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NUREG-0918
e
Prevention and Mitigation of'
Steam Generator Water Hammer'
Events in PWR Plants
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U.S. Nuclear RegulatoryCommission,
Office of Nuclear Reactor Regulation
J. T. Han, N. Anderson
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NOTICE
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NUREG-0918
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_
Prevention and Mitigation ofSteam Generator Water Hammer
'
Events in PWR Plants:
_
Manuscript Completed: March 1982Data Published: November 1982
| J. T. Han, N. Anderson
Division of Safety TechnologyOffice of Nuclear Reactor RegulationU.S. Nuclear Regulatory CommissionW:shington, D.C. 20566
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ABSTRACT
Water hammer in nuclear power plants is an unresolved safet'y issue understudy at the NRC (OSI A-1) (Reference 1). One of the identified safetyconcerns is steam generator water hammer (SGWH) in pressurized-waterreactor (PWR) plants (References 2-4). This report presents a summary of:(1) the c1uses of SGWH, (2) various fixes employed to prevent or mitigateSGWH, and (3) the nature and status of modifications that have been made ateach operating PWR plant. The NRC staff considers that the issue of SGWHin top feedring designs has been technically resolved. This report doesnot address technical findings relevant to water hammer in preheat typesteam generators.
.
iii
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CONTENTS
ABSTRACT ............................................................. iii
LIST OF FIGURES ...................................................... V.
I ACKNOWLEDGMENTS ...................................................... Vii
1. INTRODUCTION .................................................... I
i 2. TECHNICAL DISCUSSION ............................................ I
2.1 Definition and Possible Causes of Steam GeneratorWater Hammer .............................................. 2
.
| 2.2 Modifications to Prevent ar.d Mitigate SGWH ................ 7
i'
2.3 Summary ................................................... 104
3. DESCRIPTION OF MODIFICATIONS MADE AT OPERATING PWR'S . . . . . . . . . . . . 12
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j 4. CONCLUSIONS ..................................................... 26;
5. REFERENCES ...................................................... 28
>
FIGURES
h
1. A steam generator (SG and Main Feedwater Line) for atypical Westinghouse plant ...................................... 3
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| 2. A Westinghouse steam generator with the " unmodified"| feedring using bottom holes to discharge water .................. 4
3. A Combustion Engineering steam generstor with the" unmodified" feedring using bottom openings todischarge water ................. 5.................... ..... ...
4. Possible sequential events leading to steam generatorwater hammer ....................................... 6............
i 5. Westinghouse and Combustion Engineering steam generatori feearings using J-tubes to discharge from the top of the
feedring ........................................................ 8
6. Westinghouse-recommended designs to achieve the "short"horizontal feedwater pipe at steam generator inlet . . . . . . . . . . . . . . 9
v
1
1
7. Babccck & Wilcox steam generator with external feedring(header) ........................................................ 11
8. Steam generator feedring and feedwater system at Kewaunee,Prai rie Island 1 and 2, and Point Beach 1 and 2 . . . . . . . . . . . . . . . . . 33
9. Preheat steam generator at McGuire 1 ............................ 21
10. Schematic of the McGuire 1 preheat steam generator withassociated feedwater system ..................................... 22
TABLES
1. A summary of water hammer modifications for feedring SGs ........ 12
2. Summary of SGWH modifications implemented at all W andCE operating plants ............................................. 13
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ACKNOWLEDGEMENTS
The authors are grateful to a number of people for providing valuableinformation and discussion during preparation of this report.
Special thanks are due to S. D. MacKay of NRC, who was responsible for thecompletion of most safety evaluation reports cited in the report.Assistance from other NRC colleagues is also acknowledged; these include0. D. Parr and the staff of the Auxiliary Systems Branch; C. C. Graves;R. Colmar; and project managers and resident inspectors of the operatingPWR plants.
Steam generator information was received from F. C. Wellhofer andJ. Schulties at Westinghouse, and R. E. Daleas and his staff at CombustionEngineering. The authors are grateful to them.
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i
v ii
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1. INTRODUCTION
Water hammer in nuclear power plants is an unresolved safety issue understudy at the NRC (VSI A-1) (Reference 1). One of the identified safety .
concerns is steam generator water hammer (SGWH) in pressurized-waterreactor (PWR) plants (References 2-4). This report presents a summary of:(1) the causes of SGWH, (2) various , fixes employed to prevent or mitigateSGWH, and (3) the nature and status of modifications that have been made ateach operating PWR plant. The NRC staff considers that the issue of SGWHin top feedring designs has been technically resolved.
SGWHs occurred in certan PWR plants before modifications discussed in thisreport were performed. Effects varied from plant to plant, usually rangingfrom noise to observed damage to feedwater piping. The most severerecorded SGWH incident (Reference 5) occured on November 13, 1973 at theIndian Point Unit 2 Plant; the feedwater piping cracked and resulted insteam release into the containment building. However, the plant was shutdown safely and no damage to the reactor or primary system resulted. Sincethen, Westinghouse has conducted several studies to identify causes of SGWHand develop modifications to prevent or mitigate SGWH (References 6-8).
Because of the the continuing occurrence of SGWHs in some Westinghouse (W)and Combustion Engineering (CE) plants, the NRC in September 1977 requestedall W and CE PWR licensees to submit proposed hardware and proceduralmodifications necessary to prevent or mitigate SGWH (Reference 9).Licensee responses were subsequently evaluated by the NRC staff, andconclusions were presented in safety evaluation reports and letters tolicensees. As a result of these evaluations, the NRC staff prepared aBranch Technical Position ASB 10-2, " Design Guidelines for Water Hammers inSteam Generators with Top Feedring Designs" and incorporated this positioninto Section 10.4.7 of NRC's Standard Review Plan (NUREG-0800). SinceBabcock and Wilcox (B&W) plants had not reported damaging SGWH's, theseplants were not required to make changes. However, recently (5/82) someB&W SG's have baen found to have damaged internal auxiliary feedring andsupport strv . ee . These findings are discussed briefly in Section 2.0and 4.0; m ft oa hations are underway.
Chapte if s report addresses the possible causes of water hammer in Wand CE stean perator and feedwater systems, various modifications to helpprevent SGWH, and an explanation of why water hammer is unlikely to occurin B&W steam generators. Chapter 3 presents specific plant modificationsapproved by the NRC staff that have been implemented at each of the38 operating W and CE plants. Chapter 4 presents staff conclusions.
Finally it should be noted that this report does not address the waterhammer issue with respect to preheat steam generator designs, such as: WModels D2/D3 and D4/DS. Water hammer considerations for preheat SG's willbe included in the staffs concluding water hammer technical evaluations forUSI A-1.
2. TECHNICAL DISCUSSION
1
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2.1 Definition and Possible Causes of Steam Generator Water Hammer
Steam generator water hammer (SGWH) is defined as steam condensation-induced water hammer occurring in the secondary side of a PWR steamgenerator (SG) at the connection to tne feedwater line (Reference 2).
Prior to the introduction of preheat SG's,* all PWR steam generatorsemployed a feedring (i.e., ring-type sparger) through which the feedwateris injected into the downcomer between the baffle and the outer shell.Figure 1 shows the SG and main feedwater line of a typical Westinghouseplant. Figure 2 shows the internals of a Westinghouse SG with the" unmodified" feedring with bottom holes to discharge water. It should benoted that when the severe SGWH occurred in 1973 the SG feedring at IndianPoint 2 was similar to the one shown in Figure 2(b) except that the mainfeedwater pipe was 18-in. Schedule 80 pipe. Figure 3 shows a CombustionEngineering SG with the " unmodified" feedring using bottom openings todischarge water.
