WO2022206064A1

WO2022206064A1 - Reactor core system and gas-cooled micro reactor

Info

Publication number: WO2022206064A1
Application number: PCT/CN2021/142231
Authority: WO
Inventors: 张成龙; 刘国明; 袁媛; 张朔婷; 朱思阳; 董建华; 贺楷; 姚红; 肖会文; 李云龙
Original assignee: 中国核电工程有限公司
Priority date: 2021-03-29
Filing date: 2021-12-28
Publication date: 2022-10-06
Also published as: CN113270208A; CA3212782A1

Abstract

A reactor core system (6), comprising a reactor core, a reflective layer and a rotary drum control rod (2), wherein the reactor core, which is transversely arranged, comprises a plurality of fuel assemblies (1), and the plurality of fuel assemblies (1) are arranged according to a radial partition and in an axial layered manner; the reflective layer wraps outside the reactor core; the rotary drum control rod (2) is arranged in the reflective layer; a central graphite belt (5) is arranged in the reactor core, and the central graphite belt (5) is arranged in a vertical direction; an absorption body ball channel (4) is arranged in the central graphite belt (5), and the absorption body ball channel (4) is vertically arranged and penetrates the reflective layer; and an absorption body ball is arranged in the absorption body ball channel (4). The reactor core system (6) is small in size and convenient to transport.

Description

A core system and gas-cooled micro-reactor

The present disclosure claims the priority of a Chinese patent application with an application date of March 29, 2021, an application number of 202110333122.2, and the title of “A Modular Transverse Prismatic Gas-cooled Microreactor Core System”.

technical field

The invention belongs to the technical field of nuclear reactor engineering, and particularly relates to a core system and an air-cooled micro-reactor using the core system.

Background technique

The rapid economic development has increased the demand for energy, but traditional fossil fuels such as coal will bring serious environmental problems, which prompts countries to continuously explore and develop clean energy, optimize the existing energy structure, and reduce fossil fuel consumption. The proportion of fuel in energy. Among various types of new energy, nuclear energy has the advantages of cleanliness, high energy density, almost no greenhouse gas emissions, and low fuel transportation pressure. In recent years into the 21st century, nuclear energy has been continuously developed, becoming an important option to improve the energy structure, and has been further strengthened in the energy development strategy. By the end of September 2018, China's 44 reactors had reached a net installed capacity of 40.7 GWe, accounting for 10% of the world's installed nuclear power capacity, and China is also the country with the most nuclear power plants under construction.

At present, the existing high-temperature gas-cooled reactor designs all over the world are based on fixed non-moving cores, with a diameter of more than 5m and a height of more than 10m. They are large in size and suitable for use in nuclear power plants. At the same time, they need to be equipped with auxiliary systems. And there are many special safety facilities, which take up a lot of space. The components of the core need to be processed and manufactured in the factory in the early stage, and then transported separately to the application site. A large number of fuel assemblies, reflective layers, control rods and other components also require a long period of installation and debugging on site to achieve normal operation. It is difficult to meet the requirements of container transportation, simple assembly and rapid deployment in special application scenarios.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned defects in the prior art, the present disclosure provides a core system, which is small in size and convenient for transportation, and also provides a gas-cooled micro-stack using the above-mentioned core system, which is movable, flexible and High adaptability.

In a first aspect, the present disclosure provides a core system, which includes a fuel assembly, an absorber sphere, a reflector, and a rotating drum control rod, the fuel assemblies are laterally arranged, and the number of the fuel assemblies is multiple, and the multiple fuel assemblies are sequentially The core is arranged to form a core, the reflection layer is wrapped outside the core, the drum control rod is arranged in the reflection layer, and a central graphite strip is arranged in the core, the central graphite strip is vertically arranged, and Extending along the length direction of the core, the central graphite ribbon is provided with an absorber ball channel, the absorber ball channel is vertically arranged and penetrates the reflective layer, and the absorber ball is disposed in the absorber ball channel.

In a second aspect, the present disclosure also provides a gas-cooled micro-stack, including a core system and auxiliary equipment, where the core system adopts the above-mentioned core system.

