Reactor core adopting combination application of different hydrides
By introducing a combination of zirconium hydride and yttrium hydride fuel rods into a moderator-free reactor core, the problems of neutron energy spectrum and power distribution in the core were solved, resulting in a higher fission reaction rate and a lower critical mass, thus enhancing the safety and lifespan of the reactor core.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-03-13
AI Technical Summary
How to design a lead-bismuth power reactor core with metal hydride fuel to achieve a moderated core neutron energy spectrum, improve the core fission reaction rate, reduce the core critical mass, and achieve a better flattened core power distribution.
The reactor core design employs different hydride combinations. By introducing metallic hydride fuel rods into the unmoderate core and utilizing the combination of zirconium hydride and yttrium hydride, the equivalent nucleon density of uranium and hydrogen in different regions of the core can be adjusted, thereby achieving softening of the core energy spectrum and flattening of the power distribution.
It improves the core fission reaction rate, reduces the core critical mass, enhances core safety and power distribution uniformity, avoids local overheating, and extends core lifespan.
Smart Images
Figure CN121662439A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nuclear reactor core technology, and more specifically, to a reactor core employing different combinations of hydrides. Background Technology
[0002] The core characteristic of metal hydride fuels (such as zirconium uranium hydride and yttrium uranium hydride) is the inherent moderator hydrogen atoms within the fuel. This characteristic not only determines their unique safety performance but also gives rise to advantages in thermal performance, fuel consumption, and other aspects, as detailed below: (1) Inherent slowing ability and inherent safety In metallic hydride fuels, hydrogen atoms are bound within a zirconium (or yttrium) lattice. When fast neutrons collide with hydrogen nuclei in the reactor core, they... Neutrons exchange energy in quantized forms that are integer multiples of eV, thus being effectively thermalized. Neutrons with energies below 0.137 eV are difficult to deeply moderate with zirconium hydride, except for further thermalization in other types of moderators in the reactor core. At the same time, neutrons in zirconium hydride may also gain energy from stimulated oscillators through scattering, and the number of stimulated oscillators in the lattice increases with increasing fuel temperature.
[0003] When a sudden surge in reactor power leads to a momentary increase in fuel temperature, the proportion of hydrogen atoms in a highly excited state increases simultaneously, significantly raising the probability of neutrons gaining energy through collisions with hydrogen nuclei. On one hand, the increased energy of neutrons increases their chance of escaping from the fuel, resulting in more neutrons being absorbed outside the fuel rods. This reduces the ratio of neutron absorption within the fuel to total absorption in the cells, directly leading to a decrease in core reactivity. On the other hand, the hardening of the neutron spectrum enhances U-238 resonance absorption and increases core neutron leakage, further reinforcing the transient negative temperature coefficient. In summary, metallic hydride fuels possess unique transient negative reactivity, endowing the reactor core with extremely strong inherent safety and effectively suppressing abnormal power fluctuations.
[0004] (2) High thermal conductivity, suitable for high power density scenarios Metal hydride fuels exhibit significantly higher thermal conductivity than traditional oxide fuels. The thermal conductivity of zirconium hydride and yttrium hydride fuels is 2 to 6 times that of uranium dioxide. This higher thermal conductivity allows for rapid heat dissipation from the fuel's interior, drastically reducing the core temperature of the fuel rods. Data from boiling water reactor studies show that, under the same pressure drop and maximum linear power density, oxide fuels can reach a maximum temperature of around 2000°C, while metal hydride fuels only reach about 500°C. This advantage means that metal hydride fuels can maintain a power density comparable to oxide fuels while avoiding overheating failure, thus possessing core potential as fuels for high-power-density power reactors.
[0005] (3) High unloading burnup extends core life. Another key characteristic of metal hydride fuels is that even under high burnup irradiation, the fission gas release rate is very low, resulting in high unloading burnup and thus a relatively long core lifespan. (Romania UZrH) 1.6 The core power density of the reactor is 139 W / cm³. 3 The unloading burnup is 120 GWd / tU, which is higher in power density and deeper in burnup than traditional pressurized water reactors. For example, the core power density of the Daya Bay PWR is 107 W / cm³. 3 The fuel consumption during unloading is 52GWd / tU.
