ML20062K960
| ML20062K960 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 12/29/1980 |
| From: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8101090015 | |
| Download: ML20062K960 (28) | |
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THis DOCUMENT C0tiTAlttS POOR QUAUTY PAGES
- 4 SOUTH CAROLINA EtECTRic a gas COMPANY 7 !cn mggg
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CotuMeia, South CApo u N A 29218
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T. C. NsCHots JR w,..... c, cuco.
Deeember 29, 1980 um u. o,.. -
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y Mr. liarold R. Denton, Director i
Of fice of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Subject:
Virgil C. Summer Nuclear Statice Docket No. 50/395 Containment Sumps
Dear Mr. Denton:
South Carolina Electric and Gas Company acting for itself and as agent for the South Carolina Public Service Autharit, provides forty-five (45) copies of our response to questions on the Reactor Poilding Sumps. Attachment 1 includes a copy of question 211.132 and its response.
Full flow testing of the sump was performed as a part of the start-up testing procedures.
In addition to these tests, the containment sumps will be model tested by Alden Laboratories. We will inform you prior to the model tests so that you may attend. A copy of the Alden Laboratory proposal is provided as.
The combination of our initial testing, testing to be performed by Alden and this written response to the question should provide you with enough infor-mation to close out this item.
If_you have further questions, please let us know.
Very truly yours, l
lW
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,b T. C. Nichols, Jr.
NEC:TCN:glb
Enclosures:
cc:
V. C. Summer w/o enclosures A. A. Smith G. !!. Fischer w/o enclosures A. R. Koon T. C. Nichols, Jr. w/o enclosures R. B. Clary E. 11. Crews, Jr.
J. B. Kno t t s, J r.
gdg O. W. Dixon, Jr.
J. L. Skolds T
D. A. Nauman B. A. Bursey j
- 0. S. Bradham NPCF/Whitaker W. A. Williams, Jr.
File
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- 810 3 o e col 5 h
ATTACHMENT 1 211.132 Containment Sump and its effect on long term cooling following a LOCA During our reviews of license applications we have identified concerns related to the containment sump design and its effect on long term cooling following a Loss of Coolant Accident (LOCA).
These concerns are related to (1) creation of debris which could potentially block the sump screens and flow passages in the ECCS and the core, (2) inadequate NPSH of the pumps taking suction from the containment sump, (3) air entrainment from streams of water or steam which can cause loss of adequate NPSH, (4) formations of vortices which can cause loss of adequate NPSH, air entrainment and suction of floating debris into the ECCS and (5) inadequate emergency pro-cedures and operator training to enable a correct response to these problems. Preoperational recirculation tests performed by utilities have consistently identified the need for plant modifications.
The NRC has begun a generic program to resolve this issue. However, more immediate actions are required to assure greater reliability of safety system operation. We therefore require you take the following actions to provide additional assurance that long term cooling of the reactor core can be achieved and maintained following a postulated LOCA.
1.
Establish a procedure to perform an inspection of the containment, and the containment sump area in particular, to identify any materials which have the potential for becomi:ft; debris capable,
of blocking the containment sump when required'for recirculation of coolant water. Typically, these-materials consist of: plastic bags, step-off pads, health physics instrumentation, welding equipment scaffolding, metal chips,and screws, portable inspection lights, unsecured wood, construction materials and tools as well as other mtscellaneous loose equipment.
"As licensed" cleanliness should be assured prior to each startup.
This inspection shall be performed at the end of each shutdown as soon as ptactical before containment isolation.
2.
Institute an inspection program according to the requirements of Regulatory Guide 1.82, item 14.
This item addresses inspection of the containment sump components including screens and intake i
structures.
3.
Develop and implement procedures for the operator which addresses both a possible vortexing problem (with consequent pump cavitation) and sump blockage due to debris. These procedures should address all likely scenarios and should list all instrumentation available
d to the operator (and its location) to aid in detecting problems which may arisa. indic,tions tbn operator should look for, and operator actions to mitigate these problems.
4.
Pipe breaks, drain flow and channeling of spray flow released below or impinging on the containment water surface in the area of the sump can cause a variety of problems; for example, air entrainment, cavitation and vortex formation.
Describe any changes you plan to make to reduce vortical flow in the neighborhood of the sump.
Ideally, flow should approach uniformly from all directions.
5.
Evaluate the extent to which the containment sump (s) in your plant meet the requirements for each of the items previously identified; namely debris, inadequate NPSH, air entralument, vortex.ormation, and operator actions.
The following additional guidance is provided far performing this evaluation.
1.
Refer to the recommendations in Regulatory Guide 1.82 (Section C) which may be of assistance in performing this evaluation.
2.
Provide a drawing showing the location of the drain sump relative to the containment sumps.
3.
Provide the following information with your evaluation of debris:
a.
Provide the size of openings in the fine screens and compare this with the minimum dimensions in the pumps which take suction from the sump (or torus), the minimum dimenoion in any spray nozzles and in the fuel assemblies in the reactor core or any other line in the recirculation flow path whose size is comparable to or smaller than the sump screen mesh size in order to show that no flow blockage will occur at any point past the screen.
b.
Estimate the extent to which debris could block the trash rack or screens (50 percent limit).
If a blockage problem is identified, describe the corrective actions you plan to take (replace insulation, enlarge cages, etc.).
c.
For each type of thermal insulation used in the containment, provide the following information:
type 'f material including composition and density, 1.
o ii. manufacturer and brand name, iii. method of attachment, iv.
location and quantity in containment of each type,
v.
an estimate of the tendency of each type to form particles small enough to pass through the fine screen in the suc-tion lines.
d.
Estimate what the effect of these insulation particles would be on the operability and performance of all pumps used for recirculatica cooling. Address effects on pump seals and bearings.
