Reactor core of fast reactor

Abstract

The invention particularly relates to a fast reactor core, which belongs to the technical field of fast reactor cores, and comprises a reactor body container and a reactor core accommodated and supported in the reactor body container, the reactor core comprises fuel assemblies, a reflecting layer assembly, a first shielding assembly, a storage trap assembly and a second shielding assembly which are radially arranged in sequence from inside to outside, and a control rod assembly arranged between the fuel assemblies; the fuel assembly is composed of depleted uranium fuel element rods and uranium-plutonium mixed fuel element rods, and the quantity ratio of the depleted uranium fuel element rods to the uranium-plutonium mixed fuel element rods is determined by the proliferation ratio in the reactor core; and the proliferation ratio in the reactor core is 0.99-1.01. According to the fast reactor core disclosed by the invention, the burnup reactive damage in the subsequent reactor operation period is balanced by utilizing the increased reactivity of the newly proliferated fissile nuclide in the reactor core, so that the instantaneous supercritical safety risk caused by overhigh backup reactivity is fundamentally eliminated.

Description

Technical Field

[0001] The present invention relates to the technical field of fast reactor core, in particular to a fast reactor core. Background Art

[0002] In the core design of existing fast reactors, a large number of compensating control rod assemblies are arranged to control the higher backup reactivity of the reactor. During the operation of the unit, the positive reactivity is released by continuously adjusting the axial position of the compensating control rod to compensate for the reactivity loss caused by the consumption of fissile nuclides in the reactor, that is, the burnup reactivity loss. On the one hand, this scheme requires adding through holes to the reactor rotating shield plug to arrange the compensating control rod drive mechanism to drive the axial movement of the compensating control rod; on the other hand, the reactor needs to reserve a large backup reactivity in the initial design to balance the burnup reactivity loss during the subsequent operation of the reactor, which increases the instantaneous supercritical safety risk caused by the uncontrolled lifting of the compensating control rod during the operation of the unit. Summary of the invention

[0003] The object of the present invention is to provide a fast reactor core, which utilizes the hard neutron spectrum of the fast reactor, has an internal breeding ratio close to 1.0, eliminates the compensating control rod assembly in the core, and utilizes the increased reactivity of the newly-breeding fissile nuclides in the core to balance the burnup reactivity damage during subsequent reactor operation. The number of openings on the reactor rotating shield plug can be reduced, the reliability of the primary circuit boundary operation can be improved, and the prompt supercritical safety risk caused by excessive backup reactivity can be fundamentally eliminated.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A fast reactor core comprises a reactor body container and a reactor core contained and supported in the reactor body container; the reactor core comprises a fuel assembly, a reflector assembly, a first shielding assembly, a storage well assembly and a second shielding assembly radially arranged in sequence from the inside to the outside, and a control rod assembly arranged between the fuel assemblies; the fuel assembly is composed of depleted uranium fuel element rods and uranium-plutonium mixed fuel element rods, and the quantity ratio of the depleted uranium fuel element rods and the uranium-plutonium mixed fuel element rods is determined by the proliferation ratio in the reactor core; the proliferation ratio in the reactor core is 0.99-1.01.

[0006] As one possible implementation, the depleted uranium fuel rod and the uranium-plutonium mixed fuel rod are both cylindrical and have the same length and diameter;

[0007] A first axial regeneration zone is arranged axially in the center of the depleted uranium fuel element rod, and the first axial regeneration zone and the depleted uranium fuel element rod share a central axis; a second axial regeneration zone, a core active zone and a third axial regeneration zone are arranged axially at equal intervals from top to bottom in the uranium-plutonium mixed fuel element rod, and the second axial regeneration zone, the core active zone, the third axial regeneration zone and the uranium-plutonium mixed fuel element rod share a central axis;

[0008] The first axial regeneration zone, the second axial regeneration zone, the core active zone and the third axial regeneration zone are all cylindrical and have the same diameter. The length of the first axial regeneration zone is equal to the sum of the lengths of the second axial regeneration zone, the core active zone and the third axial regeneration zone. The lengths of the second axial regeneration zone and the third axial regeneration zone are the same. The length of the core active zone is equal to the sum of the lengths of the second axial regeneration zone and the third axial regeneration zone.