Beneficial effects of the present disclosure compared to the prior art:

The overall shape of the core system provided by the present disclosure has a high degree of matching with the shape of the container, and by arranging the drum control rod and the vertically arranged absorber ball channel, the space occupied by the supporting auxiliary system can be reduced, and the core system can be reduced in size. The core system of this structure can be well arranged in a common container, which is convenient for transportation, and can meet the requirements of container transportation, simple assembly and rapid deployment in special application scenarios. And because the fuel assemblies and other components adopt a modular structure, they can be assembled in the factory, avoiding long-term installation and debugging at the installation site.

The gas-cooled micro-reactor provided by the present disclosure, due to the adoption of the above-mentioned core system, is small in size, can be easily moved, has high flexibility and adaptability, and can realize rapid deployment.

Description of drawings

FIG. 1 is a radial arrangement diagram of a fuel assembly containing combustible poison rods in a reactor core system according to an embodiment of the present disclosure;

Fig. 1a is a radial arrangement diagram of a fuel assembly without combustible poison rods in a core system according to an embodiment of the disclosure;

FIG. 2 is a radial arrangement diagram of the core at the position of the absorber ball channel in the embodiment of the present disclosure;

FIG. 3 is a radial arrangement diagram of the core at the position of the central graphite ribbon in the embodiment of the present disclosure;

4 is a schematic diagram of an axial cross-section of a central graphite ribbon in an embodiment of the present disclosure;

FIG. 5 is a burnup characteristic curve diagram of an air-cooled micro-reactor in an embodiment of the present disclosure;

FIG. 6 is a power distribution diagram of a zero burnup core assembly when a rotating drum control rod normalized based on the average power of the assembly is proposed according to an embodiment of the present disclosure;

FIG. 7 is a gas-cooled microstack in an embodiment of the present disclosure.

In the figure: 1. Fuel assembly; 2. Drum control rod; 3. Side reflection layer; 4. Absorber ball channel; 5. Central graphite belt; 6. Core system, 7. Car compartment; 8. Graphite block; 9 , helium gas storage tank; 10, helium fan 10; 11, instrument box; 12, drum control rod driving mechanism; 101, fuel rod; 102, coolant channel; 103, combustible poison rod; 104, beryllium oxide rod 11. The first fuel assembly; 12. The second fuel assembly.

Detailed ways

In order to make those skilled in the art better understand the technical solutions of the present disclosure, the present disclosure will be further described in detail below with reference to the accompanying drawings and embodiments.

Example 1

As shown in Figures 2-4, this embodiment discloses a modular transverse prismatic gas-cooled micro-reactor core system, including a fuel assembly 1, a rotating drum control rod 2, an absorber sphere, a reflection layer and other modules The reflection layer includes a front reflection layer, a rear reflection layer and a side reflection layer 3, and the front reflection layer, the rear reflection layer and the side reflection layer 3 together cover the core composed of the fuel assembly 1; the drum control rods 2 are arranged in The side reflection layer 3 ; the core is provided with a central graphite strip 5 ; the central graphite strip 5 is provided with an absorber ball channel 4 , and the absorber ball is arranged in the absorber ball channel 4 .

In this embodiment, the fuel assemblies 1 are arranged in 9 layers in the radial direction and in the axial direction. For the convenience of description, taking the center of the core as the origin, x represents the axial direction, y and z represent the radial direction, and there are 28 complete fuel assemblies arranged in the radial direction of the core, which are located at (1,1)(1,-1)(- 1, 1) (-1, -1) Four combustible poison rods 103 with a diameter of 1 cm and an absorber material of gadolinium are arranged in each of the fuel assemblies at four positions; on the radial diameter of y=0, 7 are arranged. A set of incomplete fuel assemblies, including 14

fuel rods

101 , 8

beryllium oxide rods

104 and 6 coolant passages 102 . The entire core has an axial length of 3.4m and a radial diameter of 2.1m.

A central graphite strip with a width of 8.4 cm is arranged at the position of y=0 in the center of the core, and five absorber ball channels with a radius of 3.9 cm are distributed along the axial x direction of the central graphite strip. There are 8 groups of control drums arranged in the reflective layer on the core side, and the absorber is a third ring with an inner diameter of 12.5 cm and an outer diameter of 14.5 cm. The rotating drum control rod is used to compensate for reactivity changes caused by temperature changes, xenon-samarium poisoning, burnup, etc., thermal shutdown, etc.; the absorber ball is used to further cool the core after the rotating drum control rod achieves thermal shutdown. , the core cold shutdown can also be achieved independently.

