A fast reactor core

Abstract

The present invention specifically relates to a fast reactor core, belonging to the technical field of fast reactor cores, and includes a reactor body container and a core accommodated and supported within the reactor body container; the core includes a fuel assembly, a reflector assembly, a first shielding assembly, a storage well assembly, and a second shielding assembly that are arranged radially from the inside to the outside in sequence, as well as 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 breeding ratio within the core; the breeding ratio within the core is 0.99 to 1.01. For the fast reactor core of the present invention, the reactivity increased by the newly bred fissile nuclides within the core is used to balance the burnup reactivity damage during the subsequent reactor operation, fundamentally eliminating the prompt supercritical safety risk brought about by excessive excess reactivity.

Description

Technical Field

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

[0002] In the core design scheme of existing fast reactors, a relatively large number of compensation control rod assemblies are arranged to control the high excess reactivity of the reactor. During the operation of the unit, by continuously adjusting the axial position of the compensation control rods, positive reactivity is released 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 in the rotating shield of the reactor to arrange the compensation control rod drive mechanism to drive the axial movement of the compensation control rods; on the other hand, the reactor needs to reserve a large amount of excess reactivity in the initial design to balance the burnup reactivity loss during the subsequent reactor operation, which increases the prompt supercritical safety risk caused by the uncontrolled lifting of the compensation control rods during the unit operation. Summary of the Invention

[0003] The object of the present invention is to provide a fast reactor core. By utilizing the characteristics of a hard neutron energy spectrum in a fast reactor, with an internal breeding ratio close to 1.0, the compensation control rod assemblies in the core are cancelled, and the reactivity increased by the newly bred fissile nuclides in the core is used to balance the burnup reactivity damage during the subsequent reactor operation. This can reduce the number of openings in the reactor rotating shield, improve the operation reliability of the primary circuit boundary, and fundamentally eliminate the prompt supercritical safety risk caused by excessive excess reactivity.

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

[0005] A fast reactor core includes a reactor body container and a core accommodated and supported in the reactor body container; the core includes a fuel assembly, a reflector assembly, a first shielding assembly, a storage well assembly, and a second shielding assembly arranged radially from the inside to the outside in sequence, 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 internal breeding ratio of the core; the internal breeding ratio of the core is 0.99 to 1.01.

[0006] As one achievable manner, both the depleted uranium fuel element rods and the uranium-plutonium mixed fuel element rods are cylindrical and have the same length and diameter;

[0007] A first axial regeneration zone is axially centered inside the depleted uranium fuel element rod, and the first axial regeneration zone and the depleted uranium fuel element rod share the same central axis; second axial regeneration zones, a core active zone, and a third axial regeneration zone are axially arranged at equal intervals from top to bottom inside the uranium-plutonium mixed fuel element rod, and the second axial regeneration zones, the core active zone, the third axial regeneration zone, and the uranium-plutonium mixed fuel element rod share the same 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 regeneration zone is composed of U-235 with a mass percentage of 0.25% to 0.7% and U-238 with a mass percentage of 99.3% to 99.75%. The core active zone is composed of Pu-239 with a mass percentage of 30% to 60% and U-238 with a mass percentage of 40% to 70%. Both the second axial regeneration zone and the third axial regeneration zone are composed of U-235 with a mass percentage of 0.25% to 0.7% and U-238 with a mass percentage of 99.3% to 99.75%.

[0010] As one possible implementation, the core is a regular hexagon structure; the fuel assembly is a regular hexagon structure composed of depleted uranium fuel element rods and uranium-plutonium mixed fuel element rods arranged alternately in layers. The depleted uranium fuel element rods and the uranium-plutonium mixed fuel element rods are arranged alternately every other layer;

[0011] The quantity ratio of the depleted uranium fuel element rods and the uranium-plutonium mixed fuel element rods is determined by the breeding ratio in the core; the breeding ratio in the core is defined as the ratio of the production 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] where CR is the breeding ratio in the core.

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

[0015] According to the average neutron energy of the fast reactor core, determine the microscopic radiative 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 breeding ratio calculation formula in the core, determine the number of nucleons of U-238, U-235, and Pu-239 in the fuel assembly 13;

[0017] Determine the quantity ratio of depleted uranium fuel element rods and uranium-plutonium mixed fuel element rods 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 element rods and uranium-plutonium mixed fuel element rods.

