Design method of metal hydride reactor with adjustable feedback coefficient and reactor core

Abstract

The invention relates to the technical field of reactor cores, and particularly discloses a design method of a metal hydride reactor with an adjustable feedback coefficient. According to the method, uranium hydrogen metal is adopted as reactor fuel, and metal hydride is adopted as a reactor moderator; different hydrogen content partitions are arranged in the radial direction of the reactor core by controlling the proportion of hydrogen and metal in the uranium hydrogen metal and the metal hydride, and the neutron leakage rate of the reactor core is adjusted by controlling the proportion of fuel and a moderator, so that the feedback coefficient of the reactor core is adjusted, and the reactivity control requirement of the reactor core is met. Furthermore, neutron flux distribution is optimized by setting different fuel enrichment degree partitions, and the total negative feedback coefficient of the reactor core is adjusted by matching with radial partitions with different hydrogen contents, so that the flattening of the radial power distribution of the reactor core in the whole life period is realized, the radial power peak factor of the reactor core is reduced, and the maneuverability and safety of the reactor core are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of reactor core technology, specifically a design method and core for a metal hydride reactor with adjustable feedback coefficient. Background Technology

[0002] During reactor operation, in order to operate stably under given power conditions and meet requirements such as emergency shutdown, power regulation, and compensation control, various forms of reactivity must be introduced. Determining the amount of reactivity to be introduced, the methods for efficient and safe control, and the allocation of reactivity among different control types are crucial aspects of nuclear reactor core design.

[0003] The core feedback coefficient refers to the change in core reactivity caused by a unit temperature change in the core. For a specific core, the coolant temperature change caused by core power increases or decreases is relatively constant. The larger the core feedback coefficient, the greater the reactivity change required to increase or decrease core power. However, the rate at which reactivity is introduced into the core is limited due to factors such as preventing instantaneous supercriticality. Therefore, the size of the core feedback coefficient affects the rate at which core power increases or decreases. In other words, the core feedback coefficient is related to the inertia of core state changes; the larger the core feedback coefficient, the less easily the core equilibrium state changes.

[0004] The feedback factor is a crucial indicator of reactor safety. To ensure reactor safety, a negative overall feedback factor is generally required. However, if the feedback factor is too low, the core power will also decrease. Therefore, reactor design requires a comprehensive consideration of both power and safety to determine an appropriate feedback factor. However, the core feedback factor is influenced by the feedback factors of the fuel, coolant, and moderator, which complicates core design.

[0005] Therefore, there is a need for a simple core design method that can control the reactor feedback coefficient. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a reactor core design method to at least achieve flexible adjustment of the instantaneous negative feedback coefficient of the core fuel and the total feedback coefficient of the core, while meeting the core reactivity control requirements and effectively improving the core mobility and safety.

[0007] The objective of this invention is achieved through the following technical solution: A design method for a metal hydride reactor with adjustable feedback coefficient, using uranium hydride metal as fuel and metal hydride as moderator; By controlling the ratio of hydrogen and metal in the uranium hydrogen metal and the metal hydride, different hydrogen content zones are set in the radial direction of the reactor core to control the feedback coefficient.

[0008] It is worth noting that in reactors containing metal hydrides, because the hydrogen atoms in the metal hydride are bound in the metal lattice, collisions between neutrons and hydrogen atoms will result in... Energy is exchanged quantically in integer multiples of eV. Neutrons with energies below 0.137 eV are difficult to further moderate in metallic hydrides, while still having a certain probability of gaining energies in integer multiples of 0.137 eV. As the core temperature increases, the proportion of hydrogen atoms in the excited state increases, increasing the probability of neutrons gaining energy in metallic hydrides and thus increasing the probability of neutron escape, resulting in a larger core feedback coefficient, i.e., the grid effect of metallic hydrides. For uranium-hydrogen metallic fuel, as the temperature increases, the probability of neutrons escaping the fuel increases, leading to increased core negative feedback; for metallic hydride moderators, as the temperature increases, the probability of neutrons escaping the moderator increases, leading to increased core positive feedback. Therefore, this invention adjusts core negative feedback based on the different characteristics of metallic hydride fuels and moderators, obtaining a suitable core negative feedback coefficient by directly controlling the hydrogen content parameter.

[0009] In some embodiments, the fuel and the moderator are selected from uranium zirconium hydride and zirconium hydride or uranium yttrium hydride and yttrium hydride, respectively.