[0006] In summary, metal hydride fuels possess inherent advantages such as safety, high thermal conductivity, high burnup during unloading, and long core lifespan, making them promising for applications. The key to core design for this type of fuel lies in how to design lead-bismuth power reactor cores using metal hydride fuels, achieve a moderated core neutron energy spectrum, improve the core fission reaction rate, reduce the core critical mass, and achieve a better flattened core power distribution. Summary of the Invention
[0007] To address the aforementioned shortcomings in the existing technology, the core objective of this invention is to provide a reactor core employing a combination of different hydrides. By introducing metallic hydride fuel rods into a core without a moderator, the neutron energy spectrum of the core is moderated, the core fission reaction rate is increased, and the core critical mass is reduced. Simultaneously, by using a combination of different hydride types, the equivalent nucleon density of uranium and hydrogen in different regions of the core is adjusted, further flattening the core power distribution.
[0008] This invention is achieved through the following technical solution: A reactor core employing different hydride combinations includes several fuel assemblies arranged radially from the center to the periphery; some of the fuel assemblies simultaneously include uranium zirconium hydride fuel rods filled with uranium zirconium hydride fuel and uranium yttrium hydride fuel rods filled with uranium yttrium hydride fuel.
[0009] This invention utilizes metal hydride fuel rods in a moderator-free reactor core to achieve ultrathermal or thermal core design. By softening the core energy spectrum, it increases the core fission reaction rate and reduces the core critical mass. Simultaneously, it allows the core to use combustible poisons, as found in conventional pressurized water reactors, to assist in controlling the core's residual reactivity.
[0010] Metal hydride fuels include yttrium uranium hydride and zirconium uranium hydride. Yttrium uranium hydride has a higher hydrogen release temperature than zirconium uranium hydride. Yttrium uranium hydride begins to release hydrogen at around 850℃, while zirconium uranium hydride begins to release hydrogen at 650℃. The increased hydrogen release temperature can greatly expand the application range of metal hydride fuels and enable them to maintain good moderation performance at high temperatures. Compared with yttrium uranium hydride, zirconium uranium hydride has a higher fuel density. For the same uranium mass percentage, zirconium uranium hydride has a higher uranium load and hydrogen load. At the same time, yttrium has a larger neutron absorption cross section in the thermal spectrum than zirconium. Therefore, zirconium uranium hydride has better moderation performance, uranium load, and neutron economy than yttrium uranium hydride.
[0011] Therefore, this invention achieves a non-uniform hydrogen content distribution in the reactor core by using a combination of different types of metal hydride fuels. Zirconium uranium hydride has a higher hydrogen nucleon density, better moderation performance, and better neutron economy, while yttrium uranium hydride has a relatively lower hydrogen nucleon density, slightly worse moderation performance, and poorer neutron economy due to yttrium's neutron absorption. The combination of these two fuels can achieve equivalent uranium and hydrogen nucleon densities in different regions, further flattening the core power distribution.
[0012] Preferably, the fuel assemblies distributed radially from the center to the periphery include low-enrichment fuel assemblies, medium-enrichment fuel assemblies, and high-enrichment fuel assemblies; preferably, the fuel enrichment of the low-enrichment fuel assemblies is 27%~29%; the fuel enrichment of the medium-enrichment fuel assemblies is 29%~31%; and the fuel enrichment of the high-enrichment fuel assemblies is 31%~33%.
[0013] The low-enrichment fuel assembly includes yttrium uranium hydride fuel rods; the medium-enrichment fuel assembly includes both zirconium uranium hydride fuel rods and yttrium uranium hydride fuel rods; and the high-enrichment fuel assembly includes both zirconium uranium hydride fuel rods and yttrium uranium hydride fuel rods.
[0014] Preferably, both the medium-enrichment fuel assembly and the high-enrichment fuel assembly are axially segmented fuel assemblies, which are arranged axially in segments with zirconium hydride fuel rods and yttrium hydride fuel rods; the low-enrichment fuel assembly is an axially unsegmented fuel assembly.
[0015] By placing uranium zirconium hydride in areas with high power requirements and uranium yttrium hydride in areas with low power requirements, excessive local energy is avoided. At the same time, radial and axial power distribution and burnup distribution are flattened by using fuel enrichment zoning and uranium mass percentage zoning in conjunction with different hydride combinations.
