A nuclear fission reactor equipped with a segment cladding body having cladding arms with an involute curve shape.

Abstract

The present invention provides a nuclear fission reactor structure and a method for manufacturing the same that comply with neutron engineering and thermal management requirements for nuclear fission reactors, while reducing manufacturing complexity and variability. [Solution] Multiple layers form a nuclear fission reactor structure. Each layer has an inner segment body, an intermediate segment body, and an outer segment body (each segment body is separated by a contact surface). The layer includes multiple cladding arms having an involute curve shape that radiates outward in a helical manner from the radially inner end to the radially outer end. The chambers of the involute curve cladding arms contain the fuel composition (and / or other materials such as moderators and interfering materials).

Description

[Technical Field]

[0001] This disclosure generally relates to structures relating to fission reactors and nuclear fission reactor spaces within them. In particular, thermogenerating structures, such as fuel elements containing fissile nuclear fuel compositions, are covered by containment structures such as cladding. The thermogenerating structures have involute curve shapes, and multiple such shapes are assembled to form a cylindrical reactor layer. The involute curve shapes vary based on the radial position of the cylindrical reactor layer, but the homogenization of the involute curve shapes minimizes the number of unique shapes of fuel elements (or other features such as moderators and / or poisons) that are fed into each thermogenerating structure to achieve a desired reactor performance profile. The involute curve shapes of the thermogenerating structures allow for the homogenization of the thickness of the fuel elements and cladding, and for the homogenization of the coolant space between individual thermogenerating structures. This disclosure is particularly suited to the manufacture of cladding structures of thermogenerating structures, at least those with involute curve shapes, by additive manufacturing processes. The disclosed fission reactor is suitable for use in a variety of applications, including power sources for small vessels (such as spacecraft and satellites), nuclear thermal propulsion (NTP), and isotope production. [Background technology]

[0002] In the following discussion, specific structures and / or methods will be referred to. However, the following references should not be construed as acknowledging that these structures and / or methods constitute prior art. The applicant expressly reserves the right to demonstrate that such structures and / or methods are not appropriate prior art to the present invention.

[0003] When designing new thermogenerative functions and structures for nuclear fission reactors, adequate cooling of each fuel element throughout the entire fission reactor space is often a limiting design factor. In previous reactor designs, uranium fuel was sealed in rolled metal sheets by, for example, a cold rolling process. Referring to the schematic diagram in Figure 1, the arrangement of layer 1, including the fuel composition layer 2 between two cladding layers (first cladding layer 4a and second cladding layer 4b), is supplied to the nip of the roller 6 of the cold rolling mill. The cold rolling process reduces the thickness of the arrangement of layer 1 from an initial thickness to a final thickness in one or more cold rolling steps. In this process, various layers of material (in the illustrated example, a fuel composition layer 2 and two cladding layers 4a and 4b) are metallurgically bonded to a single-layer structure 8 (shown in cross-section in Figure 1), where cladding layers 4a and 4b provide sealing layers on both sides of the fuel composition layer 2 (shown by dashed lines at the interface between the fuel composition layer 2 and the two cladding layers 4a and 4b in Figure 1). Whether formed in a strip or plate shape, the unit layer structure 8 can be further processed using conventional metal forming techniques. In one embodiment, such a plate-shaped unit layer structure 8 is curved into an involute shape and incorporated into the core assembly of a High Flux Isotope Reactor (HFIR) 10, a nuclear research reactor at Oak Ridge National Laboratory (ORNL) (a partial cross-sectional view is shown in Figure 1). In the HFIR design, the involute shape 12 provides a uranium / cladding plate of uniform thickness positioned between the homogenized coolant spaces.

[0004] The single-layer structure and involute shape in HFIRs have several drawbacks that reduce design flexibility. For example, to comply with neutron engineering and thermal management requirements, the composition of fuel composition layer 2 is spatially non-uniform with respect to its position within the plate or strip, and is adjusted based on its position within the core assembly. However, at the same time, the composition and layer distribution of the single-layer structure are fixed during the process of combining fuel composition layer 2 with the two cladding layers 4a and 4b, for example, during cold rolling. Therefore, the structure at each location in the HFIR must have its own uniquely constructed single-layer structure, and these uniquely constructed single-layer structures are not interchangeable with other forms. [Overview of the project]

[0005] Considering the above, it would be advantageous to allow for more flexible variations in the shape, position, and composition of clad fuel elements in the core assembly. Furthermore, meeting the neutron engineering and thermal management requirements in fission reactor design would be advantageous because it would reduce the complexity of component manufacturing and fission reactor assembly while minimizing geometric and compositional variations in clad fuel elements. In addition, modular, repeatable, and sufficiently sized designs would enable the application of manufacturing methods such as additive manufacturing.

[0006] The neutron engineering and thermal performance of fuel elements in the core design of a nuclear fission reactor are influenced, in particular, by the structure of the fuel elements, the cladding surrounding them, and the coolant channels, such as their shape, size, and relative position, and by the heat transport characteristics of the fuel elements, cladding, and coolant. As described above, alternative designs are needed to improve design and manufacturing flexibility and reliability while satisfying the neutron engineering and thermal performance requirements of the fuel elements.

[0007] In one example of an alternative design (see Figure 2), layers containing a series of radially concentric fuel rings 32 (60-degree portions 30 of the layers are shown in Figure 2) are assembled in a cylindrical fission reactor space. In each fuel ring 32, the fuel ring edge 34a and internal webbing 34b function as cladding, defining a volume containing a bowtie-shaped fuel composition 36. The edge 34a and webbing 34b can also define the shape of a coolant channel 38 having a circular cross-section in Figure 2. The volume containing the fuel composition 36 has the same cross-sectional area in each fuel ring 32. Similarly, the coolant channel 38 in each fuel ring 32 has the same cross-sectional area. For neutron engineering and thermal management purposes, each fuel ring 32 requires a different fuel composition (for a constant fuel cross-sectional area) or a different fuel shape (for a constant fuel composition). For example, a fuel composition sized to fit ring 32b cannot be used in ring 32f and will not function well from a neutron engineering and thermal management standpoint. Therefore, in further examples, the 10-ring design shown in Figure 2 would require several different fuels with one or more variations in fuel composition and fuel shape.

[0008] Another example of an alternative design (shown in Figures 3A and 3B) involves assembling a layer containing pockets 52 for fuel elements 54 distributed concentrically and radially within a portion 50 (a 15-degree portion 50 of the layer is shown in Figures 3A and 3B). Multiple portions 50 can be assembled into a cylindrical fission reactor space. Compared to the example in Figure 2, the examples in Figures 3A and 3B change the shape of the fuel elements 54 from a bowtie shape to a more triangular or rectangular shape. Elliptical coolant holes 56 are located in clad web structures 58 between each pocket 52. As with the example in Figure 2, each fuel element 54 of different size and position requires a different fuel composition or different fuel shape, and overall, the examples in Figures 3A and 3B would also require a sufficiently large number of different fuels with one or more variations in fuel composition and fuel shape (although the change from bowtie shape to a more triangular or rectangular shape simplifies the manufacture of such elements, as well as the manufacture of such elements with various fuel compositions). However, neutron engineering and thermal performance analyses for the design shown in Figures 3A and 3B proved that, among the various different shapes and locations for the fuel element, the only fuel element shape that could be adequately cooled was the thin fuel element 54a at the outermost radial position, i.e., the fuel element with the largest length-to-width ratio.

[0009] The two examples above illustrate the challenges in designing thermogenerative functions and structures for fission reactors that meet neutron engineering and thermal performance standards, and that are sufficiently common and / or have sufficiently low variability to reduce manufacturing complexity and manufacturing variability (and thereby reduce the likelihood of manufacturing defects).

[0010] Generally, this disclosure relates to a fission reactor structure in which fuel elements comprising a fissile nuclear fuel composition are arranged along the axis of an involute-shaped encapsulation cladding structure. Multiple such involute-shaped cladding structures are arranged to form rings, and multiple concentric rings are arranged to form layers of a fission reactor structure. Multiple layers themselves are assembled to form a fission reactor structure. In exemplary embodiments, the fission reactor structure is the active core region of the fission reactor.