[0010] In some examples, the stoichiometric ratio of H:Zr in the uranium hydride zirconium and zirconium hydride is 1.59-1.65:1.

[0011] For example, the stoichiometric ratio of H:Zr is 1.6:1.

[0012] In some embodiments, the stoichiometric ratio of H:Y in the uranium yttrium hydrogen and yttrium hydride is 1.7-2.2:1.

[0013] For example, the stoichiometric ratio of H:Y is 1.85:1.

[0014] In some embodiments, a lead-bismuth alloy is used as a coolant.

[0015] It is worth noting that the present invention uses a low-melting-point, high-boiling-point lead-bismuth alloy as a coolant, which can achieve a low core coolant inlet temperature, thereby reducing the maximum temperature of fuel and cladding. The primary circuit pressure adopts an atmospheric pressure design, which improves the core economy.

[0016] In some embodiments, different hydrogen content zones are provided radially in the core.

[0017] In some examples, the fuel enrichment partitioning is specifically: from the inside out radially, it consists of a low enrichment partition, a medium enrichment partition, and a high enrichment partition.

[0018] It is worth noting that by using radial partitioning of fuels with different enrichment levels and fuel-moderators with different hydrogen contents, it is possible to flatten the radial power distribution of the reactor core throughout its entire lifespan, reduce the radial power peak factor of the reactor core, and improve the core safety.

[0019] In some embodiments, different amounts of toxic substances are arranged according to different fuel enrichment levels in the fuel enrichment zone.

[0020] In some examples, the poison is erbium, a flammable poison.

[0021] It is worth noting that the erbium combustible poison is arranged in sections in the fuel and moderator of the reactor core, which can not only adjust the magnitude of negative feedback, but also control the residual reactivity of the reactor core and reduce the difficulty of control rod control.

[0022] In some embodiments, the core is specifically designed as follows: It includes several fuel assemblies, each fuel assembly comprising several fuel rods, several moderator rods, and several control rods; the control rods include one of a safety rod, a compensation rod, and a regulating rod; the fuel loaded in the fuel rods is uranium-hydrogen metal fuel; the moderator loaded in the moderators is a metal hydride; The uranium-hydrogen metal fuel includes uranium-hydrogen zirconium or uranium-hydrogen yttrium; The metal hydride includes zirconium hydride or yttrium hydride.

[0023] In some embodiments, three zones are provided radially along the reactor core, namely a central zone, an intermediate zone, and an outer zone; Each of the aforementioned zones is equipped with a fuel assembly containing different fuel rods and moderator rods; Each of the aforementioned partitions contains fuel assemblies with different fuel enrichment levels.

[0024] In some examples, the fuel enrichment in the central region is low, and the fuel loaded in the fuel rods is UYH. 1.85 (Indicating H:Y=1.85), the moderator loaded in the moderator rod is YH. 1.85 (This means H:Y = 1.85); The intermediate zone has a medium enrichment level of fuel, and the fuel loaded in the fuel rods is UZrH. 1.4 (Indicating H:Zr=1.4), the moderator loaded in the moderator rod is ZrH. 1.4 (This indicates that H:Zr=1.4); The outer region has a high fuel enrichment level, and the fuel loaded in the fuel rods is UZrH. 1.7 (Indicating H:Zr=1.7), the moderator loaded in the moderator rod is ZrH. 1.7 (This means H:Zr=1.7).

[0025] For example, the core design is as follows: The reactor core has a power output of 200 MWt and a lifespan of 1000 EFPD.

[0026] The reactor core comprises 68 assemblies: 13 low-enrichment fuel assemblies without control rods, 24 medium-enrichment fuel assemblies without control rods, 13 high-enrichment fuel assemblies without control rods, 6 medium-enrichment fuel assemblies with safety rods, and 12 medium-enrichment fuel assemblies with conditioning and compensation rods. The equivalent diameter of the active region is 181 cm, the active region height is 100 cm, the core height-to-diameter ratio is 0.55, and the core power density is 78 W / cm³. 3 The initial uranium loading at the beginning of the reactor core's lifespan is 2.19 tons, and the average burnup depth at the end of its lifespan is 91 GWd / tU.

