Advanced manufacturing of printed wick integrated heat pipe segments

Abstract

A transition piece for joining heat pipe segments in a joining process is provided. The transition piece includes a head section, a body section, a tail section, and a plurality of alignment tabs configured to facilitate rotational alignment of an end of the body section with an end of a heat pipe segment during the joining process. The body section includes a wick and an outer wall. Each of the plurality of alignment tabs includes an end portion extending axially from the body section. The body section and the plurality of alignment tabs are configured as a unitary structure. Methods for manufacturing a heat pipe transition piece and methods for joining heat pipe segments are also provided.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of and priority under 35 U.S.C. § 120 of U.S. patent application Ser. No. 18 / 164,911, filed February 6, 2023, entitled "ADVANCED MANUFACTURING HEAT PIPE SEGMENT WITH INTEGRAL PRINTED WICK," the contents of which are incorporated herein by reference in their entirety. [Background technology]

[0002] Heat pipes are sealed, passive devices that rely on the phase change of a working fluid to transfer thermal energy. Typically, the working fluid circulates between a hot primary section and a cold secondary section through a wick section spanning the length of the heat pipe, which contains relatively small and / or high-surface-area flow passages. Current nuclear reactor designs require heat pipes to span several meters in length. Conventional methods for manufacturing long heat pipes for nuclear reactors involve several steps and / or techniques that are prone to small defects or imperfections along the length of the heat pipe. Heat pipe sections containing defects are discarded to avoid failure during use, despite the presence of defect-free partial-length sections. Therefore, there is a need to develop alternative heat pipe components and associated manufacturing methods to optimize the cost and throughput of heat pipe manufacturing without compromising the reliability and / or efficiency of heat transfer from the nuclear reactor. Summary of the Invention

[0003] The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments disclosed herein and is not intended to be a complete description. A complete understanding of the various embodiments disclosed herein can be obtained by taking the entire specification, claims, and abstract as a whole.

[0004] In various embodiments, a transition piece for joining heat pipe segments in a joining process is disclosed. In some embodiments, the transition piece includes a head section including a first tubular segment, a body section extending from a first end to a second end, a tail section including a second tubular segment, and a plurality of alignment tabs configured to facilitate rotational alignment of the end of the body section with the end of the heat pipe segment during the joining process. In some embodiments, the head section extends axially from the first end of the transition piece to a first axial position, and the first tubular segment is configured to connect with an end portion of the first heat pipe segment. In some embodiments, the body section includes a wick having an outer surface, the wick defining a cavity therein, and an outer wall having an inner surface surrounding the outer surface of the wick. In some embodiments, the first end of the body section is positioned at the first axial position and the second end is positioned at a second axial position, and the inner surface of the outer wall and the outer surface of the wick are positioned to form a gap therebetween. In some embodiments, the tail section extends axially from the second end of the body section to the second end of the transition piece, and the second tubular segment is configured to connect with an end portion of a second heat pipe segment. In some embodiments, each of the plurality of alignment tabs includes an end portion extending axially away from the body section. In some embodiments, the body section and the plurality of alignment tabs are configured as a unitary structure.

[0005] In various embodiments, a method for manufacturing a transition piece for a heat pipe in a nuclear reactor heat transfer system is disclosed. In some embodiments, the method includes manufacturing a first section of the transition piece, forming a body of the transition piece by a molding process, and forming a tail section of the transition piece. In some embodiments, the first section is configured to extend axially from a first end of the transition piece to a first axial location, and an inner portion of the first section is configured to connect with an end portion of a first heat pipe segment. In some embodiments, the body includes a wick surrounded by an outer wall, and an outer surface of the wick and an inner surface of the outer wall are arranged to form a gap therebetween. In some embodiments, the body includes forming a first end of the body at the first axial location and extending the first end of the body to a second axial location. In some embodiments, forming the tail section includes extending the tail section axially from the second axial location to a second end of the transition piece. In some embodiments, the tail section is configured to connect with an end portion of a second heat pipe segment.

[0006] In various embodiments, a method of joining segments of a heat pipe in a nuclear reactor is disclosed. In some embodiments, the method includes joining a first end portion of a transition piece to an end portion of a first heat pipe segment and joining a second end portion of the transition piece to an end portion of a second heat pipe segment to produce the heat pipe. In some embodiments, the transition piece, the first heat pipe segment, and the second heat pipe segment each include an internal wick section. In some embodiments, each of the internal wick sections is joined to form a continuous wick section of the heat pipe.

[0007] These and other objects, features, and characteristics of the present disclosure, as well as the method of operation and function of the associated elements of construction, and combination of parts and economies of manufacture, will become more apparent from a study of the following description and appended claims, taken in conjunction with the accompanying drawings, which are to be read in conjunction with the accompanying drawings, but which are to be expressly understood as being for the purpose of illustration and description only and are not intended as a definition of the limits of the embodiments disclosed herein.

[0008] The various aspects described herein, together with their objects and advantages, may best be understood by referring to the following description taken in conjunction with the accompanying drawings, in which: [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional schematic diagram of a heat pipe according to at least one non-limiting embodiment of the present disclosure. [Figure 2] FIG. 1 is a perspective view of a transition piece according to at least one non-limiting embodiment of the present disclosure. [Figure 3] FIG. 3 is a partial cross-sectional schematic view of the transition piece of FIG. 2 according to at least one non-limiting embodiment of the present disclosure. [Figure 4] FIG. 10 is a cross-sectional view of a body section of a transition piece according to at least one non-limiting embodiment of the present disclosure. [Figure 5] FIG. 1 is a perspective view of a transition piece according to at least one non-limiting embodiment of the present disclosure. [Figure 6] FIG. 6 is a partial cross-sectional schematic view of the transition piece of FIG. 5, according to at least one non-limiting embodiment of the present disclosure. [Figure 7] FIG. 10 is a perspective view of a body section of a transition piece according to at least one non-limiting embodiment of the present disclosure. [Figure 8] FIG. 1 is a perspective view of a transition piece according to at least one non-limiting embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set forth herein are, in one aspect, illustrative of various aspects of the present disclosure, and such exemplifications are not to be construed as limiting the scope of any of the aspects disclosed herein.

