System and method for aligning nuclear reactor tubes and end fittings using tube geometry

Abstract

A method for positioning a calandria tube within a calandria vessel of a nuclear reactor. The method includes determining a restrained bow of the calandria tube; determining an unrestrained bow of the calandria tube; calculating a vector sum of the restrained bow of the calandria tube and the restrained bow of the calandria bow; and positioning the calandria tube with respect to the nuclear reactor to orient the vector sum in an operational position.

Description

SYSTEM AND METHOD FOR ALIGNING NUCLEAR REACTOR TUBES AND END FITTINGS USING TUBE GEOMETRY CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims all benefit including priority to United States Provisional Patent Application 62 / 524,418, filed June 23, 2017, and entitled "SYSTEM AND METHOD FOR ALIGNING NUCLEAR REACTOR TUBES AND END FITTINGS USING TUBE GEOMETRY". FIELD

[0002] The present disclosure relates to the field of nuclear reactor fuel channel assemblies and some embodiments relate to methods and systems for positioning calandria tubes and pressure tubes within a nuclear reactor fuel channel assembly. BACKGROUND

[0003] Nuclear reactors are designed to have an operational lifespan. For example, second generation CANDUTM-type reactors ("CANada Deuterium Uranium") can be designed to operate for approximately 25 to 30 years. After this time, the existing fuel channels can be removed and fuel channels can be installed.

[0004] Properly aligning fuel channel components which can include positioning elongated tubes into existing apertures or bores can be a challenge. SUMMARY

[0005] In one embodiment, the disclosure provides a method for positioning a calandria tube within a calandria vessel of a nuclear reactor. The method includes determining a restrained bow of the calandria tube; determining an unrestrained bow of the calandria tube; calculating a vector sum of the restrained bow of the calandria tube and the restrained bow of the calandria tube at a specific axial location along the calandria tube and positioning the calandria tube with respect to the nuclear reactor to orient the vector sum in an operational position.

[0006] In another embodiment, the disclosure provides a method for positioning a calandria tube within a calandria vessel of a nuclear reactor. The method includes determining a bow of the of the calandria tube; orienting the calandria tube so that the bow is in a generally upward orientation; and orienting a subassembly including a pressure tube and a first end fitting with respect to a second end fitting positioned within a bore of a tube sheet positioned at a reactor face. The first end fitting is engaged with a first bore of a first tube sheet and the pressure tube is positioned within the calandria tube. The method further includes the steps of exerting a downward force on the first end fitting; and securing the calandria tube in an operational position.

[0007] In another embodiment, the disclosure provides A method for positioning a calandria tube within a calandria vessel of a nuclear reactor. The method includes determining a restrained bow of the calandria tube; determining an unrestrained bow of the calandria tube; calculating an alignment angle between a vector angle of the restrained bow of the calandria tube and a vector angle of the unrestrained bow of the calandria tube at an axial location; and positioning the calandria tube with respect to the nuclear reactor to orient the alignment angle in an operational position.

[0008] Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a perspective view of a CANDUTM-type reactor.

[0010] FIG. 2 is a cutaway view of a CANDUTM-type reactor fuel channel assembly.

[0011] FIG. 3 is a side-cutaway view of the entire fuel channel assembly, showing droop.

[0012] FIG. 4 is a side-cutaway view of a pressure tube of the fuel channel assembly showing an orientation of the pressure tube with respect to an end fitting according to some embodiments.

[0013] FIG. 5 is a side cut-away view of the sub-assembly end of the fuel channel assembly, showing a mis-alignment measurement tool installed to measure mis-alignment amount.

[0014] FIG. 6 is a flow chart illustrating an installation process for installing a calandria tube in the reactor according to an embodiment of the disclosure.

[0015] FIG. 7 is a side cut-away view of the entire fuel channel assembly showing the forces exerted based on the installation process of Fig. 6.

[0016] FIG. 8 is a flow chart illustrating an installation process for installing a calandria tube in the reactor according to another embodiment of the disclosure.

[0017] FIG. 9 is a side cut-away view of the entire fuel channel assembly showing the forces exerted based on the installation process of Fig. 8.

[0018] FIG. 10 shows example views of an unrestrained and a restrained calandria tube.

[0019] FIG. 11 shows example views of unrestrained and restrained bows of a calandria tube.

[0020] FIG. 12 is a vector diagram illustrating restrained, induced and free bow.

[0021] FIG. 13 shows example mechanisms for measuring bows.

[0022] FIG. 14 shows an example restraining fixture.

[0023] FIG. 15 shows a vector diagram illustrating a case where induced bow and free bow are in opposite directions.

[0024] FIG. 16 is a plot showing example theoretical restrained bow profiles.

[0025] FIG. 17 shows a pressure tube with an engaged first end.

[0026] FIG. 18 shows example beam deflection formulas.

[0027] FIG. 19 shows example tube body profiles.

[0028] FIG. 20 shows a pressure tube with an engaged first end and two example target points.

[0029] FIG. 21 shows an example pressure tube bow vector diagram.

[0030] FIG. 22 shows an example pressure tube bow vector diagram.

[0031] FIG. 23 show an example coordinate relationship. DETAILED DESCRIPTION

[0032] Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways.

[0033] FIG. 1 is a perspective of a reactor core of an exemplary CANDUTM-type Pressurized Heavy Water Reactor (PHWR) reactor 6. In some embodiments, the PHWR may be a 100-300 MW CANDUTM reactor, a 600MW CANDUTM reactor, a 900MW CANDUTM reactor, or a 1000 MW CANDUTM reactor. The reactor core is typically contained within a vault that is sealed with an air lock for radiation control and shielding. Although aspects of the disclosure are described with particular reference to the CANDUTM-type reactor 6 for convenience, the disclosure is not limited to CANDUTM-type reactors, and may be useful outside this particular field as well. Returning to FIG. 1, a generally cylindrical vessel, known as the calandria vessel 10 of the CANDUTM-type reactor 6, contains a heavy-water moderator. The calandria vessel 10 has an annular shell 14 and a tube sheet 18 at a first end 22 and a second end 24. The tube sheets 18 include a plurality of apertures (referred to herein as "bores") that each accept a fuel channel assembly 28. As shown in FIG. 1, a number of fuel channel assemblies 28 pass through the tube sheets 18 of calandria vessel 10 from the first end 22 to the second end 24.

