by clininating cavitation. The related I preoperational test deficiency for test W6.1E has been resolved.

All TVA design project managers have been informed cf this problem to prevent recurrences in future plant designs. The Watts Bar Nuclear Plant has a similar flow deficiency discussed in NCR WBNNEE8004.

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