[0027] Thirteen low-enrichment fuel assemblies without control rods are arranged in the core center region, while 24 medium-enrichment fuel assemblies without control rods and 13 high-enrichment fuel assemblies without control rods are arranged sequentially on the periphery. Six medium-enrichment fuel assemblies with safety rods are symmetrically distributed at the boundary between the low-enrichment and medium-enrichment fuel assemblies without control rods, and twelve medium-enrichment fuel assemblies with conditioning and compensating rods are symmetrically distributed at the boundary between the medium-enrichment and high-enrichment fuel assemblies without control rods. Each of the 18 control rod assemblies has a drive mechanism to control the raising or lowering of the control rod absorber into the core.

[0028] Dimensions of fuel rods and other components: Fuel rod core and moderator core radius 0.40cm, stainless steel cladding inner diameter 0.41cm, outer diameter 0.47cm, center distance between fuel rods and moderator rods 1.09cm, grid pitch to rod diameter ratio 1.16. Inner side-to-side distance of the component box 20.00cm, outer side-to-side distance 20.40cm, component center distance 20.60cm, control rod guide tube 7 outer side-to-side distance 6.5cm, inner radius 2.75cm.

[0029] Arrangement of each fuel assembly: Fuel assemblies without control rods consist of 10 fuel rod rings, totaling 271 cell positions. Fuel assemblies with control rods occupy 4 fuel rod rings, leaving 6 rings with a total of 234 cell positions. Low-enrichment fuel assemblies without control rods contain 238 fuel rods and 33 moderator rods; medium-enrichment fuel assemblies without control rods contain 214 fuel rods and 57 moderator rods; high-enrichment fuel assemblies without control rods contain 180 fuel rods and 91 moderator rods; and medium-enrichment fuel assemblies with safety rods and medium-enrichment fuel assemblies with regulating and compensating rods contain 186 fuel rods and 48 moderator rods.

[0030] The low-enrichment fuel assemblies without control rods and the medium-enrichment fuel assemblies without control rods contain 214 fuel rods and 57 moderator rods, the high-enrichment fuel assemblies without control rods contain 180 fuel rods and 91 moderator rods, and the medium-enrichment fuel assemblies with safety rods and the medium-enrichment fuel assemblies with regulating rods and compensating rods contain 186 fuel rods and 48 moderator rods.

[0031] The fuel assemblies within the reactor core are divided into three zones: the central zone contains low-enrichment fuel assemblies without control rods; the middle zone contains medium-enrichment fuel assemblies without control rods, medium-enrichment fuel assemblies with safety rods, and medium-enrichment fuel assemblies with conditioning and compensation rods; and the outer zone contains high-enrichment fuel assemblies without control rods. The fuel assemblies in these three zones, from the inside out, are equipped with UYH fuel. 1.85 、UZrH 1.4 and UZrH 1.7 The three fuel types have the following moderator rods in sequence: YH 1.85 ZrH 1.4 and ZrH 1.7 .

[0032] UYH is used inside the reactor core. 1.85 It has a stronger high-temperature hydrogen storage capacity and a larger hydrogen storage volume. Due to the strong neutron absorption of Y, the core power distribution is flattened by adjusting the increase of H content and enrichment. Moving outwards, the middle region uses UZrH... 1.4 Using Zr, which has better neutron economy, can save fuel consumption while ensuring hydrogen content. The outermost ring uses UZrH. 1.7 By increasing the H content, the neutron energy spectrum is further slowed down, reducing neutron leakage in the reactor core and improving the neutron economy of the reactor core.

[0033] By adjusting the fuel enrichment and combustible poison content, the core reactivity was made to meet the power and life requirements. At the same time, the core reactivity coefficient was evaluated, and the overall requirement of a negative feedback coefficient was met.

[0034] UYH inside the reactor core 1.85 The mass percentage of uranium in the medium is 35%, UZrH 1.4 and UZrH 1.7 The mass percentage of uranium in the fuel assembly is 30%. Core power distribution is flattened through radial fuel enrichment zoning and Er poison content zoning. The fuel enrichment of the high-enrichment fuel assembly without control rods is 27%, and the Er poison content is 2.0%; the fuel enrichment of the medium-enrichment fuel assembly without control rods, the medium-enrichment fuel assembly with safety rods, and the medium-enrichment fuel assembly with conditioning and compensation rods is 26%, and the Er poison content is 1.8%; the fuel enrichment of the low-enrichment fuel assembly without control rods is 24%, and the Er poison content is 1.5%.

[0035] Core rod lifting procedure: The core rod lifting procedure is to lift all safety rods. 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 requirements of the rise and fall power and the short-term reaction disturbance compensation.