During certain plant transients, which result in a rapid reduction offeedwater flow, the SG water level may drop below the bottom of thefeedring sparger. A bottom discharge feedring can be drained of water andfilled with steam within 1 or 2 minutes after the feedring is uncovered iffeedwater flow has been terminated (Figures 2 and 3). When the feedwaterflow is resumed following such a transient (which is usually highlysubcooled auxiliary feedwater) it enters the horizontal pipe run into thefeedring, and flows under the steam blanket as depicted in Figure 4(a).Rapid steam condensation can occur at the interface between the steam andthe subcooled feedwater causing a countercurrent of steam to flow over thetop of the feedwater. Interaction forces between the steam and water cancreate enough turbelence to seal off a pocket of steam, as depicted inFigure 4(b). Continued rapid condensation of steam in the pocketaccelerates a slug of water into the void as depicted in Figure 4(c).
Acceleration forces on the water slug can be very large because thepressure on one side is at steam generator pressure, initially in excess of1000 psi, while the pressure on the trapped vapor side can be greatlyreduced depending on condensation rate. As a result the water slug canhave a high velocity when it impacts against the incoming water column, anda pressure pulse is produced [ Figure 4(d)]. This constitutes one possible
explanation of a steam generator water hammer. The magnitude of thepressure pulse and its propagation through the feedwater line depend onmany factors. These include the steam void condensation rate, the initialvolumes of the void and water slug, steam pressure in the SC, sonicvelocity in the feedwater line, and piping geometry and layout(References 10, 11). In a severe SGWH the pressure pulse may be as high asthousands of psi (References 2,4).
As the pressure wave travels upstream in the feedwater line [ Figure 4(d)],dynamic forces are produced on the pipir.. system which can cause damage to
The McGuire Unit Plant which uses feedwater injection nozzles at the*
bottom of the SG instead of a feedring is discussed in Chapter 3.
2
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Feedwatermanifold
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U tubes
Containmentwall I
J\ Primary
coolantflowi
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Figure 1. A steam generator (SG and main feedwater line)for a typical Westinghouse Plant,
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(16 in., sch 80 pipe)= Upper shell Thermal sleeve
p (16 in., sch 80 pipe)#
)' ' < N', ' ' , StG wall (to 6n., sch 40 pipe)Feed ring
Feedwater ring ,7 / / ~ 7[['d
Antivibration bars-
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. Internal clearance_= Tube support plates cap = 0.020 2 0.015 6n.
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Lower shell - M tee
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CIhEL 21083
Tube sheet ?
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Primary manway Blowdown linei
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2a. Typical Westinghouse feedring steam generator 2b. Sketch of " unmodified" Westinghouse feedring
Figure 2. A Westinghouse steam generator with the " unmodified" feedring using bottom holes to discharge water
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3a. Typical CE steam generator 3b. Sketch of CE " unmodified" feedring assembly
Figure 3. A Combustion Engineering steam generator with the " unmodified" feedring using bottom openings todischarge water
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Steam fromvents in some systems Water slug
Steam moves rapidlygenerator nozzleinto void
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(d) Possible Water Slug impact INEL 21076
Figure 4. Possible sequential events leading to steam generatorwater hammer
6
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piping supports.and restraints (e.g., snubbers, and clamps) and to thepiping. Both types of damage were evident in the severe SGWH incident in1973 at Indian Point 2, where radial deformation or bulging of somefeedwater piping was found (Reference 5). A half-circle steam-leaking' fracture occurred in the main feedwater piping at the containment wallanchor point, which was probably caused by the excess bending stress due topressure-wave-induced dynamic forces (Reference 12).
,
2.2 Modifications to Prevent and Mitigate SGWH
The most effective method for preventing SGWH is to keep th. SG feedringand the feedwater line full of water so that steam will not enter thefeedwater system. This is the case normally during plant operation.However, during certain plant transients the SG water level may fall belowthe feedring. In a feedring designed with bottom discharge holes (as shownin Figures 2 and 3), it will be drained in a few minutes. To prevent rapiddraining, multiple J-tubes are installed on top of.the feedring and thebottom-discharge holes are plugged by welding, as shown in Figure 5. Withthis modification, the rate of water discharge from an uncovered feedringis greatly reduced * and it will take about 20 minutes or more to drain a SGfeedring with top-discharge J-tubes as compared to roughly one to twominutes for a SG feedring with bottom-discharge holes. The installation ofJ-tubes and closure of the bottom holes on the feedring is the firstmodification most frequently made to prevent and mitigate SGWH.
It should be emphasized that the installation of J-tubes will significantlyslow down but generally not stop the feedring from losing water whenuncovered. This modification is effective only if feedwater flow can be
j reestablished before a significant amount of steam enters the feedring.i The second modification is therefore to provide early feedwater (usually
auxiliary feedwater) flow into the SG and thus to supply water to thefeedring as soon as practical.
For W and CE plants, the highest elevation of the feedwater line isgenerally at the SG feedring and the connecting horizontal feedwater pipeat the SG inlet (Figure 1). Draining of this part of the feedwater line
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can occur during those plant transients in which SG water . level falls belowthe feedring. By shortening the length of the horizontal pipe at the SG
| feedwater inlet, the volume that can be drained in the feedwater line isreduced; consequently, the magnitude of the pressure pulse of acondensation-induced SGWH will also be reduced. The third modification isto shorten the horizontal feedwater pipe leading to the SG inlet nozzle byinstalling an elbow or U-bend as shown in Figure 6 (References 2,3,7). A
i
There is a thermal sleeve between the SG inlet nozzle and the feedring*
piping. For many operating SGs, water from the feedring piping canleak through the sleeve into the SG. The important point is that thecombined leakage through the thermal sleeve, the closed feedwatervalve and evaporation loss is much less than that going through thebottom-discharge holes of the unmodified SG feedring. The leak ratethrough the thermal sleeve has been estimated to be on the order of10 gpm.
7
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Sa. Westinghouse J tube feedring configuration atIndian Point 2
Figure 5. Westinghouse and Combustion Engineering steam generator feedrings using J tubes to discharge fromthe top of the feedring
- _ _ -
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not to exceed 8 feetINEL 21078
Figure 6. Westinghouse recomended designs to achieve the "short"horizontal feedwater pipe at a steam generator inlet
9
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90 -downward elbow at the SG inlet [ Figure 6(a)] minimizes the length of ;
the horizontal pipe and is therefore the preferred design of those shown in'
-
Figure 6. A U-bend at the SG inlet [ Figure 6(b)] serves the same purposeas an elbow except that the flow resistance is higher in the U-bend thanthe elbow. An inverted U-bend [ Figure 6(c)] has a longer-drained lengththan the elbow or U-bend because both the top and the left leg of theinverted U-bend can be drained. The maximum length specified for drainablefeedwater line is 8 ft for designs shown in Figure 6. This criterion wasrecommended by Westinghouse (Reference 7).
In an effort to reduce SGWH frequency, some licensees impose a maximumlimit on feedwater flowrate when feedwater flow is initiated. The maximumhas been spec;fied at around 150 gpm per SG. [This value is 50 gpm lessthan the 200 gpm upper limit experimentally determined in the SGWH tests atthe Indian Point Unit 2 Plant (Reference 2).] At a low feedwater flowratethe water velocity and at a water level in the pipe being low enough topreclude trapping a steam void (Figure 4) condensation-induced SGWH isunlikely to occur. However, it may be undesirable in some plant transientsto limit the feedwater flowrate to 150 gpm per SG, and therefore thismodification is not commonly used.
In addition, other measures and proceedures are possible. For example,near-s.turated water (instead of highly subcooled water) can be used torefill a drained SG feedring minimizing the rate of condensation.Furthermore, some nuclear plants (e.g., Kewaunee and Palisades) have uniquefeatures or modifications to prevent damaging SGWHs. These are discussedin Chapter 3, where a discussion of each plant is presented.
