Power transient irradiation device applicable to sheet components and power partition measurement method

Abstract

The present invention discloses a power transient irradiation device and a power partition measurement method applicable to sheet components, relating to the technical field of reactor irradiation, including: a square box, the inner cavity of the square box is an internal flow channel for cooling water to pass through, and a plurality of sheet fuel elements are evenly distributed at intervals from bottom to top in the internal flow channel; a plurality of spiral tube helium screens, the plurality of spiral tube helium screens correspond to the plurality of sheet fuel elements one by one, and the spiral tube helium screens are wound around the outside of the square box, and adjacent spiral tube helium screens are communicated with each other; both ends of the fuel section of the sheet fuel element are located between both ends of the corresponding spiral tube helium screen. An axial multi-layer sheet fuel arrangement scheme is adopted, which can carry multiple sheet fuel elements at the same time, and each layer of fuel element can be matched with spiral tube helium screens with different pipe inner diameters and winding pitches to achieve different power change amplitudes for fuel elements at different positions, so as to greatly expand the power transient test capacity and test parameter range of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of reactor irradiation, and particularly to a power transient irradiation device suitable for sheet elements and a power partition measurement method. Background Art

[0002] The performance of pressurized water reactor fuel elements is directly related to the safety and economy of the reactor. Conducting in-reactor irradiation tests on fuel elements is a key link in the research and design of fuel elements. Fuel element power transient irradiation tests are generally carried out on research reactors using special power transient irradiation test devices; by changing the power of fuel elements within a short period of time, the performance parameters and safety margins of fuel elements are verified. In order to conduct power transient irradiation tests on pressurized water reactor fuel elements in a research reactor, some foreign research reactors, such as the HBWR reactor in Norway, the BR2 reactor in Belgium, the R2 reactor in Sweden, and the JMTR reactor in Japan, adopt a helium-3 gas loop as the power adjustment device for fuel elements. By changing the pressure of gaseous neutron poison ( 3 He gas) in the helium screen in the research reactor, the irradiation power of the test fuel elements is effectively adjusted.

[0003] The helium screen of the helium-3 gas loop and a part of the helium gas pipeline connected thereto are located in the active zone of the research reactor core; the 3 He gas in the helium screen and a part of the helium gas pipeline absorbs thermal neutrons in the reactor and generates tritium ( 3 H) with radioactive hazards. Tritium is an isotope of hydrogen, and gaseous tritium has a strong penetration ability; tritium at a higher temperature can easily penetrate the container made of metal materials and then leak into the environment. The penetration ability of tritium increases sharply with the increase of its own temperature.

[0004] Since the sheet fuel element has a thin plate structure with a rectangular cross-section, the power change range of the fuel element for the traditional helium screen structure is greatly reduced. It is necessary to carry out innovative helium screen design to achieve a large increase in fuel power transient tests. On the other hand, due to the large power difference of fuel elements at different positions in a single test, the traditional heat balance method can only measure the total heat release power of multiple fuel elements. Therefore, it is necessary to develop corresponding methods to achieve real-time measurement of the power of fuel elements at different positions during the fuel power transient test. Summary of the Invention

[0005] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a power transient irradiation device suitable for sheet elements and a power partition measurement method, which adopt an axial multi-layer sheet fuel arrangement scheme, can carry multiple sheet fuel elements at the same time, and each layer of fuel elements can be equipped with a helical tube helium screen with different pipe inner diameters and winding pitches to achieve different power change amplitudes corresponding to fuel elements at different positions, so as to greatly expand the power transient test ability and test parameter range of the device.

[0006] The present invention is realized by the following technical solutions:

[0007] A power transient irradiation device applicable to sheet elements, comprising:

[0008] A square box with both the upper and lower ends open. The inner cavity of the square box is an internal flow channel for cooling water to pass through. A number of sheet fuel elements are evenly distributed at intervals from bottom to top in the internal flow channel. The number of sheet fuel elements are placed vertically and are located on the same vertical plane;

[0009] A number of spiral tube helium screens, which correspond to the number of sheet fuel elements one by one. The spiral tube helium screens are wound around the outside of the square box, and adjacent spiral tube helium screens are interconnected; the lower end of the lowermost spiral tube helium screen is connected to a helium inlet pipe, and the upper end of the uppermost spiral tube helium screen is connected to a helium outlet pipe;

[0010] Both ends of the fuel section of the sheet fuel element are located between the two ends of the corresponding spiral tube helium screen.

