Abstract:
An entrainment-reducing assembly may include a container configured to hold a liquid. A venting arrangement may extend into an upper portion of the container and be configured to direct condensable and non-condensable gases into the container. A suction structure may extend into a lower portion of the container and be configured to carry out an extraction of excess liquid from the container caused by condensed gases. A deflector may be disposed between the suction structure and the venting arrangement within the container. As a result, an entrainment of uncondensed gases during the extraction of the liquid by the suction structure may be reduced or prevented, thereby protecting the pump from cavitation and failure.

Description:
BACKGROUND 
     Field 
       [0001]    The present disclosure relates to the reduction or prevention of the entrainment of gases into the suction of a pump during a loss of coolant accident (LOCA). 
       Description of Related Art 
       [0002]    During a Loss of Coolant Accident (LOCA), the Emergency Core Cooling System (ECCS) must pump water to maintain the reactor core water level and to provide a cooling function to the reactor core. However, this same transient may cause gases to be forced downward into an operating Emergency Core Cooling System (ECCS) suction strainer, resulting in gas entrainment. In particular, during a Loss of Coolant Accident (LOCA), both condensable gases (e.g., steam) and non-condensable gases (e.g., nitrogen (N 2 )) may be directed into a suppression pool, thereby elevating the level of the suppression pool. An Emergency Core Cooling System (ECCS) pump may be used to maintain the suppression pool at an acceptable level by suctioning excess liquid from the suppression pool and supplying the excess liquid to the reactor core. However, the non-condensable gases may become entrained along with the liquid into the suction of the Emergency Core Cooling System (ECCS) pump, thereby causing loss of suction and decreased flow to the reactor core. Furthermore, the presence of non-condensable gases within the Emergency Core Cooling System (ECCS) pump causes cavitation and pump damage, which poses additional safety hazards. 
       SUMMARY 
       [0003]    The present disclosure describes various devices, assemblies, systems, and methods for preventing pumps (e.g., Emergency Core Cooling System (ECCS) pumps) from receiving relatively large quantities of entrained gas in the suction piping, which would cause cavitation and ultimately result in the failure of the pump. The teachings herein also promote the mitigation or prevention of non-condensable gases from reaching the suction strainers within the wetwell. Specially-designed deflector shields or baffles may be arranged between the drywell-to-wetwell vent downcomer and the Emergency Core Cooling System (ECCS) pump suction strainer. By preventing gases from the reaching the Emergency Core Cooling System (ECCS) suction water, the availability of pump operation for the duration of a postulated accident may be increased. 
         [0004]    An entrainment-reducing assembly may include a container configured to hold a liquid. The container may include an upper portion and a lower portion. A venting arrangement may extend into the container. The venting arrangement may be configured to direct gases into the container. A suction structure may extend into the lower portion of the container. The suction structure may be configured to carry out an extraction of the liquid from the container. A deflector may be disposed between the suction structure and the venting arrangement within the container. The deflector may be configured to reduce the entrainment of uncondensed gases during the extraction of the liquid. 
         [0005]    A reactor system may include a first container and a second container. The first container may define a drywell therein. The second container may define a wetwell therein. The second container may include an upper portion and a lower portion. A venting arrangement may connect the drywell to the wetwell. The venting arrangement may include a proximal end extending into the drywell and a distal end extending into the upper portion of the wetwell. A suction structure may extend into the lower portion of the wetwell. A deflector may be disposed between the suction structure and the distal end of the venting arrangement within the second container. 
         [0006]    A method of reducing entrainment may include discharging gases from a venting arrangement into a liquid. The method may additionally include alleviating an elevated level of the liquid resulting from condensing gases by performing an extraction of the liquid with a suction structure. The method may further include shielding the suction structure from the entrainment of uncondensed gases in the liquid with a deflector during the extraction of the liquid. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The various features and advantages of the non-limiting embodiments herein may become more apparent upon review of the detailed description in conjunction with the accompanying drawings. The accompanying drawings are merely provided for illustrative purposes and should not be interpreted to limit the scope of the claims. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. For purposes of clarity, various dimensions of the drawings may have been exaggerated. 