The Babcock & Wilcox steam generator design is a single pass heatexchanger, termed a Once Through Steam Generator (OTSG), which employs avertical tube bundle that passes through a pool of secondary coolant asshown in Figure 7. The B&W OTSG is designed to minimize, or eliminatewater hammer since: (a) separate feedwater and auxiliary feedwater headers(located external to the steam generator shell) are employed; these risersfrom the external feedwater header which function like J-tubes with respectto keeping the header full of water, (b) auxiliary feedwater injectiondirectly on SG tubes rather than into feedwater headers, (c) modulatedfeedwater control using cascaded flow control valves. These designfeatures appear to be effective since damaging SGWH's have not beenreported by B&W plants.
However, some B&W OTSG's employ an internally located auxiliary feedwaterring (eg. Davis-Besse, Rancho Seco and Oconee No. 3); this design differsfrom that shown in Figure 7. Recent (5/82) plant inservice inspections(Reference 13) have discovered damaged internal auxiliary feedring andsupport structures. The damage appears relatable to steam pocket collapseand is under evaluation by B&W and the NRR staff.
2.3 Summary
Table 1 summarizes the modifications that help prevent and mitigate SGWHs.For most operating PWR plants, a combination (i.e., simultaneous
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Table 1 A Summary of Water Hammer Modifications for Feedring SGs
No. Modification Type Function
,
1 Top discharge J-tubes on feedring Hardware Significant delay infeedring draining
2. Early feedwater flow into the SG Procedure Help keep feedringfull of water
3 Short horizontal feedwater pipe Hardware Reduce magnitude of
(less than 8 feet) at SG inlet SGWH
4 Limited flow to recover feedring Procedure Prevent forming of(150 gpm per SG) & hardware water slug to trap
steam void
5 Others (plant specific) HardwareOrprocedure
employment) of the first three modifications has proved to be effective inpreventing SGWHs. Other modifications have been made in some plants asdiscussed in Chapter 3.
In 1975 guidance for the review of designs fur prevention and mitigation ofSGWd in application for construction permits and operating licenses wasincorporated into Section 10.4.7 of the Standard Review Plan, Condensateand Feedwater Systems which includes as an attachment Branch TechnicalPosition 10-2, Design Guidelines for Water Hammers in Steam Generators withTop Feedring Designs. For plants with preheater-type steam generators,license reviews are conducted using NUREG/CR-1606, An Evaluation ofCondensation Induced Water Hammer in Pre-Heat Steam Generators, as guidance.
3. DESCRIPTION OF MODIFICATIONS MADE AT OPERATING PWR's
In September 1977, the NRC requested all W and CE PWR licensees to submitproposed hardware and procedural modifications necessary to prevent ormitigate SGWH (Reference 9). The modifications proposed by each licenseewere evaluated on an individual plant basis. The effectiveness of thesemodifications had to be demonstrateo either by tests run at the plant or bytests conducted in a similar plant. For some of the plants which havenever had SGWHs, additional modification or backfitting was not required.
The modifications made on each W and CE operating plant are discussed below(plants are listed in alphabetical order). Table 2 presents a summary ofthe SGWH modifications implemented at 38 operating plants. Most of theplants have employed a combination of J-tubes on the feedring for topdischarge, early feedwater flow into SG, and short horizontal feedwaterpipe (less than 8 ft) at the SG inlet.
12
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Table 2 Simmisry of $331 modificattens taplausated et all u and C2 eperettel plants'
* $nertIsrly nortrental Lietted
& Tubes fecemeter Feeemeter Flam toen Flew Pipe et Recover Other Test
' herettne Plants feedrina into 56 $$ inlet feedetas ($ee Romerts) Caneucted teferences teerts
1. Artansas 2 a a a a 13.14
2. Seaver falley 1 a a a 16
' 3. Calvert Citffs 1 a a a a 17.18 Separate austilary feedring
4 Calvert Citffs 2 a a s - a 17.18 Same 'as Unit 1
, 5. Coot 1 a a s a 20.22I
; 6. Cook 2 m a a e a 20.22+
7. Farley 1 a a a a 23
i 8. Farley 2 a a a 23
9. Ft. Clahaue a a a 24 Separate auslitary feedseter injectlee assale
10. Glaae a a s a 25
11. nedsas neck s a 26 $1ow change of feedmater fleurete
12. ladian Point 2 s a a a a 27
13. Indian Potet 3 a s a 28
! 14. towaunee e a 29 Prostatte of auntliary feedseter tajectlenpotat free M
15. ustne tankee a 30
14. ncGetre 1 a a a 31.32.33 u preheat $$ estng lejeCtlen neffles,
E 17. altistone Point 2 a a a a 33,34
18. North Anna 1 a a a a 35,37
19. sorth Anna 2 a a a a 35.37.
20. Paltsades* a a 38.39 $aearate avstltary feeduster Itne. tests yetto es conducted
21. Potet Seach I a a a a 40 See Rewaunee,
22. Point Seecg 2 s a a 40 See tewaunee
23. Pratete Island I a a a a 41 See Newaunee
24. Pratrie Island 2 e a a 41 See towaunee
25. Robinson 2 a a 42 400 gym per $G for stese itae bream
26. St. Lucie 1 a a e 43,44
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37. Iten 1* a a a a s 57 One $6 feedelag is yet to have atubeslastalled
38. Iton 2 s a a a 57
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For simplicity, " Arkansas 2" stands for the Arkansas Unit No. 2 Plant.This notation is used for the rest of this chapter.
(1) Arkansas 2 (CE plant w/2 SGs)ImplementationArkansas 2 has implemented (a) J-tubes on SG feedrings, (b) earlyinitiation (within one minute) of auxiliary feedwater flow into the SG, and(c) short horizontal feedwater pipe at SG inlet (References 14,15). A testwas performed (as part of the plant startup test program) to demonstratethat damaging SGWH did not occur and that auxiliary feedwater flow didstart automatically within the time specified.
StatusThe staff has approved the present implementation at Arkansas 2(Reference 14).
(2) Beaver Valley 1 (W plant w/3 SGs)ImplementationBeaver Valley 1 has implemented all of the first three modifications aslisted in Table 1: (a) J-tubes on SG feedrings, (b) early initiation(within one minute) of auxiliary feedwater flow into the SG, and (c) shortfeedwater pipe at SG inlet (Reference 16). [A flow limitation of about150 gpm to recover a SG feedring was first imposed (Reference 16) but laterit was removed (Reference 16).] No SGWH test was required because the testsperformed at the Trojan plant (W plant with the same type of SGs) weredeemed to be applicable to the Beaver Valley Unit 1 plant; SGWH did notoccur in Trojan tests, which is discussed below.
StatusThe staff has approved the present |mplementation at Beaver Valley 1(References 16).
(3) Calvert Cliffs 1 (CE w/2SGs)
(4) Calvert Cliffs 2 (same as Unit 1)ImplementationCalvert Cliffs Unit 1 and Unit 2 are identical CE plants. Both plants have
g installed J-tubes on SG main feedwater feedring, but they do not have ashort horizontal pipe (the horizontal length of the main feedwater lineupstream of the main feedring is about 12 ft) (References 17,18). However,a unique feature is employed in their SGs-there is a separate auxiliaryfeedring to inject cold auxiliary feedwater into the SG. There is noconnecting path between the auxiliary and main feedwater lines, and theauxiliary feedwater is supplied into the SGs through the separate auxiliaryfeedring. As a result, cold auxiliary feedwater cannot enter the main
feedring.
Each SG is supplied with main feedwater through the main feedring until themain feedwater flow is decreased (for any reasons) to less than 750 gpm perSG (5% of full feedwater flow) and concurrently the SG water level fallsbelow the main feedring; under this condition the main feedwater flow isstopped and auxiliary feedwater is supplied to the SG through the auxiliaryfeedring. During the uncovery period, the main feedring drainage rate due
14
_ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ - _ _
-to the leakage through its thermal sleeve (see Figure 2) is estimated inthe order of 10 to 20 gpm; (References 17,18) a supply of main feedwater at750 gpm or more will keep the main feedring full of water. Therefore,SGWHs during main feedring uncovery will not occur as long as mainfeedwater flow is supplied at 750 pgm per SG or higher.
