Nuclear reactor fuel and related systems and methods

Abstract

Embodiments of nuclear fuel elements for use in various types of nuclear reactors are disclosed. One embodiment of a nuclear fuel element comprises a plurality of solid nuclear fuel particles, such as triple-layered isotropic (TRISO) fuel particles, mixed in a non-solid matrix that is substantially stagnant to the plurality of solid nuclear fuel particles. The non-solid matrix may include liquid metals, liquid metal alloys, and liquid salts. Various embodiments of the non-solid matrix include tin, lead, sodium, aluminum, bismuth, and alloys thereof. Methods for producing nuclear fuel and embodiments of nuclear fuel cores containing nuclear fuel elements are also disclosed.

Description

[Technical Field]

[0001] Reference to related applications If an application data sheet (ADS) or PCT application ("Application") was filed on the filing date of this application, it is incorporated herein by reference. Any application asserted with respect to an ADS or priority claim under Section 119, 112, 120, 121, or 365(c) of the U.S. Patent Act, and any parent, grandparent, great-grandparent applications of such applications, are also incorporated herein by reference, to the extent that such subject matter does not conflict with this Specified, including any priority claims made in such applications and any material incorporated by reference.

[0002] Furthermore, this application relates to the following U.S. Patent Application, which is incorporated in its entirety herein by reference, and as fully described herein, U.S. Provisional Patent Application No. 63 / 510,362 (Reference No. LPF-1001P), filed on 26 June 2023, titled "Nuclear Reactor Fuel and Associated Systems and Methods," describing a nuclear fuel core and associated methods for use in a nuclear fission reactor.

[0003] Embodiments of the present invention are in the field of nuclear technology. More specifically, certain embodiments of the present invention relate to nuclear fuel for use in various types of nuclear reactors. [Background technology]

[0004] The background description of this invention is provided to aid in understanding the invention and its uses and applications, and does not constitute prior art.

[0005] Breeder fission reactors do not simply burn a small portion of uranium, but convert (breed) uranium into plutonium, enabling a much higher "fuel utilization rate" (total energy extracted per initial uranium atom) than conventional fission reactors. This makes large fission reactors highly economical, significantly reduces waste, and allows the Earth's natural uranium and thorium resources to sustain a much longer-lasting "clean air" energy source for hundreds of years.

[0006] However, existing fuel types for these types of reactors are subject to many limitations. Therefore, developing improved nuclear fuels for use in reactors, including but not limited to breeder burner reactors, would represent a significant advance in cutting-edge technology.

[0007] This invention was developed in response to this background technology. [Overview of the project]

[0008] This "Outline of the Invention" of the present invention provides a broad overview of the invention, its uses, and applications, and is not intended to limit the scope of the invention, which will become clear from the "Modes for Carrying Out the Invention" when read in conjunction with the drawings.

[0009] Developing nuclear fuel for use in various types of reactors would represent a significant advance in cutting-edge technology. Therefore, embodiments of nuclear fuel elements for use in various types of reactors are disclosed.

[0010] According to a first embodiment, or in one embodiment, a nuclear fuel element is provided. The nuclear fuel element may comprise a plurality of solid nuclear fuel particles. Each of the plurality of solid nuclear fuel particles may comprise nuclear material. The nuclear fuel element may comprise a non-solid matrix. The plurality of solid nuclear fuel particles may be mixed in the non-solid matrix. The non-solid matrix may be substantially stagnant relative to the plurality of nuclear fuel particles. The non-solid matrix may comprise a substance selected from the group consisting of liquid metals, liquid metal alloys, and liquid salts.

[0011] In some embodiments, the multiple solid nuclear fuel particles include three-layered isotropic (TRISO) particles.

[0012] In some embodiments, the non-solid matrix is ​​selected from the group consisting of liquid metals and liquid metal alloys.

[0013] In some embodiments, the non-solid matrix is ​​selected from the group consisting of tin, lead, sodium, aluminum, bismuth, zinc, magnesium, calcium, cerium, rubidium, zirconium, beryllium, potassium, yttrium, strontium, barium, and alloys thereof.

[0014] In some embodiments, the non-solid matrix includes a metalloid. In some embodiments, the non-solid matrix further includes elements selected from the group consisting of silicon and germanium.

[0015] In some embodiments, the non-solid matrix is ​​selected from the group consisting of tin, tin-aluminum alloy, tin-aluminum-gallium alloy, tin-zinc-aluminum alloy, tin-magnesium alloy, tin-aluminum-magnesium alloy, and tin-magnesium-zinc alloy.

[0016] In some embodiments, the percent composition of tin in the non-solid matrix is greater than 80 percent by mass fraction. In some embodiments, the percent composition of tin in the non-solid matrix is greater than 90 percent by mass fraction.

[0017] In some embodiments, the non-solid matrix is selected from the group consisting of lead, lead-bismuth-tin alloy, and lead-magnesium alloy.

[0018] In some embodiments, the non-solid matrix is selected from the group consisting of sodium-lead alloy, sodium-lead-bismuth alloy, and sodium-bismuth alloy.

[0019] In some embodiments, the non-solid matrix is selected from the group consisting of lead-bismuth alloy and lead-bismuth eutectic.

[0020] In some embodiments, the non-solid matrix is liquid sodium.

[0021] In some embodiments, the non-solid matrix is liquid gallium.

[0022] In some embodiments, the non-solid matrix includes an alloy selected from the group consisting of an alloy of tin, aluminum, and gallium; an alloy of tin, aluminum, lead, and bismuth; an alloy of lead and magnesium; an alloy of aluminum and magnesium; an alloy of magnesium and zinc; an alloy of bismuth and sodium; and an alloy of lead and sodium.

[0023] In some embodiments, the non-solid matrix includes an alloy selected from the group consisting of an alloy of lead and lithium; an alloy of tin and lithium; and an alloy of lead, bismuth, and lithium.

[0024] In some embodiments, the non-solid matrix includes a liquid salt.

[0025] In other embodiments, the non-solid matrix further comprises a substance selected from the group consisting of water, sulfur, supercritical fluids, organic liquids, and inorganic liquids.

[0026] In some embodiments, the plurality of solid nuclear fuel particles includes tri-isotropic (TRISO) particles. The non-solid matrix may be selected from the group consisting of tin-aluminum alloys, tin-aluminum-gallium alloys, lead-bismuth alloys, and lead.

[0027] In some embodiments, the plurality of solid nuclear fuel particles includes particles selected from the group consisting of tri-isotropic (TRISO) particles, bi-isotropic particles, and quadri-isotropic particles.

[0028] In some embodiments, at least one of the plurality of solid nuclear fuel particles comprises one or more substances selected from the group consisting of ceramic materials, metallic materials, carbon materials, and cermet materials.

[0029] In some embodiments, at least one of the plurality of solid nuclear fuel particles comprises an actinide fuel kernel.

[0030] In some embodiments, at least one of the plurality of solid nuclear fuel particles comprises a fuel kernel selected from the group consisting of UN kernels, UO2 kernels, UC kernels, and UCO kernels.

[0031] In some embodiments, the nuclear material is selected from the group consisting of fissile materials, conversion materials, and parent materials.

[0032] In some embodiments, the plurality of solid nuclear fuel particles comprises a fissile material selected from the group consisting of uranium, thorium, and plutonium.

