WO2022206072A1

WO2022206072A1 - Gas-cooled micro-reactor core and gas-cooled micro-reactor

Info

Publication number: WO2022206072A1
Application number: PCT/CN2021/142915
Authority: WO
Inventors: 袁媛; 刘国明; 张成龙; 汪俊
Original assignee: 中国核电工程有限公司
Priority date: 2021-03-29
Filing date: 2021-12-30
Publication date: 2022-10-06
Also published as: CN113270205B; CA3212783A1; SA523450776B1; CN113270205A

Abstract

A gas-cooled micro-reactor core, comprising a reflecting layer, fuel units, and a control rod assembly (2), wherein the control rod assembly (2) and the fuel units are all arranged in the reflecting layer, a plurality of fuel units are provided, each fuel unit comprises a pressure pipe (8) and a fuel assembly (1), the fuel assembly (1) is arranged in the pressure pipe (8) so as to make the pressure pipe (8) act as a pressure bearing boundary of the reactor core, and the control rod assembly (2) is arranged outside the pressure pipe (8). The reactor core is easy to mount, and solves the problems of many elements to be transported, a complex assembly, and a slow response to deployment of a high-temperature gas-cooled reactor.

Description

A gas-cooled micro-reactor core 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 202110332498.1, and the title of “A Modular Pressure Tube Gas-cooled Microreactor Core”.

technical field

The present disclosure belongs to the field of nuclear industry, and in particular relates to an air-cooled micro-reactor core and an air-cooled micro-reactor including the air-cooled micro-reactor core.

Background technique

Energy is an important foundation for social and economic development, and the increasingly prominent problem of environmental pollution poses a higher challenge to the optimization of the energy structure. As a clean, stable and high power density new energy, nuclear energy is the best candidate for baseload power. The safety of nuclear power has always been the focus of the general public, and it is also the direction of the efforts of nuclear power researchers. Especially after the Fukushima accident in Japan, more and more attention has been paid to the safe use of nuclear energy, and the design and development of various advanced nuclear energy systems has been accelerated.

High temperature gas-cooled reactor, as one of the advanced reactor types of the fourth generation nuclear energy system, has attracted much attention due to its good inherent safety and high coolant outlet temperature. Its superior inherent safety is mainly reflected in the use of TRISO-coated fuel particles, which can effectively prevent the release of fission products and the erosion of fuel; the graphite core has large heat capacity, slow temperature transients, and can withstand high temperatures. The emergency operation time margin is large; the core power density is small, and it has a strong negative temperature feedback. Under accident conditions, even without any emergency measures, the reactor can be shut down by the negative temperature feedback.

In addition, the modular high-temperature gas-cooled reactor can reduce many emergency facilities and simplify the design of nuclear power plants through reasonable design and optimization, and it is also economically competitive. Especially for some remote areas that cannot be reached by the power grid, diesel power generation costs are high and pollution is high, while small modular high-temperature gas-cooled reactors can supply power safely, stably and cleanly, and can well meet the energy needs of such areas.

At present, the existing high temperature gas-cooled reactor designs all over the world are based on stationary immobile cores. 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 an air-cooled micro-stack core and an air-cooled micro-stack including the air-cooled micro-stack core, which can meet the requirements of fast transportation and easy assembly .

In a first aspect, the present disclosure provides a gas-cooled micro-reactor core, comprising a reflective layer, a fuel unit and a control rod assembly, wherein the control rod assembly and the fuel unit are both arranged in the reflective layer, and the fuel unit adopts A plurality of each fuel unit includes a pressure tube and a fuel assembly, the fuel assembly being arranged within the pressure tube so that the pressure tube acts as a pressure-bearing boundary of the core, and the control rods are arranged outside the pressure tube.

Preferably, a plurality of fuel units are arranged in multiple layers from the inside to the outside, the control rod assemblies are multiple, and each control rod assembly is arranged outside the outermost fuel unit, and/or is arranged in any layer of the fuel unit , and/or, arranged between two adjacent layers of fuel units.

Preferably, in each pressure tube, the fuel assembly includes a graphite block and a fuel rod, the graphite block is provided with a fuel rod channel, and the fuel rod is arranged in the fuel rod channel.

Preferably, the fuel assembly further comprises a combustible poison rod, a combustible poison channel is further provided in the graphite block, and the combustible poison rod is arranged in the combustible poison rod channel.

Preferably, the fuel rod includes a plurality of fuel pellets, and the plurality of fuel pellets are stacked along the length of the core; the fuel pellets include fuel particles and a matrix, and the fuel particles are dispersed in the matrix .

Preferably, the fuel particles include a fuel core and a cladding layer covering the fuel core.

Preferably, the fuel assembly further includes a coolant flow channel, the coolant flow channel includes one or more of a first coolant flow channel, a second coolant flow channel, and a third coolant flow channel, The first coolant flow channel is provided between the fuel rod and the inner wall of the fuel rod channel of the graphite block, the second coolant flow channel is provided in the fuel rod, and the third coolant The flow channels are arranged in the graphite block and are regularly arranged between the fuel rod channels and/or the combustible poison channels.

Preferably, the core further includes an inner tube, the inner tube is arranged in the pressure tube and is wrapped outside the fuel assembly, and the coolant flow channel further includes a fourth coolant flow channel, so the fourth coolant flow channel is arranged between the inner tube and the pressure tube and communicates with the first coolant flow channel and/or the second coolant flow channel and/or the third coolant flow channel, respectively, The coolant flows in from the fourth coolant flow channel, and after the reflective layers meet, flows out from the first coolant flow channel and/or the second coolant flow channel and/or the third coolant flow channel.

