WO2014189968A2

WO2014189968A2 - High capacity suction strainer for an emergency core cooling system in a nuclear power plant

Info

Publication number: WO2014189968A2
Application number: PCT/US2014/038838
Authority: WO
Inventors: Edward J. Wolbert; Nathan R. MILLER; Felipe M. VAZQUEZ
Original assignee: Transco Products Inc.
Priority date: 2013-05-20
Filing date: 2014-05-20
Publication date: 2014-11-27
Also published as: WO2014189968A3

Abstract

A high capacity suction strainer (100) for a nuclear reactor has a frame (104), a flow-through plenum (108), and a filter array (112). The flow-through plenum is mechanically mounted to the frame and has a plurality of inlets (116) and an outlet (120). The filter array is also mechanically mounted to the frame and has a plurality of filter groupings (124) in fluid communication with the inlet (116) on the plenum (108).

Description

HIGH CAPACITY SUCTION STRAINER FOR AN EMERGENCY CORE

COOLING SYSTEM IN A NUCLEAR POWER PLANT

DESCRIPTION

TECHNICAL FIELD

[0001] The invention relates to a suction strainer for use on suction lines. More particularly, the invention relates to a suction strainer for use in an emergency core cooling system of a nuclear power plant.

BACKGROUND OF THE FNVENTION

[0002] All nuclear power plants have some form of emergency core cooling system (ECCS) in the event that normal operation is lost and a major break occurs in the reactor cooling system. There are two phases to most ECCS - The injection phase when the pumps suction water from a large tank and pump that water into the reactor cooling system or reactor, and the recirculation phase when the pumps take water from the containment sump after all of the water has been pumped into the containment.

[0003] An ECCS has one major function and that is to provide makeup water to cool the reactor in the event of a loss of coolant from the reactor cooling system. This cooling is needed to remove the decay heat still in the reactor's fuel after the reactor is shutdown. ECCS in some plants may have a second major function and that is to provide chemicals to the reactor and reactor cooling system to ensure the reactor does not produce power.

[0004] The major components of an ECCS are water supplies (tanks), pumps, interconnecting piping, high pressure pumps, low pressure pumps, water storage tanks, accumulators, and a containment sump used to circulate the water through the reactor once the storage tanks are empty.

[0005] In a nuclear reactor, a suction strainer is located in the containment area and its purpose is to keep loose materials and debris, such as insulation, from getting to the suction of the ECCS pumps during the recirculation phase. The pumps perform an important and vital function at nuclear power plants. Again, a purpose of the strainers is to protect the downstream components, such as pumps and nuclear fuel assemblies, from being adversely affected by such debris. Suction strainers, by their nature, have a tendency to build up debris layers. In use, as water is circulated through the strainer, solid debris builds on the outer surfaces of the strainer. The recirculation continues until the ECCS is no longer needed in cold shutdown. [0006] Structural considerations, hydrodynamic loading, and space constraints limit the size and shape of suction strainers in nuclear containment buildings.

[0007] One existing suction strainer design utilizes nested tubes which are produced from a perforated metal sheet. Ends of the sheet are butted together and welded to form a tube. In the nuclear power industry welding is highly regulated. It is, therefore, advantageous to reduce or eliminate welding in any nuclear application.

[0008] The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior strainers of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which:

[0010] FIG. 1 is isometric view of a strainer of the present invention;

[0011] FIG. 2 is a partially exploded view of the strainer of FIG. 1;

[0012] FIG. 3 is a top view of the strainer of FIG. 2;

[0013] FIG. 4 is a top view of a strainer plenum;

[0014] FIG. 5 is a rear isometric view of a first bottom grate;

[0015] FIG. 6 is a plan view of the first bottom grate of FIG. 5;

[0016] FIG. 7 is an isometric view of a third top grate;

[0017] FIG. 8 is a plan view of the third top grate of FIG. 7;

[0018] FIG. 9 is an exploded view of a strainer of the present invention;

[0019] FIG. 10 is a plan view of a template plate;

[0020] FIG. 11 is a side view of a strainer of the present invention;

[0021] FIG. 12 is a perspective view of an embodiment of a strainer of the present invention;

[0022] FIG. 13 is

[0023] FIG. 14 is

[0024] FIG. 15 is

[0025] FIG. 16 is

present invention;

[0026] FIG. 17 is a perspective view of the filter grouping of FIG. 16; [0027] FIG. 18 is a perspective view of the filter grouping of FIG. 16;

[0028] FIG. 19 is a perspective view of the filter grouping of FIG. 16;

[0029] FIG. 20 is a perspective view of the strainer of FIG. 12 in experimental submerged in water test use;

[0030] FIG. 21 is a perspective view of the strainer of FIG. 12 in experimental test use as debris begins to build on nested tubes of filter groupings of the strainer;

[0031] FIG. 22 is a perspective view of the strainer of FIG. 12 in experimental test use as debris continues to build on nested tubes of filter groupings of the strainer;

[0032] FIG. 23 is a perspective view of the strainer of FIG. 12 in experimental test use, primarily showing a top plate of a grouping and inlets to the nested tubes with debris build up on an inner wall of an inner tube of the nested tubes;

[0033] FIG. 24 is a partial plan view of a perforated sheet used to form a tube used in the present invention;

[0034] FIG. 25 is a partial cross-sectional view of the sheet of FIG. 24;

[0035] FIG. 26 is a partial cross-sectional view of a tube formed from a perforated sheet as used in the present invention

[0036] FIG. 27 is a perspective view of a prior art tube used in a prior art strainer;