[0009] The first axial regenerated zone is composed of 0.25-0.7% U-235 by mass and 99.3%-99.75% U-238 by mass; the core active zone is composed of 30-60% Pu-239 by mass and 40-70% U-238 by mass; the second axial regenerated zone and the third axial regenerated zone are both composed of 0.25-0.7% U-235 by mass and 99.3-99.75% U-238 by mass.

[0010] As one of the feasible ways, the core is a regular hexagonal structure; the fuel assembly is a regular hexagonal structure consisting of depleted uranium fuel rods and uranium-plutonium mixed fuel rods arranged alternately in layers, and the depleted uranium fuel rods and uranium-plutonium mixed fuel rods are arranged alternately in every other layer;

[0011] The ratio of the number of depleted uranium fuel rods and uranium-plutonium mixed fuel rods is determined by the in-core breeding ratio; the in-core breeding ratio is defined as the ratio of the generation rate of the fissile nuclide U-238 in the core to the consumption rate of the fissile nuclides U-235 and Pu-239 in the core, and its numerical expression is:

[0012] CR=

[0013] Among them, CR is the core proliferation ratio.

[0014] As one achievable method, determining the quantity ratio of depleted uranium fuel element rods and uranium-plutonium mixed fuel element rods according to the in-core breeding ratio includes the following steps:

[0015] Based on the average neutron energy of the fast reactor core, determine the microscopic radiation capture cross section of U-238, the microscopic absorption cross section of U-235 and the microscopic absorption cross section of Pu-239 through existing data or engineering experience;

[0016] According to the calculation formula of the in-core proliferation ratio, the number of nucleons of U-238, U-235 and Pu-239 in the fuel assembly 13 is determined;

[0017] The quantity ratio of the depleted uranium fuel rods and the uranium-plutonium mixed fuel rods is determined based on the nucleon numbers of U-238, U-235 and Pu-239 in the fuel assembly 13 and the mass percentages of U-238, U-235 and Pu-239 in the depleted uranium fuel rods and the uranium-plutonium mixed fuel rods.

[0018] As one of the feasible ways, depleted uranium fuel element rods are made from the depleted uranium tails left over from uranium enrichment in pressurized water reactors, and uranium-plutonium mixed fuel element rods are made from uranium-plutonium mixed fuel.

[0019] As one of the feasible ways, in the radial arrangement of the core, the number of fuel assemblies meets the minimum critical mass requirement of the reactor, that is, the total mass of the fissile nuclides U-235 and Pu-239 initially loaded in the core is greater than the minimum critical mass required for the criticality and power operation of the reactor.

[0020] As one of the feasible ways, with the core center as the center of the circle, the east direction is 0° / 360°, the south direction is 270°, the west direction is 180°, and the north direction is 90°; the control rod assembly consists of an adjusting control rod assembly and a safety control rod assembly, the safety control rod assembly is used to control the safe shutdown of the reactor, and the adjusting control rod assembly is used to control the reactor core power; a group of adjusting control rod assemblies are arranged at 90° and 270° directions of the core, and the reactivity value of each group of adjusting control rod assemblies is 150-200pcm; a group of safety control rod assemblies are arranged at the core center, 45°, 135°, 225° and 315° directions, and the reactivity value of each group of safety control rod assemblies is 750-850pcm.