[0016] Preferably, the stoichiometric ratio of hydrogen to zirconium in the uranium hydride fuel is selected from 1.2 to 1.9, preferably UZrH 1.6The stoichiometric ratio of hydrogen to yttrium in the uranium hydride is selected from 1.5 to 2.1, preferably UYH. 1.85 .
[0017] Different hydride fuels can achieve different hydrogen permeation ratios. Although different metal hydrides have the most stable hydrogen content, the hydrogen content can be adjusted as needed to achieve the zonal arrangement of different metal hydride fuels and different hydrogen contents in different fuel rods and different components.
[0018] Preferably, the axially segmented zirconium hydride fuel rods and yttrium hydride fuel rods in the medium-enrichment fuel assembly, as well as the axially segmented zirconium hydride fuel rods and yttrium hydride fuel rods in the high-enrichment fuel assembly, are coated with a pyrolytic carbon coating or a graphite coating. The thickness of the pyrolytic carbon coating and the graphite coating is preferably 5-20 μm, to achieve sealing and partitioned arrangement for different hydrogen contents.
[0019] Preferably, both the zirconium hydride fuel rod and the yttrium hydride fuel rod comprise a fuel core, helium gas, and a stainless steel cladding; the ratio of the radius of the fuel core to the thickness of the stainless steel cladding satisfies a ratio of 9 to 10:1. The fuel rods employ a thick rod and thin cladding design to increase the moderation capability of hydrogen atoms in the fuel rod and reduce the neutron absorption effect of the cladding and other structural materials.
[0020] Preferably, the fuel assembly further includes a moderator rod; the moderator rod includes a zirconium hydride moderator rod and / or a yttrium hydride moderator rod.
[0021] Introducing metal hydride moderators into a moderatorless reactor core can also achieve hyperthermal or thermal core designs. By softening the core energy spectrum, the core fission reaction rate can be increased, and the core critical mass can be reduced. Combining different types of metal hydride moderators can achieve a non-uniform hydrogen content distribution in the core. Zirconium hydride moderators are placed in locations requiring relatively higher power, while yttrium hydride moderators are placed in locations requiring relatively lower power. Furthermore, using different types of metal hydride fuels and moderators in combination can achieve a non-uniform distribution of different hydrogen contents in the core. Metal hydride moderators assist metal hydride fuels in further softening the neutron energy spectrum, which can be used to adjust the equivalent nucleon density of uranium and hydrogen in the core to meet power density and lifetime requirements. Similarly, the hydrogen infiltration ratio of the hydride moderator can also be adjusted to appropriately adjust the hydrogen content.
[0022] Preferably, some of the fuel assemblies also include control rods, which include safety rods, regulating rods, and compensating rods. The fuel assemblies can be further categorized into fuel assemblies without control rods, fuel assemblies with regulating rods, fuel assemblies with safety rods, and fuel assemblies with compensating rods. Furthermore, combining fuel enrichment and the presence or absence of control rods, fuel assemblies can be categorized into: low-enrichment fuel assemblies with safety rods, low-enrichment fuel assemblies without control rods, medium-enrichment fuel assemblies with safety rods, medium-enrichment fuel assemblies with regulating rods, medium-enrichment fuel assemblies without control rods, medium-enrichment fuel assemblies with compensating rods, and high-enrichment fuel assemblies without control rods.
[0023] Preferably, the guide tube of the safety rod adopts a dry channel design, and the control rod absorber adopts a solid absorber rod design to ensure that the control rod absorber can fall freely to meet the emergency shutdown requirements under accident conditions.
[0024] Preferably, the regulating rod and the compensating rod are designed with coolant channels, and the control rod absorber is designed with a central counterweight and an outer layer of absorber material to improve the equivalent density of the control rod absorber and reduce the driving pressure of the control rod drive mechanism.
[0025] Preferably, the reactor core can use traditional solid combustible poison materials from pressurized water reactors to help control the residual reactivity of the core. Combustible poisons include boron carbide, gadolinium oxide, erbium oxide, etc.