[0037] FIG. 28 is a perspective view of a prior art tube used in a prior art strainer;

[0038] FIG. 29 is a schematic of a prior art tube showing a flow angle entering an interstitial area;

[0039] FIG. 30 is schematic of a nested tube arrangement of the present invention showing a flow angle entering an interstitial area;

[0040] FIG. 31 is schematic of an alternative nested tube arrangement of the present invention showing a flow angle entering an interstitial area;

[0041] FIG. 32 is schematic of an alternative nested tube arrangement of the present invention showing a flow angle entering an interstitial area;

[0042] FIG. 33 is an exploded isometric view of a suction strainer according to an embodiment of the present invention; and

[0043] FIG. 34 is a partial isometric sectional view showing the suction strainer of FIG. 33 with a portion of an additional filter assembly magnified for clarity. DETAILED DESCRIPTION

[0044] While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated.

[0045] An embodiment of the present invention will now be described in which, at least:

Reference number 1 is a template plate;

Reference number 2 is a bottom grate;

Reference number 3 is a bottom grate;

Reference number 4 is an aperture in the second bottom grate for receiving a fastener and a centering means;

Reference number 5 is an outer perforated conduit;

Reference number 6 is an inner perforated conduit;

Reference number 7 is a first top grate;

Reference number 8 is a second top grate;

Reference number 9 is a third top grate; and

Reference number 10 is a reinforcement cross member of a frame.

[0046] Referring to the figures, a high capacity suction strainer 100 for an emergency core cooling system (ECCS) in a nuclear power plant comprises a frame 104, a flow-through plenum 108, and a filter array 112. In order to increase filter surface area within a given cube volume, filter tubes 5,6 are nested tubes inside the one another with alternating "dirty" water and "clean" water flow paths. The strainer of the present invention may be used with pressurized water reactors, boiling water reactors, or generally any nuclear power plant system comprising an ECCS. The invention also absolutely minimizes (if not entirely eliminates) welding using, instead, mechanical fasteners. Thus, it is very economical to produce and very easy to assemble.

[0047] The flow-through plenum 108 is mechanically mounted to the frame and comprises a plurality of inlets 116 located on a template plate 1 and an outlet 120. The plenum 108 is generally an enclosed housing.

[0048] The filter array 112 is also mechanically mounted to the frame 104 and comprises a plurality of filter groupings 124, each in fluid communication with an inlet 116 on the plenum 108. The filter groupings 124 are attached to the flow-through plenum 108 by a mechanical fastener.

[0049] Each filter grouping 124 comprises a plurality of nested tubes 128. Each nested tube 128 has an inner perforated tube 6 disposed within a corresponding outer perforated tube 5 such that an interstitial space 132 is created between the inner and outer perforated tubes 6,5. The nested tubes 128 are arranged in a plurality of columns and rows and extend outwardly from the plenum 108 such that each nested tube 128 has an outlet forming a fluid communication between each interstitial space 132 and an inlet 116 on the plenum 108.

[0050] Each filter grouping 124 also has a flow-through to top plate 136. Each top plate 136 has a plurality of top grates 7,8,9 at a proximal end of the nested tubes 128.

[0051] A first top grate 7 has a plurality of first apertures 140 corresponding in size and shape to the outer circumference of each outer perforated tube 5 wherein a proximal end of each outer perforated tube is inserted within and supported by a corresponding first aperture 140. One or more second apertures 144 are located between and about the first apertures 140 to allow a fluid flow therethrough.

[0052] A second top grate 8 has a plurality of first apertures 148 aligned with the first apertures 140 in the first top grate 8. Each such aperture 148 has a smaller cross-sectional area than an opening at the proximal end of the outer perforated tube 5 such that the interstitial space 132 between the inner and outer tubes 6,5 is at least substantially sealed against a surface of the second grate 8 and such that a proximal end of each inner perforated tube 6 is inserted within and supported by a corresponding first aperture 148. One or more second apertures 152 are aligned with the second apertures 144 on the first top grate 7 and located between and about the first apertures 148 to allow a fluid flow therethrough.

[0053] A third top grate 9 has a plurality of first apertures 156 aligned with the first apertures 148 in the second top grate 8. Each such aperture 156 has a smaller cross-sectional area than an opening at the proximal end of the inner perforated tube 6 such that the proximal end of the inner perforated tube 6 abuts a surface of the third top grate 9 forming the nested tube inlet. One or more second apertures 160 are aligned with the second apertures 152 on the second top grate 8 and located between and about the first apertures 156 to allow a fluid flow therethrough.

[0054] The first top grate 7 and the third top grate 9 sandwich the second top grate 8 therebetween. Surfaces of the first top grate 7 and the third top grate 9 engage opposite surfaces of the second top grate 8. The first top grate 7, the second top grate 8, and the third top grate 9 are mechanically attached to the frame 104.

[0055] Each filter grouping 124 also has a flow-through bottom plate 164. Each bottom plate 164 has a plurality of bottom grates 2,3 at a distal end of the nested tubes 128. The bottom plates 164 are adapted to act as outlets feeding a filtered fiuid to the inlets 116 on the flow-through plenum 108.

[0056] A first bottom grate 3 has a plurality of first apertures 168 corresponding in size and shape to the outer circumference of each outer perforated tube 5 wherein a distal end of each outer perforated tube 5 is inserted within and supported by a corresponding first aperture 168.