[0018] As one of the realizable ways, the depleted uranium fuel element rods are made from the depleted uranium tails remaining after uranium enrichment in a pressurized water reactor, and the uranium-plutonium mixed fuel element rods are made from uranium-plutonium mixed fuel.

[0019] As one of the realizable ways, in the radial arrangement of the reactor 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 reactor core is greater than the minimum critical mass required for reactor criticality and power operation.

[0020] As one of the realizable ways, with the center of the reactor core 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 consists of an adjustment 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 adjustment control rod assembly is used to control the power of the reactor core; one set of adjustment control rod assemblies is arranged in the 90° and 270° directions of the reactor core respectively, and the reactivity worth of each set of adjustment control rod assemblies is between 150 and 200 pcm; one set of safety control rod assemblies is arranged in the directions of the reactor core center, 45°, 135°, 225°, and 315° respectively, and the reactivity worth of each set of safety control rod assemblies is between 750 and 850 pcm.

[0021] As one of the realizable ways, the adjustment control rod assembly includes an adjustment control rod and an adjustment control rod drive mechanism, and the adjustment control rod drive mechanism drives the adjustment control rod to insert into or withdraw from the fuel assembly; the safety control rod assembly includes a safety control rod and a safety control rod drive mechanism, and the safety control rod drive mechanism controls the safety control rod to insert into or withdraw from the fuel assembly;

[0022] A reactor plug is provided at the top of the reactor vessel body; the reactor plug includes a large plug, a medium plug, and a small plug; there is an opening at the top of the reactor vessel body; the large plug is detachably and rotationally sealed to the top of the reactor vessel body, the medium plug is detachably and rotationally sealed to the large plug, and the small plug is detachably and rotationally sealed to the medium plug;

[0023] The adjustment control rod drive mechanism passes through the medium plug and then is connected to the corresponding adjustment control rod in the reactor core; the safety control rod drive mechanism passes through the medium plug and then is connected to the corresponding safety control rod in the reactor core.

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

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

[0026] As one of the realizable ways, the shielding component is made of ceramic boron carbide material, which can withstand high temperatures of 450 to 500 °C, and the macroscopic neutron absorption cross section is 0.5 to 10 cm -1 。

[0027] Advantageous technical effects of the present invention:

[0028] For the fast reactor core of the present invention, the breeding ratio in the core is 0.99 to 1.01. The positive reactivity introduced by utilizing the breeding characteristics of the fissionable nuclide U-238 compensates for the burnup reactivity loss during the operation of the reactor, reduces the positive reserve reactivity at the initial stage of the reactor operation life, improves the operation safety of the reactor, and fundamentally reduces or even avoids the prompt supercritical risk of the reactor; the compensation control rod assembly is cancelled, the number of openings in the rotating shielding plug of the reactor is reduced, and the reliability of the operation of the primary loop boundary is improved; the fuel assembly is composed of depleted uranium fuel element rods and uranium-plutonium mixed fuel element rods. The depleted uranium fuel element rods are made of depleted uranium tailings remaining from the uranium enrichment of pressurized water reactors, and the uranium-plutonium mixed fuel element rods are made of uranium-plutonium mixed fuel, effectively improving the utilization rate of depleted uranium fuel. Description of the Drawings

[0029] Figure 1 It is a schematic plan view of the fuel assembly;

[0030] Figure 2 It is an axial schematic view of the depleted uranium fuel element rod;

[0031] Figure 3 It is an axial schematic view of the uranium-plutonium mixed fuel element rod;

[0032] Figure 4 It is a schematic view of the radial layout of the core;

[0033] Figure 5 It is a schematic plan view of the rotating shielding plug of the reactor;

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

[0035] Figure 7 It is a schematic view of the positions of the middle plug and the small plug;

[0036] Figure 8 It is a schematic view of the structure of the small plug;

[0037] Figure 9 It is a schematic structural diagram of a reactor rotating shield plug.

[0038] In the figure, 1. small plug; 2. medium plug; 3. large plug; 4. through-piece of control rod drive mechanism; 5. coaxial line of through-piece of control rod drive mechanism; 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 main body container; 13. fuel assembly; 14. reflector assembly; 15. first shielding assembly; 16. storage well assembly; 17. second shielding assembly; 18. regulating control rod assembly; 19. safety control rod assembly. Specific embodiments

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

[0040] Reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments.

