Abstract:
Example embodiments are directed to core spray sparger T-box repairs, specifically, to universal core spray sparger T-box weldless clamps having remote-friendly operation and methods of using universal core spray sparger T-box weldless clamps. Example embodiment clamps may be secured without welding to a variety of upper and lower sparger T-box configurations. Example embodiment clamps may be configured to simultaneously engage a sparger T-box in multiple dimensions to allow a universal fit. Further, example embodiment clamps may be accessed, installed, or removed by interacting only with a front side of the example embodiment clamps, thus potentially reducing difficulty and cost in remote access repairs to example clamps.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    Example embodiments generally relate to Boiling Water Reactors (BWRs) and assemblies and methods for reinforcing piping for coolant spray within such reactors. 
         [0003]    2. Description of Related Art 
         [0004]    Generally, BWRs include a reactor core surrounded by a shroud and a shroud support structure. Piping typically penetrates this shroud to deliver emergency coolant water to the core in the event of an emergency involving a loss of coolant or where coolant is otherwise unavailable to the core. 
         [0005]    As shown in  FIG. 1 , such piping includes core spray piping  10  and spargers used to deliver coolant water to the reactor core. The core spray cooling water is typically supplied to the reactor core region through a sparger T-box  15  that penetrates the shroud wall. The distal end of the T-box  15  is inside the shroud, while the proximal end extends outside the shroud. 
         [0006]    The sparger T-box typically intersects two sparger pipes  10  to form a piping “T.” The sparger pipes  10  are typically welded to the sparger T-box  15 . The distal end of the T-box  15  may be capped by a flat cover plate  20  welded to the T-box  15 . While only a lower sparger T-box  15  is shown in  FIG. 1 , upper sparger T-boxes are typically present as well and roughly match the configuration of the lower sparger T-box in the upper configuration. Lower T-boxes typically intersect sparger pipes  10  at a center vertical displacement such that the pipes  10  mate symmetrically with the upper and lower halves of the lower T-box  15 . Upper sparger T-boxes may not intersect the sparger pipes  10  at a center vertical offset due to other structural placement and thus sparger pipes  10  may not symmetrically mate with the upper sparger T-box. 
         [0007]    The cover plate weld  25  and sparger pipe welds  26  are susceptible to cracking due to the high temperature, high pressure, and variable chemistry water flowing around the T-box  15 . Resulting damage to welds  25  and  26  may be accessible for repair and inspection within a BWR only during scheduled plant outages for refueling and repair. These outages typically occur at several month intervals, and thus components within the core, including welds  25  and  26 , must remain intact for lengthy periods before being inspected and/or repaired. 
         [0008]    Further, BWR core operating conditions include high levels of radioactivity due to fission occurring in the fuel rods. Radioactivity, particularly the neutron flux generated in an operating nuclear reactor core, degrades the material strength and elasticity of core components over time. Components within the core, including welds  25  and  26 , are thus subject to premature brittling and cracking due to this radiation exposure. Accordingly, flow-induced vibration, lengthy operating cycles, and demanding water conditions coupled with radiation can cause the welds  25  and  26  to crack, particularly, by intergranular stress corrosion cracking. If cracks in welds  25  and  26  propagate circumferentially so as to completely disunion either the cover plate  20  or the sparger pipes  10  from the sparger T-box  15 , uncontrolled cooling water leakage may result. 
         [0009]    Further compounding the precarious nature of the sparger T-box welds  25  and  26  is their arrangement within the shroud among other components. Even during repair phases, workers may have only remote access to the sparger T-box  15  inside the shroud, and locating and repairing welds on the T-box may require increased expense, removal of other components, and worker hazards. 
         [0010]    Related art sparger T-box repairs and clamps may use clamping mechanisms to relieve stress on welds  25  and  26  and provide redundant security in the case of weld failure. Sparger T-boxes  15  may have various physical configurations based on their particular plant installation and repair history. Related art repair mechanisms are generally configured for only a single sparger T-box in a particular BWR and are incompatible with other sparger T-boxes in other BWRs. 