[0011] Certain exemplary embodiments of the present disclosure will now be described to provide a general understanding of the principles of composition, function, manufacture, and use of the compositions and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the compositions, articles, and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments, and that the scope of various examples of the present disclosure is defined only by the claims. Features shown or described in connection with one exemplary embodiment may be combined with features of other embodiments. Such modifications and variations are intended to be within the scope of the present disclosure.

[0012] Throughout this specification, references to "various examples," "several examples," "one example," "an example," etc., mean that a particular feature, structure, or characteristic described in connection with an example is included in that example. Thus, the appearance of phrases such as "in various examples," "in several examples," "in one example," "in an example," etc. in various places throughout this specification do not necessarily all refer to the same example. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in an example or examples. Thus, a particular feature, structure, or characteristic illustrated or described in connection with one example may be combined, in whole or in part, with features, structures, or characteristics of another example or other examples, without limitation. Such modifications and variations are intended to be within the scope of the present examples.

[0013] In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings. Also, in the following description, it should be understood that terms such as "front," "rear," "left," "right," "upper," "lower," "up," "down," etc. are terms of convenience and are not to be construed as limiting terms.

[0014] Those skilled in the art will understand that references to the terms "radial" and "concentric" that appear in this specification and claims are not necessarily limited to and / or relate to particular shapes having circular cross sections or arcs, but may be used with any shape or geometric shape that has a center of rotation. For example, a square circumscribing a circle is concentric, and line segments extending from the center of the square toward a side or corner of the square can be described as line segments extending radially outward.

[0015] A heat pipe is a sealed, two-phase heat transfer component used to transfer heat from a primary side (evaporator section) to a secondary side (condenser section). For example, FIG. 1 illustrates a heat pipe 100 comprising a wick 108, an outer wall 112, an evaporator section 102, an adiabatic section 104, and a condenser section 106. The wick 108 defines a cavity 110 therein and includes a porous region 118 comprised of capillaries, grooves, microchannels, and / or other high surface area regions. The cavity 110 functions as a central flow path suitable for vapor flow, while the high surface area of ​​the porous region 118 defines peripheral flow paths suitable for liquid flow driven by capillary action and / or gravity assist. The heat pipe 100 further includes a working fluid, such as water, liquid potassium, sodium, or an alkali metal. During operation, the working fluid is configured to absorb heat in the evaporator section 102 and undergo a phase transition to a saturated vapor. Saturated vapor flows through the adiabatic section 104 via the cavity 110 toward the condensation section 106. As the vapor loses its latent heat of vaporization in the condensation section 106, the resulting condensed phase returns to the evaporation section 102 via peripheral flow through the wick 108 and the peripheral gap between the wick 108 and the outer wall 112. The aforementioned working fluid flow path is indicated by the split arrows in Figure 1. The phase change process and two-phase flow circulation continue as long as the temperature gradient between the evaporation section and the condensation section is maintained. Due to the extremely high heat transfer coefficients for boiling and condensation, heat pipes are very effective heat conductors.

[0016] In nuclear systems, heat pipes are utilized by placing the evaporator section of the heat pipe within the core containing the nuclear fuel and the condenser section near a heat exchanger. The nuclear fuel vaporizes the working fluid, and the heat exchanger absorbs the latent heat in the condenser section. Examples of heat pipes in nuclear applications are described in U.S. Pat. No. 5,684,848, U.S. Pat. No. 6,768,781, and U.S. Patent Application Publication No. 2016 / 0027536, all of which are incorporated by reference in their entireties.

[0017] Another use of heat pipes in nuclear systems is in microreactors. Microreactors are nuclear reactors that generate less than 10 MWe and can be located in remote locations. Such microreactors are housed in relatively small vessels, operate without active human involvement, and operate without refueling / replacement for longer periods than conventional nuclear power plants. One such microreactor is the eVinci microreactor system designed by Westinghouse Electric Company. The eVinci system is a heat-pipe-cooled nuclear reactor power system that utilizes heat pipes as passive heat removal devices to efficiently transfer thermal energy from the reactor core to a heat exchanger.

[0018] Heat pipes used in microreactors experience extreme operating temperatures (over 850°C) and require an internal wick made from a material that can withstand these temperatures and is compatible with the working fluid. Traditional wicks are made from rolled wire mesh that is diffusion bonded into a tubular shape. This wick tube maintains rigidity while allowing the working fluid in the heat pipe to pass radially (i.e., after the latent heat is released and the working fluid is absorbed by the wick) and along its axis or length (where capillary action returns the working fluid toward the evaporation section).

[0019] Manufacturing wicks for insertion into heat pipes requires a highly complex and detailed process. At a very sophisticated level, wicks are currently manufactured by rolling a sheet of woven wick mesh material into the desired shape, compressing a material (such as a tube) onto the wick to force it into the desired shape, diffusion bonding the mesh in a vacuum-level oven while maintaining the wick in compression, and then removing the material used to hold the wick in compression during the diffusion bonding process. An example of such a wick-forming method is described in U.S. Pat. No. 3,964,902, entitled "METHOD OF FORMING A WICK FOR A HEAT PIPE," which is incorporated herein by reference.

[0020] As mentioned above, current methods for forming wicks require the material used to hold the wick in a compressed state to be removed after the diffusion bonding process. For example, U.S. Patent No. 3,964,902 describes a method that uses copper inner and outer mandrels to compress the wick, and then requires chemical removal of the inner and outer mandrels after diffusion bonding using a chemical etching technique. However, subjecting the wick to this chemical etching process can introduce impurities into the wick, preventing it from functioning as intended. Additionally, chemical etching techniques increase the time and cost associated with wick manufacturing.

[0021] For microreactors, heat pipes must be manufactured in lengths exceeding 7 meters. Conventional methods for manufacturing such lengths of tube and wick with suitable materials are costly and leave little room for error. Minor defects within the tube or wick can lead to premature failure of the heat pipe during use, resulting in rejection before further processing because repair or rework is impractical with current methods. Cutting a portion of a partial-length segment of a defect-free heat pipe would otherwise compromise its sealing, rendering the heat pipe segment unusable. Therefore, heat pipe manufacturing can result in high scrap rates. Furthermore, current methods for manufacturing heat pipes involve complex techniques limited to the production of straight sections, which do not allow for flow redirection and / or variability in flow cross-sectional shape. Accordingly, various aspects of the present disclosure provide various apparatus and methods for optimizing the technical and economic aspects of heat pipe manufacturing, including the recovery of heat pipe segments. In some embodiments, optimization can reduce pipe manufacturing costs and / or minimize the amount of waste generated therefrom.

