US20130334182A1 - Core shroud corner joints - Google Patents
Core shroud corner joints Download PDFInfo
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- US20130334182A1 US20130334182A1 US13/953,230 US201313953230A US2013334182A1 US 20130334182 A1 US20130334182 A1 US 20130334182A1 US 201313953230 A US201313953230 A US 201313953230A US 2013334182 A1 US2013334182 A1 US 2013334182A1
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- Prior art keywords
- unitary
- core shroud
- core
- corner
- corners
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C13/00—Pressure vessels; Containment vessels; Containment in general
- G21C13/02—Details
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
- G21C3/30—Assemblies of a number of fuel elements in the form of a rigid unit
- G21C3/32—Bundles of parallel pin-, rod-, or tube-shaped fuel elements
- G21C3/322—Means to influence the coolant flow through or around the bundles
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C5/00—Moderator or core structure; Selection of materials for use as moderator
- G21C5/02—Details
- G21C5/08—Means for preventing undesired asymmetric expansion of the complete structure ; Stretching devices, pins
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Definitions
- the disclosed concept relates generally to nuclear reactors and, more particularly, to core shrouds for nuclear reactors.
- the disclosed concept also relates to an associated method of assembling core shrouds.
- the primary side of nuclear reactor power generating systems which are cooled with water under pressure, comprises a closed circuit that is isolated from and in heat-exchange relationship with a secondary side for the production of useful energy.
- FIG. 1 shows a simplified nuclear reactor primary system, including a generally cylindrical reactor pressure vessel 10 having a closure head 12 (also shown in FIG. 2 ) enclosing a nuclear core 14 .
- a liquid reactor coolant such as water
- a liquid reactor coolant is pumped into the vessel 110 by pumps 16 through the core 14 where heat energy is absorbed and is discharged to a heat exchanger 18 , typically referred to as a steam generator, in which heat is transferred to a utilization circuit (not shown), such as a steam-driven turbine generator.
- the reactor coolant is then returned to the pump 16 , completing the primary loop.
- reactor coolant piping 20 Typically, a plurality of the above-described loops are connected to a single reactor vessel 10 by reactor coolant piping 20 .
- FIGS. 2 and 3 show simplified side elevation and top plan views, respectively, of the pressure vessel 10 , and both show portions of the pressure vessel 10 in section view.
- the core 14 is comprised of a plurality of parallel, vertical co-extending fuel assemblies 22 , only two of which are shown in FIG. 2 for ease of illustration.
- the other vessel internal structures can be divided into the lower internals 24 and the upper internals 26 (both shown in FIG. 2 ).
- the lower internals 24 function to support and align the core and guide instrumentation, as well as direct flow within the vessel 10 .
- the upper internals 26 restrain or provide a secondary restraint for the fuel assemblies 22 , and support and guide instrumentation and core components, such as control rods 28 .
- coolant enters the vessel 10 through one or more inlet nozzles 30 , flows downward through an annulus between the vessel 10 and the core barrel 32 , is turned about 180° in a lower plenum 34 , passes upwardly through a lower core support plate 37 and a lower core plate 36 upon which the fuel assemblies 22 are seated, and through and about the fuel assemblies 22 .
- the lower core support plate 37 and lower core plate 36 are replaced by a single structure.
- the coolant flow through the core and surrounding area 38 is typically large, on the order of 400,000 gallons per minute at a velocity of approximately 20 feet per second.
- Coolant exiting the core 14 flows along the underside of the upper core plate 40 and upwardly through a plurality of perforations 42 .
- the coolant then flows upwardly and radially to one or more outlet nozzles 44 .
- a core shroud 17 is positioned inside the circular core barrel 32 , and includes a plurality of vertically extending plates 19 that convert the inner profile of the core barrel 32 to a stepped circumferential profile that generally matches the peripheral outline of the fuel assemblies 22 (shown in simplified form in FIG. 3 ) within the core 14 .
- the simplified cross-section view of FIG. 3 also shows a thermal shield 15 , which is interposed between the pressure vessel 10 and core barrel 32 . Some plants have neutron pads in lieu of the thermal shield.
- the plates 19 that form the stepped circumferential profile are substantially flat and abut at right angles at intersecting, corner, locations.
- some reactor vessel internals include atypical corner joints.
- these atypical corner joints can be characterized as being round for outside corner locations, being “key-like” (e.g., without limitation, having a groove) for interior locations and/or having relatively large pockets of open areas.
- Each atypical corner joint provides an area for flow to bypass the adjacent fuel assembly due to the low hydraulic resistance in these corners.
- flow calculations have shown a relatively high axial velocity in atypical core shroud corners. Among other disadvantages, this may result in unacceptable fuel rod vibration, which leads to fuel assembly grid-to-rod fretting, and may also cause elevated cross-flow velocities in this region.
- a core shroud comprises: a number of planar members; a number of unitary corners; and a number of subassemblies each comprising a combination of the planar members and the unitary corners.
- Each of the unitary corners may be substantially identical.
- Each of the unitary corners may comprise a unitary extrusion including a first planar portion and a second planar portion disposed perpendicularly with respect to the first planar portion.
- At least one of the subassemblies may comprises a plurality of the unitary corners, wherein the first planar portion of one of the unitary corners is joined to the second planar portion of another one of the unitary corners, in order that the unitary corners are disposed side-by-side in an alternating opposing relationship.
