A lead-based fast reactor magnesium oxide reflector assembly and lead-bismuth fast spectrum reactor core arrangement

Abstract

The present invention belongs to nuclear reactor design technology, and specifically relates to a magnesium oxide reflector assembly and core arrangement for a lead-based fast reactor, wherein the reflector assembly includes an assembly box, a cladding, magnesium oxide and a coolant; the cladding is evenly arranged in the axial direction, the center of the cross section of the central cladding coincides with the center of the cross section of the assembly box, and the other claddings are evenly distributed in the hexagonal cross section of the assembly box, and the center of the cross section of adjacent claddings is equidistant. The reflector assembly is arranged at the periphery of the core active area; a control rod assembly is arranged at the center of the core active area, and hexagonal fuel assemblies with low to high enrichment are evenly arranged in two layers around the control rod assembly from inside to outside according to the hexagonal cross section, and the other control rod intervals are evenly arranged in the fuel assemblies of one enrichment. The present invention has a more significant improvement on the operation cycle of the lead-based fast reactor, and can reflect a large number of neutrons overflowing the core back to the core, improve the neutron utilization rate, and extend the operation cycle of the lead-based fast reactor.

Description

Technical Field

[0001] The invention belongs to the field of nuclear reactor design technology, and in particular relates to a magnesium oxide reflector assembly and a core arrangement for a lead-based fast reactor. Background Art

[0002] The lead-based fast spectrum reactor uses lead or lead-bismuth alloy as coolant. Lead or lead-bismuth alloy has the characteristics of weak neutron slowing down, strong thermal conductivity and stable chemical properties. These properties make the lead-based fast spectrum reactor have excellent neutron physics, thermal hydraulics and system safety properties, and it has been selected as the "fourth generation" advanced nuclear energy system recognized by the international mainstream nuclear energy community.

[0003] Compared with pressurized water reactors, fast reactors have a higher neutron leakage rate. In order to reduce leakage and increase the operating cycle of the reactor, a large number of radial reflector assemblies are generally arranged around the core fuel area. The radial reflector assemblies can reflect neutrons that overflow the core or the radial conversion zone back to the core or the conversion zone to improve the neutron utilization rate and the proliferation ratio. At the same time, they can also play a certain shielding role for gamma rays and neutrons, reducing the adverse effects of neutron and gamma irradiation on reactor equipment.

[0004] At present, the neutron reflector components of fast reactors mostly use stainless steel as the reflector material. This type of component has a general neutron reflection capability and has limited effect on improving neutron utilization. Summary of the invention

[0005] The purpose of the present invention is to provide a lead-based fast reactor magnesium oxide reflector assembly and a lead-bismuth fast spectrum reactor core arrangement, which can significantly reduce neutron leakage and improve neutron utilization.

[0006] The technical solution of the present invention is as follows:

[0007] A lead-based fast reactor magnesium oxide reflector assembly comprises a hexagonal tubular assembly box, a plurality of claddings arranged in the assembly box, magnesium oxide and a coolant; the claddings are cylindrical, all placed along the axial direction and evenly arranged in the cross-sectional direction, the cross-sectional center of one cladding coincides with the cross-sectional center of the assembly box, that is, the cladding is arranged concentrically and coaxially with the assembly box, and the remaining claddings are evenly distributed in the hexagonal cross-section of the assembly box, and the distances between the cross-sectional centers of all adjacent claddings are all equal;

[0008] The magnesium oxide is located in the cladding, and the cladding and the internal magnesium oxide together form a reflector rod, and the gap between the component box and the cladding is entirely filled with coolant.

[0009] The interior of the cladding is filled with coolant, and the gap between the cladding and the component box is filled with magnesium oxide.

[0010] The number of the claddings is such that the cross-sectional centers of three adjacent claddings are arranged to form an equilateral triangle.

[0011] The number of the claddings is 7, 19 or 37.

[0012] The coolant is lead or lead-bismuth alloy.

[0013] The component box is made of stainless steel.