[0022] As described in more detail below, the transition piece generally includes a head section, a body section, and a tail section. The head and tail sections can separately interface with end portions of separate heat pipe segments having similar or different cross-sectional shapes and / or dimensions. The body section includes a wick and an outer wall to maintain continuity of the flow path between the joined heat pipe segments. Furthermore, the transition piece generally is constructed of a single composition, such as, for example, an alloy of iron, chromium, and aluminum (FeCrAl), similar to the existing heat pipe segment, or can be joined thereto with a permanent joining process, such as, for example, welding or brazing.

[0023] 2 provides a perspective view of a transition piece 1000 according to at least one non-limiting embodiment of the present disclosure. The transition piece 1000 includes a head section 1100 extending linearly from a first end 1001 to a first axial location 1002, a body section 1200 extending linearly from the first axial location 1002 to a second axial location 1003, a tail section 1300 extending linearly from the second axial location 1003 to a second end 1004, and a plurality of alignment tabs 1400. As described later in this disclosure, the plurality of alignment tabs 1400 are positioned radially outward relative to the head section 1100 and / or the tail section 1300.

[0024] 3 provides a partial cross-sectional view of the transition piece 1000 of FIG. 2 in accordance with at least one non-limiting embodiment of the present disclosure. In various examples, the head section 1100 includes a first tubular segment 1110 having an inner surface 1112 and an outer surface 1114. In some examples, the head section 1100 may include an outer section 1120 that surrounds the first tubular segment 1110.

[0025] The first tubular segment 1110 is configured to connect with the end portion of the first heat pipe segment. For example, the first tubular segment 1110 can be configured as a cylindrical tube having an axial length corresponding to its insertion depth into the end portion of the first heat pipe segment. In some examples, the first tubular segment 1110 is configured with an axial length of approximately 12.5 millimeters. The outer surface 1114 can have a diameter substantially the same as or slightly smaller than the opening of the first heat pipe segment. Furthermore, the diameter of the inner surface 1112 can be configured to be slightly smaller than the inner diameter of the first heat pipe segment. For example, the inner surface 1112 can have a diameter approximately 4 millimeters smaller, approximately 3 millimeters smaller, or approximately 2 millimeters smaller than the diameter of the outer surface 1114. A first tubular segment 1110 incorporating this configuration can be inserted into and axially aligned with the end portion of the first heat pipe segment without significantly reducing the original cross-sectional area available for central fluid flow within the first heat pipe segment. Thus, the first tubular segment 1110 can be configured to continue the flow path of the heat pipe segment without compromising its central fluid flow characteristics.

[0026] 2-3 , in examples where the head section 1100 includes the outer section 1120, the outer section 1120 can be configured as a removable and / or sacrificial support. For example, the first tubular segment 1110 and the outer section 1120 can be configured as concentric shapes separated by a gap. The outer section 1120 can provide additional support during manufacturing of the transition piece 1000. For example, if the transition piece 1000 is manufactured using an additive manufacturing process, such as powder bed fusion, the outer section 1120 can interface with the first tubular section segment 1110 to provide additional support when the head section 1100 must serve as a base for the remainder of the transition piece 1000. Additionally, the outer section 1120 can include an indexing feature 1122, such as a recess, groove, or perforation, at the first axial location 1002 to indicate the axial transition from the head section 1100 to the body section 1200. An outer section 1120 incorporating this configuration can facilitate its complete removal from the transition piece 1000 without affecting the properties and / or shape of the first tubular segment 1110 and / or body section 1200.

[0027] Referring back to FIG. 2 , the tail section 1300 includes a second tubular segment 1310 having an inner surface 1312 and an outer surface 1314. In various embodiments, the second tubular segment 1310 is configured to connect with an end portion of a second heat pipe assembly. For example, the second tubular segment 1310 can be configured as a cylindrical tube having an axial length corresponding to an insertion depth into the end portion of the second heat pipe segment. In some examples, the second tubular segment 1310 is configured with an axial length of approximately 12.5 millimeters. The outer surface 1314 can have a diameter substantially the same as or slightly smaller than the opening of the second heat pipe segment. Furthermore, the diameter of the inner surface 1312 can be configured to be slightly smaller than the inner diameter of the second heat pipe segment. For example, the inner surface 1312 can have a diameter approximately 4 millimeters smaller, approximately 3 millimeters smaller, or approximately 2 millimeters smaller than the diameter of the outer surface 1314. A second tubular segment 1310 incorporating this configuration can be inserted into axial alignment with an end portion of the second heat pipe segment without significantly reducing the original cross-sectional area available for central fluid flow within the second heat pipe segment. Thus, the second tubular segment 1310 can be configured to continue the flow path of the heat pipe segment without compromising its central fluid flow characteristics.

[0028] In some examples, the second tubular segment 1310 can be configured similarly to the first tubular segment 1110. Accordingly, the transition piece 1000 can be configured to connect the end portions of two similarly sized heat pipe segments. Other configurations of the transition piece 1000 for joining dissimilar heat pipe segments are contemplated by the present disclosure. For example, in some embodiments, the first tubular segment 1110 and the second tubular segment 1310 are configured to have different dimensions and / or cross-sectional shapes.

[0029] 4 is a cross-sectional view of a body section 1200 including a wick 1210 and an outer wall 1220, according to at least one non-limiting embodiment of the present disclosure. The body section 1200 includes a first end 1201 disposed at a first axial location 1002 and a second end 1202 disposed at a second axial location 1003. The wick 1210 includes an inner surface 1214 defining a cavity therein and an outer surface 1216. The outer wall 1220 includes an inner surface 1222 and an outer surface 1224. The inner surface 1222 of the outer wall surrounds the outer surface 1216 of the wick.