- a nuclear reactor which comprises: a pressure vessel; an annular core barrel seated within and supported by the pressure vessel; and a core shroud supported within the core barrel, the core shroud comprising: a number of planar members, a number of unitary corners, and a number of subassemblies each comprising a combination of the planar members and the unitary corners.
- the core shroud may further comprise a number of flow deflectors, and each of the unitary corners of the core shroud may include a curved interior junction and a curved exterior junction.
- Each of the flow deflectors may include a curved portion and number of substantially flat portions disposed opposite the curved portion, wherein the curved portion is structured to mate with a corresponding one of the curved interior junction and the curved exterior junction.
- the nuclear reactor may further comprise a number of grids disposed within the core shroud, wherein the substantially flat portions of the flow deflectors are structured to engage and support a portion of a corresponding one of the grids.
- a method of assembling a core shroud comprises: providing a number of planar members; extruding a plurality of unitary corners; joining a combination of the planar members and the unitary corners to form a number of subassemblies; and joining a plurality of the subassemblies to form at least a portion of the core shroud.
- the method may further comprise joining a plurality of the subassemblies to form a quarter perimeter segment of the core shroud, and may still further comprise joining four of the quarter perimeter segments to form the core shroud.
- FIG. 1 is a simplified schematic of a portion of a nuclear reactor to which the disclosed concept may be applied;
- FIG. 2 is an side elevation view, partially in section, of a nuclear reactor vessel and internal components to which the disclosed concept may be applied;
- FIG. 3 is a cross-sectional to plan view of a nuclear reactor vessel showing the pressure vessel, thermal shield, core barrel, core shroud and the core fuel assemblies;
- FIG. 4 is a top plan view of a core shroud and several peripheral core fuel assemblies
- FIG. 5 is an enlarged view of a segment of FIG. 4 ;
- FIG. 6 is an isometric view of a pair of unitary corners for a core shroud, in accordance with an embodiment of the disclosed concept
- FIG. 7 is an isometric view of a subassembly, in accordance with an embodiment of the disclosed concept, wherein the subassembly comprises three pairs of unitary corners;
- FIG. 8 is an isometric view of a subassembly, in accordance with an embodiment of the disclosed concept, wherein the subassembly comprises a unitary corner and a relatively narrow planar member;
- FIG. 9 is an isometric view of a subassembly, in accordance with an embodiment of the disclosed concept, wherein the subassembly comprises a unitary corner and a relatively wide planar member;
- FIG. 10 is an isometric view of another core shroud subassembly in accordance with the disclosed concept
- FIG. 11 is an isometric view of a quarter perimeter segment of a core shroud in accordance with the disclosed concept
- FIG. 12 is an isometric view of a complete core shroud assembly in accordance with the disclosed concept
- FIGS. 13A and 13B are front and back isometric views, respectively, of a flow deflector for use on the interior of a core shroud corner in accordance with another embodiment of the disclosed concept;
- FIG. 14 is an enlarged isometric view of an interior portion of a corner of a core shroud employing the interior flow deflector of FIGS. 13A and 13B ;
- FIG. 15 is an isometric view of the interior of the core shroud corner of FIG. 14 , shown employing three interior flow deflectors and further showing a portion of a fuel assembly grid in phantom line drawing;
- FIGS. 16A and 16B are isometric views of opposing sides of a flow deflector for use on the exterior of a core shroud corner in accordance with another embodiment of the disclosed concept;
- FIG. 17 is an isometric view of the exterior of a core shroud corner, shown employing two exterior flow deflectors.
- FIG. 18 is an enlarged isometric view of an exterior portion of the core shroud corner of FIG. 17 , shown employing a flow deflector in accordance with another embodiment of the disclosed concept.
- embodiments of the disclosed concept will be described as applied to core shrouds although it will become apparent that they could also be applied to replace or otherwise eliminate corner joints between joined components of other internals assemblies (e.g., without limitation, battle-former assemblies) to address and overcome problems associated therewith (e.g., without limitation, baffle-jetting).
- other internals assemblies e.g., without limitation, battle-former assemblies
- problems associated therewith e.g., without limitation, baffle-jetting
- unitary shall mean one single continuous piece of material that is devoid of any seems, joints or connections and which may be formed using any known or suitable method or process such as, for example and without limitation, an extrusion process.
- number shall mean one or an integer greater than one (i.e., a plurality).
- FIG. 4 shows a core shroud 100 .
- Several fuel assemblies 102 are shown in locations (generally indicated as A, B and C in FIG. 4 ) on the perimeter 106 of the core shroud 100 where they are adjacent to either an inner core shroud corner 108 or an outer core shroud corner 110 .
- there are 44 locations (only 10 locations are shown for ease of illustration) where fuel assemblies 102 will be adjacent to either inside corners 108 , outside corners 110 , or both inside and outside corners 108 , 110 .
- FIG. 5 shows an enlarged view of an inside corner 108 and an outside corner 110 of the core shroud 100 .
- each core shroud corner as a unitary corner 200 such as, for example and without limitation, a unitary extrusion having the desired corner shape.
- the open areas associated with conventional inside and outside corners 108 , 110 are, therefore, eliminated.
- Such open areas can result from forming (e.g., without limitation, bending) and/or from welding the seems (not shown in FIGS. 4 and 5 ) where two planar portions abut and are joined to make the corner joint. Recent changes in manufacturing extrusion technology have made this possible.
