ML20153F279

Advises of Concern Re Prolonged Low Power Operation on Reliability of Check Valves & Requests Review of Subj. Experience Showed That Accelerated Wear & Failure of Some Valves Could Occur Due to Undesirable Flow Operations

ML20153F279
Person / Time
Site:	River Bend
Issue date:	09/01/1988
From:	Paulson W Office of Nuclear Reactor Regulation
To:	Deddens J GULF STATES UTILITIES CO.
References
NUDOCS 8809070179
Download: ML20153F279 (4)

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. ~ UNITED siSTEs 8 NUCLEAR REGULATC RY COMMISSION r, , WASHINGTON, D. C. 20655

'$ , , , , , # September 1,1988 Docket No. 50-458 Gulf States Utilities ATTN: Mr. James C. Deddens SeniorVicePresident(RBNG)

, Post Office Box 220 St. Francis (111e, Louisiana 70775

SUBJECT:

THE IMPACT OF PROLONGED LOW POWER OPERATION ON THE RELIABILITY OF CHECK VALVES

Reference:

Letter from M. O. Medford to NRC, "Investigation Report, San Onofre Unit 1 Wa'er Hamer Event of November 21, 1985." dated April, 1986.

Check valves are used in many systems important to plant safety and reliability.

Failure of check valves can lead to overpressurization of low-pressure systems, i

! water hamer, steam binding, and extentive day. age to other components at nuclear power plants. ,

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Recent industry experience showed that accelerated wear and failure of certain check valves could occur due to continued undesirable flow operations. The  !

primary cause of this premature degradation is continuous fluctuation of the check valve disc when it is not firinly held against the backstop by the fluid forces pushing on it. The position of the check valve disc can be determined by a balance of fluid lifting force and the gravitational force acting on the L disc and hinge arm weights. Low flow velocities are not sufficient to lift the disc through its full stroke and hold it firm'y in a stable position against a stop. With each minor flow pulsation, the disc then fluctuates

causing premature wear of moving parts. This instability if coupled with J close proximity upstream flow disturbance such as elbows, tees, control valves l and pu ;' could cause rapid wear and in some cases even failure of the valves.

An analysis (Reference 1) was perfomed to identify the root causes of check  !

! valve failures during the November 21, 1985, water hosper event et San Onofre t Nuclear Generation Station, Unit 1. That analysis concluded that the failure l of the five failed check valves was caused by repeated hasmering of the disc  ;

r stud and the stud nut against the backstop due to insufficient disc lifting '

force of the low flow rate during reduced power operation. The plant had been operating at reduced power an'J the reduced feedwater flow, coupled with a high level of turbulence due to increased throttling of the flow control valve,  ;

! resulted in an amplified oscillation and accelerated degradation. Eventually '

l it led to failures of the check valves.  ;

j Based on the above discussion, it is reasonable to conclude that certain check 1 i

valves are very vulnerable to prolonged reduced flow operation during reduced l power operation. Therefore, I am advising you of this concern and requesting l

8809070179 880901 J

PDR ADOCK 05000450 f 1 p PNV

e fir. arres C. Deddens September 1, 1988 that you review your plant configuration for possible irrpact of prolonged low power operation on the reliability of check valves.

This leste. : eiteirae no formal response.

Sincerely, f

' falter A. Paulson, Project F'anager Project Directorate - !Y Division of Reactor Projects - Ill, IV, Y and Special Projects cc: See next page DISTRIBUTION 9etfet TlW NRC PCR Local PCR PD4 Reading L. Rubenstein J. Calvo P. Noonan W. Paulson OGC-Rockville E. Jordan B. Grires ACRS (10)

PD4 Plant File T. Westerran, RlY PD4/LA PDkk PDI PNoonan WPaulton:sr hvJCalvo Oj/I/88 08/ /88 l) (j/c)/E8

Mr. James C. Deddens September 1,1988 that you review your plant configuration for possible impact of prolonged low power operation on the reliability of check valves.

This letter requires no formal response.

Sincerely, k' W Walter A. Paulson, Project Manager Project Directorate - IV Division of Reactor Projects - !!!,

IV, Y and Special Projects cc: See next pace

,.k Mr.

• James C. Deddens Gulf States Utilities Company River Bend Nuclear Plant cc:

Troy B. Conner, Jr., Esq. Mr. J. E. Booker Conner and Wetterhahn Manager-River Bend Oversight 1747 Pennsylvania Avenue, NW P. O. Box 2951 Washington, D.C. 20006 Beaumont, TX 77704 Mr. Les England Mr. William H. Spell Administrator Director - Nuclear Licensing Nuclear Energy Division Gulf States Utilities Company Office of Environmental Affairs P. O. Box 220 P. O. Box 14690 St. Francisville, LA 70775 Baton Rouge, Louisiana 70898 Richard M. Troy, Jr., Esq.

Assistant Attorney General in Charge Mr. J. David McNeill, !!!

State of Louisiana Department of Justice William G. Davis, Esq.

234 Loyola Avenue Department of Justice New Orleans, Louisiana 70112 Attorney General's Office 7434 Perkins Road Resident Inspector Baton Rouge, Louisiana 70808  :

P. O. Box 1051 St. Francisville Louisiana 70775 H. Anne Plettinger l' 3456 Villa Rose Drive 3

Gretchen R. Rothschild-Reinike Baton Rouge, Louisiana 70806 Louisianians for Safe Energy, Inc.

2108 Broadway Street New Orieans, Louisiana 70118-5462 President of West Feliciana Police Jury Regional Administrator, Region IV P. O. Box 1921 U.S. Nuclear Regulatory Commission St. Francisville, Louisiana 70775 j Office of Executive Director for Operations Mr. Frank J. Uddo 1 611 Ryan Plaza Drive Suite 1000 Uddo & Porter 1

Arlington, Texas 76011 6305 Elysian Fields Avenue Suite 400 Philip G. Harris New Orleans, Louisiana 70122 i i Cajun Electric Power Coop. Inc.

l 10719 Airline Highway 1 P. O. Box 15540 Baton Rouge, LA 70895 1

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