Additionally, previous in-plant sump tests did not accurately repli-cate expected post-LOCA conditions, and thus did not demonstrate acceptable sump performance under ECCS recirculation conditions.
Specifically, the plant test only pulled auction from a single line, when there are two lines in each of two sumps.
This resulted.In test approach flow velocities which were lower than would be expected during a LOCA.
Additionally, various flow approach directions were not investigated to determine if undesirabic rotation could be induced in the sump area, which could lead to vortex formation.
Finally, sump screen blockage due to debris entrainment was not con-sidered, with the correspondingly higher screen velocities wh!ch also could aggrevate vortex formation.
The applicability of your sump tests, and the adsquacy of your sump design under post-LOCA conditions, in light of these staff concerns should be addressed to provide assurance that reeirculation sump performance will be acceptable following a postulated LOCA, and that undesirabic vortex formation will not be experienced.
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RESPONSE
1.
The Virgli C. Summer Nuclear Station Technical Specifications require that each Emergency Core Cooling System (ECCS) subsystem be demonstrated operable by a visual inspection. This visual inspection verifies that no loose debris is present in the Reactor Building which could be transported to the RHR and RB Spray sumps to cause restriction of their pump sucticas. This inspection is performed immediately prior to establishing containment integrity for:
1.
the' Reactor Building areas affected during the ctage, and 2.
all accessible areas of the Reactor Building.
Station Surveillance Test Procedures cover these requirements.
2.
The Virgil C. Summer Nuclear Station Technical Specifications require a visual inspection of each ECCS subsystem at every refueling outage.
Station Surveillance Test Procedures have been written to satisfy these re-quirements. The suction inlets and sump components are inspected to ensure that debris is not present and that no evidence exists of structural distress or corrosion.
3.
An inst'ruction dealing with possible ECCS sump blockage is contained in the Virgil C. Summer Fuclear Station Emergency Operating Procedure (EOP-1).
This procedure addresses long term cooling and requires the operator to monitor pump flow and motor amps when in the sump recirculation mode.
It also cautions the operator that if pump flow and/or amps decrease, the cause may be sump blockage.
If there is an indication of sump blockage, the operator is instructed to monitor the sumps for signs of cavitation and the piping for water hammer.
If suction is completely lost, the operator is instructed to stop the affected pump.
During the classroom training session on E0P-1 for station operators, possible actions that may be taken in the event of a blocked screen are covered.
For example, a blocked sump could be backflushed using water which may remain in the RWST.
4.
See response to number 5.
5.
Four independent ECCS sumpc, 2 RllR and 2 RM Spray, are provided in the Virgil C. Summer Nuclear Station.
FSAR Figure 1.2-4 shows the physical separation between these sumps and the Reactor Building drainage sumps.
The Reactor Building drainage system as well as the Refueling Canal drain are located such that direct water flow does not impinge in the sump areas.
There are no high energy lines in the areas which will subject the sumps to pipe or jet impingement loads and cause subsequent damage.
There is also a 6 inch curb around the upper floors to keep water from cascading down the containment wall to the sumps below. Water from the upper floors will tend to go down the stair wells.
Each of the four sumps is located below the working floor elevation and are surrounded by 6 inch high trash curbs. The LOCA condition water level when reciceulation begins is approximately 6 to 7 feet above this working floor elevation. A horizontal grating acts as a trash rack over each sump and
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,s two verticle screens, one with h inch openings and the other with k inch openings, act as the suction strainers. An inner sump extends below the strainers an additional 8 feet to the suction inlet pipe. A horizontal top plate covers the strainer screens and the inner sump and includes a hatch for inspection purposes. The hatch clearances provide air vent gapa for the top cover plate.
Components of the ECCS sumps are seismically designed and are constructed of stainless steel except the grating which is of galvanized steel.
There are two types of insulation inside primary containment, Mirror and Temp !bt.
The Mirror insulation is attached by metal bands and rivetted buckels.
It covers vessels and piping (except for the steam generator reference leg piping).
The potential for mirror insulation to be torn away from its pipe and causing a blockage problem is limited by:
1.
the method of attachment to the pipe, 2.
the fact that it tends not to break up after separation from the pipe, 3.
the fact that it will sink to the bottom of the containment pool, and 4.
only a small quantity is located outside of the missile shield wall in the area of the sumps.
Temp !bt is a fibrous insulating material manufactured by Pittsburgh Corning.
It is attached by a stainless steel jacket that is rivetted in place.
Ap-proximately 210 square feet, 70 per steam generator, of 2 inch thick insulation cover the steam generator reference legs. (Insulation on the re-ference legs is an interim modification suggested by Westinghouse. The final modification will not involve insulating the lines.) For the insulation in a single steam generator compartment to become a blockage source, it would have to separate from the pipe and jacket and then maneuver through the I
missile shield openings and around to the sump areas. An additional 440 square feet of 1 inch thick Temp Mat covers the pressurizer equipment cooling duct as it branches from the Reactor Building cooling duct and enters the pressurizer cubicle. Over half of this insulation is actually inside the cubicle.
For the ductuork insulation to become a potential problem, a pipe rupture of the main steam loop A line or a line inside the pressurizer cubicle would have to occur.
Then either a jet impingement or pipe impact load would have to tear the insulation and duct work anart.
For the insula-tion outside the cubicle, it would then have to go down three floors to get to the sump areas.
Several grating floor elevations inside the pressurizer cubicle are between this insulation and the floor.
The insulation would then have to pass through the 3' x 9' -
6". door opening and then make its way from elevation 436 to the sump floor elevation 412.
Temp }bt tends to float 'due to entrained air.
Ilowever, if it does sink, tests show it acts as a filter element.
