Fuel assembly, reactor core, and sodium-cooled fast reactor

Abstract

The embodiment of the application relates to the technical field of reactor fuel assemblies, in particular to a fuel assembly, a reactor core and a sodium-cooled fast reactor. The fuel assembly of the embodiment of the application accommodates sodium coolant through the sodium cavity section, thereby increasing the leakage of neutrons from the fuel section, reducing the sodium void reactivity, and enhancing the inherent safety of the reactor core; and the second fuel generation section is arranged to reuse the neutrons leaked to the sodium cavity section to generate fuel, thereby achieving an effective balance between the sodium void reactivity reduction and the breeding ratio increase of the reactor on the basis of reducing the sodium void reactivity.

Description

Technical Field

[0001] Embodiments of this application relate to the field of reactor fuel assembly technology, and particularly to a fuel assembly, a reactor core, and a sodium-cooled fast reactor. Background Technology

[0002] The statements herein are provided merely as background information in connection with this application and do not necessarily constitute prior art.

[0003] Generally speaking, for sodium-cooled fast reactors, the overall temperature or power reactivity feedback effect is required to be negative feedback.

[0004] However, sodium coolant in the reactor core can generate cavitation due to heating and boiling or other reasons. These sodium cavitation bubbles can further introduce changes in the core's reactivity; this phenomenon is called the sodium cavitation reactivity effect. In large sodium-cooled fast reactors, sodium cavitation reactivity is usually a positive reactivity feedback. When large-scale boiling of the sodium coolant in the core introduces a large amount of positive reactivity, it can potentially have a significant impact on reactor safety. Summary of the Invention

[0005] A brief overview of this application is provided below to offer a basic understanding of certain aspects thereof. It should be understood that this overview is not an exhaustive summary of the application. It is not intended to identify key or essential parts of the application, nor is it intended to limit its scope. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0006] In a first aspect, embodiments of this application provide a fuel assembly comprising: a fuel section configured to generate neutrons and energy through a fission reaction; a first fuel generation section configured to utilize neutrons from the fuel section to generate fuel; a fission gas containment section configured to contain fission gas generated by the fission reaction in the fuel section; a sodium cavity section configured to contain sodium coolant for increasing neutron leakage to reduce sodium cavitation reactivity; a second fuel generation section configured to utilize neutrons leaking into the sodium cavity section to generate fuel; a shielding section configured to shield neutrons; a sodium inflow section configured to allow sodium coolant to flow in therefrom; and a sodium outflow section configured to allow sodium coolant to flow out therefrom; wherein the sodium coolant is used to cool the fuel section.

[0007] The fuel assembly in this application increases the leakage of neutrons from the fuel section by setting up a sodium cavity to contain sodium coolant, thereby reducing sodium cavitation reactivity and enhancing the inherent safety of the reactor core. Furthermore, by setting up a second fuel generation section to reuse the neutrons leaking into the sodium cavity to generate fuel, the reactor's breeder ratio is increased while reducing sodium cavitation reactivity, thus improving fuel utilization. This achieves an effective balance between reducing sodium cavitation reactivity and increasing the breeder ratio.

[0008] Secondly, embodiments of this application also provide a fuel assembly, which includes an outer casing, a fuel rod bundle, a convertible material rod bundle, a shield, a sodium inlet, and a sodium outlet. The fuel rod bundle is disposed within the outer casing and is used to undergo a fission reaction to produce neutrons and energy. The convertible material rod bundle is disposed within the outer casing and is spaced apart from the fuel rod bundle, allowing sodium coolant to flow into the space to increase neutron leakage and reduce sodium cavitation reactivity. The convertible material rod bundle is configured to absorb neutrons leaking into the space and convert them into fuel. The shield is disposed within the outer casing and is configured to shield against neutrons. The sodium inlet is disposed at one end of the outer casing, and sodium coolant is configured to flow in from the sodium inlet and is used to cool the fuel rod bundle. The sodium outlet is disposed at the other end of the outer casing and is used to load and unload the fuel assembly and to supply sodium coolant for outflow.

