Nuclear fuel simulation rod

Abstract

The invention discloses a nuclear fuel simulation rod which comprises a simulation pipe body, a first end plug assembly sealed at one end of the simulation pipe body, a second end plug assembly sealed at the other end of the simulation pipe body and a temperature measurement optical fiber. The simulation tube body comprises a heating tube section and an electrode section which are axially connected, and a ceramic layer attached to the inner walls of the heating tube section and the electrode section; the simulation pipe body is filled with inert gas and is matched with the ceramic layer to support and reinforce the heating pipe section; the temperature measuring optical fiber penetrates into the simulation pipe body from the second end plug assembly and extends into the heating pipe section through the electrode section; the heating pipe section is provided with at least one temperature measuring point, and a heat conducting sheet is arranged at the temperature measuring point, arranged on the periphery of the temperature measuring optical fiber and connected with the ceramic layer. According to the nuclear fuel simulation rod, the ceramic layer in the heating pipe section is matched with the filled inert gas for pressurization for supporting and reinforcing, the ceramic layer in the electrode section does not need a high-precision requirement, and the manufacturing cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power engineering tests, and in particular to a nuclear fuel simulation rod. Background Art

[0002] The development of new nuclear fuel assemblies requires a series of thermal hydraulic tests and studies. To simulate the heat release of a nuclear reactor, electric heating of metal pipes is often used. A heating rod simulation that can reflect the axial power distribution of the prototype fuel assembly is designed to carry out relevant research. Therefore, the performance of the electric heating simulation rod is crucial to the relevant research. For non-uniform electric heating rods, metal pipes with variable wall thickness are usually used in domestic and foreign designs. The hollow structure is filled with insulating materials such as ceramics for reinforcement, and thermocouples are installed at different positions to achieve temperature measurement.

[0003] The above structure mainly has the following two problems: 1. Since the heating rod works in a high temperature and high pressure environment, the thin-walled metal tube cannot withstand radial pressure and needs to be reinforced by filling a ceramic layer inside. In order to avoid deformation of the metal tube under high pressure, the internal ceramic must fit closely with it. The processing precision of the ceramic is extremely high and the assembly is relatively difficult. The cost of the ceramic components is very high; 2. Thermocouple temperature measurement is a single-point temperature measurement, but due to the limited inner diameter of the hollow structure of the rod, the number of thermocouples placed is limited, usually a maximum of 7-8. It is difficult to meet the experimental needs of more temperature measurement points. At the same time, different thermocouple positions need to be used in conjunction with different internal ceramic components, and the replaceability is poor. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an improved nuclear fuel simulation rod.

[0005] The technical solution adopted by the present invention to solve its technical problems is: providing a nuclear fuel simulation rod, including a simulation tube body, a first end plug assembly, a second end plug assembly and a temperature measuring optical fiber; the simulation tube body includes a heating tube segment and an electrode segment axially connected, and a ceramic layer attached to the inner walls of the heating tube segment and the electrode segment; the first end plug assembly is sealed at the end of the heating tube segment away from the electrode segment, and the second end plug assembly is sealed at the end of the electrode segment away from the heating tube segment; the simulation tube body is filled with an inert gas, and cooperates with the ceramic layer to support and reinforce the heating tube segment;

[0006] The temperature measuring optical fiber passes through the simulation tube body from the second end plug assembly, and extends through the electrode segment to the heating tube segment; the heating tube segment is provided with at least one temperature measuring point, and a heat conducting plate is provided at the temperature measuring point, and the heat conducting plate is arranged on the periphery of the temperature measuring optical fiber and connected to the ceramic layer.

[0007] In some embodiments, the first end plug assembly includes a first plug body, a second plug body and a one-way valve;

[0008] The first plug body is connected to the end of the heating pipe segment away from the electrode segment, and the first plug body is provided with an air filling hole connected to the heating pipe segment, and the one-way valve is arranged in the air filling hole;

[0009] The second plug body is connected to the first plug body to seal the inflation hole.