[0030] The outer wall 1220 can be configured to mate with an existing heat pipe segment. For example, the outer wall 1220 can be configured to have a cylindrical shape with an outer surface 1224 having a diameter substantially the same as or slightly larger than the outer diameter of the end of the existing heat pipe segment. In certain examples, the end portions of the outer surface 1224 located at the first end 1201 and / or the second end 1202 are configured to have an outer diameter of about 40 millimeters, about 30 millimeters, about 25 millimeters, about 20 millimeters, about 15 millimeters, or about 10 millimeters. In particular examples, the outer wall 1220 can be configured in the shape of a cylinder with an outer diameter of about 21 millimeters or about 17 millimeters. Furthermore, the outer wall 1220 can be configured to have a thickness of about 10 millimeters or less, about 5 millimeters or less, about 3 millimeters or less, or about 2 millimeters. In certain examples, the outer wall 1220 can be configured to have an inner diameter larger than the inner diameter of the outer wall of the existing heat pipe segment to be joined to the transition piece 1000. An outer wall 1220 incorporating this configuration can provide a surface at the first end 1201 and / or second end 1202 suitable for undergoing a joining process and / or final machining steps with the end of the heat pipe segment in contact therewith while maintaining structural integrity. Thus, in some embodiments, the body section 1200 can be configured to join with an end portion of a heat pipe segment while maintaining the original strength and / or footprint of the heat pipe segment. Other configurations of the outer wall 1220 are contemplated by the present disclosure. For example, in some implementations, the outer wall 1220 can be configured with an elliptical cross-section, a rectangular cross-section, a hexagonal cross-section, a conical shape, or combinations thereof, including continuous and / or graduated changes in size, thickness, and / or shape along the length of the body section 1200.

[0031] In various examples, the wick 1210 is configured to continue one or more flow paths of an existing heat pipe segment. For example, the portions of the wick 1210 located at the first end 1201 and / or the second end 1202 of the body section can be configured with substantially the same cross-sectional shape as the ends of the wicks of the heat pipe segments to which they are joined. In some examples, the wick 1210 is configured as a cylindrical tube having a thickness and outer diameter that are substantially the same as the thickness and outer diameter of the cylindrical wick of the heat pipe segment to which it is joined with the transition piece 1000. In some embodiments, a wick 1210 incorporating this configuration maintains the characteristics of saturated vapor flow from one heat pipe segment to another. Other configurations of the wick 1210 are contemplated by the present disclosure. For example, in some embodiments, the wick 1210 can be configured to vary in thickness and / or cross-sectional shape from the first end 1201 to the second end 1202.

[0032] In addition to the above, the wick 1210 can be configured to continue peripheral flow between the heat pipe segments connected by the transition piece 1000. For example, the wick 1210 can include a porous region 1215 extending from the first end 1201 to the second end 1202 of the body section 1200. In various examples, the porous region 1215 is formed in a configuration similar to the wick of the heat pipe segment joined to the transition piece 1000. In some examples, the porous region 1215 can be configured with multiple capillary channels. In one example, the porous region 1215 can include an array of channels axially aligned with the body section 1200, as depicted in FIG. 4. Other configurations are contemplated by the present disclosure. For example, in some embodiments, the porous region 1215 can be configured with axial grooves, a granular region with open pores, a region of partially sintered grain, an etched surface, a region with a radial permeability gradient, a region with a lattice-type structure, or any combination thereof.

[0033] In various embodiments, the inner surface 1222 of the outer wall is disposed around the outer surface 1216 of the wick, forming a gap 1230 therebetween. In some examples, the wick 1210 and the outer wall 1220 are concentrically disposed. In some embodiments, the cross-sectional shapes of the wick 1210 and the outer wall 1220 are similarly shaped and nested. Thus, in examples of body section 1200 in which the wick 1210 and / or the outer wall 1220 are configured to vary in cross-sectional shape and / or thickness along the length of the body section 1200, the gap 1230 formed therebetween can have a variable thickness. In one example, upon mating of the existing heat pipe segment with the transition piece 1000, the gap 1230 can be radially aligned with a radially inner portion of the outer wall of the existing heat pipe segment that immediately surrounds the wick of the existing heat pipe segment.

[0034] 2 and 3 , the end portion 1402 of each of the plurality of alignment tabs 1400 extends axially parallel to the head section 1100 and / or tail section 1300, away from the first end 1201 and / or the second end 1202 of the body section 1200, and in alignment with the gap 1230. In various examples, a portion of at least some of the plurality of alignment tabs 1400 is disposed within the gap 1230. In some examples, each of the plurality of alignment tabs 1400 is configured as an elongated member spanning the entire length of the body section 1200, thereby separating the gap 1230 into an angle divider 1232. In the elongated configuration of the plurality of alignment tabs 1400, at least one of the plurality of alignment tabs can include a first end portion 1402 extending away from the first end 1202 and a second end portion 1402b extending away from the second end 1204. In one example, each of the plurality of alignment tabs 1400 is elongated and includes a first end portion 1402a and a second end portion 1402b.

[0035] The plurality of alignment tabs 1400 are configured to facilitate radial and / or rotational alignment of the end of the body section 1200 and the end of the heat pipe segment during mating. For example, the end portion 1402 can be configured to be received by a complementary opening located at the end of the radially inner portion of the outer wall of the heat pipe segment. In one example, the end portion 1402 can be configured as a parallel key having a rectangular cross-sectional shape sized to fit into an axial keyway machined into the end of the outer wall of the heat pipe segment. In a particular example, each of the end portions 1402 can be configured to have a width of about 3 millimeters or less, or about 2 millimeters or less, or about 1 millimeter, and a length of about 2 millimeters or less, or about 1 millimeter. Furthermore, each of the end portions 1402 can be configured to have a thickness of about 2 millimeters or less, or about 1 millimeter. In one example, each of the plurality of alignment tabs 1400 includes two dissimilarly configured end portions.

[0036] Additionally, the number of end portions 1402 can be configured to optimize the amount of machining required for the corresponding heat pipe segment. For example, in some embodiments, the transition piece 1000 can be limited to four or fewer end portions 1402 extending from each end of the body section 1200. A transition piece 1000 incorporating this configuration can minimize the number of alignment tabs 1400 required to facilitate radial and / or rotational alignment with an existing heat pipe segment, thereby minimizing the amount of machining required near the outer surface of the wick of the existing heat pipe segment. Thus, in some embodiments, the transition piece 1000 can be configured to minimize accidental damage to porous regions of the wick of the existing heat pipe segment by minimizing the amount of machining required therein in preparation for the joining process, thereby maintaining an available flow path for condensing fluid from the existing heat pipe segment through the transition piece 1000.