Preferably, the fuel unit further includes a moderator material jacket, the moderator material jacket is jacketed outside the pressure pipe; the control rod assembly is arranged adjacent to the fuel unit, and includes a body, A control rod, a control rod channel is provided in the body, and the control rod is arranged in the control rod channel.

Preferably, the fuel unit further includes a moderating material jacket, the moderating material jacket is jacketed outside the pressure pipe, and a control rod hole is arranged in the moderating material jacket, and the control rod assembly includes A main body and a control rod, wherein the main body is the jacket of the moderating material, and the control rod is arranged in the control rod hole, so that the control rod assembly and the fuel unit form a whole.

In a second aspect, the present disclosure also provides a gas-cooled micro-stack including the above-described gas-cooled micro-stack core.

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

1. In the present disclosure, the fuel assembly is put into the pressure tube, and the pressure tube is pressurized to form a modular structure, and a modular pressure tube assembly can be obtained, which is easy to install, and solves the problem of many high-temperature gas-cooled reactor transportation components, complex assembly, Respond to slow deployment issues.

2. Through the design of pressure tube components, long-term on-site assembly is avoided, and the convenience of transportation, assembly and deployment of each component is improved; moreover, the core has superior inherent safety, design flexibility, environmental adaptability and The convenience of transportation and assembly has great market potential in the fields of power supply in remote mountainous areas, aerospace, island power supply, and deep sea power supply.

3. By setting the inner tube, a fourth coolant flow channel as the coolant inlet can be formed between the pressure tube and the inner tube. After the pressure tube is cooled by the inlet coolant, the core temperature outside the pressure tube is low, which can be reduced Control rods and other components are required to withstand high temperature. In addition, the graphite jacket and reflective layer graphite outside the pressure tube can also be replaced by moderator materials with better moderator performance but lower working temperature, such as beryllium oxide, hydrogenated Zirconium, yttrium hydride and other materials can further reduce the size of the core.

Description of drawings

FIG. 1 is a schematic structural diagram of one of the gas-cooled micro-stack cores in an embodiment of the disclosure.

FIG. 2 is a schematic structural diagram of another gas-cooled micro-stack core in an embodiment of the disclosure.

FIG. 3 is an enlarged schematic view of a part of the structure in FIG. 2 .

FIG. 4 is a schematic diagram of an axial section of FIG. 2 .

FIG. 5 is a schematic diagram of the grouping of control rods in the core of FIG. 2 .

FIG. 6 is a schematic structural diagram of a control rod in an embodiment of the present disclosure.

FIG. 7 is a graph showing a burnup characteristic of an air-cooled micro-stack in an embodiment of the present disclosure.

FIG. 8 is a normalized component power distribution diagram of a zero burnup core of an air-cooled micro-reactor in an embodiment of the present disclosure when control rods are raised.

FIG. 9 is a graph showing the change of fuel temperature coefficient of the air-cooled micro-reactor under different burnup points and different temperatures in the embodiment of the present disclosure;

10 is a graph showing the variation curve of the temperature coefficient of the core graphite of the gas-cooled micro-reactor under different burn-up points and different temperatures in an embodiment of the disclosure;

FIG. 11 is a graph showing the change of the temperature coefficient of the reflective layer graphite of the air-cooled micro-stack under different burn-up points and different temperatures in an embodiment of the disclosure.

In the figure: 1, fuel assembly; 2, control rod assembly; 3, side reflector; 4, control rod hole; 5, fuel pellet; 6, coolant flow channel; 7, poison rod; 8, pressure pipe; 9 , inner tube; 10, control rod; 11, control rod cladding.

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 FIGS. 1 and 2 , the present disclosure provides a modular pressure tube gas-cooled micro-reactor core, including a fuel assembly 1 , a reflector, a control rod assembly 2 , and a pressure tube 8 .

The reflective layer completely covers the fuel assembly 1 and the control rod assembly 2, which can be made of graphite material, and can specifically include an upper reflective layer, a lower reflective layer and a side reflective layer 3, the upper reflective layer and the lower reflective layer are respectively in the fuel. At both ends of the assembly and the control rod assembly, the side reflectors 3 are located on the side of the fuel assembly and the control rod assembly.

As shown in FIG. 3 , the fuel assembly 1 is put into the pressure tube 8 , so that the pressure tube 8 serves as the pressure-bearing boundary of the core, and the reflective layer and the control rod assembly 2 are installed outside the pressure tube 8 . The fuel assembly 1 includes a graphite block and a fuel rod; the graphite block is provided with a fuel rod channel, the fuel rod is arranged in the fuel rod channel in the graphite block, and a coolant flow channel 6 is formed between the fuel rod and the graphite block (the first cooling The first coolant flow channel is used to circulate the coolant; the cross section of the fuel rod can be annular, so that a coolant flow channel (second coolant flow channel) is formed in the fuel rod (center), and the second coolant flow channel is formed in the fuel rod (center). The coolant flow channel is also used to circulate the coolant.

In some embodiments, independent coolant channels (third coolant flow channels) may also be provided on the graphite block. Specifically, the third coolant flow channels and the fuel rod channels may be arranged in a certain interval, for example, A plurality of fuel rod channels are arranged around a third coolant flow channel, and the third coolant flow channel may be arranged along the graphite block or along the length of the fuel assembly, also for the flow of the coolant.

That is, the coolant flow channel in the core of this embodiment may include one or more of the first coolant flow channel, the second coolant flow channel, and the third coolant flow channel.