- each unitary corner 200 (two are shown) includes a first planar portion 202 and a second planar portion 204 disposed perpendicular to the first planar portion 202 , and without any seem or other connection therebetween. This is particularly advantageous where, as in the example of FIG.
- the width (e.g., without limitation, about 4.75 inch) when welded to a similar extrusion 200 , is sufficiently wide to accommodate a perimeter location having a single fuel assembly 102 (see, for example, fuel assemblies 102 in locations “A” in FIG. 4 ).
- the unitary extruded shapes 200 e.g., unitary corners
- FIGS. 8 and 9 show planar members 214 , 216 of widths 218 , 220 , respectively, that can be laser welded or otherwise suitably joined to a unitary corner 200 to accommodate core fuel assembly locations “B” and “C,” respectively, of FIG. 4 .
- the first planar member 214 includes opposing edges 215 , 217 and a first width 218 measured by the distance therebetween
- the second planar member 216 of FIG. 9 has opposing edges 219 , 221 and a second width 220 therebetween, which is greater than the first width 218 of first planar member 214 .
- the exemplary method of forming the perimeter 106 of the core shroud 100 involves welding or otherwise suitably joining two of the subassembly 222 , shown in FIG. 8 , to the subassembly 212 , shown in FIG. 7 , resulting in the subassembly 226 , shown in FIG. 10 .
- the unitary corner subassembly 210 of FIG. 6 and the subassembly 224 shown in FIG.
- each of the quarter perimeter segments 228 includes eleven of the unitary corners 200 , two of the first planar members 214 , and one of the second planar members 216 , as shown in FIG. 11 .
- four of the quarter perimeter segments 228 are welded or otherwise suitably joined together to form the complete core shroud 300 , shown in FIG. 12 (see also core shroud 100 of FIG. 4 ).
- any known or suitable alternative configuration, number and/or assembly sequence of components e.g., without limitation, unitary corners 200 ; first planar members 214 ; second planar members 216
- subassemblies e.g., without limitation 210 , 212 , 222 , 224 , 226 , 228
- any known or suitable alternative configuration, number and/or assembly sequence of components e.g., without limitation, unitary corners 200 ; first planar members 214 ; second planar members 216
- subassemblies e.g., without limitation 210 , 212 , 222 , 224 , 226 , 228
- components e.g., without limitation, unitary corners 200 ; first planar members 214 ; second planar members 216
- components are preferably welded using laser technology, as generally indicated in simplified form in FIG. 6
- any known or suitable alternative method, process or mechanism could be employed to suitably join the core shroud components (e.g., without limitation, unitary corners 200 ; first planar members 214 ; second planar members 216 ) and/or subassemblies (e.g., without limitation 210 , 212 , 222 , 224 , 226 , 228 ).
- the disclosed concept eliminates the inside and outside corner void areas associated with the known core shroud designs.
- the void areas are the result of extensive machining, bending and/or forming operations.
- the disclosed concept provides a unitary corner and therefore eliminates all seems at the corner, and also eliminates welding corner joints that are difficult to inspect due to lack of accessibility.
- the only welds are at locations away from the corners, which are substantially flat and/or relatively easy to access and facilitate inspection.
- each unitary corner extrusion 200 can be laser welded or otherwise suitably joined to like extrusions 200 (see, for example, FIGS. 6 and 7 ) and/or associated planar members 214 , 216 (see, for example, FIGS. 8 and 9 ).
- Each of the unitary corners 200 may also be substantially identical, with the first planar portion 202 of one unitary corner 200 being joined to the second planar portion 204 of another unitary corner 200 , in order that the unitary corners 200 are disposed side-by-side in an alternating opposing relationship (best shown in FIG. 7 ).
- the assembly method can employ rigid-like tooling and/or fixtures (not shown) to hold the extruded unitary corners 200 , planar members 214 , 216 and/or subassemblies 210 , 212 , 222 , 224 , 226 , 228 . Therefore, weld distortion, which can be caused for example by heat, is minimized. Furthermore, compared to conventional welding processes that use consumable electrodes, laser welding results in minimal heat input, which should further result in better dimensional control. This will improve core cavity dimensions, particularly at the final stage of welding the tour quarter perimeter segments 228 ( FIGS. 11 and 12 ), whereas the current process results in significant machining being required after welding, in order to meet core cavity dimensional requirements.
- the extruded unitary corner design of the disclosed concept eliminates the welding of corner joints altogether and, therefore, eliminates a significant amount of machining work and time and cost associated therewith. Additionally, due to the possibility of less machining being necessary after welding, a further savings may be available by way of the ability to potentially use thinner extruded shapes.
- baffle-former assembly corner joints (not shown)
- an extruded unitary corner could be retro-fitted to an existing baffle-former design to eliminate corner joints between baffle plates (not shown) of a baffle-former assembly (not shown).
- baffle jetting is a result of water jetting from inside the baffle-former core cavity toward the direction of the core as a result of gaps or openings in the corner joint.
- FIGS. 13A-15 and 16 A- 18 respectively show interior flow deflectors 302 and exterior flow deflectors 304 , 304 ′, in accordance with non-limiting example alternative embodiments of the disclosed concept.
- the flow deflector 302 sometimes referred to as a “hockey puck” type of insert, is structured to be installed in the interior junction 112 of the core shroud corner 108 , as shown in FIGS. 14 and 15 .
- each of the flow deflectors 302 includes a curved portion 306 and a number of substantially flat portions 308 (two are shown in FIGS. 13A-15 ).
