A high-safety fuel assembly with temperature measurement and strong current conduction capability

Abstract

This invention belongs to the field of nuclear fuel assembly design technology, specifically relating to a high-safety fuel assembly with temperature-measuring and high-flow-guiding capabilities. It includes a temperature-measuring instrument tube, a high-flow-guiding grid, fuel rods, guide tubes, a lower tube seat to prevent foreign object trapping, and a lower tube seat with low pressure drop, along with their connecting structures. Through the arrangement of these structures and the connection of their components, a high thermal safety margin is achieved in the fuel assembly. By incorporating the temperature-measuring instrument tube, temperature sensors can be placed within it to continuously measure the temperature of the coolant entering from the radially distributed water flow holes in real time. This allows for the determination of the actual thermal safety margin of the fuel assembly, providing feedback for operation and guiding operational strategy optimization, thus achieving low transient and accident incidence rates. By measuring and providing feedback on the coolant temperature at hot spots in the fuel assembly, based on the established safety margin, the fuel assembly and the power plant can operate at safe but as high a parameter as possible for the long term, improving the economics of the nuclear power plant.

Description

Technical Field

[0001] This invention belongs to the field of nuclear fuel assembly design technology, specifically relating to a high-safety fuel assembly with temperature-measurable and high-current conductivity. Background Technology

[0002] During the operation of a nuclear power plant reactor, the performance of nuclear fuel is a crucial factor affecting reactor safety and economics. Operating in a harsh aqueous chemical environment characterized by high temperature, high pressure, high flow rate, and strong radiation, the performance of nuclear fuel directly impacts the economics, safety, and reliability of the nuclear power plant. Therefore, international research on fuel elements has always been given high priority. Through optimizing fuel element design, adopting advanced structural materials, and improving element manufacturing processes, the various performance characteristics of nuclear fuel elements are continuously improved, promoting the development of nuclear power towards a safer and more economical direction.

[0003] Safety and economy are the foundation of nuclear power development, and almost all nuclear power technology development aims to increase these aspects. As the core component of a nuclear power plant reactor, the performance of fuel elements is one of the most significant factors affecting nuclear power safety and economy. Therefore, international research on fuel elements has always been given high priority. Through methods such as optimizing fuel element design, various performance characteristics of nuclear fuel elements are continuously improved, promoting the development of nuclear power towards a safer and more economical direction.

[0004] To meet the economic and safety requirements of advanced nuclear power units, fuel assemblies must possess excellent thermal-hydraulic performance. Existing technologies typically incorporate mixing elements at the corners of fuel rod cells to enhance coolant cooling. For example, US Patent 6144716 uses slots to insert mixing elements at cell corners to improve heat transfer. However, this approach makes it difficult to mix coolant between adjacent cells. Because the neutron flux and power distribution within the reactor core are not uniform, the heat generation within the fuel assemblies is also uneven, necessitating cross-cell mixing to match the power distribution of the fuel assemblies.

[0005] Furthermore, with increasing economic requirements, the actual operating temperature of reactors is constantly rising, further reducing the thermal safety margin of fuel assemblies and decreasing their ability to cope with transients and accidents. Measuring the coolant temperature at hot spots in fuel assemblies to obtain the true thermal safety margin and provide feedback on reactor operation is crucial for the safe operation of nuclear power plants and fuel assemblies. However, current technologies have not yet disclosed a solution for fuel assemblies with high thermal safety margins that simultaneously allow for coolant temperature measurement and operational feedback, as well as strong cross-cell flow conduction. Summary of the Invention

[0006] The purpose of this invention is to provide a high-safety fuel assembly with strong temperature-measuring and high-current conduction capability, in order to address the requirements of matching the power distribution of the fuel assembly with cross-grid mixing through strong current conduction across grid cells, and to obtain the true thermal safety margin of the fuel assembly and provide feedback on reactor operation. This enables the fuel assembly to have good thermal-hydraulic performance to meet the economic and safety requirements of advanced nuclear power units.