In some embodiments, the core may further include an inner tube 9 , the coolant flow channel may further include a fourth coolant flow channel, and the inner tube 9 is arranged in the pressure tube 8 and covers the outside of the fuel assembly, that is, the inner tube 9 It is located between the pressure pipe 8 and the fuel assembly 1, and a gap is left between the inner pipe 9 and the pressure pipe 8 to form a fourth coolant flow channel between the pressure pipe 8 and the inner pipe 9, and the top/ A gap is left between the bottom and the upper/lower reflective layer, and the fourth coolant flow passage and the first coolant flow passage and/or the second coolant flow passage and/or the third coolant flow passage pass through the fuel assembly. The gaps between the top/bottom and the upper/lower reflective layers are respectively connected, and the coolant flows in from the coolant flow channel 6 (ie, the fourth coolant flow channel) between the pressure tube 8 and the inner tube 9, and is reflected at the top The layer (ie upper reflective layer) or the bottom reflective layer (ie lower reflective layer) merges from the inner and outer sides of the fuel rod composed of the superposition of fuel pellets 5 in the fuel hole (ie fuel rod channel) in the fuel assembly 1. Any one or more of the coolant flow passages (ie, the first coolant flow passage and the second coolant flow passage), and the third coolant flow passages flow out.

The fuel rod includes a plurality of fuel pellets 5 superimposed along the axial direction (or the length direction of the core); the fuel pellets 5 are formed by dispersing fuel particles in a silicon carbide matrix, that is, the fuel pellets include fuel particles and a matrix, and The base body is made of silicon carbide material. The fuel particles include a fuel core and a four-layer cladding layer structure wrapped around the fuel core; the fuel core is uranium dioxide, and the cladding layer structure is high-temperature ceramics, that is, the fuel particles are ceramic fuel particles.

In this embodiment, the fuel particles used are ceramic fuel particles, which can effectively prevent the release of fission products and prevent the fuel from being eroded; the coolant used is helium, a single-phase inert gas; and the graphite block is both a neutron moderator, It is also a core structural material and a reflective layer material, and has the advantages of large heat capacity, high temperature resistance, high thermal conductivity, high moderation ratio, and small thermal neutron absorption cross section. At the same time, the use of annular fuel elements (fuel rods) can further improve the safety or economy of the reactor.

A fuel assembly 1 is arranged in each pressure tube 8, and a graphite jacket (ie, a jacket of moderating material) is arranged outside the pressure tube 8, so that the pressure tube can be pressurized to form a modular structure, and a modularized pressure tube assembly can be obtained. (or called pressure tube combustion assembly), the gas-cooled micro-reactor core composed of pressure tube-type components as the main components is the modular pressure-tube gas-cooled micro-reactor core.

In the design of the pressure tube assembly in this embodiment, the pressure-bearing boundary of the core can be the pressure tube 8 of the fuel assembly 1, and the reflective layer, control rods and other components are not within the pressure boundary, which improves the performance of the reflective layer and control rods. Ease of disassembly and transportation of components. At the same time, by arranging the inner tube, a fourth coolant flow channel as the coolant inlet can be formed between the pressure tube and the inner tube. After the pressure tube is cooled by the inlet coolant, the core temperature outside the pressure tube 8 is lower, which can Reduce the high temperature resistance requirements of components such as control rods. In addition, the graphite of the outer core of the pressure tube 8 (such as the graphite jacket) and the graphite of the reflective layer can also be replaced by moderator materials with better moderation performance but lower working temperature, such as beryllium oxide, zirconium hydride, etc. The core size can be further reduced.

Specifically, in some embodiments, when the modular pressure tube gas-cooled micro-reactor core of the present disclosure adopts a small pressure tube type fuel assembly, for example, when the inner diameter of the pressure tube is 20 cm, as shown in FIG. 1 As shown, the fuel assembly 1, the pressure pipe 8 and the moderating material jacket together form a fuel assembly unit (also referred to as a fuel unit in Embodiment 2); the control rod assembly 2 is provided separately outside the fuel assembly unit, which includes a body and a The body of the control rod can be made of graphite material, the body is provided with a control rod channel, and the control rod 10 is arranged in the control rod channel on the body of the control rod assembly 2; the control rod assembly 2 is arranged adjacent to the fuel assembly unit. In FIG. 1 , each fuel assembly unit is adjacent to at least one control rod assembly 2 . The outlines of the cross-section of the body of the control rod assembly 2 and the cross-section of the moderating material jacket (ie, the graphite jacket) can both be regular hexagons for arrangement.

Specifically, in other embodiments, when the modular pressure tube gas-cooled micro-reactor core of the present disclosure adopts a large pressure tube fuel assembly, for example, when the inner diameter of the pressure tube is 54 cm, the As shown in 2-4, a control rod hole 4 is provided in the moderated material jacket outside the pressure tube 8, the control rod assembly 2 includes a main body and a control rod, and the control rod 10 is arranged in the control rod hole 4 of the moderated material jacket. In order to make the control rod 10 and the fuel assembly 1 form a whole, at this time, it is not necessary to set the control rod assembly 2 separately, and the moderating material jacket with the control rod hole 4 is equivalent to the control rod as shown in FIG. The body in component 2. In this embodiment, the pressure pipes 8 may be in a group of 7, wherein 6 pressure pipes at the periphery are arranged around one pressure pipe at the center. The outline of the cross-section of the graphite jacket (ie, the moderating material jacket) is a regular hexagon, and each graphite jacket can be provided with three control rod channels 4, and the control rod channels 4 are distributed in the graphite jacket at intervals. Near the three vertices of the hexagonal section.