[0033] In other embodiments, the plurality of solid nuclear fuel particles comprises a conversion or parent material selected from the group consisting of thulium, tantalum, gadolinium, silver, strontium, holmium, and lithium.

[0034] In some embodiments, each of the multiple solid nuclear fuel particles is 0.5 cm 3 Smaller, 6 x 10 -7 cm 3 It has a larger volume.

[0035] In some embodiments, each of the multiple solid nuclear fuel particles is 1.5 × 10 -2 cm 3 Smaller, 6 x 10 -7 cm 3 It has a larger volume.

[0036] In some embodiments, the non-solid matrix has approximately the same density as the multiple solid nuclear fuel particles.

[0037] In some embodiments, the non-solid matrix is ​​less dense than the multiple solid nuclear fuel particles.

[0038] In some other embodiments, the non-solid matrix is ​​denser than the number of solid nuclear fuel particles.

[0039] In some embodiments, the nuclear fuel elements generate energy in a reactor selected from the group consisting of fast-spectrum fission reactors, thermal-spectrum fission reactors, epithermal-spectrum fission reactors, and fission-fusion hybrid reactors.

[0040] In some embodiments, nuclear fuel elements generate energy in a reactor, which is cooled by a coolant selected from the group consisting of liquid metal coolants, liquid salt coolants, gas coolants, water coolants, and heat pipes.

[0041] Nuclear fuel cores for use in various nuclear fuel reactors are also provided. In some embodiments, the nuclear fuel core includes: a plurality of solid nuclear fuel particles, each of which contains nuclear material; a non-solid matrix, in which the plurality of solid nuclear fuel particles are mixed, the non-solid matrix substantially stagnates the plurality of nuclear fuel particles, and the non-solid matrix contains a substance selected from the group consisting of liquid metals, liquid metal alloys, and liquid salts; and a plurality of coolant tubes penetrating the non-solid matrix, each of which contains a fluid coolant.

[0042] Nuclear reactors are also provided. In some embodiments, the reactor includes a power loop and a reactor. In some embodiments, the reactor includes nuclear fuel elements and a coolant. In some embodiments, the nuclear fuel elements include a plurality of solid nuclear fuel particles, each of which contains nuclear material, and a non-solid matrix. In some embodiments, the plurality of solid nuclear fuel particles are mixed in the non-solid matrix. In some embodiments, the non-solid matrix is ​​substantially stagnant with respect to the plurality of solid nuclear fuel particles. In some embodiments, the non-solid matrix includes a material selected from the group consisting of liquid metals, liquid metal alloys, and liquid salts.

[0043] Various nuclear fuel cores having the nuclear fuel elements described herein, as well as methods for manufacturing the nuclear fuel elements, are within the scope of the present invention as shown and described herein.

[0044] Features described in the context of separate aspects and / or embodiments of the present invention may be used together and / or interchangeable as far as possible. Similarly, for brevity, if features are described in the context of a single embodiment, those features may also be provided separately or in any preferred partial combination.

[0045] Further aspects and embodiments of the present invention will become apparent from the "Modes for Carrying Out the Invention" of the present invention, when read in conjunction with the accompanying drawings. [Brief explanation of the drawing]

[0046] The accompanying drawings incorporated herein, and constituting part thereof, illustrate embodiments of the invention and, together with the description, help to illustrate the principles of the disclosed embodiments. For clarity, brevity, and flexibility, not all elements, components, or specifications are shown in all drawings. Not all drawings corresponding to a particular step or embodiment of the invention are drawn to scale. Instead, emphasis is placed on illustrating the nature, function, and products of the manufacturing methods and devices described herein.

[0047] The embodiments of the present invention described herein are illustrative and not limiting. Hereinafter, embodiments will be described by reference to the accompanying drawings.

[0048] [Figure 1] This exhibits a fast breeder burning type reactor with a pool design, i.e., a breeder reactor, as an example of prior art. [Figure 2] This demonstrates the filling of fuel particles using prior art. [Figure 3] An enlarged cross-sectional view of fuel particles, a second enlarged cross-sectional view of fuel particles in a stagnant matrix, and fuel particles and stagnant matrix filling in a fuel reactor core are shown according to an embodiment of the present invention. [Figure 4] This shows an enlarged cross-sectional view of a fuel reactor core containing fuel particles and a stasis matrix within the containment vessel, according to an embodiment of the present invention. [Figure 5] Another enlarged cross-sectional view of a fuel reactor core, including fuel particles and a stasis matrix within the containment vessel, according to an embodiment of the present invention. [Figure 6] This shows yet another enlarged cross-sectional view of a fuel reactor core, including fuel particles and a stasis matrix within the containment vessel, according to an embodiment of the present invention. [Figure 7]An exemplary embodiment of the present invention illustrates a nuclear fuel reactor having a novel fuel core. [Figure 8] The present invention illustrates alternative embodiments of fuel particles and stagnation matrix. [Figure 9] An embodiment of the present invention provides an alternative embodiment for fuel particles. [Figure 10] An alternative embodiment of the stagnation matrix according to an embodiment of the present invention is shown. [Figure 11] This shows a flowchart of a method for producing nuclear fuel according to an embodiment of the present invention. [Figure 12] This image shows a photograph of a batch of fuel particles mixed in a liquid-form stasis matrix, according to one embodiment of the present invention. [Figure 13] A photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention is shown. [Figure 14] A photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention is shown. [Figure 15] Another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention is shown. [Figure 16] Another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention is shown. [Figure 17] Another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention is shown. [Figure 18] Another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention is shown. [Figure 19] Another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention is shown. [Figure 20] Another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention is shown. [Modes for carrying out the invention]

[0049] In the following description, numerous specific details are provided for illustrative purposes to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be carried out without these specific details. Embodiments consistent with the invention are described in detail, and such embodiments are shown in the accompanying drawings. The following description includes many details for illustrative purposes, but those skilled in the art will understand that many variations and / or modifications to the suggested details are within the scope of the invention. Similarly, many of the features of the invention are described with respect to or in relation to each other, but those skilled in the art will understand that many of these features can be provided independently of other features. Therefore, this description of the invention is written without loss of generality to the invention and without imposing limitations on the invention.

[0050] This invention relates to fuel design. According to one embodiment, the invention is described in relation to a breeder burn sodium-cooled fast reactor. Various embodiments of the invention may be used in, or modified for use in, any other type of nuclear system, including but not limited to fission reactors, fusion reactors, radioisotope energy systems, and accelerator systems.

[0051] Nuclear reactor context Figure 1 shows a fast breeder burning type, i.e., a breeder reactor, with a pool design, by an exemplary reactor of the prior art. The reactor is characterized by a pool of liquid metal coolant 114, typically filled with sodium or lead, which serves to cool the core and facilitate heat transfer. The reactor typically houses a solid fissile fuel core 106, which is the primary source of fission. In existing designs, this core typically consists of a solid matrix material, often a mixture of parental and fissile isotopes embedded in graphite. The solid fuel core 106 is immersed in liquid metal coolant 114, which is pumped into the reactor pool 120 by a reactor pool pump 110, and circulates within the reactor pool 120. The solid fuel core 106 may also be surrounded by a parental breeder blanket 108, which serves to capture any leaked neutrons and convert them into additional fissile material, further increasing the efficiency of the reactor. The fuel core may also be surrounded by a neutron reflector, which may consist of liquid lead (Pb). Control rods 102 are incorporated into the reactor, which can be inserted or withdrawn to control the rate of nuclear fission. These rods are made of a neutron-absorbing material such as boron or cadmium, and their movement may be adjusted to maintain a desired level of reactivity within the core. Surrounding the reactor is a biological shielding material 112, which may consist of concrete or a material such as lead, designed to protect personnel and the environment from radiation emitted during reactor operation.