           [0008]      FIG. 1  is a simplified, cross-sectional view of a reactor system according to a non-limiting embodiment. 
           [0009]      FIG. 2  is cross-sectional view of an entrainment-reducing assembly according to a non-limiting embodiment that may be used in the reactor system of  FIG. 1 . 
           [0010]      FIG. 3  is a cross-sectional view of a deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 . 
           [0011]      FIG. 4A  is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 . 
           [0012]      FIG. 4B  is a plan view of the deflector of  FIG. 4A . 
           [0013]      FIG. 5A  is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 . 
           [0014]      FIG. 5B  is a plan view of the deflector of  FIG. 5A . 
           [0015]      FIG. 6A  is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 . 
           [0016]      FIG. 6B  is a plan view of the deflector of  FIG. 6A . 
           [0017]      FIG. 7A  is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 . 
           [0018]      FIG. 7B  is a plan view of the deflector of  FIG. 7A . 
           [0019]      FIG. 8A  is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 . 
           [0020]      FIG. 8B  is a plan view of the deflector of  FIG. 8A . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    It should be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “covering” another element or layer, it may be directly on, connected to, coupled to, or covering the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout the specification. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0022]    It should be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments. 
         [0023]    Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,” “upper,” and the like) may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
         [0024]    The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0025]    Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of example embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments. 
         [0026]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0027]    Various embodiments of the present disclosure relate to devices and assemblies, which when used inside a nuclear reactor (e.g., Boiling Water Reactor (BWR) Mark I or Mark II wetwells (torus)), will mitigate or solve the issue of “loss of suction” to Emergency Core Cooling System (ECCS) pumps due to the entrainment of steam and/or non-condensable gases during a Loss of Coolant Accident (LOCA) in the drywell. Various embodiments of the present disclosure also relate to systems and methods for reducing the entrainment of gases. 
         [0028]    Although the description herein is in the context of a Boiling Water Reactor (BWR), it should be understood that example embodiments are not limited thereto. In addition to the various types of Boiling Water Reactors (BWR), the present disclosure may also be applied to Pressurized Water Reactor (PWR) emergency water sumps with suction strainers. Furthermore, the teachings herein may be applied to non-reactor settings. For instance, the devices, assemblies, systems, and methods may be used in other situations in which a suction is taken from a large reservoir of liquid (e.g., water), whereupon a large injection of non-condensable gases could result in these gases being entrained or swept into the suction pipe, thereby causing the downstream pump to fail. 
         [0029]      FIG. 1  is a simplified, cross-sectional view of a reactor system according to a non-limiting embodiment. Referring to  FIG. 1 , a reactor system  100  includes a first container  102  defining a drywell  104  and a second container  108  defining a wetwell  110 . A reactor pressure vessel  106  is situated within the drywell  104 . A body of liquid  112  (e.g., suppression pool) is disposed within the wetwell  110 . The drywell  104  is connected to the wetwell  110  via a venting arrangement  114 . The details of  FIG. 1  are discussed in connection with the subsequent drawings. 
         [0030]    The present disclosure details the mitigation or prevention of gases from being entrained in the suction of Emergency Core Cooling System (ECCS) pumps. Such mitigation or prevention may improve the safety operation and availability of the Emergency Core Cooling System (ECCS) pumps during a Loss of Coolant Accident (LOCA). In particular, a relatively large Loss of Coolant Accident (LOCA) may force gas into the Emergency Core Cooling System (ECCS) piping. A relatively large gas entrainment may lead to gas entering an Emergency Core Cooling System (ECCS) pump, resulting in pump damage from cavitation and reduced flow (if any flow at all) to the reactor core. Consequently, the ability of the Emergency Core Cooling System (ECCS) pumps to maintain the proper water level in the reactor core may be affected. That being said, the present disclosure is directed to mitigating or preventing the possibility of gas reaching the suction of the Emergency Core Cooling System (ECCS) piping. 
         [0031]    A centrifugal pump is used in the Emergency Core Cooling Systems (ECCS) of Boiling Water Reactors (BWR) and Pressurized Water Reactors (PWR). A centrifugal pump requires a net positive suction head (NPSH) at a given location relative to a reference point as defined by the following equation: 
         [0000]    
       