[0007] The technical solution of the present invention is as follows:

[0008] A high-safety fuel assembly with temperature measurement and strong flow guidance includes a temperature measurement instrument tube, a strong flow guidance grid, fuel rods, a guide tube, a lower tube seat to prevent foreign object trapping, and an upper tube seat with low pressure drop, as well as their connecting structures.

[0009] The temperature measuring instrument tube has a coolant exchange hole at the hot section of the fuel assembly. The coolant at the hot section enters the temperature measuring instrument tube through the coolant exchange hole to achieve temperature measurement of the fuel assembly.

[0010] The strong flow guide grid is composed of inner strips interlocked with each other and then surrounded by an outer strip; the inner strips and the outer strips are one of the following structures: a structure with springs and rigid protrusions, a spring structure, or a rigid protrusion structure;

[0011] The inner and outer strips are spaced apart to form a grid for placing one of the following components: fuel rod, guide tube, or temperature measuring instrument tube;

[0012] An inner strip guide vane is provided at the coolant outlet end of the inner strip fuel rod grid cell; an outer strip high guide vane and an outer strip low guide vane are provided at the coolant outlet end of the outer strip fuel rod grid cell.

[0013] By setting support structures on the parts of the inner strip that contact the high guide vanes and low guide vanes of the outer strip, the structural integrity of the strong guide grid is ensured during the loading and unloading of fuel assemblies.

[0014] The inner strip guide vane and the outer strip high guide vane are smoothly bent into the fuel rod grid cell. The projected surface covers the corner of the grid cell and the projected edge is an arc concentric with the fuel rod, guiding the low-temperature coolant at the corner of the grid cell to flow around the high-temperature fuel rod.

[0015] The fuel rod is encapsulated and end-plugged, with the active section, fuel positioning structure and heat-conducting gas sealed within it; wherein, the active section refers to the fuel column containing fuel pellets;

[0016] The cladding material is a creep-resistant zirconium alloy;

[0017] The guide tube is one of the following two structures: a zirconium alloy tube with a uniform outer diameter and an inner neck, or a "tube-in-tube" assembly consisting of a straight tube with a larger inner diameter and a uniform wall thickness, with a straight tube of uniform wall thickness placed in the lower part of the tube.

[0018] The anti-foreign object trapping lower tube seat includes a lower tube seat connecting plate, a lower tube seat surrounding plate, and a lower tube seat support leg;

[0019] The low-pressure-drop upper tube seat includes an upper tube seat connecting plate, an upper tube seat surrounding plate, an upper tube seat frame plate, and an upper tube seat spring clamping system.

[0020] Furthermore, in the above-mentioned high-safety fuel assembly with temperature-measuring and strong flow-guiding capability, a throttling orifice is provided at one end of the temperature-measuring instrument tube; and coolant exchange holes are distributed axially and radially in the hot-end section of the fuel assembly.

[0021] Furthermore, in the above-mentioned high-safety fuel assembly with temperature measurement and strong flow guidance, the temperature measuring instrument tube is a straight tube with uniform wall thickness, and 0 to P cooling holes with a diameter of 3 mm are opened as needed at 60% to 100% of the active section region. The value obtained by taking the square root of the coolant flow rate in m / s and rounding it to half is P; the P water flow holes are arranged in axial layers and radially evenly distributed.

[0022] Furthermore, in the above-mentioned high-safety fuel assembly with temperature-measuring and strong flow-guiding capability, the strong flow-guiding grid is composed of 2×(N-1) inner strips interlocked to form a (N-1)×(N-1) arrangement, and then surrounded by an outer strip;

[0023] The inner and outer strips are spaced apart to form N×N grids, of which N×NM fuel rod grids hold fuel rods and M non-fuel rod grids hold guide tubes or temperature measuring instrument tubes.

[0024] 3≤N≤25, 1≤M≤50 and M≤N×N / 4;

[0025] The guide vanes of the strong flow-guiding grid specifically include an inner strip guide vane, an outer strip high guide vane, and an outer strip low guide vane. The guide vanes are smoothly bent into the fuel rod grid element, with a bending radius of 2-10 mm and greater than the unit m / s coolant flow velocity.