[0034] As in the illustrated embodiment, in some embodiments the reactor core is provided with two walls at each end 22, 24 of the reactor core: an inner wall defined by the tube sheet 18 at each end 22, 24 of the reactor core, and an outer wall 64 (often referred to as a "end shield") located a distance outboard from the tube sheet 18 at each end 22, 24 of the reactor core. A lattice tube 65 spans the distance between the tube sheet 18 and the end shield 64 at each pair of bores (i.e., in the tube sheet 18 and the end shield 64, respectively).

[0035] FIG. 2 is a cutaway view of one fuel channel assembly 28 of the reactor core illustrated in FIG. 1. As illustrated in FIG. 2, each fuel channel assembly 28 includes a calandria tube ("CT") 32 surrounding other components of the fuel channel assembly 28. The CTs 32 each span the distance between the tube sheets 18. Also, the opposite ends of each CT 32 are received within and sealed to respective bores in the tube sheets 18. In some embodiments, a CT rolled joint insert 34 is used to secure the CT 32 to the tube sheet 18 within the bores. A pressure tube ("PT") 36 forms an inner wall of the fuel channel assembly 28. The PT 36 provides a conduit for reactor coolant and fuel bundles or assemblies 40. The PT 36, for example, generally holds two or more fuel assemblies 40, and acts as a conduit for reactor coolant that passes through each fuel assembly 40. An annulus space 44 is defined by a gap between each PT 36 and its corresponding CT 32. The annulus space 44 is normally filled with a circulating gas, such as dry carbon dioxide, helium, nitrogen, air, or mixtures thereof. One or more annulus spacers or garter springs 48 are disposed between the CT 32 and PT 36. The annulus spacers 48 maintain the gap between the PT 36 and the corresponding CT 32, while allowing passage of annulus gas through and around the annulus spacers 48.

[0036] As also shown in FIG. 2, each end of each fuel channel assembly 28 is provided with an end fitting 50 located outside of the corresponding tube sheet 18. At the terminal end of each end fitting 50 is a closure plug 52. Each end fitting 50 also includes a feeder assembly 54. The feeder assemblies 54 feed reactor coolant into or remove reactor coolant from the PTs 36 via feeder tubes 59 (FIG. 1). In particular, for a single fuel channel assembly 28, the feeder assembly 54 on one end of the fuel channel assembly 28 acts as an inlet feeder, and the feeder assembly 54 on the opposite end of the fuel channel assembly 28 acts as an outlet feeder. As shown in FIG. 2, the feeder assemblies 54 can be attached to the end fittings 50 using a coupling assembly 56 including a number of screws, washers, seals, and / or other types of connectors. The lattice tube 65 (described above) encases the connection between the end fitting 50 and the PT 36 containing the fuel assemblies 40. Shielding ball bearings 66 and cooling water surround the exterior of the lattice tubes 65, which provides additional radiation shielding. In the illustrated construction, the end fittings 50 are engaged with the ends of the PTs 36. For the purpose of convenience, when referring to specific end fittings 50, the end fitting 50 closest to the reactor face will be indicated with the symbol " " and the end fitting 50 closest to a subassembly side (e.g. the side of the fuel channel assembly 28 farthest from the reactor face) will be indicated with the symbol "".

[0037] Returning to FIG. 2, a positioning hardware assembly 60 and bellows 62 are also coupled to each end fitting 50. The bellows 62 allows the fuel channel assemblies 28 to move axially – a capability that can be important where fuel channel assemblies 28 experience changes in length over time, which is common in many reactors. The positioning hardware assemblies 60 can be used to set an end of a fuel channel assembly 28 in either a locked configuration that fixes the axial position or an unlocked configuration. The positioning hardware assemblies 60 are also coupled to the end shield 64. The illustrated positioning hardware assemblies 60 each include a rod having an end that is received in a bore of the respective end shield 64. In some embodiments, the rod end and the bore in the end shield 64 are threaded. Again, it should be understood that although a CANDUTM-type reactor is illustrated in FIGS. 1-2, the disclosure may also apply to other types of reactors, including reactors having components that are similar to those illustrated in FIGS. 1-2.

[0038] FIG. 3 illustrates a schematic representation of a cross-section of a fuel channel assembly 28 in the operational position according to some embodiments. As shown in FIG. 3, the CT 32 and the PT 36 are largely unsupported along their longitudinal extents when the CT 32 and the PT 36 are installed in the reactor 6. In the operational position, the CT 32 and the PT 36 are generally positioned so that the bows face upward (e.g. the position of maximum bow is downward with respect to the ends of the CT 32 or the PT 36). In some embodiments, orienting the PT 36 so that the bow faces upward reduces bow in the CT / PT combination by approximately <semantics>0.2−0.5<annotation encoding="application / x-tex">0.2 - 0.5< / annotation>< / semantics> microradians. A plurality of garter springs 48 is positioned along the longitudinal extent of the PT 36 to prevent contact between the PT 36 and the CT 32. In embodiment of FIG. 3, the fuel channel assembly 28 includes four garter springs 48. The position of the bow of the CT 32 is generally proximate a third garter spring 48". The position of the bow may be different in other embodiments or in embodiments using more or fewer garter springs 48.

[0039] Positioning the CTs 32 and the PTs 36 is complex due to the shape of the CTs and the PTs. As illustrated in FIG. 10, a calandria tube can include a body and expanded end portions at each end of the body. In some embodiments, the expanded end portions have a larger diameter than the body. In some embodiments, the expanded end portions of the tubes are cylindrical forms which are connected to the body of the tube. Due to the manufacturing process or otherwise, the expanded end portions may have axes which are not perfectly concentric with the axis of the body of the tube. Alternatively or additionally, the axes of the expanded end portions may not be perfectly parallel with the axis of the body of the tube. For example, in the example CT 32A in FIG. 10, the axis of the first extended end portion 1010A and the axis of the body of the tube 1020 are offset by an angle <semantics>ΘA<annotation encoding="application / x-tex">\Theta_A< / annotation>< / semantics>; and the axis of the second extended end portion 1010B and the axis of the body of the tube 1020 are offset by an angle <semantics>ΘB<annotation encoding="application / x-tex">\Theta_{B}< / annotation>< / semantics>.

[0040] When the two expanded end portions 1010A, 1010B are restrained in positions such that the axes of the two expanded end portions are parallel or are substantially coaxial as illustrated in FIG. 10, the imperfect alignment of the expanded end portions in their free state results in a bowing of the calandria tube.

