Abstract:
An apparatus for measuring perpendicularity of an upper tie plate of a nuclear fuel bundle includes a first comb having a first plurality of teeth; a second comb having a second plurality of teeth, the second comb being parallel to and spaced from the first comb; a comb connector that connects the first comb to the second comb, the comb connector having a second end extending beyond the first comb; a rigid finger provided at the second end of the comb connector; a rotatable gage provided on the second comb; and a mobile finger operatively connected to the gage.

Description:
[0001]    The present invention relates to an apparatus and method for measuring and for setting the perpendicularity of an upper tie plate of a nuclear fuel bundle. 
       BACKGROUND OF THE INVENTION 
       [0002]    On a BWR fuel bundle, the upper tie plate (UTP) must be set perpendicular to the bundle&#39;s fuel rods to allow unrestricted rod growth during irradiation and to ensure an even load on each of the tie rod upper end plugs, which are used to support the bundle during lifting and/or for moving the nuclear fuel bundle around. Currently available UTP perpendicularity gages and set blocks have many issues that cause difficulty in achieving repeatable measurements. The currently available UTP perpendicularity gages yield unrepeatable measurements, even using a single inspector and a single gage. 
         [0003]    The currently available UTP perpendicularity gages measure the perpendicularity of the UTP with respect to a single rod within the nuclear fuel bundle. If that fuel rod is bowed, the UTP is repeatedly set incorrectly without taking into consideration the many other fuel rods within the same bundle. The currently available gages are also difficult to use on the bundle sides while the bundle is in the horizontal position. 
         [0004]    Additionally, because the single rod being measured is flexible, the inspector can inadvertently rotate or twist the gage handle slightly and the rod the gage rides upon can be moved, yielding an inaccurate perpendicularity reading. Tolerances on the UTP perpendicularity are typically small, e.g. ±0.007 in., and it is easy for two or more people to achieve readings that are different when measuring the same piece. All of these gage issues yield a very technique-driven gage and a high potential for operator error during usage. 
         [0005]    Furthermore, the UTP perpendicularity is set while the nuclear fuel bundle is horizontal on the assembly table. In this position, the last support block under the nuclear fuel bundle lies 24-26 inches from the UTP allowing the bundle head to droop a minimum of 0.125 inches due to the weight of the UTP and flexibility of the rods. With the thinner cladding of some nuclear fuel rods, this becomes even more of an issue. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    According to one embodiment, an apparatus for measuring perpendicularity of an upper tie plate of a nuclear fuel bundle comprises a first comb having a first plurality of teeth; a second comb having a second plurality of teeth, the second comb being parallel to and spaced from the first comb; a comb connector that connects the first comb to the second comb, the comb connector having a second end extending beyond the first comb; a rigid finger provided at the second end of the comb connector; a rotatable gage provided on the second comb; and a mobile finger operatively connected to the gage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic illustration of a nuclear fuel bundle; 
           [0008]      FIG. 2  is a schematic illustration showing part of an upper tie plate perpendicularity measurement system according to an embodiment of the invention as seen from a top perspective; 
           [0009]      FIG. 3  is a schematic illustration showing part of the upper tie plate perpendicularity measurement system according to an embodiment of the invention as seen from a bottom perspective; 
           [0010]      FIG. 4  is a schematic plan view of a set block usable with the upper tie plate perpendicularity measurement system; 
           [0011]      FIG. 5  is a schematic illustration showing part of the upper tie plate perpendicularity measurement system and the set block; 
           [0012]      FIG. 6  is a schematic illustration showing part of the upper tie plate perpendicularity measurement system, resting upon, and a nuclear fuel bundle. 