[0011] Embodiments disclosed herein also include a fission reactor structure comprising multiple layers. Each of the multiple layers comprises an inner segment body including an inner opening extending axially from a first side surface of the inner segment body to a second side surface of the inner segment body, an intermediate segment body radially outward from the inner segment body, and an outer segment body radially outward from the intermediate segment body. A first interior interface separates the inner segment body from the intermediate segment body, and a second interior interface separates the intermediate segment body from the outer segment body. In a cross-sectional plan view in a plane perpendicular to the axially extending inner opening, the inner segment body includes a plurality of inner cladding arms having a first involute curve shape that radiates outward in a helical manner from a first radially inward end adjacent to the inner opening to a first radially outward end of the first interior interface. The intermediate segment body includes a plurality of intermediate cladding arms having a second involute curve shape that radiates outward in a helical manner from a second radially inner end adjacent to the first internal contact surface to the second radially outer end of the second internal contact surface. The outer segment body includes a plurality of outer cladding arms having a third involute curve shape that radiates outward in a helical manner from a third radially inner end adjacent to the second internal contact surface to the third radially outer end of the radially outer surface of the outer segment body.

[0012] Embodiments disclosed herein also include a fission reactor comprising a plurality of layers disclosed herein. The plurality of layers are assembled into a fission reactor structure having a first end face, a second end face, and an outer surface connecting the first end face to the second end face. Also included are radial reflectors positioned around the outer surface of the active core structure, a pressure vessel, and a coolant system in fluid communication with the active core structure through an opening in the pressure vessel.

[0013] Embodiments disclosed herein also include methods for manufacturing fission reactor structures disclosed herein. The method comprises manufacturing an inner segment body, an intermediate segment body segment, and an outer segment body segment, wherein each of a plurality of inner cladding arms, a plurality of intermediate cladding arms, and a plurality of outer cladding arms comprises a plurality of chambers, wherein the segment body forms a fuel-loaded layer by placing one of a fissile fuel composition and a moderator, assembled by welding and joining, in the plurality of chambers, and assembling the plurality of fuel-loaded layers into a fission reactor structure.

[0014] In an alternative embodiment of the method for manufacturing a fission reactor structure disclosed herein, the method comprises manufacturing a layer comprising an inner segment body, an intermediate segment body, and an outer segment body as a single structure, wherein each of the plurality of inner cladding arms, plurality of intermediate cladding arms, and plurality of outer cladding arms comprises a plurality of chambers, wherein one of a fissile fuel composition and a moderator is placed in the plurality of chambers to form a fuel loading layer, and the plurality of fuel loading layers are assembled into a fission reactor structure.

[0015] Furthermore, although the disclosed reactors and cores have complex mechanical shapes, the structures and features disclosed herein can be more easily manufactured by manufacturing them layer by layer integrally and iteratively using additive manufacturing techniques such as 3D printing of elemental metals or metal alloys.

[0016] The above overview and the following detailed description of the embodiments can be better understood when read in conjunction with the attached drawings. It should be understood that the illustrated embodiments are not limited to the exact arrangement and means. [Brief explanation of the drawing]

[0017] [Figure 1] This diagram schematically illustrates the structure and process related to the formation of cladding in a prior art high neutron flux isotope reactor (HFIR). [Figure 2] In the first embodiment, the assembled layers schematically show the 60-degree portion of the layers in a design that includes a series of radially concentric fuel rings. [Figure 3A-3B] Figure 3A schematically shows a 15-degree portion of the layer of the design in the second embodiment, which includes pockets for concentrically and radially distributed fuel elements, and Figure 3B schematically shows the same portion with fuel elements partially inserted into the pockets. [Figure 4] A schematic partially exploded perspective view illustrating a simplified example of a fission reactor assembled from layers of a third embodiment, each having a series of concentric segment bodies, each containing a cladding arm having a first involute curve shape. [Figure 5] A schematic top view showing a series of concentric segment bodies assembled in layers, each having an involute curve shape. [Figure 6A-6C] Figure 6A is a schematic top view showing an embodiment of the inner segment body, Figure 6B is a partially enlarged view of the inner segment body shown in Figure 6A, and Figure 6C is a diagram showing an example of the surface features of the end of the cladding arm. [Figures 7A-7B]FIG. 7A is a top view schematically showing an embodiment of an intermediate segment body, and a partially enlarged view of the intermediate segment body shown in FIG. 7A [Figure 8A-8B] FIG. 8A is a top view schematically showing an embodiment of an outer segment body, and FIG. 8B is a partially enlarged view of the outer segment body shown in FIG. 8A [Figure 9] A diagram showing an example where the involute-shaped curved surface of the cladding arm is continuous across the inner segment body, the intermediate segment body, and the outer segment body [Figure 10] A diagram showing an example of a layer in which each of the inner cladding arms can include six chambers, and each of the intermediate cladding arms and the plurality of outer cladding arms can include two chambers [Figure 11] A diagram schematically showing an example of a cladding arm [Figure 12] A diagram showing an embodiment of a layer including an inner body segment 502, an intermediate segment body 504, and an outer segment body, each including a plurality of chambers and a plurality of fuel composition bodies located on each segment body [Figures 13A-13B] FIG. 13A is a diagram showing the results of a thermal analysis study in an involute curve-shaped cladding arm design disclosed herein, and FIG. 13B is a partially enlarged view of the inner segment cladding arm shown in FIG. 13A [Figure 14A-14D] FIG. 14A is a flowchart showing the steps of assembling a layer from various parts of a segment body, FIG. 14B is a flowchart showing the steps of assembling a layer from various parts of a segment body, FIG. 14C is a flowchart showing the steps of loading a fuel composition and / or a moderator composition and interfering substances into a layer, and FIG. 14D is a flowchart showing the steps of assembling a plurality of layers into a nuclear fission reactor structure [Figure 15] A side cross-sectional view schematically showing an embodiment of a nuclear fission reactor including a plurality of layers assembled into a nuclear fission reactor structure

Embodiments for Carrying Out the Invention

[0018] For clarity, in some examples, only some of the named features in the diagram are given reference numerals.

[0019] Figure 4 is a schematic exploded view showing a simplified exemplary embodiment of a fission reactor 100. The fission reactor 100 comprises a plurality of layers 102 assembled on a fission reactor core structure 104 having a first end face 106, a second end face 108, and an outer surface 110 connecting the first end face 106 and the second end face 108, positioned along the longitudinal axis 112 of the active core structure 104. The layers 102 are defined by an inner segment body, an intermediate segment body, an outer segment body, a first internal contact surface, and a second internal contact surface, as will be further described herein. The fission reactor 100 also comprises radial reflectors 114 positioned around the outer surface 110 of the active core structure 104. Although the active core structure 104 is shown as a cylindrical structure, any suitable geometric shape can be utilized as long as the active core structure exhibits any neutron engineering and thermal management characteristics. In an exemplary embodiment, the activated core structure 104 has a diameter (D RX Length of the activated core region (L) relative to ) RX The ratio of ) is approximately 1 (i.e., L RX / D RX The radial reflector 114 has sufficient layers 102 such that the effective multiplication factor (k) is 1 ± 0.05. Generally, the radial reflector 114 reduces neutron leakage from the fission reactor 100 by scattering (or reflecting) neutrons that would otherwise escape back into the core. For this reason, the effective multiplication factor (k) is designed to be sufficient. eff This increases the amount of fuel required to maintain criticality. A coolant system (informably shown schematically as pressure vessel 120 and coolant system 130) is also provided, which is in fluid communication with the activated core structure through an opening in the pressure vessel.

[0020] Any suitable radial reflector, pressure vessel, and coolant system can be incorporated into the fission reactor 100. For example, the coolant system may be liquid-based or gas-based. If the coolant system is gas-based, multiple layers 102 can be assembled into the active core structure 104 by welding the inner and outer surfaces of adjacent layers 102 together using weld joints, i.e., contact surfaces corresponding to the outer surfaces of adjacent layers 102, to provide an airtight, open cylindrical shape with an annulus cross-section. In a gas-based coolant system, only the outermost surface needs to be airtight, as it is permissible for the gas to circulate throughout the entire active core region. If the coolant system is liquid-based, the opposing surfaces of adjacent layers 102 are joined together such that the coolant channels are separated from each other, while each provides a continuous path of coolant across the active core structure from a first end to a second end.

[0021] Alignment aids can be used to assist in aligning features, such as coolant channels, in one layer 102 with features in an adjacent layer 102. A clocking technique can be applied using protruding registry features on the surface of a mated or inserted layer 102, for example, by insertion or acceptance into a receiving space on the adjacent surface of the adjacent layer 102. Other registry features, including pins, notches, and molded protrusions, can also be used. Furthermore, other alignment aids, such as alignment channels or scribe marks, can also be used. The alignment aids can also be positioned on one or more suitable surfaces, including adjacent inner surfaces and continuous outer surfaces 110.