[0052] The solid fuel core 106 generates heat through the nuclear fission process, and this heat is transferred to the liquid metal coolant 114 surrounding the fuel core 106. A heat exchanger 116 facilitates the transfer of heat from the liquid metal coolant 114 in the reactor pool 120 to the intermediate loop 122. In the power generation loop 130, the heat from the liquid metal coolant is used in the steam generator 118 to produce steam 132, which powers the output turbine 134 to generate electricity. Water 136 flows back from the output turbine 134 to the steam generator 118. Flow baffles 104 may be placed in the reactor pool 120 to facilitate coolant flow and enhance heat transfer from the fuel core 106 to the liquid metal coolant 114 in the reactor pool 120.

[0053] Figure 2 shows the prior art method of filling fuel particles. The fuel particles 210 are filled into a solid nuclear fuel molded body 220, the solid nuclear fuel compressor is placed inside a solid fuel rod 230, and the solid fuel rod is then placed inside a solid fuel assembly 240 together with coolant tubes 244. A three-layer isotropic (TRISO) fuel particle 210 according to one embodiment of the present invention is shown in an enlarged three-dimensional section. At the core of the particle is a fuel kernel 218, typically composed of uranium, thorium, or plutonium. This fuel kernel acts as the primary source of fission. Surrounding the fuel kernel 218 is a porous carbon buffer layer 216. This layer is designed to absorb fission gases and relieve stress on the outer layer caused by heat and radiation from the fuel kernel. Wrapping around the porous carbon buffer layer 216 is one of two pyrolysis carbon layers 212. This inner pyrolysis carbon layer is denser and acts as an additional barrier against leakage of fission products. The next layer 214 is composed of silicon carbide, a material known for its excellent heat resistance and mechanical strength. This silicon carbide layer 214 provides a robust barrier against the release of fission products, even under extreme conditions. Finally, the outermost layer is another layer of pyrolysis carbon 212, similar to the inner layer of pyrolysis carbon. This outer layer provides additional containment and protection to the fuel kernel 218. The multilayer design of TRISO particles is essential to their role in enhancing reactor safety.

[0054] Next, the TRISO particles 210 are embedded within a solid fuel mold 220, which is stacked within the fuel rods 230, and the fuel rods house the fuel mold 234, the fuel mold 220 being, for example, located within a graphite sleeve 236. The fuel rods are positioned along the coolant tubes 224 within the channels of the fuel assembly 240 in the reactor core. More specifically, the solid fuel mold 220, which houses a large number of TRISO particles, is intended to provide an additional containment layer and facilitate efficient heat transfer. The solid fuel mold 234 is typically made of a graphite matrix and is positioned within the fuel rods 230, and the fuel rods may have a surrounding graphite sleeve 236 and plugs 232 to secure the fuel mold 234 within the fuel rods. The fuel rods 242 are positioned within the fuel assembly 240, the fuel rods 230 being, for example, located in close proximity to the coolant tubes. The fuel assembly 240 is typically composed of a solid, high-strength, corrosion-resistant material, such as a zirconium alloy, capable of withstanding the high temperatures and pressures within the reactor core. Coolant tubes 244, filled with liquid sodium coolant, are intended to maintain the reactor core temperature by removing the heat generated during nuclear fission. However, this arrangement of solid fuel bodies 234 in a solid fuel assembly 240 with liquid sodium coolant tubes 244 introduces stability problems due to the positive "void value" of the sodium coolant, which leads to undesirable positive reactivity feedback in the reactor. The present invention addresses this problem and other problems related to the associated embodiments using a novel fuel design.

[0055] Improved nuclear fuel and fuel core design Figure 3 shows a nuclear fuel element 320 according to one embodiment of the present invention. The fuel element 320 comprises nuclear fuel particles 322 mixed in a substantially stagnant matrix 324. As used herein, “stagnant” refers to the negligible relative motion of the matrix with respect to the TRISO fuel particles. The matrix is ​​substantially stagnant in that it is at rest with respect to the fuel particles except for thermal expansion and mixing. The fuel particles mixed in the matrix may be immersed, submerged, suspended, embedded, or suspended within the matrix. The matrix is ​​not a coolant, does not flow through the turbine or extracore heat exchanger, and is at rest with respect to the fuel particles except for the aforementioned thermal expansion and mixing. Selections of alternative materials for the fuel particles 322 and the stagnant matrix 324 are shown in Figures 8 to 10.

[0056] The fuel particles 322 are mixed in a stagnation matrix 324 at a high volumetric fraction. In some embodiments, the density of the stagnation matrix 324 is substantially the same as the density of the fuel particles 322. In other embodiments, the density of the stagnation matrix 324 is less than the density of the fuel particles 322. In yet another embodiment, the density of the stagnation matrix 324 is greater than the density of the fuel particles 322. In some embodiments, the fuel particles 322 are spherical. It should be noted that when the fuel element 320 is presented in a two-dimensional (2D) cross-sectional slice as shown, the apparent volumetric fraction of the spherical particles is lower than the actual three-dimensional (3D) volumetric fraction. However, it will be apparent to those skilled in the art that the teachings of this disclosure can be extended to use any type of spherical fuel particles in any type of matrix at any volumetric fraction.

[0057] In some embodiments, the substantially stagnant matrix 324 is a non-solid matrix. According to one embodiment, the substantially stagnant matrix 324 may be a mixture of liquid lead (Pb) and liquid sodium (Na), for example, a mixture of 60% lead and 40% sodium. The liquid lead is denser than the fuel particles 322. The liquid sodium is less dense than the fuel particles 322. According to another embodiment, the stagnant matrix 324 may be a mixture of lead (Pb) and lithium (Li). Additional embodiments are described in the section on alternative embodiments of fuel element compositions.

[0058] According to one embodiment, the nuclear fuel particles 322 mixed in the stasis matrix 324 may be TRISO fuel particles. Embodiments of fuel particles 322 containing TRISO fuel particles are shown in the enlarged three-dimensional section 310. At the core of the fuel particles is a fuel kernel 318, typically composed of uranium, thorium, or plutonium. This fuel kernel 318 acts as the primary source of nuclear fission. Surrounding the fuel kernel 318 is a porous carbon buffer layer 316.

[0059] This layer is designed to absorb fission gases and relieve stress on the outer layer caused by heat and radiation from the fuel kernel. The porous carbon buffer layer 316 is surrounded by one of two pyrolysis carbon layers 312. This inner pyrolysis carbon layer is dense and acts as an additional barrier against the leakage of fission products. The next layer 314 is made of silicon carbide (SiC), a material known for its excellent heat resistance and mechanical strength. This silicon carbide layer 314 provides a robust barrier against the release of fission products, even under extreme conditions. Finally, the outermost layer is another layer 312 of pyrolysis carbon, similar to the inner layers of pyrolysis carbon. This outer layer provides additional containment and protection to the fuel kernel 318. The multilayer design of TRISO particles is essential to their role in enhancing reactor safety.