As shown in FIG. 2 , taking the number of pressure tubes 8 as an example, the fuel assemblies 1 in the pressure tubes 8 can be divided into two zones (a central zone and a peripheral zone) in the radial direction of the core. One pressure pipe and its internal fuel assemblies are arranged in the area, and the other six pressure pipes and their internal fuel assemblies are arranged in the surrounding area, and are distributed annularly around the periphery of the central area. The axial direction of the core can be arranged in 6 layers (that is, there are 6 stacked fuel assemblies 1 in each pressure tube 8). There are 42 fuel blocks (fuel assemblies 1) in the whole stack. The size and structure of each fuel block and other characteristics may be substantially the same. Wherein, a combustible poison channel may also be provided at the edge position of the fuel assembly 1 in the central area of the core, and a combustible poison rod (ie, poison rod 7) is provided in the combustible poison channel. The number of combustible poison channels in this embodiment can be 6, that is, 6 combustible poison rods 7 are arranged at the edge position of the fuel assembly 1 in the central region of the core. The axial height of the entire core can be 2.7m, and the radial diameter can be 2.6m.

In some embodiments, the fuel assemblies 1 in the central region of the control rods may be arranged in one group, and the fuel assemblies 1 in the peripheral regions may be arranged in three groups, as shown in FIG. 5 . The control rod group located in the center of the core can have only 3 rod-shaped control rods, and the other 3 groups of control rods located in the peripheral 6 fuel assembly areas can each have 6 rod-shaped control rods.

Specifically, as shown in FIG. 5 , the control rods in the control rod holes 4 of each group of pressure pipes 8 are divided into the zeroth control rod group (CR0), the first control rod group (CR0), the first A control rod group (CR1), a second control rod group (CR2), and a third control rod group (CR3). The zeroth control rod group is a group of control rods located in the center of the core, with 3 rod-shaped control rods; the first to third control rod groups are located around the pressure tube at the periphery of the core, and each group has 6 rod-shaped control rods The rods are distributed in concentric circles and are distributed from near to far away from the center of the core.

The zeroth control rod group and the first control rod group can be used as the shutdown rod group for emergency shutdown and cold shutdown of the core; the second control rod group and the third control rod group can be used as starting rods and adjustment rods. It is used to compensate for reactivity changes, thermal shutdown, etc. caused by temperature changes, xenon-samarium poisoning, burn-up, etc.

As shown in FIG. 6 , the outside of the control rod 10 of the control rod assembly 2 is covered with a control rod cladding 11 .

In order to analyze the physical characteristics of the above-mentioned modular pressure-tube gas-cooled micro-reactor core, this embodiment uses a general Mon-card program to analyze the gas in the above-mentioned modular pressure-tube gas-cooled micro-reactor core assuming a core temperature of 1200K. The cold micro-reactor is used for modeling and calculation analysis, as follows:

The calculation results of the burnup characteristics of the gas-cooled micro-reactor are shown in Figure 7. Under the thermal power of 5MW, the core life of the gas-cooled micro-reactor is about 650EFPD, which meets the design target of 1.5 years of life. The arrangement of combustible poisons not only effectively reduces the residual reactivity of the core, but also does not cause reactivity penalty, and does not affect the life of the core.

The core power distribution of the gas-cooled micro-reactor is shown in Figure 8, which is the normalized component power distribution based on the average power when there is 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 1.21; in the axial direction, the power distribution is cosine function distribution, and the axial power peak factor is 1.21; the maximum power factor of the full stack assembly is 1.46, and the minimum is 0.71. Of course, the core power distribution can be further optimized if the fuel enrichment is arranged in zones according to the different positions of the fuel assemblies.

The calculation results of the temperature reactivity coefficient of the gas-cooled micro-reactor are shown in Figs. 9 to 11. Among them, Figure 9 is the fuel temperature coefficient at the beginning of life (0EFPD) and end of life (600EFPD) at different temperatures, and its value is between -2.2pcm/K ~ -4.5pcm/K; Figure 10 is at different temperatures, at the beginning of life (0EFPD) and end-of-life (600EFPD) temperature coefficients of core graphite, the value of which is between -2.8pcm/K ~ -3.7pcm/K; Figure 11 shows the temperature coefficients at the beginning of life (0EFPD) and end of life (600EFPD) at different temperatures The temperature coefficient of graphite in the reflection layer is between 0.4 and 1.3 pcm/K, which is a small positive value. The total core temperature reactivity coefficient can be approximately regarded as the sum of the fuel temperature coefficient, the core graphite temperature coefficient, and the reflector graphite temperature coefficient, and its value is between -4.3pcm/K ~ -6.6pcm/K.