[0057] A second bottom grate 2 has a plurality of first apertures 172. Each such aperture 172 is aligned with a corresponding interstitial space 132 between an inner perforated tube 6 and an outer perforated tube 5. The second bottom grate 2 also has a plurality of second apertures 176. Each second aperture 176 is aligned with an opening at a distal end of a corresponding inner perforated tube 6, which forms the nested tube 128 outlet aligned with an inlet on the plenum 108. A central webbing 180 about each second aperture 176 substantially seals the opening at the distal end of the corresponding inner perforated tube 6. A

mechanical fastener 180 passes through each second aperture 176 and engages the distal end of the corresponding inner perforated tube 6 to maintain the corresponding inner perforated tube 6 in a desired position in the nested tube 124. Typically, a washer or other substantially donut-shaped member is attached to the mechanical fastener and is located within the inner perforated tube 6 to center the inner perforated tube 6.

[0058] The first bottom grate 3 and a surface of the plenum 108 sandwich the second bottom grate 2 therebetween such that surfaces of the first bottom grate 3 and the plenum 108 engage opposite surfaces of the second bottom grate 2. The first bottom grate 3 and the second bottom grate 2 are mechanically attached to the frame 104.

[0059] Accordingly, the interstitial spaces 132 between the inner perforated tubes 6 and the outer perforated tubes 5 are adapted to receive a filtered fluid flow as a contaminated fluid passes from outer surfaces to inner surfaces of the outer perforated tubes 5 and from inner surfaces to outer surfaces of the inner perforated tubes 6.

[0060] Each top plate 136 is mechanically joined to a corresponding bottom plate 164 by a tie rod. Each top plate 136 is separated from the corresponding bottom plate 164 by the plurality of nested tubes 124. Each top plate 136 is further mechanically joined to a corresponding bottom plate 164 by a pair of cross members 10, which are joined to the top plate 136 by a mechanical fastener and to the corresponding bottom plate 164 at an opposing end by a mechanical fastener.

[0061] The template plate 1 forms the plurality of inlets on the plenum 108. Accordingly, the template plate 1 has a plurality of openings. Each opening is aligned with a filter grouping to provide the inlets to the plenum. The template plate is mechanically attached to the plenum 108, to each of the groupings 124 and the frame 104.

[0062] As illustrated in FIGS. 24-26, the tubes are generally produced from a stainless steel 184 strip that is rolled, perforated, and cut in a continuous process. Opposing edges of the perforated strip are brought into engagement and joined by a mechanical seam 186. The opposing edges are brought together by twisting or rotating a terminal end of the strip such that the strip forms a tube having a helical seam, one edge a receiving a portion of the opposing edge into a receiver to form the mechanical seam.

[0063] The perforations 188 are formed in a fluted fashion. Longitudinal recesses are formed on a surface of the metal sheet 184 forming slotted opposing parallel openings 192 separated by a segment 194 of the metal sheet 184. It should be understood that the segment 194 is recessed relative to an outer surface of the tubes 5,6. When viewed from an inner surface of the tubes 5,6, the segments 194 will appear as protrusions or extensions. This will be explained in more detail below. The structure of the tubes with mechanical seam lends itself to repetition and changes in length and the tube diameter as will be understood from the description below taken in combination with structure so far explained.

[0064] Again, a tube is formed by twisting the sheet 184 to form a helical orientation and draw the opposing edges together. The opposing edges have complimentary mechanically formed seaming members which are interlocked to form the mechanical seam 186. The resulting mechanical seam 186 forms a helical structure winding about a length of the tubes. Among other things, the mechanical seam 186 eliminates the need for welding of the tube in order for it to achieve structural integrity, which is an improvement over prior designs.

[0065] As can be seen on, for example, FIGS. 13-18, the openings 192 create a double helix pattern in the finished nested tubes. A first helix pattern of the openings is parallel to the seam 186. A second helix pattern of the openings 192 extends generally transverse to the seam 186 in an opposite direction. In one embodiment, the first helix pattern is a right- handed helix, and the second helix pattern is a left-handed helix. It should be understood that the patterns 300,302 can be reversed without departing from the spirit of the invention. [0066] A pitch of the first helix pattern is generally substantially less than a pitch of the second helix pattern. In one embodiment, the pitch of the second helix pattern is 6 times greater than the pitch of the first helix pattern. In another embodiment, the pitch of the second helix pattern is 7 times greater than the pitch of the first helix pattern. In one preferred embodiment, the outer tube 5 of the nested tubes has a second helix pattern having a pitch 6 times greater than a pitch of the first helix pattern, and an inner tube 6 of the nested tubes has a second helix pattern having a pitch 7 times greater than a pitch of the first helix pattern. The ratio of the respective pitches of the second helix pattern and the first helix pattern may be greater than 3, between about 3 to about 10, between about 4 to about 8, between about 6 to about 8, or any range or combination of ranges therein.

[0067] An improvement over the prior art nested tubes is believed to be the flow angle of the fluid entering the tubes 5,6. In a prior art configuration shown in FIGS. 27-29, tubes 200 are formed from a metal sheet having opposing edge portions welded to form a longitudinal welded seam 204 which forms a tube. The metal sheet is stamped or pierced with round apertures 208 to form a perforated tube 200. A fluid flow entry angle 210 is typically about 90 degrees in this configuration, as shown in FIG. 29. It is believed that an undesired turbulent flow is established at knife edges of each aperture.

[0068] As illustrated in FIG. 30, a fluid flow 214 enters the interstitial area 132 of the nested tubes at an angle less than 90 degrees, rather than a 90 degree angle as experienced in the prior art tubes. This results in a reduction or elimination of turbulent flow at the knife edge of the openings.