[0060] As further detailed in the sections on simulation results and advantages over existing designs, in some embodiments, when the stagnation matrix surrounding the fuel particles is in liquid form, it has high thermal expansion, which provides a negative reactivity feedback that dominates any positive reactivity feedback from the sodium coolant present in sodium-cooled reactor designs. The use of TRISO fuel particles in some embodiments further provides containment of fission products within the fuel particles, preventing undesirable reactions between fission products in larger fuel cores. Overall, the fuel elements of the present invention have safe and stable reactivity, enabling high fuel utilization with a very low risk of radioactive release.

[0061] The configuration and / or composition of the fuel particles 322 are not limited to the embodiments described above. Instead, it should be understood that fuel particles 322 consistent with the present disclosure may include one or more additional layers, or may omit one or more layers, depending on the desired properties of the fuel particles 322.

[0062] The disclosed fuel designs can be extended to any solid macroscopic ceramic particles (e.g., TRISO particles) mixed in any matrix (e.g., liquid metal, molten salt), the mixing including immersion, sedimentation, suspension, or flotation of the particles. Further embodiments are described in the following sections.

[0063] In some embodiments, the nuclear fuel 334, including a nuclear fuel element 320 containing a substantially stagnant matrix 324 and mixed nuclear fuel particles 322, may be housed inside a large butt 332 inside the nuclear fuel core 330. The nuclear fuel 334 is permeated by a plurality of coolant tubes 335. The plurality of coolant tubes contain a coolant used to remove or transfer heat from the fuel core 330. The nuclear fuel 334, including the stagnant matrix containing mixed fuel particles, fills the entire volume inside the butt 332 of the fuel core 330, except for the coolant tubes 335 that contain the coolant.

[0064] According to one embodiment, the fuel core 330 may be the reactor core. In some embodiments, the inner portion of the fuel core 332 exhibits 1 / 6 symmetry (e.g., a hexagonal cross-section that is invariant under rotations of integer multiples of 60 degrees). The coolant tubes 336 may be formed of a material that can withstand extremely high radiation damage over long periods of time, such as ceramic. In some embodiments, the ceramic material is silicon carbide (SiC) or zirconium carbide (ZrC).

[0065] Figure 4 shows a top view 410 and a side view 420 of the nuclear fuel core 330, as initially described in Figure 3, according to one embodiment of the present invention. The fuel core 330 includes a large butt 332 containing nuclear fuel elements 334, each containing a substantially stagnant matrix and mixed nuclear fuel particles. The matrix-particle fuel elements 334 are perforated by a plurality of coolant tubes 336.

[0066] Figure 5 shows a first enlarged cross-sectional view of a nuclear fuel element 334 according to one embodiment of the present invention, which includes a substantially stagnant matrix and mixed fuel particles, the stagnant matrix being permeated by a plurality of coolant tubes 336. The coolant tubes 336 may contain separate fluid coolants 502.

[0067] Figure 6 shows a second enlarged cross-sectional view of a fuel element 334 and a coolant tube 336 according to one embodiment of the present invention. The fuel element 334 may include a substantially stagnant matrix mixed with a plurality of fuel particles. The matrix-particulate fuel element 334 is further perforated by a tube 336 that houses a separate fluid coolant 502. In one embodiment, the coolant 502 may be a liquid sodium (Na) coolant.

[0068] Figure 7 shows exemplary embodiments of a fast breeder burning reactor having a pool design utilizing a novel fuel core 330 having novel fuel elements, according to several embodiments of the present invention. At the center of the reactor is an innovative fuel core 330 containing fuel particles mixed in a stagnant matrix. In one embodiment, the fuel core 330, shown earlier in Figure 3 along with the top and side section views shown in Figure 4, consists of fuel particles immersed in a substantially stagnant matrix of the same density as the fuel particles, thereby suspending the fuel particles in the matrix. It should be noted herein that “stagnant” refers to the negligible relative motion of the matrix with respect to the fuel particles. The fuel core is permeated by a number of coolant tubes containing separate fluid coolants. In some embodiments, the coolant tubes are ceramic coolant tubes, and the fluid coolant is liquid sodium or lead. In some embodiments, the fuel particles are TRISO fuel particles.

[0069] The coolant flows from a liquid metal coolant 714 in the reactor pool 720. The liquid metal coolant 714 is typically filled with sodium or lead and serves to cool the reactor's fuel core 330 and facilitate heat transfer. The liquid metal coolant 114 is pumped into the reactor pool 720 by a reactor pool pump 710 and circulates within the reactor pool 720. The fuel core 330 may also be surrounded by a parent material breeding blanket 708, which serves to capture any leaked neutrons and convert them into additional fissile material, further increasing the reactor's efficiency. The fuel core may also be surrounded by a neutron reflector, which may consist of liquid lead (Pb).

[0070] The fuel core 330 generates heat through the process of nuclear fission, and this heat is transferred to the liquid metal coolant 714 that surrounds the fuel core 330 and flows through coolant tubes within the fuel core 330. A heat exchanger 716 facilitates the transfer of heat from the liquid metal coolant 714 in the reactor pool 720 to the intermediate loop 722. In the power generation loop 730, the heat from the liquid metal coolant is used to generate steam 732, which powers the output turbine 734 to generate electricity. Water 736 flows from the output turbine 734 back to the steam generator 718. Flow baffles 704 may be placed in the reactor pool 720 to facilitate coolant flow and enhance heat transfer from the fuel core 330 to the liquid metal coolant 714 in the reactor pool 720.

[0071] Alternative Embodiments of Fuel Element Compositions Figure 8 presents a tree diagram illustrating various potential embodiments of the present invention. This chart begins with the main concept of the fuel element 810 at the root and branches into two main categories: nuclear fuel particles 820, which have a corresponding subtree with 820 at the root, and a stagnant matrix 830, which has a corresponding subtree with 830 at the root. As described above, the fuel particles are mixed in a matrix that is substantially stationary relative to the fuel particles.

[0072] The subtree rooted in nuclear fuel particles 820 is further subdivided into various types of fuel particles that can be used, including various materials 822 used in the fuel particles, fuel particle kernel composition 824, and fuel particle size 826. Each of these fuel types is further subdivided into different possible configurations, as shown in detail in Figure 9.

[0073] The stagnation matrix subtree 830 explores different materials that could be used to form the matrix into which the fuel particles are mixed. This includes branches for fluids 840, including liquids 842 and supercritical fluids 844, as well as for solids 850 of predetermined properties that constitute the matrix. Each subbranch is further divided into different possible properties, compositions, and structures, such as different density values ​​for the density of fuel particles and material composition, as shown in more detail in Figure 10.

[0074] The tree diagram in Figure 8 illustrates the versatility and adaptability of the present invention with respect to fuel design, highlighting the possibility of customization to meet specific reactor requirements or operating conditions.

