ML19254D007
| ML19254D007 | |
| Person / Time | |
|---|---|
| Site: | Kewaunee, Point Beach, Prairie Island  |
| Issue date: | 09/30/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19254C998 | List: |
| References | |
| NUDOCS 7910190279 | |
| Download: ML19254D007 (5) | |
Text
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SAFETY EVALUAT?0N REPORT STEAM GENERATOR WATER HAMMER KEWAUNEE POINT 3EACH UNITS 1 AND 2 PRAIRIE ISLAND UNITS 1 AND 2 '
SEPTEMSER 1979 1190 026 9
7910190
4
1.0 INTRODUCTION
Steam generator water hammer has occurred in certain nuclaar 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 thase events varies from plant to plant. A total loss of feedwater could affect the ability of the plant to cool down after a rea*ctor shutdown; therefore, the NRC is concerned about these events occurring, even thcugh an event wi Lh potentialle 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 representea a safety conce n 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 fee 6<ater 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 five operating power units considered in this safety evaluation include Kewaunee, Point Beach Units 1 and 2, and Prairie Isl.
Units 1 and 2.
These five units have a particular arrangement of main feedwater piping that apparently is not susceptible to steam generator water hammer.
Altnough they have been subjected to system transients that affect the thermal and hydraulic conditions in the feedwater lines and feedwater rings, these units have experienced no steam generator water hammer.
2.0 EVALUATION Our consultant, EG&G, Idaho, Inc. prepared evaluations of steam generator water hammer at Kewaunee, Point Beach 1 and 2 and Prairie Island 1 and 2 as part of our technical assistance program.
Three individuel evaluations (references 4.4.1, 4.4.2 and 4.4.3) were prepared separately for each of the three power stations and the conclusion was reached in each case that the means to reduce the potential for water hammer were inadecuate to maintain sufficiently full feedrings and feedwater piping until feedring recovery occurs.
However, these systems have been subjected to the conditions conducive to water namer and no water hammer nas occurred.
Therefore, the potential for stear, generator water ham er at these three oower stations was reevaluated (reference 4.4.4) based
- n :neir recorc of success #ul 0;:eraticn anc the cartic;lar arrangerent of auxiliary feecwater piping in relation tc main fescvater Dioing that is corrcn te all three ocwer staticns.
The rescits of that integrated 1190 027
. reevaluation showed that since these nuclear powir units had been subjected to thosc-conditions conducive to water hammer t:: e> might be expected during normal operation, transient or accident conditic/.s and no water hammer had occurred, water hammer is not likely to occur at these units in the future.
Our consultant concluded that steam generator water hammer is not likely to occur in these 5 units during normal or transient operating conditions and recommended that instal'ation of top discharge feedrings in the steam generators to avoid steam generator water hammer is not necessary for continued safe operation of Point Beach Units 1 and 2, Prairie Island-Also, our consultant concluded from his Units 1 and 2 and Xewaunee.
integrated reevaluation that, in view of cast coerating experience, the test program recommended in the initial indiviraal evaluations is not We have reviewed the licensees' submittrls and our necess ary.
consultants reports listed under Section 4 of this evaluation.
We~ concur with our consultant's final conclusions and recommendations.
However, even though staam generator water hammer is not likely to occur in these units, these licensees should be vigilant and monitor for water hammers that might impose significant stresses on the piping systems or their supports.
We,ceviously requested in our letter of September 2,1977, that licensees for operating pressurized water reactors report all damaging water hammer events occurring in safety related systers or occurring in other systems that affect safety related systens.
A damaging water hamrer was defined therein as an event that resulted in damage to pipe supports or pipe insulation; pipe cisplacement; or failure of pipes or components.
We will continue to monitor licensee event reports as well as water hammer reports from these licensees for indications of possible water hammer.
If such indications appear in the future, this matter will be reexamined and mey result in additional requirements to reduce the probability of steam generator water hammer at these facilities.
3.0 CONCLUSION
Based on our knowledge of water hammer phenomena and our review of the referenced technical evaluation reports by our consultant, the licensee's responses listed in Section 4 and the particular piping geometry and operating history of these five nuclear pcwer units, we have concluded that steam generator water hammer is not likely to cccur at these units during normal operation or as a result of transient or accident conditions.
We, tnerefore, find that modificaticns to prevent steam generator water hammer are not necessary for the continued safe oper1* ion of the aaaunee, Point eacn Units 1 and 2 and Prairie Island Units 1 end 2 nuclear power s ta ti on s.
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4.0 REFERENCES
ih 9
4.1 Kewaunee 4.1.1 E. W. James, Wisconsin Public Service Corporation (WPSC), letter to R. A. Purple, NRC, Subject
" Response to May 13,1975 NRC letter on Steam Generator Water Hamer", ' August 1,1975.
4.1.2
' E. W. James, WPSC, letter to R. A. Purple, NRC, Subject -
" Transmittal of report entitled, ' Water Hamer Analysis for Feedwater and Steam Generator Syste-s'", dated March 10, 1976.
4.1.3 E. W. James, WPSC, letter to A. Schwencer, NRC, Subject -
" Response to September 2,1977 NRC letter on Steam Generator Water Hammer", February 3,1978.
4.2 Point Beach Units 1 and 2 4.2.1 S. Burstein letter to G. Lear, Subject
" Response to May 15, 1975 NRC letter on Steam Generator Water Ham er," June 19, 1975.
4.2.2 S. Burstein letter to G. Lear, Subject
" Response to September 2, 1977 NRC letter on Steam Generator Water Hammer," November 1,1977.
4.3 Prairie Island Units 1 and 2 4.3.1 L. O. Mayer, Northern States Power Company (NSPC), letter to D. Ziemann, NRC, Subject
" Response to May 12,1975 NRC letter on Steam Generator Water Hammer", September 2,1975.
4.3.2 L. O. Mayer, NSPC Letter to V. Stello, NRC, Subject
" Transmittal of report ef titled ' Analysis of PWR Secondary System Fluid Flow Instability'", January 29, 1976.
4.3.3 L. O. Mayer, NSPC, letter to Director of Nuclear Reactor Regulation, NRC, Subject
" Response to September 2, 1977 NRC letter on Steam Generator Water Ham,er", December 30, 1977.
4.3.4
'W. E. Bennett, Waterhammer in Steam Generator Feedwater Lines, Westinghouse Technical Eulletin, NSD-TB-75-7, June 10,1975.
4.4 Consul ant-EG5G, Idaho. Inc.
4.a.1 J.
Dearien le:
er to R. E. Tiller. JA:-122-79, Point Beach cnits 1 anc 2 Stear Ser. erat:r e.ater
-a-er Tectnical Evaluation (A6257), June 12, 1979.
4.4.2 J. A.
Dearien letter to R. E. Tiller..A -129-79,
Kewaunee Oc,er Station 5:ea Generator '-la er -ar er Technical Evaluation (A6257), June 12, 1979.
1190 um
r a 4.4.3 J. A.
Dearien letter to R. E. Tiller,
JAD-135-79, Prairie Island Power Station Steam Generator Water Hamer Technical Evaluation (A6257), June 27, 1979.
4.4.4 J. A.
Dearien letter to R. E. Tiller,
JAD 162-79 Reevaluation of Steam Generator Water Hamer for Point Besen Units 1 and 2 Prairie Island Units 1 and 2, and Kewaunee, August 6,1979.
I19,0 030
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