[0022] The disclosed fission reactor structure comprises multiple layers. Each layer includes a series of concentrically arranged segment bodies. Each segment body includes cladding arms having an involute curve shape. Figure 5 is a schematic top view showing a series of concentric segment bodies 210, 240, and 270. Each of these includes cladding arms having a first involute curve shape assembled to layer 200. In an exemplary embodiment, the fission reactor structure comprises an inner segment body 210, an intermediate segment body 240, and an outer segment body 270. The intermediate segment body 240 is radially outward of the inner segment body 210, and the outer segment body 270 is radially outward of the intermediate segment body 240. A contact surface separates one segment body from radially adjacent continuous segment bodies. For example, the first internal contact surface 212 separates the inner segment body 210 from the intermediate segment body 240, and the second internal contact surface 242 separates the intermediate segment body 240 from the outer segment body 270.

[0023] A fission reactor structure includes an internal opening that extends axially from a first axial end to a second axial end of the fission reactor structure (typically corresponding to the longitudinal axis of the fission reactor structure). This internal opening can function as a coolant channel, but it can also function to house reactor control devices, control rods, sensors, or radioisotope production equipment (either in combination with or independently of the coolant channel). Each layer has a corresponding internal opening that defines a portion of the internal opening when multiple layers are assembled in a fission reactor structure.

[0024] Figure 5 shows embodiments of layer 200 in a top view of the layer and a plan view of the cross section relative to the assembled fission reactor, in a plane perpendicular to the axis of the axially extending inner opening 202. Layer 200 includes an inner segment body 210 containing an inner opening 202 that extends axially from a first side surface 204 to a second side surface 206 of layer 200. Layer 200 also includes an intermediate segment body 240 radially outward from the inner segment body 210 and an outer segment body 270 radially outward from the intermediate segment body 240. The concentrically arranged segment bodies 210, 240, and 270 are joined to each other to form layer 200 at the contact surface. The segment bodies can be joined to form the contact surface by any suitable means. In some embodiments, the segment bodies can be joined to form the contact surface by welding. In other embodiments, the segment bodies can be joined to form the contact surface by compression fitting. In either case, the first internal contact surface 212 separates the inner segment body 210 from the intermediate segment body 240, and the second internal contact surface 242 separates the intermediate segment body 240 from the outer segment body 270.

[0025] Figure 6A shows embodiments of the inner segment body 210 in a top view of the inner segment body 210 and a cross-sectional plan view of the assembled fission reactor structure, in each case in a plane perpendicular to the axis of the axially extending inner opening 202. Figure 6B is an enlarged view showing a portion P1 of the inner segment body 210 shown in Figure 6A. The inner segment body 210 includes a plurality of inner cladding arms 214 having a first involute curve shape that radiates outward in a helical manner from a first radially inner end 216 adjacent to the inner opening 202 to a first radially outer end 218 of an outer edge 220 which forms or is part of a first inner contact surface 212 in the assembled layer 200. The plurality of inner cladding arms 214 include a plurality of chambers 222. The plurality of chambers 222 are distributed along the length of the inner cladding arms 214. In each cladding arm 214, each chamber 222 is enclosed within the web 224 of the material forming the inner segment body 210, such that each chamber 222 is surrounded by the web 224, and the first chamber 222a is separated from the adjacent chamber 222b by a portion of the web 224. As described herein, the chambers 214 contain a fissile fuel composition (or other compositions such as moderators and interfering materials), and the web 224 functions as cladding for the fissile fuel composition or other compositions.

[0026] One or more coolant openings 230 are positioned between a plurality of chambers 222 of one cladding arm 214 and a plurality of chambers 222 of an adjacent inner cladding arm 214 (for example, between a chamber 222c of one inner cladding arm 214a and a chamber 222d of an adjacent cladding arm 214b (see Figure 6B)). The coolant openings 230 extend through the inner cladding arm 214 in the thickness direction of the inner segment body 210, from the first side surface 204' of the inner segment body 210 to the second side surface 206' of the inner segment body 210.

[0027] The coolant opening 230 can take various forms. For example, if the web 224 of the inner segment body 210 is a single body, the coolant opening 230 is one or more passages, channels, or other openings that can be formed in the web during the initial web manufacturing, for example, during the layer-by-layer deposition process of an additive manufacturing process, or after web manufacturing by a material removal process such as drilling, milling, plunge milling, or by using an electrical discharge machining (EDM) process. In another example, if each cladding arm 214 is formed as a single body and multiple cladding arms 214 are joined to form an inner segment body 210, the coolant opening 230 is a passage or other opening formed by features on the edge of the inner cladding arm 214, i.e., the surface of the inner cladding arm 214 forming the first side surface 204' of the inner segment body 210, the surface of the inner cladding arm 214 forming the second side surface 206' of the inner segment body 210, the surface of the first radially inner end 216 of the inner cladding arm 214, and the surface of the first radially outer end 218 of the inner cladding arm 214. In this regard, the edge of the cladding arm 214 may include grooves, ribs, protrusions, or other surface features that, when in contact with the edge of an adjacent cladding arm 214, form one or more passages, channels, or other openings.

[0028] In some embodiments, the surface feature is an inconspicuous area located along the periphery of an edge. In other embodiments, the surface feature extends continuously or discontinuously along at least one opposing side from a first end toward a first side of the inner segment body to a second end toward a second side of the inner segment body. Combinations of different surface features can also be implemented. Furthermore, the surface feature may be present on only one edge of the cladding arm or on both edges of the cladding arm. As an example, the surface feature is a projection. Non-limiting examples of projections include features that have similarities to bumps, knobs, or mesa-like features, and include both regular and irregular shapes.

[0029] The surface feature has an upper surface distal to at least one opposing side from which the projection protrudes. When assembled to a segment body having an immediately adjacent cladding arm, the upper surface of the projection contacts the opposing side of the immediately adjacent cladding arm, and the height or projection distance of the projection provides a stand-off separation between the two cladding arms. This stand-off separation forms a channel between the two cladding arms. In some embodiments, where present, such surface features may be offset along the radially extending length of the cladding arm 214 so that the position of the surface feature does not coincide with the portion of the web 224 that separates the first chamber 222a from the adjacent chamber 222b. Different combinations of coolant openings can also be implemented. As an example, Figure 6C shows a surface feature (in this case, a rib 234) on the edge of a cladding arm (in this case, an example of an inner cladding arm 214). However, surface features may also be present on the edge surfaces and on one or more of the inner cladding arms 214, intermediate cladding arms 244, and outer cladding arms 272.

[0030] In some embodiments, it is preferable that the inner segment body 210 be formed as a single body to avoid welding or other structures on the surface that would otherwise be present from joining individual cladding arms 214 or groups of cladding arms 214 to form the inner diameter of the opening 202.

[0031] To make the involute curve shape of the inner cladding arm 214 easier to see, an embodiment of the inner cladding arm 214 is schematically shown in Figure 6A. In the illustrated embodiment, the two curved sides 232a and 232b of the involute curve shape of the inner cladding arm 214 are located on lines connecting to the midpoints of the web 224 located between a plurality of chambers 222 in one cladding arm 214 and a plurality of chambers 222 in an adjacent cladding arm 214. The involute curve shape itself may have a constant width (i.e., the width is the distance between the two opposing curved sides 232a and 232b of the involute curve shape of the inner cladding arm 214) as a function of the position along the axis of the involute curve shape extending from the midpoint of the first radially inner end 216 to the midpoint of the first radially outer end 218. Alternatively, the width of the involute curve shape may vary as a function of the position along the axis of the involute curve shape extending from the midpoint of the first radially inner end 216 to the midpoint of the first radially outer end 218. For example, the width of the involute curve shape may continuously increase or continuously decrease as a function of the position along the axis of the involute curve shape extending from the midpoint of the first radially inner end 216 to the midpoint of the first radially outer end 218.

[0032] Figure 7A shows embodiments of the intermediate segment body 240 in a top view of the intermediate segment body 240 and a cross-sectional plan view of the assembled fission reactor structure, in each case in a plane perpendicular to the axis of the axially extending internal opening 202. Figure 7B is an enlarged view showing a portion P2 of the intermediate segment body 240 shown in Figure 7A. In Figure 7A, the intermediate segment body 240 is shown in the context of the inner segment body 210 and outer segment body 270 that form layer 200.