[0026] The fuel rods are arranged in an N×NM square within a single fuel assembly;

[0027] The guide tubes are placed in M-1 units in a single fuel assembly.

[0028] Furthermore, in the above-mentioned high-safety fuel assembly with temperature measurement and strong flow guidance, the inner strip guide vane is formed by N bending, the first bending is along the first horizontal baseline of the upper edge of the inner strip, or along the first oblique baseline at an angle of 10-20° with the first horizontal baseline.

[0029] The distance between the horizontal baseline of the Qth bend and the horizontal baseline of the Q-1th bend is 2-5mm.

[0030] The distance between the inclined baseline of the Qth bend and the inclined baseline of the Q-1th bend is 2-5mm; the angle of the Qth bend is smaller than the angle of the Q-1th bend.

[0031] 1 < Q ≤ N.

[0032] Furthermore, in the above-mentioned high-safety fuel assembly with strong temperature measurement and high flow conduction, the temperature measuring instrument tube is arranged and operates on the fuel assembly, and has 12 small holes with a diameter of 3mm at a position 3m to 4m above the lower surface of the active section; the temperature measuring instrument and the core measuring instrument are inserted from the top of it.

[0033] Furthermore, in the above-mentioned high-safety fuel assembly with temperature-measuring and strong flow-guiding capability, the inner strip spring has a bridge-type flow-guiding structure.

[0034] The inner strip rigid protrusion is a buckle-type flow guide structure;

[0035] A flow-guiding structure is set at the flow end of the inner strip to guide the coolant to gather at the corner of the grid cell with the projection of the inner strip guide vane at the upper end, while reducing the degree of turbulence when the fluid reaches the inner strip guide vane.

[0036] Furthermore, in the above-mentioned high-safety fuel assembly with temperature measurement and strong flow guidance, the outer strip guide vane has a high-low configuration, including a high outer strip guide vane and a low outer strip guide vane; when the crossflow direction guided by the outer strip guide vane is the same as that of the inner strip, a high outer strip guide vane with a size of 6mm-10mm is used, and when the crossflow direction guided by the outer strip guide vane is opposite to that of the inner strip, a low outer strip guide vane with a size of 2mm-6mm is used.

[0037] Furthermore, as described above, a high-safety fuel assembly with temperature measurement and strong flow guidance comprises: a temperature measurement instrument tube, 11 layers of strong flow guidance grid, 264 fuel rods, 24 guide tubes, a low-pressure drop upper tube seat, and a foreign object trapping lower tube seat and their connecting structures, arranged in a 17×17 square, with fuel rods having a diameter of 9.5 mm, an active section of 12 feet, and a transverse center-to-center spacing of 12.6 mm;

[0038] The strong flow guide grid is specifically arranged in the axial direction of the fuel assembly as 2 pure structural grids, 6 structural flow guide grids, and 3 pure flow guide grids; wherein, the spacing between the pure structural grids and the structural flow guide grids is 400mm to 650mm, with a preferred value of 522mm; one pure flow guide grid is arranged between each of the 3rd to 6th structural flow guide grids from bottom to top.

[0039] Furthermore, as described above, a high-safety fuel assembly with measurable temperature and strong current conduction can be combined with core design to ensure a thermal safety margin of more than 15% for use in existing reactor cores such as Hualong One.

[0040] Furthermore, the reactor core employs a high-safety fuel assembly with temperature measurement and strong current conduction as described above, wherein: the fuel assemblies are arranged in 15×15 to form 177 cores and / or 157 cores, in 16×16 to form 193 cores, in 17×17 to form 241 cores, in 14×14 to form 121 cores, and in 9×9 to form 57 cores.

[0041] The beneficial effects of the technical solution of this invention are:

[0042] 1. Achieving a high thermal safety margin in fuel assemblies. By using guide vanes that are smoothly bent into the fuel rod cells at the grid outlet, the low-temperature coolant at the corners of the cells is guided to flow around the high-temperature fuel rods. Compared with existing fuel assemblies in China, the coolant mixing effect is improved by 25%, the critical heat flux density of the fuel assembly is increased by 5%, and the thermal safety margin for existing reactor cores such as Hualong One is greater than 15%.

