ML20126B249

Safety Evaluation Re Steam Generator Water Hammer at Facility.Water Hammer Unlikely

ML20126B249
Person / Time
Site:	Maine Yankee
Issue date:	12/31/1979
From:	Office of Nuclear Reactor Regulation
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ML20126B248	List: ML20126B245 ML20126B249 ML20126B253
References
NUDOCS 8003100151
Download: ML20126B249 (4)

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JAN 171960 MEMORANDUM FOR: R. Reid, Chief, Operating Reactors Branch #4, 00R FROM: G. Lainas, Chief, Plant Systems Branch, 00R

SUBJECT:

MAINE YANKEE STEAM GENERATOR WATER HAMMER EVALUATION Plant Name: Maine Yankee Atomic Power Station Docket No.: 50-309 Responsible Branch: ORB #4

, Project Manager: M. Fairtile Reviewing Brancn: Plant Systems Branch Review Status: Complete In response to Technical Assistance Request, TAC No. 7191, regarding water hammer in the Maine Yankee feedwater systems, the Plant Systems Branch has completed its review and found that acceptable precautions are being taken to minimize the occurrence of water hammer in the feedwater piping. The basis for our conclusions are provided in the enclosed Safety Evaluation Report and our consultants' report dated December 1979.

This completes our review of steam generator water hammer under TAC No. 7191.

. M G. Lainas, Chief Plant Systems Branch Division of Operating Reactors

Enclosures:

As stated

Contact:

S. MacKay X-27111 cc w/ enclosures:

See page 2 800s;anjfl ,

JAN 171980 cc w/ enclosures:

D. Eisennut

5. Hanauer B. Grimes

• E. Adensam W. Gannill M. Fairtile S. MacKay

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SAFETY EVALUATION REPORT 1

STEAM GENEPATOR WATER HAMMER MAINE YANKEE ATOMIC POWER STATION DOCKET NO. 50-3C9 DECEMBER 1979 1

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1.0 INTRODUCTION

Steam generator water hammer has occurred in certain nuclear power plants as a result of the rapid condensation of steam in a steam generator feedwater line and the consequent acceler' tion of a slug of water which upon impact within the piping system causes undue stresses in the piping and its support system. The significance of these events varies from plant to plant. Since a total loss of feedwater could affect the ability of the plant to cool down after a reactor shutdown, the NRC is concerned about these events occurring, even though an event with potentially serious consequences is unlikely to happen.

Because of the continuing occurrence of water hammer events, the NRC, in September 1977, informed all PWR licensees that water hammer events due to the rapid condensation of steam in the feedwater lines of steam generators represented a safety concern and that further actions by licensees for Westinghouse and Combustion Engineering designed nuclear I steam supply systems are warranted to assure that an acceptably low risk to public safety due to such events is maintained. Accordingly, these ,

licensees were requested to submit proposed hardware and/or procedural l modifications, if any, which would be necessary to assure that the feedwater lines and feedrings remain filled with water during nomal as well as transient operating conditions. At the same time, the NRC ,

1 provided each PWR licensee with a copy of its consultant's report, "An Evaluation of PWR Steam Generator Water Hamer," NUREG-0291.

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-2 The evaluation of the potential for steam generator water hammer at the Maine Yankee plant shows that the feedwater piping adjacent ,to the steam generator consists of a favoraoly short run of horizontal' piping and' I

that during seven years of successful operation it has experienced those conditions that might induce steam genera +ar water hammer; but no water hanner has occurred.

2.0 EVALUATION Our consultant EG&G Idaho Inc., prepared the attached evaluation of steam generator water harter at the Maine Yankee Plant as part of our technical assistance program. (Letter from J.A. Cearien, EG&G, to R.E. Tiller, 00E, dated Cecember 13, 1979.) We have reviewed this report together with the licensees submittals listed under item 4.0, 3.0 CO.';CtUS ION Based on our knowledge of water hammer phenomena, and our review of the licensees responses and the enclosed evaluation report, we concur with our consultants' conclusien that the potential for steam generator water hammer is sufficiently low to perm,it continued operation of this

. facil ity. However, even though steam generator water hamer is not likely to occur, the licensee should be vigilant and nonitor for water hanners that might impose significant stresses on the piping systems or their supports. We will continue to monitor reports from this licenses for indications of possible water hammer. If i

such indications appear in the future, this matter will be reexamined and any result in additional requirements to reduce /'

the probabflity of steam generator water hanmer at these facilities.

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We have concluded that steam generator water hammer is not likely to occur at this facility and, therefore, we find no undue risk to the health and safety of the public as a result of the continued

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operation of the Maine Yankee Atomic Power Station.

4.0 REFERENCES

4 4.1 J.L. French, Maine Yankee Atomic Power Company (MYAPC), letter to R.A. Purple, NRC,

Subject:

" Response to May 13, 1975 letter on Steam Generator Water Hammer," July 14, 1975.

4.2 R.H. Groce, MYAPC, letter to R.W. Reid, NRC,

Subject:

"Feedline Water Hammer," November 25, 1977.

a.3 C.C. Fri::le, MY'PC, letter to R. Colmar, NRC,

Subject:

" Maine Yankee Steam Generator Feedwater Piping," June 6,1979.

4.4 0.E. Moody, MYAPC, letter to R. Reid, NRC, dated November 15, 1979, in resconse to NRC request for information regarding the potential for steam generator water hammer.

4.5 J. A. Block, et al, An Evaluation of PWR Steam Generator Water Hammer, Creare, Inc., NUREG-0291 (December 1976).

I 4.6 W.E. Bennett, Waterhammer in Steam Generator Feedwater Lines,  !

Westinghouse Technical Bulletin, NSD-TB-75-7, June 10,1975.

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