[0011] Compared with the prior art, the helium screen of the helium-3 gas circuit and the part of the helium gas pipeline connected thereto are located in the active zone of the research reactor core; the 3 He gas in the helium screen and part of the helium gas pipeline absorbs thermal neutrons in the reactor, generating tritium ( 3 H) with radioactive hazards. Tritium is an isotope of hydrogen, and gaseous tritium has a strong penetration ability; tritium at a higher temperature can easily penetrate the container made of metal materials and then leak into the environment. The penetration ability of tritium increases sharply with the increase of its own temperature; and because the sheet fuel element is a thin plate structure with a rectangular cross-section, the traditional helium screen structure greatly reduces the power change range of the fuel element, and due to the large power difference of the fuel elements at different positions in a single test, the traditional thermal equilibrium method can only measure the total heat release power of multiple fuel elements and other problems. The present invention provides a power transient irradiation device applicable to sheet elements, which adopts an axial multi-layer sheet fuel arrangement scheme, can carry multiple sheet fuel elements at the same time, and each layer of fuel elements can be matched with spiral tube helium screens with different pipe inner diameters and winding pitches, so as to achieve different power change amplitudes corresponding to fuel elements at different positions, thereby greatly expanding the power transient test ability and test parameter range of the device.

[0012] In a specific solution, it includes a square box, a spiral tube helium shield, a helium inlet pipe, and a helium outlet pipe. The spiral tube helium shield is successively wound around the outside of the square box in a spiral direction. At this time, several spiral tube helium shields, such as the first spiral tube helium shield, the second spiral tube helium shield, and the third spiral tube helium shield, are interconnected. The gas pipelines between the spiral tube helium shields at different positions can preferably be connected by welding. The lower end of the third spiral tube helium shield located at the bottom is connected to the helium inlet pipe, and the upper end of the first spiral tube helium shield located at the top is connected to the helium outlet pipe. In this way, helium gas ( 3 He gas) can be filled into several spiral tube helium shields. The helium-3 gas enters from the helium inlet pipe, flows through several spiral tube helium shields, and finally flows out through the helium outlet pipe. In addition, there is an inner cavity inside the square box, that is, an inner flow channel for cooling water to pass through. Several sheet-shaped fuel elements are evenly distributed at intervals along the axial direction of the inner flow channel, that is, N sheet-shaped fuel elements are arranged vertically in a row. The array of sheet-shaped fuel elements is in the shape of a thin cuboid and is fixed in shape and position by corresponding fixing structures. In this way, the cooling water entering the square box will be divided into two parts by the sheet-shaped fuel elements. After being heated and raised in temperature by the fuel elements, it re-converges at the top of the sheet-shaped fuel element array and then enters the inner flow channel of the intermediate joint area. Each layer of sheet-shaped fuel elements corresponds to an independent spiral tube helium shield. In this way, a large power jump of the sheet-shaped fuel elements can be achieved through the spiral tube helium shield. In addition, for the spiral tube helium shield corresponding to each layer of sheet-shaped fuel elements, the diameter of the pipeline and the pitch of the spiral tube can be independently set, so that different power change amplitudes can be achieved for the sheet-shaped fuel elements at different positions under the same helium-3 gas pressure change range. Among them, both ends of the fuel section of the sheet-shaped fuel element are located between the two ends of the corresponding spiral tube helium shield. Preferably, the axial position and length of the spiral tube helium shield are the same as those of the corresponding sheet-shaped fuel element.

