CN219017253U

CN219017253U - Heat pipe type fuel element and reactor core

Info

Publication number: CN219017253U
Application number: CN202223311721.3U
Authority: CN
Inventors: 陈兴伟; 邹杨; 戴叶; 崔德阳; 蔡翔舟
Original assignee: Shanghai Institute of Applied Physics of CAS
Current assignee: Shanghai Institute of Applied Physics of CAS
Priority date: 2022-12-09
Filing date: 2022-12-09
Publication date: 2023-05-12
Anticipated expiration: 2032-12-09

Abstract

The utility model discloses a heat pipe type fuel element and a reactor core. The heat pipe type fuel element comprises a first matrix and a second matrix which are coaxially and fixedly connected from bottom to top, wherein the first matrix and the second matrix are of hollow tubular structures and are communicated with each other; the inner side walls of the tubular structures of the first substrate and the second substrate are respectively provided with a first groove and a second groove which are axially distributed, and the joint of the first groove and the second groove is continuous and free of faults. The heat pipe type fuel element adopts an integrated design to avoid the heat efficiency problem and the safety problem caused by the heat resistance of the gaps, and ensures the close contact between fuel particles and heat transfer working media. The reactor core has the advantages of simple and compact structure, easy assembly and maintenance, high heat transfer efficiency, stable and reliable performance and capability of meeting the requirements of multi-scenario and multi-purpose energy supply.

Description

Heat pipe type fuel element and reactor core

Technical Field

The utility model relates to a heat pipe fuel element and a core.

Background

The heat pipe is an passive heat exchange element which realizes heat transfer by means of internal working medium phase change and continuous circulation, and has the advantages of high heat transfer efficiency, reversible heat flow direction, compact structure, effective isolation of secondary side fluid and the like. Numerous heat pipe stack solutions have been developed since the 90 s of the last century, and in recent years, with the success of the U.S. kilowatt grade heat pipe stack Kilopower ground prototype stack KRUSTY, the heat pipe stack has become a new type of reactor research hotspot. In the heat pipe pile design, the heat pipe is directly inserted into the reactor core to lead out nuclear heat, the system is simplified and has moderate volume, good operability and optimal thermal transient feedback performance, and meanwhile, the system has high reliability and minimum maintenance requirements, can be flexibly applied to application scenes such as deep sea deep space and land-based nuclear power stations, and has profound significance for science and technology and energy development in China.

In the prior art, heat pipes are mostly inserted into the core. For example, the following three forms of core fuel and heat pipe designs: (1) The fuel rods and the heat pipes form a fuel module, the heat conduction of the fuel and the heat pipes is enhanced by metal blocks in the module, and a plurality of modules are inserted into a reactor core, such as a HOMER spark/moon detection reactor and an HP-STMCs space reactor; (2) a metal matrix: the fuel rods or fuel pieces and heat pipes are placed in channels in a metal matrix, such as MagePower, eVinci. The liquid sodium metal is partially filled to reduce the thermal resistance of the gaps, but the filling quantity needs to consider the expansion caused by heat and contraction caused by cold, and particularly the positions of the gaps change when the inclination angle of the reactor core changes, so that the heat transfer uniformity cannot be ensured; (3) a fuel substrate: the heat pipe is inserted into the fuel matrix channel, such as the FSP of Kilopower of 1-10kWe and FSP of 1-kWe, which is only suitable for small power stacks with fewer heat pipes, and the large power stack type is not suitable. However, the fuel rod or fuel block is directly contacted with the working medium, which is easy to activate, fission gas enters the heat pipe, and radioactive leakage can be caused when the single heat pipe is damaged.

In addition, in the prior art, a loop heat pipe is inconvenient to assemble with a reactor core formed by the fuel block, and a gap of 1-3mm between the heat pipe and the fuel block also causes a large gap thermal resistance when the loop heat pipe is applied in a vacuum environment (such as space), so that hot spots and even safety problems can occur.

