ML19290E302
| ML19290E302 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 01/31/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19290E299 | List: |
| References | |
| TASK-05-13, TASK-5-13, TASK-RR NUDOCS 8003100179 | |
| Download: ML19290E302 (5) | |
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Enclosure 9
SAFETY EVALUATION REPORT STEAM GENERATOR WATER HAMMER YANKEE NUCLEAR POWER STATION DOCKET NO, 50-29 JANUARY 1980 O
O 80031001 7s7
1.0 INTRODUCTION
Steam generator water hanmer 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 signifi-cance 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, these 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 during 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 Hammer," NUREG-0291.
The Yankee Rowe plant had experienced steam generator water hammers during its 5 years of operation prior to September 1966.
Modifications to prevent steam generator water hammer or reduce its magnitude were installed during September and October of 1966.
The modifications included the elimination of the horizontal feedwater pipe adjacent to the four steam generators. Since 1966, the feedwater system has been subjected to those conditions that are conducive to steam generator water hammer but none has occurred.
2.0 EVALUATION Our consultant, EG&G Idaho Inc., prepared the attached evaluation of steam generator water hammer at the Yankee Rowe Plant as part of our technical assistance program.
(Letter from J. A.
Dearien,
EG&G, to R.E. Tiller, DOE, dated January 9,1980.) We have reviewed this report together with the licensee's submittals Itsted under item 4.0.
3.0 CONCLUSION
Based on our knowledge of water hammer phenomena, and our review of the licensee's responses and the attached evaluation report, we concur with our consultants' conclusion that the potential for steam generator water hammer is sufficier.tly low to permit continued operati m of this facility. However, even though steam generator water hammer is not likely to occur, the licensee should be vigilart and monitor for water hanners that might impose significant stresses on the piping systems or their supports. We will continue to monitor reports from this licensee for indications of possible water hammer. If such indications appear in the future, this matter will be reexamined and may result in additional requirements to reduce the probability of steam generator water hammer at these "acilities.
We 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 Yankee Nuclear Power Station.
4.0 REFERENCES
4.1 J.L. French, Yankee Atomic Electric Company (YARC), letter to R.A. Purple, NRC, Subject
" Response to May 13, 1975 NRC letter on Steam Generator Water Hammer," July 18, 1975.
4.2 D.E. Moody, YAEC, letter to A. Schwencer NRC, Subject -
" Feed Line Water Hammer," November 2,1977.
4.3 D.E. Moody, YAEC, letter to D.L. Ziemann, NRC, Subject -
" Water Hamer," December 7,1979.
4.4 D.E. Moody YAEC, letter to D.L. Ziemann NRC, Subject -
" Water Hammer," December 21, 1979.
4.5 J.A. Block, et al, An Evaluation of PWR Steam Generator Water Hammer..Creare, Inc., NUREG-0291 (December 1976).
4.6 W.E. Bennett, Waterhammer in Steam Generator Feedwater Lines, Westinghouse Technical Bulletin, NSD-TB-75-7 (June 10,1975).
Attachment ry 64 G ua,na,,,,.
P.O.go,,ggg idaho FeJis. Idaho 83401 January 9, 1980 Mr. R. E. Tiller, Director Reactor Operations and Programs Division Idaho Operations Office - DOE Idaho Falls, ID 83401 YANKEE R0WE POWER STATION STEAM GENERATOR WATER HAMMER TECHNICAL EVALUATION (A6257) - JAD-7-80 Ref:
J. A.
Dearien Ltr to R. E. Tiller,
JAD-225-79, PWR Steam Generator Water Hammer Reviews (A6257),
November 8, 1979
Dear Mr. Tiller:
The attachnent completes the assessment of the effective-ness of the existing means to reduce the potential for steam generator water hammer at the Yankee Rowe Power Station (YRPS).
We have reviewed the operating history of the YRPS pertinent to steam generator water hmaner and the related operational and procedural characteristics of the feedwater system. The review has shown that condi-tions conducive to steam generator water hammer have occurred at the YRPS but no water hammer events have been observed subsequent to the 1966 feedwater system modifications. The conditions have been encountered during normal operating transients and startup and shutdown operations. Such conditions would also be ex-pected 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 generator water hammer is sufficiently low to permit continued operation of this facility.
t
9
,9 R9 E. Tiller January 9, 1980 JAD-7-UD Page 2 This transmittal constitutes completion of the YRPS SER, Task A6257 of the Milestone Chart in the referenced letter.
Very truly yours, 1
w&
J.
Dearien,
Manager Code Assessment and Applications Program DDC:tn
Attachment:
As stated
/.'D. MacKay, NRC-DOR S
cc:t R. W. Kiehn, EG&G Idaho w/o attach.
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STEAM GENERATOR WATER HAM 4ER TECHNICAL EVALUATION YANKEE R0WE POWER STATION January 1980 EG&G Idaho, Inc.
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