[0026] More preferably, the core is arranged as follows: low-enrichment fuel assemblies with safety rods are located in the central region of the core; low-enrichment fuel assemblies without control rods are symmetrically and uniformly arranged around the low-enrichment fuel assemblies with safety rods; medium-enrichment fuel assemblies with safety rods and medium-enrichment fuel assemblies with regulating rods are dispersed and symmetrically arranged around the low-enrichment fuel assemblies without control rods; medium-enrichment fuel assemblies without control rods are arranged in the central region of the core; and medium-enrichment fuel assemblies with compensating rods and high-enrichment fuel assemblies without control rods are sequentially and symmetrically arranged around the core.
[0027] Preferably, the control rod-less fuel assembly of the present invention includes a fuel rod, an assembly box, and lead-bismuth; the regulating rod fuel assembly of the present invention includes a fuel rod, a regulating rod, an assembly box, and lead-bismuth; the safety rod fuel assembly of the present invention includes a fuel rod, a safety rod, an assembly box, and lead-bismuth; the compensation rod fuel assembly of the present invention includes a fuel rod, a compensation rod, an assembly box, and lead-bismuth.
[0028] Preferably, in the fuel assembly containing a control rod (adjusting rod / compensation rod / safety rod) of the present invention, the control rod (adjusting rod / compensation rod / safety rod) is located at the center of the fuel assembly, and fuel rods are uniformly arranged on the outer periphery of the control rod (adjusting rod / compensation rod / safety rod).
[0029] Preferably, the fuel rod of the present invention comprises, from the inside out, a fuel core, helium, a stainless steel cladding, and lead-bismuth; the safety rod of the present invention comprises, from the inside out, a B4C core, helium, a stainless steel cladding, air, a control rod guide tube, and lead-bismuth; the compensation rod of the present invention comprises, from the inside out, a counterweight tungsten, helium, a stainless steel cladding, helium, a B4C core, helium, a stainless steel cladding, lead-bismuth, a control rod guide tube, and lead-bismuth; the adjustment rod of the present invention comprises, from the inside out, a counterweight tungsten, helium, a stainless steel cladding, helium, a B4C core, helium, a stainless steel cladding, lead-bismuth, a control rod guide tube, and lead-bismuth.
[0030] Preferably, the fuel assemblies of the present invention are divided into two categories: axially unsegmented fuel assemblies and axially segmented fuel assemblies. The axially unsegmented fuel assembly includes: yttrium uranium hydride fuel rods, an assembly box, and lead bismuth. The axially segmented fuel assembly includes: yttrium uranium hydride fuel rods, zirconium uranium hydride fuel rods, an assembly box, and lead bismuth.
[0031] In one embodiment, the core is specifically designed as follows: The core power is 100MWt, and the lifespan is 1000EFPD.
[0032] The reactor core contains 85 fuel assemblies: 12 low-enrichment fuel assemblies without control rods, 1 low-enrichment fuel assembly with safety rods, 3 medium-enrichment fuel assemblies with safety rods, 3 medium-enrichment fuel assemblies with conditioning rods, 24 medium-enrichment fuel assemblies without control rods, 12 medium-enrichment fuel assemblies with compensating rods, and 30 high-enrichment fuel assemblies without control rods. The equivalent diameter of the active region is 144 cm, the height of the active region is 100 cm, the core height-to-diameter ratio is 0.69, and the core power density is 61 W / cm³. 3 The initial uranium loading at the beginning of the reactor core's lifespan is 2.43 tons, and the average burnup depth at the end of its lifespan is 41 GWd / tU.
[0033] One low-enrichment fuel assembly with a safety rod is located in the central region of the core. Twelve low-enrichment fuel assemblies without control rods are symmetrically and evenly arranged around the low-enrichment fuel assemblies with safety rods. Three medium-enrichment fuel assemblies with safety rods and three medium-enrichment fuel assemblies with conditioning rods are dispersed and symmetrically arranged around the 12 low-enrichment fuel assemblies without control rods. Twenty-four medium-enrichment fuel assemblies without control rods are arranged in the central region of the core. Twelve medium-enrichment fuel assemblies with compensation rods and thirty high-enrichment fuel assemblies without control rods are arranged symmetrically around the core.