[0069] As shown in FIG. 30, fluid flow 214 enters the interstitial area 132 through the outer tube 5 via negative, depressed, or recessed portions 194 from an outer space surrounding the tube 5 to the interstitial area 132 within an interior space of the tube 5.

Because the openings 192 are slotted, angled greater than 0 degrees relative to the recessed portions 194, generally perpendicular to an outer cylindrical surface of the tube 5, insulation fibers, which can be long and thin in structure, are less likely to enter the interstitial area 132 and/or clog or otherwise obstruct flow at the openings 192 than if the openings were stamped apertures parallel to the cylindrical outer surface of the tube as is prevalent in the prior art. Thus, the slotted openings 192 may have an entrance to the interstitial area 132 which is radially outwardly of the recessed portion 194 and radially inwardly of a radially outermost surface of the tube 5 as shown on FIG. 30. [0070] As also shown in FIG. 30, fluid flow 214 enters the interstitial area 132 through the inner tube 6 via positive, extended, or protruding segments 194 from an interior space of the inner tube 6 to the interstitial area 132. Similar to the openings 194 on the outer tube 5, the openings 192 on the inner tube 6 are slotted, angled greater than 0 degrees relative to the segments 194 between the slots, generally perpendicular to an inner cylindrical surface of the tube 6. Thus, the slotted openings 192 may have an entrance to the interstitial area 132 which is radially outwardly of the segment 194 and which extends radially inwardly from a cylindrical surface of the tube 6 into the interior space of the tube 6 as shown on FIG. 30.

[0071] The orientations of the openings 192 described above on the tubes 5,6 may be reversed. Here, the outer tube 5 has slotted openings extending radially outwardly from the cylindrical surface of the tube 5 and the segments 194 are protruding radially outwardly on the cylindrical surface. The inner tube 6 has slotted openings extending radially outwardly characterized by segments 194 also protruding radially outwardly from the cylindrical surface. See FIG. 31.

[0072] Alternatively, the orientations can be mixed such that one tube has radially outwardly projecting segments 194, and the other tube has radially inwardly projecting segments 194. See FIG. 32.

[0073] Alternatively still, the orientations of the projecting segments 194 can be mixed on each tube 5,6. In this embodiment, a single tube can exhibit both radially inwardly and outwardly projecting segments 194.

[0074] The nested tubes 5,6 with radially extending slotted openings provides at least the following improvements over prior designs. By-pass is reduced. By-pass is amount of material that passes through the nested tube medium and beyond the suction strainer, i.e. not filtered. Additionally, head loss is reduced. Head loss, in this case, is a pressure drop across the filter medium.

[0075] Now referring to FIGS. 33 and 34, an embodiment of a suction strainer 100 includes additional filter assemblies. These assemblies are external to the stainless steel filter groupings or cartridges 124 and are generally positioned between the filter groupings and the plenum 108. More precisely, the additional filter assemblies are sandwiched between the generally are position bottom plates 164 of each filter grouping 124 and the template plate 1 which defines the inlets 116 to the plenum 108. Accordingly, the number of additional filter assemblies generally equals the number of inlets 116 on the plenum 108 that are fed by a filter grouping 124. Otherwise, the suction strainer 100 of this embodiment may be identical to any of the previously described embodiments, adopting any or all of their respective structural characteristics, as one of ordinary skill in the art would readily understand.

[0076] The additional filter assemblies generally include one or more divider plates or filter trays 400 which sit within the inlets 116 to the plenum 108 and are attachable to either bottom plates 164 of the filter groupings 124 or the template plate 1. Each filter tray 400 includes a recessed portion 404 which as has perforated the surface 406. The recessed portions 404 extend outwardly from the bottom plate 164 and inwardly relative to the inlets 116. The filter trays are preferably produced from a stainless steel.

[0077] The additional filter assemblies further include one or more mesh pads 408. The number of mesh pads 408 generally corresponds to the number of filter trays 400. The mesh pads 408 are adapted, as in sized and shaped, to fit within the recesses 404 of the filter trays 400. The mesh in the pads 408 is preferably produced from stainless steel and is adapted to allow liquid to pass therethrough while straining large scale particulates such as insulation and the like.

[0078] Owing to the construction and placement of the additional filter assemblies, no portion of the mesh pads 408 enters the interstitial spaces 132 of the nested tubes 5,6 of the filter groupings 124.

[0079] The terms "first," "second," "upper," "lower," "top," "bottom," etc., when used, are for illustrative purposes relative to other elements only and are not intended to limit the embodiments in any way. The term "plurality" as used herein is intended to indicate any number greater than one, either disjunctively or conjunctively as necessary, up to an infinite number. The terms "joined," "attached," and/or "connected" as used herein are intended to put or bring two elements together so as to form a unit, and any number of elements, devices, fasteners, etc. may be provided between the joined or connected elements unless otherwise specified by the use of the term "directly" and/or supported by the drawings. The pitch of a helix is the width of one complete helix turn, measured parallel to the axis of the helix. If the movement away from the observer is clockwise, then the helix is right-handed. Most hardware screw threads (a screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force) are right-handed helices. If the movement is in the anti-clockwise direction, then a left-handed helix is being observed.

[0080] While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention, and the scope of protection is only limited by the scope of the accompanying Claims.