[0041] In some embodiments, the bowing of the calandria tube when the two expanded end portions of the tube are rigidly clamped or otherwise held in positions that are aligned is referred to as restrained bow. In some embodiments, the restrained bow of the tube can be defined when the expanded end portions are secured by fixtures which are positioned a particular distance apart (e.g. 232 inches apart or at a distance at which the expanded end portions would be secured in the fuel channel assembly), and are positioned to be in a particular alignment (e.g. substantially coaxial / concentric, or having an alignment in which the expanded end portions would be secured in the fuel channel assembly).

[0042] With reference to FIG. 11, due to the manufacturing process or otherwise, a calandria tube can have a bow shape when it is in a free state (e.g. when its expanded ends are unrestrained). In some embodiments, this bowing can be referred to as free bow or unrestrained bow.

[0043] When the expanded end portions of the tube are restrained, the resulting bowing is referred to as the restrained bow. As illustrated by FIG. 11, the difference between the restrained bow and the unrestrained bow is the bowing caused by the restraining of the expanded end portions. In some embodiments, this bowing caused by the restraining of the expanded end portions is referred to as induced bow. In other words, the restrained bow is the induced bow plus the free / unrestrained bow. This relationship is illustrated in FIG. 12.

[0044] In some embodiments, components of the restrained bow may be recoverable / reduced when countered by the weight of the tubes. Accordingly, in some situations, it may be beneficial to position a tube in a position where the recovered bow (i.e. the restrained bow and the countering effects of gravity on the tubes).

[0045] The bow shapes of CTs 32 and the PTs 36 in various states (free, restrained, etc.) can be defined with respect to a reference point, such as an axial centerline of the calandria tube. In some instances, a bowed portion of the CT 32 or the PT 36 may be located proximate a center of the CT 32 or the PT 36. In other instances, the bowed portion of the CT 32 or the PT 36 may be off-center, for example closer to one of the ends of the CT 32 or the PT 36, or proximate one of the ends of the CT 32 or the PT 36. A bow of the CTs 32 or a bow of the PTs 36 is generally measured before the CTs 32 or the PTs 36 are installed in the reactor 6 determine a position of the bow in a rotational orientation and an axial location. The term "rotational orientation" is generally used to refer to an angular orientation with respect to a known reference point, such as a "12 o'clock position". The term "axial location" is generally used to refer to a position along a longitudinal extent of the CT 32 or the PT 36. In some embodiments, the PTs 36 include markings to indicate the rotational orientation and / or axial position of the bow. Since the PTs 36 are positioned inside of the CTs 32, the bow of each PT 36 is oriented rotationally and axially with respect to each respective CT 32 ensure that the annulus space 44 between the PT 36 and the CT 32 is adequately sized to allow for circulation of gas in the annulus space 44.

[0046] In some embodiments, the bow of a tube can be defined based on a polar coordinate system relative to the center of a straight tube. In some embodiments, the polar coordinates can be defined as particular axial locations of the tube. In some embodiments, the polar coordinates of the bowing can be defined at the axial center of the tube. In some embodiments, the bowing of the tube can be defined at an axial location which corresponds to the location of a spacer, spring or other structural or other component of the channel. In some embodiments, the bowing of the tube is defined at 37.5" + / - 1" at either side of the axial center of the tube.

[0047] In some embodiments, the bowing of the tube is defined at an axial location and a vector between the center of the cross-section of a straight tube and the center of the actual tube.

[0048] In order to determine an operational position (e.g. where the recovered bow of the tube is upward), both an unrestrained bow and a restrained bow are obtained for each of the CTs 32.

[0049] In some embodiments, restrained bow can be measured with one of the fixtures illustrated in FIG. 13. The two expanded ends portions of the tube are clamped in two identical concentric fixtures. In one approach, these two fixtures (and chuck system) are installed on roller bearings and are free to rotate. A dial indicator gauge that is installed in horizontal location is used to capture the maximum TIR (total indicated run-out). The effect of the tube weight on the reading of a dial indicator may be negligible since the indicator arm is moving in horizontal direction.

[0050] In another approach, instead of turning the tube relative to a stationary dial indicator gauge, the tube is fixed on two stationary fixtures and the gauge is turned around the tube on a base ring. The concept of this measurement is to find the geometric centre of the cross section under review relative to the centre of the two fixtures.

[0051] As illustrated in FIG. 14, in some embodiments, he two fixtures include a two piece metal frame and two halves removable nylon sleeves. Nylon inserts of different sizes can be used to accommodate different expanded end portion diameters. To avoid the tube ends from deforming by the fixture and to guarantee that the fixtures are rigid enough to straighten and align the expanded ends relative to each other, an adjustable ID plug can be used to support the ends from inside.

[0052] In some embodiments, the bow of the CTs 32 or the bow of the PTs 36 may be measured by the manufacturer at the point of manufacture. In other embodiments, the bow of the CTs 32 or the PTs 36 may be measured on-site (e.g. at the point of installation or at a nearby staging location) to account for any changes in the bow of the CTs 32 or the PTs 36 that occurred during transportation. In some embodiments, the bow of the CTs 32 or the bow of the PTs 36 may be measured using a laser.

[0053] In one approach, after the unrestrained bow and the restrained bow of the CT 32 are measured, a vector sum of the unrestrained bow and the restrained bow of the CT 32 is calculated. The vector sum may be calculated manually or by a computing device. The vector sum is used to orient the CT 32 so that both the unrestrained bow and the restrained bow face upward (e.g. the position of maximum bow is downward with respect to the ends of the CT 32 or the PT 36) when the CT 32 is in an operational position (FIG. 3). In some embodiments, orienting the CT 32 so that the vector sum of the restrained bow and the unrestrained bow faces upward when in the operational position may improve the CT 32 orientation (i.e., so that the CT 32 is straighter or less bowed) with respect to a predetermined point on the PT 36 by 1 to 2 micro radians. In some embodiments, the vector sum provides the rotational orientation and the axial location of the bow for a specified portion of the CT 32 to be aligned with a reference point, such as, for example, a specific tubesheet 18 bore. In some embodiments, a global coordinate system ("GCS") can be set up in the vault. The GCS allows accurate and repeatable measurements to be made throughout the reactor building. The GCS is a virtual coordinate system, where the origin is positioned as close to the center of the calandria vessel 10 as possible. In such embodiments, the vector sum of restrained bow and the unrestrained bow of the CT 32 may be used to orient the CT 32 with respect to the GCS.

[0054] In some embodiments, orienting the direct CT 32 so that the vector sum of the restrained bow and the unrestrained bow faces upward may guarantee or may increase the likelihood that the recovered bow is upward.