- the curved portion 306 is structured to mate with the curved interior junction 112 of the core shroud interior corner 108 , as shown in FIGS. 14 and 15 .
- the dimensional characteristics of the flow deflector 302 e.g., without limitation, height of the flow deflector 302
- the height of fuel assembly grids 46 e.g., without limitation, fuel assembly grids 46 , partially shown in phantom line drawing in FIG. 15 ).
- the flow deflectors 302 deflect the flow of coolant so as to reduce axial velocity and resist undesired flow bypass, for example, by filling an open area in the corner (e.g., 108 ), but they can also serve to further support the grids 46 .
- a fillet weld (indicated generally be reference numeral 310 in FIG. 15 ) may be used, as shown for example, in FIG. 15 .
- each exterior flow deflector 304 , 304 ′ preferably includes a curved portion 312 and a number of substantially flat portions 314 (two are shown) disposed generally opposite the curved portion 312 .
- the curved portion 312 is structured to mate with, and be suitably joined (e.g., without limitation, welded) to, the curved exterior junction 114 of the exterior corner 110 of the core shroud, as shown in FIGS. 17 and 18 .
- any known or suitable alternative number, shape and/or configuration of flow deflectors (not shown) other than, or in addition to, those that are shown and described herein, could be employed without departing from the scope of the disclosed concept.
- FIG. 17 shows two different exterior flow deflectors 304 , 304 ′ disposed on the exterior corner 110 of the core shroud 100 , each of which has a different length. Additionally, as shown in exaggerated form in FIG.
- the flow deflector 304 may include a chamfer 316 .
- chamfer 316 which may for example, be formed as part of a fillet weld, would help, for example, to avoid undesired interaction (e.g., without limitation, a “snag”) with a grid during fuel assembly loading and unloading.
- flow deflectors e.g., without limitation, 302 , 304 , 304 ′
- could be incorporated independently e.g., as a separate solution from the disclosed unitary corner concept, for example, with an existing core shroud design, to improve the flow-related problems associated with the corner joints thereof.
- such flow deflectors e.g., without limitation, 302 , 304 , 304 ′
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Abstract
A core shroud is provided, which includes a number of planar members, a number of unitary corners, and a number of subassemblies each comprising a combination of the planar members and the unitary corners. Each unitary corner comprises a unitary extrusion including a first planar portion and a second planar portion disposed perpendicularly with respect to the first planar portion. At least one of the subassemblies comprises a plurality of the unitary corners disposed side-by-side in an alternating opposing relationship. A plurality of the subassemblies can be combined to form a quarter perimeter segment of the core shroud. Four quarter perimeter segments join together to form the core shroud.
Description
- This application is a divisional of application Ser. No. 12/634,836, filed Dec. 10, 2009, and entitled “CORE SHROUD CORNER JOINTS”.
- This application claims the benefit of Provisional Application No. 61/138,140, filed on Dec. 17, 2008 and entitled, “Core Shroud Corner Joints.”
- This invention was made with government support under Contract No. DE-FC07-05ID14636 awarded by the Department of Energy. The government has certain rights in this invention.
- 1. Field
- The disclosed concept relates generally to nuclear reactors and, more particularly, to core shrouds for nuclear reactors. The disclosed concept also relates to an associated method of assembling core shrouds.
- 2. Background Information
- The primary side of nuclear reactor power generating systems which are cooled with water under pressure, comprises a closed circuit that is isolated from and in heat-exchange relationship with a secondary side for the production of useful energy.
-
FIG. 1 shows a simplified nuclear reactor primary system, including a generally cylindricalreactor pressure vessel 10 having a closure head 12 (also shown inFIG. 2 ) enclosing anuclear core 14. A liquid reactor coolant, such as water, is pumped into thevessel 110 bypumps 16 through thecore 14 where heat energy is absorbed and is discharged to aheat exchanger 18, typically referred to as a steam generator, in which heat is transferred to a utilization circuit (not shown), such as a steam-driven turbine generator. The reactor coolant is then returned to thepump 16, completing the primary loop. Typically, a plurality of the above-described loops are connected to asingle reactor vessel 10 byreactor coolant piping 20. -
FIGS. 2 and 3 show simplified side elevation and top plan views, respectively, of thepressure vessel 10, and both show portions of thepressure vessel 10 in section view. Thecore 14 is comprised of a plurality of parallel, verticalco-extending fuel assemblies 22, only two of which are shown inFIG. 2 for ease of illustration. For purposes of this description, the other vessel internal structures can be divided into thelower internals 24 and the upper internals 26 (both shown inFIG. 2 ). In conventional designs, thelower internals 24 function to support and align the core and guide instrumentation, as well as direct flow within thevessel 10. Theupper internals 26 restrain or provide a secondary restraint for thefuel assemblies 22, and support and guide instrumentation and core components, such ascontrol rods 28. In operation, coolant enters thevessel 10 through one ormore inlet nozzles 30, flows downward through an annulus between thevessel 10 and thecore barrel 32, is turned about 180° in alower plenum 34, passes upwardly through a lowercore support plate 37 and alower core plate 36 upon which thefuel assemblies 22 are seated, and through and about thefuel assemblies 22. In some designs the lowercore support plate 37 andlower core plate 36 are replaced by a single structure. The coolant flow through the core and surroundingarea 38 is typically large, on the order of 400,000 gallons per minute at a velocity of approximately 20 feet per second. The resulting pressure drop and frictional forces tends to cause the fuel assemblies to rise, which movement is restrained by theupper internals 26, including a circularupper core plate 40. Coolant exiting thecore 14 flows along the underside of theupper core plate 40 and upwardly through a plurality of perforations 42. The coolant then flows upwardly and radially to one ormore outlet nozzles 44. - As shown in simplified form in
FIG. 3 , acore shroud 17 is positioned inside thecircular core barrel 32, and includes a plurality of vertically extending plates 19 that convert the inner profile of thecore barrel 32 to a stepped circumferential profile that generally matches the peripheral outline of the fuel assemblies 22 (shown in simplified form inFIG. 3 ) within thecore 14. The simplified cross-section view ofFIG. 3 also shows a thermal shield 15, which is interposed between thepressure vessel 10 andcore barrel 32. Some plants have neutron pads in lieu of the thermal shield. - Typically, the plates 19 that form the stepped circumferential profile are substantially flat and abut at right angles at intersecting, corner, locations. As a result of machining and/or forming, some reactor vessel internals, however, include atypical corner joints. By way of example, these atypical corner joints can be characterized as being round for outside corner locations, being “key-like” (e.g., without limitation, having a groove) for interior locations and/or having relatively large pockets of open areas. Each atypical corner joint provides an area for flow to bypass the adjacent fuel assembly due to the low hydraulic resistance in these corners. In fact, flow calculations have shown a relatively high axial velocity in atypical core shroud corners. Among other disadvantages, this may result in unacceptable fuel rod vibration, which leads to fuel assembly grid-to-rod fretting, and may also cause elevated cross-flow velocities in this region.
