A lead bismuth cooled reactor core structure with inherent safety

Abstract

The application discloses a kind of lead bismuth cooled reactor core structures with inherent safety, which is composed of fuel area, control assembly and reactor vessel;Fuel area is arranged by fuel units in a regular hexagonal grid array;Each fuel unit is composed of an outer beryllium reflector and an inner silicon carbide substrate;The reflector is nested outside the substrate and is combined with the substrate under the action of electromagnetic device;The substrate is provided with staggered fuel channels and coolant channels;Fuel rods are made of uranium dioxide fuel and MoNbZr alloy cladding, and are arranged in the fuel channels;Liquid lead bismuth removes heat from the core through independent and parallel coolant channels in the substrate;The control assembly is arranged in the cavity outside the fuel unit and inside the reactor vessel;The application proposes a discrete core arrangement, which has significant inherent safety.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear reactor engineering, and in particular relates to a lead-bismuth cooled reactor core structure with inherent safety. Background Art

[0002] Small reactors are primarily used for one-stop energy supply or microgrids, providing isolated islands and remote areas with a higher energy density and longer-lasting stability than diesel generators. Compared to traditional commercial nuclear power systems, they are smaller, more compact, more economical, and have a shorter construction period.

[0003] With the development of small reactors, nuclear power is becoming closer to users and more interconnected, placing higher demands on operational safety. Currently, public acceptance of nuclear energy is low, and the sustainable development of nuclear power requires safer and more reliable reactor designs. Therefore, this invention aims to propose a small reactor core design with inherent safety that can address these issues. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a lead-bismuth cooled reactor core structure with inherent safety, which improves the operating safety of small reactors through reasonable structure and layout.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A lead-bismuth-cooled reactor core structure with inherent safety comprises a fuel zone, a control assembly 2, and a reactor vessel 3. The fuel zone is located at the center of the core and comprises a plurality of fuel elements 1 arranged in a regular hexagonal grid. The control assembly 2 is located in a cavity located outside the fuel zone and within the reactor vessel 3 at any position, with the cavity position determined according to actual needs. The reactor vessel 3 is a cylinder with a spherical lower head, which encloses all reactor components and is filled with liquid lead-bismuth coolant. The fuel elements 1 are cylindrical and discretely arranged within the reactor vessel 3, independent of each other, and are capable of driving the reactor into a critical state through neutron leakage coupling. The fuel elements 1 include a reflector 4 and a base 5. The reflector 4 is annular and nested outside the base 5 and coupled to the base 5 by an electromagnetic device. In the event of an overtemperature or power failure emergency, the reflector 4 can naturally detach from the base 5 by virtue of the buoyancy of the high-density lead-bismuth alloy, causing the core to automatically enter a subcritical shutdown state.

[0007] The fuel unit 1 is cylindrical and discretely arranged in the stack container 3, including a reflector 4 and a base 5; the reflector 4 is annular, nested outside the base 5 and combined with the base 5 under the action of an electromagnetic device; the base 5 is circular and divided into three circles according to a regular hexagonal grid. Fuel channels 6 and coolant channels 7 are respectively arranged in the grid. From the inside to the outside, there are successively arranged a central coolant channel, 6 intermediate fuel channels, 6 corner fuel channels arranged alternately, and 6 edge-center coolant channels.

[0008] The reflector 4 is made of metal beryllium with excellent neutron moderation and reflection properties, and the substrate 5 is made of high-temperature-resistant and corrosion-resistant silicon carbide.

[0009] Fuel rods are loaded in the fuel channels 6 of the substrate 5 ; the fuel rods are composed of fuel pellets 8 and cladding 9 .

[0010] The fuel pellets 8 of the fuel rods are made of uranium dioxide fuel with an enrichment of 19.75%, and the cladding 9 is made of MoNbZr alloy cladding.

[0011] The coolant channels 7 are independent parallel channels arranged on the base 5 . The coolant is driven by a coolant pump, flows through the coolant channels 7 , removes the fission heat conducted through the base 5 , and forms a circulation in the stack container 3 .

