ML19294B463
| ML19294B463 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 01/31/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19294B462 | List: |
| References | |
| TASK-05-13, TASK-5-13, TASK-RR NUDOCS 8002280440 | |
| Download: ML19294B463 (3) | |
Text
Enclosure 1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION STEAM GENERATOR WATER HAliMER YANKEE NUCLEAR POWER STATION DOCKET N0. 50-29 JANUARY 1900 8002280 9gg
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 conse unt 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, infomed all PWR licensees that water harter 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 nomal 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.
The Yankee Rowe plant had experienced steam generator water hamers 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 hamer but none has occurred.
2.0 EVALUATION Our consultant, EG&G Idaho Inc., prepared the attached evaluation of steam generator water harrer 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 listed 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 sufficiently low to permit continued operation of this facility. However, even though steam generator water hammer is not likely to occur, the licensee should be vigilant and monitor for water hammers 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 app ~ ear 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 facilities.
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 Hammer," 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).