No significant effect on flow is indicated when a blanket of the material is placed over a sump drain.
Other potential blockage sources include:
1.
Fifteen fibrous reinforced silicon rubber enclosure- (approximately 4 square feet each) which provide forced air cooling of equipment inside the pressurizer cubicle,
2.
Jubber expansion joints in the ring header duct, and 3.
Rubber boots for reactor nozzel and support feet ventilation (6 total at approximately 14 square feet each).
The blockage potential of the equipment covers is subject to the same location consij gations as.the Temp 1m > taside the pressurizer cubicle.
In addition, the covers are located high in the cubicle and would have to clear instruments, piping, and grating to reach the cubicle opening at the bottom The ductwork expansion joints ard so renoved from the sumps and potential missiles that their blockave potential is very small.
The reactor nozzel and support ventilation boots are bolted to the wall and clamped to the pipe.
Ho.e/er, became fredue to its physical location, it would most likely re-if a boot e
main in the incore instrument tunnel.
The potential for debris getting into the suction piping and causing blockage or damage to the pumpn or other components, is greatly reduced by the trash racks and screens.
For the components in the ECCS flow path the Reactor Building Spray nozzles are the determining f actor for sizing the smallest strainer 'creens.
Strainer vreens witF h m.h v, care openings will allow only those particles smaller than k inch square to pass completely through the system.
In order to perform a complete analysis, SCE&G has contracted Alden Research Laboratories to institute a model study c' the Virgil C. Summer Nuclear Station ECCS sumps and suction piping. The study will investigate several design phenomena including swirling and vortexing under full flow and 50% block strainer conditions, lesses leading to insufficient NPSH, and air entrainment.
Scaling factors will also be evaluated to ensure similarity between the model and prototype operating under LOCA conditions.
If problems with the current design are uncovered during the study, design modifications will be investigated until an adequate solution is found.
These design modifications will then be mm'c to the full scale sump designs.
RUR and RB Spray pump flow beyond rated runout is another condition which requires evaluation.
Due to the different known and unknown conditionc of operation, this evaluation is more important for the RHR system.
Therefore, full scale tests of the RilR pumps were performed at the Virgil C. Summer Nuclear Station for the different modes of injection and recirculation.
As a result of these tests, flow restricting orifices have been installed at the outlet of each heat exchanger.
A retect of the RilR system will be performed to insure the adequacy of these orifices.
A full scale test of the RB Spray discharge ring headers and spray nozzels is not feasible, llowever, this system is only subj ected to two worst case operating conditions, injection and recirculation, as its design basis.
Full scale tests have been performed using the suction and recirculation test returns to the RWST.
Test data on the suction piping will be compared to the results of the design calculations as a measure of their accuracy.
A detailed analysis will then be performed of the Reactor Building Spray System's calcula-tions to ensure that flow rates beyond runout are not possible.
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ATTACilMENT II O
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liYDRAULIC 140 DEL STUDY CF CC:JTh!":-T;;T SU:'P FI'GIDUAL !! EAT REMOVAL SYSTEM VIRGIL C.
SUIC'ER I;UCLEAR STATIO:1 i
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1:ovember 1980 t
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Pw)POSAL IIYDRAULIC !?ODT:L STUDY OF CC:1TAII;;"E:iT SUMP REGIDUAL !! EAT REMOVAL SYSTEM
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U VILGIL C. SUMcR 11UCLEAR STATION l
- This proposal is submitted to the South Can iir. Elt_ctric & Gas Company in accordance with their request for proposal dattJ October 30, 1930.
i I!!TRCDUCTIO:1 i
The Contairxent Sumps for t' Virgil C. Sumner liuclear St
- t. ion are located i
F in the reactor containment building close to the containment wall as sho,in in rigure 1. Pour cumps supply two residual heat removal pumps and two re-actor building spray pumps.
One RilR and one sp' ray sung are located adja-cent to cr.e another in each of two r. hallow sumps in the floor of the reac-tor building at elevation 412 ft.
The trapezoidal. shallow sung is about.
22 ft by 10 ft in plan ard is 4 fL deep.
A 4 ft wide wall extending 3 ft high f rom the sung ilcor s parates the luiR and spray sumps w'. thin the shal-low sump.
T'r.c second pair of sumps are located about 20 ft away.
A 6 inch high curb currounds the shallcw sumps and standard floor grates cover the s
entire sunp arca at the curb elevat. ion.
Uithin the challow sung, tuo 4 f t square surnps decend 8 f t to c1cyation 400 ft.
The R:!R ar.d spray pu:,p inlets, 34 inches and 12 inches in diameter, re-spectively, exit the deep sur..ps horizontally at elevation 402 ft.
A quaci-
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bellnouth cor.sisting of standard reducera is used on both inlets. The inlet i
piping to the pumps extends hm inontally with a shsllow slope about 56 ft
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tn on ir,olaticn valve prior to the pump.
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In addition to the horizontal floor grating, two set's of screens are located i
in the shallow sump to assure no trash is entrained into the pump systems, i
5 An outer vertical, screen is made of 1/2 inch mesh extending from elevation 1
408 f t to 410 f t and is 6 f t square in plan.
This outer screen has a solid cover e:<tenrling from elevation 410 f t to < tovation 412 and a horizontal solid i
cover at elevation 412 ft.
An inner 1/4 1 ich mesh vertical screen has the dimenr;cns of the deep sump, 4 ft nquare. The inner screen extends from ele-
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vation 110 ; t t.o tlevatien 411 it, !1 inchen.
A solid plate covers the in-i l
nce nercta and solid plates extend froa the botton en the shallo.: sump at f
elevat.!ca '403 f t to elevatkien 410 f t.