           [0013]      FIG. 7  is a schematic side elevation view of a semi-automated bundle assembly device in the up position; 
           [0014]      FIG. 8  is a schematic side elevation view of the semi-automated bundle assembly device in the down position; and 
           [0015]      FIG. 9  is a schematic front elevation view of the automated bundle assembly machine. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    Referring to  FIG. 1 , a nuclear fuel bundle  2  comprises a channel  4  encompassing an upper tie plate  6  and a lower tie plate  8 . Within the channel  4  there is provided a plurality of nuclear fuel rods  10  and a pair of water rods  27  supported on the lower tie plate  8 . The nuclear fuel rods  10  extend upwardly toward and to the upper tie plate  6 . A plurality of spacers  12 ,  14 ,  16  are vertically spaced one from the other throughout the height of the nuclear fuel bundle  2  and define discrete, vertically aligned openings at lattice positions in a regular array of such openings to receive and confine the rods  10  within the nuclear fuel bundle  2  against lateral movement relative to one another. It should be appreciated that, generally, eight or nine spacers are provided, although only three spacers  12 ,  14 ,  16  are illustrated. 
         [0017]    It will be appreciated that  FIG. 1  illustrates a 9×9 array of nuclear fuel rods  10 , but that other arrays may be utilized with the present invention, e.g., 8×8 or 10×10 arrays. A handle  18  is integrated into the top portion of the upper tie plate  6 , and provides a means for lifting and moving the nuclear fuel bundle  2  relative to a nuclear fuel core (not shown). 
         [0018]    In utilizing the nuclear fuel bundle  2  in the core of a nuclear reactor, for example a BWR, coolant/moderator, e.g., water, enters through the lower tie plate  8  for flow upwardly and about the rods  10 . During upward passage of this water, steam is generated and a vapor and liquid mixture passes upwardly through the upper tie plate  6 . During steam generation, the channel  4  confines the coolant/moderator flow within the nuclear fuel bundle  2  and isolates that flow from a core bypass volume flowing outside the channel  4  and between similarly disposed fuel bundles. 
         [0019]    As shown in  FIG. 1 , not every lattice position of the lattice or array of openings across the spacers  12 ,  14 ,  16  is occupied by a full-length fuel rod  10 . For example, one or more water rods  27  or moderator rods may pass upwardly through the central portion of the nuclear fuel bundle  2  and occupy a number of lattice positions. Additionally, one or more part-length rods  20  may be provided in selected lattice positions in the nuclear fuel bundle  2 . Thus, for example, each part-length rod  20  may extend from the lower tie plate  8  upwardly in the fuel bundle through a spacer, for example the spacer  12 , and terminate just above the spacer  12 . Part-length rods  20  are typically terminated just above the spacer to provide support for the otherwise cantilevered ends of the part-length rod. 
         [0020]    Referring to  FIG. 2 , an upper tie plate perpendicularity gage  22  comprises a first comb  24  and a second comb  26  connected by a comb connector  30 . A handle  32  on the upper tie plate perpendicularity gage  22  is provided along the comb connector  30  for ease of usage. The second comb  26  supports a dial indicator gage  34  that is operatively connected to a mobile finger  38 . It should be appreciated that the gage  34  may be a digital gage. The mobile finger  38  is pivotally connected to the dial indicator gage  34  and has a generally L-shaped configuration. At the end of the comb connector  30 , a rigid finger  36  is provided and secured to the comb connector  30 . First fasteners  29  may be used to secure the handle  32  to the comb connector  30 , and the first and second combs  24 ,  26  are assembled and secured to the framework of the upper tie plate perpendicularity gage  22  by first fasteners  29  as well as dowel pins  25 . 
         [0021]    A rotational locking thumbscrew  35  may be provided to the dial indicator gage  34  to allow the operator/inspector to rotate the dial indicator gage  34  with respect to the second comb  26 . A button  33  may also be provided to the dial indicator gage  34  to permit the operator/inspector to save measurements made by the dial indicator gage. The dial indicator gage  34  may comprise a memory that is configured to save certain data. Data may be entered and removed from the dial indicator gage by, for example, a USB cable. Data such as the name of the operator/inspector, date and time, location, etc. may be entered into the memory of the dial indicator gage. The operator/inspector may depress the button  33  to save measurements made by the dial indicator gage  34 . The measurements saved in the memory may be correlated to the other information saved in the memory so that it is possible to determine, for example, the time and date and/or location that the measurements were taken, and/or the operator/inspector that took the measurements. 