[0055] In another approach, it may be assumed that in at least some instance, the induced bow as the result of the rolled joint would be in the same direction of the theoretical / measured induced bow vector of the restrained bow direction but with a net value that is equal or less than the measured induced bow.

[0056] Accordingly, with reference to FIG. 15, if the calandria tube is installed in a direction such that the orientation of Free Bow <semantics>θFB<annotation encoding="application / x-tex">\theta_{FB}< / annotation>< / semantics> and Restrained Bow <semantics>θRB<annotation encoding="application / x-tex">\theta_{RB}< / annotation>< / semantics> are positioned equally on each side of the 12 o'clock position, that the resultant bow of the CT after making rolled joint will be or will likely be in the upward direction. FIG. 15 shows an extreme case example where the induced bow (IB) and free bow (FB) are in opposite directions with a strong contribution of the induced in the inspection fixture. FIG. 15 also shows why in case the induced bow in the reactor face is only 40% of what was observed during the manufacturing inspection, when this guideline for orientation is used, the resultant reactor restrained bow would still remain in the upward direction.

[0057] In some embodiments, this approach for orienting the CT can be based on the following formulas: [Image disponible dans le document PDF, Image available in the PDF document]

[0058] Theoretical restrained bow profiles of example tubes were plotted in FIG. 16. For the ease of generating input points representing CT profiles, the sinusoidal function was used to generate simulated profiles. As it can be seen in FIG. 16, for most of the cases, the sinusoidal plots can well represent the actual curves.

[0059] FIGS. 3 and 4 illustrate the orientation of a PT 36 with respect to a bore 74 of the end fitting 50' closest to the reactor face. The PT 36 is precisely aligned with the bore 74 of the end fitting 50' closest to the reactor face to verify that an orientation in the downward direction of the PT 36 relative to the end fitting 50 does not exceed a predetermined angle 76. In some embodiments, the predetermined angle 76 is approximately 2 microradians. Precise positioning of the CTs 32 simplifies installation process for PTs 36 and may enable alignment verification steps to be skipped, reducing the amount of time required for the retooling process. In the embodiment illustrated in FIG. 3, the CTs 32 should be oriented so that a centerline of a cross- section of the CT 32 proximate the third garter spring 48" is aligned with a centerline of the tube sheet 18 bore closest to the reactor or is slightly above the tube sheet 18 bore closest to the reactor. In such an orientation, the weight of the PT 36 is supported on the third garter spring 48". Accordingly, orienting the CT 32 so that the centerline of the cross-section of the CT 32 is aligned with the centerline of the bore of the tube sheet 18 closest to the reactor face, the PT 36 may be inserted into the CT 32 and guided into precise alignment with the end fitting bore 50 closest to the reactor face without further measurement or verification of positioning. The position of the bow may be different in other embodiments or in embodiments using more or fewer garter springs 48.

[0060] FIG. 5 illustrates an embodiment of an alignment tool 78 for measuring an orientation of the PTs 26 relative to the end fitting 50. The alignment tool 78 includes a shaft 82, a pair of bearings 86, shielding members 90, a first probe 94, and a second probe 98. The bearings 86 are positioned at the ends of the 82. The shielding members 90 are positioned along the shaft 82 and spaced proximate an end of the shaft 82 that is closest to the reactor face when the alignment tool 78 is positioned within the bore 74 of the end fitting 50. The first probe 94 and the second probe 98 are positioned proximate a second end of the shaft 82. When the alignment tool 78 is positioned within the bore 74 of the end fitting 50, the first probe 94 and the second probe 98 are oriented to engage an end of the PT 36. The first probe 94 and the second probe 98 are positioned to sense a height of the PT 36 relative to a central axis of the bore 74 at different axial positions along the PT 36. An angle between the PT 36 and an axis of the end fitting 50 may be calculated based on the heights sensed by the first probe 94 and the second probe 98.

[0061] As the reactor 6 ages, it may be necessary to remove the CTs 32 and the PTs 36 and replace the CTs 32 and PTs 36 with new CTs 32 and PTs 36 in a process known as "retubing". FIG. 6 is a flow chart illustrating an installation process for the CT 32 of the reactor 6 according to an embodiment of the disclosure. The restrained bow and the unrestrained bow of the CT 32 is measured (block 102). The vector sum of the restrained bow and the unrestrained bow of the CT 32 is calculated (block 106). The steps shown in block 102 and block 106 may be done at the CT 32 manufacturing site, a staging area near the reactor 6, or a re-tubing worksite. The rotational orientation and the axial location of the bow of the CT 32 in the operational position is determined with respect to the tube sheet 18 bores or the GCS so that the vector sum of the restrained bow and the unrestrained bow faces upward in the operational position (block 110). The CT 32 is then rotated into the rotational orientation calculated in block 110 (block 122). In some embodiments, an orientation of the CT 32 is measured after the CT 32 has been rotated into the rotational orientation. After the CT 32 has been positioned in the rotational orientation, the CT 32 is translated axially to position the CT 32 in the axial location of operational position (block 126). In some embodiments, the rotational orientation and / or the axial location of the CT 32 is measured after the CT 32 has been translated axially. The CT 32 is then secured in the operational position using the CT rolled joint inserts 34 (block 130). After the CTs 32 of the calandria vessel 10 have been replaced, the calandria vessel 10 is filled with the heavy water moderator (block 134). Filling the calandria vessel 10 with the heavy water moderator applies a generally upward force 136 (FIG. 7) on the CTs 32, which reduces the gravity-induced sag on the CTs 32, which further reduces misalignment of the CTs 32. The PTs 36 may then be installed into the CTs 32 (block 138).

[0062] Fig. 7 is a schematic representation of a calandria vessel 10 that has been filled with heavy water moderator and that includes a CT that has been positioned in the operational position as described in the method of FIG. 6. As shown in FIG. 7, the CT 32 and the PT 36 are largely unsupported along their longitudinal extents when the CT 32 and the PT 36 are installed in the reactor 6. The upward force 118 is applied proximate the end fitting. In the illustrated embodiment, the force 118 may help improve the alignment between the end fitting 50 closest to the reactor and the PT 36 by approximately 0.44 to 2.15 microradians. The heavy water moderator exerts an upward bouyant force 136 along a longitudinal extent of the CT 32. In some embodiments, the upward force 136 exerted by the heavy water moderator may support the weight of the PTs 36, reducing or eliminating the gravity-induced sag of the PTs.In the illustrated construction, the heavy water moderator may improve an alignment of the CT 32 by approximately <semantics>1−1.8<annotation encoding="application / x-tex">1 - 1.8< / annotation>< / semantics> microradians. In the operational position, the CT 32 and the PT 36 are generally positioned so that the bows face upward. In embodiment of FIG. 7, the position of the bow of the CT 32 is generally proximate a third garter spring 48".