The auxiliary feedring does not heve J-tubes but holes for bottomdischarge. Since November 1976 auxiliary feedwater flow has been suppliedto the auxiliary feedring several times a year but no water hammer hasresulted (References 17,18,19). The reasons are:
(1) The horizontal portion of the auxiliary feedwater line upstream of theauxiliary feedring is very short (less than a foot).
(2) Auxiliary feedwater is normally supplied at 9 ft/sec which is highenough to keep the 4-in. diameter auxiliary feedwater line andfeedring filled with water so that entrapment of a steam void isunlikely in the pipe.
(3) The auxiliary feedring is located about 43 in, below the main feedringand is less likely to be uncovered.
StatusThe staff has approved the present implementation at Calvert Cliffs 1 and 2(References 17,18).
(5) Cook 1 (W plant w/4 SGs)
(6) Cook 2 (same as Cook 1)ImplementationBoth Cook 1 and Cook 2 have implemented the first four modifications listedin Table 1:
(a) J-tubes on SG feedring,
(b) Early auxiliary feedwater flow into the SG (within about one minuteafter isolation of main feedwater supply),
(c) Short horizontal feedwater pipe upstream of the feedring, and
(d) Feedwater flow limited by administrative control to 150 gpm per SGduring feedring recovery (References 20,21). Tests were performed inCook 2 to demonstrate that no SGWH will occur (Reference 22).
StatusThe staff has approved the implementation at Cook 1 and 2(References 20,22).
(7) Farley 1 (W plant w/3 SGs)
15
-. _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ - _ _ - _ _
(8) Farley 2 (same as Farley 1)Implementation lBoth Farley 1 and Farley 2 have implemented (a) J-tubes on SG feedrings, i
(b) early auxiliary feedwater flow into the SG, and (c) short hurizontalfeedwater pipe leading to the feedring (Reference 23). Tests wereperformed in Farley 1 to demonstrate that no SGWH occurred. Because Farley2 has a similar plant design to Farley 1, no tests were required forFarley 2.
StatusThe staff has approved the present implementation at Farley 1 and 2(Reference 23).
(9) Fort Calhoun (CE plant w/2 SGs)ImplementationFort Calhoun has implemented (a) short horizontal feedwater pipe leading toSG feedring and, (b) early auxiliary feedwater flow into SG (within oneminute) after a loss of main feedwater supply (Reference 24). However, theSG feedring still has bottom-discharge holes instead of J-tubes. Aseparate injection nozzle (4-in. diameter and located above the feedring)is used to inject cold auxiliary feedwater into the SG when the mainfeedwater line is isolated; therefore, the cold auxiliary water will notenter a steam-voided feedring during SG refilling. No SGWHs have occurredat Fort Calhoun, which has been in operation since 1974.
StatusThe staff has approved the present implementation at Fort Calhoun(Reference 24).
(10) Ginna (W plant w/2 SGs)ImplementationGinna has implemented the first four modifications as listed inTable 1: (a) J-tubes on the SG feedring, (b) early auxiliary feedwaterflow into the SG (within a few minutes), (c) short horizontal feedwaterpipe at SG inlet nozzle, and (d) a maximum feedwater rate of 150 gpm per SGduring periods of SG feedring recovery (Reference 25). Because Ginna hasimplemented all the four modifications, no SGWH tests were required.
StatusThe staff has approved the present implementation at Ginna (Reference 25).
(11) Haddam Neck (W plant w/4 SGs)ImplementationHaddam Neck has very short horizontal feedwater pipe (using an elbow) atthe SG inlet (Reference 26). However, SGs do not have J-tubes for top-
discharge. Auxiliary feedwater initiation and control are performedmanually (no automatic initiation of auxiliary feedwater flow), and theplant operator s administrative 1y required to change " slowly" thefeedwater flow rate. For example, during plant startup the main feedwaterpump is started prior to shutdown of the auxiliary feed pump; and during '*-
the plant shutdown the auxiliary feed pump is started prior to shutdown ofthe main feed pump. Administrative procedures also require starting up a
16
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feed pump with the downstream discharge valve closed and that the valve beopened slowly. Nc SGWHs have occurred in Haddam Neck since 1975(References 19,26).
StatusThe staff has accepted the present implementation at Haddam Neck; however,staff acceptance specified that the issue be reexamined if SGWHs occur inthe future (Reference 26).
(12) Indian Point 2 (W plant w/4 SGs)Introduction '
When the severe SGWH occurred in the No. 2 SG at Indian Point 2 onNovember 13, 1973 (Reference 5), the SG did not have any of themodifications listed in Table 1. [All SGs had an " unmodified" feedringusing bottom holes for discharge (Figure 2.); the length of the horizontalfeedwater pipe on the No. 2 SG was about 17 ft.]
ImplementationIndian Point 2 has implemented the first three modifications and partiallyimplemented the fourth (Table 1): (a) J-tubes on SG feedrings, (b) earlyfeedwater flow into the SG (auxiliary feedwater flow will startautomatically in less than a minute during plant transients), (c) shorthorizontal fedwater pipe immediately outside the SG, and (d) auxiliaryfeedwater flow is limited to 150 gpm per SG after any five-minute periodduring which feedwater flow has not been supplied to a SG (Reference 27).
Tests were performed to show that the fixes are effective in preventingSGWHs at the plant (Reference 27).
StatusThe staff has approved the present implementation at Indian Point 2(Reference 27).
(13) Indian Point 3 (W plant w/4 SGs)ImplementationIndian Point 3 nas implemented: (a) J-tubes on the SG feedrings, (b) earlyinjection of feedwater flow into the SG (within a few minutes), and(c) short horizontal feedwr.ter pipe upstream of the feedring(Reference 28). Because the plant design of the SG and feedwater system atIndian Point 3 is similar to that at Indian Point 2, SGWH tests were notrequired.
StatusThe staff has approved the present implementation at Indian Point 3(Reference 28).
(14) Kewaunee (W plant w/2 SGs)IntroductionKewaunee in one of five Westinghouse 2-loop plants which have similardesigns for the SG and feedwater system. The statements made here forKewaunee are also applicable for the other four plants namely Point BeachUnits 1 and 2, and Prairie Island Units 1 and 2.
17
. . ._ __ - _ -. . _ _ - _ _ - . _ - - . -_
.
ImplementationKewaunee, Point Beach 1 and 2, and Prairie Island I and 2 were among thosefor which no backfitting or modifications were required to prevent SGWH(Reference 29). These five plants have not had a single SGWH since tneiroperation started in the early 1970's. However, all these plants will havethe " unmodified" SG feedrings using bottom holes to discharge water (seeFigure 2); the horizontal feedwater pipe at the SG inlet at Kawaunee and atPrairie Island 2 exceeds the 8-ft limit for a SG. Although the auxiliaryfeedwater flow starts automatically shortly after a reactor trip in whichthe feedring is uncovered, this rate of flow cannot maintain the feedringfull of water at the maximum flow rate of the auxiliary feedwater, which isabout 360 gpm per SG.