[0037] The multiple alignment tabs 1400 can maintain the positioning of the wick 1210 and the outer wall 1220. For example, in a body section 1200 in which the wick 1210 and / or outer wall 1220 form a gap 1230 of variable thickness, each alignment tab 1400 can be independently configured to vary in thickness to radially bridge a portion of the variable gap 1230 that coincides with the portion of the alignment tab 1400 located in the gap 1230, thereby forming a unitary structure. In examples in which the multiple alignment tabs 1400 are elongated, the thickness of each of the multiple alignment tabs 1400 can be configured to vary along the length of the body section 1200 to radially bridge the gap 1230 and / or maintain contact between the wick 1210 and the outer wall 1220 along the entire length of the body section 1200. In some embodiments, multiple alignment tabs 1400 incorporating this configuration can support radial, rotational, and axial alignment between the wick 1210 and the outer wall 1220. In some embodiments, the wick 1210, the outer wall 1220, and the plurality of alignment tabs 1240 can be integrally formed from a common feedstock by a single molding process, such as an additive manufacturing process, thereby forming a monolithic structure. In one example, the transition piece 1000 is formed as a monolithic structure.

[0038] 5 , a perspective view of a transition piece 2000 is provided in accordance with at least one non-limiting embodiment of the present disclosure. The transition piece 2000 comprises a head section 2100 extending linearly from a first end 2001 to a first axial location 2002, a body section 2200 extending from a first end 2201 disposed at the first axial location 2002 to a second end 2202 disposed at a second axial location 2003, a tail section 2300 extending linearly from the second axial location 2003 to the second end 2004, and three or more alignment tabs 2400.

[0039] FIG. 6 shows a partial cross-sectional schematic view of the transition piece 2000 of FIG. 5 according to at least one non-limiting embodiment of the present disclosure. In various examples, the head section 2100 includes a first tubular segment 2110 and an outer section 2120 surrounding the first tubular segment. The first tubular segment 2110 includes an inner surface 2112 and an outer surface 2114. The head section 2100 can be configured similarly to the head section 1100 described herein above. Accordingly, the first tubular segment 2110 can be configured to connect with an end portion of the first heat pipe segment and continue its central flow path. Additionally, the outer section 2120 can be configured to facilitate its complete removal from the transition piece 2000 without affecting the properties and / or shape of the first tubular segment 2110 and / or the body section 2200.

[0040] 5, tail section 2300 includes a second tubular segment 2310 having an inner surface and an outer surface 2314. Tail section 2300 may be configured similarly to tail section 2100 described herein above. Accordingly, tail section 2300 may be configured to connect with an end portion of the second heat pipe segment and continue its central flow path.

[0041] In some examples, the second tubular segment 2310 can be configured similarly to the first tubular segment 2110. Thus, the transition piece 2000 can be configured to bridge two similarly sized heat pipe segments. Alternatively, the dimensions and / or cross-sectional shapes of the first tubular segment 2110 and the second tubular segment 2310 can be independently configured. Thus, in some embodiments, a transition piece 2000 incorporating this configuration can provide an interface between heat pipe segments having different cross-sectional shapes and / or dimensions.

[0042] 7 shows a body section 2200 including a wick 2210 and an outer wall 2220, according to at least one non-limiting embodiment of the present disclosure. The first end 2201 of the body section 2200 is disposed at a first axial location 2002, and the second end 2202 is disposed at a second axial location 2003. In various examples, the wick 2210 includes an inner surface 2214 defining a cavity therein, a porous region 2215, and an outer surface 2216. The outer wall 2220 includes an inner surface 2222 and an outer surface 2224. The inner surface 2222 of the outer wall is disposed around the wick outer surface 2216, forming a gap 2230 therebetween. Additionally, each of the plurality of alignment tabs 2400 can be elongated to extend through the length of the gap 2230 and includes first and second end portions 2402.

[0043] In some embodiments, the wick 2210 and outer wall 2220 can be configured similarly to other wicks and outer walls, respectively, described elsewhere in this disclosure. For example, the cross-sectional shape, thickness, and relative position of the wick 2210 and outer wall 2220 can be configured to align with the end of the body section 2200 for an existing heat pipe segment without compromising its central fluid flow characteristics. The porous region 2215 of the wick 2210 can be configured to continue peripheral flow between multiple wicks connected by the transition piece 2000.

[0044] The plurality of alignment tabs 2400 can be configured similarly to other plurality of alignment tabs described elsewhere in this disclosure. Thus, each of the plurality of alignment tabs 2400 can be configured to maintain alignment between the wick 2210 and the outer wall 2220, and each of the first and second end portions 2402 can be configured to facilitate rotational alignment during mating of the end of the body section 2200 with the end of the heat pipe segment.

[0045] Additionally, the wick 2210, outer wall 2220, and plurality of alignment tabs 2240 are formed as a single unitary structure by a single molding process, such as an additive manufacturing process, thereby forming a monolithic structure. In one example, the transition piece 2000 is formed as a monolithic structure. Other configurations are contemplated by the present disclosure. For example, in some embodiments, the cross-sectional shape and / or thickness of the wick 2210 and outer wall 2220 can vary along the length of the body section 2200 to connect heat pipe segments of dissimilar configurations.

[0046] The length of the body section 2200 can be configured with directional changes. For example, the lengths of the wick 2210 and outer wall 2220 can include angles, bends, or S-bends, or a combination thereof. In various examples, the body section 2200 includes two 45-degree bend sections 2204 arranged coplanarly. The rotational relationship during the change in direction can be configured to change the offset between the first end 2201 and the second end 2202. For example, as depicted in FIG. 7 , the bend sections 2204 can be complementary positioned to form a 180-degree angle between the first end 2201 and the second end 2202, offsetting them laterally but effectively maintaining the overall direction of flow therethrough. Alternatively, the complementary positioning between the two bend sections 2204 can provide a 90-degree angle therebetween, thereby introducing an angular offset between the ends 2201 and 2202 and changing the direction of flow therethrough. Because the first tubular segment 2110 and the second tubular segment 2310 extend linearly from the end of the body section 2200, the offset between the tubular segments 2110 and 2310 is determined by the configuration of the body section 2200. In some examples, the first tubular segment 2110 and the second tubular segment 2310 are oriented with an angular offset, a lateral offset, or a combination thereof. Thus, the transition piece 2000 can be configured to match the flow between the two offset heat pipe segments.