[0043] 2. It realizes thermal safety monitoring and feedback of fuel assemblies. By setting up a temperature-measuring instrument tube, a temperature sensor can be placed inside to continuously measure the temperature of the coolant entering from the radially distributed water flow holes (the coolant has been uniformly mixed with the hot and cold coolant by the strong flow guide grid) in real time. This allows us to know the actual thermal safety margin of the fuel assembly and provide feedback on the operation to guide the optimization of the operation strategy.

[0044] 3. Achieved low incidence of transients and accidents in fuel assemblies. By measuring and providing feedback on the coolant temperature at hot spots in the fuel assemblies, the operating strategy can be adjusted in a timely manner to increase the safety margin when it is insufficient, thereby reducing the probability of transients and accidents, especially temperature-triggered transients and accidents.

[0045] 4. High economic efficiency of fuel assemblies and power plants is achieved. By measuring and providing feedback on the coolant temperature at hot spots in fuel assemblies, and based on the established safety margins, fuel assemblies and power plants can be operated at safe but as high a level as possible for extended periods, thereby improving the economic efficiency of nuclear power plants. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the fuel assembly structure of the present invention.

[0047] Figure 2 This is a schematic diagram illustrating the overall structure of the strong flow guiding grid with inner and outer strips for this invention.

[0048] Figure 3 This is a partial cross-sectional view of the strong flow guiding grid structure of the present invention.

[0049] Figure 4 This is a structural schematic diagram illustrating the assembly of the inner and outer strips of the present invention.

[0050] Figure 5 This is a schematic diagram of the strip structure inside the strong flow guiding grid of the present invention.

[0051] Figure 6 This is a schematic diagram of the strip guide vane structure within the strong flow guide grid of the present invention.

[0052] Figure 7 This is a projected view of the strip guide vanes within the strong flow guide grid of the present invention.

[0053] Figure 8 This is a schematic diagram of the outer strip structure of the strong flow guiding grid of the present invention.

[0054] Figure 9 This is a schematic diagram of the temperature measuring instrument tube structure of the present invention.

[0055] In the diagram: 1. Fuel rod; 2. High-pressure flow guide grid; 3. Guide tube; 4. Temperature measuring instrument tube; 5. Foreign object trapping lower tube seat; 6. Low-pressure drop upper tube seat; 101. Sheath; 102. End plug; 103. Fuel pellet; 104. Fuel positioning structure; 201. Inner strip; 202. Outer strip; 2011. Inner strip guide vane; 2012. Inner strip spring; 2013. Inner strip rigid protrusion; 2014. Support structure; 2015. Projection of the strip guide vane; 2021. Outer strip high guide vane; 2022. Outer strip low guide vane; 2023. Outer strip rigid convexity; 20111. First horizontal baseline; 20112. First oblique baseline; 20113. Second horizontal baseline; 20114. Second oblique baseline; 20115. Q-1th bending angle; 20116. Qth bending angle; 401. Coolant exchange hole; 402. Cooling hole; 403. Throttling hole. Detailed Implementation

[0056] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0057] like Figure 1 As shown, the present invention provides a high-safety fuel assembly with temperature measurement and strong flow guidance, including a temperature measuring instrument tube 4, a strong flow guiding grid 2, a fuel rod 1, a guide tube 3, a foreign object trapping lower tube seat 5, and a low pressure drop upper tube seat 6 and their connection structures;

[0058] The temperature measuring instrument tube 4 has a coolant exchange hole 401 at the hot section of the fuel assembly. The coolant at the hot section enters the temperature measuring instrument tube 4 through the coolant exchange hole 401 to realize the temperature measurement of the fuel assembly.