[0021] As one of the possible implementations, the adjustment control rod assembly includes an adjustment control rod and an adjustment control rod driving mechanism, and the adjustment control rod driving mechanism drives the adjustment control rod to be inserted into or withdrawn from the fuel assembly; the safety control rod assembly includes a safety control rod and a safety control rod driving mechanism, and the safety control rod driving mechanism controls the safety control rod to be inserted into or withdrawn from the fuel assembly;

[0022] A reactor cock is arranged on the top of the reactor body container; the reactor cock includes a large cock, a middle cock and a small cock; the top of the reactor body container is open; the large cock is detachably rotatably sealed and connected to the top of the reactor body container, the middle cock is detachably rotatably sealed and connected to the large cock, and the small cock is detachably rotatably sealed and connected to the middle cock;

[0023] The regulating control rod driving mechanism passes through the center cock and is connected to the corresponding regulating control rod in the core; the safety control rod driving mechanism passes through the center cock and is connected to the corresponding safety control rod in the core.

[0024] As one of the feasible ways, the material of the reflector assembly is austenitic stainless steel, and the diameter of the reflector assembly is 2 to 3 times the mean free path of neutrons in the reactor core.

[0025] As one of the feasible ways, the fast reactor is a sodium-cooled fast reactor, and the mean free path of neutrons in the core of the sodium-cooled fast reactor is 10 cm.

[0026] As one of the feasible ways, the shielding components are made of ceramic boron carbide material, which can withstand high temperatures of 450 to 500°C and has a macroscopic neutron absorption cross section of 0.5 to 10 cm. -1 .

[0027] Beneficial technical effects of the present invention:

[0028] The fast reactor core of the present invention has a proliferation ratio in the core of 0.99-1.01, and utilizes the positive reactivity introduced by the proliferation characteristics of the fissile nuclide U-238 to compensate for the burnup reactivity loss during the operation of the reactor, thereby reducing the positive backup reactivity in the early stage of the reactor operation life, improving the operating safety of the reactor, and fundamentally reducing or even avoiding the risk of instantaneous supercriticality of the reactor; the compensating control rod assembly is cancelled, the number of openings of the reactor rotating shield plug is reduced, and the reliability of the primary circuit boundary operation is improved; the fuel assembly consists of depleted uranium fuel element rods and uranium-plutonium mixed fuel element rods, the depleted uranium fuel element rods are made of depleted uranium tails remaining from uranium enrichment in a pressurized water reactor, and the uranium-plutonium mixed fuel element rods are made of uranium-plutonium mixed fuel, thereby effectively improving the utilization rate of the depleted uranium fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the fuel assembly plan;

[0030] Figure 2 This is a schematic diagram of the axial direction of a depleted uranium fuel element rod;

[0031] Figure 3 This is a schematic diagram of the axial direction of the uranium-plutonium mixed fuel element rod;

[0032] Figure 4 This is a schematic diagram of the radial arrangement of the core;

[0033] Figure 5 This is a schematic diagram of the plan view of the reactor rotating shield plug;

[0034] Figure 6 It is a schematic diagram of the positions of the large cock and the middle cock;

[0035] Figure 7 This is a schematic diagram of the positions of the middle and small stopcocks;

[0036] Figure 8 It is a schematic diagram of the small cock structure;

[0037] Fig. 9 Schematic diagram of the reactor rotating shield plug structure.

[0038] In the figure, 1, small cock; 2, middle cock; 3, large cock; 4, control rod drive mechanism penetration piece; 5, control rod drive mechanism penetration piece coaxial line; 6, uranium-plutonium mixed fuel element rod; 7, depleted uranium fuel element rod; 8, first axial regeneration zone; 9, second axial regeneration zone; 10, core active zone; 11, third axial regeneration zone; 12, reactor body container; 13, fuel assembly; 14, reflector assembly; 15, first shielding assembly; 16, storage well assembly; 17, second shielding assembly; 18, adjustment control rod assembly; 19, safety control rod assembly. DETAILED DESCRIPTION

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of this application; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", "third", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0040] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0041] The technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings and specific embodiments.

[0042] A fast reactor is a reactor that uses fast neutrons to cause fission of nuclear fuel and maintain a chain reaction.