Claims

CLAIMS What is claimed is:

1. A high capacity suction strainer for an emergency core cooling system in a nuclear power plant comprising:

a flow-through plenum comprising an inlet and an outlet;

a filter array comprising a plurality of a plurality of nested tubes, each comprising an inner perforated tube disposed within a corresponding outer perforated tube such that an interstitial space is created between the inner and outer perforated tubes, the inner and outer tubes comprising a radially extending slot adjacent to a radially extending segment of the inner and outer tubes wherein the radially extending slot and the radially extending segment extend in an identical radial direction relative to a center axis of the inner and outer tubes; and

a filter assembly external to the filter array located between the filter array and the inlet of the plenum.

2. A high capacity suction strainer for an emergency core cooling system in a nuclear power plant comprising:

a flow-through plenum comprising an inlet and an outlet;

a filter array comprising a plurality of a plurality of nested tubes, each comprising an inner perforated tube disposed within a corresponding outer perforated tube such that an interstitial space is created between the inner and outer perforated tubes, the inner and outer tubes comprising a helical mechanically-formed seam extending a length of each tube; and a filter assembly external to the interstitial spaces and located between the filter array and the inlet of the plenum.

3. A high capacity suction strainer for an emergency core cooling system in a nuclear power plant comprising:

a flow-through plenum comprising an inlet and an outlet;

a filter array comprising a plurality of a plurality of nested tubes, each comprising an inner perforated tube disposed within a corresponding outer perforated tube such that an interstitial space is created between the inner and outer perforated tubes, the inner and outer tubes comprising a plurality of radially extending slots adjacent to a corresponding plurality of radially extending segments of the inner and outer tubes, the plurality of radially extending slots forming a first helical pattern having a first orientation about a surface of the inner and outer tubes and a second helical pattern having a second orientation opposite the first orientation about the surface of the inner and outer tubes; and

a filter assembly external to the interstitial spaces and located between the filter array and the inlet of the plenum.

4. A high capacity suction strainer for an emergency core cooling system in a nuclear power plant comprising:

a flow-through plenum comprising an inlet and an outlet; and

a filter array comprising a plurality of a plurality of nested tubes, each comprising an inner perforated tube disposed within a corresponding outer perforated tube such that an interstitial space is created between the inner and outer perforated tubes, the inner and outer tubes comprising a radially extending slot adjacent to a radially extending segment of the inner and outer tubes wherein the radially extending slot and the radially extending segment extend in an identical radial direction relative to a center axis of the inner and outer tubes; a filter assembly external to the interstitial spaces and located between the filter array and the inlet of the plenum.

5. The high capacity suction strainer of any preceding claim wherein the nested tubes are arranged in a plurality of columns and rows and extend outwardly from the plenum such that each nested tube has a nested tube outlet forming a fluid communication between each interstitial space and an inlet on the plenum, wherein the filter array forms a filter grouping and the high capacity suction strainer comprises a plurality of filter groupings.

6. The high capacity suction strainer of any preceding claim wherein the filter assembly comprises:

a filter element sandwiched between a flow-through bottom plate of at least one of the filter groupings and the inlet of the plenum.

7. The high capacity suction strainer of Claim 6 wherein the filter assembly comprises: a filter tray supporting the filter element in the suction strainer.

8. The high capacity suction strainer of Claim 7 wherein the filter tray has a perforated surface adjacent the filter element for allowing fluid to pass therethrough and into the plenum.

9. The high capacity suction strainer of Claim 8 wherein the filter tray has a recessed portion sized and shaped to receive the filter element therein.

10. The high capacity suction strainer of Claim 9 wherein the recessed portion extends inward into the inlet of the plenum.

11. The high capacity suction strainer of Claim 10 wherein the filter element is a mesh.

12. The high capacity suction strainer of Claim 11 wherein the mesh is a stainless steel mesh.

13. The high capacity suction strainer of Claim 12 wherein the filter tray is fastened to a portion of the plenum.

14. The high capacity suction strainer of any preceding claim wherein each filter grouping comprises:

a flow-through top plate.

15. The high capacity suction strainer of Claim 14 wherein each filter grouping comprises:

plurality of top grates located at a proximal end of the nested tubes.

16. The high capacity suction strainer of Claim 15 wherein each flow-through top plate comprises:

a plurality of top grates located at a proximal end of the nested tubes.

17. The high capacity suction strainer of Claim 16 wherein each flow-through bottom plate comprises:

a plurality of bottom grates located at a distal end of the nested tubes.

18. The high capacity suction strainer of Claim 17 wherein the plurality of top grates comprises:

a first top grate comprising a plurality of first apertures corresponding in size and shape to the outer circumference of each outer perforated tube wherein a proximal end of each outer perforated tube is inserted within and supported by a corresponding first aperture and a plurality of second apertures located between and about the first apertures to allow a fluid flow therethrough.

19. The high capacity suction strainer of Claim 18 wherein the plurality of top grates comprises:

a second top grate comprising a plurality of first apertures aligned with the first apertures in the first top grate, each having a smaller cross-sectional area than an opening at the proximal end of the outer perforated tube such that the interstitial space between the inner and outer tubes is at least substantially sealed against a surface of the second grate and such that a proximal end of each inner perforated tube is inserted within and supported by a corresponding first aperture, and a plurality of second apertures aligned with the second apertures on the first top grate and located between and about the first apertures to allow a fluid flow therethrough.

20. The high capacity suction strainer of Claim 19 wherein the plurality of top grates comprises:

a third top grate comprising a plurality of first apertures aligned with the first apertures in the second top grate, each having a smaller cross-sectional area than an opening at the proximal end of the inner perforated tube such that the proximal end of the inner perforated tube abuts a surface of the third top grate forming the nested tube inlet, and a plurality of second apertures aligned with the second apertures on the second top grate and located between and about the first apertures to allow a fluid flow therethrough.