[0009] The fuel assembly in this embodiment of the application, by spacing the fuel rod bundle and the convertible material rod bundle between them, allows sodium coolant to flow into the spacer, thereby increasing the leakage of neutrons from the fuel rod bundle, reducing sodium cavitation reactivity, and enhancing the inherent safety of the reactor. Furthermore, since the convertible material rod bundle absorbs the neutrons leaking into the spacer and converts them into fuel, it not only reduces sodium cavitation reactivity but also increases the reactor's breed rate and improves fuel utilization, thus achieving an effective balance between reducing sodium cavitation reactivity and increasing the breed rate.

[0010] Thirdly, embodiments of this application also provide a reactor core comprising the fuel assembly provided in either the first or second aspect of this application.

[0011] Fourthly, embodiments of this application also provide a sodium-cooled fast reactor, which includes the core of any embodiment of the third aspect of this application. Attached Figure Description

[0012] To further illustrate the above and other advantages and features of this application, the specific embodiments of this application will be described in more detail below with reference to the accompanying drawings. The drawings, together with the following detailed description, are included in and form a part of this specification. Elements having the same function and structure are indicated by the same reference numerals. It should be understood that these drawings only depict typical examples of this application and should not be considered as limiting the scope of this application.

[0013] Figure 1 This is a schematic diagram of the structure of a fuel assembly according to an embodiment of this application; Figure 2 This is a schematic diagram of a fuel assembly according to another embodiment of this application, in which the shielding body is omitted.

[0014] Explanation of reference numerals in the attached figures: 110. Fuel section; 120. First fuel generation section; 130. Fission gas containment section; 140. Sodium cavity section; 150. Second fuel generation section; 160. Shielding section; 170. Sodium inflow section; 180. Sodium outflow section; 210. Outer casing; 220. Fuel rod bundle; 230. Convertible material rod bundle; 240. Sodium inlet; 250. Sodium outlet. Detailed Implementation

[0015] Exemplary embodiments of this application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the development of any such actual embodiment to achieve the developer's specific goals, such as complying with constraints related to the system and business, and these constraints may vary depending on the implementation. Furthermore, it should be understood that while development work can be very complex and time-consuming, such development work is merely a routine task for those skilled in the art who benefit from the content of this application.

[0016] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the equipment structure and / or processing steps closely related to the solution according to this application are shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0017] The following disclosure provides several different implementations or examples for carrying out this application. To simplify the disclosure of this application, specific examples of components and methods are described below. Of course, these are merely examples and are not intended to limit this application. In the description of the embodiments of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0018] In related technologies, the current methods for reducing sodium cavitation reactivity in sodium-cooled fast reactors all have the drawback of reducing the reactor breeder ratio.

[0019] To address the aforementioned problems, embodiments of this application provide a fuel assembly. See also... Figure 1 , Figure 1 This is a schematic diagram of a fuel assembly provided according to an embodiment of this application. Figure 1 As shown, the fuel assembly includes: a fuel section 110 configured to generate neutrons and energy through a fission reaction; a first fuel generation section 120 configured to utilize neutrons from the fuel section 110 to generate fuel; a fission gas containment section 130 configured to contain fission gas generated by the fission reaction in the fuel section 110; a sodium cavity section 140 configured to contain sodium coolant to increase neutron leakage and reduce sodium cavitation reactivity; a second fuel generation section 150 configured to utilize neutrons leaking into the sodium cavity section 140 to generate fuel; a shielding section 160 configured to shield neutrons; a sodium inflow section 170 configured to allow sodium coolant to flow in therefrom; and a sodium outflow section 180 configured to allow sodium coolant to flow out therefrom; wherein the sodium coolant is used to cool the fuel section 110.