[0043] See also Figure 1 and 4 , this embodiment provides a fast reactor core, including a reactor body container 12 and a reactor core accommodated and supported in the reactor body container 12;

[0044] The core includes a fuel assembly 13, a reflector assembly 14, a first shielding assembly 15, a storage well assembly 16 and a second shielding assembly 17 which are radially arranged in sequence from the inside to the outside, and a control rod assembly arranged between the fuel assemblies 13. The arrangement area of ​​the fuel assembly 13 is the inner periphery of the core, and the arrangement area of ​​the first shielding assembly 15, the storage well assembly 16 and the second shielding assembly 17 is the outer periphery of the core.

[0045] The fuel assembly 13 is composed of depleted uranium fuel rods 7 and uranium-plutonium mixed fuel rods 6. The quantity ratio of the depleted uranium fuel rods 7 and the uranium-plutonium mixed fuel rods 6 is determined by the in-core proliferation ratio, which is 0.99-1.01.

[0046] The fast reactor core of the present invention has a core proliferation ratio of 0.99 to 1.01. The positive reactivity introduced by the proliferation characteristics of the fissile nuclide U-238 compensates for the burnup reactivity loss during the operation of the reactor, reduces the positive backup reactivity at the beginning of the reactor's operating life, improves the operating safety of the reactor, and fundamentally reduces or even avoids the risk of instantaneous supercriticality of the reactor.

[0047] In the fast reactor core of the present invention, the fuel assembly 13 is composed of depleted uranium fuel element rods 7 and uranium-plutonium mixed fuel element rods 6. The quantity ratio of the depleted uranium fuel element rods 7 and the uranium-plutonium mixed fuel element rods 6 is determined according to the proliferation ratio in the core of 0.99 to 1.01. The core is arranged in this way, the number of control rod assemblies in the core is reduced, and the residual reactivity of the core is reduced.

[0048] In the fast reactor core of the present invention, a circle of reflective layer assemblies 14 are radially arranged on the periphery of the fuel assembly 13, thereby reducing the core neutron leakage rate and improving the utilization rate of the core neutrons; two circles of shielding assemblies are arranged on the periphery of the core, thereby reducing the irradiation dose of the reactor body container 12 and extending the service life of the reactor body container 12; a storage well assembly 16 is arranged between the two circles of shielding assemblies for storing spent fuel assemblies. Since the spent fuel assemblies have high decay heat, they need to be stored in the storage well assembly 16 for a period of time before they can be unloaded from the core after the decay heat is reduced.

[0049] See also Figure 2-3 In this embodiment, as one of the achievable methods, the depleted uranium fuel element rod 7 and the uranium-plutonium mixed fuel element rod 6 are both cylindrical and have the same length and diameter;

[0050] A first axial regeneration zone 8 is axially arranged in the center of the depleted uranium fuel element rod 7, and the first axial regeneration zone 8 and the depleted uranium fuel element rod 7 share a central axis; a second axial regeneration zone 9, a core active zone 10 and a third axial regeneration zone 11 are axially arranged at equal intervals from top to bottom in the uranium-plutonium mixed fuel element rod 6, and the second axial regeneration zone 9, the core active zone 10, the third axial regeneration zone 11 and the uranium-plutonium mixed fuel element rod 6 share a central axis;

[0051] The first axial regeneration zone 8, the second axial regeneration zone 9, the core active zone 10 and the third axial regeneration zone 11 are all cylindrical and have the same diameter. The length of the first axial regeneration zone 8 is equal to the sum of the lengths of the second axial regeneration zone 9, the core active zone 10 and the third axial regeneration zone 11. The lengths of the second axial regeneration zone 9 and the third axial regeneration zone 11 are the same. The length of the core active zone 10 is equal to the sum of the lengths of the second axial regeneration zone 9 and the third axial regeneration zone 11.