[0034] All control rods in the reactor core are divided into safety rod groups S1~S4, regulating rod groups P1~P3, and compensation rod groups B1~B12. Each group of control rods is controlled by a drive mechanism to raise or insert the control rod absorber into the reactor core.
[0035] The fuel rod core has a radius of 0.50 cm, a stainless steel cladding with an inner diameter of 0.51 cm and an outer diameter of 0.57 cm, a fuel rod center-to-center distance of 1.276 cm, and a grid pitch-to-rod diameter ratio of 1.16. Each fuel assembly contains 7 fuel rod coils, with control rods occupying 4 coils. Fuel assemblies without control rods contain 127 fuel rods, while those with control rods contain 90 fuel rods. The assembly box has an inner side-to-side distance of 14.54 cm, an outer side-to-side distance of 14.94 cm, an assembly center-to-center distance of 15.14 cm, and a control rod guide tube with an outer side-to-side distance of 7.56 cm and an inner radius of 3.22 cm.
[0036] The fuel in the reactor core is UZrH 1.6 and UYH 1.85 The fuel assemblies are divided radially by fuel enrichment level, and some assemblies are divided axially by fuel type. The high-enrichment fuel assemblies have a fuel enrichment level of 32%; the medium-enrichment fuel assemblies have a fuel enrichment level of 30%; and the low-enrichment fuel assemblies have a fuel enrichment level of 28%. The low-enrichment fuel assemblies are not segmented axially, and the fuel rod type is yttrium uranium hydride fuel rods, filled with UYH fuel. 1.85 Both medium-enrichment and high-enrichment fuel assemblies employ an axially segmented fuel type design, with the upper half of the assembly filled with UYH fuel. 1.85 The fuel consists of yttrium uranium hydride fuel rods, with the lower half filled with UZrH. 1.6 Zirconium hydride fuel rods for fuel.
[0037] The B4C B-10 content in the four medium-enriched fuel assemblies containing safety rods is 90%, the B4C B-10 content in the three medium-enriched fuel assemblies containing conditioning rods is 40%, and the B4C B-10 content in the twelve medium-enriched fuel assemblies containing compensation rods is 60%. The total value of the safety rods is 5560 pcm, the value of the three conditioning rods is 2155 pcm, and the total value of the twelve compensation rods is 12553 pcm. The core reactivity control rods meet the design requirements for shutdown depth and sticking rods.
[0038] The core lifting procedure is as follows: safety rods are fully lifted, control rods are raised to half the core height, and compensating rods are raised to core criticality. During burnup, compensating rods are raised to compensate for burnup reactivity loss. Control rods do not need to compensate for the reactivity demand of power rise and fall or for short-term reaction disturbance compensation.
[0039] The present invention has at least the following advantages and beneficial effects: (1) This invention introduces a metal hydride fuel rod design into a core without a moderator to moderate the neutron energy spectrum of the core, improve the core fission reaction rate, reduce the core critical mass, and at the same time enable the core to use combustible poisons in conventional pressurized water reactors to help control the core's residual reactivity. More importantly, this invention uses a combination of different hydride types to adjust the equivalent nucleon density of uranium and hydrogen in different regions of the core, further flattening the core power distribution, avoiding local overheating, and improving core safety.
[0040] (2) The present invention achieves radial and axial power distribution flattening and burnup distribution flattening by using fuel enrichment partitioning in the core radially in combination with different hydride combinations in the axial direction. Attached Figure Description
[0041] Figure 1 This is a schematic diagram of the fuel rod structure in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the structure of the safety bar in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the structure of the adjusting rod and the compensating rod in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the structure of the control rod-less fuel assembly in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the structure of the fuel assembly containing the safety rod in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the structure of the fuel assembly with regulating rod in Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the fuel assembly with compensation rods in Embodiment 1 of the present invention; Figure 8 This is a schematic diagram of the axially segmented fuel assembly in Embodiment 1 of the present invention; Figure 9 This is a schematic diagram of the axially segmented fuel assembly in Embodiment 1 of the present invention; Figure 10 This is a schematic diagram of the 100MWt reactor core arrangement structure in Embodiment 1 of the present invention.