[0020] The fuel assembly in this embodiment increases the leakage of neutrons from the fuel section 110 by providing a sodium cavity section 140 to contain sodium coolant, thereby reducing sodium cavitation reactivity and enhancing the inherent safety of the reactor core. Furthermore, by providing a second fuel generation section 150 to reuse the neutrons leaking into the sodium cavity section 140 to generate fuel, the reactor's breeder ratio is increased while reducing sodium cavitation reactivity, thus improving fuel utilization. This achieves an effective balance between reducing sodium cavitation reactivity and increasing the breeder ratio.

[0021] In some embodiments, a sodium inflow section 170, a fission gas containment section 130, a first fuel generation section 120, a fuel section 110, a sodium cavity section 140, a second fuel generation section 150, a shielding section 160, and a sodium outflow section 180 are arranged sequentially.

[0022] In this embodiment, sodium coolant flows in from sodium inlet section 170, then sequentially through fission gas containment section 130, first fuel generation section 120, fuel section 110, sodium cavity section 140, second fuel generation section 150, and shielding section 160, finally exiting from sodium outlet section 180. When sodium coolant flows into sodium cavity section 140, it boils and generates cavitation bubbles, weakening its ability to reflect neutrons. More neutrons generated in fuel section 110 leak into sodium cavity section 140, introducing negative reactivity to counteract the positive reactivity introduced by sodium cavitation bubbles, thereby reducing the overall sodium cavitation reactivity of the reactor core. Furthermore, the second fuel generation section 150 is adjacent to sodium cavity section 140. The second fuel generation section 150 can absorb neutrons leaking into sodium cavity section 140 to generate fuel, thereby increasing the reactor breed ratio and improving fuel utilization.

[0023] In some embodiments, the fuel section 110 may be provided with uranium-enriched fuel or industrial plutonium fuel.

[0024] In some embodiments, the first fuel generation section 120 and the second fuel generation section 150 may be provided with convertible materials that can be converted into fuel by absorbing neutrons.

[0025] In some embodiments, the convertible material is depleted uranium fuel or natural uranium fuel, which can absorb neutrons and be converted into plutonium fuel.

[0026] In some embodiments, the shielding section 160 may be provided with a boron carbide shield.

[0027] The inventors of this application have discovered that when the height of the fuel section 110 in the fuel assembly is 800 mm and the height of the second fuel generation section 150 is 300 mm, the reactor breed rate increases by approximately 0.04 to 0.05 compared to when the second fuel generation section 150 is not present, while other reactor parameters remain unchanged. Therefore, in some embodiments, the height of the fuel section 110 is 800 mm and the height of the second fuel generation section 150 is 300 mm.

[0028] The inventors of this application have also discovered that when the height of the fuel section 110 in the fuel assembly is 800 mm, the height of the second fuel generation section 150 is 300 mm, and the height of the sodium cavity section 140 is 150 mm, the sodium cavitation reactivity is close to 0. Furthermore, with other reactor parameters remaining constant, the reactor breed rate increases by approximately 0.06 compared to when the second fuel generation section 150 is not present. This demonstrates that a lower sodium cavitation reactivity is achieved while significantly improving the reactor breed rate. Therefore, in some embodiments, the height of the sodium cavity section 140 is 150 mm.

[0029] Embodiments of this application also provide a fuel assembly. See also Figure 2 , Figure 2 This is a schematic diagram of a fuel assembly according to another embodiment of this application, where the shielding body is omitted. Figure 2 As shown, the fuel assembly includes an outer tube 210, a fuel rod bundle 220, a convertible material rod bundle 230, a shield, a sodium inlet 240, and a sodium outlet 250. The fuel rod bundle 220 is disposed within the outer tube 210 and is used to undergo a fission reaction to produce neutrons and energy. The convertible material rod bundle 230 is disposed within the outer tube 210, spaced apart from the fuel rod bundle 220, allowing sodium coolant to flow into the space to increase neutron leakage and reduce sodium cavitation reactivity. The convertible material rod bundle 230 is configured to absorb neutrons leaking into the space and convert them into fuel. The shield is disposed within the outer tube 210 and is configured to shield against neutrons. The sodium inlet 240 is disposed at one end of the outer tube 210, through which sodium coolant flows to cool the fuel rod bundle 220. The sodium outlet 250 is disposed at the other end of the outer tube 210 and is used to load and unload the fuel assembly and to supply sodium coolant for outflow.