[0075] Figure 9 shows a tree diagram depicting a subtree rooted at a nuclear fuel particle 820 that branches from the tree initially introduced in Figure 8, and illustrates various embodiments of the present invention. These examples are not intended to limit the scope of the present disclosure and are provided as possible implementations. The nuclear fuel particle may be composed of different materials 822, including but not limited to ceramic, carbon, and metallic materials. In some embodiments, the nuclear fuel particle may also be composed of a cermet material. A cermet, as a composite material composed of ceramic and metallic components, can provide a balance between the high-temperature resistance and hardness of the ceramic and the thermal conductivity of the metal. This balance can potentially enhance the performance of the fuel particle, particularly in the high-temperature environments typically encountered within a nuclear reactor. The ceramic component of the cermet can be designed to encapsulate the nuclear fuel, while the metallic component can facilitate the conduction of heat away from the fuel, thereby contributing to the overall efficiency and safety of reactor operation. Examples of partially ceramic nuclear fuel particles and partially carbon nuclear fuel particles include the particles of Group 934 and the particles listed in Table 2. Additionally, Table 3 lists the types of fuel kernels that can be used within Group 936 of TRISO particles, bilayer isotropic (BISO) particles, and quadruple layer isotropic (QUADRISO) particles in some embodiments of the present invention. The nuclear fuel particle may have various fuel compositions 824, including but not limited to fissile materials, fertile materials, and materials used for activation, breeding, or radioisotope production. Table 1 lists fissile materials 932, including but not limited to uranium, thorium, plutonium, and other actinides, that can be used in nuclear fuel particles in some embodiments of the present invention. Table 4 lists fertile materials 938 for activation, breeding, or radioisotope production that can be used in fuel particles in some embodiments of the present invention. The nuclear fuel particle may also have any given volume, medium size (volume < 0.5 cm 3 ), small size (volume < 0.015 cm 3 ), or fine size (any volume > 6×10 -7 cm 3 and volume < 0.015 cm 3) may include but not limited to these, various sizes of 826. Nuclear fuel particles are 6 / 10 -7 cm 3 It may be larger. The sizes mentioned are not intended to limit the scope of this disclosure, but are provided as possible implementations.

[0076] Figure 10 presents a tree diagram showing a subtree rooted in the stagnation matrix 830, which is a branch of the tree initially introduced in Figure 8, illustrating various embodiments of the present invention. The stagnation matrix 830, designed to mix nuclear fuel particles, may consist of either a non-solid matrix or a solid matrix having predetermined properties. The non-solid matrix may include a fluid 840, which may be further classified as a liquid 842 or a supercritical fluid 844.

[0077] The liquid matrix 842 may exhibit various densities 1040 with respect to the mixed particles, including but not limited to densities lower than, equivalent to, or higher than, the nuclear fuel particles dispersed within it. The liquid matrix composition 1050 may include, but is not limited to, liquid metals, liquid metallomonides, liquid metalloids, molten salts, water, organic fluids, glass, or other suitable substances. Specific examples of liquid metals 1052 and molten salts 1054 that can be used in the matrix are listed in Tables 5 and 6, respectively. In some embodiments, the liquid matrix includes a liquid metal alloy of Sn-Al. In some embodiments, the matrix includes tin, lead, sodium, aluminum, bismuth, zinc, magnesium, calcium, cerium, rubidium, zirconium, silicon, beryllium, potassium, yttrium, strontium, germanium, barium, and alloys thereof. The stagnant matrix may include metals and metalloids such as silicon and germanium. In some embodiments, the matrix includes tin, tin-aluminum alloys, tin-aluminum-gallium alloys, tin-zinc-aluminum alloys, tin-magnesium alloys, tin-aluminum-magnesium alloys, and tin-magnesium-zinc alloys. In the case of tin alloys, a compositional percentage of tin exceeding 80% or exceeding 90% by mass fraction may be used. In some embodiments, the matrix includes liquid metal or liquid metal alloys of lead, lead-bismuth-tin alloys, lead-magnesium alloys, sodium-lead alloys, sodium-lead-bismuth alloys, sodium-bismuth alloys, lead-bismuth alloys, or lead-bismuth eutectic alloys. The matrix may also include liquid sodium or liquid gallium. In some embodiments, the matrix may include alloys of tin, aluminum, and gallium; alloys of tin, aluminum, lead, and bismuth; alloys of lead and magnesium; alloys of aluminum and magnesium; alloys of magnesium and zinc; alloys of bismuth and sodium; or alloys of lead and sodium. In some embodiments, the matrix may include lead-and-lithium alloys; tin-and-lithium alloys; or lead, bismuth, and lithium alloys.In some embodiments, the matrix may further include a liquid salt, water, sulfur, a supercritical fluid, and / or another organic or inorganic liquid or semi-liquid. Note that in the Pb-Al and Pb-Bi-Al embodiments characterized in Table 5, since Pb and Al do not alloy, liquid Al lies on top of liquid Pb, and intermediate density fuel particles are suspended around the Al-Pb boundary.

[0078] The water used in the matrix may include light water or heavy water (option 1056). In some embodiments, the liquid matrix may consist of other substances (1058) including but not limited to S or S compounds, P or P compounds, and Br or Br compounds. A supercritical fluid (844) may also be used as the matrix and may include, among other things, substances (1060) such as S-CO2, S-H2O, S-CH4, and S-C2H6. For a solid matrix (850) with predetermined properties, substances (1070) such as polyethylene, other plastics or polymers, and metal hydrides (including but not limited to ZrH, YH, and CaH) may be used according to one embodiment of the present disclosure.

[0079] Tables 1-4 show the material composition of fuel particle substitutes. Tables 5-6 show the material composition of stagnation matrix substitutes.

[0080] [Table 1]

[0081] [Table 2]

[0082] [Table 3]

[0083] [Table 4]

[0084] [Table 5] * Pb and Al do not form an alloy; the liquid Al is on top of the liquid Pb.

[0085] [Table 6]

[0086] Exemplary manufacturing methods and uses of nuclear fuel Figure 11 shows a flow chart of a method for producing nuclear fuel according to an embodiment of the present invention. In step 1102, a particle-matrix mixture is produced by mixing solid fuel particles, such as TRISO particles, in a matrix, such as a mixture of liquid lead and liquid sodium. The matrix may have a density greater than, less than, or equivalent to that of the fuel particles. In step 1104, the process then moves to a cooling and solidification stage, during which the mixture is allowed to cool in a mold or casting. As the mixture cools, it transitions from a liquid state to a solid state, potentially forming a plurality of solid fuel molded bodies. In step 1106, the plurality of solid fuel molded bodies are inserted into the reactor core to prepare fuel for use in the reactor. In step 1108, during reactor operation, the solid fuel is in a liquid state at operating temperatures and can function as liquid fuel in the reactor. The matrix remains substantially stagnant relative to the fuel particles during operation. During operation, the fuel solution may need to be periodically mixed or agitated.

[0087] While the method for producing nuclear fuel is described with reference to a specific set of steps involving the use of TRISO particles and a liquid metal matrix, it will be understood by those skilled in the art that various modifications can be made and equivalents can be used in place of those elements without departing from the scope of this disclosure. For example, other types of fuel particles can be used, or the cooling and solidification processes can be modified.