21. The high capacity suction strainer of Claim 20 wherein the plurality of bottom grates comprises:

a first bottom grate comprising a plurality of first apertures corresponding in size and shape to the outer circumference of each outer perforated tube wherein a distal end of each outer perforated tube is inserted within and supported by a corresponding first aperture.

22. The high capacity suction strainer of Claim 21 wherein the plurality of bottom grates comprises:

a second bottom grate comprising a plurality of first apertures, each aligned with a corresponding interstitial space between an inner perforated tube and an outer perforated tube, a plurality of second apertures, each aligned with an opening at a distal end of a corresponding inner perforated tube forming the nested tube outlet aligned with an inlet on the plenum, a central webbing about each second aperture substantially sealing the opening at the distal end of the corresponding inner perforated tube, and a plurality of mechanical fasteners, each fastener passing through a corresponding second aperture and engaging the distal end of the corresponding inner perforated tube to maintain the corresponding inner perforated tube in a desired position in the nested tube.

23. The high capacity suction strainer of Claim 22 wherein the first top grate and the third top grate sandwich the second top grate therebetween such that surfaces of the first top grate and the third top grate engage opposite surfaces of the second top grate.

24. The high capacity suction strainer of Claim 23 wherein the first top grate, the second top grate, and the third top grate are mechanically attached to the frame.

25. The high capacity suction strainer of Claim 24 wherein the first bottom grate and a surface of the plenum sandwich the second bottom grate therebetween such that surfaces of the first bottom grate and the plenum engage opposite surfaces of the second bottom grate.

26. The high capacity suction strainer of Claim 25 wherein the first bottom grate and the second bottom grate are mechanically attached to the frame.

27. The high capacity suction strainer of Claim 26 wherein each top plate is mechanically joined to a corresponding bottom plate by a tie rod and each top plate is separated from the corresponding bottom plate by the plurality of nested tubes.

28. The high capacity suction strainer of Claim 27 wherein each top plate is mechanically joined to a corresponding bottom plate by a pair of cross members joined to the top plate by a mechanical fastener and to the corresponding bottom plate at an opposing end by a mechanical fastener.

29. The high capacity suction strainer of Claim 28 wherein each filter grouping is attached to the flow-through plenum by a mechanical fastener.

30. The high capacity suction strainer of Claim 29 wherein each top plate is mechanically joined to a corresponding bottom plate by a tie rod and each top plate is separated from the corresponding bottom plate by the plurality of nested tubes.

31. The high capacity suction strainer of Claim 30 wherein the interstitial spaces between the inner perforated tubes and the outer perforated tubes are adapted to receive a filtered fiuid flow as a contaminated fluid passes from outer surfaces to inner surfaces of the outer perforated tubes and from inner surfaces to outer surfaces of the inner perforated tubes.

32. The high capacity suction strainer of Claim 31 wherein the bottom plates are adapted to act as outlets feeding a filtered fluid to the inlets on the flow-through plenum.

33. A high capacity suction strainer for an emergency core cooling system in a nuclear power plant as shown and described.

34. A filter array for a high capacity suction strainer for an emergency core cooling system in a nuclear power plant as shown and described.

35. A filter grouping for a high capacity suction strainer for an emergency core cooling system in a nuclear power plant as shown and described.

36. A high capacity suction strainer for an emergency core cooling system in a nuclear power plant comprising:

a frame;

a flow-through plenum mechanically mounted to the frame and comprising a plurality of inlets and an outlet; and

a filter array also mechanically mounted to the frame and comprising a plurality of filter groupings, each in fluid communication with a corresponding inlet on the plenum.

37. The high capacity suction strainer of Claim 36 wherein each filter grouping comprises:

a plurality of nested tubes, each comprising an inner perforated tube disposed within a corresponding outer perforated tube such that an interstitial space is created between the inner and outer perforated tubes.

38. The high capacity suction strainer of Claim 37 wherein the nested tubes are arranged in a plurality of columns and rows and extend outwardly from the plenum such that each nested tube has a nested tube outlet forming a fiuid communication between each interstitial space and an inlet on the plenum.

39. The high capacity suction strainer of Claim 38 wherein each filter grouping comprises:

a flow-through top plate.

40. The high capacity suction strainer of Claim 39 wherein each filter grouping comprises:

a flow-through bottom plate.

41. The high capacity suction strainer of Claim 40 wherein each filter grouping comprises:

plurality of top grates located at a proximal end of the nested tubes.

42. The high capacity suction strainer of Claim 41 wherein each flow-through top plate comprises:

a plurality of top grates located at a proximal end of the nested tubes.

43. The high capacity suction strainer of Claim 42 wherein each flow-through bottom plate comprises:

a plurality of bottom grates located at a distal end of the nested tubes.

44. The high capacity suction strainer of Claim 43 wherein the plurality of top grates comprises:

45. The high capacity suction strainer of Claim 44 wherein the plurality of top grates comprises:

46. The high capacity suction strainer of Claim 45 wherein the plurality of top grates comprises:

47. The high capacity suction strainer of Claim 46 wherein the plurality of bottom grates comprises:

48. The high capacity suction strainer of Claim 47 wherein the plurality of bottom grates comprises:

49. The high capacity suction strainer of Claim 48 wherein the first top grate and the third top grate sandwich the second top grate therebetween such that surfaces of the first top grate and the third top grate engage opposite surfaces of the second top grate.

