Abstract:
An auxiliary wedge positioning apparatus/assembly  100  for use in a nuclear reactor pressure vessel  12  having riser piping  44  and  144  and a jet pump assembly  46  and  120 , the apparatus  100  having a combination slide wedge  105  and spring  103  mounted on a restraint bracket body  102  having a transverse rail  110  with end gull-wing hooked protrusions  111  with sections  150, 152, 156  and wing stability attachment  155 , the slide wedge used for placement between the riser piping  44  and  144  and jet pump assembly  46  and  120  to control vibrations during operation of the reactor vessel  12.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/259,291, filed on Nov. 9, 2009. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to jet pump stabilization in nuclear reactors and, more particularly, to an auxiliary wedge apparatus, for modifying jet pump wedge positioning assemblies within a nuclear reactor pressure vessel. 
     2. Description of Related Art 
     As detailed by Wivagg in U.S. Pat. No. 7,023,949 (“Wivagg &#39;949”). Boiling water reactors (“BWRs”) are designed to generate steam in reactor pressure vessels (“RPVs”) by heating the water surrounding uranium-containing tubes of fuel assemblies located in the RPV core regions. The RPVs have recirculation loops designed to facilitate the circulation of water in the core regions. The recirculation loops pump water out of the RPVs and return the water to the inlets of jet pump assemblies located in annular regions in the RPVs surrounding the core regions. The jet pump assemblies are designed to entrain the surrounding water in the annular regions and then discharge the water in a manner that induces a desired flow pattern in the core regions. The jet pump assemblies are subject to vibrations caused by hydraulic forces due to the flow of water. Thus, in one BWR design, the jet pump assemblies are horizontally supported against vibration within brackets by a suspension system including a wedge movably mounted on a vertically oriented guide rod that is attached to a jet pump assembly. The wedge, which may weigh about seven pounds, is designed to slide downwardly under the force of gravity into the space between the bracket and the jet pump assembly and thereby urge the jet pump against adjustment screws. 
     This design is shown in prior art  FIGS. 1-3  (from Wivagg &#39;949), wherein, in  FIG. 1 , nuclear reactor  10  contains outside reactor pressure vessel  12 , interior core shroud  18 , surrounding reactor core assemblies  20 , including fuel, usually UO 2  contained in zirconium based tubes, not shown. The core assemblies generate steam from cooling water. Inlet feed water  22  passes into recirculation water outlet nozzle  33  and is pumped to water inlet nozzle  42  via pumping loop (not shown) and passes to riser piping  44 . 
     Riser piping  44  terminates at a manifold  48 , sometimes referred to as a “ramshead.” Each jet pump assembly  46  of the pair generally includes an inlet  50  adjacent the manifold  48  that is open to an annular region defined by the wall of the RPV pressure vessel  12  and wall of the core shroud  18  for entraining the surrounding water in the annular region, a mixing section  52  and a diffuser section  54  supported on a crossplate  56 . The jet pump assembly  46  may have a boss  49  on its periphery surface as shown in  FIG. 2 . In the prior art, each jet pump assembly  46  had an associated main wedge  60  that was movably mounted on a vertically extending guide rod  62  fastened to the jet pump assembly  46 . As shown in prior art  FIG. 2 , the main wedge  60  was designed to slide vertically through an opening  68 , better shown in  FIG. 3 , in a restrainer bracket  70 , having adjustment set screws  80 , therethrough to contact the jet pump assembly  46 . The bracket  70  was attached to the riser pump piping  44  by welds  72  or other suitable means. As shown, there are no wedges near the adjustment set screws  80  of  FIGS. 2 and 3 . The weight of the main wedge  60  provides a sufficient force urging the jet pump assembly  46  against two (or more) adjustment set screws  80  for horizontally supporting the jet pump assembly  46  against hydraulic forces and vibrations. The outer surface of the main wedge  60  could be inclined relative to the edge surface of the bracket  70 . 
     Erbes et al. (U.S. Pat. No. 6,052,425) in their  FIG. 2  show a plurality of set screws  32 A to D passing through restrainer brackets  28 A and B. The main wedges are shown as  30 A and B disposed away from the set screws. This provides only two restraining wedge assemblies on opposite sides of inlet mixers assemblies  16 A and B. U.S. Pat. No. 7,627,074 (Erbes et al.) teaches dual spring wedges contained within a U-shaped bracket where dual guide rods pass through the top of the U-shaped bracket, through the springs to contact dual wedges. Problems associated with this design are complexity and probable cost. Other patents dealing with jet pump wedges include U.S. Pat. Nos. 4,675,149; 6,320,923; 6,490,331; and 6,788,756 (Perry et al.; Wivagg et al.; Erbes; and Erbes, respectively). Existing designs usually require that the space between the mixer belly band and the restrainer bracket that is being occupied, needs to be measured and therefore the wedge assembly needs to be machined to fit each specific location. 