- There is, therefore, room for improvement in core shrouds and corner joints therefor.
- These needs and others are met by embodiments of the disclosed concept, which provide an improved design and assembly method for nuclear reactor core shrouds wherein, among other benefits, the corners of the core shroud assembly are preferably of a unitary design comprising one single continuous piece of material that is devoid of any seems or associated gaps or voids.
- As one aspect of the disclosed concept, a core shroud is provided. The core shroud comprises: a number of planar members; a number of unitary corners; and a number of subassemblies each comprising a combination of the planar members and the unitary corners.
- Each of the unitary corners may be substantially identical. Each of the unitary corners may comprise a unitary extrusion including a first planar portion and a second planar portion disposed perpendicularly with respect to the first planar portion. At least one of the subassemblies may comprises a plurality of the unitary corners, wherein the first planar portion of one of the unitary corners is joined to the second planar portion of another one of the unitary corners, in order that the unitary corners are disposed side-by-side in an alternating opposing relationship.
- As another aspect of the disclosed concept, a nuclear reactor is provided which comprises: a pressure vessel; an annular core barrel seated within and supported by the pressure vessel; and a core shroud supported within the core barrel, the core shroud comprising: a number of planar members, a number of unitary corners, and a number of subassemblies each comprising a combination of the planar members and the unitary corners.
- The core shroud may further comprise a number of flow deflectors, and each of the unitary corners of the core shroud may include a curved interior junction and a curved exterior junction. Each of the flow deflectors may include a curved portion and number of substantially flat portions disposed opposite the curved portion, wherein the curved portion is structured to mate with a corresponding one of the curved interior junction and the curved exterior junction. The nuclear reactor may further comprise a number of grids disposed within the core shroud, wherein the substantially flat portions of the flow deflectors are structured to engage and support a portion of a corresponding one of the grids.
- As a further aspect of the disclosed concept, a method of assembling a core shroud is provided. The method comprises: providing a number of planar members; extruding a plurality of unitary corners; joining a combination of the planar members and the unitary corners to form a number of subassemblies; and joining a plurality of the subassemblies to form at least a portion of the core shroud.
- The method may further comprise joining a plurality of the subassemblies to form a quarter perimeter segment of the core shroud, and may still further comprise joining four of the quarter perimeter segments to form the core shroud.
- A further understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
-
FIG. 1 is a simplified schematic of a portion of a nuclear reactor to which the disclosed concept may be applied; -
FIG. 2 is an side elevation view, partially in section, of a nuclear reactor vessel and internal components to which the disclosed concept may be applied; -
FIG. 3 is a cross-sectional to plan view of a nuclear reactor vessel showing the pressure vessel, thermal shield, core barrel, core shroud and the core fuel assemblies; -
FIG. 4 is a top plan view of a core shroud and several peripheral core fuel assemblies; -
FIG. 5 is an enlarged view of a segment ofFIG. 4 ; -
FIG. 6 is an isometric view of a pair of unitary corners for a core shroud, in accordance with an embodiment of the disclosed concept; -
FIG. 7 is an isometric view of a subassembly, in accordance with an embodiment of the disclosed concept, wherein the subassembly comprises three pairs of unitary corners; -
FIG. 8 is an isometric view of a subassembly, in accordance with an embodiment of the disclosed concept, wherein the subassembly comprises a unitary corner and a relatively narrow planar member; -
FIG. 9 is an isometric view of a subassembly, in accordance with an embodiment of the disclosed concept, wherein the subassembly comprises a unitary corner and a relatively wide planar member; -
FIG. 10 is an isometric view of another core shroud subassembly in accordance with the disclosed concept; -
FIG. 11 is an isometric view of a quarter perimeter segment of a core shroud in accordance with the disclosed concept; -
FIG. 12 is an isometric view of a complete core shroud assembly in accordance with the disclosed concept; -
FIGS. 13A and 13B are front and back isometric views, respectively, of a flow deflector for use on the interior of a core shroud corner in accordance with another embodiment of the disclosed concept; -
FIG. 14 is an enlarged isometric view of an interior portion of a corner of a core shroud employing the interior flow deflector ofFIGS. 13A and 13B ; -
FIG. 15 is an isometric view of the interior of the core shroud corner ofFIG. 14 , shown employing three interior flow deflectors and further showing a portion of a fuel assembly grid in phantom line drawing; -
FIGS. 16A and 16B are isometric views of opposing sides of a flow deflector for use on the exterior of a core shroud corner in accordance with another embodiment of the disclosed concept; -
FIG. 17 is an isometric view of the exterior of a core shroud corner, shown employing two exterior flow deflectors; and -
FIG. 18 is an enlarged isometric view of an exterior portion of the core shroud corner ofFIG. 17 , shown employing a flow deflector in accordance with another embodiment of the disclosed concept. - For purposes of illustration, embodiments of the disclosed concept will be described as applied to core shrouds although it will become apparent that they could also be applied to replace or otherwise eliminate corner joints between joined components of other internals assemblies (e.g., without limitation, battle-former assemblies) to address and overcome problems associated therewith (e.g., without limitation, baffle-jetting).
