Lead-bismuth reactor core adopting metal hydride as moderator

Abstract

The invention belongs to the field of nuclear reactor core structures, and discloses a lead-bismuth reactor core adopting a metal hydride as a moderator, the lead-bismuth reactor core comprises a plurality of fuel assemblies which are arranged from the central area to the peripheral area of the reactor core in a zoning manner, and the fuel assemblies comprise fuel rods and moderation rods; the fuel rod comprises a fuel core body and a lead-bismuth coolant surrounding the fuel core body; the moderator rod comprises a moderator core body and a lead-bismuth cooling agent surrounding the moderator core body, and the moderator core body adopts a metal hydride moderator; the fuel enrichment degrees of the fuel assemblies in different partitions are different, and the fuel enrichment degrees are sequentially increased from inside to outside in the radial direction of the reactor core; the mass contents of burnable poison of the fuel assemblies in different partitions are different, and the mass contents of the burnable poison are sequentially increased from inside to outside in the radial direction of the reactor core. The reactor core design optimization is realized through the strategies of uniform dispersion arrangement of the metal hydride moderation rods, fuel enrichment degree and burnable poison partitioning and the like.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactor core technology, and more specifically, to a lead-bismuth reactor core that uses a metal hydride as a moderator. Background Technology

[0002] Lead-bismuth coolant offers advantages such as low melting point, high boiling point, and chemical stability. Reactors using lead-bismuth coolant can employ an atmospheric pressure design for their primary circuit, significantly reducing core costs compared to the high pressure of pressurized water reactors. Furthermore, the primary coolant does not undergo violent chemical reactions with water or air, resulting in greater economic efficiency and safety. Due to its large atomic mass, lead-bismuth coolant does not moderate neutrons, resulting in a fast energy spectrum for the reactor core. Fissile nuclides such as U-238 can undergo capture reactions under fast neutrons, converting into Pu isotopes such as Pu-239. In other words, a fast-spectrum reactor core using lead-bismuth coolant can convert fissile nuclides into easily fissile nuclides, improving fuel utilization within the core. However, because easily fissile nuclides such as U-235 have small fissile cross-sections under fast neutron conditions, a larger amount of easily fissile nuclides is required for the core to reach criticality. Therefore, compared to thermal and hyperthermal cores, the fuel utilization rate at the end of the core's lifespan is relatively low. Summary of the Invention

[0003] This invention addresses the problems existing in the prior art by providing a lead-bismuth reactor core using metal hydrides as moderators. It leverages the high boiling point and chemical stability of lead-bismuth coolant, while the use of metal hydrides as moderators effectively softens the core energy spectrum. This not only effectively reduces the initial uranium loading during the core's lifespan but also allows for the use of combustible poisons to control the core's remaining reactivity, releasing the reactivity control pressure on the control rods and reducing the potential positive temperature feedback from the metal hydrides. Through strategies such as uniformly distributing the metal hydride moderator rods, fuel enrichment, and zoning of combustible poisons, core design optimization is achieved.

[0004] This invention is achieved through the following technical solution: A lead-bismuth reactor core using a metal hydride as a moderator includes several fuel assemblies arranged in sections from the core center region to the outer region. The fuel assembly includes a fuel rod and a moderator rod. The fuel rod includes a fuel core and a lead-bismuth coolant surrounding the fuel core. The moderator rod includes a moderator core and a lead-bismuth coolant surrounding the moderator core. The moderator core uses a metal hydride moderator. The fuel enrichment of fuel assemblies in different zones is different, and the fuel enrichment increases sequentially from the inside to the outside along the radial direction of the core. The mass content of combustible poison in fuel assemblies varies in different zones, and the mass content of combustible poison increases sequentially from the inside to the outside along the radial direction of the reactor core.

[0005] Optionally, the plurality of fuel assemblies include fuel assemblies without control rods, fuel assemblies with safety rods, and fuel assemblies with compensating rods and regulating rods arranged sequentially along the radial direction of the reactor core from the inside to the outside. The fuel enrichment of the fuel assembly without control rods is 25%, and the mass content of combustible toxic substances is 0.8%; the fuel enrichment of the fuel assembly with safety rods is 28%, and the mass content of combustible toxic substances is 1.2%; the fuel enrichment of the fuel assembly with compensating rods and regulating rods is 31%, and the mass content of combustible toxic substances is 1.5%.