[0059] like Figure 2 As shown, the strong flow guide grid 2 is composed of inner strips 201 interlocked with each other and then surrounded by outer strips 202; the inner strips 201 and the outer strips 202 are all one of the following structures: a structure with springs and rigid protrusions, a spring structure, or a rigid protrusion structure;

[0060] The inner and outer strips are spaced apart to form a grid for placing one of the following components: fuel rod 1, guide tube 3, temperature measuring instrument tube 4;

[0061] like Figure 3 As shown, an inner strip guide vane 2011 is provided at the coolant outlet end of the inner strip 201 fuel rod grid cell; an outer strip high guide vane 2021 and an outer strip low guide vane 2022 are provided at the coolant outlet end of the outer strip 202 fuel rod grid cell.

[0062] like Figure 4 As shown, by setting a support structure 2014 on the part of the inner strip 201 that contacts the outer strip high guide vane 2021 and the outer strip low guide vane 2022, the structural integrity of the strong guide grid 2 is ensured during the loading and unloading of fuel assemblies.

[0063] The inner strip guide vane 2011 and the outer strip high guide vane are smoothly bent into the fuel rod grid, with the projected surface covering the corner of the grid and the projected edge forming an arc concentric with the fuel rod, guiding the low-temperature coolant at the corner of the grid to flow around the high-temperature fuel rod. Compared with the fuel assemblies currently in service in China, the coolant mixing effect of this structure is improved by 25%, the critical heat flux density of the fuel assembly is improved by 5%, and the thermal safety margin for use in existing reactor cores such as Hualong One is greater than 15%.

[0064] The fuel rod 1 is encapsulated in a shell 101 and an end plug 102, which encapsulate the active section, the fuel positioning structure 104, and the heat-conducting gas; wherein, the active section refers to the fuel column containing the fuel pellet 103;

[0065] The cladding material 101 is a creep-resistant zirconium alloy;

[0066] The guide tube 3 has one of the following two structures: a zirconium alloy tube with a uniform outer diameter and an inner neck, or a straight tube with a uniform wall thickness and a larger inner diameter, with a straight tube with a uniform wall thickness placed in the lower part of the tube.

[0067] The anti-foreign object trapping lower tube seat 5 includes a lower tube seat connecting plate, a lower tube seat surrounding plate, and a lower tube seat support leg;

[0068] The low-pressure-drop upper tube seat 6 includes an upper tube seat connecting plate, an upper tube seat surrounding plate, an upper tube seat frame plate, and an upper tube seat spring clamping system.

[0069] like Figure 9 As shown, a throttling orifice 403 is provided at one end of the temperature measuring instrument tube 4 to limit excessive coolant bypass and improve the efficiency of coolant entering the instrument tube at the hot section of the fuel assembly, avoiding the influence of insufficient discharge of coolant entering the bottom of the instrument tube on the measurement results; the coolant exchange orifice 401 is distributed axially and radially in the hot section of the fuel assembly to ensure sufficient coolant flow to guarantee the temperature measurement results, while ensuring mechanical properties and facilitating processing.

[0070] The temperature measuring instrument tube 4 is a straight tube with uniform wall thickness. 0 to P cooling holes 402 with a diameter of 3 mm are opened as needed at 60% to 100% of the active section area. The value obtained by taking the square root of the coolant flow rate in m / s and rounding it to the nearest integer is P. The P water flow holes are arranged in axial layers and radially evenly distributed.

[0071] The strong flow-guiding grid 2 is formed by interleaving 2×(N-1) inner strips to form (N-1)×(N-1) arrangement, and then surrounding it with an outer strip;

[0072] The inner and outer strips are spaced to form N×N grids, of which N×NM fuel rod grids hold fuel rods 1, and M non-fuel rod grids hold guide tubes 3 or temperature measuring instrument tubes 4.

[0073] 3≤N≤25, 1≤M≤50 and M≤N×N / 4;

[0074] The guide vanes of the strong flow guide grid 2 specifically include an inner strip guide vane 2011, an outer strip high guide vane 2021, and an outer strip low guide vane 2022. The guide vanes are smoothly bent into the fuel rod grid, with a bending radius of 2-10 mm, preferably 6 mm, and greater than the coolant flow rate per unit m / s.