- Directional phrases used herein, such as, for example, interior, exterior, inside, outside, top, bottom and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.
- As employed herein, the term “unitary” shall mean one single continuous piece of material that is devoid of any seems, joints or connections and which may be formed using any known or suitable method or process such as, for example and without limitation, an extrusion process.
- As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).
-
FIG. 4 shows acore shroud 100.Several fuel assemblies 102 are shown in locations (generally indicated as A, B and C inFIG. 4 ) on theperimeter 106 of thecore shroud 100 where they are adjacent to either an innercore shroud corner 108 or an outercore shroud corner 110. For example and without limitation, in the non-limiting example ofFIG. 4 , there are 44 locations (only 10 locations are shown for ease of illustration) wherefuel assemblies 102 will be adjacent to either insidecorners 108,outside corners 110, or both inside andoutside corners FIG. 5 shows an enlarged view of aninside corner 108 and anoutside corner 110 of thecore shroud 100. - As shown in
FIGS. 6-12 , the disclosed concept entails the fabrication of each core shroud corner as aunitary corner 200 such as, for example and without limitation, a unitary extrusion having the desired corner shape. The open areas associated with conventional inside andoutside corners 108, 110 (FIGS. 4 and 5 ) are, therefore, eliminated. Such open areas can result from forming (e.g., without limitation, bending) and/or from welding the seems (not shown inFIGS. 4 and 5 ) where two planar portions abut and are joined to make the corner joint. Recent changes in manufacturing extrusion technology have made this possible. For example and without limitation, up to about 4.75 inch×4.75 inch×1 inch or larger full-length (e.g., without limitation, see length, ofFIG. 6 which may be, for example and without limtation, about 180 inches (not shown to scale)) extruded shapes are possible. Thus, as shown inFIG. 6 , each unitary corner 200 (two are shown) includes a firstplanar portion 202 and a secondplanar portion 204 disposed perpendicular to the firstplanar portion 202, and without any seem or other connection therebetween. This is particularly advantageous where, as in the example ofFIG. 6 , the width (e.g., without limitation, about 4.75 inch) when welded to asimilar extrusion 200, is sufficiently wide to accommodate a perimeter location having a single fuel assembly 102 (see, for example,fuel assemblies 102 in locations “A” inFIG. 4 ). The unitary extruded shapes 200 (e.g., unitary corners) can then be laser welded or otherwise suitably joined, for example, to form asubassembly 210, as shown inFIG. 6 . - To complete the perimeter of the core shroud near the pair of
filet assemblies 102 designated as “A” inFIG. 4 , continued welding of three pairs of theunitary corners 200 is completed to form asubassembly 212, as shown inFIG. 7 . For the other two typical perimeter locations, which have two or three fuel assemblies in a row (see, for example,fuel assemblies 102 at the locations designated as “B” and “C” inFIG. 4 ), planar members 214 (FIG. 8 ), 216 (FIG. 9 ) of differing widths 218 (FIG. 8 ), 220 (FIG. 9 ), are welded to aunitary corner 200 to formsubassemblies FIGS. 8 and 9 , respectively. Specifically,FIGS. 8 and 9 showplanar members widths unitary corner 200 to accommodate core fuel assembly locations “B” and “C,” respectively, ofFIG. 4 . In the example ofFIG. 8 , the firstplanar member 214 includes opposingedges first width 218 measured by the distance therebetween, whereas the secondplanar member 216 ofFIG. 9 has opposingedges second width 220 therebetween, which is greater than thefirst width 218 of firstplanar member 214. - The exemplary method of forming the
perimeter 106 of the core shroud 100 (FIG. 4 ), involves welding or otherwise suitably joining two of thesubassembly 222, shown inFIG. 8 , to thesubassembly 212, shown inFIG. 7 , resulting in thesubassembly 226, shown inFIG. 10 . Lastly, to complete a quarter perimeter segment, orsubassembly 228, of the core shroud 100 (FIG. 4 ; also referred to generally as 300 inFIG. 12 ), theunitary corner subassembly 210 ofFIG. 6 and thesubassembly 224, shown inFIG. 9 , are welded or otherwise suitably joined to subassembly 226 ofFIG. 10 . In the example shown and described herein, each of thequarter perimeter segments 228 includes eleven of theunitary corners 200, two of the firstplanar members 214, and one of the secondplanar members 216, as shown inFIG. 11 . Finally, four of thequarter perimeter segments 228 are welded or otherwise suitably joined together to form thecomplete core shroud 300, shown inFIG. 12 (see alsocore shroud 100 ofFIG. 4 ). - It will be appreciated that any known or suitable alternative configuration, number and/or assembly sequence of components (e.g., without limitation,
unitary corners 200; firstplanar members 214; second planar members 216) and subassemblies (e.g., withoutlimitation - It will also be appreciated that while components (e.g., without limitation,
unitary corners 200; firstplanar members 214; second planar members 216) are preferably welded using laser technology, as generally indicated in simplified form inFIG. 6 , that any known or suitable alternative method, process or mechanism could be employed to suitably join the core shroud components (e.g., without limitation,unitary corners 200; firstplanar members 214; second planar members 216) and/or subassemblies (e.g., withoutlimitation - Among other advantages, the disclosed concept eliminates the inside and outside corner void areas associated with the known core shroud designs. The void areas are the result of extensive machining, bending and/or forming operations. The disclosed concept provides a unitary corner and therefore eliminates all seems at the corner, and also eliminates welding corner joints that are difficult to inspect due to lack of accessibility. The only welds are at locations away from the corners, which are substantially flat and/or relatively easy to access and facilitate inspection.