[0042] A fast reactor is a reactor that causes nuclear fuel fission by fast neutrons and maintains a chain reaction.

[0043] See Figure 1 and 4 , this embodiment provides a fast reactor core, including a reactor main body container 12 and a core accommodated and supported in the reactor main 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 that are arranged radially from the inside to the outside in sequence, 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 areas of the first shielding assembly 15, the storage well assembly 16, and the second shielding assembly 17 are the outer periphery of the core.

[0045] 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 by the internal breeding ratio of the core, and the internal breeding ratio of the core is 0.99 to 1.01.

[0046] For the fast reactor core of the present invention, with the internal breeding ratio of the core being 0.99 to 1.01, the positive reactivity introduced by utilizing the breeding characteristics of the fissionable nuclide U-238 compensates for the burnup reactivity loss during the operation of the reactor, reduces the positive excess reactivity at the initial stage of the reactor operation life, improves the operation safety of the reactor, and fundamentally reduces or even avoids the prompt supercritical risk of the reactor.

[0047] For 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 internal breeding ratio of the core being 0.99 to 1.01. By arranging the core in this way, the number of control rod assemblies in the core is reduced, and the residual reactivity of the core is decreased.

[0048] For the fast reactor core of the present invention, a circle of reflector assemblies 14 is arranged radially outside the fuel assembly 13, reducing the neutron leakage rate of the core and improving the utilization rate of neutrons in the core; two circles of shielding assemblies are arranged outside the core, reducing the irradiation dose of the reactor vessel 12 and extending the service life of the reactor vessel 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 a relatively high decay heat, they need to be stored in the storage well assembly 16 for a period of time until the decay heat decreases before they can be unloaded from the core.

[0049] See Figure 2-3 , in this embodiment, as one of the realizable ways, both the depleted uranium fuel element rods 7 and the uranium-plutonium mixed fuel element rods 6 are cylindrical and have the same length and diameter;

[0050] A first axial regeneration zone 8 is axially centered inside the depleted uranium fuel element rod 7, and the first axial regeneration zone 8 and the depleted uranium fuel element rod 7 share the same central axis; second axial regeneration zones 9, a core active zone 10, and third axial regeneration zones 11 are arranged at equal intervals axially from top to bottom inside the uranium-plutonium mixed fuel element rod 6, and the second axial regeneration zones 9, the core active zone 10, the third axial regeneration zones 11, and the uranium-plutonium mixed fuel element rod 6 share the same 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 regeneration zone 8 is composed of U-235 with a mass percentage of 0.25 - 0.7% and U-238 with a mass percentage of 99.3 - 99.75%. The core active zone 10 is composed of Pu-239 with a mass percentage of 30 - 60% and U-238 with a mass percentage of 40 - 70%. Both the second axial regeneration zone 9 and the third axial regeneration zone 11 are composed of U-235 with a mass percentage of 0.25 - 0.7% and U-238 with a mass percentage of 99.3 - 99.75%.

[0053] See Figure 4 , in this embodiment, as one of the achievable ways, the core is a regular hexagonal structure. Designing the core as a regular hexagonal structure can maximize the compactness of the core and reduce neutron leakage.

[0054] See Figure 1 , in this embodiment, as one of the achievable ways, the fuel assembly 13 is a regular hexagonal structure composed of depleted uranium fuel element rods 7 and uranium-plutonium mixed fuel element rods 6 arranged alternately by layer. The depleted uranium fuel element rods 7 and the uranium-plutonium mixed fuel element rods 6 are arranged alternately 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 breeding ratio in the core. The breeding ratio in the core is defined as the ratio of the generation rate of the fissionable nuclide U-238 in the core to the consumption rate of the fissile nuclides U-235 and Pu-239 in the core. Its numerical expression is:

[0056] CR =

[0057] where CR is the breeding ratio in the core.

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

[0059] According to the average neutron energy of the fast reactor core, determine the microscopic radiative 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 breeding ratio calculation formula in the reactor core, determine the number of nucleons of U-238, U-235, and Pu-239 in the fuel assembly 13;

[0061] According to the number of nucleons 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 element rod 7 and the uranium-plutonium mixed fuel element rod 6, determine the quantity ratio of the depleted uranium fuel element rod 7 and the uranium-plutonium mixed fuel element rod 6.