The number of fuel rods 101 in the fuel assemblies 1 close to the central graphite strip 5 is less than the number of fuel rods 101 in the fuel assemblies 1 farther from the central graphite strip 5 .

As shown in FIG. 1a, the fuel assembly 1 is provided with fuel rods 101, coolant channels 102 and beryllium oxide rods 104 that are regularly arranged in phases to enhance moderation. Specifically, fuel rod channels are provided in the fuel assembly 1. Arranged in the fuel rod passages, the coolant passages 102 are used for circulating coolant. Wherein, in some embodiments, as shown in FIG. 1 , combustible poison rods 103 may also be arranged in the fuel assembly 1 close to the central graphite strip 5 . The combustible poison rods 103 may adopt a separate arrangement; the coolant circulating in the coolant channel 102 may be a single-phase inert gas helium; the fuel assembly 1 may be a square graphite fuel assembly. Each fuel assembly 1 may have a side length of 21 cm and a height of 31 cm, including 24

fuel rods

101 and 9 coolant channels; as shown in FIG. 1 , if the combustible poison rods 103 are arranged, there are 12 beryllium oxide rods 104 with a diameter of 1 cm; as shown in FIG. 1a, if the combustible poison rods 103 are not arranged, there are 16 beryllium oxide rods 104 in the fuel assembly.

The fuel rods 101 are cylindrical, and each fuel rod contains a plurality of fuel pellets, preferably 8 fuel pellets are superimposed in the axial direction. Fuel pellets are formed by dispersing a plurality of coated fuel particles in a graphite or ceramic matrix. The structure of the fuel particle includes a fuel core and a multi-layer cladding layer, preferably a UO ₂ fuel core with an enrichment degree of 8.5% and a four-layer cladding layer structure. The fuel particle has a diameter of about a few Hundred microns; the fuel core material includes one or more of UO ₂ , UCO and UN; the cladding layer material includes one or more of graphite, SiC and ZrC. In this way, the fuel pellets are micro-packaged, specifically, ceramic micro-packages can be used, which can effectively prevent the release of fission products.

The material of the absorber (including the absorber ball and the absorber on the drum control rod) includes B ₄ C; the absorber ball not only includes the absorber material, but also includes a cladding covering the outside of the absorber material, and the cladding material includes stainless steel . The absorber on the drum control rod is in the shape of a partial ring.

In this embodiment, the material of the reflective layer includes graphite or BeO.

The reactor core in the technical solution of this embodiment is composed of square fuel assemblies, and the fuel type used is ceramic micro-encapsulated fuel, which can effectively prevent the release of fission products and prevent the fuel from being eroded; the coolant used is a single-phase inert gas helium Neutron moderators including graphite and BeO are also core structural materials and reflector materials, with large heat capacity, high temperature resistance, high thermal conductivity, high moderation ratio, and thermal neutron absorption cross section. The reactor core has the inherent safety of realizing automatic thermal shutdown by only relying on negative temperature feedback under accident conditions; the rotating drum control rods and absorber balls can not only effectively control the reactivity, ensure the core safety, but also save energy space, so that the core system and the reactor can be arranged in common containers for easy transportation.

The graphite core used in this embodiment has large heat capacity, slow temperature transient, can withstand very high temperatures, and has a large emergency operation time margin; the core power density is small, and has a strong negative temperature feedback, under accident conditions Even without any emergency measures, the reactor can be automatically thermally shut down by only relying on negative temperature feedback to physically avoid the possibility of core melting and radioactive material release. Modular design can simplify the system of nuclear power plants, reduce production costs, improve the quality of manufacturing components, can also reduce personnel operations and reduce the risk of accidents. The miniaturized design can further reduce the power and power density of the core, and improve the safety of the core.

Taking graphite as the core and reflector material, B ₄ C as the absorber material, and gadolinium as the combustible poison material as examples, the effect of this embodiment will be described in detail as follows:

The modular transverse prismatic gas-cooled micro-reactor core system proposed in this embodiment has a design life of 1 year and a design power of 5 MW. During the life, when the control rods are proposed, the radial power peak factor is about 1.25, and the axial power distribution is about 1.25. In the form of a cosine function, the axial power peak factor is about 1.29; the core has two sets of independent shutdown rod groups, which can realize cold shutdown and thermal shutdown; the core has strong negative temperature feedback and negative temperature reactivity The coefficient is at least -5pcm/K, and the huge temperature rise margin ensures that under accident conditions, even if the drum control rod and the absorber ball channel are completely unavailable, without any emergency measures, only relying on negative temperature feedback can also achieve automatic Shut down. The modular transverse prismatic gas-cooled micro-reactor core system has good core physical properties and superior inherent safety. The radial size of the core system is small, the drum control rods and the auxiliary system of the absorber ball occupy a small space, and can be arranged in the container for easy transportation and have a large market potential.