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i The biochield wall is adjacent to one sump, while the other cump has several feet of clearance to the inner wall.
Various components, such as the accu-nulator tank, complicate the nearby geometry.
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In the recirculation reode, after a postulated loss-of-reactor-coolant acci-i dent, water primarily approaches the cump by flowing through several open-4 ings in the inner bicshield wall into a channel formed by the biochield and containment walls, in which the recirculation sunp is located.
These open-1 ings are relatively remote from the su~ps. A secondary flow path to the sump is from the next level arcve the sump through an annular opening along the l
containrent wall.
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The runout flm: for the R:iR pumps and the spray punps are 4500 gpm/ pump and
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JOOO gp:/pu. p, respectively.
The minimum water level is at elevation 418 ft, giving a mininun subnergence of approximately 16 ft at the suction pipes.
ALVf:R5E FLOW CO::DITIONS TO HE INVESTIGATED
,j The following c.ro some of the likely flow conditions in the containment surp which could cause poor pump perfornance (1), and will hence be investigated a
I in the rodel study.
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1.
S..irl,ing Flow - The various possible approach flow patterns, together 1
with possible screen blockage and vortexing, could induce swirl in the station pipes, which in undesirable for the pumps.
Excessive,
I swirl could alro affect the intake losses, and thereby the available MP55'for the punps.
Scverity of swirl will be nearured in the nodel using a vortine;or in the suction pipe.
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Lesnes Leading to Insufficient NPS!! - A roorly designed sump could l
F result in large intake louces.
Intake losses cauncd by racks and i
i cerccns (including blockage by debr i s), peor entrance flow condi-
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7 tican, vortex cu,pression devices, inlet dusign, etc.,.uy add up
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to a v..lue such that the required U." Sit of the punp is not sa t i n f i,-d.
Irdet lc-sscs are dif ficult to calculate thcoretically, and nodel
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tenta give a rcliable value of f niet losses.
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Entrained Air - Air entrainment,in the suction pipes could be due to t
strong free surface vortices, flow impingement from the upper level,
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It is and/or suct. ion of ent rapped air' below sub. merged cover plates.
establiched that even low air concentration in the suction pipes, such as 3 to M.,
could lower the efficiency of a pump considerably (11).
Hence, potential air entrainment is recognized as a major flow condition in the sung to be examined.
As the cump area and vicinity are not exposed t.o breakflow jets because of the sump loca-l tion outside the biochield wall, air entrainnent due to breakflow l
I jets will not be of concern in this study.
Potential air entrain-nent by uater fro.a the floor above must be considered unless field modifications are feasible to eliminate that flow path near the i
suans.
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SCALING COMSIDERATIONS
?:odels involving a free surface are operated using the Froude similarity criterion since the flew pattern is controlled by gravity and inertial forces. The Proude nu nber, F,
representing the ratio of inertial to gravitat icnal force, 4
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l F = u//g5 i
where u = average velocity in the pipe 9 = gravitational acceleration sa sub::v:rgence is, t.herefore, nade equal in model and protot ype.
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F = F /P
=1 l
r ra p t
where n, p. and r denote incdel, protot ype, and ratio letween rodel and pro-toty;>e, tornetively.
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7 In modeling an inta};c surp to study the formation of vortices, it is impor-5
.__ tant to select a reasonably large gecmetric scale to achicve large Reynolds numbers to achieve. turbulent flow and to reproduce the curved flow pattern in the vicinity of the intake (2).
IIoveve r, the gewetric scale ratio of the model also controls the cost of construction and operation of the model, therefore, careful judgnent is necessary in selecting the scale ratio.
The fluid : otions involving vortex fornation in pump sumps have been stu-died by several investig?. tors (2, 3).
Anwar (2) has shown by principles of dimencional analysis that. the dynamic sinilarity of fluid motion in an intake is governed by the dinensionless parameters given by:
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, 1, and b 1
vs 2s 2
j 9" u 0 where i
Q = discharge through the outlet u = tangential velocity at a radius equal to that of 0
,the outlet, pipe d = diameter of the outlet pipe Surface tcasion ef fects were shown to be negligible in this analysis.
The influence of viscous effects was defined by the parameter Q/(v s),
known as the radial Reynolds nunber,,Rg For similarity between the dincn-sions of a vortex of types up to and including the narrow air-core type, it was 91.own that the influence of R becomes negligible i f Q/ (v s) vas greater f
4 than 'l x 10 (2).
As strong air core type vortices, if preocut in the raudel, j
would have to be clininated by modified sump design, the main concern for in-
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l turpretc. tion of prototype performance, based on the model 1,crfor::ance, uc>uld be on the sini1arity of weaker vortices, such as surface dimples and dye cores (see attached chart of ARL vortex classification, Piqure 3).
- Thus, 4
t if H is greater than 3 x 10 siccous forces would have only a secondary j
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. role'and dynatic binilarity'vould La obtais.ed by equaliving the parameters l
4'.'/u < l af.'29s, and d/2G in the :wdcl a::d prototype.
A Froudien model i
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would catinfy this condition.
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In order to account for secondary viscous forces, various investigators
.(4, 5) have proposed increasing the rodel flow and, therefore, the velo-city, keeping the submergence constant. Considering this, the model used
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in this study would have the capability of running at the prototype velo-i city.
Also, indicators are that good nodel to prot.otype vortex correla-I tion can be achieved by keeping the ratio of inertia to viscous forces large in the model (i. e., large Reynolds numbers). For Reynolds nunbers, Il (based on pipe velocity and pipe diamet.er) greater than 3.2 x 10 d
i the influence of viscosity would be negligible (3).
ARI, has conducted an ext.cnsive research program to independently assure that. the conclusions of the above investigat. ors are valid.