[0010] In some embodiments, the heating pipe segment is a metal pipe with a reduced inner diameter; the electrode segment includes a first metal pipe and a second metal pipe connected in sequence to the heating pipe segment;

[0011] The inner diameters of the first metal tube and the second metal tube are smaller than the minimum inner diameter of the heating tube section.

[0012] In some embodiments, the heating tube segment is a metal alloy; the first metal tube is a nickel tube, and the second metal tube is a copper tube.

[0013] In some embodiments, the inner diameter of the inner channel of the heating tube segment gradually increases from opposite ends of the inner channel to the middle position.

[0014] In some embodiments, the internal channel of the heating pipe segment includes a first channel, a second channel, a third channel and a fourth channel which are axially connected; the inner diameter of the first channel is less than the inner diameter of the second channel and less than the inner diameter of the third channel, and the inner diameter of the fourth channel is equal to the inner diameter of the second channel.

[0015] In some embodiments, the outer diameters of the first end plug assembly, the heater tube segment, and the electrode segment are equal.

[0016] In some embodiments, the second end plug assembly includes a spring plug; at the end of the electrode segment, the spring plug presses against the edge of the ceramic layer in the electrode segment;

[0017] The gap between the spring plug and the electrode segment, and the gap between the temperature measuring optical fiber and the spring plug are filled and sealed by high-temperature glue.

[0018] In some embodiments, the ceramic layer includes a first ceramic layer located in the heating tube segment and a second ceramic layer located in the electrode segment; the first ceramic layer is a finished ceramic layer.

[0019] In some embodiments, the first end plug assembly is made of metal nickel; and the heat conductive sheet is a copper sheet.

[0020] The beneficial effects of the present invention are as follows: the simulated tube body of the nuclear fuel simulation rod is constructed by connecting the heating tube segment and the electrode segment in sections, so that the ceramic layer therein is also divided into two parts. It is only necessary to make the accuracy of the ceramic layer in the heating tube segment meet the tight-fitting effect, and to support and reinforce it with the inert gas pressurization. The ceramic layer in the electrode segment does not require high precision, thereby reducing the cost; temperature measurement is carried out by temperature measuring optical fiber, which can realize multi-point continuous temperature measurement with one optical fiber, thereby meeting the test requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0022] Figure 1 is a schematic cross-sectional structure diagram of a nuclear fuel simulation rod according to an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the cross-sectional structure of a nuclear fuel simulation rod according to another embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0025] like Figure 1 and Figure 2 As shown, the nuclear fuel simulation rod of the present invention comprises a simulation tube body, a first end plug assembly 40 and a second end plug assembly 50 respectively sealed at opposite ends of the simulation tube body, and a temperature measuring optical fiber 60 for monitoring temperature. The temperature measuring optical fiber 60 penetrates into the simulation tube body and extends along the axial direction of the simulation tube body to measure the temperature at positions at different heights on the surface of the simulation tube body where temperature measurement is required.

[0026] The simulated pipe body includes a heating pipe segment 10 and an electrode segment 20 connected axially, and a ceramic layer 30 attached to the inner walls of the heating pipe segment 10 and the electrode segment 20. The first end plug assembly 40 is sealed at the end of the heating pipe segment 10 away from the electrode segment 20, and the second end plug assembly 50 is sealed at the end of the electrode segment 20 away from the heating pipe segment 10. The temperature measuring point is set on the heating pipe segment 10.

[0027] The first end plug assembly 40 and the second end plug assembly 50 form a closed chamber inside the simulated tube body, and the simulated tube body is filled with inert gas. A certain air pressure is formed by the filled inert gas, and the heating tube segment 10 is pressurized to improve the structural strength of the heating tube segment 10 so that it does not deform during the high temperature and high pressure experiment.

[0028] The inert gas includes but is not limited to helium. The heating pipe section 10 is formed by a precision-machined metal pipe.