In the scheme, a heat pipe inserting channel or a heat pipe and fuel rod connecting metal block mode is adopted, and the heat transfer of the heat pipe and the fuel rod depends on solid heat conduction. Because of long-time high-temperature operation and uneven power and temperature, larger stress exists between the fuel and the heat pipe, and in addition, the problem of swelling caused by fuel irradiation can lead to the connection damage of the fuel rod and the heat pipe to generate gaps, especially in a vacuum environment, the heat transfer performance is drastically reduced due to the thermal resistance of the gaps, and the fuel operation temperature is obviously increased and even endangers the safety of the reactor. When the core of the heat pipe pile filled with the liquid metal is inclined or changed in position, hot spots may occur when the liquid metal is not filled into the upper gap. In addition, in most core solutions using fuel rods, the core temperature is too high, which faces safety accident problems such as the fusion of the core of the Fudao nuclear power plant.

The prior art discloses a boiling water reactor which utilizes the phase change heat transfer of water, fuel rods are inserted into the reactor core, the water flows through the fuel rods to form a mixture of steam and water, and the steam and water flows through a steam-water separator and a steam dryer to drive a turbine to generate electricity by using separated high-temperature steam. However, the reactor comprises a plurality of pump valves and loops, the structure is complex, the pressure is high, the loop circulation easily causes radioactive leakage, and potential safety hazards exist.

Disclosure of Invention

In order to overcome the defects of low heat transfer efficiency and low safety performance caused by the gap thermal resistance of the heat pipe pile in the prior art, a heat pipe type fuel element and a reactor core are provided. The heat pipe type fuel element adopts an integrated design to avoid the heat efficiency problem and the safety problem caused by the heat resistance of a gap, ensure the close contact between fuel particles and a heat transfer working medium and avoid radioactive leakage. The reactor core has the advantages of simple and compact structure, easy assembly and maintenance, high heat transfer efficiency, stable and reliable performance and capability of meeting the requirements of multi-scenario and multi-purpose energy supply.

In order to achieve the above object, the present utility model provides the following technical solutions:

the utility model provides a heat pipe type fuel element, which comprises a first matrix and a second matrix which are coaxially and fixedly connected from bottom to top, wherein the first matrix and the second matrix are hollow tubular structures and are mutually communicated; the first substrate and the second substrate have a structure of one or two modes:

mode one: the inner side walls of the tubular structures of the first substrate and the second substrate are respectively provided with a first groove and a second groove which are axially distributed, and the joint of the first groove and the second groove is continuous and free from faults; the first matrix is made of metal or a moderator, fuel particles are dispersed in the first matrix, and the fuel particles are provided with a coating layer; the second matrix is a metal matrix without fuel particles;

mode two: the inner side walls of the tubular structures of the first matrix and the second matrix are respectively stuck with a first silk screen and a second silk screen which are axially distributed, and the joint of the first silk screen and the second silk screen is continuous and free from faults; the first matrix is made of metal or a moderator, fuel particles are dispersed in the first matrix, and the fuel particles are provided with a coating layer; the second matrix is made of metal materials without fuel particles.

In the utility model, the continuous and fault-free design of the connection part between the first groove and the second groove and between the first silk screen and the second silk screen is convenient for the reflux of working medium.

In the present utility model, the inner diameter of the tubular structure of the first base may be the same as the inner diameter of the tubular structure of the second base.

In the present utility model, the first groove and the second groove may have the same shape.

In the present utility model, preferably, the first groove or the second groove is uniformly disposed around the inner sidewall of the tubular structure.

In the utility model, preferably, the first groove or the second groove is one or more of a square groove, a rectangular groove, a circular groove and a special groove, and more preferably an omega-shaped groove, so that a liquid suction core structure is formed, the fuel volume share can be better improved, and the use requirement is met.

In the present utility model, preferably, the first groove or the second groove is independently provided with at least one layer of wire mesh at the edge closest to the axis of the heat pipe type fuel element, the first groove and the second groove and the wire mesh form a composite liquid suction core structure respectively, in the liquid suction core structure, large holes can reduce flow resistance to help liquid return, and small holes can provide large capillary force.

In the present utility model, preferably, the first screen or the second screen is a single-layer screen or a composite screen, more preferably a composite screen; even more preferably, the composite wire mesh is a double layer wire mesh having different pore sizes; the double layer wire mesh can facilitate both reflow and increase capillary force.

In the present utility model, preferably, the first substrate is cylindrical or polygonal; more preferably, when the first substrate is made of metal, the first substrate is cylindrical; more preferably, when the first substrate is made of a moderator, the first substrate is in a regular hexagonal prism shape.