[0033] The intermediate segment body 240 includes an inner cladding arm 244 having a second involute curve shape that radiates outward in a helical manner from a second radially inner end 246 adjacent to an inner opening 248 that forms or is part of a first internal contact surface 212 in the assembled layer 200, to a second radially outer end 250 at an outer edge 256 that forms or is part of a second internal contact surface 242 in the assembled layer 200. A plurality of intermediate cladding arms 244 include at least one chamber 252, or a plurality of chambers 252a, 252b (see also Figures 9 and 10, for example). In Figure 7B, the chamber 252 is shown for only two intermediate cladding arms 244, but additional intermediate cladding arms 244, or alternatively all intermediate cladding arms 244, may include one or more chambers 252. The chambers 252 extend along the length of the intermediate cladding arm 244, or, if multiple chambers are included, the chambers 252a, 252b are distributed along the length of the intermediate cladding arm 244. The chambers 252 (or, if multiple chambers are included, the chambers 252a, 252b) are contained within the web 254 of the material forming the intermediate segment body 240, so that an individual chamber 252 is enclosed within the web 254 in each intermediate cladding arm 244. Furthermore, if multiple chambers 252 are included, the first chamber 252a is separated from the adjacent chamber 252b by a portion of the web 254 (see also Figures 9 and 10). As described herein, the chambers 252 may contain a fissile fuel composition (or other compositions such as moderators and interfering materials), and the web 254 functions as cladding for the fissile fuel composition or other compositions.

[0034] Similar to the inner segment body 210, the intermediate segment body 240 may include one or more coolant openings 258 that can be located between a chamber 252 or a plurality of chambers 252a, 252b in one intermediate cladding arm 244 and a plurality of chambers 252 or a plurality of chambers 252a, 252b in an adjacent intermediate cladding arm 244. The coolant openings 258 extend through the intermediate cladding arm 244 in the thickness direction of the intermediate segment body 240 from a first side surface 204'' of the intermediate segment body 240 to a second side surface 206'' of the intermediate segment body 240.

[0035] Furthermore, similar to the inner segment body 210, the coolant opening 258 associated with the intermediate segment body 240 can take various forms (the coolant opening 258 associated with the intermediate segment body 240 may be identical to or different from the coolant opening 230 in the inner segment body 210). For example, if the web 254 of the intermediate segment body 240 is a single body, the coolant opening is one or more passages, channels, or other openings that can be formed in the web during the initial web manufacturing, for example, during the layer-by-layer deposition process of an additive manufacturing process, or after web manufacturing by a material removal process such as drilling, milling, or plunge milling, or by using an electrical discharge machining (EDM) process. In another example, if each intermediate cladding arm 244 is formed as a single body and multiple intermediate cladding arms 244 are joined to form an intermediate segment body 240, the coolant opening 258 may be a passage or other opening formed by surface features at the edge of the intermediate cladding arm 244, i.e., the surface of the intermediate cladding arm 244 forming the first side surface 204'' of the intermediate segment body 240, the surface of the intermediate cladding arm 244 forming the second side surface 206'' of the intermediate segment body 240, the surface of the second radially inner end 246 of the intermediate cladding arm 244, and the second radially outer end 250 of the intermediate cladding arm 244. In this regard, the edge of the cladding arm 244 may include grooves, ribs, or other surface features that, when in contact with the edge of an adjacent intermediate cladding arm 244, form one or more passages, channels, or other openings. In this regard, the edges of the intermediate cladding arm 244 may include any of the surface features described and / or shown herein with respect to the inner cladding arm 214 and Figure 6C. If present, in some embodiments, such surface features may be offset along the radially extending length of the intermediate cladding arm 244 so that their location does not coincide with a portion of the web 254 separating the first chamber 252a from the adjacent chamber 252b.Combinations of different coolant openings can also be implemented.

[0036] In some embodiments, it is preferable that the intermediate segment body 240 be formed as a single body to avoid welding or other constructions on the surface 260 that form the inner diameter of the opening 248, which would otherwise exist from joining individual intermediate cladding arms 244 or groups of intermediate cladding arms 244. In some embodiments, one or both of the surface 260 that forms the inner diameter of the opening 248 and the outer edge 256 of the intermediate segment body 240 may be a smooth surface (as seen on the surface 260) or a ridge having a series of peaks and valleys (as seen on the surface of the outer edge 256). The surface morphologies of the surface 260 that forms the opening 248 and the outer edge 256 may be complementary to adjacent surfaces within the assembled layer 200. However, if they are not perfectly complementary, gaps may exist that can function as coolant channels, or adapter structures may be used to fit non-conforming surfaces at the contact surface. For example, the first internal contact surface may include multiple secondary coolant channels that traverse the activated core structure from the first end to the second end. Furthermore, if the surfaces are not complementary, an adapter structure can be used to fit the incompatible surfaces at the contact surface. As a further alternative, a combination of secondary coolant channels and an adapter structure can also be implemented.

[0037] To make the involute curve shape of the intermediate cladding arm easier to see, an embodiment of the intermediate cladding arm 244 is schematically shown in Figure 7A. In the illustrated embodiment, two curved edges 262a, 262b of the involute curve shape of the intermediate cladding arm 244 are located on a line connected to the midpoint of a web 254 located between a chamber 252 or multiple chambers 252a, 252b in one intermediate cladding arm 244 and a chamber 252 or multiple chambers 252a, 252b in an adjacent intermediate cladding arm 244. The involute curve shape itself may have a constant width (i.e., the width is the distance between the two opposing curved edges 262a, 262b of the involute curve shape of the intermediate cladding arm 244) as a function of the position along the axial direction of the involute curve shape extending from the midpoint of the second radially inner end 246 to the midpoint of the second radially outer end 250. Alternatively, the width of the involute curve shape may vary as a function of the position along the axis of the involute curve shape extending from the midpoint of the second radially inner end 246 to the midpoint of the second radially outer end 250. For example, the width of the involute curve shape may continuously increase or continuously decrease as a function of the position along the axis of the involute curve shape extending from the midpoint of the second radially inner end 246 to the midpoint of the second radially outer end 250.

[0038] Figure 8A shows an embodiment of the outer segment body 270 in a top view of the outer segment body 270 and a cross-sectional plan view of the assembled fission reactor structure, in each case in a plane perpendicular to the axis of the axially extending inner opening 202. Figure 8 is an enlarged view showing a portion P3 of the outer segment body 270 shown in Figure 8A.

[0039] The outer segment body 270 includes an outer cladding arm 272 having a third involute curve shape that radiates outward in a helical manner from a third radially inner end 274 adjacent to an inner opening 276 which forms or is part of a second inner contact surface 242 in the assembled layer 200, to a third radially outer end 278 on an outer edge 280 which forms or is part of the radially outermost edge in the assembled layer 200 (or, if additional segment bodies are included in more than three as shown, which form or are part of a further contact surface in the assembled layer 200). A plurality of outer cladding arms 272 include at least one chamber 282, or a plurality of chambers 282a, 282b (see also, e.g., Figures 9 and 10). In Figure 8B, the chamber 282 is shown for only two outer cladding arms 272, but additional outer cladding arms 272, or alternatively all outer cladding arms 272, may include one or more chambers 282. The chambers 282 extend along the length of the outer cladding arm 272, or, if multiple chambers are included, the chambers 282a, 282b are distributed along the length of the outer cladding arm 272. The chambers 282 (or, if multiple chambers are included, the chambers 282a, 282b) are contained within the web 284 of the material forming the outer segment body 270, so that an individual chamber 282 is enclosed within the web 284 in each outer cladding arm 272. If further multiple chambers 282 are included, the first chamber 282a is separated from the adjacent chamber 282b by a portion of the web 284 (see also Figures 9 and 10). As described herein, the chambers 282 may contain a fissile fuel composition (or other compositions such as moderators and interfering materials), and the web 284 functions as cladding for the fissile fuel composition or other compositions.

[0040] Similar to the inner segment body 210 and the intermediate segment body 240, the outer segment body 270 may include one or more coolant openings 286 that can be located between a chamber 282 or a plurality of chambers 282a, 282b on one outer cladding arm 272 and a chamber 282 or a plurality of chambers 282a, 282b on an adjacent outer cladding arm 272. The coolant openings 286 extend through the outer cladding arm 272 in the thickness direction of the outer segment body 270 from a first side surface 204''' to a second side surface 206''' of the outer segment body 270.