[0014] The length of the enclosure is the same as that of the component box, that is, all enclosures run through the entire length direction of the component box.

[0015] The lead-based fast reactor magnesium oxide reflector assembly is arranged at the periphery of the core active area; a control rod assembly is arranged at the center of the core active area, and hexagonal fuel assemblies with enrichment from low to high are evenly arranged in two layers around the control rod assembly from inside to outside according to the hexagonal cross-section, and the remaining control rod intervals are evenly arranged in the fuel assemblies of one enrichment.

[0016] The lead-based fast reactor magnesium oxide reflector assembly is arranged at the periphery of the core active area; a total of 114 hexagonal fuel assemblies are arranged in the core active area, including fuel assemblies with an enrichment of 15.5%, fuel assemblies with an enrichment of 17.5%, and fuel assemblies with an enrichment of 19.5%, which are evenly arranged in two layers according to the hexagonal cross-section from the inside to the outside;

[0017] Among them, there are 18 fuel assemblies with an enrichment of 15.5%, 36 fuel assemblies with an enrichment of 17.5%, and 60 fuel assemblies with an enrichment of 19.5%.

[0018] The lead-based fast reactor magnesium oxide reflector layer components are 90, which are evenly arranged in two layers around the core active area;

[0019] The number of the control rod assemblies is 7, one of which is arranged at the center of the core active area, and the other 6 are arranged at the overlapping positions of two adjacent sides of the first layer of hexagons of the fuel assembly with an enrichment degree of 17.5%.

[0020] There are 18 fuel assemblies with an enrichment degree of 15.5%, all of which are arranged in two layers in a hexagonal shape with one control rod assembly as the center, with 6 in the first layer and 12 in the second layer. There are 36 fuel assemblies with an enrichment degree of 17.5%, which are arranged in two layers in a hexagonal shape around the 18 fuel assemblies with an enrichment degree of 15.5%, with 2 in the middle of each side in the first layer, with a total of 12 fuel assemblies with an enrichment degree of 17.5%, and in the second layer, 2 in the middle of each side, with a total of 12 fuel assemblies with an enrichment degree of 17.5%. A control rod assembly is arranged at the overlapping position of each adjacent two sides in a layer, so that a total of 6 control rod assemblies are arranged in the first layer; a total of 24 fuel assemblies with an enrichment of 17.5% are evenly arranged in the second layer; there are 60 fuel assemblies with an enrichment of 19.5%, which are arranged in two layers outside the fuel assembly with an enrichment of 17.5%, of which a total of 30 are evenly arranged in the first layer, and 5 are evenly arranged on each side of the second layer, for a total of 30; a reflector layer assembly is arranged at the overlapping position of each adjacent two sides in the second layer.

[0021] The lead-based fast reactor magnesium oxide reflector assembly is arranged at the periphery of the core active area; a total of 54 hexagonal fuel assemblies are arranged in the core active area, including 18 fuel assemblies with an enrichment of 15% and 36 fuel assemblies with an enrichment of 19% which are evenly arranged in two layers according to the hexagonal cross-section from the inside to the outside;

[0022] The number of lead-based fast reactor magnesium oxide reflector assemblies is 68, which are evenly arranged in two layers around the core active area;

[0023] The number of the control rod assemblies is 7, one of which is arranged at the center of the core active area, and the other 6 are arranged at the overlapping positions of two adjacent sides of the first layer hexagon of the fuel assembly with an enrichment degree of 19%.

[0024] The control rod assembly contains 37 control rod absorbers in total, and the control rod absorber material is B4C.

[0025] The thickness of the shell is 0.8 mm, and the thickness of the component box is 2 mm.

[0026] The fuel assemblies described above all contain 169 cylindrical fuel element rods.

[0027] The fuel material is UO2, the diameter of the fuel element rod is 12 mm, and the height of the active section is 900 mm.