[0006] Optionally, the plurality of fuel assemblies include one 8-ring rod fuel assembly without control rod, six 8-ring rod fuel assemblies with safety rods, and twelve 8-ring rod fuel assemblies with compensating rods and regulating rods arranged sequentially from the inside to the outside along the radial direction of the reactor core. The fuel assembly without control rods includes 114 fuel rods and 55 moderator rods arranged in 8 rings; the fuel assembly with safety rods includes 1 safety rod, 102 fuel rods and 48 moderator rods arranged in 8 rings, with the safety rod located in the central area and occupying 3 rings of rod space; the fuel assembly with compensation rods and regulating rods includes 1 compensation rod and regulating rod, 102 fuel rods and 48 moderator rods arranged in 8 rings, with the compensation rod and regulating rod located in the central area and occupying 3 rings of rod space.

[0007] Optionally, the B4C B-10 content in the 6 fuel assemblies with safety rods is 90%, and the B4C B-10 content in the 12 fuel assemblies with compensating rods and regulating rods is 40%. The value of the 6 safety rods is 4543 pcm, and the value of the 12 compensating rods and regulating rods is 6021 pcm. The average value of a single compensating rod and regulating rod bundle is lower than the core delayed neutron share by 716 pcm.

[0008] Optionally, the plurality of fuel assemblies include fuel assemblies without control rods, fuel assemblies with safety rods, and fuel assemblies with compensating rods and regulating rods arranged sequentially along the radial direction of the reactor core from the inside to the outside. The fuel enrichment of the fuel assembly without control rods is 28%, and the mass content of combustible toxic substances is 0.9%; the fuel enrichment of the fuel assembly with safety rods is 30%, and the mass content of combustible toxic substances is 1.4%; the fuel enrichment of the fuel assembly with compensating rods and regulating rods is 33%, and the mass content of combustible toxic substances is 1.7%.

[0009] Optionally, the plurality of fuel assemblies include one 10-ring fuel assembly without control rods, six 10-ring fuel assemblies with safety rods, and twelve 10-ring fuel assemblies with compensating rods and regulating rods arranged sequentially from the inside to the outside along the radial direction of the reactor core. The fuel assembly without control rods includes 180 fuel rods and 91 moderator rods, arranged in 10 rings; the fuel assembly with safety rods includes 1 safety rod, 159 fuel rods and 75 moderator rods, arranged in 10 rings, with the safety rod located in the central area and occupying 4 rings of space; the fuel assembly with compensation rods and regulating rods includes 1 compensation rod and regulating rod, 159 fuel rods and 75 moderator rods, arranged in 10 rings, with the compensation rod and regulating rod located in the central area and occupying 4 rings of space.

[0010] Optionally, the fuel assembly includes a plurality of fuel rods and moderator rods, with a plurality of fuel rods arranged around each moderator rod.

[0011] Optionally, a combustible toxic substance is uniformly dispersed in the moderation rod.

[0012] Optionally, the metal hydride moderator is zirconium hydride or yttrium hydride.

[0013] Optionally, the fuel core uses oxide ceramic fuel.

[0014] The technical solution of the present invention has at least the following beneficial effects: The lead-bismuth reactor core of this invention uses metal hydrides as moderators. The fuel assemblies adopt a strategy of separately arranging fuel rods and moderator rods. The fuel core can obtain a higher operating temperature. The metal hydrides, as moderator rods, can not only soften the core energy spectrum and reduce the core critical uranium load, but also prevent the temperature of the metal hydride moderator rods from becoming too high, thus avoiding the release of hydrogen from the metal hydride moderator rods and weakening or redistributing the moderation effect. The reactor core of this invention adopts a radial design with fuel enrichment and combustible poison partitioning to flatten the core power distribution. At the same time, it matches the combustible poison content with the core power distribution and core lifespan, minimizing the amount of combustible poison remaining in the core at the end of its lifespan and reducing the end-of-life reactivity penalty of combustible poison. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the fuel rod of the present invention; Figure 2 This is a schematic diagram of the structure of the safety bar of the present invention; Figure 3 This is a schematic diagram of the structure of the compensation rod or adjusting rod of the present invention; Figure 4 This is a schematic diagram of the slowing rod of the present invention; Figure 5 This is a schematic diagram of the structure of the control rod-less fuel assembly of Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the structure of the fuel assembly with compensation rod and regulating rod according to Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the structure of the fuel assembly with safety rods according to Embodiment 1 of the present invention; Figure 8 This is a schematic diagram of the core arrangement of Embodiment 1 of the present invention; Figure 9 This is a schematic diagram of the structure of the control rod-less fuel assembly of Embodiment 2 of the present invention; Figure 10 This is a schematic diagram of the structure of the fuel assembly with compensation rod and regulating rod according to Embodiment 2 of the present invention; Figure 11 This is a schematic diagram of the structure of the fuel assembly with safety rods according to Embodiment 2 of the present invention; Figure 12 This is a schematic diagram of the core arrangement in Embodiment 2 of the present invention.