         [0022]    As shown in  FIG. 3 , the first and second combs  24 ,  26  comprise teeth  40  that are configured to encompass a fuel rod  10  of a nuclear fuel bundle  2  between adjacent teeth  40 . The teeth  40  may comprise, for example, pins that are light press fit into the combs. The first and second combs  24 ,  26  also comprise indentations  42  that are configured to encompass a datum fuel rod location that aligns with an upper tie plate datum point(s). 
         [0023]    The upper tie plate perpendicularity gage  22  encompasses all of the nuclear fuel rods  10  (slightly beyond each of the rod&#39;s centerline) on a single side of the nuclear fuel bundle  2 . The upper tie plate perpendicularity gage  22  will take into consideration all of the fuel rods on a single side of the nuclear fuel bundle  2  when measuring the perpendicularity of the upper tie plate  6 , thus eliminating problems caused by rod bow and/or operator or inspector bias caused by inadvertently rotating the handle  32  of the upper tie plate perpendicularity gage  22 . 
         [0024]    The first and second combs  24 ,  26  are spaced to capture more of the rod length than current gages. The increased distance between the first and second combs  24 ,  26  allows for more accurate upper tie plate perpendicularity measurements. In addition, the first and second combs  24 ,  26  add stability during measurements of the sides of the nuclear fuel bundle  2  while the nuclear fuel bundle  2  is on a horizontal bundle assembly table. The first and second combs  24 ,  26  support the weight of the dial indicator gage  34  by resting on the rods of the bundle  2  and prevent the weight of the upper tie plate perpendicularity gage  22  from becoming an impedance. 
         [0025]    Before the upper tie plate perpendicularity gage  22  can be used, it must be zeroed on a set block  44 , which along with the upper tie plate perpendicularity gage  22  has to be certified as meeting all of the engineering and product requirements, shown in  FIG. 4 . If, after placing the upper tie plate perpendicularity gage  22  upon the set block  44  and the dial indicator gage  34  does not zero, then a certified gage technician is required to make an adjustment using a fine adjustment point  37  on the dial indicator gage  34 , to re-zero the gage to the set block  44  prior to usage. The set block  44  comprises a guide plate  52  and datum rods  48 . A zero set plate  46  is provided at an end of the guide plate  52  and a side guide  50  is provided along a side of the guide plate  52 . Second fasteners  45  and dowel pins  39  may be provided to secure the zero set plate  46 , the datum rods  48 , and the side guide  50  into place and upon the guide plate  52 . Third fasteners  47  may be provided through the guide plate  52  to act as supports, or feet, for the set block to maintain the stability of the set block  44  during the certification of the gage. It should also be appreciated that the fasteners may be fastened to, for example, rubber feet. It should also be appreciated that the fasteners may be, for example, threaded fasteners, or projections fastened to the guide plate  52 . 
         [0026]    Referring to  FIG. 5 , the upper tie plate perpendicularity gage  22  is placed on the set block  44  so that the indentations  42  of the first and second combs  24 ,  26  are resting on the datum rods  48  and the rigid finger  36  and the mobile finger  38  are pointed towards the zero set plate  46 . The upper tie plate perpendicularity gage  22  is slid toward the zero set plate  46  allowing the two fingers  36 ,  38  to touch the zero set plate  46  until the upper tie plate perpendicularity gage  22  is fully seated. At this point, the fingers  36 ,  38  measure a plane that is exactly perpendicular to the datum rods  48  and the operator/inspector can verify that the dial indicator gage  34  is reading zero, otherwise a certified gage technician is required to make an adjustment using the fine adjustment point  37  on the dial indicator gage  34 , as necessary to obtain a zero reading, prior to making any measurements. 