[0028] The significant effects of the present invention are as follows: compared with the integrated reflector assembly using lead oxide material, the present invention has a more significant improvement on the operating cycle of the lead-based fast reactor, and the magnesium oxide material has a low density, a high melting point, is non-toxic, has a low production cost, and is more economical. The reflector assembly using this structure is usually used outside the core fuel area. When the reactor is operating normally, a large number of neutrons overflowing the core can be reflected back to the core, thereby greatly improving the neutron utilization rate, which is of great significance for extending the operating cycle of the lead-based fast reactor and improving its economy.

[0029] After arranging this type of reflector assembly outside the core fuel area, a large number of neutrons overflowing the core will be reflected back into the core, thereby greatly improving the neutron utilization rate of the core, extending the operating cycle of the reactor, and improving the economy of the lead-based fast spectrum reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a cross-sectional view of a 7-rod magnesium oxide reflector assembly;

[0031] Figure 2 It is a longitudinal section view of a 7-rod magnesium oxide reflector assembly;

[0032] Figure 3 It is a cross-sectional view of a 19-hole magnesium oxide reflective layer assembly;

[0033] Figure 4 It is a longitudinal section view of a 19-hole magnesium oxide reflector assembly;

[0034] Figure 5 This is a schematic diagram of the core layout of a 150MW lead-bismuth fast-spectrum reactor;

[0035] Figure 6 This is a schematic diagram of the core layout of a 75MW lead-bismuth fast-spectrum reactor;

[0036] In the figure: 1. cladding; 2. magnesium oxide; 3. assembly box; 4. coolant; 100. reflector assembly; 200. control rod assembly; 300. fuel assembly with an enrichment of 19.5%; 400. fuel assembly with an enrichment of 17.5%; 500. fuel assembly with an enrichment of 15.5%; 600. fuel assembly with an enrichment of 19%; 700. fuel assembly with an enrichment of 15%. DETAILED DESCRIPTION

[0037] The present invention will be further described below through the accompanying drawings and specific implementation methods.

[0038] Embodiment 1,

[0039] like Figure 1 and Figure 2The 7-rod magnesium oxide reflective layer assembly shown in the figure has an assembly box 3 which is a columnar structure with a hexagonal cross section, i.e., a hexagonal prism tubular structure. A cylindrical cladding 1 is placed inside the assembly box 3 along the axial direction. The cladding 1 contains magnesium oxide 2. The space between the assembly box 3 and the cladding 1 is entirely filled with coolant 4.

[0040] The cladding 1 and the magnesium oxide 2 inside together form a reflector rod. The cladding 1 is cylindrical, so a cylindrical reflector channel is formed. In this embodiment, there are 7 reflector rods, which are evenly distributed in the hexagonal cross section according to the position of the center of the cross section. Among them, the center of the cross section of the middle reflector rod coincides with the center of the hexagonal cross section, and the remaining 6 reflector rods are evenly distributed around the outside of the central reflector rod, and the distances between the centers of the cross sections of all adjacent reflector rods are all equal.

[0041] The coolant 4 is lead or lead-bismuth alloy;

[0042] The number of reflector rods can also be 19, 37, etc., as long as the number satisfies the arrangement of the cross-section centers of three adjacent reflector rods to form an equilateral triangle.

[0043] The component box 3 is made of stainless steel.

[0044] Embodiment 2,

[0045] Different from the first embodiment, there is another arrangement of the magnesium oxide 2 , the coolant 4 and the cladding 1 in the component box 3 .

[0046] like Figure 3 and Figure 4 As shown, the component box 3 is also a columnar structure with a hexagonal cross-section, that is, a hexagonal tubular structure. The cylindrical cladding 1 is placed inside the component box 3 along the axial direction, and the number of claddings 1 satisfies the above-mentioned rule that the distances between the centers of all three adjacent cladding 1 cross-sections are equal, and the center of the cladding 1 cross-section at the center coincides with the center of the component box 3 cross-section. The number of claddings 1 is 7, 19, 37, etc.