[0088] Furthermore, without departing from the scope of this disclosure, many modifications can be made to adapt the method to different types of furnaces or fuels, or to optimize the method for specific operating conditions. For example, the method can be adapted for use with different types of coolants, or the fuel can be prepared in different forms or shapes. Thus, this disclosure is not limited to the specific method disclosed as a preferred form intended for carrying out this disclosure, and this disclosure is intended to include all variations and modifications within the spirit and scope of this disclosure.

[0089] Experimental results Figures 12–20 show photographs of exemplary batches of fuel elements containing solid particles mixed in a stasis matrix. The batches use yttria-stabilized zirconia (YSZ) ceramic spheres (1 mm in diameter) as a substitute for TRISO nuclear fuel particles. The particles remain well suspended despite not having exactly the same density as the metal alloy fluid in which they are immersed. When the balls are small enough, the surface area-to-volume ratio becomes sufficiently high. Furthermore, while buoyancy and gravity are proportional to volume, viscous forces are proportional to surface area. Therefore, when these particles are small enough that viscous forces dominate buoyancy and gravity, and consequently the density of the balls is on the same order of magnitude as the fluid density, the particle motion is significantly slowed. Viscous forces do not permanently fix the particles, but they slow down the particle motion to a timescale far longer than the most relevant reactor transient events.

[0090] As an example, assume that the particles are slightly denser than the fluid. Initially, they are settled at the bottom, stacked, or piled up (filling fraction approximately 64%). When the particles are suddenly heated by a thermal power spike, the fluid expands due to thermal expansion, and if the fluid is sufficiently viscous, the particles will initially rise with the fluid (reducing the filling fraction). This provides a very strong negative reactivity feedback for reactor safety. The particles then settle back down to their original positions, much more slowly and gradually. High viscosity is key to ensuring that this resettling timescale is longer than the nuclear transient timescale and the initial fluid thermal expansion.

[0091] Figure 12 shows a photograph of a batch of fuel elements in liquid form according to one embodiment of the present invention. YSZ particles are immersed in a liquid metal matrix. In this exemplary experiment, a tin-indium alloy was used as the liquid metal alloy matrix and was chosen for its low melting point to facilitate the initial testing phase. Figure 12 photographs the earliest experiment conducted to verify whether the YSZ particles remain suspended and immersed in the liquid metal matrix, showing that the YSZ particles remain suspended and immersed within the liquid metal matrix. It should be noted that the tin-indium alloy was chosen primarily as a proof-of-concept, and that it is unlikely to be actually used in a reactor due to the strong neutron absorption properties of indium. Various matrix compositions that may be used in a reactor are shown in Figures 13–20 and described above in this disclosure.

[0092] Figure 13 shows a photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention. The fuel elements comprise a tin-zinc-aluminum alloy matrix and YSZ ceramic spheres as substitutes for TRISO particles.

[0093] Figure 14 shows another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention. The fuel element comprises a tin-zinc-aluminum alloy matrix and YSZ ceramic spheres as substitutes for TRISO particles.

[0094] Figure 15 shows yet another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention. The fuel element comprises a tin-zinc-aluminum alloy matrix and YSZ ceramic spheres as substitutes for TRISO particles.

[0095] Figure 16 shows another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention. The fuel element comprises a tin-zinc-aluminum alloy matrix and YSZ ceramic spheres as substitutes for TRISO particles.

[0096] Figure 17 shows yet another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention. The fuel element comprises a tin-zinc-aluminum alloy matrix and YSZ ceramic spheres as substitutes for TRISO particles.

[0097] Figure 18 shows another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention. The fuel elements comprise a lead-bismuth eutectic alloy matrix and YSZ ceramic spheres as substitutes for TRISO particles.

[0098] Figure 19 shows yet another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention. The fuel element comprises a lead-magnesium alloy matrix and YSZ ceramic spheres as substitutes for TRISO particles.

[0099] Figure 20 shows yet another photograph of a cross-section of a batch of solid fuel elements according to one embodiment of the present invention. The fuel element comprises a lead-sodium alloy matrix and YSZ ceramic spheres as substitutes for TRISO particles.

[0100] Model simulation results The following simulation results demonstrate the feasibility of one embodiment of the present invention for use as fuel in a breeder fission reactor. In one embodiment, spherical TRISO particles having a uranium metal fuel kernel (800 μm in diameter) are suspended in a liquid mixture of approximately 60% Pb metal and 40% Na metal (by volume fraction). The volume filling fraction of these spherical particles is 64%, where the filling fraction refers to the proportion of the total fluid volume occupied by the particles. This fuel is permeated by numerous coolant tubes, which are SiC tubes filled with a flowing liquid Na metal coolant. The entire core is surrounded by a pure liquid Pb neutron reflector. According to one embodiment of the present invention, basic reactor core parameters, including the dimensions of the core and neutron reflector and the fuel particle volume filling fraction, are shown in Table 7.

[0101] [Table 7]

[0102] According to one embodiment, the stagnation matrix surrounding the fuel particles has very large thermal expansion, which causes a large negative reactivity feedback that easily counteracts the positive reactivity feedback of sodium void value. Hereinafter, sodium void value refers to the change in reactivity or fission rate when the sodium coolant in the reactor is removed, i.e., “voided.” A positive sodium void value means that reactivity increases when sodium is voided, leading to an increase in reactor power output and potentially creating a dangerous situation. Furthermore, reactivity feedback refers to the reactor’s response to changes in conditions such as temperature or power output. Positive reactivity feedback occurs when an increase in power output creates conditions that further increase reactivity, generating a self-amplifying cycle. This can potentially lead to a rapid increase in power output, known as a reactor runaway, which can be dangerous. A positive sodium void value contributes to positive reactivity feedback and can potentially lead to a dangerous condition in the reactor. The design of the present invention counteracts this effect by the thermal expansion of the fluid matrix surrounding the fuel particles, resulting in a net negative reactivity. In that case, breeder burn fast reactors can achieve very large-scale and high fuel utilization rates with very stable reactivity, while enjoying high power density and the high economic efficiency of sodium coolant.

[0103] [Table 8]

[0104] The neutron k-effectiveness is a dimensionless neutron parameter that represents the effective neutron multiplication factor of the reactor. When k-effectiveness is greater than 1.0, the neutron chain reaction reactor can reach criticality and be turned on. From the results shown in Table 8 above, it is shown that k-effectiveness is 1.0085 ± 0.0009, which exceeds the threshold of 1.0.

[0105] The fission conversion rate is the ratio of the production rate of fissile plutonium-239 (Pu-239) atoms to the destruction rates of both fissile uranium-235 (U-235) atoms and fissile Pu-239 atoms. The production rate of fissile Pu-239 atoms is mostly due to neutron absorption by U-238 atoms and subsequent decay. The destruction rates of both fissile U-235 and fissile Pu-239 atoms are mostly due to fission. If the fission conversion rate is greater than 1.0, the reactor produces more fissile atoms (fuel for fission) than it consumes. From the results shown in Table 8 above, it is shown that the fission conversion rate is 1.0072 ± 0.0015, which is above the threshold of 1.0. This indicates true breeder combustion physics, i.e., a very high fuel utilization rate, which is made possible by embodiments of this disclosure.