[0016] Figure label: 1-Fuel core, 2-Helium layer, 3-Stainless steel cladding, 4-Lead-bismuth coolant, 5-B4C core, 6-Air layer, 7-Control rod guide tube, 8-Counterweight tungsten, 9-Moderator core, 51-Fuel rod, 52-Moderator rod, 53-Component box, 54-Compensation rod or regulating rod, 55-Safety rod, 101, 201-Fuel assembly with compensation rod and regulating rod, 102, 202-Fuel assembly with safety rod, 103, 203-Fuel assembly without control rod, 104-Reflective layer. Detailed Implementation

[0017] Reference Figures 1-12 The lead-bismuth reactor core of the present invention, which uses metal hydride as moderator, includes several fuel assemblies arranged in sections from the core center area to the outer area. Each fuel assembly includes independently arranged fuel rods 51 and moderator rods 52. Each fuel rod 51 includes a fuel core 1 and a lead-bismuth coolant 4 surrounding the fuel core 1. The fuel core 1 uses oxide ceramic fuel, which can achieve a high core power density by utilizing its high melting point. The fuel type can be UO2, MOX, etc.

[0018] The moderator rod 52 includes a moderator core 9 and a lead-bismuth coolant 4 surrounding the moderator core 9. The moderator core 9 uses a metal hydride moderator, such as zirconium hydride or yttrium hydride. The hydrogen content in the metal hydride moderator is adjustable. The hydrogen-yttrium stoichiometry ratio in yttrium hydride is selected in the range of 1.7-2.2, preferably 1.85, i.e., UYH1.85. A stoichiometric ratio with stable phase structure is selected to ensure the neutron performance of uranium yttrium hydride. The hydrogen-zirconium stoichiometric ratio in zirconium hydride is selected in the range of 1.59-1.65, preferably 1.6, i.e., UZrH1.6. A stoichiometric ratio with stable phase structure is selected to ensure the neutron performance of uranium zirconium hydride.

[0019] This invention employs a lead-bismuth reactor core with metal hydrides as moderators. The fuel assemblies utilize a strategy of separately arranging fuel rods 51 and moderator rods 52. This allows the fuel core 1 to achieve a higher operating temperature. Furthermore, the metal hydride moderator rods 52 not only soften the core energy spectrum and reduce the critical uranium load in the core, but also prevent the temperature of the metal hydride moderator rods 52 from becoming too high, thus avoiding the release of hydrogen from the metal hydride moderator rods 52 and the resulting weakening or redistribution of the moderation effect.

[0020] The fuel enrichment of fuel assemblies varies in different zones, and increases radially from the inside to the outside of the core. Combustible poisons, preferably erbium, are uniformly dispersed in the moderator rods 52 of the fuel assemblies. This uniform dispersion of erbium in the moderator rods 52 enhances the absorption reactivity of erbium, improving its reactivity control value and reducing the residual amount of erbium combustible poison at the end of its lifespan, thus mitigating the penalty to core reactivity at the end of its lifespan. The mass content of combustible poisons varies in different zones of the fuel assemblies, and increases radially from the inside to the outside of the core.

[0021] The reactor core adopts a radial design with fuel enrichment and combustible poison partitioning to flatten the core power distribution. At the same time, it matches the combustible poison content with the core power distribution and core lifespan, minimizing the amount of combustible poison remaining in the core at the end of its lifespan and reducing the end-of-life reactivity penalty of combustible poison.

[0022] The content of the present invention will be described in detail below with reference to specific embodiments: Example 1 Reference Figures 5-8 This embodiment provides a lead-bismuth reactor core that uses metal hydride as a moderator, with a core power of 8 MWt and a lifespan of 2000 EFPD.