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 emergency shutdown and cold shutdown rely on the core shutdown rod. Assuming that the core temperature is 300K during the cold shutdown, considering the principle of sticking rods, the uncertainty of rod value is 10% (that is, the multiplier factor is 0.9), when the uncertainty of the positive reaction caused by the temperature reduction is 10% (ie, the multiplier factor is 1.1), the shutdown rod can provide at least a shutdown depth of -4636pcm, which fully meets the shutdown depth requirements of -1000pcm for cold shutdown . (2) The thermal shutdown of the core depends on the core start rod and the regulating rod. Assuming that the core temperature is 700K during the thermal shutdown, considering the principle of sticking rods, the uncertainty of rod value is 10% (that is, the multiplier factor is 0.9) , When the uncertainty of the positive reaction caused by the temperature reduction is 10% (ie, the multiplier factor is 1.1), the starting rod and the regulating rod can provide at least a shutdown depth of -3765pcm, which fully meets the shutdown depth requirement of -1000pcm for thermal shutdown. . (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 control rods are fully ejected, the core maximum k _eff = 1.023528 during the lifetime and the residual reactivity is +2326 pcm. The total core temperature reactivity coefficient is between ﹣4.3pcm/K～﹣6.6pcm/K. Assuming that the total temperature coefficient is -4.3pcm/K, when the temperature rises to 1740K, the reactor shuts down due to the negative reactivity introduced by the temperature increase, and the core temperature limit is 1600℃ (1873K), there is still a large temperature Lift margin. Therefore, even under accident conditions, the modular pressure tube gas-cooled micro-reactor can achieve automatic shutdown without any emergency measures and only rely on negative temperature feedback, which physically excludes the possibility of core melting and radioactive material release .

The design life of the modular pressure tube gas-cooled micro-reactor core design scheme proposed in this embodiment can be 1.5 years, and the design power can be 5 MW; during the life, when the control rod is proposed, the radial power peak factor is about 1.21, The axial power distribution is in the form of a cosine function, and the axial power peak factor is about 1.21; the core control rods can realize cold shutdown and hot shutdown respectively, with two sets of independent shutdown rod groups; the core has a strong Negative temperature feedback, the coefficient of negative temperature reactivity is at least -4pcm/K, and the large temperature rise margin ensures that under accident conditions, even if the control rod is completely ejected, without any emergency measures, it can be achieved only by the negative temperature feedback Automatic shutdown. The modular pressure tube gas-cooled micro-reactor core design has good core physical properties and superior inherent safety.

In addition, this embodiment can realize the design of different power and different lifetimes of the reactor type through reasonable core fuel design, adjustment of parameters such as core size and fuel enrichment; The core power distribution can be optimized; the reactivity can be effectively controlled by adjusting the arrangement of combustible poisons and control rods; the core size can be further reduced by the reasonable selection of the moderator material outside the pressure tube. The modular pressure tube gas-cooled microreactor core design scheme has superior design flexibility and environmental applicability.

Example 2

As shown in FIGS. 1 and 2 , the present disclosure provides an air-cooled micro-reactor core, including a fuel assembly 1, a reflector, a combustion unit, and a control rod assembly 2, wherein the control rod assembly 2 and the fuel unit are both provided In the reflection layer, a plurality of fuel units are used, each fuel unit includes a pressure tube 8 and a fuel assembly 1, the fuel assembly 1 is arranged in the pressure tube 8, so that the pressure tube serves as the pressure-bearing boundary of the core, and the control rod assembly 2 Arranged outside the pressure pipe 8 .

The details of the gas-cooled micro-stack core of this embodiment will be described in detail below.

The pressure tube 8 can be made of zirconium-niobium alloy material.

A plurality of fuel units are arranged in multiple layers from the inside to the outside, and multiple control rod assemblies 2 are used. As shown in FIG. In the layered fuel unit, and/or, as shown in FIG. 2, it may also be arranged between two adjacent layers of fuel units.

The reflection layer can be made of graphite material, which can specifically include an upper reflection layer, a lower reflection layer, and a side reflection layer 3. The upper reflection layer, the lower reflection layer, and the side reflection layer 3 together combine the fuel assembly 1 and the control rod assembly 2. The cladding, wherein the upper reflective layer and the lower reflective layer are located at the two ends of the fuel assembly 1 and the control rod assembly 2, respectively, as shown in FIG. .

In each pressure tube 8, the fuel assembly 1 may include a graphite block and a fuel rod. As shown in Figures 1, 2, and 3, the graphite block is provided with a fuel rod channel, and the fuel rod is arranged in the fuel rod channel in the graphite block. middle.

Specifically, multiple graphite blocks may be used in each fuel assembly 1, which may include a part of complete hexagonal graphite blocks and a part of incomplete hexagonal graphite blocks, and the graphite blocks are arranged and filled in the pressure tube 8 in sequence. Inside, the fuel rod channel can be arranged in each complete hexagonal graphite block, can also be arranged in each incomplete hexagonal graphite block, and can also be arranged in each complete hexagonal graphite block and in each complete hexagonal graphite block. Inside each incomplete hexagonal graphite block. Of course, the graphite blocks in each fuel assembly 1 may also be a whole, and are not limited to being formed by arranging a plurality of graphite blocks.

The fuel assembly 1 may also include a combustible poison rod (ie, poison rod 7), and a combustible poison channel may also be provided in the graphite block, and the combustible poison channel is located in the graphite block at the edge of the fuel assembly, and is close to the pressure pipe 8, as shown in Figure 3. As shown, the combustible poison rod channel is set in a part of the incomplete hexagonal graphite block, and the combustible poison rod is set in the combustible poison rod channel.

The fuel assembly 1 may also include coolant flow passages 6 for circulating coolant. The coolant flow channel 6 may include one or both of a first coolant flow channel and a second coolant flow channel. The first coolant flow channel is provided between the fuel rod and the inner wall of the fuel rod channel of the graphite block. Two coolant flow passages are arranged in the fuel rods. The coolant may be a single-phase inert gas helium.

Specifically, a gap is left between the fuel rod and the graphite block to form a first coolant flow channel. The cross section of the fuel rod is annular so that a second coolant flow channel is formed in the fuel rod (center).

