阅读说明：本技术 一种适用于无源启动的紧凑型空间堆堆芯结构 (Compact type space reactor core structure suitable for passive start ) 是由 郑友琦 李梁喆 贾晓茜 王永平 曹良志 吴宏春 于 2021-06-04 设计创作，主要内容包括：本发明公开了一种适用于无源启动的紧凑型空间反应堆堆芯结构,该堆芯结构由燃料区和外部结构组成；燃料区由燃料棒、控制棒和冷却剂组成；燃料区分为内外两区,内区燃料弥散有一定质量分数的中子毒物用来展平径向功率分布；燃料棒采用高浓二氧化铀燃料和耐高温钼合金包壳；外部结构由交替布置的径向反射层和冷却剂通道以及源量程探测器组成,其中径向反射层一方面用来反射堆芯泄漏的中子,另一方面用于反应堆启动时与宇宙空间中的质子或α粒子作用产生中子,从而提高初始中子注量水平；源量程探测器选用灵敏型～(3)He正比计数管,4个源量程探测器沿径向90°对称布置在金属铍内侧。整体而言,该型空间反应堆堆芯具有结构紧凑、便于监测的特点。(The invention discloses a compact space reactor core structure suitable for passive start, which consists of a fuel area and an external structure; the fuel area consists of fuel rods, control rods and a coolant; the fuel area is divided into an inner area and an outer area, and neutron poison with a certain mass fraction is dispersed in the fuel of the inner area to flatten the radial power distribution; the fuel rod is cladded by high-concentration uranium dioxide fuel and high-temperature-resistant molybdenum alloy; the outer structure consists of radial reflecting layers and coolant channels which are alternately arranged and a source range detector, wherein the radial reflecting layers are used for reflecting neutrons leaked from the reactor core on one hand and are used for generating neutrons by the action of protons or alpha particles in the cosmic space when the reactor is started on the other hand, so that the neutrons are providedHigh initial neutron fluence levels; sensitive type for selecting source range detector 3 He proportional counting tube, 4 source range detectors are symmetrically arranged at the inner side of the metal beryllium along the radial direction by 90 degrees. On the whole, the reactor core of the space reactor has the characteristics of compact structure and convenience in monitoring.)

1. A compact space reactor core structure suitable for passive start-up which characterized in that: the core structure consists of a fuel area and an outer structure (4) covering the fuel area; in the fuel area, the fuel rods (1) are arranged in a hexagonal grid array, the control rods (2) are dispersedly arranged among the fuel rods (1), and the fuel rods (1) and the control rods (2) are filled with a coolant (3); the outer structure (4) consists of alternately arranged coolant channels (12) and radially reflecting layers (13) and a source range detector (14) arranged inside the radially reflecting layer (13) of the outer layer.

2. The compact space reactor core structure suitable for passive startup of claim 1, wherein: the fuel area is divided into an inner area and an outer area, wherein the inner area is composed of 141 fuel rods (1), and the outer area is composed of 510 fuel rods (1).

3. A compact space reactor core structure suitable for passive startup as claimed in claim 2 wherein: the fuel rod (1) of the inner zone and the outer zone has the same structure, the fuel rod (1) sequentially comprises a fuel pellet (5), an air gap (6) and a cladding (7) from inside to outside in the radial direction, air cavities (9) are arranged at two ends of the fuel pellet (5) along the axial direction, and an axial reflecting layer (8) is arranged at the outer end of each air cavity (9); the axial reflecting layer (8) is made of beryllium or beryllium oxide; helium is filled in the air cavity (9); the fuel pellet (5) of the fuel rod (1) of the inner zone is made of high-concentration uranium dioxide with the mass fraction of 90% and Gd with the mass fraction of 10%₂O₃The fuel pellet (5) of the fuel rod (1) in the outer region is made of high-concentration uranium dioxide, and the enrichment degree of the high-concentration uranium dioxide is greater than 90%; the material of the cladding (7) is high-temperature-resistant molybdenum alloy.

4. The compact space reactor core structure suitable for passive startup of claim 1, wherein: the outermost layer of the radial reflecting layer (13) is thicker than the inner layer; the radial reflecting layer (13) is made of metal beryllium.

5. The compact space reactor core structure suitable for passive startup of claim 1, wherein: the radial reflecting layer (13) is mainly composed of⁹The form of Be exists in the form of,⁹be reacts with proton or alpha particle in the cosmic space radiation field to generate neutron, and the specific reaction equation is as follows:

the (p, n) reaction section or the (alpha, n) reaction section is mainly concentrated in an energy interval of 1-100 MeV.

6. The compact space reactor core structure suitable for passive startup of claim 1, wherein: the source range detector (14) is selected from a sensitive type³He proportional counter tube, neutron fluence rate monitoring range is 10^-1n/(cm²s)～10⁵n/(cm²s), four source range detectors (14) are arranged in the whole stack, and are symmetrically arranged on the inner side of the radial reflecting layer (13) of the outer layer along the circumferential direction at 90 degrees.

