ML19322E334

Safety Evaluation Concluding That Acceptable Precautions Are Being Taken to Minimize Occurrence of Water Hammer in Feedwater Piping Sys

ML19322E334
Person / Time
Site:	Maine Yankee
Issue date:	03/12/1980
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML19322E333	List: ML19322E332 ML19322E334
References
NUDOCS 8003270205
Download: ML19322E334 (3)

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SAFETY _ EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION STEAM GENERATOR _yATER HAMMER MAINE YANKEE ATOMIC p0NER STATION DOCKET NO. 50-309

1.0 INTRODUCTION

Steam generator water hamer 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 acceleration 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 steam supply systems are warranted to assure that an acceptably low risk to public safety due to such events is maintained. Accordingly, th'ese licensees were requested to submit proposed hardware and/or procedural modifications, if any, which would be necessary to assure that the feedwater lines and feedrings remain filled with water durir.g normal as well as transient operating conditions. At the same time, the NRC provided each PWR licensee with a copy of its consultant's report, "An Evaluation of PWR Steam Generator Water Hamer," NUREG-0291.

8003270 7 C} 6

-2 The evaluation of the potential for steam generator water hamer 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 that du' ring seven years of successful operation it has experienced those conditions that might induce steam generator water hamer, but no water har.ner has occurred.

2.0 EVALUATION Our consultant, EG&G Idaho Inc., prepared the attached evaluation of steam generator water hacer at the Maine Yankee Plant as part of our technical assistance program.

(Letter from J.A. Ocarien, EG&G, to R.E. Tiller, DOE, dated December 13, 1979.) We have reviewed this report together with the licensees submittals listed under item 4.0.

3.0 CO.;CLU510N Based on our knowledge of water hamer 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 hamer is sufficiently low to perm,it continued operation of this facil ity. However, even though steam generator water ha:aner is not likely to occur, the ifcensee should be vigilant and sonitor for water hamers that might impose significant stresses on the piping systems or their supports. We will continue to monitor reports from this licensee fer indications of possible water hanner.

If such indications appear in the future, this matter will be 1

reexamined and may result fn additional requirenents to reduce the probability of steam generator water hanener at these facilities.

4 1 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 operation of the Maine Yankee Atomic Power Station.

4.0 REFERENCES

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.

4.3 C.D. Frizzle, MYAPC, letter to R. Colmar, NRC,

Subject:

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

4.4 D.E. Moody, MYAPC, letter to R. Reid, NRC, dated November 15, 1979, in response 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 Hamner, Creare, Inc., NUREG-0291 (December 1976).

4.6 W.E. Bennett, Waterhammer in Steam Generator Feedwater Lines, Westinghouse Technical Bulletin, NS0-TB-75-7, June 10,1975.

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$D E6E6 Idaho, Inc.

p. o. som is2s ieano rens. secio suoi December 13, 1979 f

Mr. R. E. Tiller, Director Reactor Operations and Programs Division Idaho Operations Office - 00E Idaho Falls,10 83401 MAINE YANKEE POWER STATION STEAM GENE?ATOR WATER HM ER TECHNICAL EVALUATION (A6257) - JAD-250-79 Ref:

J. A.

Dearien Ltr to R. E. Tiller,

PWR Steam Generator Water Hamer Reviews (A6257) - JAD-225-79, November ~ 8,1979

Dear Mr. Tiller:

The attachment completes the assessment of the effectiveness of the existing means to reduce tie potential for steam generator water hammer at the Maine Yankes Power Station (MYPS).

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We have reviewed the c:erating history of the MYPS pertinent to f

l steam generator water hamer and the related operational and proce-dural characteristics of the feedwater systam. The review has shown that conditions conducive to steam generator water har=er have occurred at the MYPS but no water ha=er events have been ob-served. The conditions have been encountered during normal operating transients and startup and shutdown operations. Such conditions would also be expected in the future during the normal and accident operating situations addressed in the review.

Based on this review we have concluded that the potential for steam gen-erator water hammer is sufficiently low to permit continued opera-tion of this facility.

This transmittal constitutes completion of the MYPS SER, Task A6257 of the referenced Milestone Chart.

Very truly yours, wp J.(A.

Dearien,

Manager Code Assessment and Applications Program

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q 00C:tn Attacnment:

DUPLICATE DOCUMENT As stated Entire document previously c::

S. D. MacKay, NRC-DOR entered into system under-R. W. xiehn, Em Idahm a

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