[0106] The delayed neutron fraction is the fraction of all neutrons released in the reactor core that did not directly result from fission. These delayed neutrons arise instead from the decay of various fission products after they emerge from fission. The presence of delayed neutrons on the timescale of fission product decay (seconds to minutes) allows for the safe control of a fission reactor, primarily because the timescale of fission reactions is extremely short (microseconds to milliseconds). The reactor remains stable as long as any rapid perturbation within the reactor changes the k-effective by a fraction smaller than the delayed neutron fraction, and this occurs only when its "reactivity coefficient" is negative, as defined below.

[0107] The stability of a reactor with negative reactivity feedback is verified by calculating the "reactivity coefficient." The reactivity coefficient is the ratio of the k-effectiveness sensitivity to temperature changes of various core materials. The reactivity coefficients due to thermal expansion of the fuel assembly (fuel particles + Na-Pb liquid) and Na-Pb liquid alone, in the absence of fuel particle movement, are calculated. The reactivity coefficients due to thermal expansion of the liquid sodium coolant, silicon carbide coolant tubes, and liquid lead neutron reflector are also calculated. The simulation results of the reactivity coefficients are shown in Table 9.

[0108] The change in k-effectiveness is expressed by dk / kk = 1 / keff1 - 1 / keff2. This can be expressed in dollars or cents, where 1 "dollar" is equal to the "delayed neutron fraction" (in this case, 0.00797). For an "apple-to-apple" comparison over the same temperature change, multiply each reactivity coefficient by the thermal expansion coefficient (CTE) (1 / K) of each substance to obtain the result in units of cents / K.

[0109] The Doppler reactivity coefficient in fuel arises from the Doppler effect, which occurs when the motion of atoms changes at different temperatures, and is calculated on a microscopic neutron cross-section of uranium.

[0110] [Table 9]

[0111] The net reactivity coefficient is strongly negative, primarily due to the fuel aggregate expansion, i.e., the Pb-Na fluid pushing the suspended fuel particles apart. The liquid Na coolant thermal expansion reactivity coefficient is slightly negative here. In some embodiments of the present invention, a large negative fuel coefficient can dominate and overwhelm any positive coolant coefficient that may occur.

[0112] Advantages over existing designs This disclosure provides a novel design for a breeder burn fission energy reactor that offers several advantages over existing designs. One of the key advantages is the use of a stagnant matrix surrounding TRISO particles. As shown in the previous section, this matrix exhibits very large thermal expansion, which, when in liquid form, results in a large negative reactivity feedback. This feedback effectively counteracts the positive reactivity feedback associated with sodium, known as the sodium void value. As a result, the reactor can achieve a breeder burn equilibrium characterized by large scale and high fuel utilization while maintaining stable reactivity. This contributes to the safety of reactor operation. Furthermore, the reactor benefits from a high power density due to the favorable thermal properties of the sodium coolant, which enhances its economic viability.

[0113] These desirable properties are in contrast to existing breeder burn reactor designs, which suffer from the high void value of sodium coolant, resulting in positive reactivity feedback in critical neutron chain reactions when the sodium temperature rises for some reason, reducing its density. Other approaches attempt to mitigate the sodium void value problem by slowing neutrons with lead or gas coolants. However, equilibrium burnup, defined as the fraction of uranium atoms that fiss when the reactor's breeder rate and burnup rate are balanced to eventually achieve equilibrium in order to achieve the high neutron energy spectrum required for the breeder burnup process, can exceed a threshold that any solid uranium-based fuel can sustain while maintaining structural and mechanical integrity. This can potentially lead to the problematic decay of the solid fuel.

[0114] This design of hybrid fuel, made from fuel particles mixed in a matrix, offers additional advantages through the properties of solid fuel particles. The use of TRISO fuel particles in some embodiments of the present invention further provides containment of fission products within the fuel particles, preventing undesirable reactions between fission products in larger fuel cores. This also addresses the reactivity stability issues with liquid fuel, but differs from molten salt reactors (MSRs), which result in mixing of fission products within the fuel core, leading to a "periodic table soup" and increasing the risk of radioactive release.

[0115] More specifically, TRISO fuel particles contain carbon atoms in their various layers, which weakly relax the neutron energy. Neutrons are still fast enough to achieve breeder burn fuel utilization, but the equilibrium burnup is also very high. Here, equilibrium burnup is the fraction of uranium atoms that undergo nuclear fission when the reactor's breeder rate and burnup rate eventually equalize and reach equilibrium. In some embodiments, TRISO particles can maintain structural integrity while withstanding extremely high burnup levels.

[0116] The disclosed invention of TRISO fuel-matrix particle fuel enables a much lower risk of radiation leakage than is currently known in the art. TRISO fuel particles 310 mixed in a stagnant matrix are structurally more resistant to neutron irradiation, corrosion, oxidation, and high temperatures. Furthermore, when a uranium atom undergoes fission, it splits into two smaller atoms called fission products or fission fragments, which are typically radioactive, can vary in size and number of atoms, and are produced with different probabilities. Most of these fission products are radioactive and decay into other fission fragments. Each TRISO fuel particle acts as its own containment system, holding the fission products under all reactor conditions and preventing them from undesiringly reacting within the larger fuel core.

[0117] Therefore, the use of TRISO particles in this design enables a much lower risk of radiation emission compared to reactors using non-TRISO solid fuels. This eliminates the need for extensive and years-long chemical research and testing, further enhancing the practicality and feasibility of this design. A summary of the advantages and benefits of the fuel design of the present invention is shown in Table 10. One embodiment of the present invention is shown in the last column of Table 10 and, as demonstrated, has good performance in all criteria considered, including fuel utilization rate, power density (and economic desirability), radiation and coolant leakage risks, safety, and stability with respect to coolant void value, as well as technical risks from the unknown chemistry of new nuclear material or reaction by-products. Overall, the fuel design of the present invention enables high fuel utilization rate with safe and stable reactivity and a very low risk of radiation emission.

[0118] [Table 10]

[0119] Additional exemplary uses and embodiments In some embodiments, the disclosed nuclear fuel embodiments may be used to generate energy in a fast-spectrum fission reactor, a thermal-spectrum fission reactor, an epithermal-spectrum fission reactor, or a fission-fusion hybrid reactor. In other embodiments, the disclosed nuclear fuel embodiments may be used to generate energy in a reactor cooled by a liquid metal coolant, a liquid salt coolant, a gas coolant, a water coolant, or a heat pipe.

[0120] The present invention may also be advantageous for the fusion energy industry in both future fusion reactors and fission-fusion hybrid reactors. In a fusion reactor, the design may or may not include the same cooling tubes. TRISO particles may be immersed in a lead-lithium fluid mixture. The lithium allows neutrons to breed tritium, and the first fusion reactors will need to produce tritium to replenish their deuterium-tritium fuel. For fission-fusion hybrid technology, TRISO fuel for the fission component is highly desirable because there is no leakage of fission products. The breeder burn and highly stable reactivity characteristics of the fuel design are also very attractive for more efficient use of fission fuel by breeding plutonium. The combination of containment of fission products in TRISO and a matrix that can be mixed (effectively shuffled) without being removed from the reactor, as disclosed in the present invention, makes an attractive option for increasing fusion energy based on fission. Various embodiments of the present invention may be used in, or modified for, any other type of nuclear system, including but not limited to, fission reactors, fusion reactors, fission-fusion hybrid reactors, radioisotope energy systems, and accelerator systems.