[0012] The lead-bismuth alloy coolant is a lead-bismuth eutectic alloy with a mass percentage of 44.5:55.5.

[0013] The control component 2 is made of a strong neutron absorber material.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. Compared with the traditional reactor core layout, the discrete fuel unit structure is adopted. The coupling between the units is achieved through neutron leakage. When the reactor temperature rises significantly, the coupling is weakened, introducing a natural negative feedback to the reactor.

[0016] 2. Each fuel unit is relatively independent. If any unit fails, the reactor will automatically enter a subcritical state, achieving a reliable accident shutdown. At the same time, the failed unit can be isolated and replaced with other units without affecting the subsequent operation of the reactor.

[0017] 3. Compared to traditional reactor fuel assemblies, fuel rods are placed on a high-temperature resistant matrix, transferring heat to the coolant through thermal conductivity. In the event of insufficient coolant, the matrix can accommodate a large amount of fuel heat release, significantly reducing the risk of core overheating and fuel melt. Coolant heat exchange in independent large-diameter channels effectively prevents coolant corrosion and abrasion of the cladding under the rod grid structure, significantly reduces the impact of coolant blockage, and improves reactor operation safety.

[0018] 4. Compared to traditional reactor fuel assemblies, each fuel element has an independent reflector, which effectively maintains the independence of each fuel element. The reflector is also bonded to the matrix by an electromagnetic device. In the event of overheating or power failure, the reflector can be separated from the matrix by the buoyancy of the lead-bismuth alloy, introducing negative reactivity and achieving automatic reactor shutdown. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the reactor core layout plan 1.

[0020] Figure 2 Schematic diagram of reactor core layout plan 2.

[0021] Figure 3 Schematic diagram of the cross section of the fuel unit.

[0022] Figure 4 Schematic diagram of the cross section of the fuel rod.

[0023] In the above figures: 1: fuel unit; 2: control assembly; 3: stack container; 4: reflector; 5: matrix; 6: fuel channel; 7: coolant channel; 8: fuel pellet; 9: cladding. DETAILED DESCRIPTION

[0024] The structure of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 Figure 2 shows an inherently safe lead-bismuth cooled reactor core structure consisting of a fuel zone, a control assembly 2, and a reactor vessel 3. The fuel zone is located in the center of the core and consists of several fuel cells 1 arranged in a regular hexagonal grid. The control assembly 2 is located in a cavity outside the fuel cells and within the reactor vessel 3. The reactor vessel 3 is a cylinder with a spherical lower head, housing all reactor components and filled with liquid lead-bismuth coolant.

[0026] like Figure 1 As shown, the independent fuel units 1 are discretely arranged, and the reactor enters a critical state through neutron leakage coupling.

[0027] like Figure 1 and Figure 2 As shown, the control assembly 2 can be arranged in a cavity at any position outside the fuel area and within the stack container 3, and the specific arrangement can be determined according to actual needs.

[0028] like Figure 3As shown, the fuel unit 1 is cylindrical with a radius of 11.28 cm and includes a reflector 4 and a substrate 5. The reflector 4 is made of metal beryllium, which has excellent neutron moderation and reflection properties, while the substrate 5 is made of high-temperature and corrosion-resistant silicon carbide. The reflector 4 is annular and nested outside the substrate 5 and is combined with the substrate by the action of an electromagnetic device. The substrate 5 is circular with a radius of 5.75 cm. The interior is divided into three circles according to a regular hexagonal grid with a grid pitch of 2.30 cm. The grid is provided with fuel channels 6 with a radius of 0.95 cm and coolant channels 7 with a radius of 1.15 cm. From the inside to the outside, there is a central coolant channel, six intermediate fuel channels, and six alternating corner fuel channels and six edge-core coolant channels.

[0029] like Figure 3 As shown, the coolant channels 7 are independent parallel channels arranged on the base 5. The coolant is driven by a coolant pump, flows through the coolant channels 7 to remove the fission heat conducted through the base 5, and forms a circulation in the reactor vessel 3.