In the present utility model, the length of the first substrate may be the same as the length of the second substrate.

In the present utility model, preferably, the outer diameter of the first base is equal to or larger than the outer diameter of the second base.

In the present utility model, the second substrate is preferably cylindrical or polygonal, more preferably cylindrical.

In the utility model, the first matrix and the second matrix can play a role in sealing, so that the heat transfer working medium is positioned in the heat pipe type fuel element, the share of the volume of the core fuel is improved to a greater extent, and the size of the core is reduced.

In the present utility model, the metal material is preferably a material with no neutron absorption capability and high temperature and irradiation resistance, and more preferably 316ss stainless steel.

In the present utility model, preferably, the material of the moderator is one or more of silicon carbide, graphite and yttrium hydride, and more preferably yttrium hydride or silicon carbide.

In the present utility model, preferably, the periphery of the first substrate is further covered with a tube shell.

Wherein, preferably, the thickness of the tube shell is 1-3 mm.

Wherein, preferably, the tube shell is made of metal or moderator.

In the present utility model, the fuel particles preferably have a filling ratio of 10 to 64%, more preferably 40 to 60%, in the first matrix.

In the present utility model, the material of the coating layer is preferably metal, carbide or carbide-refractory metal, more preferably carbide, still more preferably silicon carbide.

In the present utility model, the core of the fuel particle is preferably one or more of uranium nitride, uranium oxide and uranium oxycarbide, and more preferably uranium nitride. The density of the uranium nitride is high, and compared with uranium oxide or uranium oxycarbide, the uranium nitride can improve heavy metal loading by 40%.

In the present utility model, preferably, the fuel particles are one or more of TRISO particles, FCM and MOX, more preferably TRISO particles. The TRISO particles sequentially comprise a loose pyrolytic carbon layer, an inner compact pyrolytic carbon layer, a silicon carbide layer and an outer compact pyrolytic carbon layer from the core of the fuel particles outwards; the TRISO particles can maintain integrity at 2100 ℃.

In the present utility model, the diameter of the fuel particles is preferably 0.5 to 1mm. Within this range of particles, the more advantageous is to increase the packing rate in the heat pipe fuel element, thereby facilitating a reduction in the volume of the heat pipe fuel element and thus a reduction in the size of the core.

In the utility model, the heat pipe type fuel element can be processed and manufactured by adopting a traditional processing mode and also can be processed and manufactured by adopting an additive manufacturing technology (such as 3D printing).

The utility model also provides a reactor core, which comprises a reactor core container and a plurality of heat pipe type fuel elements which are filled in the reactor core container and are distributed in parallel with the axis of the reactor core container.

In the utility model, preferably, the reactor core further comprises a reflecting layer and a plurality of control drums, wherein the control drums are arranged in the reflecting layer; more preferably, when the control drums are more than two, each control drum is symmetrically distributed in the reflecting layer with the central axis of the reactor core container.

In the present utility model, preferably, the core further comprises shutdown control rods; more preferably, the shutdown control rods are disposed in the center of the core.

In the present utility model, the reflection layer is preferably provided on the periphery of the core vessel.

In the present utility model, when the first matrix is made of a moderator material, the fuel particles preferably occupy 10 to 30% of the volume of the core vessel.

In the present utility model, it is preferable that the fuel particles occupy 30 to 50% of the volume of the core vessel when the first base is made of metal.

In a preferred embodiment, when the first substrate is made of metal, a plurality of moderator channels are arranged at the bottom of the reactor core container; the heat pipe type fuel elements are connected with the moderator channels one by one along the direction parallel to the axis of the reactor core container.

In a preferred embodiment, when the first substrate is made of a moderator, the plurality of heat pipe fuel elements are uniformly distributed in the core vessel along a direction parallel to the axis of the core vessel.

The utility model also provides an operation method of the reactor core, which comprises the following steps: and placing the heat pipe type fuel element filled with the heat transfer working medium into the reactor core, and operating the reactor core.

In the utility model, the heat transfer working medium is generally added according to the process flow of filling the high-temperature heat pipe; preferably, the tubular structure of the heat pipe type fuel element filled with the heat transfer working medium is in a vacuum state.