The coolant flow channel 6 may also include a third coolant flow channel (not shown in the figure, that is, the coolant hole in Embodiment 1), the third coolant flow channel is arranged in the graphite block, and the third coolant flow channel is independent It is arranged and arranged with the fuel rod channel and/or the combustible poison channel according to a certain interval rule, for example, a plurality of fuel rod channels are arranged around a third coolant flow channel, and the third coolant flow channel can be along the graphite block or Said to be arranged along the length direction of the fuel assembly 1 .

The core may also include an inner tube 9, which is arranged in the pressure tube 8 and is wrapped outside the fuel assembly 1, that is, the inner tube 9 is located between the pressure tube 8 and the fuel assembly 1, and the coolant flow channel 6 may also Including a fourth coolant flow channel, the fourth coolant flow channel is provided between the inner tube 9 and the pressure tube 8 and is separate from the first coolant flow channel and/or the second coolant flow channel and/or the third coolant flow channel The coolant flows in from the fourth coolant flow channel, and flows out from the first coolant flow channel and/or the second coolant flow channel and/or the third coolant flow channel after the reflective layers converge.

Specifically, there is a gap between the inner tube 9 and the pressure tube 8. By arranging the inner tube 9, a fourth coolant flow channel can be formed between the pressure tube 8 and the inner tube 9. The inner tube 9 can be made of zirconium-niobium alloy material. production. Also, a gap is left between the top/bottom of the fuel assembly 1 and the upper/lower reflection layer, and the fourth coolant flow channel is connected to the first coolant flow channel and/or the second coolant flow channel and/or the third coolant flow channel The coolant flow passages are connected through the gaps between the top/bottom of the fuel assembly and the upper/lower reflection layers, respectively, and the coolant flows in from the fourth coolant flow passage between the pressure pipe 8 and the inner pipe 9, and is reflected at the top After the layers (that is, the upper reflective layer) or the bottom reflective layer (that is, the lower reflective layer) are merged, from the first coolant flow channel between the fuel rod and the inner wall of the fuel rod channel of the graphite block, the second coolant flow channel in the annular fuel rod Any one or more of the coolant flow passages and the third coolant flow passages between the inner pipe 9 and the pressure pipe 8 flow out.

The fuel rod includes a plurality of fuel pellets 5, and the plurality of fuel pellets 5 are stacked in the axial direction (or the length direction of the core). The fuel pellet 5 includes fuel particles and a matrix, and the fuel particles are dispersed in the matrix, that is, the fuel pellet 5 is formed by dispersing the fuel particles in the silicon carbide matrix. The base body can be made of silicon carbide material. The fuel particles include a fuel core and a cladding layer. The cladding layer coats the fuel core. The cladding layer can be one layer or multiple layers, such as four layers. The fuel core is uranium dioxide, and the cladding layer is high-temperature ceramics, that is, the fuel particles are ceramic fuel particles.

In some embodiments, the fuel unit may further include a jacket of moderating material that is jacketed outside the pressure tube 8 . The moderating material jacket can be made of graphite material, that is, the moderating material jacket can be a graphite jacket. The control rod assembly 2 is arranged adjacent to the fuel unit, and includes a body, a control rod 10, and a control rod channel is provided in the body, and the control rod 10 is arranged in the control rod channel.

Specifically, when the gas-cooled micro-reactor core of the present disclosure adopts a small pressure tube type fuel assembly, for example, when the inner diameter of the pressure tube is 20 cm, as shown in FIG. The chemical material jackets together constitute a fuel unit (also called a fuel assembly unit in Embodiment 1); the control rod assembly 2 is provided separately outside the fuel unit, and a control rod channel is provided on its body, and the control rod 10 is provided in the control rod assembly. In the control rod channel on the body of 2; the control rod assembly 2 is arranged adjacent to the fuel unit. In FIG. 1 , each fuel unit is adjacent to at least one control rod assembly 2 . The profiles of the cross-section of the body in the control rod assembly 2 and the cross-section of the moderator material jacket can both be regular hexagons for arrangement.

In other embodiments, the fuel unit further includes a moderator material jacket, the moderator material jacket is jacketed outside the pressure tube 8, and the moderator material jacket can be made of graphite material, that is, the moderator material jacket can be Graphite jacket. There is a control rod channel 4 in the moderating material jacket. The control rod assembly 2 includes a main body and a control rod 10. The body is a moderating material jacket. The control rod 10 is arranged in the control rod channel 4, so that the control rod assembly 2 and The fuel unit forms a whole.

Specifically, when the gas-cooled micro-reactor core of the present disclosure adopts a large pressure tube type fuel assembly, for example, when the inner diameter of the pressure tube is 54 cm, as shown in FIGS. The control rod hole 4 is arranged in the chemical material jacket, and the control rod 10 is arranged in the control rod hole 4 of the moderator material jacket, so that the control rod assembly 2 and the fuel unit are formed as a whole. At this time, there is no need to separately set the control rod The rod assembly 2, the moderating material jacket with the control rod channel 4 is equivalent to the body of the control rod assembly 2 as described in FIG. 1, and the control rod 10 and the fuel assembly 1 are integrated. In this embodiment, the pressure pipes 8 may be in a group of 7, wherein 6 pressure pipes at the periphery are arranged around one pressure pipe at the center. The outline of the cross-section of the graphite jacket (ie, the moderating material jacket) is a regular hexagon, and each graphite jacket can be provided with three control rod channels 4, and the control rod channels 4 are distributed in the graphite jacket at intervals. Near the three vertices of the hexagonal section.