[0023] Reference Figure 8 The reactor core consists of one low-enrichment 8-ring fuel assembly without control rods (103), six medium-enrichment 8-ring fuel assemblies with safety rods (102), twelve high-enrichment 8-ring fuel assemblies with compensating rods and regulating rods (101), and a reflector layer (104) composed of lead-bismuth coolant. The equivalent diameter of the active zone is 68 cm, the height of the active zone is 50 cm, the core height-to-diameter ratio is 0.73, the core power density is 44 W / cm³, the initial uranium loading at the end of the core's life is 0.45 t, and the average burnup depth at the end of the core's life is 36 GWd / tU. One low-enrichment 8-ring fuel assembly without control rods 103 is arranged in the core center region, six medium-enrichment 8-ring fuel assemblies with safety rods 102 and twelve high-enrichment 8-ring fuel assemblies with compensating rods and regulating rods 101 are arranged sequentially on the periphery, and each of the 18 control rod assemblies (including safety rod fuel assemblies 102 and fuel assemblies with compensating rods and regulating rods 101) has a drive mechanism to control the raising or lowering of the control rod absorber into the core.

[0024] The distribution of enrichment is specifically determined by: The reactor core uses UO2 as fuel, and is divided into radial zones based on fuel enrichment and Er poison content. The low-enrichment 8-ring fuel assembly 103 (without control rods) has a fuel enrichment of 25% and an Er poison content of 0.8% by mass; the medium-enrichment 8-ring fuel assembly 102 (with safety rods) has a fuel enrichment of 28% and an Er poison content of 1.2% by mass; and the high-enrichment 8-ring fuel assembly 101 (with compensating and regulating rods) has a fuel enrichment of 31% and an Er poison content of 1.5% by mass.

[0025] In this fuel assembly, several fuel rods 51 and several moderator rods 52 are provided, with several fuel rods 51 arranged around each moderator rod 52. A dispersed arrangement strategy for the moderator rods 52 is adopted within the fuel assembly to ensure that the fuel rods 51 and moderator rods 52 are evenly distributed, thereby improving the moderation performance of the moderator rods 52. For example, in this embodiment, six fuel rods 51 are evenly distributed around each moderator rod 52.

[0026] In this embodiment, the control rodless fuel assembly 103, as shown in Figure 5, includes fuel rods 51, moderator rods 52, assembly box 53, and lead-bismuth coolant 4. The control rodless fuel assembly 103 in this embodiment includes 114 fuel rods 51 and 55 moderator rods 52. Each moderator rod 52 surrounds 6 fuel rods 51, ultimately forming an 8-ring structure. Lead-bismuth coolant 4 is filled between the rods, and an assembly box 53 is provided on the outside.

[0027] Including safety rod fuel assembly 102 Figure 7 As shown, the assembly includes a safety rod 55, a fuel rod 51, a moderator rod 52, an assembly box 53, and a lead-bismuth coolant 4. In this embodiment, the fuel assembly 102 with a safety rod includes one safety rod 55, 102 fuel rods 51, and 48 moderator rods 52, arranged in 8 rings. The safety rod 55 is located in the central area and occupies the space of 3 rings of rods. The space between the rods is filled with lead-bismuth coolant 4, and the assembly box 53 is provided on the outside.

[0028] Fuel assembly 101 including compensating rod and regulating rod, as shown Figure 6 As shown, the fuel assembly 101 includes a compensating rod or regulating rod 54, fuel rods 51, moderator rods 52, an assembly box 53, and lead-bismuth coolant 4. The fuel assembly 101 with compensating rod and regulating rod includes one compensating rod or regulating rod 54, 102 fuel rods 51, and 48 moderator rods 52, arranged in 8 rings. The compensating rod or regulating rod 54 is arranged in the central area and occupies 3 rings of rod space. Lead-bismuth coolant 4 is filled between the rods, and an assembly box 53 is provided on the outside.