[0042] Figure label: 1-Fuel core, 2-Helium, 3-Stainless steel cladding, 4-Lead bismuth, 5-B4C core, 6-Air, 7-Control rod guide tube, 8-Counterweight tungsten, 51-Fuel rod, 52-Assembly box, 53-Compensation rod, 54-Safety rod, 55-Yttrium uranium hydride fuel rod, 56-Zirconium uranium hydride fuel rod, 57-Regulating rod, 101-Low enrichment fuel assembly without control rod, 102-Low enrichment fuel assembly with safety rod, 103-Medium enrichment fuel assembly with safety rod, 104-Medium enrichment fuel assembly with regulating rod, 105-Medium enrichment fuel assembly without control rod, 106-Medium enrichment fuel assembly with compensation rod, 107-High enrichment fuel assembly without control rod. Detailed Implementation
[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the present invention will be further described below in conjunction with specific embodiments. All features disclosed in this specification, except for mutually exclusive features and / or steps, can be combined in any way.
[0044] The following embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way.
[0045] Example 1 As attached Figure 1 - Appendix Figure 10 As shown, this embodiment provides a reactor core using different combinations of hydrides, with the specific design as follows: The core power is 100MWt, and the lifespan is 1000EFPD.
[0046] For details, see attached. Figure 10 As shown, the reactor core contains 85 fuel assemblies: 12 low-enrichment fuel assemblies without control rods (101), 1 low-enrichment fuel assembly with safety rods (102), 3 medium-enrichment fuel assemblies with safety rods (103), 3 medium-enrichment fuel assemblies with conditioning rods (104), 24 medium-enrichment fuel assemblies without control rods (105), 12 medium-enrichment fuel assemblies with compensating rods (106), and 30 high-enrichment fuel assemblies without control rods (107). The equivalent diameter of the active zone is 144 cm, the height of the active zone is 100 cm, the core height-to-diameter ratio is 0.69, the core power density is 61 W / cm³, the initial uranium loading at the end of the core's life is 2.43 t, and the average burnup depth at the end of the core's life is 41 GWd / tU.
[0047] Further details are attached. Figure 10As shown, one low-enrichment fuel assembly with safety rods 102 is located in the central region of the reactor core. Twelve low-enrichment fuel assemblies without control rods 101 are symmetrically and evenly arranged around the low-enrichment fuel assembly with safety rods 102. Three medium-enrichment fuel assemblies with safety rods 103 and three medium-enrichment fuel assemblies with regulating rods 104 are dispersed and symmetrically arranged around the 12 low-enrichment fuel assemblies without control rods 101. Twenty-four medium-enrichment fuel assemblies without control rods 105 are arranged in the central region of the reactor core. Twelve medium-enrichment fuel assemblies with compensating rods 106 and thirty high-enrichment fuel assemblies without control rods 107 are arranged symmetrically around the reactor core.
[0048] All control rods in the reactor core are divided into safety rod groups S1~S4, regulating rod groups P1~P3, and compensation rod groups B1~B12. Each group of control rods is controlled by a drive mechanism to raise or insert the control rod absorber into the reactor core.
[0049] The fuel rod 51 has a core radius of 0.50 cm, an inner diameter of 0.51 cm and an outer diameter of 0.57 cm for the stainless steel cladding 3, a center-to-center distance of 1.276 cm, and a grid pitch-to-rod diameter ratio of 1.16. Each fuel assembly contains 7 coils of fuel rods 51, with the control rod occupying 4 coils. Fuel assemblies without control rods contain 127 fuel rods 51, while those with control rods contain 90 fuel rods 51. The assembly box 52 has an inner side-to-side distance of 14.54 cm, an outer side-to-side distance of 14.94 cm, and a center-to-center distance of 15.14 cm. The control rod guide tube 7 has an outer side-to-side distance of 7.56 cm and an inner radius of 3.22 cm.
[0050] The fuel in the reactor core is UZrH 1.6 and UYH 1.85 The fuel assemblies are zoned radially by fuel enrichment and axially by fuel type for some assemblies. The fuel enrichment of high-enrichment fuel assemblies is 32%; that of medium-enrichment fuel assemblies is 30%; and that of low-enrichment fuel assemblies is 28%.