[0075] The fuel rods 1 are arranged in an N×NM square within a single fuel assembly;

[0076] The guide tube 3 has M-1 tubes placed in a single fuel assembly.

[0077] like Figure 6 As shown, the inner strip guide vane 2011 is formed by N bending. The first bending is along the first horizontal baseline 20111 along the upper edge of the inner strip, or along the first oblique baseline 20112 at an angle of 10-20° to the first horizontal baseline.

[0078] The distance between the horizontal baseline of the Qth bend and the horizontal baseline of the Q-1th bend is 2-5mm, preferably 3mm;

[0079] The distance between the inclined baseline of the Qth bend and the inclined baseline of the Q-1th bend is 2-5mm, preferably 3mm; the angle of the Qth bend 20116 is less than the angle of the Q-1th bend 20115.

[0080] 1 < Q ≤ N.

[0081] The temperature-measuring instrument tube 4 is arranged on the fuel assembly, with 12 small holes of 3mm diameter at a distance of 3m to 4m from the lower surface of the active section. Temperature measuring instruments and core measuring instruments are inserted from the top. When temperature sensors or other temperature measuring instruments are placed inside, online real-time continuous measurement of the temperature of the coolant entering from the radially distributed water flow holes (this coolant has been uniformly mixed with hot and cold coolant by the strong flow guide grid) can be achieved. This allows for knowledge of the actual thermal safety margin of the fuel assembly and provides feedback for operation, guiding the optimization of operational strategies. By measuring and providing feedback on the coolant temperature at hot spots in the fuel assembly, operational strategies can be adjusted in a timely manner to increase the safety margin when it is insufficient, reducing the probability of transients and accidents, especially temperature-triggered transients and accidents. At the same time, based on the known safety margin, the fuel assembly and the power plant can operate at safe but as high a parameter as possible for a long time, improving the economics of the nuclear power plant.

[0082] like Figure 5 As shown, the inner strip spring 2012 has a bridge-type flow guiding structure; the inner strip rigid protrusion 2013 has a buckle-type flow guiding structure.

[0083] like Figure 7 As shown, a flow guiding structure is set at the flow end of the inner strip, and combined with matching measures such as increasing the coordination spacing, the coolant is guided to gather at the corner of the grid cell with the inner strip guide vane projection 2015 at the upper end, while reducing the degree of turbulence when the fluid reaches the inner strip guide vane 2011.

[0084] like Figure 8 As shown, the outer strip guide vane has a high-low configuration, including an outer strip high guide vane 2021 and an outer strip low guide vane 2022; when the crossflow direction guided by the outer strip guide vane is the same as that of the inner strip, the outer strip high guide vane 2021 with a size of 6mm-10mm is used, and when the crossflow direction guided by the outer strip guide vane is opposite to that of the inner strip, the outer strip low guide vane 2022 with a size of 2mm-6mm is used.

[0085] Specifically, a high-safety fuel assembly with temperature measurement and strong flow guidance can be combined with the core design to ensure that the thermal safety margin for existing reactor cores such as Hualong One is greater than 15%. It consists of a temperature measurement instrument tube 4, 11 layers of strong flow guidance grid 2, 264 fuel rods 1, 24 guide tubes 3, a low pressure drop upper tube seat 5, and a foreign object trapping lower tube seat 6 and their connecting structures. It is arranged in a 17×17 square, with a fuel rod diameter of 9.5 mm, an active section of 12 feet, and a lateral center-to-center spacing of 12.6 mm.

[0086] The strong flow guide grid 2 is specifically arranged in the axial direction of the fuel assembly as 2 pure structural grids, 6 structural flow guide grids and 3 pure flow guide grids; wherein, the spacing between the pure structural grids and the structural flow guide grids is 400mm to 650mm, with a preferred value of 522mm; one pure flow guide grid is arranged between each of the 3rd to 6th structural flow guide grids from bottom to top.

[0087] The reactor core is constructed using a high-safety fuel assembly with high temperature and strong current conduction as described above, wherein the fuel assemblies are arranged in 15×15 to form 177 cores and / or 157 cores, in 16×16 to form 193 cores, in 17×17 to form 241 cores, in 14×14 to form 121 cores, and in 9×9 to form 57 cores.