[0063] In some embodiments, it may be necessary to consider the alignment of the lattice tube 65 relative to an absolute horizontal plane. Considering the alignment of the lattice tube 65 relative to the absolute horizontal plane may reduce bow by approximately + / - 51 microradians. In some embodiments, the absolute horizontal plane may be established relative to an X-axis, a Y-axis, or a Z-axis of the GSC. FIG. 8 is a flow chart illustrating an installation process for the CT 32 for such an embodiment. The installation process of FIG. 8 includes steps similar to the steps shown in blocks <semantics>78−134<annotation encoding="application / x-tex">78-134< / annotation>< / semantics> of the embodiment of FIG. 6. For the sake of brevity, these steps will not be described in detail herein.

[0064] Turning now to block 138, an end of the PT 36 is engaged with the end fitting 50" in a predetermined orientation. The end of the PT 36 is then secured to the end fitting 50" using a rolled joint to form a subassembly 38 (block 142). In some embodiments, the PT 36 is positioned in a predetermined or optimized orientation with respect to the PT 36. In some embodiments, the PT 36 is engaged with the end fitting 50" off-site, for example in a clean room. In other embodiments, the PT 36 is engaged with the end fitting 50" at the worksite. The end fitting 50' is engaged with the tube sheet 18 proximate the reactor face (block 146). In some embodiments, block 142 may occur before block 146, block 142 may occur after block 146, or block 142 may occur at the same time as block 146. The PT 36 of the subassembly 38 is then translated axially to insert the PT 36 into the CT 32 and a bore of the tube sheet 18 until a free end (e.g. the end that isn't engaged with the end fitting 50") is near the end fitting 50' (block 148). The end fitting 50" closest to sub-assembly side (e.g. the end fitting 50" farthest from the reactor face) is pushed downward (block 152) by exerting a downward force 146 on the end fitting 50" closest to the sub-assembly side. In some embodiments, the end fitting 50" is pushed downward by a strap engaged with an outer end 150 of the end fitting 50" adapted to urge the outer end 150 into engagement with the upward (e.g. "12 o'clock position") of the bore of the tube sheet 18. The end fitting 50 closest to the reactor face is then lifted (block 156) by exerting an upward force 118 (FIG. 9) on the end fitting 50 closest to the reactor face. In some embodiments, the end fitting 50' closest to the reactor face is lifted to a maximum angle allowed by the bearing clearances (e.g. by lifting the end fitting as high as possible while the PT 36 is positioned within the bore 74 of the end fitting 50'). In some constructions, the end fitting 50' closest to the reactor face is actuated using a jack.

[0065] Fig. 9 is a schematic representation of a calandria vessel 10 that has been filled with heavy water moderator and that includes a CT that has been positioned in the operational position as described in the method of FIG. 8. As shown in FIG. 0, the CT 32 and the PT 36 are largely unsupported along their longitudinal extents when the CT 32 and the PT 36 are installed in the reactor 6. The upward force 118 applied by the jack is applied proximate the end fitting. In the illustrated embodiment, the force 118 may help improve the alignment between the end fitting 50 closest to the reactor and the PT 36 by approximately 0.44 to 2.15 microradians. The downward force 136 applied by the strap is positioned proximate the outward end of the end fitting 50 closest to the subassembly side of the reactor 6. In some constructions, the downward force 136 may reduce the bow of the CT 32 by approximately <semantics>0.2−0.4<annotation encoding="application / x-tex">0.2 - 0.4< / annotation>< / semantics> microradians. The heavy water moderator exerts an upward force 136 along a longitudinal extent of the CT 32. In the illustrated construction, the heavy water moderator may improve an alignment of the CT 32 by approximately <semantics>1−1.8<annotation encoding="application / x-tex">1 - 1.8< / annotation>< / semantics> microradians. In the operational position, the CT 32 and the PT 36 are generally positioned so that the bows face upward. In embodiment of FIG. 7, the position of the bow of the CT 32 is generally proximate a third garter spring 48".

[0066] In some embodiments of the methods shown in FIG. 6 and FIG. 8, the PT 36 may be inserted into the CT 32 in an insertion position in which the bow of the PT 36 faces generally upward. In other embodiments of the methods shown in FIG. 6 and FIG. 8, the PT 36 may be rotated relative to the CT 32 described in block 82 orients the bow of the PT 36 away from the bow of the CT 32 to reduce the effect of gravity-induced misalignment of the bow of the PT 36 and the bow of the CT 32, which helps maintain the annulus spacers 48 captive and reduces the overall bow in the CT / PT combination as the PT 36 is slid axially with respect to the CT 32.

[0067] In some embodiments, a retube tooling platform ("RTP"), and other tool and equipment supports may be installed proximate the reactor 6 during retooling operations. The RTP is an adjustable platform upon which much of the fuel channel component removal and installation operations are performed. In some embodiments, the RTP is a stand-alone machine that does not rely on existing plant structures for positioning or movement. The RTP can be precision-located within the vault, relative to the center point of the calandria vessel 10, using laser tracker technology. By positioning the columns in this way, the RTP is positioned to the as-built location of the calandria vessel 10 (including pitch and yaw), which provides a precision tooling base that permits the use of high accuracy indexing to each lattice site. Installed and mounted on the RTP, and serving as the basis for tool delivery during the removal phase, are one or more installation work tables ("IWTSs"). The IWTs provide a platform that supports retubing equipment. In some embodiments, the jacks and / or the straps may be engaged with the ITWs. In such embodiments, the jacks and / or the straps may be positioned relative to the CTs 32 with a high degree of precision using the GCS. The jacks and / or the straps may be actuated relative to the ITWs or the CTs 32 with a high degree of precision using the GCS.