As shown in FIG. 2 , taking the number of pressure tubes 8 as an example, the fuel assemblies 1 in the pressure tubes 8 can be divided into two zones (a central zone and a peripheral zone) in the radial direction of the core. One pressure pipe and its internal fuel assemblies are arranged in the area, and the other six pressure pipes and their internal fuel assemblies are arranged in the surrounding area, and are distributed annularly around the periphery of the central area. The axial direction of the core can be arranged in 6 layers (that is, there are 6 stacked fuel assemblies 1 in each pressure tube 8). There are 42 fuel blocks (fuel assemblies 1) in the whole stack. The size and structure of each fuel block and other characteristics may be substantially the same. Wherein, the combustible poison channels are arranged in the graphite block located at the edge of the fuel assembly 1 in the central region of the core. There are 6 combustible poison rods 7 arranged at the edge position of the fuel assembly 1 . The axial height of the entire core can be 2.7m, and the radial diameter can be 2.6m.

As shown in FIG. 6 , the outside of the control rod 10 is covered with a control rod cladding 11 .

In this embodiment, by arranging the fuel assembly 1 in each pressure tube 8, and arranging a moderating material jacket (ie, a graphite jacket) outside the pressure tube 8, the pressure tube is pressurized to form a modular structure, and a module can be obtained. In other words, the gas-cooled micro-reactor core of this embodiment is a modular pressure-tube type gas-cooled micro-reactor core.

The pressure tube type fuel assembly design in this embodiment can make the pressure-bearing boundary of the core be the pressure tube 8 of the fuel assembly 1, and the reflective layer, control rods and other components are not within the pressure boundary, which improves the performance of the reflective layer and control rods. The convenience of disassembly and transportation of other parts. At the same time, by arranging the inner tube, a fourth coolant flow channel as the coolant inlet can be formed between the pressure tube and the inner tube. After the pressure tube is cooled by the inlet coolant, the core temperature outside the pressure tube 8 is lower, which can Reduce the high temperature resistance requirements of components such as control rods. In addition, the graphite jacket and reflective layer graphite outside the pressure tube 8 can also be considered to be replaced by moderator materials with better moderation performance but lower working temperature, such as beryllium oxide, zirconium hydride and other materials, so that the core can be further reduced size.

In the reactor core of this embodiment, the fuel assembly is put into the pressure tube, and the pressure tube is pressurized to form a modular structure, and a modular pressure tube assembly can be obtained, which is easy to install, and solves the problem of many transportation components and assembly of high temperature gas-cooled reactors. It is complex and slow to respond to deployment. Moreover, the core has superior inherent safety, design flexibility, environmental adaptability, and ease of transportation and assembly. great market potential.

This embodiment also discloses a gas-cooled micro-stack, which includes the above-mentioned gas-cooled micro-stack core.

In order to analyze the physical characteristics of the above-mentioned gas-cooled micro-reactor core, this embodiment uses a universal Mon-card program to perform modeling calculation analysis on the above-mentioned gas-cooled micro-reactor with an assumed core temperature of 1200K, as follows:

The core power distribution of the gas-cooled micro-reactor is shown in Figure 8, which is the normalized component power distribution based on the average power when there is 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 1.21; in the axial direction, the power distribution is cosine function distribution, and the axial power peak factor is 1.21; the maximum power factor of the full stack assembly is 1.46, and the minimum is 0.71. Of course, if the fuel enrichment is arranged in zones according to the positions of the fuel assemblies, the core power distribution can be further optimized.

The calculation results of the temperature reactivity coefficient of the gas-cooled micro-reactor are shown in Figs. 9 to 11. Among them, Figure 9 is the fuel temperature coefficient at the beginning of life (0EFPD) and end of life (600EFPD) at different temperatures, and its value is between -2.2pcm/K ~ -4.5pcm/K; Figure 10 is at different temperatures, at the beginning of life (0EFPD) and end-of-life (600EFPD) temperature coefficients of core graphite, the value of which is between -2.8pcm/K ~ -3.7pcm/K; Figure 11 shows the temperature coefficients at the beginning of life (0EFPD) and end of life (600EFPD) at different temperatures The temperature coefficient of graphite in the reflection layer is between 0.4 and 1.3 pcm/K, which is a small positive value. Due to the good core cooling performance and thermal conductivity of the gas-cooled micro-reactor, the temperature difference between the fuel and the core graphite is very small, and the temperature changes are almost synchronous. The sum of the temperature coefficient and the temperature coefficient of the graphite in the reflection layer is between ﹣4.3pcm/K～﹣6.6pcm/K.

(1) The core emergency shutdown and cold shutdown rely on the core shutdown rod. Assuming that the core temperature is 300K during the cold shutdown, considering the principle of sticking rods, the uncertainty of rod value is 10% (that is, the multiplier factor is 0.9), when the uncertainty of the positive reaction caused by the temperature reduction is 10% (ie, the multiplier factor is 1.1), the shutdown rod can provide at least a shutdown depth of -4636pcm, which fully meets the shutdown depth requirements of -1000pcm for cold shutdown . (2) The thermal shutdown of the core depends on the core start rod and the regulating rod. Assuming that the core temperature is 700K during the thermal shutdown, considering the principle of sticking rods, the uncertainty of rod value is 10% (that is, the multiplier factor is 0.9) , When the uncertainty of the positive reaction caused by the temperature reduction is 10% (ie, the multiplier factor is 1.1), the starting rod and the regulating rod can provide at least a shutdown depth of -3765pcm, which fully meets the shutdown depth requirement of -1000pcm for thermal shutdown. . (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 control rods are fully ejected, during the lifetime, the maximum core keff = 1.023528 and the residual reactivity is +2326 pcm. Among them, the total core temperature reactivity coefficient is between ﹣4.3pcm/K～﹣6.6pcm/K. Assuming that the total temperature coefficient is -4.3pcm/K, when the temperature rises to 1740K, the reactor shuts down due to the negative reactivity introduced by the temperature increase, and the core temperature limit is 1600℃ (1873K), there is still a large temperature Lift margin. Therefore, the modular pressure tube 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 excludes the possibility of core melting and radioactive material release. sex.