7. The compact space reactor core structure suitable for passive startup of claim 1, wherein: the coolant (3) is helium-xenon mixed gas, wherein the mass fraction of helium is 17.5%.

Technical Field

The invention belongs to the technical field of nuclear reactor engineering, and particularly relates to a compact reactor core structure of a space reactor suitable for passive start.

Background

The space reactor is one of the optimal choices for solving the problem of energy supply of the spacecraft in the dark environment in the deep space, and has the characteristics of compact structure, high power density, long service life, strong environmental adaptability and the like. Common space reactor types include gas-cooled fast reactors, liquid metal cooled reactors, heat pipe reactors and the like, and compared with other reactor types of thermoelectric conversion systems, the gas-cooled fast reactors have higher cycle efficiency and smaller system weight and volume in combination with direct Brayton cycle systems. Space reactor core design generally requires that the volume of the core be compressed as much as possible without sacrificing the power capability of the core, thereby improving the propulsion performance of the spacecraft.

The existing reactor starting technology is that a neutron source is arranged in a reactor core and is used for increasing the initial neutron fluence level of the reactor core to the range which can be detected by a source range detector when the reactor is started. For special design requirements and operating environments of the space reactor, a passive starting method for improving the initial neutron fluence level can be adopted, namely, neutrons are generated by nuclear reaction of a reflecting layer structure material and protons or alpha particles in a cosmic space irradiation field. Compared with the traditional starting mode, the passive starting mode saves the volume occupied by the neutron source in the reactor, and avoids the complex system required by loading the neutron source component in the reactor starting process and the influence of decay of the neutron source on the reactor core safety in the emission stage. However, this passive start-up approach places new demands on the choice of reactor fuel arrangement and reflective layer materials.

Disclosure of Invention

In order to solve the above technical problems, an object of the present invention is to provide a compact reactor core structure suitable for passive startup, which improves the applicability of the reactor to the passive startup method through reasonable structural design and material selection.

In order to achieve the purpose, the invention adopts the following technical scheme:

a compact spatial reactor core structure suitable for passive startup, the core structure consisting of a fuel region and an outer structure 4 surrounding the fuel region; in the fuel area, the fuel rods 1 are arranged in a hexagonal grid array, the control rods 2 are dispersedly arranged among the fuel rods 1, and the fuel rods 1 and the control rods 2 are filled with the coolant 3; the outer structure 4 consists of alternately arranged coolant channels 12 and radially reflecting layers 13 and a source range detector 14 arranged inside the radially reflecting layer 13 of the outer layer.

The fuel area is divided into an inner area and an outer area, wherein the inner area is composed of 141 fuel rods 1, and the outer area is composed of 510 fuel rods 1.

The fuel rod 1 of the inner zone and the outer zone has the same structure, the fuel rod 1 sequentially comprises a fuel pellet 5, an air gap 6 and a cladding 7 from inside to outside in the radial direction, two ends of the fuel pellet 5 along the axial direction are provided with air cavities 9, and the outer ends of the air cavities 9 are provided with axial reflecting layers 8; the axial reflecting layer 8 is made of beryllium or beryllium oxide; helium is filled in the air cavity 9; the fuel pellet 5 material of the fuel rod 1 of the inner zone is high-concentration uranium dioxide with the mass fraction of 90 percent and Gd with the mass fraction of 10 percent₂O₃The fuel pellet 5 of the fuel rod 1 in the outer region is made of high-concentration uranium dioxide, and the enrichment degree of the high-concentration uranium dioxide is more than 90%; the material of the cladding 7 is high-temperature-resistant molybdenum alloy.

The outermost layer of the radial reflecting layer 13 is thicker than the inner layer; the material of the radial reflecting layer 13 is metallic beryllium.

The radial reflecting layer 13 is mainly composed of⁹The form of Be exists in the form of,⁹be reacts with proton or alpha particle in the cosmic space radiation field to generate neutron, and the specific reaction equation is as follows:

the (p, n) reaction section or the (alpha, n) reaction section is mainly concentrated in an energy interval of 1-100 MeV.

The source range detector 14 is selected from a sensitive type³He proportional counter tube, neutron fluence rate monitoring range is 10^-1n/(cm² s)～10⁵n/(cm²s), four source range detectors 14 are arranged in the whole stack, and are symmetrically arranged on the inner side of the radial reflecting layer (13) of the outer layer along the circumferential direction at 90 degrees.

The coolant 3 is helium-xenon mixed gas, wherein the mass fraction of helium is 17.5%.

Compared with the prior art, the invention has the following advantages:

1. compared with the traditional space gas-cooled fast reactor fuel arrangement, the fuel assembly has the advantages that the assembly box type design is eliminated, the fuel rods are compactly arranged in the reactor core in a hexagonal arrangement mode, and the volume of the reactor core is further reduced.