[0068] In some embodiments, the rotational device may include a grasping member, a rotational actuator, and a position sensor. The grasping member may be adapted to grasp at least an inner wall or an outer wall of the CT 32. In some embodiments, the grasping member may include clamp arms actuable to grasp the CT 32. In other embodiments, the grasping member may include an adjustable collar for engaging the CT 32 to evenly distribute a grasping force about the circumference of the CT 32, reducing the potential for deformation of the CT 32 by the grasping member. In embodiments in which the adjustable collar is adapted to engage the outer wall of the PT 36, the adjustable collar may be tightenable around the CT 32. In embodiments in which the adjustable collar is adapted to engage the inner wall of the CT 32, the adjustable collar may be expandable to grasp the inner wall of the CT 32 after the adjustable collar has been positioned within the CT 32. In some embodiments, the grasping mechanism may include a first adjustable collar to grasp the outer wall of the CT 32 and a second adjustable collar to grasp the inner wall of the CT 32. In a preferred embodiment, the grasping member may grasp both the inner wall and the outer wall of the CT 32 to prevent deformation of the CT 32.

[0069] In some embodiments, the rotational actuator may be a motor adapted to rotate an output shaft engaged with at least a portion of the grasping member. The motor may be controlled to a high degree of precision and be actuable to rotate the grasping member to a high degree of precision. In some embodiments, the position sensor may be a rotary encoder engaged with an output shaft of the motor to sense an angle rotation of the output shaft. In other constructions, the position sensor may be mounted proximate the CT 32 to sense an angle of rotation of the CT 32. Exemplary position sensors include laser, optical, or magnetic rotary encoders.

[0070] In some embodiments, the ram may include a grasping member, a translational actuator, and a position sensor. The grasping member may be adapted to grasp at least an inner wall or an outer wall of the CT 32. The grasping member may be substantially similar to the grasping member described above with respect to the rotational member. The translational actuator is adapted to actuate the grasping member in a linear direction that is generally parallel to a longitudinal axis of the PT 36 or the CT 32. Exemplary translational actuators may include servo motors, pneumatic actuators, or hydraulic cylinders. In some embodiments, the position sensor may be engaged with an output shaft of the motor to sense translation of the output shaft. In other embodiments, the position sensor may be mounted proximate the CT 32 to sense translation of the CT 32. In some embodiments, the position sensor may include laser, optical, or magnetic proximity sensors. In other embodiments, the position sensor may include a proximity sensor, such as a laser proximity sensor, adapted to sense a distance to a marked portion of the output of the translational actuator or a marked portion of the CT 32.

[0071] In some embodiments, the rotational device and the ram may be separate tools. In other embodiments, the rotational device and the ram may be included in the same tool.

[0072] In embodiments that include the RTP and the IWTs, tools used to install the CT 32 may be positioned on the RTP or the IWTs. Tools installed on the RTP or the ITWs may be positioned and actuated with high precision with respect to the CTs 32 using the GCS. For example, the rotational device may be positioned with respect to the CT 32 using the GCS. The grasping means of the rotational device and / or the translational actuator of the rotational device may be controlled (e.g. rotated or repositioned) using coordinates of the GCS. In another example, the ram may be positioned with respect to the CT 32 using the GCS. The grasping means of the ram and / or the translational actuator of the ram may be controlled (e.g. rotated or repositioned) using coordinates of the GCS.

[0073] In some embodiments, the CT 32 may be manually oriented with respect the bore of the tube sheet 18.

[0074] In some embodiments, positioning of the pressure tube can be based on the skew angle and / or eccentricity of the ends of the pressure tube. After trimming the pressure tube to its final length and prior to fabrication of the sub-assembly, the alignment of the pressure tube reactor side (sometimes referred to as LCRJ - low clearance roll joint) or first end can be measured relative to the sub-assembly (sometimes referred to as ZCRJ - zero clearance roll joint ) or second end. This alignment in every plane passing through the second end reference axis is comprised of two components as follow: 1. First end skew angle(<semantics>α<annotation encoding="application / x-tex">\alpha< / annotation>< / semantics>) 2. Eccentricity of the LCRJ End relative to the second end axis <semantics>(λ)<annotation encoding="application / x-tex">(\lambda)< / annotation>< / semantics>

[0075] This misalignment can be measured when both ends are in free-state or when the second end is clamped at the last 3 to 5 inches shown as dimension LCL in Figure 17. Effect of the weight may be isolated during this measurement and may not influence the results.

[0076] Misalignment of the fend relative to the ZCRJ end in any plane that passes through the axis of the ZCRJ end is as follow: [Image disponible dans le document PDF, Image available in the PDF document]

[0077] Where LCRCJ end skew angle (<semantics>α<annotation encoding="application / x-tex">\alpha< / annotation>< / semantics>) is the angle of the axis of the last 2 to 3 inches of the tube end and is established as the angle between the shadow projection of the LCRJ end axis onto the plane of study. Angle <semantics>α<annotation encoding="application / x-tex">\alpha< / annotation>< / semantics> is positive when looking through the LCRJ end toward the ZCRJ end, the LCRJ end axis is in upward direction as shown in Figure 17.

[0078] Eccentricity (<semantics>λ<annotation encoding="application / x-tex">\lambda< / annotation>< / semantics>) of the LCRJ end is the distance of the centre of any cross section of the tube located within the last ½ inch of the tube end relative to the axis of the ZCRJ end. Eccentricity is positive when it is upward of the ZCRJ axis in the plane of study as shown in Figure 17.

[0079] The plane that passes the axis of the ZCRJ end of the tube and in which the misalignment M is maximized with a positive number is to be identified. The angle of this plane relative to the pop mark (e.g. a reference mark on the tube) can be either marked permanently with a double pop mark, or temporarily with a removable marking or nor marked at all but tracked on a record sheet. The rotary position of the pressure tube relative to the feeder side port can be established such that the maximum misalignment of the pressure tube LCRJ end at the reactor west face relative to the sub-assembly ZCRJ end is in the upward direction; i.e. 12 o'clock.

[0080] Misalignment of one end of a beam relative to the other end is defined with two components of 1) LCRJ End skew angle (<semantics>α<annotation encoding="application / x-tex">\alpha< / annotation>< / semantics>) 2) Eccentricity of the LCRJ End relative to the ZCRJ axis <semantics>(λ)<annotation encoding="application / x-tex">(\lambda)< / annotation>< / semantics>

[0081] The goal of this work is to identify the net effect of the misalignment of the pressure tube LCRJ end, relative to the ZCRJ end, when the sub-assembly is formed and inserted through the reactor east face.

[0082] The ZCR end after being rolled to the end-fitting and confined by the bearings at east side represents a cantilever beam. Beam deflection equations for cantilever support are provided in the table in FIG. 18 for reference.