       SUMMARY 
       [0011]    Example embodiments are directed to core spray sparger T-box repairs, specifically, to universal core spray sparger T-box weldless clamps having remote-friendly operation and methods of using universal core spray sparger T-box weldless clamps. Example embodiment clamps may be secured without welding to a variety of upper and lower sparger T-box configurations. Example embodiment clamps may be configured to simultaneously engage a sparger T-box in multiple dimensions to allow a universal fit. Further, example embodiment clamps may be accessed, installed, or removed by interacting only with a front side of the example embodiment clamps, thus potentially reducing difficulty and cost in remote access repairs to example clamps. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0012]    Example embodiments will become more apparent by describing, in detail, example embodiments thereof with reference to the attached drawings, wherein like elements are represented by like reference numerals, which are given by way of illustration only and thus do not limit the example embodiments herein. 
           [0013]      FIG. 1  is an illustration of related art BWR sparger pipes with a lower sparger T-box mated to the sparger pipes. 
           [0014]      FIGS. 2 and 3  are isometric views of example embodiment core spray sparger T-box clamp assemblies installed on lower and upper sparger T-boxes, respectively. 
           [0015]      FIG. 4  is an exploded view of an example embodiment sparger T-box clamp assembly. 
           [0016]      FIG. 5  is a front elevation view of the anchor plate and clamping structures. 
           [0017]      FIG. 6  is a cross-sectional view of an example embodiment anchor plate and clamping structures useable in example embodiment clamp assemblies. 
           [0018]      FIG. 7  is an isometric view of an example slider wedge useable in example embodiment clamps. 
           [0019]      FIG. 8  is an isometric view of an example slide latch useable in example embodiment clamps. 
           [0020]      FIG. 9  is an isometric view of an example anchor plate useable in example embodiment clamps. 
           [0021]      FIG. 10  is a front elevation and cross-sectional view of the example embodiment clamps in the installed configuration. 
           [0022]      FIG. 11  is a flow chart of example methods for using a core spray sparger T-box clamp assembly. 
           [0023]      FIG. 12  is an illustration of BWR sparger pipes and T-box after forming slots and holes in accordance with example methods. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIGS. 2 and 3  are isometric views of example embodiment core spray sparger T-box clamp assemblies  100  and  200  that may attach to the lower and upper sparger T-boxes  15  and  16 , respectively, and sparger pipes  10  on either side of each sparger T-box. Example embodiment clamp assemblies  100  and  200  may reinforce and provide redundancy to the welds  25  and  26  (shown in  FIG. 1 ) between the T-box and the cover plate and sparger pipes. The example embodiment clamp assemblies  100  and  200  may hold the pipes  10  and the cover plate  20  (shown in  FIG. 1 ) to the sparger T-boxes  15  and  16  and thus relieve stress on welds  25  and  26  (shown in  FIG. 1 ) and prevent or minimize coolant leakage from the welds  25  and  26  in the event of a full circumferential crack. 
         [0025]    Example embodiments are described hereinafter with respect to the lower core spray sparger T-box clamp assembly  100 . Upper clamp assembly  200  may have shared characteristics with the lower clamp assembly  100 , and thus redundant descriptions are omitted. 
         [0026]      FIG. 4  is an exploded view of the example embodiment clamp assembly  100  in  FIG. 2 . As shown in  FIG. 4 , the example clamp assembly  100  includes an anchor plate  110  between two sparger pipe supports  115  and  116 . The anchor plate  110  may be in front of the sparger T-box  15  (as shown in  FIG. 2 ) and shaped to substantially match and cover and/or overlap the sparger T-box  15  and cover plate  20  (shown in  FIG. 1 ). The sparger pipe supports  115  and  116  engage and support the left and right sparger pipes  10  on either side of the sparger T-box  15  via, for example, inner and outer T-bolts  121  and  122 . The anchor plate  110  and sparger pipe supports  115  and  116  may be located in any relative position to match the configuration of various sparger T-boxes. For example, upper sparger T-boxes may be vertically offset from the sparger pipes  10 , and the anchor plate  110  and sparger pipe supports  115  may be similarly offset to match the upper sparger T-box in that case. 
         [0027]    The anchor plate  110  and sparger pipe supports  115  and  116  are connected by a dovetail joint that permits the sparger pipe supports  115  and  116  to translate relative to the anchor plate in an axial direction but prevents translation in a transverse direction along the length of the pipe supports  115  and  116 . In this way, the anchor plate  110  and pipe supports  115  and  116  may be secured independently against the sparger T-box and sparger pipes, respectively. Further, the dovetail joints allow the anchor plate  110  and pipe supports  115  and  116  to be installed at different displacements in the axial direction to accommodate different sparger T-box and pipe configurations. 