The modular transverse prismatic gas-cooled micro-reactor core system proposed in this embodiment can realize the reactor type with different power and different lifetimes through reasonable core fuel design and adjustment of parameters such as core size and fuel enrichment. design; the core size can be further reduced by increasing the fuel enrichment; the core power distribution can be optimized by the zonal arrangement of the fuel assembly enrichment at different locations; the reactivity can be achieved by adjusting the combustible poison and control rod arrangement The effective control of the modular transverse prismatic gas-cooled microreactor core system has superior design flexibility and environmental suitability.

In order to analyze the physical characteristics of the modular transverse prismatic gas-cooled micro-reactor core system in this embodiment, this embodiment uses a universal Mon-card program to model and analyze the gas-cooled micro-reactor with an assumed core temperature of 1200K. as follows:

The calculation results of the burnup characteristics of the gas-cooled micro-reactor are shown in Fig. 5. Under the thermal power of 5 MW, the core life of the gas-cooled micro-reactor is about 435 EFPD, which meets the design target of one-year life. During the lifetime, the maximum keff of the core is 1.01494, the minimum keff is 1.00410, and the residual reactivity variation is 1074pcm.

The core power distribution of the gas-cooled micro-reactor is shown in Fig. 6, which is a quarter of the in-core components normalized based on the average power of the components when the drum control rod 2 is fully withdrawn from the core with zero burnup. power distribution. In the radial direction, the power distribution is relatively uniform, and the radial power peak factor is about 1.25; in the axial direction, the power distribution is cosine function distribution, and the axial power peak factor is 1.29; the maximum power factor of the full stack assembly is 1.61, and the minimum is 0.53.

The inherent safety of the gas-cooled micro-reactor is mainly reflected in the core operation and shutdown in terms of physics, as follows:

(1) The core thermal shutdown relies on the rotating drum control rod. Assuming that the core temperature is 700K during thermal shutdown, considering the principle of sticking rods, the uncertainty of rod value is 10% (ie, the multiplier factor is 0.9), and the temperature decreases When the uncertainty of the induced positive reactivity is 10% (ie, the multiplier factor is 1.1), the drum control rod can provide at least -2117pcm thermal shutdown shutdown depth, which fully meets the -1000pcm shutdown depth requirement.

(2) The core emergency shutdown and cold shutdown rely on the absorber sphere. Assuming that the core temperature during cold shutdown is 300K, considering that the most valuable absorber sphere channel is unavailable and the value of the absorber sphere is uncertain 10 % (i.e., the multiplier factor is 0.9) and the uncertainty of the positive reactivity due to temperature reduction is 10% (i.e., the multiplier factor is 1.1), on the basis of the thermal shutdown of the drum control rod, the absorber sphere can provide at least ﹣10281pcm cold shutdown depth fully meets the ﹣1000pcm shutdown depth requirement.

(3) The maximum inherent safety of the gas-cooled micro-reactor is reflected in the accident condition, without any emergency measures, the core only relies on the negative feedback of temperature to realize the shutdown. Assuming that all the drum control rods and absorber ball channels are unavailable, the maximum core keff = 1.01494 and the residual reactivity is +1483pcm during the lifetime; and the total core temperature reactivity coefficient is between ﹣5pcm/K～﹣10pcm/ Between K, the reactor core temperature rises from the assumed 1200K to 1500K (about 1227°C) to achieve automatic shutdown; this temperature is much lower than the core fuel temperature limit (about 1600°C). Therefore, the modular transverse prismatic gas-cooled micro-reactor can achieve automatic shutdown even under accident conditions without any emergency measures and only relying on negative temperature feedback, which physically eliminates the possibility of core melting and radioactive material release. possibility.

Through the above settings, the radial diameter of the core can be reduced to 2.1m, and the auxiliary system required for the drum control rod 2 and the absorber ball occupies a small space, and can be placed in a common container with a side length of 2.5m, which is convenient for core transportation and flexible. Use, the market potential is large.