[0083] FIG. 19 shows 4 different scenarios for the tube body profile. The angle (<semantics>α<annotation encoding="application / x-tex">\alpha< / annotation>< / semantics>) of the end at right side of the sketch representing the LCRJ end of a pressure tube relative to the other side and, as it can be seen it is the same for all four profiles. What is different in all four profiles is the eccentricity (<semantics>λ<annotation encoding="application / x-tex">\lambda< / annotation>< / semantics>) for these profiles.

[0084] Assuming the second end fitting on the LCRJ end is in line with the subassembly end fitting when both are confined within the similar bearing system. (This assumption is valid as all the other bearing arrangements are modeled separately and the effect of end-fitting alternative locations are superimposed on the shape of the fuel channel in nominal arrangement.)

[0085] In order for the free end travel vertically to become in line with the ZCRJ end (fixed end), the free end will be sloped to angle <semantics>β<annotation encoding="application / x-tex">\beta< / annotation>< / semantics> found in the FIG. 18 beam deflection table above:

[0086] <semantics>β=PL22EI<annotation encoding="application / x-tex">\beta = \frac{PL^2}{2EI}< / annotation>< / semantics> (note that <semantics>β<annotation encoding="application / x-tex">\beta< / annotation>< / semantics> is shown as <semantics>θ<annotation encoding="application / x-tex">\theta< / annotation>< / semantics> in the FIG. 18 table)

[0087] [Image disponible dans le document PDF, Image available in the PDF document]

[0088] Therefore angle <semantics>β<annotation encoding="application / x-tex">\beta< / annotation>< / semantics> is:

[0089] [Image disponible dans le document PDF, Image available in the PDF document]

[0090] Therefore, the overall angle of the PT LCRJ end after it is aligned with the ZCRJ end- fitting is:

[0091] Misalignment = <semantics>M=α+β=α+2λ3(LPT−LCL)<annotation encoding="application / x-tex">M = \alpha + \beta = \alpha + \frac{2\lambda}{3(L_{PT} - L_{CL})}< / annotation>< / semantics>

[0092] The method of measurement proposed by the tooling group is to clamp the ZCRJ end of the pressure tube and measure total indicator runout (TIR) of two points at the free end (LCRJ end) of the tube. These two example target points are 2.5 inch apart and the first one is within the first 3 / 8 inch from the tube end (see FIG. 20). 1) PT ZCRJ are clamped first with the pop mark at 12 o'clock (see FIG. 21). 2) Both micrometers (tool that measures topography of surface usually inmicrons) starts from zero relative to a reference cylinder that is perfectly aligned to the clamp end of the ZCRJ end. 3) Then the micrometer housing moves to the LCRJ end at the set axial location to scan the surface of the LCRJ end. 4) From the TIR reading of the micrometer, the location of the centre of the PT cross section at points P1 and P2 are to be located. 5) The centre point <semantics>P1<annotation encoding="application / x-tex">P_1< / annotation>< / semantics> and <semantics>P2<annotation encoding="application / x-tex">P_2< / annotation>< / semantics> in the horizontal direction is basically <semantics>x1<annotation encoding="application / x-tex">x_1< / annotation>< / semantics> and <semantics>x2<annotation encoding="application / x-tex">x_2< / annotation>< / semantics> component of the points <semantics>P1<annotation encoding="application / x-tex">P_1< / annotation>< / semantics> and <semantics>P2<annotation encoding="application / x-tex">P_2< / annotation>< / semantics>. 6) The tube is then to be rotated 90° and clamped again as per FIG. 22. 7) TIR displacement of the micrometer from for cross section 1 and 2 provided Y component of the points, <semantics>y1<annotation encoding="application / x-tex">y_1< / annotation>< / semantics> and <semantics>y2<annotation encoding="application / x-tex">y_2< / annotation>< / semantics>. 8) After finding X and Y components of Points P1 and P2 from the LCRJ end, for every degree of angle θ, ranging from 0 to 359 degrees, components X and Y of points P1 and P2 can be translated to new coordinated system X' and Y' after an angular rotation. 9) Angular rotation for transfer from X and Y coordinate system to X' and Y' with angle <semantics>θ<annotation encoding="application / x-tex">\theta< / annotation>< / semantics> from the original system is as follows: [Image disponible dans le document PDF, Image available in the PDF document] 10) After conversion of X and Y to new coordinate system to X' and Y' for full rotation of 0 to 359°, the angle α formed by points P1 and P2 onto the plane ZY' can be calculated as follows: [Image disponible dans le document PDF, Image available in the PDF document] Where: [Image disponible dans le document PDF, Image available in the PDF document] [Image disponible dans le document PDF, Image available in the PDF document] <semantics>LPT<annotation encoding="application / x-tex">L_{PT}< / annotation>< / semantics> = Pressure tube cut length LCL= Length Clamp engagement at the Pressure tube ZCRJ end. (See FIG. 23) 11) Misalignment in plane Y'Z which is at rotary angle of <semantics>θ<annotation encoding="application / x-tex">\theta< / annotation>< / semantics> from the original pop mark is found as follows: Misalignment in Plane Y [Image disponible dans le document PDF, Image available in the PDF document] 12) After repeating above calculations for every 1° of angle <semantics>θ<annotation encoding="application / x-tex">\theta< / annotation>< / semantics> from 0 to 359°, the angle in which misalignment <semantics>Mθ<annotation encoding="application / x-tex">M_{\theta}< / annotation>< / semantics> is maximum, can be identified and marked for installation. This rotary point that has an angle <semantics>θ<annotation encoding="application / x-tex">\theta< / annotation>< / semantics> from the pop mark can be aligned at the top 12 o'clock orientation at reactor face.

[0093] In some instances, by rotating the pressure tube, the X and Y values can be measured without needing to necessarily compensate for the effect of weight of the tube.

[0094] It should also be noted that the embodiments described above and illustrated in the accompanying figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present disclosure. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present disclosure as set forth in the appended claims.