[0029] Fuel rod 51 includes, from the inside out, a fuel core 1, a helium layer 2, a stainless steel cladding 3, and a lead-bismuth coolant 4; safety rod 55 includes, from the inside out, a B4C core, a helium layer 2, a stainless steel cladding 3, an air layer 6, a control rod guide tube 7, and a lead-bismuth coolant 4; compensation rod or regulating rod 54 includes, from the inside out, a counterweight tungsten 8, a helium layer 2, a stainless steel cladding 3, a helium layer 2, a B4C core, a helium layer 2, a stainless steel cladding 3, a lead-bismuth coolant 4, a control rod guide tube 7, and a lead-bismuth coolant 4; moderator rod 52 includes, from the inside out, a metal hydride moderator, a helium layer 2, a stainless steel cladding 3, and a lead-bismuth coolant 4.

[0030] The B4C B-10 content in the six fuel assemblies 102 containing safety rods is 90%, and the B4C B-10 content in the twelve fuel assemblies 101 containing compensating and regulating rods is 40%. The value of the six safety rods is 4543 pcm, and the value of the twelve compensating and regulating rods is 6021 pcm. The average value of a single bundle of compensating and regulating rods is lower than the core delayed neutron fraction by 716 pcm. At the same time, the core reactivity control rods meet the design requirements for shutdown depth and sticking rods.

[0031] The core lifting procedure is as follows: all safety rods are lifted at 55°. The 12 compensating rods and regulating rods are symmetrically divided into two groups, namely compensating rods and regulating rods, with 6 groups in each group. The regulating rods are lifted to half the core height, and the compensating rods are lifted to the core criticality. During the burnup process, the compensating rods are lifted to compensate for the burnup reactivity loss. The regulating rods do not need to compensate for the reactivity demand of the rise and fall power or the short-term reaction disturbance compensation.

[0032] This invention employs a modular design with large fuel assemblies and control rods placed within the fuel assemblies. Each fuel assembly contains a bundle of control rods, reducing the number of assemblies within the core, flattening the core power distribution, and effectively improving the core assembly characteristics.

[0033] Example 2 Reference Figures 9-12 This embodiment provides a lead-bismuth reactor core that uses metal hydride as a moderator, with a core power of 20 MWt and a lifespan of 2000 EFPD.

[0034] Reference Figure 12The reactor core consists of one low-enrichment 10-ring fuel assembly without control rods 203, six medium-enrichment 10-ring fuel assemblies with safety rods 202, twelve high-enrichment 10-ring fuel assemblies with compensating rods and regulating rods 201, and a reflector layer 104 composed of lead-bismuth coolant. The equivalent diameter of the active zone is 86 cm, the height of the active zone is 60 cm, the core height-to-diameter ratio is 0.70, the core power density is 58 W / cm3, the initial uranium loading at the end of the core's life is 0.84 t, and the average burnup depth at the end of the core's life is 48 GWd / tU. One low-enrichment 8-ring fuel assembly without control rods 203 is arranged in the core center region, six medium-enrichment 8-ring fuel assemblies with safety rods 202 and twelve high-enrichment 8-ring fuel assemblies with compensating rods and regulating rods 201 are arranged sequentially on the periphery, and each of the 18 control rod assemblies (including safety rod fuel assemblies 202 and compensating rod regulating rod fuel assemblies 201) has a drive mechanism to control the raising or lowering of the control rod absorber into the core.

[0035] The distribution of enrichment is specifically determined by: The reactor core uses UO2 as fuel, and is divided into radial zones based on fuel enrichment and Er poison content. The low-enrichment 10-ring fuel assembly 203 (without control rods) has a fuel enrichment of 28% and an Er poison content of 0.9% by mass; the medium-enrichment 10-ring fuel assembly 202 (with safety rods) has a fuel enrichment of 30% and an Er poison content of 1.4% by mass; and the high-enrichment 10-ring fuel assembly 201 (with compensating and regulating rods) has a fuel enrichment of 33% and an Er poison content of 1.7% by mass.

[0036] In this fuel assembly, several fuel rods 51 and several moderator rods 52 are provided, with several fuel rods 51 arranged around each moderator rod 52. A dispersed arrangement strategy for the moderator rods 52 is adopted within the fuel assembly to ensure that the fuel rods 51 and moderator rods 52 are evenly distributed, thereby improving the moderation performance of the moderator rods 52. For example, in this embodiment, six fuel rods 51 are evenly distributed around each moderator rod 52.