Example 2

As shown in FIGS. 2-4 , the present embodiment discloses a core system, which includes a core, a reflective layer, and a drum control rod 2 , wherein:

The core is arranged laterally, which includes a plurality of fuel assemblies 1, and the plurality of fuel assemblies 1 are arranged in a radially partitioned (or grouped) and axially layered manner, the reflective layer is wrapped outside the core, and the drum control rods 2 is arranged in the reflective layer, and the drum control rod 2 is used to compensate for reactivity changes, thermal shutdown, etc. caused by temperature changes, xenon-samarium poisoning, burn-up, etc.;

In addition, a central graphite belt 5 is arranged in the core, the central graphite belt 5 is arranged vertically, and an absorber ball channel 4 is arranged in the central graphite belt 5. The absorber ball channel 4 is vertically arranged and penetrates the reflective layer, and the absorber ball Absorber balls are arranged in the channel 4, and the absorber balls can be used to further cool down the core after the drum control rod 2 achieves thermal shutdown, or can independently achieve the cold shutdown of the core.

Through the above arrangement, not only the overall shape of the core system can be made into a horizontal cylindrical shape, but also the cylindrical core system is "short and long" compared with the conventional "high and short" shape of the core system. The shape of the container has a high degree of matching with the shape of the container, and it can also reduce the volume of the core system, which can facilitate the transportation of the container, so that the assembly can be completed in the processing plant, avoiding long-term installation and debugging on site, and meeting the container transportation in special application scenarios. , simple assembly, rapid deployment requirements.

Next, the core system of this embodiment will be described in further detail.

In this embodiment, the shape of the reflector is cylindrical, the radially outermost fuel assembly 1 in the core is connected to the inner wall of the reflector, and the shape of the core matches the shape of the interior wall of the reflector. The number of the absorber ball channels 4 may be one or multiple, and the plurality of absorber ball channels 4 are distributed along the length direction of the core.

The central graphite strip 5 is arranged in the middle of the core, so that the fuel assemblies 1 in the core can be divided into two symmetrically arranged areas, that is, divided into two groups, as shown in Fig. 2 and Fig. 3 , the two groups of fuel assemblies 1 Arranged on both sides of the central graphite strip 5 respectively, and each group of fuel assemblies 1 includes a first fuel assembly 11 (ie an incomplete fuel assembly) and a second fuel assembly 12 (ie a complete fuel assembly), wherein the first fuel assembly 11 is arranged close to the central graphite strip 5 , the second fuel assembly 12 is arranged on the other side of the first fuel assembly 11 and is located on both sides of the first fuel assembly 11 respectively with the central graphite strip 5 .

The fuel assembly 1 may be a square graphite fuel assembly. More specifically, as shown in FIG. 2 and FIG. 3 , the cross section of the first fuel assembly 11 may be a rectangle, the cross section of the second fuel assembly 12 may be a square, and the rectangular The length of the first fuel assembly 11 may be equal to the side length of the square second fuel assembly 12 , and the width of the two rectangular first fuel assemblies 12 plus the thickness of the central graphite strip 5 may be equal to the side of the square second fuel assembly 12 long for sorting. In fact, the first fuel assembly 11 can also be regarded as being formed by the central graphite ribbon 5 penetrating the second fuel assembly 12 . For the convenience of description, the center of the core is taken as the origin O, the axial direction (ie the length direction) of the cylindrical core is taken as the x-axis, and the radial direction of the cylindrical core is taken as the y-axis and the z-axis, wherein, Taking the radial direction in the horizontal direction as the y-axis and the radial direction in the vertical direction as the z-axis, the first fuel assemblies 11 in each group of fuel assemblies 1 are respectively arranged in a row along the z-axis direction. The second fuel assemblies 12 in 1 are arranged in sequence along the y-axis and the Z-axis. Specifically, the second fuel assemblies 12 in each group of fuel assemblies 1 are further divided into multiple groups, and the second fuel assemblies 12 in each group are respectively close to each other. A first fuel assembly 11 is sequentially arranged in multiple layers along the y-axis direction, and the outermost second fuel assemblies in each group of second fuel assemblies 12 are approximately on the same circumscribed circle.

Moreover, as shown in FIG. 2 and FIG. 3 , the reactor core may further include graphite blocks 8, the graphite blocks 8 have the same shape and size as the second fuel assemblies, and are arranged in one or more groups of second fuel assemblies, which are consistent with the second fuel assemblies. The individual fuel assemblies in the group of second fuel assemblies are aligned together to enhance the moderation effect.