- Additionally, in stages, each
unitary corner extrusion 200 can be laser welded or otherwise suitably joined to like extrusions 200 (see, for example,FIGS. 6 and 7 ) and/or associatedplanar members 214, 216 (see, for example,FIGS. 8 and 9 ). Each of theunitary corners 200 may also be substantially identical, with the firstplanar portion 202 of oneunitary corner 200 being joined to the secondplanar portion 204 of anotherunitary corner 200, in order that theunitary corners 200 are disposed side-by-side in an alternating opposing relationship (best shown inFIG. 7 ). Moreover, it will be appreciated that the assembly method can employ rigid-like tooling and/or fixtures (not shown) to hold the extrudedunitary corners 200,planar members subassemblies FIGS. 11 and 12 ), whereas the current process results in significant machining being required after welding, in order to meet core cavity dimensional requirements. - The extruded unitary corner design of the disclosed concept eliminates the welding of corner joints altogether and, therefore, eliminates a significant amount of machining work and time and cost associated therewith. Additionally, due to the possibility of less machining being necessary after welding, a further savings may be available by way of the ability to potentially use thinner extruded shapes. The possibility exists for the
aforementioned subassemblies FIG. 4 ; see alsocore shroud assembly 300 ofFIG. 12 ). - It will also be appreciated that the potential exists to incorporate the disclosed unitary corner concept with respect to other reactors internals assemblies (e.g., without limitation, baffle-former assembly corner joints (not shown)). For example and without limitation, an extruded unitary corner could be retro-fitted to an existing baffle-former design to eliminate corner joints between baffle plates (not shown) of a baffle-former assembly (not shown). Thus, the potential for undesirable “baffle jetting” is eliminated. “Baffle jetting is a result of water jetting from inside the baffle-former core cavity toward the direction of the core as a result of gaps or openings in the corner joint.
-
FIGS. 13A-15 and 16A-18 respectively showinterior flow deflectors 302 andexterior flow deflectors FIGS. 13A-15 , theflow deflector 302, sometimes referred to as a “hockey puck” type of insert, is structured to be installed in theinterior junction 112 of thecore shroud corner 108, as shown inFIGS. 14 and 15 . Specifically, each of theflow deflectors 302 includes acurved portion 306 and a number of substantially flat portions 308 (two are shown inFIGS. 13A-15 ). Thecurved portion 306 is structured to mate with the curvedinterior junction 112 of the core shroudinterior corner 108, as shown inFIGS. 14 and 15 . Thus, it will be appreciated that the dimensional characteristics of the flow deflector 302 (e.g., without limitation, height of the flow deflector 302) can be established to be consistent with, for example, the height of fuel assembly grids 46 (e.g., without limitation,fuel assembly grids 46, partially shown in phantom line drawing inFIG. 15 ). Thus, not only do theflow deflectors 302 deflect the flow of coolant so as to reduce axial velocity and resist undesired flow bypass, for example, by filling an open area in the corner (e.g., 108), but they can also serve to further support thegrids 46. To secure theflow deflector 302 to thecore shroud 100, a fillet weld (indicated generally be reference numeral 310 inFIG. 15 ) may be used, as shown for example, inFIG. 15 . - Implementation of the aforementioned
exterior flow deflector exterior corners 110 of thecore shroud 100 is shown in the non-limiting examples ofFIGS. 16A-17 and 18, respectively. As with theinterior flow deflectors 302, previously discussed, the height of theexterior flow deflectors FIG. 15 ). Eachexterior flow deflector curved portion 312 and a number of substantially flat portions 314 (two are shown) disposed generally opposite thecurved portion 312. Thecurved portion 312 is structured to mate with, and be suitably joined (e.g., without limitation, welded) to, thecurved exterior junction 114 of theexterior corner 110 of the core shroud, as shown inFIGS. 17 and 18 . It will, however, be appreciated that any known or suitable alternative number, shape and/or configuration of flow deflectors (not shown) other than, or in addition to, those that are shown and described herein, could be employed without departing from the scope of the disclosed concept. For example and without limitation,FIG. 17 shows two differentexterior flow deflectors exterior corner 110 of thecore shroud 100, each of which has a different length. Additionally, as shown in exaggerated form inFIG. 18 , theflow deflector 304 may include achamfer 316.Such chamfer 316, which may for example, be formed as part of a fillet weld, would help, for example, to avoid undesired interaction (e.g., without limitation, a “snag”) with a grid during fuel assembly loading and unloading. It will also be appreciated that such flow deflectors (e.g., without limitation, 302, 304, 304′) could be incorporated independently (e.g., as a separate solution from the disclosed unitary corner concept), for example, with an existing core shroud design, to improve the flow-related problems associated with the corner joints thereof. It will, therefore, further be appreciated that such flow deflectors (e.g., without limitation, 302, 304, 304′) are not required in a least some embodiments in accordance with the disclosed concept. - While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.