A technique of extrapolating vortex activity to prototype Reynolds numbers (6) by using elev 'ad model water temperatures and increased nodel flow velo-city (Froude ratio) has been applied to scveral studies (7, 9, 12, 13).
j Experience has shcwn that incoherent swirling flow is even less depen-dent on Reynolds nu:.ber than a coherent vortex core.
Eliminating the
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tendency for coherent vertices axiomatically removes any possible scale effect. In reactor cr ps, the design criteria eliminate the loosibility 6
of coherent vortex cort s in an accept.able design.
Figure 2 shows the results of one typical recirculation sump model (9).
As can be seen from the data, which are for the final design with vortex supprescor I
grids, there are no neasurabic changes in vortex strength with Reynolds nunbar. Therefore, it is concluded that elevated temperature tests are i
not required in this test program as no scale effects will be prcrent in the final design.
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-Por this study, it is reco.=nended that a nodel be cenetructed to a gcome-I t ric :$cale of about 1:2.6.
Por t his scale, the internal diameter of the RilR suction pipes corresponds to a standard pipe size, 5.05 inches.
The minimum pipe Reynolds number anel radial Reynolds number used in the co-dol, for a Froude rat.io of 1.0, trould be 1.99 x 10 and 3.05 x 10 re-sper:l i ve ly.
At these Ecynolda nm..bers, the viscous effects en the vor-
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t < :-:ing i hm5enen teuld be negligible (2, 3), again indicating the ab-Lence of any scale effect.s.
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noDEL DESCRIPTION i
The model would be constructed to a geometric scale of about 1:2.6 with
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boundaries an indicated in rigure 1,' and would be operated conforming to Proude's Law of Similarity.
Ecth pairs of pumps are included in the pro-posed model since the geometry of the bioshield wall controlling the ap-proach flow is suf ficiently dif ferent and t.he deep our.ps and screens are oriented differently in the shallow sumps.
An cxisting elevated tank of sufficient size is available to contain both shallow sumps.
Model bound-aries have been chosen relatively close to the sump since previous studies i
(7, 9, 12, 13) have indicatcd litt.le effect of farfield flow patterns once the dominant nearfield screen blockage is considered.
Screen blockage has consistently generated the most severe vortexing and swirl in the numerous past ECCS nemp studies c.t the ARL.
Inflow to the model will be supplied from a surp by an existing pump of suitable capacity. Portions of the pro-totype st.ructure, such as colu:ans, conduits, and pipes.with external pro-totype dirensions of 3 inches or larger, in the ire.ediate vicinity of the
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sump and below the water surface which might affect the approach flow pat-turn to the sump, would be modeled to the geometric scale.
The details of the prototype appurtenant structures and pipes to be included in the model would be confirr.ed by a site visit during the design stage of the j
study. The various structtues inside the bioshield wall, such as reactor
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coolant drain tank, steam generator nuoports, etc., need not be modeled
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i being away,fros.. the sump area separated by the bioshield call.
Effects of ar.y approach flow distribut: ions will be studied by suitably blocking p
the approach openings in the model.
The more critical upproach geonetry I
will t.htn be studied with various screen blockages, f
The model will be constructed using a combination of,od and steel, and clear act ylic will be used for the sump to allow observ ition of flow pt-1 t en nn. Uater level in the nump will be cont: rolled by an adjustable weir.
The RIIR and spray pump suction 1>ipes vill be modeled for greater than 10 diamet.cru and each will contafn a swirl meter and prc ssure gradient taps.
The discharge thrcugh each suct ien pipe will be masured using calibeted
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flow ~.eters.
Dye will be used for flow observat ten and Jd.cnti-ication of
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vort ices, rull document ation of the data vill be mado, and phutographs uill be t aken thenever appropria' e.
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7 i
As. previous ARL basic studies have shown (8), scaled gratings are as effec-1 3
. tive in suppressing nodel vortices as are full size gratings in suppressing fu)i size vorticos, therefore, all gratings erployed'in this study will be
~
i I
geo-etrically scaled. The scretan used in the model will be chosen with approximately the same open area as in the prototype, and this has been f
shown by separate studies to control the head loss and effects on flow patterns (10).
The effret of screen blockage will be studied using vari-ous possible configuraticns of up to EM blockage.
As the sump is locat-l ed carside the bios ield wall and is protected frcm /; rect jet impingement, simulation of breakflsws is not neccssary and is not considered in this proposal.
k i
IM5TFJ:C:TATION AND OESEPVATION TECI:MIQUES General Descrintion i
1
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)
An orifice plate flow rmter w uld be use d to measure the flow in cach suc-1 tion pipe.
Approach flow patterns and vortices in the su:,p area would be observed with the a n istar.cc of dye tracers.
Swirl in the pipes vculd be measured using a vortir.eter and elec_ronic counter.
Pressure gradients would be obtained in the suction pipes to dcLermine the inlet loss coeffi-i cients under vaticus operating condit. tons w.tth possibic screen blockage.
[
1 Specific Description i
f j
Plow :basurcments - Plows will be n':asured by AO:M st.usdard meters located
?
i in the appropriate lines.
1 i
Observatica of Flow Pattcrns - Virual aids, such as dye and t.ufts of j
thread, would be,used to observe flow patterns.
Photographic documenta-I tion
.-.:uld be taken whentver appropriate.
Portions of the vedel in the
+
su,p a c t would be of t rcusparent mterial to facilitale visual observa-L 3 cr.s.
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Vor ticity - Vortex activity for AHL stadies hac been recorded by observ-ing vc*)rtex strc ngth on a scale from 1 to 6 (rigurc 3), and by' determining
~ the percent ol Line for 'each strerigth. Vortices would be identified by
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1 visual aids. A vortimeter would be built and installed in the suction t-F pipe,to indicate the swirl in the pipe.
l Pressure - Average pressures will be nonsured using piezometers connected to air-water nanometers.