         
           
             
               
                 
                   NPSH 
                   = 
                   
                     
                       
                         
                           P 
                           o 
                         
                         - 
                         
                           P 
                           v 
                         
                       
                       
                         ρ 
                          
                         
                             
                         
                          
                         g 
                       
                     
                     + 
                     
                       Δ 
                        
                       
                           
                       
                        
                       z 
                     
                     - 
                     
                       h 
                       L 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    wherein P 0  is the pressure acting upon the fluid at the reference point, P ν  is the saturation pressure for the fluid at the current temperature, ρ is the fluid density, g is gravitational acceleration, Δz is the height difference from the current point to the reference point, and h L  is the head loss between the two points. 
         [0032]    If a centrifugal pump does not have a sufficient net positive suction head (NPSH), then low or no flow, pump wear, and in the worst case, seizing of the pump will result. During a Loss of Coolant Accident (LOCA), as will be explained, gases (e.g., non-condensable nitrogen, which was previously used to inert the drywell, and steam, resulting from the flashing flow from a design basis line break) can be forced through the suction strainer in the wetwell (e.g., torus-shaped wetwell) and then into the Emergency Core Cooling System (ECCS) suction header and finally into the pump. 
         [0033]    Depending on the anticipated Emergency Core Cooling System (ECCS) configuration and potential active failures, the ranges of flow 1  in an Emergency Core Cooling System (ECCS) header range from 600 to 30,000 gal/min (5,010 to 417,000 lbs/min). With a ring header diameter of 2 feet, this results in a Reynolds number ranging from 10 5  to 10 7 . Reynolds number 2*  is the ratio of inertial forces within a fluid to its vicious forces and is defined by the following equation: 
         [0000]    
       
         
           
             
               