In the utility model, the working temperature of the heat transfer working medium can be in the range of 400-1800 ℃, and the heat transfer working medium can preferably operate in the range of less than 500 ℃ and more than 1600 ℃.

In the present utility model, preferably, the heat transfer medium comprises one or more of Li, na, K, naK alloy or nanofluid, and more preferably Li or NaK alloy. When the heat transfer working medium is Na, the vaporization latent heat of the heat transfer working medium is 4090 kilojoules/kilogram and is 2 times of that of water (the water is 2260 kilojoules/kilogram), so that more heat can be taken away; when the heat pipe type fuel element can operate at high temperature, the heat utilization efficiency of high temperature output is high, and the application modes are various, such as hydrogen production, energy storage and the like.

In the present utility model, preferably, the filling rate of the heat transfer working medium in the cavity inside the tubular structure of the heat pipe type fuel element is 15-35%.

In the present utility model, the core preferably has an operating temperature of 500 ℃ or more, more preferably 500 to 1600 ℃, to ensure efficient system heat removal.

In a preferred embodiment, when the core operating temperature is 650-1100 ℃, the heat transfer working medium can be NaK alloy, and the weight ratio of K to Na of the NaK alloy is 77.2:22.8, the melting point is-12.3 ℃, and the temperature is liquid at normal temperature, so that the reactor is easy to start.

In a preferred embodiment, the heat transfer medium may be Li at a core operating temperature above 1000 ℃.

In the present utility model, the operating power of the core is preferably 1kW to 10MW.

In the utility model, preferably, when the operating temperature of the reactor core is 650-1100 ℃, the heat transfer working medium is NaK alloy, and the weight ratio of K to Na of the NaK alloy is 77.2:22.8.

In the present utility model, preferably, when the operating temperature of the core is 1000 ℃ or higher, the heat transfer medium is Li.

In the present utility model, preferably, the heat pipe type fuel element includes an evaporation section, an insulation section and a condensation section during the operation of the core; the evaporation section is positioned in the reactor core container; the heat-pipe type fuel element has no heat loss or generation in the heat-insulating section; the condensing section is a heat dissipation part and is used for transferring heat to the energy conversion system.

In the utility model, the heat pipe type fuel element in the reactor core utilizes the phase change of working medium to guide nuclear heat generated by fuel particles in the evaporation section to the condensation section during operation, and then the nuclear heat is transmitted to the energy conversion system by the condensation section.

The utility model also provides the application of the reactor core in land-based maneuvering, deep sea exploration or energy supply.

On the basis of conforming to the common knowledge in the field, the above preferred conditions can be arbitrarily combined to obtain the preferred examples of the utility model.

The reagents and materials used in the present utility model are commercially available.

The utility model has the positive progress effects that:

(1) In the utility model, because the fuel particles are dispersed in the metal matrix with good heat conductivity, the groove formed by the metal matrix is directly contacted with the working medium flowing in the heat pipe, so that the integrated design avoids the thermal engineering and safety problems caused by gap thermal resistance, simultaneously further reduces the metal volume of the tube shell, improves the volume share of fuel, and is beneficial to reducing the core structure.

(2) The fuel particles in the heat pipe type fuel element have a coating layer, can contain fission gas generated during operation, have high temperature resistance and inclusion, reduce the problems of radioactive pollution, thermal stress deformation and the like, and can ensure the safety of the system even in high-temperature operation.

(3) The interior of the heat pipe type fuel element is in vacuum and is in a negative pressure environment, so that the pressure is lower in the operation process of the reactor core, and the safety problem is not caused; in addition, the fuel element is a closed heat pipe, can be effectively isolated from the reactor core and a subsequent loop, and avoids the problems of radioactive pollution and the like.

(4) The reactor core of the utility model has no movable parts, can realize high-efficiency heat transfer, and is safe and reliable. Because of the reversibility of heat flow density of the heat pipe and the integrated heat transfer of the fuel working medium, the reactor core has strong environmental applicability and can stably run under the working conditions of transverse arrangement, vertical arrangement, swinging and the like.

(5) The reactor core has a simple and compact structure, can be assembled by inserting the elements into the reactor core, is easy to assemble and maintain, and can be suitable for multi-scene and multi-purpose energy supply in land-based maneuvering, deep sea exploration, deep space, star meters or remote areas and the like.