Claims

<pat:ClaimStatement>CLAIMS What is claimed is.< / pat:ClaimStatement> <pat:Claims com:id="claims"> <pat:Claim com:id="CLM-00001"> <pat:ClaimNumber>1< / pat:ClaimNumber> <pat:ClaimText>1. A method for positioning a calandria tube within a calandria vessel of a nuclear reactor, the method comprising: determining a restrained bow of the calandria tube; determining an unrestrained bow of the calandria tube; calculating an alignment angle between a vector angle of the restrained bow of the calandria tube and a vector angle of the unrestrained bow of the calandria tube at an axial location; and positioning the calandria tube with respect to the nuclear reactor to orient the alignment angle in an operational position. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00002"> <pat:ClaimNumber>2< / pat:ClaimNumber> <pat:ClaimText>2. The method of claim 1, wherein the alignment angle faces upward upon installation of the calandria tube. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00003"> <pat:ClaimNumber>3< / pat:ClaimNumber> <pat:ClaimText>3. The method of claim 1, wherein the alignment angle is the angle of a vector sum of the restrained bow of the calandria tube and the unrestrained bow of the calandria tube. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00004"> <pat:ClaimNumber>4< / pat:ClaimNumber> <pat:ClaimText>4. The method of claim l, wherein the alignment angle is an average of the vector angle of the restrained bow and the vector angle of the unrestrained bow. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00005"> <pat:ClaimNumber>5< / pat:ClaimNumber> <pat:ClaimText>5. The method of claim l, wherein the alignment angle is an angle of the restrained bow. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00006"> <pat:ClaimNumber>6< / pat:ClaimNumber> <pat:ClaimText>6. The method of claim l, wherein positioning the calandria tube comprises rotating the calandria tube based on a relative angle between the alignment angle and a reference angle associated with the calandria tube to orient the alignment angle in the operational position. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00007"> <pat:ClaimNumber>7< / pat:ClaimNumber> <pat:ClaimText>7. The method of claim 1, further comprising the steps of aligning an end of a pressure tube with a bore of a first end fitting and forming a subassembly by securing the end of the pressure tube to the end fitting. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00008"> <pat:ClaimNumber>8< / pat:ClaimNumber> <pat:ClaimText>8. The method of claim 7, further comprising the step of inserting the subassembly into the calandria tube until a free end of the pressure tube aligned with a bore of a second end fitting positioned in a bore of a tube sheet positioned at a side of a nuclear reactor core. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00009"> <pat:ClaimNumber>9< / pat:ClaimNumber> <pat:ClaimText>9. The method of claim 8, further comprising the step of lifting the second end fitting to a maximum angle within bearing clearances. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00010"> <pat:ClaimNumber>10< / pat:ClaimNumber> <pat:ClaimText>10. The method of claim 7, further comprising the step of exerting a downward force on the first end fitting. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00011"> <pat:ClaimNumber>11< / pat:ClaimNumber> <pat:ClaimText>11. The method of claim 1, further comprising the step of securing the calandria tube in the operational position. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00012"> <pat:ClaimNumber>12< / pat:ClaimNumber> <pat:ClaimText>12. The method of claim 7, further comprising the step of positioning a pressure tube within the calandria tube. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00013"> <pat:ClaimNumber>13< / pat:ClaimNumber> <pat:ClaimText>13. The method of claim 12, further comprising the step of filling the calandria vessel with moderator before positioning the pressure tube within the calandria tube. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00014"> <pat:ClaimNumber>14< / pat:ClaimNumber> <pat:ClaimText>14. The method of claim l, wherein a midline of the calandria tube is oriented with respect to a midline of a bore of a tube sheet positioned within the calandria vessel. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00015"> <pat:ClaimNumber>15< / pat:ClaimNumber> <pat:ClaimText>15. The method of claim l, wherein the calandria tube is oriented with respect to a global coordinate system comprising a virtual coordinate system defined by an origin positioned at or near a center of the calandria vessel. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00016"> <pat:ClaimNumber>16< / pat:ClaimNumber> <pat:ClaimText>16. A method for positioning a calandria tube within a calandria vessel of a nuclear reactor, the method comprising: determining a bow of the of the calandria tube; orienting the calandria tube so a restrained bow faces upward upon installation of the calandria tube; orienting a subassembly including a pressure tube and a first end fitting, the first end fitting engaged with a first bore of a first tube sheet and the pressure tube positioned within the calandria tube, with respect to a second end fitting positioned within a bore of a tube sheet positioned at a reactor face; exerting a downward force on the first end fitting; and securing the calandria tube in an operational position. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00017"> <pat:ClaimNumber>17< / pat:ClaimNumber> <pat:ClaimText>17. The method of claim 16, wherein the first end fitting is spaced from a reactor face of the nuclear reactor. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00018"> <pat:ClaimNumber>18< / pat:ClaimNumber> <pat:ClaimText>18. The method of claim 16, wherein a step of determining a bow of the calandria tube includes: determining the restrained bow of the calandria tube; and determining an unrestrained bow of the calandria tube. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00019"> <pat:ClaimNumber>19< / pat:ClaimNumber> <pat:ClaimText>19. The method of claim 16, further comprising the steps of: calculating a vector sum of the restrained bow of the calandria tube and the restrained bow of the calandria tube; and positioning the calandria tube with respect to the nuclear reactor to orient the vector sum in the operational position. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00020"> <pat:ClaimNumber>20< / pat:ClaimNumber> <pat:ClaimText>20. The method of claim 16, further comprising the step of positioning the pressure tube within the calandria tube. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00021"> <pat:ClaimNumber>21< / pat:ClaimNumber> <pat:ClaimText>21. The method of claim 20, further comprising the step of filling the calandria vessel with moderator before positioning the pressure tube within the calandria tube. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00022"> <pat:ClaimNumber>22< / pat:ClaimNumber> <pat:ClaimText>22. The method of claim 16, wherein a midline of the calandria tube is oriented with respect to a midline of a bore of a tube sheet positioned within the calandria vessel. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00023"> <pat:ClaimNumber>23< / pat:ClaimNumber> <pat:ClaimText>23. The method of claim 16, wherein the calandria tube is oriented with respect to a global coordinate system comprising a virtual coordinate system defined by an origin positioned at or near a center of the calandria vessel. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00024"> <pat:ClaimNumber>24< / pat:ClaimNumber> <pat:ClaimText>24. The method of any one of claims 1-15, wherein the operational position comprises a rotational orientation and an axial location within the calandria vessel during operation of the nuclear reactor, and wherein the operational position is selected to align the alignment angle with a reference point. < / pat:ClaimText> < / pat:Claim> <pat:Claim com:id="CLM-00025"> <pat:ClaimNumber>25< / pat:ClaimNumber> <pat:ClaimText>25. The method of claim 16, wherein the operational position comprises a rotational orientation and an axial location within the calandria vessel during operation of the nuclear reactor, and wherein the operational position is selected to align an alignment angle with a reference point, the alignment angle being calculated between a vector angle of the restrained bow of the calandria tube and a vector angle of an unrestrained bow of the calandria tube at the axial location. < / pat:ClaimText> < / pat:Claim> < / pat:Claims>