                 
                   Re 
                   = 
                   
                     QD 
                     vA 
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    wherein Q is the Emergency Core Cooling System (ECCS) flow rate, D is the hydraulic diameter, ν is the kinematic viscosity, and A is the cross-sectional area of the ring header. 
         [0034]    Due to the relatively high Reynolds number, the flow regime is highly turbulent and the inertial force dominates over buoyant forces of gas entrained in the water. Therefore, to remove entrained gases from the water  1  Assuming RCIC ˜600 gpm, HPCS (BWR/5s and 6s)˜7,175 gpm, Low pressure systems that take SP suction: LPCI ˜4 pumps*8400 gpm/pump=33,600 gpm, LPCS ˜2 pumps*8400 gpm/pump=16,800 gpm. 2  Assuming Viscosity at 100° F.=4.579E-4 lb m /ft/s; Density at 100° F.=8.34 lb m /gallon; Kinematic viscosity=4.579E-4/8.34*60=0.003294 gal/ft/min; D=2 ft; D/A=D/(¼ pi D 2 )=4/(pi D)=0.6366 1/ft; Re=Q [gal/min]*193.2 min/gal. the Reynolds number needs to reach a value below 1000, so that buoyancy of the entrained gas can allow phase separation. Even at a Reynolds number of about 100, a wobble occurs that causes bubbles to rise in a spiral or helical path. This velocity of the fluid can occur with expansion of the flow area and is enhanced with flow direction changes. These entrained air bubbles in the pool will take much longer to rise to the surface because of the viscosity of the water. Air bubbles will rise and achieve a terminal velocity governed by Stoke&#39;s law. 
         [0035]      FIG. 2  is cross-sectional view of an entrainment-reducing assembly according to a non-limiting embodiment that may be used in the reactor system of  FIG. 1 . Although the entrainment-reducing assembly of  FIG. 2  is shown in connection with a Boiling Water Reactor (BWR) Mark I suppression pool, it should be understood that example embodiment are not limited thereto. Referring to  FIG. 2 , the entrainment-reducing assembly  200  includes the second container  108 , which defines the wetwell  110  and holds the body of liquid  112  (e.g., suppression pool of water) therein. The venting arrangement  114  connects the drywell  104  ( FIG. 1 ) to the wetwell  110 . The venting arrangement  114  includes a vent pipe  202 , a header  204 , and a plurality of downcomers  206 . A suction structure  212  protrudes into the second container  108  at a position below the surface of the liquid  112 . The suction structure  212  includes a suction pipe  214  and a strainer  216  secured to the suction pipe  214 . The strainer  216  may have a variety of configurations and shapes and is designed to allow the liquid  112  to enter with relative ease while filtering out relatively large-sized debris. 
         [0036]    A deflector  210  is arranged between the suction structure  212  and the venting arrangement  114  to deflect uncondensed gas  208  away from the suction structure  212  so as to reduce or prevent the entrainment of the uncondensed gas  208  with the liquid  112 . A spacing distance between the deflector  210  and the suction structure  212  may be equal to or less than half of a total distance between the venting arrangement  114  and the suction structure  212 . The deflector  210  may be secured to the second container  108  such that the deflector  210  does not directly contact the suction structure  212 . After passing through the strainer  216  and entering the suction pipe  214 , the liquid  112  is directed through the suction line to a pump. Optionally, a gas/liquid separator may be additionally connected to the suction line to separate out any uncondensed gases that may have been entrained with the liquid  112 . The gases may be separated based on density, and the separated gases may be redirected back into the wetwell  110 . 
         [0037]    The common term for a Mark I wetwell is a torus, since the second container  108  defining the wetwell  110  may be in the form of a torus. When the second container  108  is in a form of a torus, eight vent pipes  202  may connect the drywell  104  to the wetwell  110 . In such an example, the header  204  may be in form of a ring within the torus that connects the vent pipes  202 . In addition to the vent pipes  202 , the gas flow from the drywell  104  is further divided by a plurality of downcomers  206  which discharge the gas below the surface of the liquid  112  (e.g., subcooled water). Steam quenchers may be optionally attached to the downcomers  206 . The strainer  216  is positioned so as to remain submerged near the bottom of the second container  108 . The liquid  112  is removed from the wetwell  110  via the suction structure  212  and is conveyed through the suction pipe  214  to the Emergency Core Cooling System (ECCS) pumps. The deflector  210  is positioned between the strainer  216  and the downcomer  206  to reduce or prevent the entrainment of an uncondensed gas  208  into the suction line. Although not shown in the drawings, it should be understood that a suction structure  212  and/or a deflector  210  may be provided for each downcomer  206 . 
         [0038]    The entrainment-reducing assembly  200  will be described in additional detail with regard the following three states: normal operations “Steady State,” a state after a “Large LOCA” in the drywell, and the resulting system transient “Gas to ECCS Pumps” state. 