[0036] The B4C B-10 content in the fuel assembly containing safety rods is 90%, and the B4C B-10 content in the fuel assembly containing compensating rods and adjustment rods is 40%. The total value of the 6 safety rods is 4412 pcm, and the total value of the 12 compensating and adjustment rods is 6793 pcm. The average value of a single bundle of compensating and adjustment rods is 722 pcm lower than the core's delayed neutron fraction. Meanwhile, the core reactivity control rods meet the design requirements for shutdown depth and sticking rods. The temperature coefficient of the core fuel at full power is 3.96 pcm / K, and the total negative feedback coefficient of the core is 4.68 pcm / K.

[0037] The beneficial effects of this invention are: 1) The design method of the present invention achieves the adjustment of the negative feedback coefficient in different regions by adjusting the hydrogen and metal content in the fuel and moderator.

[0038] 2) The design method of the present invention adjusts the neutron leakage rate of the reactor core by setting different hydrogen content partitions in the radial direction of the reactor core, thereby adjusting the total feedback coefficient of the reactor core. For example, when the hydrogen content inside the reactor core is set to be higher and the hydrogen content outside the reactor core is set to be lower, the neutron leakage rate increases and the negative feedback of the reactor core is relatively large; when the hydrogen content inside the reactor core is set to be lower and the hydrogen content outside the reactor core is set to be higher, the neutron leakage rate decreases and the negative feedback of the reactor core is relatively small.

[0039] 3) This invention optimizes the neutron flux distribution by setting different enrichment levels of fuel, and adjusts the total negative feedback coefficient of the core by radial partitioning with different hydrogen contents, thereby flattening the radial power distribution of the core throughout its lifespan, reducing the radial power peak factor of the core, and improving core safety. Attached Figure Description

[0040] Figure 1 These are schematic diagrams of the fuel rods in Embodiments 1 and 2 of the present invention; Figure 2 These are schematic diagrams of the safety bar in Embodiments 1 and 2 of the present invention; Figure 3 These are schematic diagrams of the compensation rod or adjusting rod in Embodiments 1 and 2 of the present invention; Figure 4 The diagram shows the structure of the moderating rod in Embodiments 1 and 2 of the present invention. Figure 5 These are schematic diagrams of the high-enrichment, control rod-free fuel assemblies in Embodiments 1 and 2 of the present invention. Figure 6 These are schematic diagrams of the enrichment-free fuel assembly without control rods in Embodiments 1 and 2 of the present invention. Figure 7 These are schematic diagrams of the low-enrichment, control rod-less fuel assemblies in Embodiments 1 and 2 of the present invention. Figure 8 This is a schematic diagram of the structure of the medium enrichment zone regulating rod compensating rod fuel assembly in Embodiments 1 and 2 of the present invention; Figure 9 These are schematic diagrams of the medium-enrichment fuel assembly with safety rods in Embodiments 1 and 2 of the present invention. Figure 10 This is a schematic diagram of the arrangement of the 200MWt reactor core in Embodiment 1 of the present invention; Figure 11 This is a schematic diagram of the arrangement of the 200MWt reactor core in Embodiment 2 of the present invention.

[0041] 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-weight tungsten, 9-moderator core, 51-fuel rod, 52-moderator rod, 53-assembly box, 54-compensator rod or regulating rod, 55-safety rod, 101-low enrichment fuel assembly a without control rod, 102-medium enrichment fuel assembly a without control rod, 103-high enrichment fuel assembly a without control rod, 104-medium enrichment fuel assembly a with safety rod, 105-medium enrichment fuel assembly a with regulating rod and compensator rod, 201-low enrichment fuel assembly b without control rod, 202-medium enrichment fuel assembly b without control rod, 203-high enrichment fuel assembly b without control rod; 204-medium enrichment fuel assembly b with safety rod, 205-medium enrichment fuel assembly b with regulating rod and compensator rod. Detailed Implementation

[0042] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0043] Example 1 Reference Figure 1-10 This embodiment provides a metal hydride reactor core with adjustable feedback coefficient, a core power of 200 MWt, and a lifespan of 1000 EFPD. Its specific structure is as follows: Reference Figure 10In this embodiment, the reactor core comprises 68 assemblies, including 13 low-enrichment fuel assemblies without control rods (a 101), 24 medium-enrichment fuel assemblies without control rods (a 102), 13 high-enrichment fuel assemblies without control rods (a 103), 6 medium-enrichment fuel assemblies with safety rods (a 104), and 12 medium-enrichment fuel assemblies with conditioning rods and compensation rods (a 105). The equivalent diameter of the active region is 181 cm, the height of the active region is 100 cm, the core height-to-diameter ratio is 0.55, the core power density is 78 W / cm³, the initial uranium loading at the end of the core's lifespan is 2.42 t, and the average burnup depth at the end of the core's lifespan is 83 GWd / tU.