[0029] The outer diameters of the first end plug assembly 40, the heating tube segment 10 and the electrode segment 20 are equal, so that the nuclear fuel simulation rod is a rod body with equal outer diameters in appearance.

[0030] Specifically, the heating pipe section 10 is a metal pipe with a reduced inner diameter.

[0031] In one embodiment, if Figure 1 As shown, the inner diameter of the inner channel of the heating pipe segment 10 gradually increases from the two opposite ends of the inner channel to the middle position, so that the wall thickness of the heating pipe segment 10 gradually decreases from the two opposite ends of the heating pipe segment 10 to the middle position, that is, the wall thickness of the heating pipe segment 10 is large at the two ends and small (thin) in the middle. A plurality of temperature measuring points can be set on the heating pipe segment 10 with axial spacing, and the specific number and spacing distance can be set according to needs.

[0032] In another embodiment, if Figure 2 As shown, the internal channel of the heating pipe segment 10 includes a first channel 11, a second channel 12, a third channel 13 and a fourth channel 14 connected axially; the inner diameter of the first channel 11 is less than the inner diameter of the second channel 12 and less than the inner diameter of the third channel 13, and the inner diameter of the fourth channel 14 is equal to the inner diameter of the second channel 12. In combination with the variable diameter setting of the inner diameter of the heating pipe segment 10, the ceramic layer 30 in the heating pipe segment 10 is also set corresponding to the change of the inner diameter, so that the ceramic layer 30 in the first channel 11 to the fourth channel 14 is all fitted with the corresponding inner wall. The electrode segment 20 is connected to one end of the heating pipe segment 10 and is directly connected to the fourth channel 14. The electrode segment 20 may further include a first metal tube 21 and a second metal tube 22 connected axially, and the electrode segment 20 is connected to the heating pipe segment 10 with the first metal tube 21. The inner diameters of the first metal tube 21 and the second metal tube 22 are smaller than the minimum inner diameter of the heating pipe segment 10. Among the four channels of the heating pipe section 10 , the first channel 11 has the smallest inner diameter, and the inner diameters of the first metal tube 21 and the second metal tube 22 are smaller than the inner diameter of the first channel 11 .

[0033] In the electrode segment 20 , the first metal tube 21 is preferably a nickel tube, and the second metal tube 22 is preferably a copper tube.

[0034] The heating pipe section 10 is made of nickel-based alloy, zirconium alloy or other metal alloys.

[0035] Corresponding to the heating pipe segment 10 and the electrode segment 20 , the ceramic layer 30 in the simulation pipe segment includes a first ceramic layer 31 and a second ceramic layer 32 . The first ceramic layer 31 is located in the heating pipe segment 10 , and the second ceramic layer 32 is located in the electrode segment 20 .

[0036] The temperature measurement point is mainly located on the heating pipe section 10, and the first ceramic layer 31 is a finely processed ceramic layer with high precision. The gas pressure provided by the inert gas filled in makes the first ceramic layer 31 fit closely with the inner wall of the heating pipe section 10. The electrode section 20 is a non-temperature measurement section, so the second ceramic layer 32 therein does not need to be finely processed, which reduces the cost.

[0037] The temperature measuring optical fiber 60 is mainly used to measure the temperature of the temperature measuring point of the heating pipe section 10. To this end, a heat conducting sheet 15 may be provided at the position corresponding to the temperature measuring point in the heating pipe section 10. The heat conducting sheet 15 is arranged on the outer periphery of the temperature measuring optical fiber 60 and connected to the ceramic layer 30 (specifically connected to the first ceramic layer 31). The heat of the temperature measuring point is transferred to the temperature measuring optical fiber 60 through the heat conducting sheet 15, thereby obtaining the temperature of the temperature measuring point.

[0038] exist Figure 1 In the illustrated embodiment, each temperature measuring point in the heating pipe section 10 is provided with a heat conducting sheet 15 to connect the ceramic layer 30 (specifically the first ceramic layer 31 ) where it is located with the temperature measuring optical fiber 60 .