Damping of pressure fluctuations can be controll-ed by varying the cross-sectional area of thc manometer.
t
. TEST PROCEDURE f
Tests on the taodel would be conducted at the normal laboratory water'ter.-
perature uting the given minimum submergence and two pumps operating. T.;o flowrates will be tested:
(1) the scaled flowrate, and (2) the flowrate corresponding to cqual prototype velocity.
(
i The following flow pattern variations will be i raplet.ented :
1.
uniform approach flow and no gratings or screen blcckage, i
2.
non-uniform approach flow from the farfield model area.
Since previous ctudies at ARL (7, 9,
12, 13) have shown flow varia-I tion of the farfield has a minimal effect on' sump performance, t
+
only about six variations will be tried for both approach geo-t l
j
- untries, t
l 3.
50% blockage of the horizontal grating and the two vertical
(
screens.
Up t.o 12 blockage configurations will be tried in an effort to obtain the most adverse blockage scheme.
Tcuts will be conducted with both pumps oporating at two flowrates for all blockage schemen, and selected blockage schenes will be tcsted with fingle pump operation.
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9 r=,
The following data would be obtaincd: (1) vortex severi ty within the sung, (2) ricacurenent of head Jo'ss acrocs the two-staged inlet screens,_ (3)
~
nwirl angle in the pipe inlets, (4) prennure gradient measurements in the mods ' ed ';uc tion pipea, and (5) pocrible air ingestion from under solid cover plates.
It is poncible that nr.t all the tests outlined above would be conduct ed if prob 1cna cre apparent and revisions are required.
On con-sult at ion with fouth Carolina Electric & Gan, changes to sump screens and grat ings waald be proposed to ansure a sat.icra< tory design. The final de-nign would also be checkei for catisfactory perfor-ance for a few critical operating ccnditions at water levcis above and below mininun submergence.
SCIIEDULE The denign and construction of the nudel could be started within two weeks after iorr.il authoriza m n.is obtained. The design, construction, and fabri-cation of the i.. reel mld r; quire a total of eight weeks.
The testing pro-gran of tl.a p.ra cred design is estinated to require about six weeks.
Minor k'
remedial work, nach cs a:idi.t ion of horizontal grati ng wi thin t.he deep sunps,
in estimted to rulu e an additional two week test period.
The preparation of a draft report c:vering all aspects of the stu ly is esti :at cd to recuire four weeks and would begin upon corpletion of the tent work.
Thus, the to-tal duration of the n.odel stedy from inceptien to submission of a draft re-port would ? 9 about twenty-two weeks, assuming no alterations are required.
The 'e>.ptrirental data and result.s would be availnble as the test progran j ' rog ".% S Cd.
COST Yhe cost for t.he deuign, construction, testing, and reporting for t he pro-t o:ar.1 d< s i gn, including cort. of materialn, using and incorporating such equi} cent and f acil i t les as a t e ava i lable at APL, c=f."J' C" *.~O70.CCT The cont. of a site visit by ARL personnel in included in the cost esti-mate.
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MEETIIIGS Although c r recent experience indi ates that ur reports are sufficient for IIRC review purInses and, therefore, our participation in I RC hearings i
or meetings is unnecessary, any support required for answering inquiries or attending nectings would be charged per our General Policy for the person's time and associated travel expenses. '
l PERSO!!NEL The model study would be under the general direction of Professor George E.
liccker, Director of the Alden Research Laboratory.
Profersor llecker, who has just expleted a torn as Chairman of an ASCS Task Cornittee on Intake
- Vortices, may be contacted at 30 Shrewsbury Street, !! olden, !!a s sachuse tts,
01520, or by calling (617)S29-4323.
14 ore specific guidance and supervision 3
I would be handled by Dr. Jar.es B.
Nystrom, Lead Research Engineer.
Other
(
crgineers, technicians, and craf tsmen from AHL would be assigned as appro--
iniote.
Resunds of enginecru likely to be involved in the study are en-
- closed, i
I t
PAST EXPERIENCE WITil PUMP INTAKES I
,i ARL has conducted several hydraulic r.odel studies of reactor containnent sumps, cooling water intake sumps, and 1 imped storage intake structures, all of which have required elaborate testin; and observations of approach flow initterns, forr.ation and type of vortices, suirling flow in the suc-tion pipes, and inlet losses.
Brief descriptions of some studies conduct-ed or being conducted at AHL in the above areas ire given below so as to provide definite examples of ARL's experience in similar ef f' orts.
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I e
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11 T
A.
Reactor Containnent Supp Models s
' The nadels of reactor;contajnmer.t su:ss' arc designed based on Proude.sini-(-
larit.y to include the su p and the surrounding area with all the structures y
and piping which could influence the approach flow.
In deciding the geone-tric scale, due considerations of sinulation of curved flow patterns, vor-tcxing, and pcssible scale effects due to viscous and surface tension forces are given. Testing to observe the flow patterns, formation and type of vor-tices, and prerotation and swirl effectn, are undertaken for the various op-erating conditions, including restrictions such as screen blockage.
Evalua-
.i i
tion of initt icss coefficients for the various conditions ir nado to verify i
j available 575H.
Incorporation of vorter. suppressors or other design modifi-cations are derivcd and substantiated as necennary.
Detailed studies on pos-sible scale effects involving high terperature-high velocity testing, derived by APb rosaarchers are conducted before projecting the prototype performance i
and making recorcndations.
The following are sump codel studies conducted or currently being conducted by ARL.
3 s.
i 1.
Three Mile Island Nuclear Power Station - 1:3 nodel, investiga-f tion completed, report available, sponsored by Burns and Poe, Inc.