[0088] The implementation method of the present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. All contents not described in detail in this specification can be derived from existing technologies.

Claims

1. A high-safety fuel assembly with temperature-measuring and strong current-conducting capability, characterized in that: It includes a temperature measuring instrument tube (4), a strong flow guide grid (2), a fuel rod (1), a guide tube (3), a foreign object trapping lower tube seat (5), and a low pressure drop upper tube seat (6) and their connecting structures; The temperature measuring instrument tube (4) has a coolant exchange hole (401) at the hot section of the fuel assembly. The coolant at the hot section enters the temperature measuring instrument tube (4) through the coolant exchange hole (401) to realize the temperature measurement of the fuel assembly. The strong flow guide grid (2) is composed of inner strips (201) interlocked with each other and then surrounded by an outer strip (202); the inner strips (201) and the outer strips (202) are one of the following structures: a structure with springs and rigid protrusions, a spring structure, or a rigid protrusion structure; The inner and outer strips are spaced apart to form a grid for placing one of the following components: fuel rod (1), guide tube (3), or temperature measuring instrument tube (4); An inner strip guide vane (2011) is provided at the coolant outlet end of the fuel rod grid cell of the inner strip (201); an outer strip high guide vane (2021) and an outer strip low guide vane (2022) are provided at the coolant outlet end of the fuel rod grid cell of the outer strip (202); By setting a support structure (2014) on the part of the inner strip (201) that contacts the outer strip high guide vane (2021) and the outer strip low guide vane (2022), the structural integrity of the strong guide grid (2) is ensured during the loading and unloading of fuel assemblies; The inner strip guide vane (2011) and the outer strip high guide vane are smoothly bent into the fuel rod grid cell. The projected surface covers the corner of the grid cell and the projected edge is an arc concentric with the fuel rod, guiding the low-temperature coolant at the corner of the grid cell to flow around the high-temperature fuel rod. The fuel rod (1) is encapsulated by a shell (101) and an end plug (102) which welds the active section, fuel positioning structure (104) and heat-conducting gas therein; wherein, the active section refers to the fuel column containing fuel pellets (103); The cladding material (101) is a creep-resistant zirconium alloy; The guide tube (3) is one of the following two structures: a zirconium alloy tube with equal outer diameter and inner necking, or a straight tube with equal wall thickness and larger inner diameter with a straight tube of equal wall thickness placed in the lower part of the tube; The anti-foreign object trapping lower tube seat (5) includes a lower tube seat connecting plate, a lower tube seat surrounding plate, and a lower tube seat support leg; The low-pressure-drop upper tube seat (6) includes an upper tube seat connecting plate, an upper tube seat surrounding plate, an upper tube seat frame plate, and an upper tube seat spring clamping system; The temperature measuring instrument tube (4) is provided with a throttling orifice (403) at one end; the coolant exchange orifice (401) is distributed axially and radially in the hot end section of the fuel assembly.

2. The high-safety fuel assembly with temperature-measuring and strong current-conducting capability according to claim 1, characterized in that: The temperature measuring instrument tube (4) is a straight tube with equal wall thickness. At 60% to 100% of the active section area, 0 to P cooling holes (402) with a diameter of 3 mm are opened as needed. The value obtained by taking the square root of the coolant flow rate in m / s and rounding it to half is P. The P water holes are arranged in axial layers and radially evenly distributed.

3. The high-safety fuel assembly with temperature-measuring and strong current-conducting capability according to claim 1, characterized in that: The strong flow-guiding grid (2) is formed by interleaving 2×(N-1) inner strips to form (N-1)×(N-1) arrangement, and then surrounding it with an outer strip; The inner and outer strips are spaced to form N×N grids, of which N×NM fuel rod grids hold fuel rods (1), and M non-fuel rod grids hold guide tubes (3) or temperature measuring instrument tubes (4). 3≤N≤25, 1≤M≤50 and M≤N×N / 4; The guide vanes of the strong flow guide grid (2) specifically include an inner strip guide vane (2011), an outer strip high guide vane (2021) and an outer strip low guide vane (2022). The guide vanes are smoothly bent into the fuel rod grid, and the bending radius is 2-10 mm and greater than the unit m / s coolant flow rate. The fuel rods (1) are arranged in a square shape of N×NM in a single fuel assembly; The guide tube (3) is placed in M-1 places in a single fuel assembly.