[0039] The heat conducting sheet 15 may preferably be a copper sheet.

[0040] The first end plug assembly 40 can be fixedly connected to the end of the heating pipe section 10 by welding or the like. In order to meet the inflation requirement after the simulated pipe body is closed, the first end plug assembly 40 is provided in a split body.

[0041] Alternatively, the first end plug assembly 40 includes a first plug body 41 and a one-way valve 43. The first plug body 41 is provided with an air filling hole 410 running through its opposite ends, and the opening of the air filling hole 410 makes the first plug body 41 form a cylindrical structure. The first plug body 41 is fixedly connected to the end of the heating pipe segment 10 away from the electrode segment 20, and the air filling hole 410 is connected to the inside of the heating pipe segment 10. The one-way valve 43 is arranged in the air filling hole 410, controls the opening and closing of the air filling hole 410, and allows gas to enter the heating pipe segment 10, restricts the gas from being output from the heating pipe segment 10 to the outside, and realizes the primary sealing of the heating pipe segment 10. The first end plug assembly 40 may also include a second plug body 42, which is a block metal body, and can be fixedly connected to the first plug body 41 by welding or the like, so as to seal the air filling hole 410, thereby also sealing the one-way valve 43 in the first plug body 41, and realizing the secondary sealing of the heating pipe segment 10.

[0042] The outer diameters of the first plug body 41 and the second plug body 42 are equal to the outer diameter of the heating pipe section 10 , so that the outer peripheral surfaces of the second plug body 42 , the first plug body 41 and the heating pipe section 10 are flush with each other.

[0043] The first plug body 41 and the second plug body 42 are preferably made of metal nickel.

[0044] The second end plug assembly 50 is fitted at the end of the electrode segment 20 away from the heating tube segment 10 and seals the end. At the same time, the second end plug assembly 50 presses against the edge of the ceramic layer 30 (specifically the second ceramic layer 32) in the electrode segment 20 to improve the stability of the ceramic layer 30 in the simulation tube.

[0045] In one embodiment, the second end plug assembly 50 includes a spring plug. In another embodiment, the second end plug assembly 50 includes a plug body or a bolt, which can be fixed to the end of the electrode segment 20 by welding or screwing, respectively.

[0046] The temperature measuring optical fiber 60 penetrates into the simulated tube body from the second end plug assembly 50, and extends through the electrode segment 20 to the heating tube segment 10, so as to effectively measure the temperature of the heating tube segment 10. The temperature measuring principle of the temperature measuring optical fiber 60 is different from that of the thermocouple, and can break through the space limitation of the hollow rod bundle and measure the temperature at any point of the axial height.

[0047] In the heating pipe section 10, the connection between the heat conducting sheet 15 at the temperature measuring point and the temperature measuring optical fiber 60 and the ceramic layer 30 not only plays a role in heat transfer, but also helps to position the temperature measuring optical fiber 60 in the middle of the heating pipe section 10 to avoid displacement, bending and other problems.

[0048] The temperature measuring optical fiber 60 is a metalized optical fiber coated with a metal layer, and is suitable for use in high temperature and high pressure environments.

[0049] In order to further improve the sealing performance, the gap between the second end plug assembly 50 and the electrode segment 20 and the gap between the temperature measuring optical fiber 60 and the second end plug assembly 50 are filled and sealed by high temperature glue.

[0050] The first end plug assembly 40 and the lower end of the electrode segment 20 (the lower end of the second metal tube 22 ) are used to connect the positive and negative electrodes of the power supply respectively during the experiment.

[0051] The nuclear fuel simulation rod of the present invention is a non-uniform electric heating rod, which is suitable for various thermal hydraulic simulation experiments of fuel assemblies. Compared with the existing non-uniform electric heating rods in China, it has the following advantages:

[0052] Except for the ceramic layer at the temperature measurement point (the first ceramic layer 31) which requires high processing precision and is close to the inner wall, the processing precision requirements of the ceramic layers at other locations are relatively low, so the cost is low and the manufacturing process is convenient;

[0053] The seal is reliable and the structure is stable. The rod is filled with inert gas of appropriate pressure, and the ceramic layer makes the structure inside the rod stable and does not deform during high temperature and high pressure experiments.