[0037] In this embodiment, the control rodless fuel assembly 203 is as follows: Figure 9 As shown, the fuel assembly 203 without a control rod in this embodiment includes fuel rods 51, moderator rods 52, assembly box 53 and lead-bismuth coolant 4. The fuel assembly 203 includes 180 fuel rods 51 and 91 moderator rods 52. Each moderator rod 52 surrounds 6 fuel rods 51, and finally forms a structure of 10 rings of rods. Lead-bismuth coolant 4 is filled between the rods, and an assembly box 53 is provided on the outside.

[0038] Fuel assembly with safety rod 202 Figure 11As shown, the fuel assembly 202 includes a safety rod 55, fuel rods 51, moderator rods 52, assembly box 53, and lead-bismuth coolant 4. In this embodiment, the fuel assembly 202 with safety rod includes one safety rod 55, 159 fuel rods 51, and 75 moderator rods 52, arranged in 10 rings. The safety rod 55 is located in the central area and occupies 4 rings of rod space. Lead-bismuth coolant 4 is filled between the rods, and the assembly box 53 is provided on the outside.

[0039] Fuel assembly 201 including compensating rod and regulating rod Figure 10 As shown, the fuel assembly 201 includes a compensating rod or regulating rod 54, fuel rods 51, moderator rods 52, an assembly box 53, and lead-bismuth coolant 4. The fuel assembly 201 with compensating rod and regulating rod includes one compensating rod or regulating rod 54, 159 fuel rods 51, and 75 moderator rods 52, arranged in 8 rings. The compensating rod or regulating rod 54 is arranged in the central area and occupies 3 rings of rod space. Lead-bismuth coolant 4 is filled between the rods, and an assembly box 53 is provided on the outside.

[0040] Fuel rod 51 includes, from the inside out, a fuel core 1, a helium layer 2, a stainless steel cladding 3, and a lead-bismuth coolant 4; safety rod 55 includes, from the inside out, a B4C core, a helium layer 2, a stainless steel cladding 3, an air layer 6, a control rod guide tube 7, and a lead-bismuth coolant 4; compensation rod or regulating rod 54 includes, from the inside out, a counterweight tungsten 8, a helium layer 2, a stainless steel cladding 3, a helium layer 2, a B4C core, a helium layer 2, a stainless steel cladding 3, a lead-bismuth coolant 4, a control rod guide tube 7, and a lead-bismuth coolant 4; moderator rod 52 includes, from the inside out, a metal hydride moderator, a helium layer 2, a stainless steel cladding 3, and a lead-bismuth coolant 4.

[0041] The B4C B-10 content in the six fuel assemblies 202 containing safety rods is 90%, and the B4C B-10 content in the twelve fuel assemblies 201 containing compensating and regulating rods is 40%. The value of the six safety rods is 4789 pcm, and the value of the twelve compensating and regulating rods is 6543 pcm. The average value of a single compensating and regulating rod bundle is 732 pcm lower than the core delayed neutron fraction. At the same time, the core reactivity control rods meet the design requirements for shutdown depth and sticking rods.

[0042] The core lifting procedure is as follows: all safety rods are lifted at 55°. The 12 compensating rods and regulating rods are symmetrically divided into two groups, namely compensating rods and regulating rods, with 6 groups in each group. The regulating rods are lifted to half the core height, and the compensating rods are lifted to the core criticality. During the burnup process, the compensating rods are lifted to compensate for the burnup reactivity loss. The regulating rods do not need to compensate for the reactivity demand of the rise and fall power or the short-term reaction disturbance compensation.

[0043] This invention employs a modular design with large fuel assemblies and control rods placed within the fuel assemblies. Each fuel assembly contains a bundle of control rods, reducing the number of assemblies within the core, flattening the core power distribution, and effectively improving the core assembly characteristics.

Claims

1. A lead-bismuth reactor core using a metal hydride as a moderator, comprising a plurality of fuel assemblies arranged in sections from the core center region to the outer perimeter region, characterized in that: The fuel assembly includes a fuel rod and a moderator rod. The fuel rod includes a fuel core and a lead-bismuth coolant surrounding the fuel core. The moderator rod includes a moderator core and a lead-bismuth coolant surrounding the moderator core. The moderator core uses a metal hydride moderator. The fuel enrichment of fuel assemblies in different zones is different, and the fuel enrichment increases sequentially from the inside to the outside along the radial direction of the core. The mass content of combustible poison in fuel assemblies varies in different zones, and the mass content of combustible poison increases sequentially from the inside to the outside along the radial direction of the reactor core.