4 I
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2.
North Anna Nuclear Power Station, Unit 1 - 3:3 model, investiga-tion conpleted, report available, sponsored by Virginia Electric
.& ?ower Campany.
r 3.
McGuire and Catawba Muclear Power Plants - 1:3 nodel, investiga.
l l
tion complet.ed, report available, sponsored by Dnke Power Company.
[
4 4.
D.C.
Cook Muclear Power Station -- 1:2. 5 model, investigation I
cc:9ple t ed, report available, sponsored by American Electric Power r
Service Corporation.
l 5.
Scabrook Nuclear Statica - 1:4 model study, investigation under-
[
ua/, cronsored by Yanb e Atenic Electric Ccmpany.
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Sal, m Generatirig Gtation - 1: 2.3 rodel study, invest igation under-u,iy, sponsored by Punlic Service Electric and Gas Company.
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D.
Coolin<j Uater Intake Sumps I
j Model st.udies of cooling water intake cumps are conducted to invectigate l
11ce patternc in the approach region, pump bays, and at the pump bell, and to derive nuitabic devices to streamline the flow pattern and to sup-1
+
press vort ex form:ition, if any.
Often, t.he flow pat.Lorns recu1 Ling from i
few of the pumps operating in a nycten with nany adjacent bays are of a
impor t.ance.
Velocity ucasurements in the cump, cwirl in the pump column, 4
l flow visualization and photography to identify vortexing, etc., i.re com-1
?
menly ir.cluded in the nciel study.
Geometric simulation of bellmouth l
j shape, deter-ination of flow patterns entering the bellaouth, and swirl-l ing flown inside the pipa, Arc also important.
Models are operated ac-
]
cording to Proude's Law of similarity.
The foilowing art. some of the-1 cooling wat(.r intake.odel studiec conducted at ARL.
i i
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l.
Seabrock Condirser Circulating Cater Pump Intake - 1:12 ncale j
j i
model, appros.ch flow patterns and vortex observations, ocl.fi-calien '.o 'i:' pro te pe r fornance rebemended, 'rcport avail.ble, j
sponrored by Pa' lic Service Company of New licmpshire.
j t
2.
tierry nuclear Powar Plant Of f shore Intake Struct.ure - 1:25 ccal-l Inodel of three submerged intaken, flow velocitics at ports, hecd 1
j lonsep, etc., measured, objective to minimize fish entrapment, I
report available, sponsored by Cleveland Electric Illuminating Company.
l 1
3.
Perry nuclear Power Plant Coo'ing Tower Int ahe - 1:16 scale r.o-del of punp intake ut ructure, three bays nodeled, original de-sign nodi fied to reduce vorticity and i:r. prove approach flou dis-l l
tribution, report available, sionso' ed by Cleveland Elect ric l
I 11 ual na t.ing Co.,.pany.
l t
4.
Mitchell Pouer Plant Intake - 1:10 r,cale model of harimu'..a t rump
(
i nt ake*;, vortex activity noted, vortex nuppressing device recom-ra.nded, report available, sponsored by Worthington rua.p Corporation, i
i
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_--o---.--,++---*--~-+a
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5.
McGuire 1:oclear Power Station,. Condenser Cooling Water Intake -
flow pattern vis-i 1r15 raodel of four vertical suction inlets, nalization in pumpwell and bellnouth, optimization of pump lo-cation, report available, sponsored by Duke Power Company.
6.
Bridgeport 11 arbor Steam Electric Station - 1:8.7 scale nodel of. ster intake structure, observation of cddies ar.d vortexing, i
baffling suggested to inprove vortexing problems, report avail-abic, prototype oper,tes satisfactorily, sponsored by United Illuminati ng Con;;any.
7.
Ucrtc;crt Dilution pumps - 1:9 scale inodel of pump intake struc-ture with two 247,0D0 gpa vertical shaft pumps.
Existing design ncdificd to reduce surface and subsurface vortex activity which greatly increased pump maintenanca, sponsored by Ebasco Services, e
Inc.
I
- s. _
8.
Circulating Mater Purp Intake, Killen Generating Station - 1:10 scale model of puq) intake located at a cooling tower.
Original.
design nodified to increase flow capacity and flow distribution to t.wo vertical shaft pumps, sponsored by Ebasco Services, Inc.
4 9.
Sonerset Power Plant Intale - 1:10.8 scale Inodel of intab-rump-house with three vertical shaft circulating ater pumps.
Origi-nal design modifi.ed to improve flow approach to the traveling scrennn. Vortex activity, persistence, arn! prerotation investi-gated over the range of water levels and purp combinations anti-
' s cipated.
Ecduction of these para:;eters acccuplished by redesign cf sump geometry, sponsored by United Ung1..eers and Coustructors, l
Inc.
i i
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14 4
.. ) -
C.
Pumped Storage Plant -Intake Structures
~
I!ydraulic model studies of upper reservoir intake / outlet structures for pumped storage projects are conducted to optimize the intake configuration, to observe flow patterns and possibic vortox tornation, and'to deternine the head loss coefficients in generating and pumping : nodes.
It is often necessary to rnodel the whole or a part of the upper reservoir so that background circulation is properly sinulated.
Detailed :ncasurements of velocity profiles, stage varsus vortex severity, and loss coefficient versus P.2ynolds nu:.ber are made.
A 1.isting of various model studies in this area conducted at ARL follows.
1.
Bltahn:.-Gilboa Upper Reservoir - 1:75 model including dikes, t.opograpny'of restrvcir and intako structure, remedial measures to a caid strong */crtex recommended, report available, operating satisfactorily in the field, sponcored,by Power Authority of the State of !!ew York.
2.