[0047] The difference is that the interior of the cladding 1 is a flow channel for the coolant 4, and the gap between the cladding 1 and the component box 3 is magnesium oxide 2;

[0048] In this embodiment, the number of the cladding 1 is 19, so the cross section of the magnesium oxide reflective layer assembly has 19 holes, and the holes are flow channels for the coolant 4.

[0049] The length of the enclosure 1 is the same as that of the component box 3 , that is, all the enclosures 1 run through the entire length direction of the component box 3 .

[0050] like Figure 5 As shown, a lead-bismuth fast-spectrum core arrangement with a hot full power of 150MW is shown;

[0051] A total of 114 hexagonal fuel assemblies are arranged in the core active area, including fuel assembly 300 with an enrichment of 19.5%, fuel assembly 400 with an enrichment of 17.5%, and fuel assembly 500 with an enrichment of 15.5%;

[0052] There are 18 fuel assemblies 500 with an enrichment of 15.5%, all of which are evenly arranged in a hexagonal shape in two layers with a control rod assembly 200 as the center, with 6 in the first layer and 12 in the second layer.

[0053] There are 36 fuel assemblies 400 with an enrichment degree of 17.5%, which are arranged in two layers in a hexagonal shape around the 18 fuel assemblies 500 with an enrichment degree of 15.5%, wherein the first layer has two fuel assemblies 400 arranged in the middle of each side, for a total of 12 fuel assemblies 400 with an enrichment degree of 17.5%, and a control rod assembly 200 is arranged at the overlapping position of each two adjacent sides in the first layer, so that a total of 6 control rod assemblies 200 are arranged in the first layer; a total of 24 fuel assemblies 400 with an enrichment degree of 17.5% are evenly arranged in the second layer;

[0054] There are 60 fuel assemblies 300 with an enrichment degree of 19.5%, which are arranged in two layers around the fuel assembly 400 with an enrichment degree of 17.5%, wherein 30 are evenly arranged in the first layer, and 5 are evenly arranged on each side of the second layer, for a total of 30; a reflector assembly 100 is arranged at the overlapping position of each adjacent side of the second layer;

[0055] All the remaining reflective layer components 100 are evenly arranged in two layers on the outermost side;

[0056] The number of all reflector assemblies 100 is 90, and the number of control rod assemblies 200 is 7;

[0057] In this embodiment, the core adopts three 235 U enrichment assemblies, corresponding to enrichments of 15.5%, 17.5%, and 19.5% respectively. All fuel assemblies are arranged in sequence in the core active area from the inside to the outside.

[0058] Each fuel assembly adopts the design structure of fuel element rods plus assembly box. Each fuel assembly contains 169 cylindrical fuel element rods. The diameter of the fuel element rods is 12mm, the active section height is 900mm, the fuel material is UO2, the outer side length of the assembly box cross section is 117.5mm, the assembly box thickness is 2mm, and the assembly box material is stainless steel.

[0059] The control rod assembly 200 adopts a design structure of control rod plus assembly box. Each control rod assembly contains 37 control rod absorbers. The main absorber material of the control rod is B4C. The control rod diameter is 23mm and the active section height is 900mm. The size and material of the assembly box of the control rod assembly 200 are the same as those of the fuel assembly.

[0060] In order to extend the core life and improve the economy of the lead-based fast reactor, 90 magnesium oxide reflector assemblies 100 are arranged outside the core active area (outside the fuel assembly). The structure of each reflector assembly 100 adopts the design of Example 1, and 7 reflector rods are installed inside. The reflector rod diameter is 80 mm, the cladding 1 thickness is 0.8 mm, and the active section height is 900 mm. The size and material of the assembly box 3 are the same as those of the fuel assembly. It is calculated that the operating cycle of the reactor is extended by about 600 equivalent full power days compared with the reactor using the traditional stainless steel reflector assembly.