[0054] It is easy to disassemble and assemble, and the temperature measurement is efficient and reliable. Helium is filled into the rod through a one-way valve, which is easy to operate. At the same time, optical fiber temperature measurement is used, which is efficient and accurate.

[0055] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A nuclear fuel simulation rod, characterized in that: The invention comprises a simulated tube body, a first end plug assembly, a second end plug assembly and a temperature measuring optical fiber; the simulated tube body comprises a heating tube segment and an electrode segment connected axially, and a ceramic layer attached to the inner walls of the heating tube segment and the electrode segment; the first end plug assembly is sealed at the end of the heating tube segment away from the electrode segment, and the second end plug assembly is sealed at the end of the electrode segment away from the heating tube segment; the simulated tube body is filled with an inert gas, and cooperates with the ceramic layer to support and reinforce the heating tube segment; The temperature measuring optical fiber passes through the simulation tube body from the second end plug assembly, and extends through the electrode segment to the heating tube segment; the heating tube segment is provided with at least one temperature measuring point, and a heat conducting plate is provided at the temperature measuring point, and the heat conducting plate is arranged on the periphery of the temperature measuring optical fiber and connected to the ceramic layer.

2. The nuclear fuel simulation rod according to claim 1, characterized in that: The first end plug assembly comprises a first plug body, a second plug body and a one-way valve; The first plug body is connected to the end of the heating pipe segment away from the electrode segment, and the first plug body is provided with an air filling hole connected to the heating pipe segment, and the one-way valve is arranged in the air filling hole; The second plug body is connected to the first plug body to seal the inflation hole.

3. The nuclear fuel simulation rod according to claim 1, characterized in that: The heating pipe section is a metal pipe with a reduced inner diameter; the electrode section includes a first metal pipe and a second metal pipe connected in sequence to the heating pipe section; The inner diameters of the first metal tube and the second metal tube are smaller than the minimum inner diameter of the heating tube section.

4. The nuclear fuel simulation rod according to claim 3, characterized in that: The heating tube section is made of metal alloy; the first metal tube is a nickel tube, and the second metal tube is a copper tube.

5. The nuclear fuel simulation rod according to claim 3, characterized in that: The inner diameter of the inner channel of the heating pipe section gradually increases from the opposite ends of the inner channel to the middle position.

6. The nuclear fuel simulation rod according to claim 3, characterized in that: The internal channel of the heating pipe section includes a first channel, a second channel, a third channel and a fourth channel which are axially connected; The inner diameter of the first channel is smaller than the inner diameter of the second channel and smaller than the inner diameter of the third channel, and the inner diameter of the fourth channel is equal to the inner diameter of the second channel.

7. The nuclear fuel simulation rod according to claim 1, characterized in that: The outer diameters of the first end plug assembly, the heating tube segment and the electrode segment are equal.

8. The nuclear fuel simulation rod according to claim 1, characterized in that: The second end plug assembly comprises a spring plug; at the end of the electrode segment, the spring plug presses against the edge of the ceramic layer in the electrode segment; The gap between the spring plug and the electrode segment, and the gap between the temperature measuring optical fiber and the spring plug are filled and sealed by high-temperature glue.

9. The nuclear fuel simulation rod according to any one of claims 1 to 8, characterized in that: The ceramic layer includes a first ceramic layer located in the heating tube segment and a second ceramic layer located in the electrode segment; the first ceramic layer is a finely processed ceramic layer.

10. The nuclear fuel simulation rod according to any one of claims 1 to 8, characterized in that: The first end plug assembly is made of metal nickel; the heat conducting sheet is a copper sheet.

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