Drawings

FIG. 1 is a schematic structural view of a heat pipe type fuel element a of embodiment 1;

FIG. 2 is a cross-sectional view of a second substrate of the heat pipe type fuel element a of example 1;

FIG. 3 is a cross-sectional view of a first substrate of a heat pipe type fuel element a of example 1;

FIG. 4 is a perspective view of a first substrate of a heat pipe type fuel element a of example 1;

FIG. 5 is a block diagram of a core containing a heat pipe type fuel element a of example 1;

FIG. 6 is a schematic illustration of the distribution of the heat pipe fuel elements a of example 1 in the core;

FIG. 7 is a schematic structural view of a heat pipe type fuel element b of embodiment 2;

FIG. 8 is a cross-sectional view of a second substrate of the heat pipe type fuel element b of example 2;

FIG. 9 is a cross-sectional view of a first substrate of a heat pipe type fuel element b of example 2;

FIG. 10 is a dimensional view of a first substrate of a heat pipe type fuel element b of example 2;

FIG. 11 is a schematic diagram of omega-shaped grooves of a heat pipe type fuel element b of example 2;

FIG. 12 is a perspective view of a first substrate of a heat pipe type fuel element b of example 2;

FIG. 13 is a schematic view showing the area division of the heat pipe type fuel element b of embodiment 2;

fig. 14 is a schematic view showing the arrangement of the heat pipe type fuel element b of example 2.

Reference numerals illustrate:

heat pipe type fuel element 1

First substrate 2

Evaporator section 21

Second base 3

Insulation section 31

Condensing section 32

First groove 5

Second groove 6

Shell 7

Core 8

Reactor core vessel 9

Reflective layer 10

Control drum 11

Silk screen 13

Inscribed diameter d of first matrix _o

Vapor chamber diameter d of first substrate _v

Outer diameter di of the second substrate

Omega-shaped groove circle diameter d

Slot width w

Depth delta of slot

Detailed Description

The utility model is further illustrated by means of the following examples, which are not intended to limit the scope of the utility model. The experimental methods, in which specific conditions are not noted in the following examples, were selected according to conventional methods and conditions, or according to the commercial specifications.

Example 1

FIG. 1 is a schematic view of a heat pipe type fuel element a of the present embodiment; fig. 2 is a sectional view of the second base 3 of the heat pipe type fuel element a of the present embodiment; fig. 3 is a sectional view of the first base 2 of the heat pipe type fuel element a of the present embodiment; fig. 4 is a perspective view of the first substrate 2 of the heat pipe type fuel element a of the present embodiment.

The heat pipe type fuel element 1 comprises a first matrix 2 and a second matrix 3 which are coaxially and fixedly connected from bottom to top, wherein the first matrix 2 and the second matrix 3 are hollow tubular structures and are communicated with each other; the inner side walls of the tubular structures of the first substrate 2 and the second substrate 3 are respectively provided with a first groove 5 and a second groove 6 which are axially distributed, and the joint of the first groove 5 and the second groove 6 is continuous and free from faults; the first matrix 2 is made of metal material of 316ss stainless steel, fuel particles with the diameter of 0.5mm are dispersed and distributed in the first matrix 2, and are TRISO particles, and the core of the fuel particles sequentially comprises a loose pyrolytic carbon layer, an inner compact pyrolytic carbon layer, a silicon carbide layer and an outer compact pyrolytic carbon layer from outside; the fuel particles have an internal filling rate of 40% in the first matrix 2; the fuel particles have a silicon carbide coating; the second matrix 3 is a metal matrix of 316ss stainless steel without fuel particles; the diameter of the inner diameter of the tubular structure of the first matrix 2 was 2.2cm, which was the same as the inner diameter of the tubular structure of the second matrix 3, and the shape of the first groove 5 was the same as the shape of the second groove 6. The first groove 5 and the second groove 6 are uniformly and annularly arranged on the inner side wall of the tubular structure, and independently 60 rectangular grooves with the width of 0.8mm and the depth of 1mm are symmetrically distributed along the circumference of the inner wall of the first matrix 2, and 4 layers of stainless steel wire meshes are also independently arranged at the edge closest to the axis of the heat pipe type fuel element a, wherein the aperture of each wire mesh is 0.254mm. The first substrate 2 is cylindrical; the length of the first substrate 2 is 50cm and the length of the second substrate 3 is 50cm. The outer diameter of the first substrate 2 was 4cm, and the outer diameter of the second substrate 3 was 3.2cm. The second substrate 3 is cylindrical. The periphery of the first substrate 2 is also coated with a shell of 316ss stainless steel with a thickness of 2 mm.