[0051] The low-enrichment fuel assembly is an axially unsegmented fuel assembly, with fuel rod 51 being a yttrium uranium hydride fuel rod 55, and the fuel being UYH. 1.85 Both medium-enrichment and high-enrichment fuel assemblies employ axially segmented fuel assemblies, with the upper half of the assembly filled with UYH. 1.85 The fuel rod 55 is made of uranium hydride yttrium fuel rod, with the lower half filled with UZrH. 1.6 56. Fuel rods of uranium hydride zirconium hydride.
[0052] The axial spaces between the zirconium hydride fuel rod 56 and the yttrium hydride fuel rod 55 in the medium-enrichment fuel assembly, and between the zirconium hydride fuel rod 56 and the yttrium hydride fuel rod 55 in the high-enrichment fuel assembly, are all coated with a pyrolytic carbon coating with a thickness of 10 μm (not shown in the figure).
[0053] For details, see attached. Figure 1 As shown, in this embodiment, the fuel rod 51 consists of, from the inside out, a fuel core 1, helium gas 2, a stainless steel cladding 3, and lead-bismuth 4. (See attached diagram) Figure 2 As shown, the safety rod 54 in this embodiment includes, from the inside out, a B4C core 5, helium gas 2, a stainless steel shell 3, air 6, a control rod guide tube 7, and lead-bismuth 4; the structures of the adjusting rod 57 and the compensating rod 53 in this embodiment are as shown in the attached figure. Figure 3 As shown, the structure includes, from the inside out, a counterweight tungsten 8, helium 2, a stainless steel cladding 3, helium 2, a B4C core 5, helium 2, a stainless steel cladding 3, lead-bismuth 4, a control rod guide tube 7, and lead-bismuth 4. The difference between the adjusting rod 57 and the compensating rod 53 is that the B4C content in the B4C core 5 is different.
[0054] A schematic diagram of the control rodless fuel assembly in this embodiment is attached. Figure 4 As shown, in the control rod-less fuel assembly, fuel rod 51 is assembled in assembly box 52 and loaded in lead-bismuth 4 alloy; the structural schematic diagram of the fuel assembly with safety rod in this embodiment is shown below. Figure 5 As shown, in the fuel assembly with safety rods, safety rod 54 is arranged at the center of the fuel assembly, and fuel rods 51 are evenly arranged on the outer periphery, and finally mixed and assembled in the assembly box 52, loaded in lead-bismuth 4 alloy; the schematic diagram of the fuel assembly with regulating rods in this embodiment is shown below. Figure 6 As shown, a schematic diagram of the fuel assembly containing the compensation rod is as follows: Figure 7 As shown, both have the same structure, with the regulating rod 57 or the compensating rod 53 arranged in the center of the fuel assembly, the fuel rods 51 evenly arranged on the outer periphery, and finally assembled in the assembly box 52, loaded in lead-bismuth 4 alloy.
[0055] As attached Figure 8 As shown, in this embodiment, the axially non-segmented fuel assembly has yttrium uranium hydride fuel rods 55 arranged axially and uniformly; as shown in the attached figure. Figure 9 As shown, the axial segmented fuel assembly in this embodiment is arranged in upper and lower segments, with yttrium uranium hydride fuel rods 55 arranged in the upper segment and zirconium uranium hydride fuel rods 56 arranged in the lower segment.
[0056] In this embodiment, the B4C B-10 content in the four medium-enriched fuel assemblies 103 containing safety rods is 90%, the B4C B-10 content in the three medium-enriched fuel assemblies 104 containing regulator rods is 40%, and the B4C B-10 content in the twelve medium-enriched fuel assemblies 106 containing compensation rods is 60%. The total value of the safety rods 54 is 5560 pcm, the value of the three regulator rods 57 is 2155 pcm, and the total value of the twelve compensation rods 53 is 12553 pcm. The core reactivity control rods meet the design requirements for shutdown depth and sticking rods.
[0057] During operation, the core lifting procedure is as follows: safety rod 54 is fully lifted, regulating rod 57 is raised to half the core height, and compensating rod 53 is raised to the core criticality. During the burnup process, compensating rod 53 is raised to compensate for burnup reactivity loss. Regulating rod 57 does not need to compensate for the reactivity requirements of power rise and fall or for short-term reaction disturbance compensation.