[0030] like Figure 1 、 Figure 2 and Figure 3 As shown, to effectively control core reactivity and meet safety requirements during reactor operation, the core provides two independent control systems with different drive modes: a regulation system and a shutdown system. The regulation system consists of a control assembly 2, which is driven by a motor. By moving within its cavity, it changes the absorber area facing the core, achieving power regulation and reactivity compensation. Under normal operating conditions, the shutdown system uses electromagnetic devices to connect the reflector 4 of the fuel unit 1 to the matrix 5. In the event of an accident such as overtemperature or power failure, the reflector 4 can be separated from the matrix 5 by the buoyancy of the lead-bismuth alloy, introducing negative reactivity and thus achieving automatic shutdown.

[0031] like Figure 4 As shown, the fuel rod is round and loaded into the fuel channel 6 of the substrate 5. It consists of fuel pellets 8 and cladding 9. The fuel pellets 8 have a radius of 0.85 cm and use uranium dioxide fuel with a 19.75% enrichment, which has good thermal conductivity and high technological maturity. The cladding 9 is made of a MoNbZr alloy with a thickness of 0.1 cm and excellent high-temperature resistance.

Claims

1. A lead-bismuth cooled reactor core structure with inherent safety, characterized by: The core structure consists of a fuel zone, a control assembly (2) and a reactor container (3); the fuel zone is arranged at the center of the core and is composed of a plurality of fuel units (1) arranged in a regular hexagonal grid; the control assembly (2) is arranged in a cavity at any position outside the fuel zone and inside the reactor container (3); the reactor container (3) is a cylinder with a spherical lower head, which contains all the internal components of the reactor and is filled with liquid lead-bismuth coolant; the fuel units (1) are cylindrical, discretely arranged in the reactor container (3), independent of each other, and the reactor enters a critical state through neutron leakage coupling, and the fuel units (1) include a reflector (4) and a matrix (5); the reflector (4) is annular, nested outside the matrix (5) and combined with the matrix (5) under the action of an electromagnetic device, and the reflector (4) can naturally separate from the matrix (5) by relying on the buoyancy of the high-density lead-bismuth alloy under emergency conditions of over-temperature or power failure, so that the core automatically enters a subcritical shutdown state; The base (5) is circular, and its interior is divided into three circles according to a regular hexagonal grid. The grids are respectively provided with fuel channels (6) and coolant channels (7). From the inside to the outside, there are sequentially provided with a central coolant channel, six intermediate fuel channels, six alternately arranged corner fuel channels, and six edge-center coolant channels. The fuel rod is loaded into the fuel channel (6) of the substrate (5); The coolant channel (7) is an independent parallel channel arranged on the base (5). The coolant is driven by a coolant pump, flows through the coolant channel (7), takes away the fission heat conducted through the base (5), and forms a circulation in the stack container (3).

2. The lead-bismuth cooled reactor core structure with inherent safety according to claim 1, characterized in that: The material of the reflector (4) is metallic beryllium, and the material of the base (5) is silicon carbide.

3. The lead-bismuth cooled reactor core structure with inherent safety according to claim 1, characterized in that: The fuel rod is composed of a fuel pellet (8) and a cladding (9).

4. The lead-bismuth cooled reactor core structure with inherent safety according to claim 3, characterized in that: The fuel pellets (8) are uranium dioxide fuel, and the cladding (9) is a MoNbZr alloy cladding.

5. The lead-bismuth cooled reactor core structure with inherent safety according to claim 1, characterized in that: The material of the liquid lead-bismuth coolant is a eutectic alloy of lead and bismuth with a mass percentage of 44.5:55.

5.

6. The lead-bismuth cooled reactor core structure with inherent safety according to claim 1, characterized in that: The control component (2) is driven by a motor when in operation, and changes the area of ​​the absorber facing the core by moving in the cavity to which it belongs, thereby achieving the purpose of power regulation and reactivity compensation.

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