The heat pipe type fuel element a of the present embodiment is manufactured by additive manufacturing technology (such as 3D printing). Printing is completed by the manufacturing mode, vacuumizing is carried out, and the end cover is sealed after liquid filling.

Fig. 5 is a structural view of the core 8 containing the heat pipe type fuel elements a of the present embodiment; fig. 6 is a schematic diagram of the distribution of the heat pipe fuel elements a of the present embodiment in the core 8. The reactor core 8 comprises a reactor core vessel 9, 37 heat pipe type fuel elements 1 which are distributed in parallel with the axis of the reactor core vessel 9, a reflecting layer 10 and two control drums 11, wherein the two control drums 11 are symmetrically distributed in the reflecting layer 10 with the axis of the reactor core vessel 9. The fuel particles are filled in an amount of 30% of the volume of the core vessel 9. The reactor core vessel 9 also comprises a moderator channel, and the heat pipe type fuel element 1 is inserted into the moderator channel to realize reactor core assembly. The fuel particles account for 18% of the volume of the core vessel 9. The tubular structure of the heat pipe type fuel element a is in a vacuum state, and 100g of heat transfer working medium sodium is filled in the inner cavity.

The operating power of the reactor was 50kW and the operating temperature of the core was 700 ℃. The diameter of the active area of the reactor core is 36cm, and the height is 50cm. The required heat transfer quantity of a single heat pipe is 1.35kW, and the heat pipe type fuel element 1 has a heat transfer limit of 3.6kW in a gravity-free environment, so that the heat transfer requirement of multiple scenes is met.

During operation of the core, the heat pipe type fuel element 1 is divided into an evaporation section 21, an insulation section 31 and a condensation section 32; the evaporation section 21 corresponds to the first matrix 2, the grooves of the evaporation section 21 occupy 46% of the total volume of the reactor core, and the heat insulation section 31 and the condensation section 32 correspond to the second matrix 3; the evaporator section 21 is located in the core vessel 9; the heat-insulating section 31 of the heat pipe type fuel element 1 is a portion that does not exchange energy with the outside, and is located in the reflective layer 10; the condensing section 32 is located outside the core for transferring heat to the energy conversion system.

The heat transfer limit of the single heat pipe is 3.7kW compared with the existing 600 ℃ single heat pipe, the heat transfer limit of the single heat pipe type fuel element 1 in the embodiment is 11.5kW when the working temperature is 700 ℃ and the reactor core is vertically placed, and the heat transfer limit is 3.6kW when the single heat pipe type fuel element is horizontally placed or in a gravity-free environment.

The reactor core in the embodiment has a simple and reliable structure, can effectively improve the thermal efficiency of the molten salt reactor, reduce hot spots and the generated safety problem, and has higher heat transfer capability when dealing with the environments such as vacuum, swing and the like. The heat pipe pile can be applied to land-based maneuvering, deep space and deep sea exploration or energy supply.

Example 2

FIG. 7 is a schematic view of the heat pipe type fuel element b of the present embodiment; fig. 8 is a sectional view of the second base 3 of the heat pipe type fuel element b of the present embodiment; fig. 9 is a sectional view of the first base 2 of the heat pipe type fuel element b of the present embodiment; fig. 10 is a dimensional view of the first substrate 2 of the heat pipe type fuel element b of the present embodiment; FIG. 11 is a schematic diagram of omega-shaped grooves of a heat pipe type fuel element b of the present embodiment; fig. 12 is a perspective view of the first substrate 2 of the heat pipe type fuel element b of the present embodiment.