         [0028]    First described are example structures for attaching example embodiment clamps to the sparger pipes, specifically, for attaching the sparger supports  115  and  116  to the sparger pipes  10 . 
         [0029]    In an example embodiment, the sparger pipe supports  115  and  116  may be attached to the sparger pipes  10  by inner and outer T-bolts  121  and  122 , which may be secured to the supports  115  and  116  by T-bolt nuts  131  and  132 . The T-bolts  121  and  122  may extend through apertures  50  (shown in  FIG. 12 ) created in the sparger pipes  10  by, for example, electric discharge machining. A threaded end of each T-bolt  121  and  122  may extend through the pipe support  116 . Sealing collars  141  and  142  may interface with the sparger pipe around the aperture  50  in order to prevent leakage of coolant through the aperture  50 . The T-bolt nuts  131  and  132  may screw onto the threaded ends of corresponding T-bolts  121  and  122 . The head of each T-bolt  121  and  122  may have a keyed shape, for instance a rectangular shape, that allows the T-bolt to slide into a corresponding aperture  50 . The T-bolt may then be rotated and thus locked in the sparger pipe  10 . 
         [0030]    Sealing collars  141  and  142  may be placed on the T-bolts  121  and  122  such that as the T-bolt nuts  131  and  132  are tightened, the collars  141  and  142  may be seated against the exterior curved surfaces of the sparger pipes  10 . The sparger pipe support  115  and  116  may have recesses and holes to allow the T-bolts  121  and  122 , T-bolt nuts  131  and  132 , and sealing collars  141  and  142  to pass through the pipe supports  115  and  116  and/or seat against them. 
         [0031]    Ratchet springs  125  may be placed into adjoining slots in the sparger pipe supports  115  and  116  to allow only one-way rotation of the T-bolt nuts  131  and  132 . For example, ratchet springs  125  may allow only tightening of the T-bolt nuts  131  and  132 . The ratchet springs  125  may be keyed to allow disengagement from the T-bolt nuts  131  and  132  and permit two-way rotation of the nuts  131  and  132 . For example, the ratchet springs  125  may be keyed to disengage and allow removal of the sparger pipe supports  115  and  116 . 
         [0032]    Although example embodiments and example structures for attaching example embodiment clamps to sparger pipes have been described as having sparger pipe supports  115  and  116  joined to sparger pipes  10  through a T-bolt  121 , T-bolt nut  131 , and sealing collar  141 , other fastening structures are useable with example embodiments. For example, the sparger pipe supports may be attached to the sparger pipes by welding and/or gripping fasteners around the circumference of a sparger pipe as would be known to one skilled in the art. 
         [0033]    Second described is a unique example clamp for securing example embodiment clamp assemblies to sparger T-boxes of varying configurations. 
         [0034]    Because example embodiment assembly clamp assemblies include dovetail joints that permit axial movement between the anchor plate  110  and sparger pipe supports  115  and  116 , the anchor plate  110  is independently clamped to the sparger T-box. Sparger T-boxes may have variety of configurations and front plate structures, and example embodiments provide a unique universal, front-accessible clamping mechanism for attaching to sparger T-boxes despite diverse front and dimensional characteristics. 
         [0035]    As shown in  FIG. 4 , example clamp assemblies include a central post  151 , a ratchet nut  152 , a slider wedge  153 , a ratchet nut lock  154 , a pair of slide latches  155 , and/or four flat-head screws  156 . These structures allow example embodiment clamp assemblies to engage a variety of sparger T-boxes securely and removably. 
         [0036]      FIGS. 5 and 6  illustrate the latching structures described in  FIG. 4 .  FIG. 6  is a cross-section along the line V-V in  FIG. 5 . As shown in  FIG. 6 , the anchor plate  110  may have a rectangular recessed area  111  that accommodates a rectangular end of the central post  151 . The central post  151  may be prevented from rotating within the recessed area  111  due to the rectangular shape. The recessed area  111 , however, may permit the central post  151  to translate within the recessed area  111  and thus re-center the anchor plate  110  to accommodate irregular T-box geometries. Such accommodation is discussed below in greater detail. 