These plants have a unique piping layout which may be effective inpreventing SGWHs (Reference 29). In these five plants, the 3-in. diameterauxiliary feedwater pipe injects into the 16-in. main feedwater pipe at alocation "very close" to the SG inlet nozzle (Figure 8). The distancebetween the junction of the auxiliary and main feedwater pipes and the SGinlet is approximately 4 ft at Kewaunee and Prairie Island 1, 3 ft at PointBeach 1 and 2, and 7 ft at Prairie Island 2. The value given is for the SGwith the maximum distance. At the junction the auxiliary feedwater isinjected at the horizontal centerline of the main feedwater pipe and normalto the main feedwater pipe. As the 3-in. jet from the auxiliary feedwaterpipe splashes into the much larger 16-in. main feedwater pipe, condensationcan occur if the pipe is voided. But because the travel distance into theSG feedring is so short, the sequential events that lead to SGWH (shown inFigure 4) are not likely to occur. SGWHs have not occurred in over 60 SGyears of operation (ten SGs operated at an average of six years). PointBeach 1 and 2 have administrative controls which require the operator tolimit feedwater flow to 100 gpm per SG during feedring recovery, andPrairie Island 1 and 2 have set the limit to less than 150 gpm per SGduring feedring recovery. However, Kewaunee has no flow limit to recoverthe SG feedring.
StatusThe staff has accepted the present implementation at Kewaunee. However,the staff has stipulated that the matter will be reexamined if SGWHs occur
| in the future (Reference 29).1
(15) Maine Yankee (CE w/3 SGs)ImplementationMaine Yankee has not had any SGWHs since its operation started in 1972,
I therefore, plant modifications to prevent IGWHs were not required! (Refe ence 30). The plant has very short norizontal feedwater pipe (about! 3 ft long) upstream of the SG inlet; however, it still uses the unmodified
SG feedring with bottom discharge (Reference 30).
StatusThe staff has accepted the present implementation at Maine Yankee.However, the staff has stipulated that the matter will be reexamined if
SGWHs occur in the future (Reference 30).
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(16) McGuire 1 (W plant w/4 preheat SGs)Background InformationMcGuire 1 is the first operating plant which uses Westinghouse preheat typesteam generators. These SGs do not use a feedring but have two injectionnonles for feedwater injection (References 3,4). For this type of SG(including future CE economizer SGs), a NRC contractor report was publishedthat evaluates the potential for SGWHs (Reference 31).
Figure 9 shows a preheat SG at McGuire 1 (Reference 31). Main feedwater isinjected into the SG through the lower main feedwater nozzle which is16-in. in diameter, and the auxiliary feedwater is injected into the SGthrough the upper auxiliary feedwater nozzle, which is 6-in. in diameter.During plant startup, when power is below about 25% of full power,feedwater is fed into the SG through the upper nozzle; as power isincreased beyond 25% of full power, the MAIN / AUX valve between the main andauxiliary feedwater lines (shown in Figure 10) is then closed and the mainfeedwater valve is opened so that the SG injection is through the mainfeedwater nozzle. During plant shutdown, as power is reduced below 25% offull power, the main feedwater valve is closed and the MAIN / AUX valveopened so that SG injection is switched from the main feedwater nozzle tothe auxiliary feedwater nozzle.
SGWH FixesBoth the main and auxiliary feedwater lines have an elbow immediatelyoutside the SG (Figure 10) to minimize the length of the horizontal pipe asrecommended in Table 1. Furthermore, the cold auxiliary feedwater isinjected into the SG downcomer (i.e., the annular space next to the SGshell) so that only the main feedwater at elevated temperature is allowedto contact the tubes and flow baffles inside the SG. A test was performedat McGuire 1 to show that damaging SGWHs did not occur. [However, the testreport has not been published as of publication date of this report(Reference 32).]
St tusThe staff has approved the present implementation at McGuire 1(Reference 33).
(17) Millstone 2 (CE plant w/2 SGs)ImplementationMillstone 2 has implemented: (a) J-tubes on the SG feedring, (b) earlyinjection of feedwater flow into the SG (within five minutes), and(c) short horizontal feedwater pipe at SG inlet (Reference 34). Planttests were performed to show that no SGWH occurred.
StatusThe staff has approved the present implementation at Millstone 2(Reference 34).
(18) North Anna 1 (W plant w/3 SGs)(19) North Anna 2 (same as Unit 1)ImplementationNorth Anna 1 and 2 have implemented (a) J-tubes on the SG feedring for topdischarge, (b) early feedwater flow into the SG, and (c) short horizontalfeedwater pipe at SG inlet (References 35-37).
19
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_.
____ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ - _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ - _ - _ _ _ _ _ _ _ _ _ _ _ _ - _ - _ _ _ _ _ _ _ _ _ _ _ _ _ - _
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,
3-in. dia auxiliaryfeedwater line
Thermal sleeve
Steam generator.. wall
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J
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Figure 8. Steam generator feedring and feedwater system atKewaunee, Prairie Island 1 and 2, and Point Beach 1 and 2
20
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/ \. 7*
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21
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Figure 10. Schematic of the McGuire 1 preheat steam generatorwith associated feedwater system
22
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Tests were performed :t both Units 1 and 2 to show that SGWHs did not occurwhile the auxiliary feedwater was fed into the SG following the plantoperating procedures to recover the feedring (References 35-37). (Resultsfor Unit 2 tests were not published.)
StatusThe staff has approved the present implementation at North Anna Units 1and 2 (References 35-37).
(20) Palisades (CE plant w/2 SGs)ImplementationPalisades uses the bottom-discharge feedring (with no J-tubes) to injectmain feedwater into the SG; the horizontal pipe of the main feedwater lineleading to the SG is 28 ft long (Reference 38). However, the plant hasimposed a limited flowrate of 150 gpm per SG during feedring recovery.
- The auxiliary feedwater line has been modified so that it does not injectinto the main feedwater line (Reference 39). The auxiliary feedwater linehas a short horitontal pipe leading to the SG inlet and uses an auxiliaryfeedring with top-discharge J-tubes for auxiliary feedwater injection(Reference 39).
Tests are scheduled to show that SGWH does not occur. Normal plantoperating procedures will be used during the test.
. . Status (as of November 1981)Modification of the auxiliary feedwater line at Palisades has beencompleted. The staff's approval of the implementation at Palisades was
- contingent on successful SGWH tests (Reference 39). These tests weresuccessfully conducted in December 1981.
- (21) Point Beach 1 (W plant w/2 SGs)(22) Point Beach 2 (same as Unit 1)ImplementationPoint Beach 1 and 2 are similar to Kewaunee (Reference 40). See Item 14above for implementation.
. -Status
.The staff has accepted the present implementation at Point Beach 1 and 2.However, this matter will be reexamined if any SGWHs occur at these plantsin the future (Reference 40).
(23) Prairie Island 1 (W plant w/2 SGs). (24) Prairie Island 2 (same as Unit 1)
ImplementationPrairie Island 1 and 2 are similar in design to Kewaunee (Reference 41).
' Please see Item 14 above for implementation.
_ StatusThe staff has accepted the present implementation at Prairie Island 1and 2. However, this matter will be reexamined if any SGWHs occur at theseplants in the future (Reference 41).
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(25) Robinson 2 (W plant w/3 SGs)ImplementationRobinson 2 has short horizontal feedwater pipe (less than 3.5 ft) leadingto the SG inlet (Reference 42). The SGs still have an unmodified feedringwith bottom holes (Figure 12); further, there is no flow limitation forrecovering a SG feedring except in the case of a steam line break for whicha limit of 400 gpm per SG is imposed. Robinson 2 has not had any SGWHs inits ten years of plant operation.
StatusThe staff has accepted the present implementation at Robinson 2. However,this matter will be reexamined if any SGWHs occur at the plant in thefuture (Reference 42).
(26) Saint Lucie.1 (CE plant w/2 SGs)ImplementationSt. Lucie 1 has implemented (a) J-tubes on the SG feedring for topdischarge, (b) early feedwater injection into the SG, ano (c) .shorthorizontal feedwater pipe leading to SG inlet (Reference 43).
Two plant tests were conducted to show that SGWHs do not occur as auxiliaryfeedwater is supplied to a drained SG feedring at 300 gpm and also at600 gpm with a SG pressure of about 900 psig (Reference 44).
StatusThe staff has approved the implementation at St. Lucie 1 (References 43,44).