[0044] Thirteen low-enrichment fuel assemblies (a 101) without control rods are arranged in the core center region; 24 medium-enrichment fuel assemblies (a 102) and 13 high-enrichment fuel assemblies (a 103) are arranged sequentially on the periphery; six medium-enrichment fuel assemblies (a 104) with safety rods are symmetrically distributed at the boundary between low-enrichment and medium-enrichment fuel assemblies (a 101) and medium-enrichment fuel assemblies (a 102); and twelve medium-enrichment fuel assemblies (a 105) with conditioning and compensating rods are symmetrically distributed at the boundary between medium-enrichment and high-enrichment fuel assemblies (a 102) and high-enrichment fuel assemblies (a 103). Each of the 18 control rod assemblies has a drive mechanism to control the raising or lowering of the control rod absorber into the core.

[0045] The distribution of hydrogen content across different zones is as follows: The fuel in the reactor core is all UZrH 1.6 (i.e., H:Zr=1.6:1), the mass percentage of uranium is 30%, that is, the total mass percentage of hydrogen and zirconium is 70%.

[0046] The distribution of fuel enrichment zones and Er toxicant content zones is as follows: The high-enrichment fuel assembly a 103 without control rods has a fuel enrichment of 28% and an Er toxic substance content of 2.0% by mass; the medium-enrichment fuel assembly a 102 without control rods, the medium-enrichment fuel assembly a 104 with safety rods, and the medium-enrichment fuel assembly a 105 with regulating and compensating rods have a fuel enrichment of 25% and an Er toxic substance content of 1.8% by mass; and the low-enrichment fuel assembly a 103 without control rods has a fuel enrichment of 23% and an Er toxic substance content of 1.5% by mass.

[0047] Reference Figure 1 and Figure 4The fuel rod core 1 and the moderator rod core 9 have a radius of 0.40 cm. The stainless steel cladding 3 has an inner diameter of 0.41 cm and an outer diameter of 0.47 cm. The center distance between the fuel rod 51 and the moderator rod 52 is 1.09 cm, and the grid pitch-to-diameter ratio is 1.16. The assembly box 53 has an inner side-to-side distance of 20.00 cm, an outer side-to-side distance of 20.40 cm, and an assembly center distance of 20.60 cm. The control rod guide tube 7 has an outer side-to-side distance of 6.5 cm and an inner radius of 2.75 cm.

[0048] Reference Figure 5-7 The fuel assembly without control rods has 10 fuel rod coils, totaling 271 cell positions. The fuel assembly with control rods occupies 4 fuel rod coils, leaving 6 coils with 234 cell positions. Low-enrichment fuel assembly a 101 without control rods contains 238 fuel rods 51 and 33 moderator rods 52; medium-enrichment fuel assembly a 102 without control rods contains 214 fuel rods 51 and 57 moderator rods 52; high-enrichment fuel assembly a 103 without control rods contains 180 fuel rods 51 and 91 moderator rods 52; medium-enrichment fuel assembly a 104 with safety rods and medium-enrichment fuel assembly a 105 with regulating and compensating rods contain 186 fuel rods 51 and 48 moderator rods 52.

[0049] Reference Figure 2-3 The core lifting procedure involves lifting all safety rods. The 12 compensating rods and regulating rods are symmetrically divided into two groups: compensating rods and regulating rods, with six 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 burnup reactivity loss, while the regulating rods do not need to compensate for the reactivity requirements of power rise and fall, or for short-term reaction disturbance compensation.

[0050] The B4C B-10 content in fuel assembly a104 (including safety rods) is 90%, and the B4C B-10 content in fuel assembly a105 (including compensator and regulator rods) is 40%. The total value of the six safety rods is 4376 pcm, and the total value of the twelve compensator and regulator rods is 6833 pcm. The average value of a single bundle of compensator and regulator rods is 722 pcm lower than the core's delayed neutron fraction. Meanwhile, the core reactivity control rods meet design requirements for shutdown depth and sticking rods. The temperature coefficient of the core fuel at full power is 2.12 pcm / K, and the total negative feedback coefficient of the core is 3.56 pcm / K.