4. A high-safety fuel assembly with temperature-measuring and strong current-conducting capability according to claim 1, characterized in that: The inner strip guide vane (2011) is formed by N bends. The first bend is along the first horizontal baseline (20111) along the upper edge of the inner strip, or along the first oblique baseline (20112) at an angle of 10-20° to the first horizontal baseline. The distance between the horizontal baseline of the Qth bend and the horizontal baseline of the Q-1th bend is 2-5mm. The distance between the inclined baseline of the Qth bend and the inclined baseline of the Q-1th bend is 2-5mm; the angle of the Qth bend (20116) is smaller than the angle of the Q-1th bend (20115); 1 < Q ≤ N.

5. A high-safety fuel assembly with temperature-measuring and strong current-conducting capability according to claim 1, characterized in that: The temperature measuring instrument tube (4) is arranged on the fuel assembly, and 12 small holes with a diameter of 3 mm are opened at a position 3m to 4m above the lower surface of the active section; the temperature measuring instrument and the core measuring instrument are inserted from the top of it.

6. A high-safety fuel assembly with temperature-measuring and strong current-conducting capability according to claim 1, characterized in that: The inner strip spring (2012) has a bridge-type flow guiding structure. The inner strip rigid convex (2013) is a buckle-type flow guide structure; A flow-guiding structure is set at the flow end of the inner strip to guide the coolant to gather at the corner of the grid cell with the inner strip guide vane projection (2015) at the upper end, while reducing the degree of turbulence when the fluid reaches the inner strip guide vane (2011).

7. A high-safety fuel assembly with temperature-measuring and strong current-conducting capability according to claim 1, characterized in that: The outer strip guide vane has a high-low configuration, including a high outer strip guide vane (2021) and a low outer strip guide vane (2022). When the crossflow direction generated by the outer strip guide vane is the same as that of the inner stripe, the high outer strip guide vane (2021) with a size of 6mm-10mm is used. When the crossflow direction generated by the outer strip guide vane is opposite to that of the inner stripe, the low outer strip guide vane (2022) with a size of 2mm-6mm is used.

8. A high-safety fuel assembly with temperature-measuring and strong current-conducting capability according to any one of claims 1 to 7, characterized in that: It consists of a temperature measuring instrument tube (4), 11 layers of strong flow guiding grid (2), 264 fuel rods (1), 24 guide tubes (3), a low pressure drop upper tube seat (6) and a foreign object trapping lower tube seat (5) and their connecting structures, arranged in a 17×17 square, with a fuel rod diameter of 9.5 mm, an active section of 12 feet, and a transverse center-to-center spacing of 12.6 mm; The strong flow guide grid (2) is specifically arranged in the axial direction of the fuel assembly as 2 pure structural grids, 6 structural flow guide grids and 3 pure flow guide grids; wherein, the spacing between the pure structural grids and the structural flow guide grids is 400mm to 650mm; and one pure flow guide grid is arranged between the 3rd to 6th structural flow guide grids from bottom to top.

9. A high-safety fuel assembly with temperature-measuring and strong current-conducting capability according to claim 8, characterized in that: The aforementioned high-safety fuel assembly with temperature measurement and strong flow conduction can be combined with core design to ensure a thermal safety margin of more than 15% for use in existing reactor cores.

10. A reactor core constructed using a high-safety fuel assembly with thermometric and high-current conductivity as described in claim 9, characterized in that: The fuel assemblies are arranged in 15×15 configurations for 177 cores and / or 157 cores, in 16×16 configurations for 193 cores, in 17×17 configurations for 241 cores, in 14×14 configurations for 121 cores, and in 9×9 configurations for 57 cores.

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