(27) Salem 1 (W plant w/4 SGs)(28) Salem 2 (similar to Unit 1)ImplementationSalem 1 and 2 have implemented: (a) J-tubes on SG feedring for topdischarge, (b) early feedwater flow into the SG (in about one minute),(c) short horizontal feedwater pipe leading to SG inlet(References 45,46). In addition, Salem I has an administrative control onfeedwater flowrate of about 150 gpm per SG to recover the feedring.
No tests were required at Salem 1 because it ha; incorporated the firstfour modifications recommended in Table 1. A test was conducted at Salem 2according to plant operating procedures to show that SGWH did not occur(Reference 47).
StatusThe staff has approved the existing implementation at Salem 1 and 2(References 45-47).
(29) San Onofre 1 (W plant w/3 SGs)ImplementationSan Onofre I has short horizontal feedwater pipe (less than 3 ft) leadingto the SG inlet (Reference 48). SGs still use the " unmodified" feedring
~
with bottom-discharge holes. The auxiliary feedwater flow at the plant canonly be started manually, this allows the plant operator to feed the SGswith heated main feedwater whenever possible.
(
24
.- . .. --_
_ _ _ _ _ __
.
StatusThe staff has accepted the present implementation at San Onofre 1.However, this matter will be reexamined if any SGWHs occur at the plant inthe future (Reference 48).
(30) Sequoyah 1 (W plcnt w/4 SGs)ImplementationSequoyah I has implemented: (a) J-tubes on SG feedring for top discharge,(b) early feedwater flow into the SG, and (c) short horizontal feedwaterpipe leading to the SG inlet (References 49-51). Plant tests wereperformed to show that no SGWHs occurred (Reference 50).
StatusThe staff has approved the present implementation at Set uoyah 1(References 49-51).
(31) Surry 1 (W plant w/3 SGs)(32) Surry 2 (same as Unit 1)ImplementationSurry 1 and 2 have implemented: (a) J-tubes on SG feedring, (b) earlyfeedwater flow into the SG (in about one minute), and (c) short feedwaterpipe leading to the inlet (Reference 52).
Surry 1 had a damaging SGWH before the modifications discussed above wereimplemented; (Reference 52) the 14-in feedwater line for SG A wasdisplaced about 7 to 10 in., and all seven shock suppressors on the linefailed. No SGWHs have occurred since modifications were made.
StatusThe staff has approved the implementation of SGWH modifications at bothSurry 1 and 2 (Reference 52).
(33) Trojan (W plant w/4 SGs)ImplementationTrojan has implemented: (a) J-tubes in SG feedring, (b) early feedwaterflow into the SG (in about 1 to 2 minutes), and (c) short horizontalfeedwater pipe leading to SG inlet (Reference 53).
Plant tests were performed with auxiliary feedwater supplied at flowratesranging from 120 gpm to 440 gpm (maximum auxiliary feedwater flowrate) intoa drained or partially drained SG feedring (with J-tubes and shorthorizontal feedwater pipe upstream). No SGWHs were ovserved in the testsin which the SG's steam pressure was varied from 400 to 1100 psig and thefeedring draining time varied from 1 to 120 minutes (References 53,54).
StatusThe staff has approved implementation of SGWH modifications at Trojan(References 53,54).
25
(34) Turkey Point 3 (W plant w/3 SGs)(35) Turkey Point 4 (same.as Unit 1)ImplementationTurkey Point Units 3 and'4 have short horizontal feedwater pipe (less than8 ft) leading to SG inlet (Reference 55). SGs still have unmodifiedfeedrings with bottom-discharge holes. No SGWHs have occurred since 1974when the horizontal feedwater pipe leading to the SG inlet was shortened toless than 8 ft for all SGs. (Prior to the pipe modifications, three waterhammer events had occurred which caused deformation of some feedwater linesupports and one elbow.)
StatusThe staff has accepted the present implementation at Turkey Point 3 and 4.However, this matter will be reexamined if any SGWHs occur in the future(Reference 55).
(36) Yankee-Rowe (W plant w/4 SGs)ImplementationYankee-Rowe has implemented short horizontal feedwater pipe at each SGinlet (Reference 56). In addition, a steam line was installed so thatsteam from plant auxiliary boilers can be used to preheat main feedwaterduring startup, shutdown, and other low power operations when the normalsteam supply from SGs is insuf ficient or unavailable to preheat feedwater.The purpose is to reduce the magnitude and likelihood of any SGWHs.
Since the implementation of these modifications in 1966, Yankee-Rowe hasnot had any SWGHs. SGs still use unmodified feedring with bottom-dischargeholes.
StatusThe staff has accepted the implementation at Yankee-Rowe. However, thismatter will be reexamined if any SGWHs occur in the future (Reference 56).
(37) Zion 1 (W plant w/4 SGs)(38) Zion 2 (same as Unit 1)ImplementationZion 1 and 2 have implemented: (a) J-tubes on the feedring of seven out ofeight SGs (as of November 1981, one SG in Unit 1 does not have J-tubes),(b) early feedwater flow into the SG, (c) short horizontal feedwater pipeleading to each SG, and (d) a flow limit at 150 gpm per SG at reinitiationof feedwater flow (Reference 57).
StatusZion 1 is committed to have J-tubes installed on the last SG feedring whichstill has bottom-discharge holes; the work was completed in February 1982.The staff has approved the implementation at Zion 1 and 2 (Reference 57).
4. CONCLUSIONS .
The NRC staff has evaluated and approved the SGWH modificationsincorporated in all operating PWR plants. Primary emphasis has been on Wand CE SG designs. The recommended design features set forth in NRC'sStandard Review Plant (SRP), Section 10.4.7, Branch Technical Position
26
t
(BTP) ASB 10-2 appear to be effective in preventing (or minimizing)damaging SGWH's. These features (for W and CE SG's having top feed-ring)are a combination of J-tubes on the feedring, short runs of horizontalfeedwater piping (less than 8 feet), and limits on auxiliary feedwaterinjection rates. ASB 10-2 also calls for a preoperational SG test toverify that unacceptable feedwater hammer will not occur using the plantoperating procedures for normal and emergency restoration of SG water levelfollowing loss of normal feedwater and possible draining of the feed-ring.
Damaging steam generator or feedwater system water hammers have notoccurred at any operating PWR which has implemented the corrective measuresdiscussed in this report.
A damaging water hammer event did occur at the San Onofre 2 PWR plantduring pre-operational testing prior to power operation. This event wasdue to overly stringent test conditions and does not change staffconclusions on the effectiveness of design provisions to eliminate steamgenerator water hammers. At San Onofre 2, the steam generator feedring wasallowed to completely drain and fill with saturated steam. The test wasthen initiated by ramping the feedwater from 0 to 1200 gpm in about30 sec. The resultant rapid steam condensation resulted in collapsing thefeedring. The damage was not detected until later when a routineinspection of the steam generator was made. Although the feedringcollapsed, function of the feedring was not impaired.
Until just recently (as noted in Section 2.0), the staff was not aware ofany damaging SGWH phenomenon in B&W OTSG's. The damage to auxiliaryfeedwater rings at the Davis Besse, Oconee No. 3 and Rancho Seco plants iscurrently being evaluated by B&W, the B&W owners group and NRC staff. It
should be noted that the damage incurred did not impair plant normaloperation and that repairs are underway. Initial discussions(Refe-ence 58) resulted in recommendtions to return to the externallymounted auxiliary feedwater header design which has not experienced waterhammer. More recently, Davis-Besse (Reference 59) has committed toreturning to the external auxiliary feed ring design. The NRC staff willcontinue to revewi and evaluate B&W OTSG modifications.
Based on studies, safety evaluations, and plant tests for steam generatorsemploying top feedrings, we have concluded that the measures presentedherein to prevent or mitigate the consequences of SGWH constitutes anacceptable resolution to the safety issues pertinant to SGWH.