[0047] In addition to the above, the direction change can be implemented while maintaining any internal dimensional and / or cross-sectional geometric features of the body section 2200. Because the wick 2210, outer wall 2220, and multiple alignment tabs 2400 are integrally formed as a monolithic structure by a single forming process, such as additive manufacturing, implementing bends in the design does not suffer from the dimensional change issues associated with conventional manufacturing processes that must overcome tensile and / or compressive stresses in the starting material to achieve a final shape and / or geometry. For example, subjecting a conventionally manufactured straight section of heat pipe to a bending process can result in significant delamination, cross-sectional collapse, and / or fracture within the heat pipe. In examples where the body section 2200 is formed by additive manufacturing, the body section 2200 can include a bend having a bend radius that is substantially the same as or slightly larger than the outer diameter of the body section 2200. Thus, the body section 2200 can maintain certain design features, such as the morphology of the porous region 2215, throughout the direction change. Other direction change configurations are contemplated by the present disclosure. For example, in some embodiments, the transition piece 3000 can be configured with multiple laterally offset tail sections, as depicted in, for example, FIG. 8, where each tail section requires a dedicated turn.

[0048] In accordance with at least one non-limiting embodiment of the present disclosure, provided herein is a method for manufacturing a transition piece of a heat pipe in a heat transfer system of a nuclear reactor. In various examples, the method includes manufacturing a first section of the transition piece, forming a body of the transition piece using a molding process, and forming a tail section of the transition piece. The body includes a wick surrounded by an outer wall, and the outer surface of the wick and the inner surface of the outer wall are arranged to form a gap therebetween. In some examples, the wick and the outer wall are arranged concentrically. In some examples, the first section, body, and tail section are formed from a common feedstock in a single molding process.

[0049] In various embodiments, the first section is configured to extend axially from the first end of the transition piece to a first axial location, and an inner portion of the first section is configured to connect with the end portion of the first heat pipe segment. In some examples, the first section of the transition piece includes an outer portion surrounding the inner portion, and the outer portion is a sacrificial portion configured to be separated from the transition piece at the first axial location. In certain examples, the method includes removing the sacrificial portion.

[0050] In various embodiments, forming the tail section includes axially extending the tail section from the second axial location to the second end of the transition piece, the tail section configured to connect with an end portion of the second heat pipe segment.

[0051] In various embodiments, forming the body comprises forming a first end of the body at a first axial position and extending the first end of the body to a second axial position. The method can be configured to simultaneously form the wick and outer body. For example, the wick and outer wall can be formed from a common feedstock and / or by an additive manufacturing process, such as powder bed fusion. In some embodiments, methods incorporating this configuration can introduce a change in direction between the first and second ends of the body while maintaining a desired cross-sectional shape and its internal features.

[0052] In some embodiments, forming the body includes forming a porous region of the wick. In one example, the method includes integrally forming an alignment tab with the body, a first portion of the alignment tab maintaining alignment between the wick and the outer wall. In one example, the alignment tab includes an end portion extending axially away from the body past at least one of a first axial position or a second axial position, or a combination thereof. A method of manufacturing a transition piece incorporating additive manufacturing can properly configure radial and rotational positioning of the end portions of the plurality of alignment tabs to radially and rotationally align the transition piece with at least one of the first heat pipe segment or the second heat pipe segment, or a combination thereof.

[0053] A transition piece manufactured by the method for manufacturing a transition piece described herein can be incorporated into a method for manufacturing a heat pipe. For example, as described herein, a joining method for joining segments of a heat pipe in a nuclear reactor is disclosed in accordance with at least one non-limiting embodiment of the present disclosure. In various examples, the joining method can include joining a first end portion of the transition piece with an end portion of a first heat pipe segment and joining a second end portion of the transition piece with an end portion of a second heat pipe segment to produce a heat pipe. Each of the first and second heat pipe segments includes an internal wick section. The joining method is configured to join each of the internal wick sections to form a continuous wick section of the heat pipe. For example, the joining method can include axially inserting the end portion of the transition piece into the end portion of the first and / or second heat pipe segment to rotationally align the wick portion of the transition piece with the internal wick portion of the first and / or second heat pipe segment. In some examples, the joining method can include preparing the end portion of the first and / or second heat pipe segment to receive an alignment tab end portion of the transition piece prior to joining. In certain embodiments, the joining method can include bonding, welding, and / or brazing end portions of the first and / or second heat pipe segments to the transition piece. Joining methods incorporating this configuration can properly orient the first and / or second heat pipe segments in alignment with the transition piece to provide an uninterrupted flow path between the first and second heat pipe segments. Accordingly, joining methods for joining heat pipe segments can join otherwise unusable heat pipe segments to reduce scrap rates, thereby reducing manufacturing costs. Other configurations of the joining methods described herein are contemplated by the present disclosure. For example, in some embodiments, joining methods for joining heat pipe segments can include separately joining three or more heat pipe segments to the transition piece.

[0054] Various aspects of the present disclosure include, but are not limited to, the aspects listed in the following numbered sections.

[0055] (Article 1) A transition piece for joining heat pipe segments in a joining process includes a head section including a first tubular segment, a body section extending from a first end to a second end, a tail section including a second tubular segment, and a plurality of alignment tabs configured to facilitate rotational alignment of the end of the body section with the end of a heat pipe segment during the joining process. The head section extends axially from the first end of the transition piece to a first axial position, and the first tubular segment is configured to connect with an end portion of a first heat pipe segment. The body section further includes a wick having an outer surface, the wick defining a cavity therein, and an outer wall having an inner surface surrounding the outer surface of the wick. The first end of the body section is positioned at the first axial position, and the second end is positioned at a second axial position, and the inner surface of the outer wall and the outer surface of the wick are positioned to form a gap therebetween. The tail section extends axially from the second end of the body section to the second end of the transition piece, the second tubular segment is configured to connect with an end portion of a second heat pipe segment, and each of the plurality of alignment tabs has an end portion extending axially away from the body section, the body section and the plurality of alignment tabs being configured as a unitary structure.

[0056] (Article 2) The transition piece of clause 1, wherein the first tubular segment and the second tubular segment are independently configured in a cylindrical shape.

[0057] (Article 3) 3. The transition piece of clause 2, wherein the first tubular segment and the second tubular segment are configured with different outer diameters.

[0058] (Article 4) 4. A transition piece according to any one of clauses 1 to 3, wherein the cross-sectional shape of the wick varies substantially continuously between the first end of the body section and the second end of the body section.