In some embodiments, as shown in FIGS. 2 and 3 , the radial diameter of the core may be 2.1 m, the side length of the square second fuel assembly 12 and the length of the rectangular first fuel assembly 11 may be 21 cm, There may be 14 first fuel assemblies and 28 second fuel assemblies disposed in the core. The width (or thickness, that is, the thickness along the y-axis direction) of the central graphite strip 5 in the core can be 8.4 cm, and the central graphite strip 5 can be provided with 5 cylindrical absorber ball channels, 5 The absorbent ball channels 4 are arranged and distributed in parallel along the x-axis (ie, the axial direction or the longitudinal direction of the core). The radius of the absorber ball channel 4 may be 3.9 cm. The spacing between the absorbent ball channels 4 may be equal or unequal.

The first fuel assembly 11 and the second fuel assembly 12 are respectively divided into multiple layers along the length direction of the core.

In some embodiments, the axial length of the entire core may be 3.4 m, and the first fuel assembly 11 and the second fuel assembly 12 may be divided into 9 layers along the axial length of the core.

By dividing the core into a plurality of fuel assemblies 1 arranged along the y-axis and the z-axis (ie, radial divisions), and dividing each fuel assembly 1 into multiple layers (ie, axial stratification) in the axial direction of the core , which can improve the structural stability and earthquake resistance. Moreover, by independently setting the first fuel assembly and the second fuel assembly, the fuel assembly can be modularized, and each first fuel assembly and each second fuel assembly are equivalent to an independent module, which not only facilitates production and replacement, but also facilitates production and replacement. Simplify nuclear system design and emergency design.

The first fuel assembly 11 and the second fuel assembly 12 are provided with fuel rod passages, coolant passages 102, and beryllium oxide rods 104, and the fuel rod passages, coolant passages 102, and beryllium oxide rods 104 are distributed alternately, wherein, The fuel rod channel is used for setting the fuel rod 101 , the coolant channel 102 is used for circulating the coolant, and the coolant may specifically be a single-phase inert gas helium, and the beryllium oxide rod 104 is used for enhancing the moderation. Specifically, as shown in FIG. 1a, taking the square second fuel assembly 12 as an example, it can be divided into a plurality of grids of 7*7, and the coolant passages 102 are arranged on the central grid, and according to surrounding the central grid It is divided into three areas: the first layer, the second layer, and the third layer according to the distance from the center grid to the farthest, wherein: the fuel rod channels and the beryllium oxide rods 104 are alternately arranged in the first layer, and The grids where the fuel rod channels in the first layer are located are four grids next to the center grid; the coolant channels 102 and the fuel rod channels are alternately arranged in the second layer, and the fuel rod channels in the second layer are next to each other. The grid where the beryllium oxide rods 104 in the first layer are located; the fuel rod channels and the beryllium oxide rods 104 are alternately arranged in the third layer, and the grid where the fuel rod channels in the third layer are located is next to the coolant in the second layer The grid where the channels 102 are located, that is, the second fuel assembly 12 is provided with 24

fuel rods

101 , 9 coolant channels, and 16 beryllium oxide rods. Taking the rectangular first fuel assembly 11 as an example, it can be divided into multiple grids of 2*7, wherein the number of fuel rod channels is 7, the number of beryllium oxide rods 104 is 4, and the number of coolant channels is 4 The number of fuel rod channels is 6, and the fuel rod channels are arranged in a plurality of grids of 2*7, and at least one coolant channel 102 and one beryllium oxide rod 104 are arranged around each fuel rod channel.

The fuel rod 101 is cylindrical, and each fuel rod includes a plurality of fuel pellets, for example, may include 8 fuel pellets, and the 8 fuel pellets are arranged and stacked in sequence along the axial direction of the fuel rod.

The fuel pellets include fuel particles and a matrix in which the fuel particles are dispersed. The matrix can be graphite or ceramic, and the particle size of the fuel particles is on the order of a few hundred microns.

The fuel particles include a fuel core and a cladding layer, the fuel core is arranged in the cladding layer, and the cladding layer has a multi-layer structure, so that the fuel pellets can realize micro-encapsulation and can effectively prevent the release of fission products.