[0051] Example 2 This embodiment provides a metal hydride reactor core with an adjustable feedback coefficient, a core power of 200 MWt, and a lifespan of 1000 EFPD. Its specific structure is as follows: refer to Figure 11In this embodiment, the reactor core comprises 68 assemblies, including 13 low-enrichment fuel assemblies without control rods (b 201), 24 medium-enrichment fuel assemblies without control rods (b 202), 13 high-enrichment fuel assemblies without control rods (b 203), 6 medium-enrichment fuel assemblies with safety rods (b 204), and 12 medium-enrichment fuel assemblies with conditioning rods and compensation rods (b 205). The equivalent diameter of the active region is 181 cm, the height of the active region is 100 cm, the core height-to-diameter ratio is 0.55, the core power density is 78 W / cm³, the initial uranium loading at the end of the core's lifespan is 2.19 t, and the average burnup depth at the end of the core's lifespan is 91 GWd / tU.

[0052] Thirteen low-enrichment fuel assemblies without control rods (b 201) are arranged in the core center region; 24 medium-enrichment fuel assemblies without control rods (b 202) and 13 high-enrichment fuel assemblies without control rods (b 203) are arranged sequentially on the periphery; six medium-enrichment fuel assemblies with safety rods (b 204) are symmetrically distributed at the boundary between low-enrichment and medium-enrichment fuel assemblies without control rods (b 201) and medium-enrichment fuel assemblies without control rods (b 202); and twelve medium-enrichment fuel assemblies with conditioning and compensating rods (b 205) are symmetrically distributed at the boundary between medium-enrichment and high-enrichment fuel assemblies without control rods (b 202) and high-enrichment fuel assemblies without control rods (b 203). Each of the 18 control rod assemblies has a drive mechanism to control the raising or lowering of the control rod absorber into the core.

[0053] In this embodiment, the dimensions of fuel rod 51 and other components are the same as in Embodiment 1. The component structure types within the core are all the same as in Embodiment 1 (i.e., the structure of all fuel assemblies b is the same as the corresponding fuel assembly a), except that the low-enrichment fuel assembly b 201 without control rods is replaced with the same structure type as the medium-enrichment fuel assembly b 202 without control rods, and the only difference between the two is the fuel.

[0054] Fuel assemblies without control rods 201, 202 and 203 have 10 fuel rod rings, totaling 271 cell positions. Fuel assemblies with control rods 204 and 205 have control rods occupying 4 fuel rod rings, leaving 6 rings, totaling 234 cell positions.

[0055] Low-enrichment fuel assembly b 201 and medium-enrichment fuel assembly b 202 contain 214 fuel rods 51 and 57 moderator rods 52; high-enrichment fuel assembly b 203 contains 180 fuel rods 51 and 91 moderator rods 52; medium-enrichment fuel assembly b 204 with safety rod and medium-enrichment fuel assembly b 205 with regulating and compensating rod contain 186 fuel rods 51 and 48 moderator rods 52.

[0056] The fuel assemblies within the reactor core are divided into three zones: the central zone contains low-enrichment fuel assembly b 201 without control rods; the middle zone contains medium-enrichment fuel assemblies b 202, b 204 (with safety rods), and b 205 (with conditioning and compensation rods); and the outer zone contains high-enrichment fuel assembly b 203 without control rods. The fuel assemblies in the three zones, from the inside out, are equipped with UYH fuel. 1.85 、UZrH 1.4 and UZrH 1.7 The three fuel types have the following moderator rods in sequence: YH 1.85 ZrH 1.4 and ZrH 1.7 .

[0057] UYH is used inside the reactor core. 1.85 It has a stronger high-temperature hydrogen storage capacity and a larger hydrogen storage volume. Due to the strong neutron absorption of Y, the core power distribution can be flattened by adjusting the increase of H content and enrichment. Moving outwards, the middle region uses UZrH... 1.4 Using Zr, which has better neutron economy, can save fuel consumption while ensuring hydrogen content. The outermost ring uses UZrH. 1.7 By increasing the H content, the neutron energy spectrum is further slowed down, reducing neutron leakage in the reactor core and improving the neutron economy of the reactor core.