The design life of the gas-cooled micro-reactor core design scheme proposed in this embodiment can be 1.5 years, and the design power can be 5 MW; during the life, when the control rods are proposed, the radial power peak factor is about 1.21, and the axial power distribution is In the form of cosine function, the axial power peak factor is about 1.21; the core control rods can realize cold shutdown and hot shutdown respectively, with two independent shutdown rod groups; the core has strong negative temperature feedback, and the temperature The negative reactivity coefficient is at least -4pcm/K, and the large temperature rise margin ensures that under accident conditions, even if the control rod is completely ejected, without any emergency measures, the reactor can be automatically shut down only by means of negative temperature feedback. The modular pressure tube gas-cooled micro-reactor core design has good core physical properties and superior inherent safety.

In addition, this embodiment can realize the design of different power and different lifetimes of the reactor type through reasonable core fuel design, adjustment of parameters such as core size and fuel enrichment; The core power distribution can be optimized; the reactivity can be effectively controlled by adjusting the arrangement of combustible poisons and control rods; the core size can be further reduced by the reasonable selection of the moderator material outside the pressure tube. The gas-cooled microreactor core design scheme has superior design flexibility and environmental applicability.

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

An air-cooled micro-reactor core is characterized in that it includes a reflective layer, a fuel unit and a control rod assembly, the control rod assembly and the fuel unit are both arranged in the reflective layer, and multiple fuel units are used, each Each fuel unit includes a pressure tube and a fuel assembly, the fuel assembly being arranged within the pressure tube so that the pressure tube acts as a pressure-bearing boundary of the core, and the control rod assembly being arranged outside the pressure tube.
The gas-cooled micro-reactor core according to claim 1, wherein a plurality of fuel units are arranged in layers from the inside to the outside, and a plurality of the control rod assemblies are used, and each control rod assembly is arranged on the outermost fuel unit The exterior, and/or, is arranged in any one layer of fuel units, and/or, is arranged between two adjacent layers of fuel units.
The gas-cooled micro-reactor core according to claim 1, wherein in each pressure tube, the fuel assembly comprises a graphite block and a fuel rod, wherein a fuel rod channel is provided in the graphite block, and the fuel rod is provided with a fuel rod channel. in the fuel rod channel.
The gas-cooled micro-reactor core according to claim 3, wherein the fuel assembly further comprises a combustible poison rod, the graphite block is further provided with a combustible poison channel, and the combustible poison rod is arranged on the combustible poison rod in the channel.
The gas-cooled micro-reactor core of claim 4, wherein the fuel rod comprises a plurality of fuel pellets, and the plurality of fuel pellets are stacked along the length of the core;

The fuel pellet includes fuel particles and a matrix in which the fuel particles are dispersed.
6. The gas-cooled micro-reactor core of claim 5, wherein the fuel particles comprise a fuel core and a cladding layer surrounding the fuel core.
The gas-cooled micro-reactor core of claim 5, wherein the fuel assembly further comprises a coolant flow channel, and the coolant flow channel includes a first coolant flow channel, a second coolant flow channel, and one or more of third coolant flow channels, wherein the first coolant flow channel is provided between the fuel rod and the inner wall of the fuel rod channel of the graphite block, and the second coolant flow channel is provided between the fuel rod and the inner wall of the fuel rod channel of the graphite block. The flow channels are arranged in the fuel rods, and the third coolant flow channels are arranged in the graphite blocks, and are regularly arranged with the fuel rod channels and/or the combustible poison channels.
The gas-cooled micro-reactor core according to claim 7, further comprising an inner tube, the inner tube is arranged in the pressure tube and is wrapped outside the fuel assembly, and the coolant flow channel Also includes a fourth coolant flow channel, the fourth coolant flow channel is provided between the inner tube and the pressure tube and is connected with the first coolant flow channel and/or the second coolant and/or the The third coolant flow channels are respectively connected, the coolant flows in from the fourth coolant flow channel, and after the reflective layers converge, the coolant flows from the first coolant flow channel and/or the second coolant flow channel and/or the first coolant flow channel and/or the second coolant flow channel. Three coolant runners flow out.
The gas-cooled micro-reactor core according to any one of claims 1 to 8, wherein the fuel unit further comprises a moderator material jacket, and the moderator material jacket is jacketed outside the pressure tube ;

The control rod assembly is arranged adjacent to the fuel unit, and includes a body and a control rod, the body is provided with a control rod channel, and the control rod is disposed in the control rod channel.
The gas-cooled micro-reactor core according to any one of claims 1 to 8, wherein the fuel unit further comprises a moderator material jacket, and the moderator material jacket is jacketed outside the pressure tube , a control rod channel is arranged in the moderating material jacket layer, the control rod assembly includes a body and a control rod, the body is the moderating material jacket layer, and the control rod is arranged in the control rod channel, so as to The control rod assembly and the fuel unit are integrally formed.
A gas-cooled micro-stack, characterized by comprising the gas-cooled micro-stack core according to any one of claims 1-10.