[0058] In summary, this embodiment moderates the neutron spectrum in a core without a moderator by introducing metal hydride fuel rods, thereby increasing the core fission reaction rate and reducing the core critical mass. Simultaneously, it allows the core to utilize combustible poisons, as is common in pressurized water reactors, to assist in controlling the core's residual reactivity. More importantly, this embodiment employs a combination of different hydride types to adjust the equivalent nucleon density of uranium and hydrogen in different regions of the core, further flattening the core power distribution, preventing localized overheating, and improving core safety.
[0059] This invention is not limited to the above-described embodiments. Anyone should know that any structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention.
Claims
1. A reactor core employing a combination of different hydrides, characterized in that, It includes several fuel assemblies arranged radially from the center to the periphery; some of the fuel assemblies simultaneously contain uranium zirconium hydride fuel rods filled with uranium zirconium hydride fuel and uranium yttrium fuel rods filled with uranium yttrium hydride fuel.
2. The reactor core employing different hydride combinations according to claim 1, characterized in that, The fuel assemblies distributed radially from the center to the periphery include low-enrichment fuel assemblies, medium-enrichment fuel assemblies, and high-enrichment fuel assemblies. The low-enrichment fuel assembly includes yttrium uranium hydride fuel rods; the medium-enrichment fuel assembly includes both zirconium uranium hydride fuel rods and yttrium uranium hydride fuel rods; and the high-enrichment fuel assembly includes both zirconium uranium hydride fuel rods and yttrium uranium hydride fuel rods.
3. The reactor core employing different hydride combinations according to claim 2, characterized in that, Both the medium-enrichment fuel assembly and the high-enrichment fuel assembly are axially segmented fuel assemblies, which are arranged axially with zirconium hydride fuel rods and yttrium hydride fuel rods; the low-enrichment fuel assembly is an axially unsegmented fuel assembly.
4. The reactor core employing different hydride combinations according to claim 1, characterized in that, The stoichiometric ratio of hydrogen to zirconium in the uranium zirconium hydride fuel is selected from 1.2 to 1.9, and the stoichiometric ratio of hydrogen to yttrium in the uranium yttrium hydride fuel is selected from 1.5 to 2.
1.
5. The reactor core employing different hydride combinations according to claim 2, characterized in that, The low-enrichment fuel assembly has a fuel enrichment of 27% to 29%; the medium-enrichment fuel assembly has a fuel enrichment of 29% to 31%; and the high-enrichment fuel assembly has a fuel enrichment of 31% to 33%.
6. The reactor core employing different hydride combinations according to claim 3, characterized in that, The axially segmented zirconium hydride fuel rods and yttrium hydride fuel rods of the medium enrichment fuel assembly, as well as the axially segmented zirconium hydride fuel rods and yttrium hydride fuel rods of the high enrichment fuel assembly, are all coated with a pyrolytic carbon coating or a graphite coating.
7. The reactor core employing different hydride combinations according to claim 1, characterized in that, Both the zirconium hydride fuel rod and the yttrium hydride fuel rod comprise a fuel core, helium gas, and a stainless steel cladding; the ratio of the radius of the fuel core to the thickness of the stainless steel cladding satisfies a ratio of 9 to 10:
1.
8. The reactor core employing different hydride combinations according to any one of claims 1 to 7, characterized in that, The fuel assembly also includes a moderator rod; the moderator rod includes a zirconium hydride moderator rod and / or a yttrium hydride moderator rod.
9. The reactor core employing different hydride combinations according to claim 8, characterized in that, Some of the fuel assemblies also include control rods, which include safety rods, regulating rods, and compensating rods.
10. The reactor core employing different hydride combinations according to claim 9, characterized in that, The reactor core is arranged as follows: low-enrichment fuel assemblies with safety rods are located in the central region of the core; low-enrichment fuel assemblies without control rods are symmetrically and evenly arranged around the low-enrichment fuel assemblies with safety rods; medium-enrichment fuel assemblies with safety rods and medium-enrichment fuel assemblies with regulating rods are dispersed and symmetrically arranged around the low-enrichment fuel assemblies without control rods; medium-enrichment fuel assemblies without control rods are arranged in the central region of the core; and medium-enrichment fuel assemblies with compensating rods and high-enrichment fuel assemblies without control rods are arranged symmetrically around the core in sequence.