         [0039]    A “Steady State” assumes that the reactor is at normal operating temperature and pressure and assumed at 100% power. In such a state, the liquid  112  in the wetwell  110  is at a normal level. 
         [0040]    During a “Large LOCA” state, there is a break at rated power, which involves an instantaneous rupture of a steam or recirculation line in the dry well  104 . As a result of the rupture, a shock wave exits with a wave amplitude approaching the reactor operating pressure (e.g., 1000 psig). The attenuated wave enters the venting arrangement  114  and progresses into the wetwell  110 . The high pressure gases (e.g., N 2  and steam) from the drywell  104  are forced downward through the venting arrangement  114 . The high pressure gases exit the downcomer  206  and set off several phenomena, such as pool swell in the torus increasing from the steady state (normal) level to an elevated level, condensation oscillation as the steam chaotically condenses and pool water voids, and forcible downward direction of the gas mixture. 
         [0041]    In a conventional system, if the Emergency Core Cooling System (ECCS) suction strainer is located in the vicinity of the downcomer nozzle, the gas jet can be forced into the suction strainer, thereby introducing a slug of gas into the Emergency Core Cooling System (ECCS) header. If the Emergency Core Cooling System (ECCS) pumps have already been activated, with water flow from the wetwell established, this slug of gas can move into the Emergency Core Cooling System (ECCS) pump, resulting in reduced pump flow, cavitation, and/or pump damage. 
         [0042]    In contrast, in the present disclosure, a deflector  210  is in place as the gas jet is forced towards the strainer  216 . As a result, the deflector  210  deflects the gas flow, thereby allowing for buoyancy effects to permit the gas to separate and rise to the headspace of the wetwell  110 . The strainer  216  under the deflector  210  still maintains suction of the liquid  112  from the wetwell  110 . Additionally, as schematically shown in  FIG. 2 , gas/liquid separator may be used to remove gas that may have become entrained with the liquid  112  into the Emergency Core Cooling System (ECCS) suction line. The gas that is removed from the suction line may be put back into the headspace of the wetwell  110 . 
         [0043]      FIG. 3  is a cross-sectional view of a deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 . Referring to  FIG. 3 , the deflector  210  may include a first surface  302   a  with a first ridge  304   a  and a second surface  302   b  with a first furrow  304   b . When installed in the entrainment-reducing assembly  200 , the first furrow  304   b  will face the strainer  216 , while the first ridge  304   a  will face the downcomer  206 . A first angle α 1  of the first furrow  304   b , as defined by the second surface  302   b , should be of a magnitude that is sufficient to cause the uncondensed gas  208  of the impinged two phase jet hitting the deflector  210  to be deflected upward towards the surface of the wetwell liquid  112  to inhibit or prevent the uncondensed gas  208  from entering the strainer  216  and to allow for a separation when the uncondensed gas  208  reaches the headspace of the wetwell  110 . In a non-limiting embodiment, the first angle α 1  may range from about 155° to 170°. 
         [0044]    The deflector  210  may optionally have a periphery  308  that slopes away from the suction structure  212  so as to form a second ridge  310   a  and a second furrow  310   b , wherein the periphery  308  enhances the deflection of the uncondensed gas  208  away from the suction structure  212 . A second angle α 2  of the second furrow  310   b  may range from 155° to 180°. Although not shown, it should be understood that the second ridge  310   a  and/or the second furrow  310   b  may be curved instead of being angular. 
         [0045]    The deflector  210  may also include a plurality of perforations  306  extending from the first surface  302   a  to the second surface  302   b . The plurality of perforations  306  allow the liquid  112  to flow through the deflector  210 , thereby reducing the differential force across the deflector  210  and allowing the liquid  112  to enter the strainer  216 . The plurality of perforations  306  may be angled inward toward the suction structure  212  and/or the first furrow  304   b  so as to allow entry of the liquid  112  while deflecting the uncondensed gas  208  away from the suction structure  212 . In  FIG. 3 , assuming that A-A is a center line that bisects the deflector  210  and B-B is a line that corresponds to a longitudinal axis of the perforation  306  and intersects A-A to form a third angle α 3 , the third angle α 3  may range from about 45° to 135° (e.g., 60° to 90°). 
         [0046]    The diameter of each of the plurality of perforations  306  may be sized to be about two times the average expected bubble size of the uncondensed gas  208  impinging on the deflector  210 . As noted above, the plurality of perforations  306  are at a third angle α 3  that reduces or prevents bubble entrainment as the two phase jet impinges on the first surface  302   a . The amount of uncondensed gas  208  entrained through the plurality of perforations  306  is a function of perforation diameter, perforation length, and the water flow rate. A method to optimize the diameter of the perforations  306  use the Froude number (Fr): 
         [0000]    
       