[0062] The following is an example to illustrate how to determine the quantity ratio of the depleted uranium fuel element rod 7 and the uranium-plutonium mixed fuel element rod 6 according to the breeding ratio in the reactor core.

[0063] Taking a fast reactor core with an average neutron energy of 0.1 MeV as an example, the microscopic radiative 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 breeding ratio CR in the reactor core be 0.99 - 1.01, according to the breeding ratio CR calculation formula in the reactor core, 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 breeding zone 8 is composed of 0.25% U-235 and 99.75% U-238 by mass percentage, the core active zone 10 is composed of 60% Pu-239 and 40% U-238 by mass percentage, and both the second axial breeding zone 9 and the third axial breeding zone 11 are composed of 0.25% U-235 and 99.75% U-238 by mass percentage, 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 realizable ways, the depleted uranium fuel element rod 7 is made of depleted uranium tailings remaining from the uranium enrichment of a pressurized water reactor, and the uranium-plutonium mixed fuel element rod 6 is made of uranium-plutonium mixed fuel, effectively improving the utilization rate of depleted uranium fuel.

[0065] In this embodiment, as one of the realizable ways, in the radial arrangement of the reactor core, the number of fuel assemblies 13 needs to 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 reactor core is greater than the minimum critical mass required for reactor criticality and power operation.

[0066] In reactor core design, the core angle is the azimuth angle of the reactor core, used to describe the relative positions of the internal components of the reactor core; the description method of the core angle is similar to describing directions in a plane coordinate system, usually taking the center of the reactor core as the origin and a certain fixed direction as the reference, and measuring the angle clockwise or counterclockwise.

[0067] The reactivity of the control rod assembly refers to the degree of influence on the reactor reactivity when the control rod moves within the reactor core. Specifically, it regulates the reactor reactivity by the ability of the control rod to absorb neutrons, thereby achieving the control of the chain reaction.

[0068] The reactivity worth of a control rod refers to the absolute value of the reactivity change caused by inserting a fully withdrawn control rod into a critical reactor core 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 reactivity regulation ability of the control rod in the reactor.

[0069] See Figure 4 , in this embodiment, as one of the achievable ways, taking the center of the reactor core 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°;

[0070] The control rod assembly consists 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 safe shutdown of the reactor; the regulating control rod assembly 18 is used to control the power of the reactor core;

[0071] One set of regulating control rod assemblies 18 is arranged in the 90° and 270° directions of the reactor core respectively; the reactivity worth of each set of regulating control rod assemblies 18 is between 150 and 200 pcm, which can ensure a certain reactor core power regulation ability while reducing the maximum positive reactivity introduced in the accident of the uncontrolled withdrawal of the regulating control rod assembly 18;

[0072] One set of safety control rod assemblies 19 is arranged at the center, 45°, 135°, 225° and 315° directions of the reactor core respectively; the reactivity worth of each set of safety control rod assemblies 19 is between 750 and 850 pcm, so as to ensure that even if the rod lifting of the set of safety control rod assemblies 19 with the largest reactivity worth is stuck and cannot fall to the bottom of the reactor core, the negative reactivity worth introduced after the remaining four sets of safety control rod assemblies 19 fall is still greater than 3000 pcm, to compensate for the positive reactivity introduced by the reactor from full power to cold shutdown and ensure that the subcriticality after the reactor shutdown is greater than 1000 pcm.

[0073] See Figure 5-9 , in this embodiment, as one of the achievable ways, the regulating control rod assembly 18 includes a regulating control rod and a regulating control rod drive mechanism, and the regulating control rod drive mechanism drives the regulating control rod to insert into or withdraw from the fuel assembly 13; the safety control rod assembly 19 includes a safety control rod and a safety control rod drive mechanism, and the safety control rod drive mechanism controls the safety control rod to insert into or withdraw from the fuel assembly 13;

[0074] A reactor cock is provided at the top of the reactor body container 12; the reactor cock includes a large cock 3, a medium cock 2, and a small cock 1; the top of the reactor body container 12 is open; the large cock 3 is detachably and rotationally sealed to the top of the reactor body container 12; the medium cock 2 is detachably and rotationally sealed to the large cock 3, and the small cock 1 is detachably and rotationally sealed to the medium cock 2;

[0075] The regulating control rod drive mechanism passes through the medium cock 2 and is connected to the corresponding regulating control rod in the reactor core for driving the corresponding regulating control rod to insert into or withdraw from the fuel assembly 13; the safety control rod drive mechanism passes through the medium cock 2 and is connected to the corresponding safety control rod in the reactor core for driving the corresponding safety control rod to insert into or withdraw from the fuel assembly 13 in case of an accident.