[0041] Furthermore, similar to the inner segment body 210 and the intermediate segment body 240, the coolant openings 286 associated with the outer segment body 270 can be of various shapes (the coolant openings 286 associated with the outer segment body 270 may be identical or different to one or more of the coolant openings 258 in the intermediate segment body 240 and the coolant openings 230 in the inner segment body 210). For example, if the web 284 of the outer segment body 270 is a single body, the coolant openings are one or more passages, channels, or other openings that can be formed in the web during the initial web manufacturing, for example, during the layer-by-layer deposition process of an additive manufacturing process, or after web manufacturing by a material removal process such as drilling, milling, or plunge milling, or by using an electrical discharge machining (EDM) process. In another example, if each outer cladding arm 272 is formed as a single body and multiple outer cladding arms 272 are joined to form an outer segment body 270, the coolant opening 286 may be a passage or other opening formed by surface features at the edges of the outer cladding arms 272, i.e., the surface of the outer cladding arm 272 forming the first side surface 204''' of the outer segment body 270, the surface of the outer cladding arm 272 forming the second side surface 206''' of the outer segment body 270, the surface of the third radially inner end 274 of the outer cladding arm 272, and the surface of the third radially outer end 278 of the outer cladding arm 272. In this regard, the edges of the outer cladding arms 272 may include grooves, ribs, or other surface features that, when in contact with the edges of adjacent outer cladding arms 272, form one or more passages, channels, or other openings. In this regard, the edges of the intermediate cladding arm 244 may include any of the surface features described and / or shown herein with respect to the inner cladding arm 214 and Figure 6C.If present, in some embodiments, such surface features may be offset along the length of the radially extending outer cladding arm 272 so that their position does not coincide with the portion of the web 284 separating the first chamber 282a from the adjacent chamber 282b. Combinations of different coolant openings can also be implemented.

[0042] In some embodiments, one or both of the surface 288 forming the inner diameter of the opening 276 and the outer edge 280 of the outer segment body 270 may be a smooth surface (as seen on the surface 288) or a ridge with a series of peaks and valleys (as seen on the surface of the outer edge 280). The morphology of the surface 288 forming the inner diameter of the opening 276 may be complementary to the adjacent surfaces within the assembled layer 200. Also, if further segment bodies are radially outward from the outer segment body 270, the morphology of the surface of the outer edge 280 may be complementary to the adjacent surfaces within the assembled layer 200. However, if the surfaces are not perfectly complementary, gaps may exist that can function as coolant channels. For example, the second inner contact surface may include a plurality of secondary coolant channels that traverse the activated core structure from the first end to the second end. Also, if these surfaces are not perfectly complementary, an adapter structure can be used to fit the mismatched surfaces at the contact surface. As a further alternative, a combination of secondary coolant channels and an adapter structure can also be implemented.

[0043] To make the involute curve shape of the outer cladding arm easier to see, an embodiment of the outer cladding arm 244 is schematically shown in Figure 8A. In the illustrated embodiment, two curved edges 292a, 292b of the involute curve shape of the outer cladding arm 272 are located on a line connected to the midpoint of a web 284 that is located between a chamber 282 or multiple chambers 282a, 282b in one outer cladding arm 272 and a chamber 282 or multiple chambers 282a, 282b in an adjacent intermediate cladding arm 272. The involute curve shape itself may have a constant width (i.e., the width is the distance between the two opposing curved edges 292a, 292b of the involute curve shape of the outer cladding arm 244) as a function of the position along the axis of the involute curve shape extending from the midpoint of the third radially inner end 274 to the midpoint of the third radially outer end 278. Alternatively, the width of the involute curve shape may vary as a function of the position along the axis of the involute curve shape extending from the midpoint of the third radially inner end 274 to the midpoint of the third radially outer end 278. For example, the width of the involute curve shape may continuously increase or continuously decrease as a function of the position along the axis of the involute curve shape extending from the midpoint of the third radially inner end 274 to the midpoint of the third radially outer end 278.

[0044] In some embodiments, when considered collectively, the first involute curve shape, the second involute curve shape, and the third involute curve shape share a common involute curve shape. Thus, the surfaces of the inner cladding arm, the intermediate cladding arm, and the outer cladding arm form a continuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body. For example, as shown in Figure 9, if the surfaces of the curved edges 232a and 232b of the first involute curve shape of the inner cladding arm protrude across the first inner contact surface 212, the protrusion coincides with the surfaces of the curved edges 262a and 262b of the second involute curve shape of the intermediate cladding arm. As a result, there exists a continuous involute curve shape that includes the surfaces of the curved edges 232a and 232b of the first involute curve shape of the inner cladding arm and the surfaces of the curved edges 262a and 262b of the second involute curve shape of the intermediate cladding arm. As a further example, if the above-mentioned continuous involute curve shape further protrudes across the second internal contact surface 242, the protrusion also coincides with the surfaces of the curved edges 292a and 292b of the third involute curve shape of the outer cladding arm. As a result of this further protrusion, there exists a continuous involute curve shape that includes the surfaces of the curved edges 232a and 232b of the first involute curve shape of the inner cladding arm, the surfaces of the curved edges 262a and 262b of the second involute curve shape of the intermediate cladding arm, and the surfaces of the curved edges 292a and 292b of the third involute curve shape of the outer cladding arm. Furthermore, as shown in Figure 9, the first involute curve shape, the second involute curve shape, and the third involute curve shape each correspond to different portions of a continuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body.

[0045] In other embodiments, the surfaces of the curved edges 232a and 232b of the first involute curve shape of the inner cladding arm, the surfaces of the curved edges 262a and 262b of the second involute curve shape of the intermediate cladding arm, and the surfaces of the curved edges 292a and 292b of the third involute curve shape of the outer cladding arm correspond to the curvature of a continuous involute curve shape, but one or more segment bodies are rotated relative to adjacent segment bodies. If the rotation is smaller than a quantized value that maintains the alignment of the surfaces, the rotation causes the surfaces of the curved edges to be offset in the rotational direction from the projections of the continuous involute curve shape. In such an arrangement, the surfaces of the curved edges of the involute curve shape of the cladding arm on each side of the relevant affected contact surface are discontinuous in that they are connected by a step change.

[0046] In further embodiments, when considered collectively, the first involute curve shape, the second involute curve shape, and the third involute curve shape have different curvatures. Thus, the surfaces of the inner cladding arm, the intermediate cladding arm, and the outer cladding arm form a discontinuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body. Such embodiments are illustrated in layer 200 shown in Figure 5.

[0047] In some embodiments, some or all of the surfaces of the inner cladding arm, the intermediate cladding arm, and the outer cladding arm form a discontinuous involute curve shape, but such surfaces still collectively spiral radially in the same direction, i.e., either clockwise (as shown in Figure 5) or counterclockwise.

[0048] In further embodiments, one or more (but not all) of the first, second, and third involute curve shapes share a common involute curve shape. Thus, some of the surfaces of the inner cladding arm, the intermediate cladding arm, and the outer cladding arm form a continuous involute curve shape extending across each surface. On the other hand, other portions of the surfaces of the inner cladding arm, the intermediate cladding arm, and the outer cladding arm form discontinuous involute curve shapes extending across each surface.

[0049] In the embodiments shown and described in Figures 6A-6B, 7A-7B, and 8A-8B, each of the multiple inner cladding arms, multiple intermediate cladding arms, and multiple outer cladding arms may individually include one or more chambers. In some embodiments, the inner cladding arms have more chambers than either the intermediate cladding arms or the outer cladding arms. For example, as shown in Figure 5, each inner cladding arm of the inner segment body 210 may include six chambers 222 (see also chamber 222 in Figure 6A), and each of the intermediate cladding arms and the multiple outer cladding arms includes one chamber (252 and 282, respectively) (see also chamber 252 in Figure 7B and chamber 282 in Figure 8B). As another example, as shown in Figure 10, each inner cladding arm may contain six chambers 222 (see also chamber 222 in Figure 6A), and the intermediate cladding arm and multiple outer cladding arms may contain two chambers each (252 and 282, respectively). In the exemplary embodiment, the total number of chambers in one inner cladding arm, one intermediate cladding arm, and one outer cladding arm is 10 or less.

[0050] Figure 10 also shows alternative embodiments of the intermediate segment body 240 and the outer segment body 270. In the alternative embodiments, the multiple cladding arms are manufactured as units, such as unit 300 containing multiple intermediate cladding arms and unit 310 containing multiple outer cladding arms. Manufacturing the cladding arms as units is advantageous when using an additive manufacturing process. Furthermore, when manufactured as units, the units can use less material to form the web (at least in part, because adjacent cladding arms can use less web material between any chambers contained in these adjacent cladding arms compared to separate cladding arms located adjacent to each other), and the number of welded joints required to assemble the complete segment body can be minimized.

[0051] As mentioned above, in various examples of cladding arms, individual chambers are surrounded by a web. Typically, during manufacturing, the web forms the sides and bottom of the chamber, while one side of the chamber, such as the top, is initially open to be loaded with fissile fuel composition (or other compositions such as moderators and interfering materials). After loading, the open side of the chamber is closed by a cap attached to the web.