         [0037]    The ratchet nut  152  and ratchet nut lock  154  are placed on the other end of the central post  151  opposite the rectangular end. The outer surface of the ratchet nut  152  engages the inner surface of the ratchet nut lock  154  so as to permit rotation of the ratchet nut  152  in one direction only. As the ratchet nut  152  rotates, its inner surface engages threads on the end of the central post  151 , drawing the ratchet nut  152  along the central post  151  in an axial direction. For example, the ratchet nut lock  154  may permit rotation of the ratchet nut  151  only in a direction corresponding to the ratchet nut  151  tightening down onto the central post  151  axially. 
         [0038]    The ratchet nut lock  154  may include a release  158 , which may be a hole permitting a tool to be passed into it that disengages the ratchet nut lock  154  from the ratchet nut  152 , allowing rotation of the ratchet nut  152  in any direction, including tightening and loosening along the central post  151 . 
         [0039]    The slider wedge  153  is within, but not completely confined by, the ratchet nut  152 , and the central post  151  passes through the slider wedge  153 . The slider wedge  153  is not rigidly attached to the ratchet nut  152 . Instead, the slider wedge  153  and ratchet nut lock  154  are rigidly fixed together by, for example, flat-head screws  156  passing through the ratchet nut lock  154  and slider wedge  153 . The slider wedge  153  and ratchet nut lock  154  may be held stationary by slide latches  155  that are mated with the stationary sparger T-box. In this way the ratchet nut  152  may rotate and move axially along the central post  151 , but the ratchet nut lock  154  and slider wedge  153  translate only axially, and do not rotate, with the ratchet nut  152 . 
         [0040]      FIG. 7  is an isometric view of a slider wedge  153  useable in example embodiments.  FIG. 8  is an isometric view of slide latches  155  useable in example embodiments. As shown in  FIG. 8 , slide latches  155  may have an angled end  165  and a conical end  166 . The angled end  165  may mate with the angled inner surface  163  of the slider wedge  153  shown in  FIG. 7 . As shown in  FIG. 6 , the angled ends  165  may fit within the angled inner surface  163  and prevent rotation of the slider wedge  153  as long as the slide latch  155  cannot rotate. As the slider wedge  153  is translated axially along the central post  151 , the slide latches  155  may be drawn inward radially due to the mating of the angled inner surface  163  and the angled ends  165 . As the conical ends  166  are held stationary and/or impeded from further radial movement, the slider wedge  153  may not move the slide latches  155  inward radially any further, and the slider wedge  153  and ratchet nut  152  may not be further tightened along the central post  151 . 
         [0041]      FIG. 9  shows the anchor plate  110  in greater detail, including a T-shaped slot  112  across the face of the anchor plate  110 . The slot  112  allows the slide latches  155  to be fixed with the anchor plate  110  and prevents rotation of the slide latches  155 , the ratchet nut lock  154 , and/or slider wedge  153  to which the ratchet nut lock  154  is mated. The slot  112 , however, permits the slide latches  155  to move radially inward and outward as they are tightened against the sparger T-box. Further, the direction of the slot  112  may match an orientation of the recessed area  111  on the opposite side of the anchor plate  110  (shown in  FIGS. 5 and 6 ). In this way, the central post  151  may translate relative to the recessed area  111  only in a direction corresponding to the slot  112  direction and slide latch  155  orientation. Thus, if the anchor plate  110  and central post  151  are not initially centered between the exterior of a sparger T-box, the central post can translate due to clamping force from the slide latches  155  to a position centered between the slide latches  155 . In this way example embodiment clamp assemblies may accommodate different or uneven outer geometries of sparger T-boxes without unevenly attaching to the sparger T-box. 
         [0042]      FIG. 10  shows the same example embodiment clamp assembly as  FIGS. 5 and 6 , but with the ratchet nut  152 , ratchet nut lock  154 , and slider wedge  153  advanced further axially along the central post  151 . As shown in  FIG. 10 , the slide latches  155  have been drawn radially inward due to the axial translation of the slider wedge  153 . 