[0061] Figure 6 A lead-bismuth fast-spectrum core arrangement with a hot full power of 75 MW was demonstrated;

[0062] Different from the above 150MW arrangement, there are 54 hexagonal fuel assemblies arranged in the core active area, including 36 fuel assemblies 600 with an enrichment of 19%, 18 fuel assemblies 700 with an enrichment of 15%; 7 control rod assemblies 200; 68 reflector layer assemblies 100;

[0063] The arrangement is basically the same as the previous 150MW arrangement, with a control rod assembly 200 at the center, and two layers of fuel assemblies 700 with an enrichment of 15%, two layers of fuel assemblies 600 with an enrichment of 19%, and two layers of reflector layer assemblies 100 arranged closely and evenly in a hexagon from the inside to the outside, wherein a control rod assembly 200 is arranged at each of the overlapping positions of two adjacent sides of the hexagon of the first layer of fuel assemblies 600 with an enrichment of 19%;

[0064] In this arrangement, all components are arranged in a hexagonal pattern with equal spacing, and the core uses two 235 U enrichment assemblies, corresponding to enrichments of 18% and 19.5% respectively. All fuel assemblies are arranged in sequence in the core active area from the inside to the outside.

[0065] The fuel assemblies all adopt the design structure of fuel element rods plus assembly boxes. Each fuel assembly contains 169 cylindrical fuel element rods. The diameter of the fuel element rods is 12mm, the active section height is 900mm, the fuel material is UO2, the outer side length of the assembly box 3 is 117.5mm, the thickness of the assembly box 3 is 2mm, and the assembly box material is stainless steel.

[0066] The control rod assembly 200 adopts a design structure of control rod plus assembly box. Each control rod assembly contains 37 control rod absorbers. The control rod absorber material is B4C. The outer diameter of the control rod is 23mm and the active section height is 900mm. The size and material of the assembly box are the same as those of the fuel assembly.

[0067] In order to extend the core life and improve the economy of the lead-based fast reactor, 68 magnesium oxide reflector assemblies 100 are arranged outside the core active area (outside the fuel assembly). The reflector assembly 100 adopts the design of Example 2, and the reflector has 19 cylindrical channels with a channel diameter of 20 mm. The cladding 1 is 0.8 mm thick and the active section height is 900 mm. The size and material of the assembly box 3 are the same as those of the fuel assembly. It is calculated that the core operation cycle is extended by about 800 equivalent full power days compared with the reactor using the traditional stainless steel reflector assembly.