[0059] (Article 5) A transition piece described in any one of clauses 1 to 4, wherein the first tubular segment and the second tubular segment are oriented with at least one of an angular offset, a lateral offset, or a combination thereof.

[0060] (Article 6) 6. The transition piece of any one of clauses 1 to 5, wherein the body section is formed with a change in direction.

[0061] (Article 7) 7. The transition piece of any one of clauses 1 to 6, wherein the wick is comprised of a porous region.

[0062] (Article 8) A transition piece described in any one of clauses 1 to 7, wherein at least some of the plurality of alignment tabs have portions that extend into the gap formed between the inner surface of the outer wall and the outer surface of the wick.

[0063] (Article 9) 9. The transition piece of clause 8, wherein the portions of the alignment tabs that extend into the gap are integrally formed with the wick and the outer wall.

[0064] (Article 10) A transition piece as described in any one of clauses 1 to 9, wherein the head section comprises a support portion surrounding the first tubular segment, the support portion extending axially from the first end of the transition piece to the first axial position, and the support portion is configured to be removed prior to the joining process.

[0065] (Article 11) 11. The transition piece of any one of clauses 1 to 10, wherein the transition piece is configured as a monolithic structure.

[0066] (Article 12) A method for manufacturing a transition piece for a heat pipe in a nuclear reactor heat transfer system includes manufacturing a first section of the transition piece, forming a body of the transition piece by a molding process, and forming a tail section of the transition piece. The first section is configured to extend axially from a first end of the transition piece to a first axial position, and an inner portion of the first section is configured to connect with an end portion of a first heat pipe segment. The body includes a wick surrounded by an outer wall, and the outer surface of the wick and the inner surface of the outer wall are positioned to form a gap therebetween. Forming the body includes forming a first end of the body at the first axial position and extending the first end of the body to a second axial position. Forming the tail section includes extending the tail section axially from the second axial position to a second end of the transition piece, and the tail section is configured to connect with an end portion of a second heat pipe segment.

[0067] (Article 13) 13. The method of claim 12, wherein the first section of the transition piece comprises an outer portion surrounding the inner portion, the outer portion being a sacrificial portion configured to be separated from the transition piece at the first axial position.

[0068] (Article 14) 14. The method of any one of clauses 12 to 13, wherein the body of the transition piece is formed by an additive manufacturing process.

[0069] (Article 15) 15. The method of any one of clauses 12 to 14, wherein the wick and the outer wall are formed from a common material.

[0070] (Article 16) 16. The method of any one of clauses 12 to 15, wherein the wick and the outer wall are concentrically arranged.

[0071] (Article 17) 17. The method of any one of clauses 12 to 16, wherein the forming process is configured to have at least one directional change to extend the body from the first axial position to the second axial position.

[0072] (Article 18) 18. The method of any one of clauses 12 to 17, wherein the method comprises integrally forming an alignment tab with the body, a first portion of the alignment tab maintaining alignment of the wick and the outer wall, the alignment tab extending axially away from the body past at least one of the first axial position or the second axial position, or a combination thereof, and the alignment tab configured to rotationally align the transition piece with at least one of the first heat pipe segment or the second heat pipe segment, or a combination thereof.

[0073] (Article 19) A method of joining segments of a heat pipe in a nuclear reactor comprises joining a first end portion of a transition piece to an end portion of a first heat pipe segment and joining a second end portion of the transition piece to an end portion of a second heat pipe segment to produce the heat pipe, wherein the transition piece, the first heat pipe segment, and the second heat pipe segment each include an internal wick section, and each of the internal wick sections is joined to form a continuous wick section of the heat pipe.

[0074] (Article 20) 20. The method of claim 19, wherein the method comprises separately joining three or more heat pipe segments to the transition piece.

[0075] Various features and characteristics are described herein to provide an understanding of the organization, structure, manufacture, function, and / or operation of the present disclosure, including the disclosed methods and systems. It is understood that the various features and characteristics of the present disclosure described herein may be combined in any suitable manner, whether or not such features and characteristics are explicitly described in combination herein. The inventors and applicants expressly intend that such combinations of features and characteristics be included within the scope of the disclosure described herein. Accordingly, the claims may be amended to recite any combination of features and characteristics explicitly or inherently described herein or explicitly or inherently incorporated herein. Furthermore, applicants reserve the right to amend the claims to affirmatively disclaim any features or characteristics that may exist in the prior art, even if those features or characteristics are not explicitly described herein. Accordingly, such amendments do not add new matter to the specification or claims, but rather comply with the requirements of the specification, specification sufficiency, and additional matter.

[0076] With respect to the appended claims, those skilled in the art will understand that the operations described therein may generally be performed in any order. Also, while various operational flows are shown in a sequential order, it should be understood that various operations may be performed in orders other than those shown, or may be performed simultaneously. Examples of such alternative orders include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, concurrent, reversed, or other variant orders, unless the context dictates otherwise. Furthermore, terms such as "corresponding to," "related to," or other past tense adjectives are generally not intended to exclude such variants, unless the context dictates otherwise.

[0077] The inventions described herein can comprise, consist of, or consist essentially of various features and characteristics described herein. The terms "comprise" (and any form of "comprising," such as "comprises" or "comprising"), "have" (and any form of "have," such as "has" or "having"), "include" (and any form of "including," such as "includes" or "including"), and "contain" (and any form of "contain," such as "contains" or "containing") are open-ended linking verbs. Thus, a method or system that "comprises," "has," "includes," or "contains" a feature or characteristics and / or properties possesses that feature or those characteristics and / or properties, but is not limited to possessing only that feature or those characteristics and / or properties. Similarly, elements of a composition, coating, or process that "comprises," "has," "includes," or "contains" a feature and / or property possess the feature and / or property, but are not limited to possessing only the feature and / or property, and may possess additional features and / or properties.

[0078] As used herein, including the claims, the grammatical articles "a," "an," and "the" are intended to include "at least one" or "one or more," unless otherwise indicated. Accordingly, articles are used herein to refer to one or more than one (i.e., "at least one") of the grammatical object of the article. As an example, "component" means one or more components; therefore, more than one component is contemplated and may be employed or used in the practice of the described compositions, coatings, and processes. Nevertheless, the use of the terms "at least one" or "one or more" in some instances and not in others is understood not to construe the grammatical articles "a," "an," and "the" as limiting the object to one. Furthermore, the use of singular nouns includes the plural, and the use of plural nouns includes the singular.