The heat pipe type fuel element 1 comprises a first matrix 2 and a second matrix 3 which are coaxially and fixedly connected from bottom to top, wherein the first matrix 2 and the second matrix 3 are hollow tubular structures and are communicated with each other; the inner side walls of the tubular structures of the first substrate 2 and the second substrate 3 are respectively provided with a first groove 5 and a second groove 6 which are axially distributed, and the joint of the first groove 5 and the second groove 6 is continuous and free from faults; the first matrix 2 is made of a moderator material of compact silicon carbide, fuel particles with the diameter of 0.5mm are dispersed and distributed in the first matrix 2, and are TRISO particles, and the core of the fuel particles sequentially comprises a loose pyrolytic carbon layer, an inner compact pyrolytic carbon layer, a silicon carbide layer and an outer compact pyrolytic carbon layer from outside; the fuel particles have an internal filling rate of 40% in the first matrix 2; the fuel particles have a silicon carbide coating; the second matrix 3 is a metal matrix of 316ss stainless steel without fuel particles; the diameter of the inner diameter of the tubular structure of the first matrix 2 was 2.4cm, which was the same as the inner diameter of the tubular structure of the second matrix 3, and the shape of the first groove 5 was the same as the shape of the second groove 6. The first matrix 2 is in a regular hexagonal prism shape; the length of the first substrate 2 is 50cm and the length of the second substrate 3 is 50cm. The second substrate 3 is cylindrical. Wherein, the first groove 5 and the second groove 6 are uniformly and annularly arranged on the inner side wall of the tubular structure and are independently omega-shaped grooves, the circle diameter d is 1.4mm, the slot width w is 0.3mm, the slot depth delta is 0.72mm, and 50 grooves are symmetrically distributed along the circumference of the inner wall of the first matrix 2.

The heat pipe type fuel element b of the present embodiment is manufactured by additive manufacturing technology (e.g., 3D printing). Printing is completed by the manufacturing mode, vacuumizing is carried out, and the end cover is sealed after liquid filling.

The outer diameter of the first substrate 2 is 4cm, and the inscribed diameter d of the first substrate 2 _o The outer diameter di of the second substrate 3 is 3.86cm, the steam cavity diameter d of the first substrate is 3.2cm _v 2.4cm.

The heat pipe type fuel element b can be manufactured by adopting an additive manufacturing (Additive Manufacturin) mode, namely, on the basis of a design model, the fuel element is constructed by adopting materials such as silicon carbide powder, TRISO particles, a binder and the like in a layer-by-layer printing mode. The printed fuel element b completes the manufacturing and processing of the whole heat pipe type fuel element after the procedures of vacuumizing, filling liquid, sealing and the like.

Fig. 13 is a schematic view of the area division of the heat pipe type fuel element b of the present embodiment. During operation of the core, the heat pipe type fuel element b is divided into an evaporation section 21, an insulation section 31 and a condensation section 32; the evaporation section 21 corresponds to the first matrix 2, the grooves of the evaporation section 21 occupy 46% of the total volume of the reactor core, and the heat insulation section 31 and the condensation section 32 correspond to the second matrix 3; the evaporator section 21 is located in the core vessel 9; the heat-insulating section 31 of the heat pipe type fuel element b is a portion which is not energy-exchanged with the outside and is located in the reflective layer 10; the condensing section 32 is located outside the core for transferring heat to the energy conversion system.

Fig. 14 is a schematic view showing the arrangement of the heat pipe type fuel elements b of the present embodiment. In a 50kW mini-reactor core vessel, 37 heat pipe fuel elements b are provided, arranged in a hexagonal cross-section. The heat pipe type fuel element b is mainly subjected to a carrying limit value when vertically placed, the heat transfer limit is 6.7kW, and the heat transfer limit is 2.2kW when horizontally placed or operated in a deep space gravity-free environment.

The diameter of the active area of the reactor core is 28cm, and the height is 50cm. The reactor core gap is filled with a moderator, so that heat transfer between adjacent elements is enhanced, and local hot spots caused by failure of a single heat pipe are avoided. According to the filling rate of the granular silicon carbide matrix of 0.4, the volume ratio of fuel particles in the reactor core is 18%, and the neutron physical requirement is met. The tubular structure of the heat pipe type fuel element b is in a vacuum state, and 100g of heat transfer working medium sodium is filled in the inner cavity. At full power operation, the heat transfer capacity of a single heat pipe needs 1.35kW, which is far below the heat transfer limit of the heat pipe type fuel element. Compared with the heat pipe type fuel element a, the heat pipe type fuel element b is characterized in that the coated fuel particles are directly dispersed in the moderator matrix, so that the core structure can be more effectively simplified, and the core size can be reduced.