[0030] The fuel assembly in this embodiment of the application, by spacing the fuel rod bundle 220 and the convertible material rod bundle 230 between them, allows sodium coolant to flow into the space, thereby increasing the leakage of neutrons from the fuel rod bundle 220, reducing sodium cavitation reactivity, and enhancing the inherent safety of the reactor. Furthermore, since the convertible material rod bundle 230 absorbs the neutrons leaking into the space and converts them into fuel, it not only reduces sodium cavitation reactivity but also increases the reactor's breed ratio and improves fuel utilization, thus achieving an effective balance between reducing sodium cavitation reactivity and increasing the breed ratio of the reactor.

[0031] In some embodiments, a shield is disposed on the side of the convertible material rod bundle 230 opposite to the fuel rod bundle 220; a sodium inflow member 240 is disposed at one end of the outer tube 210 near the fuel rod bundle 220; and a sodium outflow member 250 is disposed at one end of the outer tube 210 near the shield.

[0032] In this embodiment, the sodium inlet 240, fuel rod bundle 220, convertible material rod bundle 230, shield, and sodium outlet 250 are arranged sequentially. Sodium coolant flows in through the sodium inlet 240, then sequentially through the fuel rod bundle 220, convertible material rod bundle 230, and shield, before exiting through the sodium outlet 250. Because the fuel rod bundle 220 and convertible material rod bundle 230 are spaced apart, the sodium coolant flowing into the space boils and generates cavitation, weakening its ability to reflect neutrons. More neutrons from the fuel rod bundle 220 leak into the space, introducing negative reactivity to counteract the positive reactivity from the sodium cavitation, thereby reducing the overall sodium cavitation reactivity of the reactor core. The convertible material rod bundle 230 can absorb the neutrons leaking into the space and convert them into fuel, thereby increasing the reactor breed ratio and improving fuel utilization.

[0033] In some embodiments, the shielding body is made of boron carbide material.

[0034] In some embodiments, the fuel rod bundle 220 includes a plurality of fuel rods fixed relative to each other and forming a gap for sodium coolant to pass through; wherein each fuel rod is configured to undergo a fission reaction to produce neutrons and energy.

[0035] In such an embodiment, sodium coolant can pass through the gaps between the fuel rods to cool each fuel rod.

[0036] In some embodiments, the gap between two adjacent fuel rods is maintained by metal wire, thereby keeping the flow path of the sodium coolant substantially unchanged.

[0037] In some embodiments, each fuel rod includes: a cladding tube; a fuel pellet disposed within the cladding tube for generating energy and neutrons through a fission reaction; a first convertible material pellet disposed within the cladding tube and converted into a fuel pellet by absorbing neutrons from the fuel pellet; a seal configured to seal both ends of the cladding tube; a spaced distance between the first convertible material pellet and the seal located away from the fuel pellet to contain fission gases generated from the reaction of the fuel pellet; wherein the convertible material rod bundle 230 is disposed on the side closest to the fuel pellet.

[0038] In this embodiment, the first convertible material pellet and the convertible material rod bundle 230 are respectively disposed on both sides of the fuel pellet in the axial direction. Thus, the first convertible material pellet and the convertible material rod bundle 230 can absorb neutrons leaked from the fuel pellet to both sides in the axial direction and convert them into fuel, thereby further improving the reactor's breed ratio, increasing fuel utilization, and enhancing the reactor's inherent safety. Furthermore, by spacing the first convertible material pellet from the sealing element, space is reserved inside the cladding tube to accommodate fission gas, reducing the pressure inside the fuel rods.