[0052] The first axial regenerated zone 8 is composed of 0.25-0.7% by mass of U-235 and 99.3-99.75% by mass of U-238; the core active zone 10 is composed of 30-60% by mass of Pu-239 and 40-70% by mass of U-238; the second axial regenerated zone 9 and the third axial regenerated zone 11 are both composed of 0.25-0.7% by mass of U-235 and 99.3-99.75% by mass of U-238.

[0053] See also Figure 4 In this embodiment, as one of the feasible ways, the core is a regular hexagonal structure. The core is designed as a regular hexagonal structure, which can maximize the compactness of the core and reduce neutron leakage.

[0054] See also Figure 1 In this embodiment, as one of the achievable ways, the fuel assembly 13 is a regular hexagonal structure consisting of depleted uranium fuel rods 7 and uranium-plutonium mixed fuel rods 6 arranged alternately in layers, and the depleted uranium fuel rods 7 and uranium-plutonium mixed fuel rods 6 are arranged alternately in every other layer;

[0055] The quantity ratio of the depleted uranium fuel element rods 7 and the uranium-plutonium mixed fuel element rods 6 is determined by the in-core breeding ratio; the in-core breeding ratio is defined as the ratio of the generation rate of the fissile nuclide U-238 in the core to the consumption rate of the fissile nuclides U-235 and Pu-239 in the core, and its numerical expression is:

[0056] CR=

[0057] Among them, CR is the core proliferation ratio.

[0058] In this embodiment, as one of the achievable methods, determining the quantity ratio of the depleted uranium fuel element rods 7 and the uranium-plutonium mixed fuel element rods 6 according to the in-core breeding ratio includes the following steps:

[0059] Based on the average neutron energy of the fast reactor core, determine the microscopic radiation capture cross section of U-238, the microscopic absorption cross section of U-235 and the microscopic absorption cross section of Pu-239 through existing data or engineering experience;

[0060] According to the calculation formula of the in-core proliferation ratio, the number of nucleons of U-238, U-235 and Pu-239 in the fuel assembly 13 is determined;

[0061] The quantity ratio of the depleted uranium fuel rods 7 and the uranium-plutonium mixed fuel rods 6 is determined according to the nucleon numbers of U-238, U-235 and Pu-239 in the fuel assembly 13 and the mass percentages of U-238, U-235 and Pu-239 in the depleted uranium fuel rods 7 and the uranium-plutonium mixed fuel rods 6.

[0062] The following example illustrates how to determine the quantity ratio of the depleted uranium fuel element rods 7 and the uranium-plutonium mixed fuel element rods 6 based on the in-core breeding ratio.

[0063] Taking the fast reactor core with an average neutron energy of 0.1 MeV as an example, the microscopic radiation capture cross section of U-238 is 0.5 barns, the microscopic absorption cross section of U-235 is 1.5 barns, and the microscopic absorption cross section of Pu-239 is 2.5 barns; in order to make the in-core breeding ratio CR be 0.99 to 1.01, according to the calculation formula of the in-core breeding ratio CR, the number of nucleons of U-238 in the fuel assembly 13 is 4 times the sum of the number of nucleons of U-235 and Pu-239; assuming that the first axial blanket zone 8 It is composed of 0.25% by mass U-235 and 99.75% by mass U-238, the core active area 10 is composed of 60% by mass Pu-239 and 40% by mass U-238, the second axial regenerated area 9 and the third axial regenerated area 11 are both composed of 0.25% by mass U-235 and 99.75% by mass U-238, then the quantity ratio of the depleted uranium fuel element rod 7 and the uranium-plutonium mixed fuel element rod 6 is 3:1.

[0064] In this embodiment, as one of the feasible ways, the depleted uranium fuel element rods 7 are made of depleted uranium tailings left over from uranium enrichment in a pressurized water reactor, and the uranium-plutonium mixed fuel element rods 6 are made of uranium-plutonium mixed fuel, which effectively improves the utilization rate of the depleted uranium fuel.