[0013] The above solution aims to achieve: adopting an axial multi-layer sheet-shaped fuel arrangement scheme, multiple sheet-shaped fuel elements can be carried at the same time, improving the utilization rate of the irradiation space in the irradiation channel; while achieving a large power jump of the sheet-shaped fuel through the spiral tube helium shield, each layer of fuel elements can be paired with a spiral tube helium shield with different inner pipe diameters and winding pitches to achieve different power change amplitudes for fuel elements at different positions, so as to greatly expand the power transient test capacity and test parameter range of the device. In addition, the spiral tube helium shield is located outside the inner flow channel for cooling the sheet-shaped fuel element, reducing the influence of the heat release of the helium-3 gas and its helium shield structural material on the measurement of the fuel heat release power, and improving the accuracy of the measurement of the heat release power of the sheet-shaped fuel element. The spiral tube helium shield does not contact the relatively high-temperature cooling water for cooling the sheet-shaped fuel element, which reduces the temperature of the helium pipeline and the tritium-containing helium gas in the pipeline to a certain extent, thus facilitating the reduction of the tritium permeation and leakage ability.

[0014] As a pressure boundary to form a coolant channel, it further includes a pressure tube. Both the square box and the helical tube helium shield are located inside the chamber of the pressure tube. The pressure tube is provided with a cooling water inlet, and the cooling water inlet is located above the helical tube helium shield. The lower end of the square box is communicated with the bottom of the pressure tube, and the upper end of the square box is communicated with a cooling water outlet. In this solution, the pressure tube is a thick-walled cylindrical structure made of stainless steel material, which serves as a pressure boundary to accommodate cooling water with typical pressurized water reactor environmental parameters. In this way, the cooling water can flow in from the upper cooling water inlet and flow downward along the outer flow channel, thereby cooling the pressure tube and the helical tube helium shield. Subsequently, it turns back upward at the bottom of the pressure tube and the outer tube, and then passes through the inner flow channel. After flushing and cooling the plate-shaped fuel elements, it flows out from the coolant outlet.

[0015] To completely separate the outer flow channel and the inner flow channel, it further includes a shunt tube. One end of the shunt tube is communicated with the upper end of the square box through an intermediate joint, and the other end of the shunt tube penetrates through the pressure tube.

[0016] To reduce heat transfer, it further includes a protection tube. The pressure tube and the protection tube are coaxial and arranged in sequence from the inside to the outside. The chamber between the inner side of the protection tube and the outer side of the pressure tube is a nitrogen chamber. In this solution, the protection tube is located outside the pressure tube and is also a cylindrical structure. The chamber between the two is a nitrogen chamber filled with normal-pressure nitrogen, which is respectively connected to a nitrogen inlet and a nitrogen outlet.

[0017] To reduce the heat exchange between the cooling water in different flow channels inside and outside the tube and provide a measurement lead channel, both the shunt tube and the square box adopt a first double-layer tube structure, and the gap in the first double-layer tube structure is filled with nitrogen.

[0018] To further prevent tritium in the helical tube helium shield and the connected helium pipelines from permeating and leaking into the cooling water, the helical tube helium shield, the helium inlet pipe, and the helium outlet pipe all adopt a second double-layer tube structure with a filling layer. The second double-layer tube structure includes an inner layer tube, a filling layer filled with sponge-like metallic titanium tubes, and an outer layer tube in sequence from the inside to the outside. Both the inner layer tube and the outer layer tube are made of stainless steel material with a dense Al2O3 coating. In this solution, a helium pipeline with a double-layer stainless steel tube structure with a sandwich is adopted, and both layers of the double-layer tube are designed with Al2O3 coating. The inner layer tube accommodates tritium-containing helium, which can prevent tritium in the helium shield and the connected helium pipelines from permeating and leaking into the cooling water, thereby effectively reducing the radioactive hazard caused by tritium leakage.

[0019] To online monitor the thermal neutron fluence rate near different sheet fuel elements, so as to accurately measure the relative power distribution of sheet fuel elements at different positions during the power transient test, a measurement head of a self-powered neutron detector is installed at the central area of the wide side of each said sheet fuel element, and the measurement heads of several said self-powered neutron detectors are all located in the square box. In this solution, the self-powered neutron detector is preferably arranged to be implanted in the hollow sandwich layer of the square box, and the number of detectors is the same as the number of sheet fuel elements. Each detector corresponds to one layer of sheet fuel elements, and its installation position is close to the central area of the wide side of the sheet fuel element. The self-powered neutron detectors arranged in the device can online monitor the thermal neutron fluence rate near different sheet fuel elements; thus, the relative power distribution of sheet fuel elements at different positions can be accurately measured during the power transient test.