[0039] In some embodiments, each fuel rod may further include a positioning element for maintaining the position of the fuel pellet within the cladding tube.

[0040] In some embodiments, the fuel pellets use uranium-enriched fuel or industrial plutonium fuel.

[0041] In some embodiments, the first convertible material pellet uses depleted uranium fuel or natural uranium fuel, which can absorb neutrons and be converted into plutonium fuel.

[0042] In some embodiments, the convertible material rod bundle 230 includes a plurality of convertible material rods fixed relative to each other and forming a gap for sodium coolant to pass through; wherein each convertible material rod is configured to convert leaked neutrons into fuel.

[0043] In such an embodiment, sodium coolant can pass through the gaps between the convertible material bars, thereby also cooling the individual convertible material bars.

[0044] In some embodiments, the gap between two adjacent convertible material bars is maintained by metal wire winding, thereby keeping the flow path of the sodium coolant substantially unchanged.

[0045] In some embodiments, each convertible material bar includes a second convertible material core.

[0046] In some embodiments, the second convertible material pellet in the convertible material rod uses depleted uranium fuel or natural uranium fuel.

[0047] In some embodiments, the diameter of the convertible material rod is larger than the diameter of the fuel rod.

[0048] In such an embodiment, the diameter of the convertible fuel rod is larger than that of the fuel rod, which can increase the fuel volume fraction in the fuel assembly, allowing for the inclusion of more convertible material and thus improving the reactor's breed ratio.

[0049] Embodiments of this application also provide a reactor core that includes a fuel assembly according to any embodiment of this application.

[0050] Embodiments of this application also provide a sodium-cooled fast reactor, which includes the core of any embodiment of this application.

[0051] The fuel assemblies, reactor cores, and sodium-cooled fast reactors provided in this application are further illustrated below with specific embodiments.

[0052] The target sodium-cooled fast reactor has a power output of 1500 MWt. For this target sodium-cooled fast reactor, the fuel assemblies and core are specifically configured as follows: The fuel assembly has a height of 4350 mm. The fuel rod bundle consists of 169 fuel rods, each 6.6 mm in diameter and 2170 mm in height. Each fuel rod contains a fuel pellet with a height of 860 mm, an equivalent diameter of 2665 mm, and an aspect ratio of 0.323. It uses (U,Pu)O2 fuel with a U-235 enrichment of 0.3 wt%. The PuO2 mass content in the inner, middle, and outer regions of the core is 23.4%, 29.0%, and 30.0%, respectively. The first convertible material pellet in each fuel rod has a height of 450 mm and uses depleted UO2 fuel with a U-235 enrichment of 0.3 wt%. The convertible material bundle comprises 37 convertible material rods with a diameter of 14.3 mm and a height of 575 mm. The second convertible material core in each convertible material rod has a height of 450 mm and uses lean UO2 fuel with a U-235 enrichment of 0.3 wt%. The spacing between the fuel rod bundle and the convertible material rod bundle is 300 mm.

[0053] The reactor core contains 403 fuel assemblies, 276 radial conversion zone assemblies, 117 steel shielding assemblies, 198 boron shielding assemblies, and 149 in-core spent fuel assembly storage locations. 24 control rod locations are reserved in-core. The radial conversion zone has a height of 2300 mm.

[0054] According to neutronics calculations, the sodium-cooled fast reactor with the above configuration has a sodium cavitation reactivity of 341 pcm at the beginning of its lifespan and a breeding ratio of approximately 1.1, achieving the goal of ensuring a low sodium cavitation reactivity while achieving a high breeding ratio.

[0055] Regarding the embodiments of this application, it should also be noted that, without conflict, the embodiments of this application and the features in the embodiments can be combined with each other to obtain new embodiments.