[0065] In this embodiment, as one of the feasible ways, in the radial arrangement of the core, the number of fuel assemblies 13 must meet the minimum critical mass requirement of the reactor, that is, the total mass of the fissile nuclides U-235 and Pu-239 initially loaded in the core is greater than the minimum critical mass required for the critical and power operation of the reactor.

[0066] In core design, the core angle is the azimuth of the core and is used to describe the relative positions of the components inside the core. The core angle is described in a similar way to the direction in a plane coordinate system, usually with the core center as the origin and a fixed direction as the reference, and the angle is measured clockwise or counterclockwise.

[0067] The reactivity of the control rod assembly refers to the degree of influence of the control rods on the reactor reactivity as they move within the core. Specifically, it is through the control rods' ability to absorb neutrons that the reactor's reactivity is adjusted, thereby achieving control of the chain reaction.

[0068] The reactivity value of a control rod refers to the absolute value of the reactivity change caused by inserting a fully extended control rod into a core in a critical state under given conditions. It reflects the ability of the control rod to compensate for the reactivity effect and is an important parameter for measuring the control rod's ability to regulate reactivity in a reactor.

[0069] See also Figure 4 , in this embodiment, as one of the achievable methods, with the core center as the center of the circle, the east direction is 0° / 360°, the south direction is 270°, the west direction is 180°, and the north direction is 90°;

[0070] The control rod assembly is composed of a regulating control rod assembly 18 and a safety control rod assembly 19; the safety control rod assembly 19 is used to control the reactor to shut down safely; the regulating control rod assembly 18 is used to control the reactor core power;

[0071] A set of regulating control rod assemblies 18 are arranged at 90° and 270° directions of the core; the reactivity value of each set of regulating control rod assemblies 18 is 150-200 pcm, which ensures a certain core power regulation capability while reducing the maximum positive reactivity introduced in the event of a loss of control of the regulating control rod assemblies 18;

[0072] A group of safety control rod assemblies 19 are arranged at the core center, 45°, 135°, 225° and 315° directions respectively; the reactivity value of each group of safety control rod assemblies 19 is between 750 and 850 pcm, to ensure that even if the lifting rods of a group of safety control rod assemblies 19 with the largest reactivity value are stuck and cannot fall to the bottom of the core, the negative reactivity values ​​introduced by the remaining four groups of safety control rod assemblies 19 after the rods are dropped are still greater than 3000 pcm, to compensate for the positive reactivity introduced when the reactor goes from full power to cold shutdown and to ensure that the subcriticality after the reactor shutdown is greater than 1000 pcm.

[0073] See also Figure 5-9 In this embodiment, as one of the achievable ways, the adjustment control rod assembly 18 includes an adjustment control rod and an adjustment control rod driving mechanism, and the adjustment control rod driving mechanism drives the adjustment control rod to be inserted into or taken out of the fuel assembly 13; the safety control rod assembly 19 includes a safety control rod and a safety control rod driving mechanism, and the safety control rod driving mechanism controls the safety control rod to be inserted into or taken out of the fuel assembly 13;

[0074] A reactor cock is arranged on the top of the stack body container 12; the reactor cock comprises a large cock 3, a middle cock 2 and a small cock 1; the top of the stack body container 12 is open; the large cock 3 is detachably and rotatably connected to the top of the stack body container 12; the middle cock 2 is detachably and rotatably connected to the large cock 3, and the small cock 1 is detachably and rotatably connected to the middle cock 2;

[0075] The regulating control rod driving mechanism passes through the center cock 2 and is connected to the corresponding regulating control rod in the core, and is used to drive the corresponding regulating control rod to insert or withdraw the fuel assembly 13; the safety control rod driving mechanism passes through the center cock 2 and is connected to the corresponding safety control rod in the core, and is used to drive the corresponding safety control rod to insert or withdraw the fuel assembly 13 in the event of an accident.