The material of the fuel core may include one or more of UO ₂ , UCO and UN, and the enrichment degree of the fuel core (ie, the mass fraction of U235) may be about 8.5%. Specifically, the cladding layer may have a four-layer structure, and the material of the cladding layer may include one or more of graphite, SiC and ZrC.

The second fuel assembly 12 may also be provided with combustible poison rods 103. Specifically, a square second fuel assembly 102 with a plurality of grids of 7×7 is taken as an example, as shown in FIG. Compared with the case of combustible poison rods, the difference is that the grids where the beryllium oxide rods 104 in the first layer are located are the combustible poison rods 103 instead of the beryllium oxide rods 104, that is, the second fuel assembly 12 is provided with There are 24

fuel rods

101, 9 coolant channels, 4 combustible poison rods, and 12 beryllium oxide rods.

The combustible poison rod 103 is a combustible poison rod which can be gadolinium as the absorber material.

The absorber ball and the drum control rod 2 both include an absorber and a casing, wherein: the absorber is made of B ₄ C material; the casing is made of stainless steel, which is wrapped outside the absorber.

The cross section of the absorber in the drum control rod 2 may be in the shape of a partial ring, for example, a third of the ring, the inner diameter of the ring may be 12.5 cm, and the outer diameter may be 14.5 cm.

The reflective layer can be made of graphite or BeO material, and it can specifically include an upper reflective layer, a lower reflective layer, and a side reflective layer 3, wherein the upper reflective layer and the lower reflective layer are respectively arranged in each fuel assembly 1. At both ends of the core, side reflectors 3 are provided on the periphery of the fuel assemblies 1 arranged in the outermost layers. The rotating drum control rods 2 are arranged in the side reflection layer 3 , and the number of the rotating drum control rods 2 is multiple, specifically 8, and the 8 rotating drum control rods 2 are evenly distributed.

The overall shape of the core system of this embodiment has a high degree of matching with the shape of the container, and by setting the drum control rod and the vertically arranged absorber ball channel, the space occupied by the supporting auxiliary system can be reduced, and the core system can be reduced. Therefore, the radial diameter of the core system can be reduced to 2.1m, and it can be arranged in a common container with a side length (width) of 2.5m, which is convenient for transportation. In this way, the assembly can be completed in the factory, avoiding long-term installation and debugging on site , which can meet the requirements of container transportation, simple assembly and rapid deployment in special application scenarios.

In addition, by using square fuel assemblies, the arrangement of the device can be facilitated, and the stability and shock resistance can be improved; the fuel type used is ceramic micro-encapsulated fuel, which can effectively prevent the release of fission products and avoid fuel erosion; by setting the drum control rod and The absorber sphere makes the core have two sets of independent shutdown rod groups, which can realize cold shutdown and thermal shutdown; since the core structural material and reflector material are graphite or BeO, it can be used as a neutron moderator, And it has the advantages of large heat capacity, high temperature resistance, high thermal conductivity, high moderation ratio, small thermal neutron absorption cross section, etc., slow temperature transient, can withstand high temperature, large emergency operation time margin, core power Low density and strong negative temperature feedback (take graphite as the core and reflector material, B ₄ C as the absorber material, and gadolinium as the combustible poison material, for example, the temperature negative reactivity coefficient is at least -5pcm/K above), the temperature rise margin is huge. Under accident conditions, even if the drum control rod and the absorber ball channel are completely unavailable, without any emergency measures, the automatic thermal shutdown can be realized only by relying on the negative temperature feedback. Physically Avoid the possibility of core melting and radioactive material release, and improve inherent safety; the core system is small in size and can be miniaturized design, which can reduce the power and power density of the core and improve the safety of the core; The core system can facilitate modular design, thereby simplifying the nuclear power plant system, reducing production costs, improving the manufacturing quality of components, reducing personnel operations, and reducing the risk of accidents.

This embodiment also discloses a gas-cooled micro-stack, as shown in FIG. 7 , which includes the above-mentioned core system 6 and auxiliary equipment.

Specifically, the auxiliary tools include a helium gas storage tank 9, a helium gas blower 10, an instrument box 11, a drum control rod driving mechanism 12, and the like. In this embodiment, the air-cooled micro-stack is arranged in a carriage 7 of a transportation tool for transportation, wherein the carriage 7 may be a container.

The gas-cooled micro-reactor of this embodiment adopts the above-mentioned core system, which is small in size and movable, and has high flexibility and adaptability, and can realize rapid deployment.