[0056] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. The scope of protection of this application shall be determined by the scope of the claims.

Claims

1. A fuel assembly, characterized in that, It includes: The fuel section is configured to produce neutrons and energy through a fission reaction; A first fuel generation section is configured to utilize neutrons from the fuel section to generate fuel; The fission gas containment section is configured to contain the fission gas produced by the fission reaction in the fuel section; The sodium cavity is configured to contain sodium coolant to increase neutron leakage and reduce sodium cavitation reactivity. The second fuel generation section is configured to utilize neutrons leaking into the sodium cavity section to generate fuel; The shielding section is configured to shield neutrons. The sodium inlet section is configured to allow sodium coolant to flow in from it; The sodium outflow section is configured to allow sodium coolant to flow out from it; The sodium coolant is used to cool the fuel section.

2. The fuel assembly according to claim 1, characterized in that, The sodium inflow section, the fission gas containment section, the first fuel generation section, the fuel section, the sodium cavity section, the second fuel generation section, the shielding section, and the sodium outflow section are arranged sequentially.

3. A fuel assembly, characterized in that, It includes: outer tube Fuel rod bundles, convertible material rod bundles, shielding, sodium inflow components, and sodium outflow components; The fuel rod bundle is disposed inside the outer tube and is used to undergo a fission reaction to produce neutrons and energy; The convertible material rod bundle is disposed inside the outer sleeve and spaced apart from the fuel rod bundle. Sodium coolant can flow into the space to increase neutron leakage and reduce sodium cavitation reactivity. The convertible material rod bundle is configured to absorb neutrons leaking into the interval and convert them into fuel; The shielding body is disposed inside the outer sleeve and is configured to shield neutrons; The sodium inlet is disposed at one end of the outer sleeve, and the sodium coolant is configured to flow in from the sodium inlet, the sodium coolant being used to cool the fuel rod bundle; The sodium outlet is located at the other end of the outer sleeve and is used to load and unload the fuel assembly and to supply the sodium coolant for outflow.

4. The fuel assembly according to claim 3, characterized in that, The shield is disposed on the side of the convertible material rod bundle opposite to the fuel rod bundle. The sodium inlet is located at one end of the outer sleeve near the fuel rod bundle; The sodium effluent is located at one end of the outer tube near the shield.

5. The fuel assembly according to claim 4, characterized in that, The fuel rod bundle includes a plurality of fuel rods, which are fixed relative to each other and form gaps for the passage of the sodium coolant; Each of the fuel rods is configured to undergo a fission reaction to produce neutrons and energy.

6. The fuel assembly according to claim 5, characterized in that, Each of the fuel rods comprises: Sheathing tube; Fuel pellets, disposed within the cladding tube, are used to generate energy and neutrons through a fission reaction; A first convertible material pellet is disposed within the fuel pellet inside the cladding tube and is converted into a fuel pellet by absorbing neutrons from the fuel pellet. A sealing element, configured to seal both ends of the casing tube; The first convertible material pellet is spaced apart from the seal located away from the fuel pellet to contain fission gases produced by the reaction of the fuel pellet; The convertible material rod bundle is disposed on one side close to the fuel pellet.

7. The fuel assembly according to claim 3 or 6, characterized in that, The convertible material rod bundle includes a plurality of convertible material rods, which are fixed relative to each other and form a gap for the sodium coolant to pass through; Each of the convertible material rods is configured to convert leaked neutrons into fuel.

8. The fuel assembly according to claim 7, characterized in that, Each of the convertible material bars includes a second convertible material core block.

9. The fuel assembly according to claim 7, characterized in that, The diameter of the convertible material rod is larger than the diameter of the fuel rod.

10. A reactor core, characterized in that, It includes the fuel assembly as described in any one of claims 1-9.

11. A sodium-cooled fast reactor, characterized in that, It includes the core as described in claim 10.

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