The operating power of the reactor was 50kW and the operating temperature of the core was 700 ℃. The diameter of the active area of the reactor core is 28cm, and the height is 50cm. The heat transfer quantity required by a single heat pipe is 1.35kW, and the heat pipe type fuel element b has a heat transfer limit of 3.6kW in a gravity-free environment, so that the heat transfer requirement of multiple scenes is met.

Effect example 1

Table 1 shows the hot spot temperatures of the cores under different conditions. Because of the gaps inside, both existing land and space piles have higher hot spot temperatures. In contrast, the land and space stacks formed in examples 1 and 2 of the present application, due to the integrated design, avoid thermal resistance of the gaps, make the hot spot temperatures more stable, both being 740 ℃.

TABLE 1

	Gap 0.1mm	Gap 0.3mm	Examples 1 and 2 (seamless)
				Land pile	920℃	950℃	740℃
Space pile	970℃	1000℃	740℃

For a single heat transfer of 5kW and a heat pipe-fuel assembly with the temperature of an evaporation section of 700 ℃, the design of the utility model has no problem of local hot spots caused by gap thermal resistance, and compared with the design of inserting a heat pipe into a fuel channel, the overall reactor core temperature distribution is more uniform, and hot spots with different application environments are different by more than 180 ℃, so that the heat transfer stability, the material service life and the reactor core safety are extremely important.

Claims

1. The heat pipe type fuel element is characterized by comprising a first matrix and a second matrix which are coaxially and fixedly connected from bottom to top, wherein the first matrix and the second matrix are hollow tubular structures and are communicated with each other;

the inner side walls of the tubular structure of the first matrix and the tubular structure of the second matrix are respectively provided with a first groove and a second groove which are axially distributed, and the joint of the first groove and the second groove is continuous and free of faults.

2. The heat pipe fuel element of claim 1, wherein the inner diameter of the tubular structure of the first substrate is the same as the inner diameter of the tubular structure of the second substrate;

and/or the first groove and the second groove have the same shape;

and/or the first groove or the second groove is uniformly and annularly arranged on the inner side wall of the tubular structure;

and/or the first groove or the second groove is one or more of a square groove, a rectangular groove, a circular groove and a special-shaped groove;

and/or, the first groove or the second groove is independently stuck with at least one layer of silk screen at the edge closest to the axis of the heat pipe type fuel element, and the first groove or the second groove and the silk screen form a composite liquid absorption core structure.

3. The heat pipe fuel element of claim 2, wherein the first groove or the second groove is an Ω -shaped groove.

4. The heat pipe fuel element of claim 1, wherein the first substrate is cylindrical or polygonal;

and/or the length of the first substrate is equal to the length of the second substrate;

and/or, the outer diameter of the first matrix is larger than or equal to the outer diameter of the second matrix;

and/or, the periphery of the first matrix is also coated with a tube shell; the thickness of the tube shell is 1-3 mm;

and/or the second substrate is cylindrical or polygonal.

5. The heat pipe fuel element as defined in claim 4, wherein said first substrate is cylindrical or hexagonal;

and/or, the second matrix is cylindrical.

6. A core comprising a core vessel and a plurality of the heat pipe fuel elements of any one of claims 1 to 5 filled in the core vessel and distributed parallel to the axis of the core vessel.

7. The core of claim 6, further comprising a reflective layer and a plurality of control drums, the control drums being disposed in the reflective layer;

and/or, the core further comprises shutdown control rods;

and/or the reflecting layer is arranged on the periphery of the reactor core container.

8. The core of claim 7, wherein when there are more than two control drums, each control drum is symmetrically distributed in the reflective layer about the central axis of the core vessel.

9. The core of claim 7, wherein the shutdown control rod is disposed in a center of the core.

10. The core of claim 7, wherein the heat pipe fuel elements and the core vessel are connected in a manner comprising two of: mode one: the bottom of the reactor core container is provided with a plurality of moderator channels; the heat pipe type fuel elements are connected with the moderator channels one by one along the direction parallel to the axis of the reactor core container; mode two: the plurality of heat pipe type fuel elements are uniformly distributed in the reactor core container along the direction parallel to the axis of the reactor core container.