With respect to preheat (or bottom feed) SG's (such as W D2/D3 and D4/05models), the water hammer potential for such designs is being evaluatedseparately and will be included in the staff's technical finds regardingUSI A-1, Water Hammer. The basic preheat SG design concept lends itself toless chance for water hammer occurance.
27
REFERENCES
1. U.S. Nuclear Regulatory Commission, " Water Hammer in Nuclear PowerPlants," USNRC Report NUREG-0582, July 1979.
2. Block, J. A. , et al . , Creare, Inc. , "An Evaluation of PWR Steam-Generator Water Hammer," USNRC Report NUREG-0291, June 1977.
3. Saha, P., et al., Brookhaven National Laboratory, "An Evaluation ofCondensation-Induced Water Hammer in Preheat Steam Generators," USNRCReport NUREG/CR-1606, September 1980.
4. Green, S. J., and Welty, C. S. Jr. , " Workshop Proceedings: SteamGenerator Water Hammer," EPRI WS-78-132, (June,1979).
5. Cahill, W. J., Feedwater Line Incident Report-Indian Point Unit No. 2,Consolidated Edison Co., AEC Docket No. 50-247, January 14, 1974.
6. Roidt, R. M., " Steam-Water Slugging in Steam Generator FeedwaterLines," Westinghouse Research Memo 74-7E9-F12NE-MI (January 2, 1975).
7. Bennett, W. E., " Water Hammer in Steam Generator Feedwater Lines,"Westinghouse Technical Bulletin, NSD-TB-75-7, Rev. 1 (March 9, 1977).
8. Lissenden, C. J. , Jr. , " Water Hammer in Steam Generator Feedwaterlines," Westinghouse Technical Bulletin, NSD-TB-79-8 (November 26,1979).
9. Letter from A. Schwencer, NRC, to D. C. Switzer, Connecticut YankeeAtomic Power Company, Docket No. 50-213, dated September 2, 1977.(Similar letters were also sent to other PWR licensees.)
10. Wylie, E. B., and Streeter, V. L., Fluid Transients, McGraw-Hill(1978).
11. Chaudhry, M. H., Applied Hydraulic Transients, Van Nostrand ReinholdCo. , New York (1979).
12. U.S. Nuclear Commision, " Investigation and Evaluation of CrackingIncidents in Piping in Pressurized-Water Reactors, USNRC ReportNUREG-0691, September 1980.
13. T. M. Novak ;NRC) to R. D. Crouse (Todedo Edison Company) letterdated 6/23/82, " Auxiliary Feedwater Header Repair - Request forAdditional Information."
14. U.S. Nuclear Regulatory Commission, " Safety Evaluation Report relatedto operation of Arkansas Nuclear One, Unit 2," USNRC ReportNUREG-0308, Supplement No. 2, September 1978.
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15. Letter from D. C. Trimble, Arkansas Power & Light Company, toK. V. Seyfrit, NRC, subject: Arkansas Nuclear One--Unit 2, DocketNo. 50-368, License No. NPF-6, Startup Report (File: 2-0520.2), datedSeptember 13, 1979.
16. Letter from A. Schwencer, NRC, to C. N. Dunn, Duquesne Light Company,Subject: Amendment No. 24 to Facility Operating License No. OPR-66for the Beaver Valley Power Station, Unit No. 1, dated January 25,1980. ;
17. Letter from A. Schwencer, NRC, to C. N. Dunn, Duquesne Light Company,Subject: Safety Evaluation of Steam Generator Water Hammer at CalvertCliffs Nuclear Power Plant, Units 1 and 2, dated March 10, 1980.
18. Letter from R. Reid, NRC, to A. E. Lundvall, Jr. , Baltimore Gas &Electric Company, Subject: Safety Evaluation of Steam Generator WaterHammer at Calvert Cliffs Nuclear Power Plant, Units 1 and 2, datedMarch 10, 1980.
19. Licensee Event Reports, Available at the Nuclear Safety InformationCenter (NSIC), Oak Ridge National Laboratory.
20. Letter from A. Schwencer, NRC, to J. Tillinghast, Indiana and MichiganElectric Company, Subject: Safety Evaluation Report for SteamGenerator Water Hammer at Donald C. Cook Nuclear Plant Unit No. 1,dated March 14, 1979.
21. U.S. Nuclear Regulatory Commission, " Safety Evaluation Report relatedto operation of Cook Unit 2, Supplement No. 7, December 1977.
22. Letter from G. P. Maloney, Indiana & Michigan Power Company, toE. G. Case, NRC, Docket No. 50-315, dated June 7, 1978.
23. U.S. Nuclear Regulatory Commission, " Safety Evaluation Report forJ. M. Farley Nuclear Plant Units 1 and 2, Docket Nos. 50-348 and50-364, NUREG 75/034, Supplements 1-3. May 1975.
24. Letter from R. W. Reid, NRC, to W. C. Jones, Omaha Public PowerDistrict, Subject: Safety Evaluation Report Regarding the Potentialfor Water Hammer in Feedwater Piping at Fort Calhoun Station UnitNo. 1, Docket No. 50-285, dated December 20, 1979.
25. Letter from D. L. Ziemann, NRC, to L. D. White, Rochester Gas andElectric Corporation, Subject: Safety Evaluation Report for SteamGenerator Water-Hammer at Ginna, Docket No. 50-244, dated December 20,1979.
26. Letter from D. L. Ziemann, NRC, to W. G. Counsil, Connecticut YankeeAtomic Power Company, Subject: Steam Generator Water Hammer GenericIstue, Docket No. 50-213, dated February 26, 1980.
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27. Letter from A. Schwencer, NRC, to W. J. Cahill, Jr. , ConsolidatedEdison Company of New York, Inc., Subject: Safety Evaluation Report
; Regarding Water Hammer in Feedwater Piping at Indian Point Nuclear' Generating Unit No. 2, Docket No. 50-247, dated July 6, 1979.
28. Consolidated Edison Company of New York, " Final Safety Analysis Reportfor Indian Point Nuclear Generating Unit No. 3, Docket No. 50-286,"
:| P.Q 10.24 , Supplement 27, July 1974.
29. Letter from A. Schwencer, NRC, to E. R. Mathews, Wisconsin PublicService Corporation, Subject: Safety Fialuation Report for SteamGenerator Water Hammer at Kewaunee, dated September 13, 1979.
30. Letter from R. W. Reid, NRC, to R. H. Groce, Maine Yankee Atomic PowerCompany, Subject: Safety Evaluation of Steam Generator Water Hammerat Maine Yankee Atomic Power Station, dated March 12, 1980.
31. Duke Power Company, " Final Safety Analysis Report for McGuire NuclearStation, Units 1 and 2," Vol. 4, May 30, 1974.
32. Duke Power Company, McGuire Nuclear Station Unit 1 Docket 50-369,License NPF-9, Startup Report, dated February 1982.
33. U.S. Nuclear Regulatory Commission, " Safety Evaluation Report relatedto operation of McGuire Nuclear Station, Units 1 and 2," USNRC ReportNUREG-0422, Supplement No. 2, March 1979.
34. Letter from N. W. Reid, NRC, to W. G. Counsil, Northeast NuclearEnergy Company, Subject: Safety Evalution of the Steam GeneratorWater Hammer Review for Millstone Nuclear Power Station, Unit No. 2,dated May 7, 1980.
35. Letter from B. J. Youngblood, NRC, to J. H. Ferguson, VirginiaElectric & Power Company, Subject: Issuance of Amendment No. 2 toLicense NPF-7, North Anna Power Station Unit No. 2, dated August 18,1980.
36. Letter from 0. D. Parr, NRC, to W. L. Proffitt, Virginia Electric &Po ar Company, Subject: Issuance of Amendment No. 4 to FacilityOverating License NPF-4, North Anna Power Station Unit No. 1, datedMay 8, 1978.