Claims (6)
1. A method of assembling a core shroud, the method comprising:
providing a number of planar members;
extruding a plurality of unitary corners;
joining a combination of said planar members and said unitary corners to form a number of subassemblies; and
joining a plurality of said subassemblies to form at least a portion of said core shroud.
2. The method of claim 1 , further comprising joining a plurality of said subassemblies to form a quarter perimeter segment of said core shroud.
3. The method of claim 2 , further comprising joining four of said quarter perimeter segments to form said core shroud.
4. The method of claim 1 , wherein each of said unitary corners includes a first planar portion and a second planar portion disposed perpendicularly with respect to the first planar portion; and wherein said method further comprises joining the first planar portion of one of said unitary corners to the second planar portion of another one of said unitary corners, in order that said unitary corners are disposed side-by-side in an alternating opposing relationship.
5. The method of claim 1 , wherein said joining steps are performed by laser welding.
6. The method of claim 1 , wherein said joining steps further comprise securing at least one of said planar members, said unitary corners and said subassemblies in a desired position with a number of fixtures.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US13/953,230 US20130334182A1 (en) | 2008-12-17 | 2013-07-29 | Core shroud corner joints |
Applications Claiming Priority (3)
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US13814008P | 2008-12-17 | 2008-12-17 | |
US12/634,836 US8532245B2 (en) | 2008-12-17 | 2009-12-10 | Core shroud corner joints |
US13/953,230 US20130334182A1 (en) | 2008-12-17 | 2013-07-29 | Core shroud corner joints |
Related Parent Applications (1)
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US12/634,836 Division US8532245B2 (en) | 2008-12-17 | 2009-12-10 | Core shroud corner joints |
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US20130334182A1 true US20130334182A1 (en) | 2013-12-19 |
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US12/634,836 Active 2031-12-14 US8532245B2 (en) | 2008-12-17 | 2009-12-10 | Core shroud corner joints |
US13/953,230 Abandoned US20130334182A1 (en) | 2008-12-17 | 2013-07-29 | Core shroud corner joints |
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US12/634,836 Active 2031-12-14 US8532245B2 (en) | 2008-12-17 | 2009-12-10 | Core shroud corner joints |
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US (2) | US8532245B2 (en) |
EP (1) | EP2366181B1 (en) |
JP (1) | JP5748179B2 (en) |
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CN (1) | CN102257574B (en) |
BR (1) | BRPI0922598A2 (en) |
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CN107966576B (en) | 2013-03-15 | 2021-08-03 | 雅培制药有限公司 | Automated diagnostic analyzer with rear accessible track system and related methods |
CN103231169B (en) * | 2013-04-19 | 2015-05-20 | 上海第一机床厂有限公司 | Laser welding method for reactor core wrapping tube |
US9721687B2 (en) | 2014-08-06 | 2017-08-01 | Ge-Hitachi Nuclear Energy Americas Llc | Method of storing a chimney assembly of a reactor pressure vessel during a nuclear reactor outage |
US9879472B2 (en) | 2015-06-05 | 2018-01-30 | Quanex Corporation | Frame assembly including a cornerlock |
US9869122B2 (en) | 2016-01-29 | 2018-01-16 | Quanex Corporation | Cornerlock having a self configurable first body member |
CN106312357B (en) * | 2016-10-31 | 2019-01-22 | 中国核动力研究设计院 | It is a kind of to be layered the monoblock type core baffle structure being welded and fixed |
CN114273759A (en) * | 2021-12-30 | 2022-04-05 | 东方电气(武汉)核设备有限公司 | Welding method of reactor core shroud assembly |
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WO2010071763A3 (en) | 2010-10-21 |
BRPI0922598A2 (en) | 2015-12-22 |
EP2366181B1 (en) | 2014-07-23 |
WO2010071763A2 (en) | 2010-06-24 |
US8532245B2 (en) | 2013-09-10 |
CN102257574A (en) | 2011-11-23 |
ZA201103994B (en) | 2012-02-29 |
KR101574826B1 (en) | 2015-12-04 |
JP2012512417A (en) | 2012-05-31 |
JP5748179B2 (en) | 2015-07-15 |
CA2744943A1 (en) | 2010-06-24 |
CA2744943C (en) | 2016-01-26 |
EP2366181A2 (en) | 2011-09-21 |
CN102257574B (en) | 2014-09-03 |
KR20110103393A (en) | 2011-09-20 |
US20100150298A1 (en) | 2010-06-17 |
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