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

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

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

[0079] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A fast reactor core, comprising a reactor body container (12) and a core accommodated and supported within the reactor body container (12); the core includes a fuel assembly (13), a reflector assembly (14), a first shield assembly (15), a storage well assembly (16), and a second shield assembly (17) arranged radially from the inside to the outside in sequence, and a control rod assembly arranged between the fuel assemblies (13); characterized in that, The reactor core has a regular hexagonal structure; the fuel assembly (13) is a regular hexagonal structure composed of depleted uranium fuel element rods (7) and uranium-plutonium mixed fuel element rods (6) arranged alternately in layers, and the depleted uranium fuel element rods (7) and uranium-plutonium mixed fuel element rods (6) are arranged alternately every other layer; the quantity ratio of the depleted uranium fuel element rods (7) and the uranium-plutonium mixed fuel element rods (6) is determined by the breeding ratio in the reactor core; the breeding ratio in the reactor core is 0.99 to 1.

01.

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

3. The fast reactor core according to claim 2, characterized in that, The quantity ratio of the depleted uranium fuel element rods (7) and the uranium-plutonium mixed fuel element rods (6) is determined by the breeding ratio in the reactor core; the breeding ratio in the reactor core is defined as the ratio of the generation rate of the fissile nuclide U-238 in the reactor core to the consumption rate of the fissile nuclides U-235 and Pu-239 in the reactor core, and its numerical expression is: where CR is the breeding ratio in the reactor core.

4. The fast reactor core according to claim 3, characterized in that, Determining the quantity ratio of the depleted uranium fuel element rods (7) and the uranium-plutonium mixed fuel element rods (6) according to the breeding ratio in the reactor core includes the following steps: According to the average neutron energy of the fast reactor core, determine the microscopic radiative 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 breeding ratio calculation formula in the reactor core, determine the number of nucleons of U-238, U-235, and Pu-239 in the fuel assembly (13); Determine the quantity ratio of depleted uranium fuel element rods (7) and uranium-plutonium mixed fuel element rods (6) 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 element rods (7) and uranium-plutonium mixed fuel element rods (6).

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

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

7. The fast reactor core according to claim 1, characterized in that, Taking the center of the reactor core 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 consists of an adjusting control rod assembly (18) and a safety control rod assembly (19); the safety control rod assembly (19) is used to control the safe shutdown of the reactor; the adjusting control rod assembly (18) is used to control the power of the reactor core. One set of adjusting control rod assemblies (18) is arranged in the 90° and 270° directions of the reactor core respectively; the reactivity worth of each set of adjusting control rod assemblies (18) is in the range of (150 - 200) pcm. One set of safety control rod assemblies (19) is arranged in the directions of the center of the reactor core, 45°, 135°, 225°, and 315° respectively; the reactivity worth of each set of safety control rod assemblies (19) is in the range of (750 - 850) pcm.

8. The fast reactor core according to claim 7, characterized in that, The adjusting control rod assembly (18) includes an adjusting control rod and an adjusting control rod drive mechanism, and the adjusting control rod drive mechanism drives the adjusting control rod to insert into or withdraw from the fuel assembly (13); the safety control rod assembly (19) includes a safety control rod and a safety control rod drive mechanism, and the safety control rod drive mechanism controls the safety control rod to insert into or withdraw from the fuel assembly (13). A reactor plug is provided at the top of the reactor vessel body (12); the reactor plug includes a large plug (3), a medium plug (2), and a small plug (1); there is an opening at the top of the reactor vessel body (12); the large plug (3) is detachably and rotationally sealed and connected to the top of the reactor vessel body (12); the medium plug (2) is detachably and rotationally sealed and connected to the large plug (3), and the small plug (1) is detachably and rotationally sealed and connected to the medium plug (2). The adjusting control rod drive mechanism passes through the medium plug (2) and then is connected to the corresponding adjusting control rod in the reactor core; the safety control rod drive mechanism passes through the medium plug (2) and then is connected to the corresponding safety control rod in the reactor 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 - 3 times the average free path of neutrons in the reactor core.

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

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