[0052] Figure 11 is a schematic diagram illustrating an example of a cladding arm 400. In the exemplary cladding arm 400, several features discussed herein are shown. For example, the exemplary cladding arm 400 has multiple chambers (in the illustrated embodiment, three chambers 402a, 402b, and 402c). A fuel composition 404 is also shown. The fuel composition 404 is shown at different points in the loading process. In one example, the fuel composition 404 is a pre-formed body 406 having dimensions suitable for insertion into the chamber. Suitable dimensions include the body 406 being sized so that there is thermal transfer contact between the outer surface of the body 406 of the fuel composition 404 and the inner surface of the chamber 402. Alternatively, the body 406 has a minimum standoff distance between the outer surface of the body 406 of the fuel composition 404 and the inner surface of the chamber 402, and a heat transfer material such as a salt or metal that melts at the operating temperature is also loaded into the chamber 402. Furthermore, the volume of the body 406 is sufficiently smaller than the volume of the chamber 402 to accommodate by-products of the fission reaction and heating operation, including not only the volume for containing fission gas and the volume change due to the fission reaction, but also any volume change due to thermal expansion. As seen in relation to chamber 402b, the body 406 of the fuel composition is inserted into the chamber, and as seen in relation to chamber 402c, the cap 408 closes the chamber, for example, by welding the cap to the portion of the web that forms the periphery of the chamber opening. When closed by the cap 408, the chamber is isolated from the environment, and the fuel composition 404 is surrounded by the web of the cladding arm 400 (or, if the cap is not considered part of the web after closing the chamber, surrounded by the combination of the web of the cladding arm 400 and the cap).

[0053] Another exemplary feature shown in the embodiment of the cladding arm 400 is a surface feature 420 of one edge 422 of the cladding arm 400. As previously stated, either or both of edges 422, 424 are bounded by the surface 426 of the cladding arm 400 that forms / will form the first side of the segment body, the surface 428 of the cladding arm 400 that forms / will form the second side of the segment body, the surface 430 of the radially inner end of the cladding arm 400, and the surface 432 of the radially outer end of the cladding arm 400. In the example illustrated in Figure 11, the surface feature 420 is a rib extending over the surface of edge 422. As can be easily seen from Figure 11, when edge 422 contacts the edge of an adjacent cladding arm, the surface feature 420 offsets a portion of edge 422 from the edge of the adjacent cladding arm by a distance corresponding to the distance the surface feature 420 extends over the surface of edge 422. This creates a channel that extends from the surface 426 of the cladding arm 400 that forms / will form the first side of the segment body to the surface 428 of the cladding arm 400 that forms / will form the second side of the segment body.

[0054] Figure 12 shows a layer 500 including an inner body segment 502, an intermediate segment body 504, and an outer segment body 506. Each body segment has multiple chambers. On each segment body are arranged multiple fuel composition bodies 508 corresponding to their shape (including involute curve shape) and the number of chambers present in each segment body into which the fuel composition bodies are loaded. For example, fuel composition body 508a is loaded in the radially inner chamber 510a of the inner segment body 502, fuel composition body 508g is loaded in the radially inner chamber 510g of the intermediate segment body 504, and fuel composition body 508j is loaded in the radially outer chamber 510j of the outer segment body 506. Furthermore, in some embodiments, the fuel composition within each fuel composition body varies, resulting in chambers containing different fissile fuel compositions at different locations along the cladding arm.

[0055] While fuel compositions are illustrated and explained in Figures 11 and 12, in one or more examples where the fuel composition is loaded into the chamber, it can be substituted with a moderator composition or an interfering material composition, or a mixture of moderator compositions or interfering material compositions. Such substitutions can be carried out in accordance with the reactor's neutron engineering design and thermal management design.

[0056] Figures 13A and 13B show the results of a thermal analysis study relating to the involute curved cladding arm design disclosed herein. The thermal analysis was performed on a fission reactor including such an involute curved cladding arm design. The involute curved cladding arm design in Figure 13A shows a cladding arm 600 having a first set of six fuel composition bodies 602 (corresponding to an embodiment of the cladding arm for the inner segment body), a cladding arm 604 having a second set of four fuel composition bodies 606 (corresponding to an embodiment of the cladding arm for the intermediate segment body), and a cladding arm 608 having a third set of four fuel composition bodies 610 (corresponding to an embodiment of the cladding arm for the outer segment body). Overall, the thermal analysis showed that both sides of the cladding arm for each segment body were sufficiently cooled, preventing the fuel composition in the chamber from melting.

[0057] In the cladding arm and fuel composition shown in Figure 13A, the thermal analysis shows temperatures ranging from approximately 1256.3K (for cladding at concave 620 and tip 622) to a maximum of 2504.6K for the highest temperature rise, occurring in the region of the cladding arm of the inner segment body positioned toward the radially outer end (corresponding to section P4 in Figure 13A, and shown as regions 630a and 530b in the enlarged view of Figure 13B). Region 630a relates to the fuel composition body of chamber 602e and occurs at the curved edge of the cladding arm of the inner segment body at temperatures between 2227.2K and 2504.6K. This result was interpreted as the fuel composition body expanding during operation within chamber 602e, causing an increase in the curvature of the fuel composition body, resulting in the fuel composition body no longer making contact with the inner surface of chamber 602e in region 630a. This gap formed between the fuel composition body and the inner surface of chamber 602e reduced heat transfer and increased temperature. It should be noted that this test did not include any heat transfer material such as salt or liquid metal buffer. The presence of a heat transfer material would be expected to fill the gap, improve heat transfer, and lower the temperature of region 620. However, the portion of the web 622, which was collocated in region 620, maintained a much lower temperature between 2356.3K and 1395K.

[0058] The involute curved cladding arms, segment bodies, and layers disclosed herein can be manufactured by any suitable process. Figures 14A–14D are flowcharts illustrating exemplary steps in the assembly of layers from various parts of the segment body (Figures 14A–14B, loading of fuel composition and / or moderator composition with interfering material into layers (Figure 14C)) and the assembly of multiple layers into a fission reactor structure (Figure 14D).

[0059] In the first manufacturing process, the involute-curved cladding arm 700 includes multiple chambers, and the web of the involute-curved cladding arm defines the cladding structure to be manufactured by a metallurgical process. These metallurgical processes include, in one example, an additive manufacturing process. The structure of the inner segment body 702 is preferably formed as a single structure (as shown in Figure 14A) to minimize the joining of the inner diameter surfaces of the opening. Furthermore, using a suitable additive manufacturing process, the entire structure of the layer 720, including the features of the inner segment body 702, the intermediate segment body 704, and the outer segment 706 structure of the inner segment body 702, can be formed as a single structure.

[0060] In other embodiments, the involute-curved cladding arms forming the intermediate segment body 704 and the involute-curved cladding arms forming the outer segment body 706 may be manufactured separately and joined to the layer, or they may be formed as a single body forming a unit joined to layer 720 (see Figure 14B), as shown in Figure 14A.

[0061] Other structures of the involute-curve-shaped cladding arm, such as the chamber and coolant opening, are typically manufactured at this stage of the process. The chamber in each involute-curve-shaped cladding arm is initially manufactured (either by the additive manufacturing process or by machining the material for the involute-curve-shaped cladding arm) at the point where the opening remains defined within the chamber, i.e., a cavity with side walls and one closed end.

[0062] The formation of layer 720 (Figure 14B) by joining involute curved cladding arms can be carried out by any suitable means, including welding and joining.

[0063] After layer 720 is formed, the chamber is loaded with fissile fuel composition 742 (or other materials such as moderators or interfering materials) (see Figure 14C, where the loading process is indicated by arrows). If necessary, heat transfer material is also placed inside the chamber. Once the chamber is loaded, a cap is placed at the opening and sealed, for example, by welding or hot isostatic pressing (HIP) to form an assembled involute curved cladding arm.

[0064] Next, as shown in Figure 14D, the multiple assembled layers 740 are further assembled into a fission reactor structure 780. The layers are placed one layer at a time on corresponding internal structures such as coolant openings. As previously mentioned, clocking techniques using protruding registry features can be used for alignment purposes. In the exemplary structure, up to 10 layers 740 are assembled to form the fission reactor structure 780. The layers 740 are assembled by any suitable means, such as welding or bonding. Furthermore, a plate 782 can be placed at any end of the fission reactor structure 780. The plate may have suitable openings, for example, corresponding to coolant openings, internal openings, and / or light-load openings. The assembled fission reactor structure 780 is placed within a radial reflector 784. The radial reflector is arbitrary, based on the fuel material and core design.