         [0027]    Referring to  FIG. 6 , in order to measure the perpendicularity of the upper tie plate  6 , the upper tie plate perpendicularity gage  22  is pressed against the fuel rods  10  of the nuclear fuel bundle  2  with the fingers  31  of the operator/inspector pointing towards the upper tie plate  6 . Once the upper tie plate perpendicularity gage  22  is seated on the nuclear fuel bundle  2 , it is slid upward toward the upper tie plate&#39;s bottom surface until the rigid finger  36  and the mobile finger  38  touch the upper tie plate datum  59 , i.e. protruding pieces on the sides of the upper tie plate  6 . Loosening the dial indictor gage&#39;s rotational locking thumbscrew  35  will allow the operator/inspector to read the dial indicator gage  34  from any angle, for a more accurate reading without producing a parallax effect. The rigid finger  36  sets the position of the upper tie plate perpendicularity gage  22  and the mobile finger  38 , operatively connected to the dial indicator gage  34 , is allowed to move up or down according to the position of the left datum stop with relation to the right datum stop. If the left datum stop is higher than the right datum stop, the dial indicator gage  34  will yield a positive reading, and vice versa. Based on the reading of the dial indicator gage  34 , the hex nuts  28  (see  FIG. 6 ) attached to each of the tie rods  11 , on top of the upper tie plate  6 , can be adjusted to change the perpendicularity of the upper tie plate  6  prior to installation of the lock tabs  9 . The upper tie plate  6  is determined to be perpendicular when a zero gage reading is obtained on the dial indicator gage  34  on each of the four bundle sides. It should appreciated, however, that only three sides can be measured when the bundle is on the horizontal bundle assembly table, while all four sides are required to be re-verified at the final inspection stand. 
         [0028]    Referring to  FIGS. 7-9 , a semi-automated bundle assembly rod lifting device  56  supports the nuclear fuel bundle  2  at the ends of the nuclear fuel rods to bring up the level of the rod&#39;s upper end plug and the upper tie plate  6  to be aligned with the rest of the nuclear fuel bundle  2 . The opposite end of the nuclear fuel bundle  2  is supported by a rod guide support  54 . The semi-automated bundle assembly rod lifting device  56  comprises an off-center toggle drum device  58  that locks in the up position, shown in  FIG. 7 , to raise the end of the nuclear fuel bundle  2  to be perpendicular to the nuclear fuel rods. When in the down position, shown in  FIG. 8 , the rod guide support  54  is low enough to not contact the nuclear fuel rods of the nuclear fuel bundle  2 , or impede assembly. Therefore, the rod guide support  54  can remain on the semi-automated bundle assembly rod lifting device  56  when not in use. 
         [0029]    The semi-automated bundle assembly rod lifting device  56  comprises the off-center toggle drum device  58  that is supported in a bearing  60 . The off-center toggle drum device  58  may be moved from the up position shown in  FIG. 7  to the down position shown in  FIG. 8  by a lift roll (or drum) lever, or toggle,  66 . The lift roll lever, or toggle,  66  is in contact with an up stop  64  in the up position shown in  FIG. 7  and in contact with a down stop  62  shown in a down position of  FIG. 8 . Fourth fasteners  65  are used to secure the semi-automated bundle assembly rod lifting device  56  and to fasten the semi-automated bundle assembly rod lifting device  56  to the rod guide support  54 . 
         [0030]    The upper tie plate perpendicularity gage allows repeatability of the upper tie plate perpendicularity measurements and reduces operator/inspector variability among measurements. The upper tie plate perpendicularity gage also allows consideration of all of the fuel rods of the nuclear fuel bundle on a single side for perpendicularity measurement, rather than consideration of just one rod. 
         [0031]    The semi-automated bundle assembly rod lifting device includes the rod guide support for supporting the end of the bundle when setting the upper tie plate to ensure accurate setting of the upper tie plate. The upper tie plate perpendicularity gage is robust and may be used to inspect the upper tie plate perpendicularity in the bundle inspection stand and at a customer site. 
         [0032]    The upper tie plate perpendicularity gage may also be used to inspect additional future fuel bundle designs. The distance between the two combs of the upper tie plate perpendicularity gage capture more of the rods overall length and add stability during measurements of the bundles sides while the bundle is on the horizontal bundle assembly table, and during a vertical inspection at the inspection stand, due to the multi-rod comb gage design. 
         [0033]    The upper tie plate perpendicularity gage may also be used with little or no training required for both domestic and international customers to allow for correct usage of the gage. 
         [0034]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.