[0076] In this embodiment, as one of the feasible ways, the material of the reflective layer assembly 14 is ordinary austenitic stainless steel, and the diameter of the reflective layer assembly 14 is 2 to 3 times the mean free path of neutrons in the reactor core.

[0077] In this embodiment, as one of the feasible ways, the fast reactor is a sodium-cooled fast reactor, and the mean free path of neutrons in the core of the sodium-cooled fast reactor is 10 cm.

[0078] In this embodiment, as one of the feasible methods, the shielding component is made of ceramic boron carbide material, which can withstand high temperatures of 450 to 500°C and has a macroscopic neutron absorption cross section of 0.5 to 10 cm. -1 .

[0079] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A fast reactor core, comprising a reactor body container (12) and a reactor core contained and supported in the reactor body container (12); the reactor core comprises a fuel assembly (13), a reflector assembly (14), a first shield assembly (15), a storage well assembly (16) and a second shield assembly (17) radially arranged in sequence from the inside to the outside, and a control rod assembly arranged between the fuel assemblies (13); characterized in that: The fuel assembly (13) is composed of depleted uranium fuel rods (7) and uranium-plutonium mixed fuel rods (6), and the quantity ratio of the depleted uranium fuel rods (7) to the uranium-plutonium mixed fuel rods (6) is determined by the in-core proliferation ratio; the in-core proliferation ratio is 0.99 to 1.

01.

2. The fast reactor core according to claim 1, characterized in that: The depleted uranium fuel element rod (7) and the uranium-plutonium mixed fuel element rod (6) are both cylindrical and have the same length and diameter; A first axial blanket region (8) is arranged axially in the center of the depleted uranium fuel rod (7), and the first axial blanket region (8) and the depleted uranium fuel rod (7) share a central axis; a second axial blanket region (9), a core active region (10), and a third axial blanket region (11) are arranged axially at equal intervals from top to bottom in the uranium-plutonium mixed fuel rod (6), and the second axial blanket region (9), the core active region (10), the third axial blanket region (11), and the uranium-plutonium mixed fuel rod (6) share a central axis; The first axial regenerated zone (8), the second axial regenerated zone (9), the core active zone (10) and the third axial regenerated zone (11) are all cylindrical and have the same diameter; the length of the first axial regenerated zone (8) is equal to the sum of the lengths of the second axial regenerated zone (9), the core active zone (10) and the third axial regenerated zone (11); the lengths of the second axial regenerated zone (9) and the third axial regenerated zone (11) are the same; and the length of the core active zone (10) is equal to the sum of the lengths of the second axial regenerated zone (9) and the third axial regenerated zone (11); The first axial regenerated zone (8) is composed of 0.25-0.7% by mass of U-235 and 99.3-99.75% by mass of U-238; the core active zone (10) is composed of (30-60)% by mass of Pu-239 and (40-70)% by mass of U-238; the second axial regenerated zone (9) and the third axial regenerated zone (11) are both composed of 0.25-0.7% by mass of U-235 and 99.3-99.75% by mass of U-238.

3. The fast reactor core according to claim 2, characterized in that: The core is a regular hexagonal structure; the fuel assembly (13) is a regular hexagonal structure consisting of depleted uranium fuel rods (7) and uranium-plutonium mixed fuel rods (6) arranged alternately in layers, and the depleted uranium fuel rods (7) and uranium-plutonium mixed fuel rods (6) are arranged alternately in every other layer; The quantity ratio of the depleted uranium fuel rods (7) and the uranium-plutonium mixed fuel rods (6) is determined by the in-core breeding ratio; the in-core breeding ratio is defined as the ratio of the generation rate of the fissile nuclide U-238 in the core to the consumption rate of the fissile nuclides U-235 and Pu-239 in the core, and its numerical expression is: CR= Among them, CR is the core proliferation ratio.