[0065] In some manufacturing methods or steps of a manufacturing method, portions of the cladding arm, segment bodies, and / or layers with an involute curve shape are manufactured as a single, integrated structure using, for example, an additive manufacturing process. As used herein, additive manufacturing processes include any techniques for constructing a 3D object by stacking materials layer by layer. In an example of a suitable additive manufacturing process, 3D printing of a metal alloy such as a molybdenum-containing metal alloy, Zircaloy-4, or Hastelloy-X is utilized to form the aforementioned structural features. In other embodiments, if a suitable multi-material additive manufacturing process is employed that has multiple metals in the raw materials, fissile nuclear fuel composition and / or heat transfer material and / or moderator and / or interfering material may be included within a single, integrated structure. If molten metal is not included in the additive manufacturing process, the additive manufacturing process can be paused to place the volume of molten metal into the fuel cavity (either in liquid or solid form), and the additive manufacturing process can be continued to complete the structure of the closed chamber. When a suitable multi-material additive manufacturing process with multiple metals in the raw materials is employed, other alloys that can be used include alloy steel, zirconium alloy, and molybdenum tungsten alloy (for the core shell), beryllium alloy (for the reflector), and stainless steel (for the containment vessel). Even when not manufactured by an additive manufacturing process, the above-mentioned materials can be used in the manufacture of the various structures disclosed herein.

[0066] Additive manufacturing technology for the production of a single, integrated structure may include additional steps such as (a) predictive and causal analysis, (b) in-situ monitoring combined with machine vision and accelerated processes during layer-by-layer manufacturing of the structure, (c) automated analysis combined with machine learning components, and (d) virtual inspection of a digital representation of the finished structure. Furthermore, additive manufacturing technology can form complex shapes. When combined with in-situ sensors, machine vision images, and artificial intelligence, additive manufacturing technology allows for control over manufacturing quality because components are built layer by layer (often on a 50-micron scale), providing predictive quality assurance for the production of such reactors and structures.

[0067] As used herein, cladding is a feature-enhanced fuel exterior located between the coolant and the nuclear fuel. Cladding acts as a safety barrier to prevent radioactive fission fragments from leaking into and contaminating the coolant. Some design constraints on cladding include neutron absorption, radiation resistance, and temperature behavior. Cladding is typically formed from corrosion-resistant materials with a small thermal neutron absorption cross-section. Exemplary materials include Zircaloy or steel, but other materials, such as metallic and ceramic (Be, C, Mg, Zr, O, and Si), may be used if suitable for the reactor conditions. In some embodiments, cladding materials can be isotope-enriched to increase reactivity through the reduction of isotopes with high neutron absorption cross-sections. For example, molybdenum-enriched Mo-92 has a smaller parasitic neutron absorption cross-section than elemental molybdenum.

[0068] Applicable to the disclosed fission reactor, suitable fission fuel compositions to be included in the thermal source include uranium oxide enriched to less than 20%, uranium containing 10 wt% molybdenum (U-10Mo), uranium nitride (UN), and other stable fissile fuel compositions. Flammable interfering materials may also be included. Typically, fissile fuel compositions are in the form of ceramic materials.

[0069] The molten metals suitable for inclusion in the fuel cavity of the disclosed fission reactor are: These are sodium (Na), sodium potassium (NaK), potassium (K), and iron (Fe).

[0070] Various support and auxiliary devices are intended to be incorporated into the disclosed fission reactor. For example, at least one of moderators (such as zirconium hydride (ZrH), beryllium oxide (BeO), water, and graphite), control rods (such as iridium control rods), and scientific instruments (such as temperature sensors or radiation detectors), and an isotope generator can be incorporated into the fission reactor. Furthermore, the control rods can also contain neutron poisons that absorb neutrons and can be used to adjust the criticality of the reactor. The neutron poison can absorb enough neutrons to shut down the fission reactor (e.g., if the control rods are fully inserted into the reactor space), or it can be positioned axially to maintain the criticality of the fission reactor (e.g., if the control rods are drawn out from the core only a distance that allows the fission chain reaction to continue). Any appropriate number of control rods and moderators can be used and appropriately distributed throughout the reactor space to obtain one or more desired flux profiles, power distributions, and operating profiles. In exemplary embodiments, the control rods are threaded, contributing to saving axial space, maximizing the diameter of the control rods, and allowing direct contact with the roller nut for reliable SCRAM operation. All or some of the control rods can be individually controlled by separate motors to provide individually responsive control and / or power shaping.

[0071] FIG. 15 is a side cross-sectional view schematically showing an embodiment of a nuclear fission reactor 800 including a plurality of layers 802 assembled in a nuclear fission reactor structure 804 and arranged along the longitudinal axis 806 of the nuclear fission reactor structure 804. As previously disclosed and as described in embodiments herein, layer 802 is defined by an inner segment body, an intermediate segment body, an outer segment body, a first internal contact surface, and a second internal contact surface. The nuclear fission reactor 800 also includes a radial reflector 810 disposed around the outer surface of the nuclear fission reactor structure 804. The nuclear fission reactor structure 804 may be of any suitable geometry as long as it exhibits appropriate neutron engineering and thermal management characteristics. As described herein, the ratio of the length (L RX ) of the active core region to the diameter (D RX ) of the active core structure is about 1 (i.e., L RX / D RX = 1 ± 0.05), and exemplary embodiments have sufficient layers 802. Generally, the radial reflector 810 reduces neutron leakage from the nuclear fission reactor 800 by scattering (or reflecting) neutrons that would otherwise escape back into the core. This increases the design effective multiplication factor (k eff ) and reduces the amount of fuel required to maintain criticality. The pressure vessel 820 surrounds, among other things, the nuclear fission reactor structure 804 and has an opening 822 through which the active core structure can be in fluid communication with a coolant system (not shown) (the flow of coolant is indicated by arrow 824). Some of the various auxiliary devices associated with the nuclear fission reactor are also shown in FIG. 15 and include a control rod assembly 830 and a shutdown device such as a poison rod 832 axially movable within an inner opening of the nuclear fission reactor structure 804. As previously disclosed and as described in embodiments herein, any suitable radial reflector, pressure vessel, and coolant system can be incorporated into the nuclear fission reactor 800.

[0072] The disclosed configurations relate to any configuration in which a heat generation source containing a fissile nuclear fuel composition, whether the fuel elements or the fissile nuclear fuel composition itself, is surrounded by cladding. While generally described herein in relation to pressurized water reactors (PWR reactors) and water as the primary coolant, the structures and methods disclosed herein can also be applied to other reactor systems. This includes boiling water reactors (BWR reactors), deuterium oxide (heavy water) moderator reactors such as CANDU reactors, light water reactors (LWR reactors), pebble-bed reactors (PBR reactors), nuclear thermal propulsion reactors (NTP reactors), both commercial and research reactors, and utilizing other primary coolants such as helium, hydrogen, methane, molten metal, and liquid metal. When utilizing the molten metal fuel buffer technology disclosed herein, any fuel cladding configuration in these various reactors can produce superior core safety and performance characteristics.

[0073] The fission reactors disclosed herein can be used in suitable applications including, but not limited to, terrestrial power, remote power or off-grid applications, space power, space propulsion, isotope production, directed energy applications, commercial power applications, and desalination.

[0074] While specific embodiments have been referenced, it will be apparent that other embodiments and variations may be devised by others skilled in the art without departing from the spirit and scope thereof. The appended claims are intended to be construed to include all such embodiments and equivalent variations.

Claims

1. A nuclear fission reactor structure comprising multiple layers, Each of the aforementioned layers is An inner segment body including an inner opening that extends axially from the first side surface of the inner segment body to the second side surface of the inner segment body, The intermediate segment body located radially outward from the inner segment body, The outer segment body located radially outward from the intermediate segment body, A first internal contact surface that separates the inner segment body and the intermediate segment body, A second internal contact surface that separates the intermediate segment body and the outer segment body, Includes, In a plan cross-sectional view in a plane perpendicular to the inner opening extending in the axial direction, The inner segment body includes a plurality of inner cladding arms having a first involute curve shape that radiates outward in a helical manner from a first radially inner end adjacent to the inner opening to a first radially outer end of the first inner contact surface, The intermediate segment body includes a plurality of intermediate cladding arms having a second involute curve shape that radiates outward in a helical manner from a second radially inner end adjacent to the first internal contact surface to a second radially outer end of the second internal contact surface. The outer segment body includes a plurality of outer cladding arms having a third involute curve shape that radiates outward in a helical manner from a third radially inner end adjacent to the second inner contact surface to a third radially outer end of the radially outer surface of the outer segment body, Here, the first involute curve shape, the second involute curve shape, and the third involute curve shape form a continuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body. The first involute curve shape, the second involute curve shape, and the third involute curve shape each have different curvatures. Multiple inner cladding arms, multiple intermediate cladding arms, and multiple outer cladding arms include multiple chambers, The chambers located at different positions along the cladding arm contain different fissile fuel compositions. The chambers located at different positions along the cladding arm contain different reduction gears, The inner cladding arm has opposing sides extending from the first side of the inner segment body to the second side of the inner segment body, At least one projection protrudes outward from at least one of the opposing sides, Nuclear fission reactor structure.