2. The lead-bismuth reactor core using metal hydrides as moderators according to claim 1, characterized in that: The fuel assemblies include fuel assemblies without control rods, fuel assemblies with safety rods, and fuel assemblies with compensating rods and regulating rods arranged sequentially along the radial direction of the reactor core from the inside to the outside. The fuel enrichment of the fuel assembly without control rods is 25%, and the mass content of combustible toxic substances is 0.8%; the fuel enrichment of the fuel assembly with safety rods is 28%, and the mass content of combustible toxic substances is 1.2%; the fuel enrichment of the fuel assembly with compensating rods and regulating rods is 31%, and the mass content of combustible toxic substances is 1.5%.

3. The lead-bismuth reactor core using metal hydrides as moderators according to claim 1, characterized in that: The fuel assemblies include, in order of radial arrangement from the inside to the outside of the reactor core, one 8-ring rod fuel assembly without control rods, six 8-ring rod fuel assemblies with safety rods, and twelve 8-ring rod fuel assemblies with compensating rods and regulating rods. The fuel assembly without control rods includes 114 fuel rods and 55 moderator rods, arranged in 8 rings; the fuel assembly with safety rods includes 1 safety rod, 102 fuel rods and 48 moderator rods, arranged in 8 rings, with the safety rod located in the central area and occupying 3 rings of rod space; the fuel assembly with compensation rods and regulating rods includes 1 compensation rod and regulating rod, 102 fuel rods and 48 moderator rods, arranged in 8 rings, with the compensation rod and regulating rod located in the central area and occupying 3 rings of rod space.

4. The lead-bismuth reactor core using metal hydrides as moderators according to claim 3, characterized in that: The B4C B-10 content in the 6 fuel assemblies with safety rods is 90%, and the B4C B-10 content in the 12 fuel assemblies with compensating and regulating rods is 40%. The value of the 6 safety rods is 4543 pcm, and the value of the 12 compensating and regulating rods is 6021 pcm. The average value of a single compensating and regulating rod bundle is 716 pcm lower than the core delayed neutron share.

5. The lead-bismuth reactor core using a metal hydride as a moderator according to claim 1, characterized in that: The fuel assemblies include fuel assemblies without control rods, fuel assemblies with safety rods, and fuel assemblies with compensating rods and regulating rods arranged sequentially along the radial direction of the reactor core from the inside to the outside. The fuel enrichment of the fuel assembly without control rods is 28%, and the mass content of combustible toxic substances is 0.9%; the fuel enrichment of the fuel assembly with safety rods is 30%, and the mass content of combustible toxic substances is 1.4%; the fuel enrichment of the fuel assembly with compensating rods and regulating rods is 33%, and the mass content of combustible toxic substances is 1.7%.

6. The lead-bismuth reactor core using a metal hydride as a moderator according to claim 1, characterized in that: The fuel assemblies include, in a radial direction from the inside to the outside of the reactor core, one 10-ring fuel assembly without control rods, six 10-ring fuel assemblies with safety rods, and twelve 10-ring fuel assemblies with compensating rods and regulating rods. The fuel assembly without control rods includes 180 fuel rods and 91 moderator rods, arranged in 10 rings; the fuel assembly with safety rods includes 1 safety rod, 159 fuel rods and 75 moderator rods, arranged in 10 rings, with the safety rod located in the central area and occupying 4 rings of space; the fuel assembly with compensation rods and regulating rods includes 1 compensation rod and regulating rod, 159 fuel rods and 75 moderator rods, arranged in 10 rings, with the compensation rod and regulating rod located in the central area and occupying 4 rings of space.

7. The lead-bismuth reactor core using a metal hydride as a moderator according to claim 3 or 6, characterized in that: The fuel assembly contains several fuel rods and several moderator rods, with several fuel rods arranged around each moderator rod.

8. The lead-bismuth reactor core using a metal hydride as a moderator according to claim 1, characterized in that: The flammable toxic substance is uniformly dispersed in the moderation rod.

9. The lead-bismuth reactor core using a metal hydride as a moderator according to claim 1, characterized in that: The metal hydride moderator is zirconium hydride or yttrium hydride.

10. The lead-bismuth reactor core using a metal hydride as a moderator according to claim 1, characterized in that: The fuel core uses oxide ceramic fuel.

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