50. The high capacity suction strainer of Claim 49 wherein the first top grate, the second top grate, and the third top grate are mechanically attached to the frame.

51. The high capacity suction strainer of Claim 50 wherein the first bottom grate and a surface of the plenum sandwich the second bottom grate therebetween such that surfaces of the first bottom grate and the plenum engage opposite surfaces of the second bottom grate.

52. The high capacity suction strainer of Claim 51 wherein the first bottom grate and the second bottom grate are mechanically attached to the frame.

53. The high capacity suction strainer of Claim 52 wherein each top plate is mechanically joined to a corresponding bottom plate by a tie rod and each top plate is separated from the corresponding bottom plate by the plurality of nested tubes.

54. The high capacity suction strainer of Claim 53 wherein each top plate is mechanically joined to a corresponding bottom plate by a pair of cross members joined to the top plate by a mechanical fastener and to the corresponding bottom plate at an opposing end by a mechanical fastener.

55. The high capacity suction strainer of Claim 54 wherein each filter grouping is attached to the flow-through plenum by a mechanical fastener.

56. The high capacity suction strainer of Claim 55 wherein each top plate is mechanically joined to a corresponding bottom plate by a tie rod and each top plate is separated from the corresponding bottom plate by the plurality of nested tubes.

57. The high capacity suction strainer of Claim 48 wherein the interstitial spaces between the inner perforated tubes and the outer perforated tubes are adapted to receive a filtered fluid flow as a contaminated fluid passes from outer surfaces to inner surfaces of the outer perforated tubes and from inner surfaces to outer surfaces of the inner perforated tubes.

58. The high capacity suction strainer of Claim 57 wherein the bottom plates are adapted to act as outlets feeding a filtered fluid to the inlets on the flow-through plenum.

59. A. high capacity suction strainer for an emergency core cooling system in a nuclear power plant comprising: a frame;

a flow-through plenum mounted to the frame and comprising a plurality of inlets and an outlet;

a filter array also mounted to the frame and comprising a plurality of filter groupings, each filter grouping comprising:

a plurality of nested tubes, each nested tube comprising a cylindrical inner perforated tube formed from a metal sheet having complimentary mechanically formed seaming members formed along opposing edge portions and wherein the cylindrical inner perforated tube is formed by interlocking the complimentary mechanically formed seaming members to form a mechanical seam, the cylindrical inner perforated tube disposed within a corresponding cylindrical outer perforated tube such that an interstitial space is created between the inner and outer perforated tubes, the cylindrical outer perforated tube also formed from a metal sheet having complimentary mechanically formed seaming members formed along opposing edge portions and longitudinal recesses formed on a surface forming slotted opposing parallel openings separated by a recessed segment of the metal sheet and wherein the cylindrical outer perforated tube is formed by interlocking the complimentary mechanically formed seaming members to form a mechanical seam.

60. The high capacity suction strainer of Claim 59 wherein the mechanical seam of the cylindrical inner perforated tube has forms a helical structure winding about a longitudinal length of the cylindrical inner perforated tube.

61. The high capacity suction strainer of Claim 59 wherein the mechanical seam of the cylindrical outer perforated tube has forms a helical structure winding about a longitudinal length of the cylindrical outer perforated tube.

62. The high capacity suction strainer of Claim 59 wherein the nested tubes are arranged in a plurality of columns and rows and extend outwardly from the plenum such that each nested tube has a nested tube outlet forming a fluid communication between each interstitial space and an inlet on the flow-through plenum.

63. The high capacity suction strainer of Claim 59 further comprising:

a flow-through top plate comprising a plurality of top grates; and a flow-through bottom plate comprising a plurality of bottom grate located opposite the plurality of top grates relative to the nested tubes.

64. The high capacity suction strainer of Claim 63 wherein the plurality of top grates comprises:

a first top grate comprising a plurality of first apertures corresponding in size and shape to the outer circumference of each cylindrical outer perforated tube wherein a proximal end of each cylindrical outer perforated tube is inserted within and supported by a

corresponding first aperture and a plurality of second apertures located between and about the first apertures to allow a fluid flow therethrough.

65. The high capacity suction strainer of Claim 64 wherein the plurality of top grates comprises:

a second top grate comprising a plurality of first apertures aligned with the first apertures in the first top grate, each having a smaller cross-sectional area than an opening at the proximal end of the cylindrical outer perforated tube such that the interstitial space between the inner and outer tubes is at least substantially sealed against a surface of the second grate and such that a proximal end of each cylindrical inner perforated tube is inserted within and supported by a corresponding first aperture, and a plurality of second apertures aligned with the second apertures on the first top grate and located between and about the first apertures to allow a fluid flow therethrough.

66. The high capacity suction strainer of Claim 65 wherein the plurality of top grates comprises:

a third top grate comprising a plurality of first apertures aligned with the first apertures in the second top grate, each having a smaller cross-sectional area than an opening at the proximal end of the cylindrical inner perforated tube such that the proximal end of the cylindrical inner perforated tube abuts a surface of the third top grate forming the nested tube inlet, and a plurality of second apertures aligned with the second apertures on the second top grate and located between and about the first apertures to allow a fluid flow therethrough.

67. The high capacity suction strainer of Claim 66 wherein the first top grate and the third top grate sandwich the second top grate therebetween such that surfaces of the first top grate and the third top grate engage opposite surfaces of the second top grate.