2. A nuclear fission reactor structure comprising multiple layers, Each of the aforementioned layers is An inner segment body including an inner opening that extends axially from the first side surface of the inner segment body to the second side surface of the inner segment body, The intermediate segment body located radially outward from the inner segment body, The outer segment body located radially outward from the intermediate segment body, A first internal contact surface that separates the inner segment body and the intermediate segment body, A second internal contact surface that separates the intermediate segment body and the outer segment body, Includes, In a plan cross-sectional view in a plane perpendicular to the inner opening extending in the axial direction, The inner segment body includes a plurality of inner cladding arms having a first involute curve shape that radiates outward in a helical manner from a first radially inner end adjacent to the inner opening to a first radially outer end of the first inner contact surface, The intermediate segment body includes a plurality of intermediate cladding arms having a second involute curve shape that radiates outward in a helical manner from a second radially inner end adjacent to the first internal contact surface to a second radially outer end of the second internal contact surface. The outer segment body includes a plurality of outer cladding arms having a third involute curve shape that radiates outward in a helical manner from a third radially inner end adjacent to the second inner contact surface to the third radially outer end of the radially outer surface of the outer segment body. Nuclear fission reactor structure.

3. The first involute curve shape, the second involute curve shape, and the third involute curve shape form a continuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body. The nuclear fission reactor structure according to claim 2.

4. The continuous involute curve-shaped surface projections extend across the first internal contact surface and the second internal contact surface and coincide with each of the surfaces of the plurality of inner cladding arms, the surface of the plurality of intermediate cladding arms, and the surface of the plurality of outer cladding arms. The nuclear fission reactor structure according to claim 3.

5. Each of the first involute curve shape, the second involute curve shape, and the third involute curve shape corresponds to a different portion of a continuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body. The nuclear fission reactor structure according to claim 2.

6. The continuous involute curve-shaped surface projections extend across the first internal contact surface and the second internal contact surface and coincide with each of the surfaces of the plurality of inner cladding arms, the surface of the plurality of intermediate cladding arms, and the surface of the plurality of outer cladding arms. The nuclear fission reactor structure according to claim 5.

7. Each of the first involute curve shape, the second involute curve shape, and the third involute curve shape has a different curvature. A nuclear fission reactor structure according to any one of claims 1 to 6.

8. The continuous involute curve-shaped surface projections extend across the first internal contact surface and the second internal contact surface and coincide with each of the surfaces of the plurality of inner cladding arms, the surface of the plurality of intermediate cladding arms, and the surface of the plurality of outer cladding arms. A nuclear fission reactor structure according to any one of claims 1 to 7.

9. Each of the plurality of inner cladding arms, the plurality of intermediate cladding arms, and the plurality of outer cladding arms includes a plurality of chambers, A nuclear fission reactor structure according to any one of claims 1 to 8.

10. The chambers of each of the cladding arms are separated from each other by a web. The nuclear fission reactor structure according to claim 9.

11. Each of the aforementioned inner cladding arms has more chambers than each of the aforementioned outer cladding arms. The nuclear fission reactor structure according to claim 9 or 10.

12. The aforementioned number of chambers is 10 or less. A nuclear fission reactor structure according to any one of claims 9 to 11.

13. Each of the aforementioned intermediate cladding arms has the same number of chambers as each of the aforementioned outer cladding arms. A nuclear fission reactor structure according to any one of claims 9 to 12.

14. The chamber contains one of a fissile fuel composition and a moderator. A nuclear fission reactor structure according to any one of claims 9 to 13.

15. The chambers located at different positions along the cladding arm contain different fissile fuel compositions. The nuclear fission reactor structure according to claim 14.

16. The chambers located at different positions along the cladding arm contain different reduction gears. The nuclear fission reactor structure according to claim 14 or 15.

17. When the fissile fuel composition is located inside the chamber, a gap exists between at least a portion of one inner surface of the chamber and at least a portion of one outer surface of the body forming the fissile fuel composition. The nuclear fission reactor structure according to claim 14.

18. The inner cladding arm has opposing sides extending from the first side of the inner segment body to the second side of the inner segment body, At least one projection protrudes outward from at least one opposing side, A nuclear fission reactor structure according to any one of claims 1 to 17.

19. Each projection extends continuously along at least one opposing side surface from a first end toward the first side surface of the inner segment body to a second end toward the second side surface of the inner segment body. The nuclear fission reactor structure according to claim 18.

20. Each projection extends discontinuously along at least one opposing side surface from a first end toward the first side surface of the inner segment body to a second end toward the second side surface of the inner segment body. The nuclear fission reactor structure according to claim 18.

21. The projection has an upper surface distal to at least one opposing side from which the projection protrudes, When the first inner cladding arm is assembled to the inner segment body with the second inner cladding arm immediately adjacent to it, the upper surface of the projection on the first inner cladding arm contacts the opposing side surface of the second inner cladding arm, forming a channel between the first inner cladding arm and the second inner cladding arm. A nuclear fission reactor structure according to any one of claims 18 to 20.

22. The inner segment body, the intermediate segment body, the outer segment body, the first internal contact surface, and the second internal contact surface define layers. A nuclear fission reactor structure according to any one of claims 1 to 21.

23. A plurality of layers according to claim 2, assembled into a nuclear fission reactor structure having a first end face, a second end face, and an outer surface connecting the first end face and the second end face, A radial reflector arranged around the outer side surface of the nuclear fission reactor structure, Containment vessel and A coolant system that fluidly communicates with the nuclear fission reactor structure through the opening of the containment vessel, Equipped with, Nuclear fission reactor.

24. The nuclear fission reactor structure has a cylindrical structure. A nuclear fission reactor according to claim 23.

25. The cooling system is either liquid-based or gas-based. A nuclear fission reactor according to claim 23 or 24.

26. The first internal contact surface and the second internal contact surface in each of the plurality of layers include a plurality of secondary coolant channels that traverse the activated core structure from the first end to the second end. A nuclear fission reactor according to any one of claims 23 to 25.

27. Multiple first layers are assembled into the nuclear fission reactor structure by welding. A nuclear fission reactor according to any one of claims 23 to 26.

28. Multiple first layers are assembled into the nuclear fission reactor structure by adhesion. A nuclear fission reactor according to any one of claims 23 to 26.

29. A method for manufacturing a nuclear fission reactor structure according to claim 2, A step of manufacturing the inner segment body, the segments of the intermediate segment body, and the segments of the outer segment body, wherein each of the plurality of inner cladding arms, the plurality of intermediate cladding arms, and the plurality of outer cladding arms includes a plurality of chambers, A step of assembling the inner segment body, the segments of the intermediate segment body, and the segments of the outer segment body in layers, wherein the segment body is assembled by welding and bonding. The steps include: forming a fuel loading layer by placing one of a fissile fuel composition and a moderator in the plurality of chambers; The steps include assembling a plurality of fuel loading layers into the nuclear fission reactor structure, including, method.

30. The inner segment body, the segments of the intermediate segment body, and the segments of the outer segment body are manufactured using an additive manufacturing process. The method according to claim 29.

31. A method for manufacturing a nuclear fission reactor structure according to claim 2, A step of manufacturing a layer comprising the inner segment body, the intermediate segment body, and the outer segment body as a single structure, wherein each of the plurality of inner cladding arms, the plurality of intermediate cladding arms, and the plurality of outer cladding arms includes a plurality of chambers, The steps include: forming a fuel loading layer by placing one of a fissile fuel composition and a moderator in the plurality of chambers; The steps include assembling a plurality of fuel loading layers into the nuclear fission reactor structure, including, method.

32. The single structure comprising the inner segment body, the intermediate segment body, and the outer segment body is manufactured using an additive manufacturing process. The method according to claim 31.

33. The steps include arranging the nuclear fission reactor structure inside a radial reflector, The method according to claims 29, 30, 31, and 32.

34. The nuclear fission reactor structure has a cylindrical shape. The method according to claims 29, 30, 31, 32, and 33.

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