Claims

1. A lead-bismuth fast spectrum reactor core arrangement, characterized in that: A lead-based fast reactor magnesium oxide reflector assembly (100) is arranged at the periphery of the core active region; a control rod assembly (200) is arranged at the center of the core active region, and hexagonal fuel assemblies with enrichments from low to high are evenly arranged in two layers around the control rod assembly (200) from inside to outside according to the hexagonal cross-section, and the remaining control rod intervals (200) are evenly arranged in fuel assemblies with one enrichment; The lead-based fast reactor magnesium oxide reflector assembly (100) comprises a hexagonal tubular assembly box (3), a plurality of claddings (1) arranged in the assembly box (3), magnesium oxide (2) and a coolant (4); the claddings (1) are cylindrical, all arranged along the axial direction and evenly arranged in the cross-sectional direction, the cross-sectional center of one cladding (1) coincides with the cross-sectional center of the assembly box (3), that is, the cladding (1) and the assembly box (3) are arranged concentrically and coaxially, and the remaining claddings (1) are evenly distributed in the hexagonal cross-section of the assembly box (3), and all adjacent claddings are arranged in a uniform manner. (1) are all equal in distance between the centers of the cross sections; the magnesium oxide (2) is located inside the cladding (1), the cladding (1) and the magnesium oxide (2) inside together form a reflector rod, and the gap between the component box (3) and the cladding (1) is all filled with coolant (4); the inside of the cladding (1) is filled with coolant (4), and the gap between the cladding (1) and the component box (3) is filled with magnesium oxide (2); the coolant (4) is lead or a lead-bismuth alloy; the number of the claddings (1) is such that the centers of the cross sections of three adjacent claddings (1) are arranged in an equilateral triangle; The length of the cladding (1) is the same as the length of the component box (3), that is, all the claddings (1) extend through the entire length direction of the component box (3); the number of the claddings (1) is 7, 19 or 37; the material of the component box (3) is stainless steel; A total of 114 hexagonal fuel assemblies are arranged in the core active area, including fuel assemblies (500) with an enrichment of 15.5%, fuel assemblies (400) with an enrichment of 17.5%, and fuel assemblies (300) with an enrichment of 19.5%, which are evenly arranged in two layers according to the hexagonal cross-section from the inside to the outside; Among them, there are 18 fuel assemblies (500) with an enrichment of 15.5%, 36 fuel assemblies (400) with an enrichment of 17.5%, and 60 fuel assemblies (300) with an enrichment of 19.5%. The lead-based fast reactor magnesium oxide reflector layer assemblies (100) are 90 in number and are evenly arranged in two layers on the periphery of the core active area; The number of the control rod assemblies (200) is 7, one of which is arranged at the center of the core active area, and the other 6 are arranged at the overlapping positions of two adjacent sides of the first layer of the hexagon of the fuel assembly (400) with an enrichment degree of 17.5%; There are 18 fuel assemblies (500) with an enrichment of 15.5%, all of which are arranged in two layers in a hexagonal shape with one control rod assembly (200) as the center, with 6 fuel assemblies arranged in the first layer and 12 fuel assemblies arranged in the second layer; there are 36 fuel assemblies (400) with an enrichment of 17.5%, which are arranged in two layers in a hexagonal shape around the 18 fuel assemblies (500) with an enrichment of 15.5%, with 2 fuel assemblies (400) arranged in the middle of each side in the first layer, with a total of 12 fuel assemblies (400) with an enrichment of 17.5%, and in the first layer A control rod assembly (200) is arranged at the overlapping position of each adjacent two sides, so that a total of 6 control rod assemblies (200) are arranged in the first layer; a total of 24 fuel assemblies (400) with an enrichment degree of 17.5% are evenly arranged in the second layer; the fuel assemblies (300) with an enrichment degree of 19.5% are 60 in number, and are arranged in two layers around the fuel assemblies (400) with an enrichment degree of 17.5%, wherein a total of 30 are evenly arranged in the first layer, and 5 are evenly arranged on each side of the second layer, for a total of 30; and a reflector assembly (100) is arranged at the overlapping position of each adjacent two sides in the second layer.

2. A lead-bismuth fast-spectrum reactor core arrangement as claimed in claim 1, characterized in that: A total of 54 hexagonal fuel assemblies are arranged in the core active area, including 18 fuel assemblies (700) with an enrichment of 15% and 36 fuel assemblies (600) with an enrichment of 19%, which are evenly arranged in two layers according to the hexagonal cross-section from the inside to the outside. The number of lead-based fast reactor magnesium oxide reflector layer assemblies (100) is 68, which are evenly arranged in two layers around the core active area; The number of the control rod assemblies (200) is 7, one of which is arranged at the center of the core active area, and the other 6 are arranged at the overlapping positions of two adjacent sides of the first layer of the hexagon of the fuel assembly (600) with an enrichment of 19%.

3. A lead-bismuth fast-spectrum reactor core arrangement as claimed in claim 1, characterized in that: The control rod assembly (200) contains a total of 37 control rod absorbers, and the control rod absorber material is B4C.

4. A lead-bismuth fast spectrum reactor core arrangement as claimed in claim 1, characterized in that: The thickness of the cladding shell (1) is 0.8 mm, and the thickness of the component box (3) is 2 mm.

5. A lead-bismuth fast-spectrum reactor core arrangement as claimed in claim 1, characterized in that: The fuel assemblies described above all contain 169 cylindrical fuel element rods.

6. A lead-bismuth fast-spectrum reactor core arrangement as claimed in claim 5, characterized in that: The fuel material is UO2, the diameter of the fuel element rod is 12 mm, and the height of the active section is 900 mm.

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