     What is needed is a simplified wedge design that does not need to be machined at site and does not require the removal of jet pumps for installation greatly reduces the cost of implementing the repair and is a significant advantage to the owner. What is also needed is an auxiliary wedge assembly disposed next to, over, or in some connection with the set screws and secondary bracing means. 
     It is therefore an object of this invention to provide a design that installs from above without removing jet pump hardware and provides a mechanism to accommodate a large range in manufacturing variation in jet pump positioning. 
     SUMMARY OF THE INVENTION 
     The above problems and needs are provided and objects met by providing an auxiliary wedge positioning apparatus for use in a nuclear reactor consisting essentially of:
         (a) a restraint bracket body having a top end flat portion having one hole therethrough and a transverse rail with two bottom integral hooked protrusions each exactly opposite to each other and attached to the transverse rail, said protrusions having an angled gull wing shape with an upward member section and a downward member section;   (b) a single triangular slide wedge having a flat side attached to the transverse rail of the restraint bracket body, with an end flat portion and an angled side facing outward;   (c) a single slide rod passing through the top flat portion hole to contact the end flat portion of the triangular slide wedge; and   (d) a single spring disposed around the slide rod, the spring contacting the top end flat portion and exerting pressure against the end flat portion of the triangular slide wedge to exert pressure against adjacent bodies in the nuclear reactor.
 
Here, the hooked protrusions have a middle upward member section and an end downward section next to the transverse rail, and a wing stabilizing attachment parallel to the upward member section and the downward member section.
       

     The invention also provides at least two separate auxiliary wedge positioning apparatus in a nuclear reactor, containing riser piping that can feed pumped cooled water to at least one jet pump assembly having a circumferential restrainer bracket, which restrainer bracket has at least two vibration damping adjustment set screws each set in a set screw block contacting the jet pump assembly, the bracket is positioned around the jet pump assembly which bracket also contacts the riser piping, such assembly and riser piping subject to vibration during reactor operation, wherein a main wedge is utilized away from the set screws while the at least two separate auxiliary wedge positioning apparatus being positioned adjacent the set screws; wherein the at least two separate auxiliary wedge positioning apparatus each consist essentially of:
         (a) a restraint bracket body having a top end flat portion having one hole therethrough and a transverse rail with two bottom integral hooked protrusions each exactly opposite to each other and attached to the transverse rail, said protrusions having an angled gull wing shape with an upward member section and a downward member section, structured to contact the at least one set screw block;   (b) a single triangular slide wedge having a flat side attached to the top rail of the restraint bracket body, with an end flat portion and an angled side facing outward;   (c) a single slide rod passing through the top flat portion hole to contact the end flat portion of the triangular slide wedge; and   (d) a single spring disposed around the slide rod, the spring contacting the top end flat portion and exerting pressure against the end flat portion of the triangular slide wedge, this pressure on the slide wedge forcing it against the jet pump assembly.
 
Here, the at least one of the adjustment set screw blocks are positioned to contact part of the wing of the bracket body and the at least two separate auxiliary wedge positioning apparatus utilizes a combination of spring force and gravity to provide continuous adjustment against the at least one jet pump assembly. The hooked protrusions, in the form of a “gull wing,” provide stability under jet pump assembly vibration and prevent excessive circumferential movement around the jet pump assembly. The term “gull wing” is herein meant to define the configuration shown particularly in  FIGS. 6 and 7  as members  150 , which is a “parallel” member section, parallel and outward from the rail  110  and transverse at its bottom of the rail  110  and attached to the transverse rail  110  as shown in  FIGS. 5-7 ;  152 , which is an angled upward member; and  156 , which is an angled downward member attached to  152 ; all of hooked protrusions  111 .