4. The fast reactor core according to claim 3, characterized in that: Determining the quantity ratio of depleted uranium fuel element rods (7) and uranium-plutonium mixed fuel element rods (6) according to the in-core breeding ratio comprises the following steps: Based on the average neutron energy of the fast reactor core, determine the microscopic radiation capture cross section of U-238, the microscopic absorption cross section of U-235 and the microscopic absorption cross section of Pu-239 through existing data or engineering experience; According to the calculation formula of the in-core proliferation ratio, the number of nucleons of U-238, U-235 and Pu-239 in the fuel assembly (13) is determined; The quantity ratio of the depleted uranium fuel rod (7) and the uranium-plutonium mixed fuel rod (6) is determined based on the nucleon numbers of U-238, U-235 and Pu-239 in the fuel assembly (13) and the mass percentages of U-238, U-235 and Pu-239 in the depleted uranium fuel rod (7) and the uranium-plutonium mixed fuel rod (6).

5. The fast reactor core according to claim 1, characterized in that: The depleted uranium fuel element rod (7) is made from the depleted uranium tails remaining from the uranium enrichment in a pressurized water reactor, and the uranium-plutonium mixed fuel element rod (6) is made from the uranium-plutonium mixed fuel.

6. The fast reactor core according to claim 1, characterized in that: In the radial arrangement of the core, the number of fuel assemblies (13) meets the minimum critical mass requirement of the reactor, that is, the total mass of the fissile nuclides U-235 and Pu-239 initially loaded in the core is greater than the minimum critical mass required for the criticality and power operation of the reactor.

7. The fast reactor core according to claim 1, characterized in that: With the core center as the center of the circle, the due east direction is 0° / 360°, the due south direction is 270°, the due west direction is 180°, and the due north direction is 90°; The control rod assembly is composed of a regulating control rod assembly (18) and a safety control rod assembly (19); the safety control rod assembly (19) is used to control the reactor to shut down safely; the regulating control rod assembly (18) is used to control the reactor core power; A set of regulating control rod assemblies (18) are arranged at 90° and 270° directions of the core; the reactivity value of each set of regulating control rod assemblies (18) is (150-200) pcm; A set of safety control rod assemblies (19) are arranged at the core center, 45°, 135°, 225° and 315° directions respectively; the reactivity value of each set of safety control rod assemblies (19) is (750-850) pcm.

8. The fast reactor core according to claim 7, characterized in that: The regulating control rod assembly (18) includes a regulating control rod and a regulating control rod driving mechanism, wherein the regulating control rod driving mechanism drives the regulating control rod to be inserted into or withdrawn from the fuel assembly (13); the safety control rod assembly (19) includes a safety control rod and a safety control rod driving mechanism, wherein the safety control rod driving mechanism controls the safety control rod to be inserted into or withdrawn from the fuel assembly (13); A reactor cock is arranged at the top of the reactor body container (12); the reactor cock comprises a large cock (3), a middle cock (2) and a small cock (1); the top of the reactor body container (12) is open; the large cock (3) is detachably rotatably sealed and connected to the top of the reactor body container (12); the middle cock (2) is detachably rotatably sealed and connected to the large cock (3); and the small cock (1) is detachably rotatably sealed and connected to the middle cock (2); The regulating control rod driving mechanism passes through the center cock (2) and is connected to the corresponding regulating control rod in the core; the safety control rod driving mechanism passes through the center cock (2) and is connected to the corresponding safety control rod in the core.

9. The fast reactor core according to claim 1, characterized in that: The material of the reflector assembly (14) is austenitic stainless steel, and the diameter of the reflector assembly (14) is 2 to 3 times the mean free path of neutrons in the reactor core.

10. The fast reactor core according to claim 1, characterized in that: The shielding components are made of ceramic boron carbide material, which can withstand high temperatures of 450-500°C and has a macroscopic neutron absorption cross section of 0.5-10 cm -1 .

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