2. Compared with the traditional space gas-cooled fast reactor fuel arrangement, the fuel partition design is increased, and the dispersed neutron absorbing material Gd in the fuel core block of the inner zone₂O₃，Gd₂O₃The reactor core has strong thermal neutron absorption capacity and weak fast neutron absorption capacity, and can be used for suppressing the reactivity during a drop accident while flattening the radial power distribution of the reactor core.

3. Compared with the traditional reflecting layer structure of the space gas-cooled fast reactor, the metal beryllium is exposed and arranged on the outer side of the reactor core, so that the capability of producing neutrons under the action of the metal beryllium and cosmic particles is effectively improved, and the reflecting layer structure improves the applicability of the reactor to a passive starting mode.

Drawings

FIG. 1 is a schematic view of a spatial reactor core arrangement.

FIG. 2 is a schematic cross-sectional view of a fuel rod.

FIG. 3 is a schematic longitudinal cross-sectional view of a fuel rod.

Fig. 4 is a schematic view of a reflective layer structure.

FIG. 5 is a cosmic ray peak power spectrum measured at a high age of a certain solar activity.

FIG. 6 is a schematic diagram of a source range detector arrangement.

Detailed Description

The structure of the invention will be described in detail with reference to the accompanying drawings and specific embodiments.

As shown in fig. 1, a compact reactor core structure suitable for passive startup is composed of a fuel region and an outer structure 4 covering the fuel region; in the fuel area, the fuel rods 1 are arranged in a hexagonal grid array, the control rods 2 are dispersedly arranged among the fuel rods 1, and the rest areas are filled with the coolant 3; the outer structure 4 consists of a coolant channel 12, a radially reflective layer 13 and a source range detector 14.

Preferably, the coolant 3 is helium-xenon mixed gas, wherein the mass fraction of helium is 17.5%.

As shown in fig. 1, the fuel zone is divided into an inner zone and an outer zone, the number of the fuel rods 1 in the inner zone is 141, the number of the fuel rods 1 in the outer zone is 510, and the number of the control rods 2 is 10; the diameter of each fuel rod 1 is 13.0mm, the center distance between two adjacent fuel rods 1 is 14.2mm, and the diameter of each control rod 2 is 35.0 mm; the material of the control rod absorber is B₄C。

As shown in fig. 2, the fuel rod 1 comprises fuel pellets 5, an air gap 6 and a cladding 7 from inside to outside in the radial direction, wherein the outer diameter of the fuel pellets 5 is 10.9mm, the outer diameter of the air gap 6 is 11.0mm, and the outer diameter of the cladding 7 is 13.0 mm; the fuel rods 1 of the inner and outer zones adopt the same geometrical structure, and the material of the fuel pellet 5 of the fuel rod 1 of the inner zone is 90 mass percent of high-concentration uranium dioxide and 10 mass percent of Gd₂O₃The fuel pellet 5 of the fuel rod 1 in the outer region is made of high-concentration uranium dioxide, and the enrichment degree of the high-concentration uranium dioxide is more than 90%; helium is filled in the air gap 6; the material of the cladding 7 is a high temperature resistant molybdenum alloy.

As shown in fig. 3, the fuel rod 1 is axially composed of an axial reflecting layer 8, an air cavity 9 and a fuel pellet 5, wherein the length of the fuel segment is 483.6mm, and the length of the air cavity is 150 mm; the axial reflecting layer 8 is made of beryllium or beryllium oxide; the gas cavity 9 is filled with helium gas for containing fission gases.

As shown in fig. 4, the coolant channels 12 and the radially reflective layers 13 in the outer structure 4 are alternately arranged, wherein the thickness of the radially reflective layer 13 of the outermost layer is 71 mm; the radial reflecting layer 13 is made of metal beryllium; the radial reflection layer 13 reacts with protons or alpha particles in the space to generate neutrons (p, n) or (alpha, n), the reaction cross section is mainly concentrated in the energy interval of 1-100 MeV, when the sun is active for a long time, about 90% of the space radiation field is protons and 10% is alpha particles, and as shown in FIG. 5, the energy of the particles is also concentrated in the energy interval of 1-100 MeV.

As shown in fig. 6, four source-range detectors 14 are symmetrically arranged at 90 ° in the circumferential direction inside the outer radial reflecting layer 13, the metal beryllium of the material of the radial reflecting layer 13 has a large neutron scattering cross section, and the source-range detectors are arranged at this position, which is favorable for obtaining a higher neutron count rate; the source range detector 14 is selected from a sensitive type³He proportional counter tube, neutron fluence rate monitoring range is 10^-1n/(cm² s)～10⁵n/(cm²s); when the average particle fluence rate of cosmic rays reaches 1.3X 10⁵#/(cm²s), the neutron count rate at the detector position can reach the lowest detection range of the detector, and the source range detector 14 can monitor the core state.

The invention provides a compact reactor core structure of a space reactor suitable for passive start, which can compress the volume and the weight of the reactor core without sacrificing the power capacity of the reactor, and improve the neutron physical performance of the reactor core and the propulsion performance of a spacecraft.