[0058] By adjusting the fuel enrichment and combustible poison content, the core reactivity was made to meet the power and life requirements. At the same time, the core reactivity coefficient was evaluated, and the overall requirement of a negative feedback coefficient was met.

[0059] UYH inside the reactor core 1.85 The mass percentage of uranium in the medium is 35%, UZrH 1.4 and UZrH 1.7 The mass percentage of uranium in the fuel assembly is 30%. Core power distribution is flattened through radial fuel enrichment zoning and Er poison content zoning. The high-enrichment fuel assembly b203 (without control rods) has a fuel enrichment of 27% and an Er poison mass content of 2.0%; the medium-enrichment fuel assemblies b202 (without control rods), b204 (with safety rods), and b205 (with conditioning and compensating rods) have a fuel enrichment of 26% and an Er poison mass content of 1.8%; and the low-enrichment fuel assembly b201 (without control rods) has a fuel enrichment of 24% and an Er poison mass content of 1.5%.

[0060] The B4C B-10 content in fuel assembly b 204 (containing safety rods) is 90%, and the B4C B-10 content in fuel assembly 205 (containing compensating and regulating rods) is 40%. The total value of the six safety rods is 4412 pcm, and the total value of the twelve compensating and regulating rods is 6793 pcm. The average value of a single bundle of compensating and regulating rods is 722 pcm lower than the core's delayed neutron fraction. Meanwhile, the core reactivity control rods meet design requirements for shutdown depth and sticking rods. The temperature coefficient of the core fuel at full power is 3.96 pcm / K, and the total negative feedback coefficient of the core is 4.68 pcm / K.

[0061] The core lifting procedure is the same as in Example 1.

[0062] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A design method for a metal hydride reactor with adjustable feedback coefficient, characterized in that, include: Uranium hydrogen metal is used as fuel, and metal hydrides are used as moderators; By controlling the ratio of hydrogen and metal in the uranium hydrogen metal and the metal hydride, different hydrogen content zones are set in the radial direction of the reactor core to control the feedback coefficient.

2. The design method according to claim 1, characterized in that: In each of the hydrogen content zones, the combination of fuel and moderator is selected from one of uranium zirconium hydride and zirconium hydride, and uranium yttrium hydride and yttrium hydride.

3. The design method according to claim 2, characterized in that: The stoichiometric ratio of H:Zr in the uranium-zirconium hydrogen and zirconium hydride is 1.59-1.65:

1.

4. The design method according to claim 2, characterized in that: The stoichiometric ratio of H to Y in the uranium yttrium hydrogen and yttrium hydride is 1.7-2.2:

1.

5. The design method according to any one of claims 1, characterized in that: A lead-bismuth alloy is used as the coolant.

6. The design method according to claim 1, characterized in that: Fuel enrichment zones are set radially in the reactor core, with different fuel enrichment levels.

7. The design method according to claim 6, characterized in that: Poison zones are set up radially in the reactor core, with different concentrations of poisons placed there.

8. A metal hydride reactor core with adjustable feedback coefficient, designed by the design method according to any one of claims 1-8, characterized in that: It includes several fuel assemblies, each fuel assembly comprising several fuel rods, several moderator rods, and several control rods; the control rods include at least one of a safety rod, a compensation rod, and a regulating rod; the fuel loaded in the fuel rods is uranium-hydrogen metal fuel; the moderator loaded in the moderators is a metal hydride; The uranium-hydrogen metal fuel includes uranium-hydrogen zirconium or uranium-hydrogen yttrium; The metal hydride includes zirconium hydride or yttrium hydride.

9. The metal hydride reactor core according to claim 8, characterized in that: The reactor core is divided into three zones along its radial direction: a central zone, an intermediate zone, and an outer zone. Each of the aforementioned zones is equipped with a fuel assembly containing different fuel rods and moderator rods; Each of the aforementioned partitions contains fuel assemblies with different fuel enrichment levels.

10. The metal hydride reactor core according to claim 9, characterized in that: The central region has a low fuel enrichment level, and the fuel loaded in the fuel rods is UYH. 1.85 The moderator loaded in the moderator rod is YH 1.85 ; The intermediate zone has a medium enrichment level of fuel, and the fuel loaded in the fuel rods is UZrH. 1.4 The moderator loaded in the moderator rod is ZrH 1.4 ; The outer region has a high fuel enrichment level, and the fuel loaded in the fuel rods is UZrH. 1.7 The moderator loaded in the moderator rod is ZrH 1.7 .

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