         
           
             
               
                 
                   Fr 
                   = 
                   
                     
                       V 
                       L 
                     
                     / 
                     
                       
                         
                           g 
                            
                           
                             ( 
                             
                               
                                 ( 
                                 
                                   
                                     ρ 
                                     l 
                                   
                                   - 
                                   
                                     ρ 
                                     G 
                                   
                                 
                                 ) 
                               
                               
                                 ρ 
                                 l 
                               
                             
                             ) 
                           
                         
                          
                         D 
                       
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
         [0000]    wherein V L  is the liquid velocity in the perforations, g is the acceleration due to gravity, ρ l  is the density of the liquid, ρ G  is the density of the gas, and D is the inside diameter of the perforations. The Froude number (Fr) should be a value that gives the uncondensed gas  208  an adequate opportunity to be deflected and rise toward the headspace of the wetwell  110 . In a non-limiting embodiment, Fr&lt;0.31. Although the perforations  306  have been discussed in the context of a circular hole, it should be understood that example embodiments are not limited thereto. For instance, the perforations  306  may be in the form of other curved shapes or polygonal shapes (e.g., slits) 
         [0047]      FIG. 4A  is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 .  FIG. 4B  is a plan view of the deflector of  FIG. 4A . Referring to  FIGS. 4A-4B , the deflector  210  is in the form of a bent sheet  210   a  including a first ridge  304   a  and a first furrow  304   b . Although not shown, it should be understood that one or more of the features discussed in connection with  FIG. 3  may be applied to this example. 
         [0048]      FIG. 5A  is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 .  FIG. 5B  is a plan view of the deflector of  FIG. 5A . Referring to  FIGS. 5A-5B , the deflector  210  is in the form of a curved shield  210   b  including a convex side  504   a  and a concave side  504   b . Although not shown, it should be understood that one or more of the features discussed in connection with  FIG. 3  may be applied to this example. 
         [0049]      FIG. 6A  is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 .  FIG. 6B  is a plan view of the deflector of  FIG. 6A . Referring to  FIGS. 6A-6B , the deflector  210  is in the form of a curved-type louvered arrangement  210   c  including a first curved portion  600   a , a second curved portion  600   b , and a third curved portion  600   c . The second curved portion  600   b  and a third curved portion  600   c  are provided with an opening in the center thereof such that when arranged with the first curved portion  600   a  into an overlapping louvered arrangement, the first curved portion  600   a  and the second curved portion  600   b  define a first passage  606   a  therebetween, while the second curved portion  600   b  and the third curved portion  600   c  define a second passage  606   b  therebetween. Although not shown, it should be understood that one or more of the features discussed in connection with  FIG. 3  may be applied to this example. 
         [0050]      FIG. 7A  is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 .  FIG. 7B  is a plan view of the deflector of  FIG. 7A . Referring to  FIGS. 7A-7B , the deflector  210  is in the form of a linear-type louvered arrangement  210   d  including a first slat  700   a , a second slat  700   b , and a third slat  700   c . When arranged in an overlapping louvered arrangement, the first slat  700   a  and the second slat  700   b  define a first slit  706   a  therebetween, while the second slat  700   b  and the third slat  700   c  define a second slit  706   b  therebetween. Although not shown, it should be understood that one or more of the features discussed in connection with  FIG. 3  may be applied to this example. 
         [0051]      FIG. 8A  is a perspective view of another deflector according to a non-limiting embodiment that may be used in the entrainment-reducing assembly of  FIG. 2 .  FIG. 8B  is a plan view of the deflector of  FIG. 8A . Referring to  FIGS. 8A-8B , the deflector  210  is in the form of a radially-configured corrugated sheet  210   e  including a plurality of alternating radially-oriented ridges  804   a  and radially-oriented furrows  804   b  that expand outward radially from a point of common convergence  802 . Although not shown, it should be understood that one or more of the features discussed in connection with  FIG. 3  may be applied to this example. 
         [0052]    While a number of example embodiments have been disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.