68. The high capacity suction strainer of Claim 67 wherein the first top grate, the second top grate, and the third top grate are mechanically attached to the frame.

69. The high capacity suction strainer of Claim 68 wherein the plurality of bottom grates comprises:

a first bottom grate comprising a plurality of first apertures corresponding in size and shape to the outer circumference of each cylindrical outer perforated tube wherein a distal end of each cylindrical outer perforated tube is inserted within and supported by a corresponding first aperture.

70. The high capacity suction strainer of Claim 41 wherein the plurality of bottom grates comprises:

a second bottom grate comprising a plurality of first apertures, each aligned with a corresponding interstitial space between a cylindrical inner perforated tube and a cylindrical outer perforated tube, a plurality of second apertures, each aligned with an opening at a distal end of a corresponding cylindrical inner perforated tube forming the nested tube outlet aligned with an inlet on the plenum, a central webbing about each second aperture substantially sealing the opening at the distal end of the corresponding cylindrical inner perforated tube, and a plurality of mechanical fasteners, each fastener passing through a corresponding second aperture and engaging the distal end of the corresponding cylindrical inner perforated tube to maintain the corresponding cylindrical inner perforated tube in a desired position in the nested tube,

71. The high capacity suction strainer of Claim 42 wherein the first bottom grate and a surface of the plenum sandwich the second bottom grate therebetween such that surfaces of the first bottom grate and the plenum engage opposite surfaces of the second bottom grate.

72. The high capacity suction strainer of Claim 43 wherein the first bottom grate and the second bottom grate are mechanically attached to the frame.

73. A high capacity suction strainer for an emergency core cooling system in a nuclear power plant comprising:

a frame;

a flow-through plenum mounted to the frame and comprising a plurality of inlets and an outlet; a filter array also mounted to the frame and comprising a plurality of filter groupings, each filter grouping comprising:

a plurality of nested tubes, each nested tube comprising a cylindrical inner tube formed from a stainless steel sheet having complimentary mechanically formed seaming members formed along opposing edge portions and longitudinal recesses formed on a surface forming slotted opposing parallel openings separated by a recessed segment of the metal sheet wherein the cylindrical inner tube is formed by twisting the stainless steel sheet to form a helical orientation and draw the opposing edges portions together and interlocking the complimentary mechanically formed seaming members form a mechanical seam, the cylindrical inner tube disposed within a corresponding cylindrical outer tube such that an interstitial space is created between the inner and outer tubes, the outer cylindrical tube also formed from a stainless steel sheet having complimentary mechanically formed seaming members formed along opposing edge portions and longitudinal recesses formed on a surface forming slotted opposing parallel openings separated by a recessed segment of the metal sheet wherein the cylindrical tube is formed by twisting the stainless steel sheet to form a helical orientation and draw the opposing edges portions together and interlocking the complimentary mechanically formed seaming members form a mechanical seam,

wherein the nested tubes arranged in a plurality of columns and rows and extending outwardly from the plenum such that each nested tube has a nested tube outlet forming a fluid communication between each interstitial space and an inlet on the flow-through plenum;

a flow-through top plate comprising a plurality of top grates comprising: a first top grate comprising a plurality of first apertures corresponding in size and shape to the outer circumference of each outer tube wherein a proximal end of each outer tube is inserted within and supported by a corresponding first aperture and a plurality of second apertures located between and about the first apertures to allow a fluid flow therethrough;

a second top grate comprising a plurality of first apertures aligned with the first apertures in the first top grate, each having a smaller cross-sectional area than an opening at the proximal end of the outer tube such that the interstitial space between the inner and outer tubes is at least substantially sealed against a surface of the second grate and such that a proximal end of each inner tube is inserted within and supported by a corresponding first aperture, and a plurality of second apertures aligned with the second apertures on the first top grate and located between and about the first apertures to allow a fluid flow therethrough; and

a third top grate comprising a plurality of first apertures aligned with the first apertures in the second top grate, each having a smaller cross- sectional area than an opening at the proximal end of the inner tube such that the proximal end of the inner tube abuts a surface of the third top grate forming the nested tube inlet, and a plurality of second apertures aligned with the second apertures on the second top grate and located between and about the first apertures to allow a fluid flow therethrough,

wherein the first top grate and the third top grate sandwich the second top grate therebetween such that surfaces of the first top grate and the third top grate engage opposite surfaces of the second top grate, and

wherein the first top grate, the second top grate, and the third top grate are mechanically attached to the frame;

a flow-through bottom plate comprising a plurality of bottom grate located opposite the plurality of top grates relative to the nested tubes comprising:

a first bottom grate comprising a plurality of first apertures corresponding in size and shape to the outer circumference of each outer tube wherein a distal end of each outer tube is inserted within and supported by a corresponding first aperture; and

a second bottom grate comprising a plurality of first apertures, each aligned with a corresponding interstitial space between an inner tube and an outer tube, a plurality of second apertures, each aligned with an opening at a distal end of a corresponding inner tube forming the nested tube outlet aligned with an inlet on the plenum, a central webbing about each second aperture substantially sealing the opening at the distal end of the corresponding inner tube, and a plurality of mechanical fasteners, each fastener passing through a corresponding second aperture and engaging the distal end of the

corresponding inner tube to maintain the corresponding inner tube in a desired position in the nested tube, wherein the first bottom grate and a surface of the plenum sandwich the second bottom grate therebetween such that surfaces of the first bottom grate and the plenum engage opposite surfaces of the second bottom grate, and wherein the first bottom grate and the second bottom grate are mechanically attached to the frame.