[0079] As used herein, unless otherwise indicated, all numerical parameters are understood to be prefaced and modified in all instances by the term "about," given the inherent variability inherent in the underlying measurement techniques employed to determine the numerical value of such parameters. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter set forth herein should, at the very least, be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0080] Numerical ranges recited herein include all subranges subsumed within the recited range. For example, a range of "1 to 10" includes all subranges between (and including) the recited minimum of 1 and the recited maximum of 10, i.e., having a minimum of 1 or more and a maximum of 10 or less. Also, all ranges recited herein include the endpoints of the recited range. For example, a range of "1 to 10" includes the endpoints 1 and 10. Every maximum numerical limitation recited herein is intended to include all subnumerical limitations subsumed therein, and every minimum numerical limitation recited herein is intended to include all upper numerical limitations subsumed therein. Accordingly, applicants reserve the right to amend this specification, including the claims, to expressly describe any subranges subsumed within any explicitly recited range. All such ranges are inherently described herein.

[0081] As used herein, particularly in reference to layers, the terms "on," "up," "onto," and variations thereof (e.g., "coated on," "formed on," "deposited on," "provided on," "located on," etc.) mean coated, formed, deposited, provided, or otherwise located on the surface of a substrate, but not necessarily in contact with the surface of the substrate. For example, a layer "coated" on a substrate does not exclude the presence of another layer or other layer, of the same or different composition, located between the coated layer and the substrate. Similarly, a second layer "coated" on a first layer does not exclude the presence of another layer or other layer, of the same or different composition, located between the coated second layer and the coated first layer.

[0082] While particular embodiments of the present disclosure have been described above for purposes of illustration, it will be apparent to those skilled in the art that many changes in the details of the present disclosure can be made without departing from the present disclosure as defined in the appended claims.

Claims

1. A transition piece for joining heat pipe segments in a joining process, comprising: a head section including a first tubular segment, the head section extending axially from a first end of the transition piece to a first axial location, the first tubular segment configured to connect with an end portion of a first heat pipe segment; a body section extending from a first end to a second end, the body section comprising: a wick having an outer surface, the wick defining a cavity therein; and an outer wall having an inner surface surrounding the outer surface of the wick, the first end being disposed at the first axial position and the second end being disposed at a second axial position, the inner surface of the outer wall and the outer surface of the wick being disposed to form a gap therebetween; a tail section including a second tubular segment, the tail section extending axially from the second end of the body section to the second end of the transition piece, the second tubular segment configured to connect with an end portion of a second heat pipe segment; a transition piece comprising: a plurality of alignment tabs configured to facilitate rotational alignment of the end of the body section and the end of the heat pipe segment during the joining process, each of the plurality of alignment tabs having an end portion extending axially away from the body section, the body section and the plurality of alignment tabs being configured as a unitary structure.

2. The transition piece of claim 1 , wherein the first tubular segment and the second tubular segment are independently configured in a cylindrical shape.

3. The transition piece of claim 2 , wherein the first tubular segment and the second tubular segment are configured with different outer diameters.

4. 10. The transition piece of claim 1, wherein the cross-sectional shape of the wick varies substantially continuously between the first end of the body section and the second end of the body section.

5. The transition piece of claim 1 , wherein the first tubular segment and the second tubular segment are oriented with at least one of an angular offset, a lateral offset, or a combination thereof.

6. The transition piece of claim 1 , wherein the body section is formed with a change in direction.

7. The transition piece of claim 1 , wherein the wick is comprised of a porous region.

8. The transition piece of claim 1 , wherein at least some of the alignment tabs include a portion that extends into the gap formed between the inner surface of the outer wall and the outer surface of the wick.

9. The transition piece of claim 8 , wherein the portions of the plurality of alignment tabs that extend into the gap are integrally formed with the wick and the outer wall.

10. 2. The transition piece of claim 1, wherein the head section comprises a support portion surrounding the first tubular segment, the support portion extending axially from the first end of the transition piece to the first axial position, and the support portion configured to be removed prior to the joining process.

11. The transition piece of claim 1 , wherein the transition piece is configured as a monolithic structure.

12. 1. A method for manufacturing a transition piece for a heat pipe in a heat transfer system of a nuclear reactor, comprising: fabricating a first section of the transition piece, the first section configured to extend axially from a first end of the transition piece to a first axial location, an inner portion of the first section configured to connect with an end portion of a first heat pipe segment; forming a body of the transition piece by a molding process, the body comprising a wick surrounded by an outer wall, the outer surface of the wick and the inner surface of the outer wall being arranged to form a gap therebetween, forming the body comprising: forming a first end of the body at the first axial position; and extending the first end of the body to a second axial position; forming a tail section of the transition piece, wherein forming the tail section comprises axially extending the tail section from the second axial position to a second end of the transition piece, the tail section being configured to connect with an end portion of a second heat pipe segment.

13. 13. The method of claim 12, wherein the first section of the transition piece comprises an outer portion surrounding the inner portion, the outer portion being a sacrificial portion configured to be separated from the transition piece at the first axial position.

14. The method of claim 12 , wherein the body of the transition piece is formed by an additive manufacturing process.

15. The method of claim 12 , wherein the wick and the outer wall are formed from a common material.

16. The method of claim 12 , wherein the wick and the outer wall are concentrically disposed.

17. The method of claim 12 , wherein the forming process is configured to have at least one change of direction to extend the body from the first axial position to the second axial position.

18. 13. The method of claim 12, further comprising: integrally forming an alignment tab with the body, a first portion of the alignment tab maintaining alignment of the wick and the outer wall, the alignment tab extending axially away from the body past at least one of the first axial position or the second axial position, or a combination thereof, and the alignment tab configured to rotationally align the transition piece with at least one of the first heat pipe segment or the second heat pipe segment, or a combination thereof.

19. 1. A method of joining segments of a heat pipe in a nuclear reactor, comprising: joining a first end portion of the transition piece to an end portion of the first heat pipe segment; and joining a second end portion of the transition piece with an end portion of a second heat pipe segment to produce the heat pipe; The method, wherein the transition piece, the first heat pipe segment, and the second heat pipe segment each comprise an internal wick section, and each of the internal wick sections are coupled to form a continuous wick section of the heat pipe.

20. The method of claim 19, comprising separately joining three or more heat pipe segments to the transition piece.

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