37. U.S. Nuclear Regulatory Commission, " Supplement No. 10 to theNorth Anna Power Station Unit 2. Safety Evaluation Rep" USNRC Report
NUREG-0053, Supplement No.10, April 10,1980.
38. Letter from D. L. Ziemann, NRC, to D. P. Hoffman, Consumer PowerCompany, Subject: Amendment No. 56 to Provisional Operating LicenseNo. DPR-20 for the Palisades Plant, dated April 30, 1980.
39. Letter from D. P. Hoffman, Consumer Power Company, toD. M. Crutchfield, NRC, Subject: Docket 50-255, License DPR-20,Palisades Plant-Auxiliary Feedwater Modifications, dated December 1,1980.
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40. Letter from A. Schwencer, NRC, to S. Burtstein, Wisconsin ElectricPower Company, Subject: Safety Evaluation Report for Steam GeneratorWater Hammer at Kewaunee, Point Beach Units 1 and 2, and PrairieIsland Units 1 and 2, dated September 13, 1979.
41. Letter from A. Schwencer, NRC, to L .0. Mayer, Northern States PowerCompany, Subject: Safety Evaluation Report for Steam Generator WaterHammer at Prairie Island Units 1 and 2, dated September 13, 1979.
42. Letter from S. A. 'Varga, NRC, to J. A. Jones, Carolina Power & LightCompany, Docket No. 50-261, dated June 2, 1980.
43. Letter from R. W. Reid, NRC, to R. E. Uhri'g, Florida Power & LightCompany, Subject: Safety Evaluation Report for Steam Generator WaterHammer at St. Lucie Plant Unit 1, dated February 7, 1980.
44. Letter from R. E. Uhring, Florida Power & Light Company, toD. L. Ziemann, NRC, Subject: St. Lucie Unit No. 1, Docket No. 50-335,License Condition C, dated March 2,1977 (ID L-77-70).
45. Letter from A. Schwencer, NRC, to F. P. Librizzi, Subject: SafetyEvaluation Regarding Water Hammer in Feedwater Piping at Salem huclearGenerating Station, Unit No. 1, dated November 3, 1979.
46. U.S. Nuclear Regulatory Commission, " Supplement No. 3 to the SafetyEvaluation Report for Salem Nuclear Generating Station, Unit 2, DocketNo. 50-311, USNRC Report NUREG-0517, December 29, 1978.
47. U.S. Nuclear Regulatory C'mmission, Region I Inspection ReportNo. 50-311/81-22, Docket No 50-311, Facility Name: Salem NuclearGenerating Station, Unit 2, C:tober 5, 1981.
48. Letter from D. L. Ziemann, NRC, to R. Dietch, Southern CaliforniaEdison Company, Subject: Steam Generator Water Hammer Issue, datedApril 22, 1980.
.
49. Letter from L. M. Mills, Tennessee Valley Authority, toL. S. Rubenstein, NRC, Subject: Water Hammer Test on Addition ofAuxiliary Feedwater to Unit 1 Steam Generator at Sequoyah NuclearPlant, Docket No. 50 327, dated April 15, 1980.
50. Letter from A. Schwencer, NRC, to H. G. Parris, TVA,Subject: Sequoyah Water Hammer Tests, dated May 13, 1980.
51. U.S. Nucler Regulatory Commission, " Safety Evaluation Report forSequoyah Nuclear Plant, Units 1 and 2, Docket Nos. 50-237 and 50-238,"USNRC Report NUREG-0011, March 1979.
52. Letter from A. Schwencer, NRC, to W. L. Proffit, Virginia Electric &Power Company, Docket Nos. 50-280 and 50-281, dated June 7, 1978.
( 53. Letter from A. Schwencer, NRC, to C. Goodwin, Jr. , Portland GeneralElectric Company, Subject: Safety Evaluation Report for SteamGenerator Water Hammer at Trojan Nuclear Plan, Docket No. 50-344,dated October 18, 1979.
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54. Letter from J. L. Williams, Portland General Electric Company, to'
| W. R. Butler, NRC, Subject: Report on Testing of Auxiliary FeedwaterAddition, Following J-tube Modifications to the Steam Generators ofthe Trojan Nuclear Plant, Docket No. 50-344, dated October 21, 1975.
55. Letter from A. Schwencer, NRC, to R. E. Uhrig, Florida Power & LightCompany, Subject: Safety Evaluation Report for Steam Generator WaterHammer at Turkey Point Plant Unit Nos. 3 and 4, dated February 4, 1980.
56. Letter from D. L. Ziemann, NRC, to J. A. Kay, Yankee Atomic ElectricCompany, Subject: Steam Generator Water Hammer Generic Issue, datedFebruary 5, 1980.
57. Letter from A. Schwencer, NRC, to D. L. Peoples, Commonwealth EdisonCompany, Subject: Safety Evaluation Report for Steam Generator Water
,
Hammer at Zion Generating Station, Units 1 and 2, dated December .2,
1979.-
58. 6/24/82 Meeting at NRC in Bethesda, MD, B&W Owners Group discussion ofgeneric repairs and design modifications related to damaged auxiliaryfeedwater header inside of steam generators.
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U.S. NUCLEAR REGULATORY COMMISSIONg,
BIBLIOGRAPHIC DATA SHEET NUREG-0918
h TITLE AN D SUBTITLE (Add Voeume No., d opreneel 2. (Leave b/mAJ
Prsvention and Mitigation of Steam Generator Water HammerEver.ts in PWR Plants 3. RECIPIENT'S ACCESS!ON No.
5. DATE REPORT COMPLETED7. AUTHOR (S)
Newton R. Anderson, James T. Han Nov her Q?
9. PERFORMING ORGANIZATION NAME AND MAILING ADDRESS (include I,p com/ DATE REPORT ISSUED
U. S. Nuclear Regulatory Commission Nov ber '5982Office of Nuclear Reactor Regulation -
y 7t ,,,, ,,,,
Division of Safety Technologyt!ashington, D. C. 20555 a. It, u, ;
12. SPONSORING ORGANIZATION NAME AND MAILING ADDRESS (/nclude I<a Codri 10. PROJECT /T ASK/ WORK UNIT NO.
Same as 9. 11. CONTRACT NO.
13. TYPE OF REPORT PE RIOD COVE RE D (loctusive damsJ
.
Technical Report14. (teeve alm 4115. SUPPLEMENTARY NOTES
16. ABSTR ACT G00 words or lessJWater hamer in nuclear power plants is an unresolved safety issue under study at theNRC (USI A-1). One of the identified safety concerns is steam generator water hamer(SGWH) in pressurized-water reactor (PWR) plants. This report presents a summary of:(1) the causes of SGWH, (2) various fixes employed to prevent or mitigate SGWH, and(3) the nature and status of modifications that have been made at each operating PWRplant. The NRC staff considers that the issue of SGWH in top feedring designs hasbeen technically resolved. This report does not address technical findings relevantto water hammer in preheat type steam generators.
1 F. KEY WORDS AND DOCUMENT ANALYSIS 17a DESCR:PTORS
|Unresolved Safety Issue A-1
! Steam Generator Water Hammer
a
17tt IDEN TiflE RS OPE N E NDE D TE RVS
l|'
19 SECURITY CLASS (TOs reports 21 NO OF P AGE S18 AV AILABILITY ST ATEVE NT UnclassifiedUnlimited 2o SECuaiTY Ct4Ss <Tms o,,, 22 ea cE
Unc1assified s i
N 8*C F ome 339 5 7 7 7 5
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UNITED ETATESrosfa'tNs ffas 5'io' ^
NUCLEA] REZULATORY COMMISSIONWASHINGTON, D.C. 20565 j5*"j g,
_ Pt awit 4 111OFFICIAL BUSINESS
Pf fe ALTY FOR PAIVATE USE, $300
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