       

     To reiterate, the auxiliary wedge of this invention uses a wedge action to restore the contact support between the jet pump restrainer bracket and the jet pump mixer (see  FIG. 2 ). The wedge uses a combination of spring force and gravity to provide continuous adjustments for possible alignment variations of the mixer and compensations for possible settlement after installation. The lines of contact between the wedge assembly, the inlet mixer and the restrainer bracket form a triangle that adds stability when installed (see  FIG. 4 ). Hooked protrusions, such as member  152 , and wing stabilizing attachment/contact pad  155 , contact or are adjacent to the set screw block  122 ′ (see  FIG. 6 ) to prevent excessive circumferential movement around the mixer. These protrusions also aid in installation of the apparatus while the mixer is in place and help maintain vertical orientation under vibration conditions. The wing stabilizing attachment is parallel to the upward member and the downward member (best shown in  FIG. 6 ) and adjacent to the at least one set screw block; and assists in preventing circumferential auxiliary wedge movement. Thus, positioning of the stabilizing attachment in such a manner is very important to this invention. The triangle contact design allows for wedge stability while not requiring machining or measurements as do other designs. The maximized stroke enables a minimum number of apparatus to accommodate the range of gap distances for the variations in existing plants. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention as set forth in the claims will become more apparent from the following detailed description and the accompanying drawings that show, by way of example only, a BWR jet pump assembly and a wedge positioning apparatus in accordance with a preferred practice of the present invention, wherein: 
         FIG. 1  is a prior art perspective schematic representation of a reactor pressure vessel which has been cut away to show a jet pump assembly arrangement; 
         FIG. 2  is a prior art partial perspective elevation view of a jet pump assembly horizontally supported by a bracket, the bracket adjustment containing set screws; 
         FIG. 3  is a prior art plan view of a jet pump assembly showing the position of the main wedge and two set/adjustment screws having no associated auxiliary wedge assembly; 
         FIG. 4  is a three-dimensional assembled view of the wedge auxiliary positioning apparatus of this invention, shown positioned to be inserted as an auxiliary stabilizing wedge against a jet pump assembly; 
         FIG. 5  is an exploded view of the wedge positioning apparatus of  FIG. 4  as it may be associated with a restraining bracket; 
         FIG. 6  is a front view of bottom brace hole  115  of the wedge positioning assembly only partially shown in  FIG. 4 ; and also showing “gull wing” hooked protrusions along with positions of an adjustment set screw set in a screw block, and restraining bracket  121 ; 
         FIG. 7 , which best illustrates the invention, is a top view of the wedge positioning apparatus of  FIG. 5  illustrating the “gull-wing” shape, and clearly shows the wing stabilizing attachment/contact pad; 
         FIG. 8  is a cross-sectional view of the wedge positioning apparatus with capture rod  104  in place; 
         FIG. 9  is a cut-away, three-dimensional view of one embodiment of a stabilized jet pump assembly and riser piping, with two installed auxiliary wedge positioning apparatus disposed about 120° away and opposite the main wedge; 
         FIG. 10  is an additional cut-away three-dimensional top view of a second embodiment of a stabilized jet pump assembly and riser piping, with two auxiliary wedges positioning apparatus disposed about 120° away and opposite the main wedge; and 
         FIG. 11  is a side view of  FIG. 10  and providing another view of  FIG. 9 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention generally relates to an auxiliary wedge spring apparatus structured to impart a wedge action to fill the space between the jet pump restrainer bracket and the mixing section of the jet pump assembly. 
     Referring now to the drawings,  FIGS. 4 and 5  are perspective and exploded views of an auxiliary wedge positioning apparatus  100  according to the main embodiment of the present invention. The auxiliary wedge positioning apparatus  100  includes a restraint bracket body  102 , single spring  103 , capture rod  104 , slide wedge  105 , pin  106 , and single slide rod  107 . As best seen in  FIG. 5 , the restraint bracket body  102  generally includes a rail  110  transverse to top end flat (spring stop) portion  108  angled at substantially 90° from rail  110  at a first end  116 . The auxiliary hooked protrusions  111  having a “gull wing” shape, defined previously, (best shown in  FIGS. 5 ,  6  and  7 ) at a second end opposite first end  116 . Thus, the top of the bracket body  102  is an L shape rather than a U shape. As can be seen best in  FIGS. 4 and 5 , the hooked protrusions forming the gull-wing are each exactly opposite each other and attached to the transverse rail  110  as part of parallel member section  150 . 
     The hooked protrusions  111 , shown in  FIG. 6 , pass to a parallel member section  150  next to the transverse rail and outward 90° from the rail  110  and the restraint bracket body  102 ; having an attached middle upward member section  152  at an angle  154  about 20° to 60° to the restraint bracket body  102 ; ending at an end downward member section  156  at an angle  158  about 70° to 110° from the upward member section  152 . The figure itself,  FIG. 6 , should control as to these angles. Also shown in  FIGS. 6 and 7  is a wing stabilizing attachment  155  connected to the bottom of upward member section  152  and downward section  156 , partly to ensure stability of the gull-wing to vibration, but also to be disposed adjacent to set screw block  122 ′ which after time may make contact with wing stabilizing attachment  155 , which increases wing rigidity and acts to assist or prevent excessive circumferential movement of the entire auxiliary wedge positioning apparatus. The stabilizing attachment  155  is parallel to the upward member section  152  and the downward member section  156 , as shown by parallel lines  159  shown in  FIG. 7 . A chamfer of sections  152  and  156  is also shown in  FIG. 7  at  157 . 