I:orthfield L'.ountain, Pumped Storage Schtme - 1:45.5 partial redel and 1:100 v.odel of intake and part of upper reservoir, examining i
the flcv 1;atterns, rcport availabic, operating natir factorily in the field, sponsored by Stone r. Webster Engineering Corporation.
3.
Fairfield Pu nped Storage Scheme - 1:70 model of upper reservoir intake, dolcr:aination of flow pat terns, head louses, and mixing, modifications to intake channel and tranuition structure recon-Ine r.d ed, report available, r.ponsored by South Carolina 1:lectric s
and Gas Company.
s\\
4.
Davin Pumped Storage Plant - partial 1:50 and complete 1:360 mo-C':1 of upper reservoir, volccity profiles taensured, - a transition "ection in head race proposed to improve flow patt.crn, rcpcrt availabin, nponr.ored by Allegheny Power Service Coi;poration.
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5.
13ad Creek Purped Stor-age Plant r 1:58 tr.odel of upper reservoir t.nb 1:55 raodel of lower reservoir, raodel testing cc=pleted, re-port bding p& pared to include' observation of flow patterns, j
velocity r.easurements, deternination of intake losses both for pur.pir.g and generation ncides, cronsored by Duke Power Corapany.
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16 P
t l<CFE.RE :CbS
[ T." radlianabban, M..,
and llecker, G.E., " Flow Characteristics of Reactor Recirculati)n Sumps," Presented at t.he IAllR XVIII Congress, Ca613ari, Italy, 1979.
i I
2.
Anwar,'If.O.,17piler, J.A., and Mphlett, M.B.,
" Similarity of Free-Vortex at !!orinontal Inta'ke," Journal of !!ydraulic Research, i
r I Ai!R 16, !!o.
2, 1978.
I s
3.
- Daggett, L.L., and Keulegan, G.!!., _" Similitude Conditions in Free Surface Vortex Fcrnations," Journal of Ilydraulics Division, ASCE, Novenber 1974.
~
4.
- Dcnny, D.F.,
and Young, G.A.J., "The Prevention of Vort. ices and S.*irl at Iatakes," 7th' General Meeting Transactions, I AllR,
(.
1.i cbon, 1957.
l
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5.
Dicr.uc, J.L., "Effect. of Intake Structurc Mcdifications on the
!!ydraulic erfomance of a Mixed Flow Pump," Joint Synposiun i
on Design and Optration'of Fluid Machinery, Colorado State University, June 1978.
r 6.
Durgin, W.W.,
and liccker, G.E., "The Modeling of Vortices at Intake St.ructures," Joint Symposium on Design and Operation of Fluid 1
Machinery, Colorado St ate 11niversity, June 1978.
1 7.
Padmanabhan, !!., "llydraulic Model Investigat. ion of Vortexing and Swirl Within a Beactor Containment Recirculation Sump," Danald i
/
C. Cook I:uc3 ra r Po :cr St.ation, AR1, nel ort I:o. 3 08-78/11178PF.
I i
8.
Padmanabhan, M., " Selection and' Scali,ng of liorizontal Gratings for Vort.ex Suppression," Duke, Po.mr tpcr[*any, ARL Retsor t :o.
,.f L2-7d/M208JF.
4 6
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. - ~., -
.,...a._--n..-
,,. + - ~ - -
=,n-. - -
= -.
,.n.
e d
17
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J 9.
Padmnabhan, M., "Asc,cccment of, Plow Characteristics Within a 1
Reactor Containment Recirculation Sump Using a Scalc !!odel,"
4 McGuire l'ucle)ir Power Station, AEL Report IIo. 29-78/M208JF.
10.
Padmanabhan, M.,
and Vigander, S.,
"Pressurc Drop Due to Flow Through Fine Mesh Screens," Journal of Hydraulics Division, ASCC, August 1978.
i 11.
- Murakani, M.,
et.al., " Flow of Entrained Air in Centrifugal Pumps," 13th IAHR Congresc, Japan, Augtiat 31 to September 5, 1969, Vol. 2, p. 71.
12.
Durgin, W.W.,
1:eale, L.C.,
and Churchill, R.L.,
ilydrodynapics 4j.
of Vertex Suppression in the Reactor Building Sump, Decay Heck.
Rc=cval Syst4n," Three Mile Island 1:uclear Station Unit 2, General Public Utilitics, ABL Report !!o. 46-17/M202FF, 4
February li;77.
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13 Padennathan,*:., " Hydraulic Model Studies of t he Reactor Cont ain-nont Sullding Srp," !!ot th Anna liuclear Power Station, Unit 1, Virginia Electric and Power Company, ARL Report !!o. 123-77/:12 S CCF, July 1977.
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N FIGURE 1 PLAN VIEW OF REACTOR BUILDING NEAR ' CONTAINMENT SUMPS AT.
EL 412 FT, VIRGIL C. SUMMER NUCLEAR STATION
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( 2,3 )
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DR ACKETS REPRESENT b c
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l MAXIMUM VO3 TEX TYPES I
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FIGURE 2 FROUDE NUT.".BER RATIO VERSUS REYNOLDS NUMBER SHOWING MAXIMUM OBSERVED VORTEX TYPES IN THE SUMP EM
e s
V lilCOllEREtJT SURFACE SV/IllL 1
m,-
o dVRFACE Dif4PLE:
2 y
COllEREtJT SV/lRL AT SURFACE V
3 DYE CORE V!!Tli SURFACE O!MPLE; COllEREfJT SVliRL THROUGHOUT WATER CO'LUMtJ l'}h c.n
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VORTEX PtlLLitJG FLOATilJG 4
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FIGURE 3 VORTEX STRENGT11 SCALE FOR INTAKE STUDY gQ l
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