In addition, the core system of this embodiment has good core physical properties and superior inherent safety. For this reason, this embodiment uses a universal Mon-card program to model and analyze the gas-cooled micro-reactor with an assumed core temperature of 1200K. , and the physical properties of the core are as follows:

The core power distribution of the gas-cooled micro-reactor is shown in Figure 6, which is a quarter-core component power distribution normalized based on the average power of the components when zero burnup and the control rods are fully drawn out of the core . In the radial direction, the power distribution is relatively uniform, and the radial power peak factor is about 1.25; in the axial direction, the power distribution is cosine function distribution, and the axial power peak factor is 1.29; the maximum power factor of the full stack assembly is 1.61, and the minimum is 0.53.

It should be understood that the above embodiments are merely exemplary implementations adopted to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also regarded as the protection scope of the present disclosure.

Claims

A core system, characterized in that it includes a core, a reflective layer, and a rotating drum control rod, the core is arranged laterally, and includes a plurality of fuel assemblies, and the plurality of fuel assemblies are radially partitioned and axially layered The reflective layer is arranged outside the core, the drum control rod is arranged in the reflective layer, and the core is provided with a central graphite strip, the central graphite strip is arranged vertically, and the central graphite strip is arranged in the vertical direction. An absorber ball channel is arranged in the belt, the absorber ball channel is vertically arranged and penetrates the reflective layer, and the absorber ball channel is provided with an absorber ball.
The core system according to claim 1, wherein the reflection layer is cylindrical, the fuel assembly in the radially outermost layer in the core is in contact with the inner wall of the reflection layer, and the fuel assembly is in contact with the inner wall of the reflection layer. is square.
The reactor core system according to claim 2, wherein the central graphite ribbon is arranged in the middle of the reactor core, so that the fuel assemblies in the reactor core are divided into two groups arranged symmetrically, and the two groups of fuel assemblies are respectively arranged in the middle of the reactor core. On both sides of the central graphite strip, each group of fuel assemblies includes a first fuel assembly and a second fuel assembly, the first fuel assembly is arranged at a position close to the central graphite strip, and the second fuel assembly Arranged on the other side of the first fuel assembly and with the central graphite ribbon on both sides of the first fuel assembly, respectively.
The core system according to claim 3, wherein the first fuel assembly and the second fuel assembly are divided into multiple layers along the length direction of the core.
The core system according to claim 3, wherein the first fuel assembly and the second fuel assembly are provided with fuel rod passages, coolant passages, and beryllium oxide rods, and the fuel rods are The passages, the coolant passages, and the beryllium oxide rods are distributed alternately, wherein the fuel rod passages are used for arranging the fuel rods, the coolant passages are used for circulating the coolant, and the beryllium oxide rods are used for enhancing the moderation.
The reactor core system according to claim 5, wherein the second fuel assembly is further provided with combustible poison rods.
The reactor core system according to claim 5, wherein the fuel rods are cylindrical, and each fuel rod includes a plurality of fuel pellets, and the plurality of fuel pellets are arranged and stacked in sequence along the axial direction of the fuel rods ; The coolant is a single-phase inert gas helium.
8. The core system of claim 7, wherein the fuel pellets include fuel particles and a matrix, wherein the fuel particles are dispersed in the matrix.
The reactor core system according to claim 8, wherein the matrix is graphite or ceramics; the fuel particles comprise a fuel core and a cladding layer, the fuel core is arranged in the cladding layer, And the coating layer is a multi-layer structure.
The reactor core system according to claim 9, wherein the material of the fuel core comprises one or more of UO 2 , UCO and UN; the material of the cladding layer comprises graphite, SiC and ZrC one or more of them.
The core system according to any one of claims 1-10, wherein the absorber ball and the drum control rod both comprise an absorber and a cladding, and the absorber is made of B 4 C material The cladding shell is made of stainless steel, which is wrapped around the absorbent body.
The core system according to any one of claims 1-10, wherein the reflection layer is made of graphite or BeO material.
The core system according to any one of claims 1-10, wherein the reflection layer comprises a front reflection layer, a rear reflection layer and a side reflection layer, and the drum control rod is arranged on the side reflection layer , the absorber in the drum control rod is in the shape of a partial ring.
A gas-cooled micro-stack, comprising a core system and auxiliary equipment, wherein the core system adopts the core system according to any one of claims 1-13.