[0121] Other embodiments of the present invention will be apparent to those skilled in the art from the discussion herein and the practices of the present invention disclosed herein. This specification and the examples are for illustrative purposes only, and various other embodiments and alternative practices are intended to be within the scope of the present invention.

Claims

1. A nuclear fuel element, A plurality of solid nuclear fuel particles, wherein each of the plurality of solid nuclear fuel particles contains nuclear material, Non-solid matrix, The plurality of solid nuclear fuel particles are mixed in the non-solid matrix, The non-solid matrix is ​​substantially stagnant with respect to the plurality of solid nuclear fuel particles, A nuclear fuel element comprising a non-solid matrix, wherein the non-solid matrix comprises a substance selected from the group consisting of liquid metals, liquid metal alloys, and liquid salts.

2. The nuclear fuel element according to claim 1, wherein the plurality of solid nuclear fuel particles include three-layered isotropic (TRISO) particles.

3. The nuclear fuel element according to claim 1, wherein the non-solid matrix is ​​selected from the group consisting of liquid metals and liquid metal alloys.

4. The nuclear fuel element according to claim 1, wherein the non-solid matrix is ​​selected from the group consisting of tin, lead, sodium, aluminum, bismuth, zinc, magnesium, calcium, cerium, rubidium, zirconium, beryllium, potassium, yttrium, strontium, barium, and alloys thereof.

5. The nuclear fuel element according to claim 1, wherein the non-solid matrix further comprises an element selected from the group consisting of silicon and germanium.

6. The nuclear fuel element according to claim 1, wherein the non-solid matrix is ​​selected from the group consisting of tin, tin-aluminum alloy, tin-aluminum-gallium alloy, tin-zinc-aluminum alloy, tin-magnesium alloy, tin-aluminum-magnesium alloy, and tin-magnesium-zinc alloy.

7. The nuclear fuel element according to claim 6, wherein the compositional percentage of tin in the non-solid matrix is ​​more than 80 percent by mass fraction.

8. The nuclear fuel element according to claim 1, wherein the non-solid matrix is ​​selected from the group consisting of lead, lead-bismuth-tin alloy, and lead-magnesium alloy.

9. The nuclear fuel element according to claim 1, wherein the non-solid matrix is ​​selected from the group consisting of sodium-lead alloy, sodium-lead-bismuth alloy, and sodium-bismuth alloy.

10. The nuclear fuel element according to claim 1, wherein the non-solid matrix is ​​selected from the group consisting of lead-bismuth alloys and lead-bismuth eutectics.

11. The nuclear fuel element according to claim 1, wherein the non-solid matrix is ​​liquid sodium.

12. The nuclear fuel element according to claim 1, wherein the non-solid matrix is ​​liquid gallium.

13. The non-solid matrix is Alloys of tin, aluminum, and gallium; Alloys of tin, aluminum, lead, and bismuth; Lead and magnesium alloys; Aluminum and magnesium alloys; Alloys of magnesium and zinc; Alloys of bismuth and sodium; and The nuclear fuel element according to claim 1, comprising an alloy selected from the group consisting of lead and sodium alloys.

14. The nuclear fuel element according to claim 1, wherein the non-solid matrix comprises an alloy of lead and lithium; an alloy of tin and lithium; and an alloy selected from the group consisting of an alloy of lead, bismuth, and lithium.

15. The nuclear fuel element according to claim 1, wherein the non-solid matrix includes a liquid salt.

16. The nuclear fuel element according to claim 1, wherein the non-solid matrix further comprises a substance selected from the group consisting of water, sulfur, supercritical fluid, organic liquid, and inorganic liquid.

17. The plurality of solid nuclear fuel particles include three-layered isotropic (TRISO) particles, The nuclear fuel element according to claim 1, wherein the non-solid matrix is ​​selected from the group consisting of tin-aluminum alloy, tin-aluminum-gallium alloy, lead-bismuth alloy, and lead.

18. The nuclear fuel element according to claim 1, wherein the plurality of solid nuclear fuel particles include particles selected from the group consisting of three-layer isotropic (TRISO) particles, two-layer isotropic particles, and four-layer isotropic particles.

19. The nuclear fuel element according to claim 1, wherein at least one of the plurality of solid nuclear fuel particles comprises one or more materials selected from the group consisting of ceramic materials, metallic materials, carbon materials, and cermet materials.

20. The nuclear fuel element according to claim 1, wherein at least one of the plurality of solid nuclear fuel particles includes an actinide fuel kernel.

21. At least one of the plurality of solid nuclear fuel particles is a UN kernel, UO ２ The nuclear fuel element according to claim 1, comprising a fuel kernel selected from the group consisting of a kernel, a UC kernel, and a UCO kernel.

22. The nuclear fuel element according to claim 1, wherein the nuclear material is selected from the group consisting of fissile material, transmutation material, and parent material.

23. The nuclear fuel element according to claim 1, wherein the plurality of solid nuclear fuel particles include a fissile material selected from the group consisting of uranium, thorium, and plutonium.

24. The nuclear fuel element according to claim 1, wherein the plurality of solid nuclear fuel particles include a transmutation or parent material selected from the group consisting of thulium, thallium, gadolinium, silver, strontium, holmium, and lithium.

25. Each of the aforementioned plurality of solid nuclear fuel particles is 0.5 cm ３ Smaller, 6 x 10 －７ cm ３ A nuclear fuel element according to claim 1, having a larger volume.

26. Each of the plurality of solid nuclear fuel particles is 1.5 × 10 －２ cm ３ Smaller, 6 x 10 －７ cm ３ A nuclear fuel element according to claim 1, having a larger volume.

27. The nuclear fuel element according to claim 1, wherein the non-solid matrix has substantially the same density as the plurality of solid nuclear fuel particles.

28. The nuclear fuel element according to claim 1, wherein the non-solid matrix has a lower density than the plurality of solid nuclear fuel particles.

29. The nuclear fuel element according to claim 1, wherein the non-solid matrix is ​​denser than the plurality of solid nuclear fuel particles.

30. The nuclear fuel element according to claim 1, wherein the nuclear fuel element generates energy in a reactor selected from the group consisting of a fast-spectrum fission reactor, a thermal-spectrum fission reactor, an epithermal-spectrum fission reactor, and a fission-fusion hybrid reactor.

31. The nuclear fuel element according to claim 1, wherein the nuclear fuel element generates energy in a nuclear reactor where it is cooled by a coolant selected from the group consisting of a liquid metal coolant, a liquid salt coolant, a gas coolant, a water coolant, and a heat pipe.

32. It is a nuclear reactor, Power generation loop and A reactor comprising a nuclear fuel element and a coolant, the nuclear fuel element is A plurality of solid nuclear fuel particles, wherein each of the plurality of solid nuclear fuel particles contains nuclear material, Non-solid matrix, The plurality of solid nuclear fuel particles are mixed in the non-solid matrix, The non-solid matrix is ​​substantially stagnant with respect to the plurality of solid nuclear fuel particles, A nuclear reactor comprising a reactor, the reactor comprising a non-solid matrix comprising a substance selected from the group consisting of liquid metals, liquid metal alloys, and liquid salts.

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