     Referring back to  FIG. 5 , the top end flat spring stop portion  108  includes a bore  109  therethrough to accommodate slide rod  107 . A first end of slide rod  107  is inserted through the bore  109 . Spring  103  is then inserted over and around/surrounding the slide rod  107 , such that a first end  103 ′ of spring  103  contacts one side of top end flat stop portion  108  and the second end of spring end  103 ″ provides pressure against the slide wedge  105 . 
     The single spring  103  is essential to the invention to exert variable pressure against the top wedge end  118 . Auxiliary slide wedge  105  is slipped onto rail  110  of restraint bracket body  102 , brought into contact with the second end  103 ″ of the spring, and receives the first end of slide rod  107  therein. Wedge pin  106  is inserted through a hole  112  in the first side of slide wedge  105 , through a bore  113  within the first end of slide rod  107 , and through a hole (not shown) on the second side of slide wedge  105 , where it is secured to ground the second end  103 ″ of spring in tension engagement with the flat top wedge end  118  of wedge  105 .  FIGS. 7 and 8  are additional views of the wedge positioning apparatus with the same numbering as  FIGS. 4 to 6  for the sake of simplicity. Also, in  FIG. 6  is restraining bracket  121  through which set screw  122  passes into set screw block  122 ′ which is disposed below upward member section  152  of hooked gull wing protrusion  111 , as shown, with contact points at  123  and  124  gull wing points. Machined hole  115  transverse to rail  110  is shown above the top of restraining bracket  121 . This machined hole  115  is also shown in  FIG. 5  and  FIG. 8 . 
     Wedge pin  106  is structured to couple slide rod  107  with slide wedge  105 . Slide wedge  105  is then pushed towards flat end top stop  108  so as to slightly compress spring  103 . Capture rod  104  is then inserted through a slot  114  in the top of slide wedge  105 . Capture rod  104  is then coupled to the second end of the restraint bracket body  102 . The slot  114  and capture rod  104  cooperate to allow slide wedge  105  to travel along the length of the restraint bracket body  102 . 
     Thus, in summary, the wedge positioning apparatus contains a restraint bracket body  102  having a rail  110  having at its bottom end two integral hooked protrusions/wings  111 , the restraint bracket body having an angled top end spring stop  108  having bore  109  therethrough receiving a slide rod  107  having a hole  113  therethrough for receiving a wedge pin  106 , which slide rod holds a spring  103  in place. The spring  103  contacts the flat top wedge end  118  of a slide wedge  105  forcing the slide wedge to be held in place, where the slide wedge contacts the rail  110 . 
     Now referring to  FIG. 9 , the auxiliary wedge positioning apparatus  100  uses a combination of spring force and gravity to provide continuous adjustment for possible alignment variations of the components involved (e.g., jet pump assembly  120 , restraining bracket  121 , set screw  122 , set screw block  122 ′, etc.) settle after installation. The apparatus can use a triangular, three-line contact  162  shown in dotted lines to maintain stability between all of the parts. The apparatus has hooked protrusions/wings  111  structured to contact either on the top of or at the bottom of the at least one restrainer bracket set screw block  122 ′, while bottom machining hole  115 , while not entirely shown here, is generally above the restraining bracket  121 . At least one of these protrusions  111  contact in one embodiment, the set screw block  122 ′ as shown in  FIG. 10  where the set screw block  122 ′ is disposed below protrusions  111 . Also shown is secondary bracing means  130  which has no part in this invention. The adjustment set screw  122 , within set screw block  122 ′, prevents excessive circumferential movement around the jet pump assembly  120 . The adjustment set screw blocks  122 ′ are positioned to contact at least one of the protrusions  111  as shown on their underside gull wing point  160  (in  FIG. 6 ). 
     These protrusions  111  and  111 ′ also aid in installation of the apparatus while the jet pump assembly  120  is in place and provide stability under vibration conditions. In one embodiment, the triangular contact design  162  allows for wedge stability while not requiring machining or take measurements on site. In one embodiment, the spring  103  is selected such that the wedge assembly positioning apparatus  100  is capable of accommodating the large range of gap distances encountered due to variations in existing nuclear plants. Also shown is riser piping  144  and hollow space between the jet pump assembly  120  and bracket  121 . 
       FIG. 11  is a side view of  FIG. 10 , using the same numbering for simplicity, but set screw blocks cannot be seen. The main wedge means, generally shown as  140 , is shown disposed from 110° to 130° usually 120° angle from both auxiliary wedges  100 . 
     Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.