         [0043]    The conical end  166  of slide latch  155  may engage a hole  60  in the sparger T-box  15  (shown in  FIG. 12 ). The hole  60  may be formed by any known method including, for example, electric discharge machining. Once the conical end  166  is fully seated into the hole  60 , the latch may not be translated inward radially further, and tightening of the ratchet nut bolt may be impeded or stopped. 
         [0044]    Example clamps for securing example embodiment clamp assemblies to sparger T-boxes of varying configurations having been described, it will be apparent to those skilled in the art that departure from these examples by routine experimentation to accommodate other configurations is possible. For example, the shape of ends  166  of slide latches  155  need not be conical or engage T-boxes in a single area; rather, any equivalent structure that allows the slide latches  155  to engage the sparger T-box may be substituted. Similarly, screws need not be used to secure the slider wedge to the ratchet nut lock and T-shaped slots are not required to prevent the slide latches from rotating. Rather, any structure for mating the slider wedge, ratchet nut lock, and slide latches may be implemented. 
         [0045]    These example structures offer an example embodiment clamp assembly may be secured to the body of the sparger T-box of divergent configuration, and how installation and removal may be achieved through a single face-accessible nut structure. 
         [0046]    Thirdly, example embodiment clamp assemblies may also include structures that seat against the cover plate  20  to provide support to weld  25  and prevent potential coolant leakage should weld  25  fail. 
         [0047]    As shown in  FIG. 4 , example embodiment clamp assemblies may include a bearing plate  160 , bearing plate bolts  161 , and latch springs  162 . The bearing plate  160  may be biased against the cover plate  20  and may secure the cover plate  20  in the event weld  25  fails. The bearing plate  160  may be connected to the anchor plate  110  by bearing plate bolts  161  that extend through threaded holes  113  in the anchor plate  110  (shown in  FIG. 9 ). The bearing bolts  161  may rotate to move the bearing plate  160  toward the T-box cover plate  20 . Latch springs  162  may lock the rotational position of the bearing plate bolts  161  to ensure that force applied to the cover plate  20  by the bearing plate  160  does not lessen over a prolonged operation period. The latch springs  162  may seat in respective slots on the face of the anchor plate  110  and may be disengaged by a key structure that disengages the latch springs  162  from the bolts  161  to allow rotation of the bolts in either direction. 
         [0048]    Example methods for operating core spray sparger T-box clamp assemblies are described with reference to  FIGS. 11 and 12 .  FIG. 11  is a flow chart of an example method for operating a core spray sparger T-box clamp. As shown in  FIG. 11 , in optional step S 10 , slots and holes may be formed in existing sparger pipes and sparger T-boxes. The slots and holes may be placed in any configuration so as to permit a clamp assembly to engage and clamp to sparger pipes and sparger T-boxes. For example, slots may be machined into the sparger pipes and holes may be machined into opposite sides of the sparger T-box. Any known process of forming these holes and slots may be used, including electric discharge machining. 
         [0049]      FIG. 12  shows an example of step S 10  with slots  50  and holes  60  machined into the sparger pipes  10  and sparger T-box  15 , respectively. 
         [0050]    As shown in step S 20 , an anchor plate may be clamped to the sparger T-box. Such clamping may be performed solely by rotational tightening on the face of the clamping mechanism and may accommodate a wide variety of sparger T-box configurations. The clamping may also center the clamping assembly between the clamped areas of the sparger T-box. 
         [0051]    As shown in step S 30 , sparger pipe supports may be attached to the sparger pipes so as to secure the sparger pipe supports to the sparger pipes. The supports may secure the sparger pipes in transverse directions parallel to the supports only. Securing the sparger pipe supports may include tightening the sparger pipe supports on only the face of the sparger supports. 
         [0052]    The clamp assembly may be secured against the sparger T-box cover by tightening on the face of the anchor plate. As such, all example methods require only access to the face of clamping assemblies in order to operate the clamping assemblies; however, access to other sides and/or aspects of clamping assemblies may be allowed by example methods. 
         [0053]    As shown in step S 40 , a bearing plate may then be biased against a cover plate of the sparger T-box. 
         [0054]    Example embodiments and methods thus being described, it will be appreciated by one skilled in the art that example embodiments and example methods may be varied through routine experimentation and without further inventive activity. Variations are not to be regarded as departure from the spirit and scope of the exemplary embodiments, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.