[0020] To measure the temperature rise of the cooling water in the inner flow channel in the fuel area, several fuel section inlet thermocouples are arranged below the lowermost said sheet fuel element; several fuel section outlet thermocouples are arranged above the uppermost said sheet fuel element. Among them, by measuring the temperature rise of the cooling water in the test fuel area and using the cooling water flow rate measured by an external system connected to the device, the total heat release power of all sheet fuel elements can be obtained.

[0021] A further solution, a power partition measurement method for a power transient irradiation device applicable to sheet elements, includes the following steps:

[0022] Measure the temperature of the cooling water at the inlet of the lower end of the inner flow channel and the temperature of the cooling water at the outlet of the upper end respectively, obtain the temperature rise of the cooling water in the test fuel area, and measure the cooling water flow rate through an external system, so as to obtain the total heat release power of all said sheet fuel elements;

[0023] Online measure the relative power distribution of each said sheet fuel element;

[0024] Through the relative power distribution of each said sheet fuel element and in combination with the total heat release power, the power data of each sheet fuel element during the fuel power transient test can be measured in real time.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] 1) The power transient irradiation device and the power partition measurement method applicable to sheet elements provided by the present invention adopt an axial multi-layer sheet fuel arrangement scheme, which can carry multiple sheet fuel elements at the same time, improving the utilization rate of the irradiation space in the irradiation channel.

[0027] 2) The power transient irradiation device and power partition measurement method for sheet elements provided by the present invention are equipped with a helical tube helium screen with different pipe inner diameters and winding pitches for each layer of fuel elements, so as to achieve different power change amplitudes corresponding to fuel elements at different positions, thereby greatly expanding the power transient test capacity and test parameter range of the device.

[0028] 3) The power transient irradiation device and power partition measurement method for sheet elements provided by the present invention measure the total heat release power of the fuel using the traditional thermal equilibrium method, and combine the relative power distribution data of different fuel elements obtained by online measurement of SPND at different positions to achieve real-time independent measurement of the power of all fuel elements during the power transient test.

[0029] 4) The power transient irradiation device and power partition measurement method for sheet elements provided by the present invention adopt a double-layer tube structure design for both the square box and the flow splitter tube, effectively reducing the heat exchange of the cooling water between the inner and outer flow channels. At the same time, the helium screen is located outside the square box, reducing the influence of the heat release of helium-3 gas and its helium screen structural materials on the measurement of the fuel heat release power and improving the accuracy of the heat release power measurement.

[0030] 5) The power transient irradiation device and power partition measurement method for sheet elements provided by the present invention have the helium screen located inside the pressure tube and close to the sheet fuel element, which can effectively increase the power change amplitude of the fuel.

[0031] 6) The power transient irradiation device and power partition measurement method for sheet elements provided by the present invention adopt a helium gas pipeline with a double-layer stainless steel tube structure with a sandwich, and both layers of the tube are designed with Al2O3 coating, which can effectively reduce the permeation and leakage of tritium in the helium gas pipeline.

[0032] 7) The present invention can be applied to the design of in-pile devices for fuel power transient test loops using a helium-3 gas circuit, and ultimately used for power transient irradiation tests of sheet fuel elements in research reactors and partition power measurement of fuel elements at different positions. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings. In the drawings:

[0034] Figure 1 is a schematic structural diagram of the power transient irradiation device provided by the present invention;

[0035] Figure 2A-A cross-sectional view of the power transient irradiation device provided by the present invention;

[0036] Figure 3 B-B cross-sectional view of the power transient irradiation device provided by the present invention;

[0037] Figure 4 Schematic structural diagram of the helical tube helium shield provided by the present invention.

[0038] Reference numerals in the drawings and corresponding component names:

[0039] 1 - protection tube; 2 - nitrogen cavity; 3 - pressure tube; 4 - helical tube helium shield; 401 - first helical tube helium shield, 402 - second helical tube helium shield, 403 - third helical tube helium shield; 5 - square box; 6 - plate-shaped fuel element; 7 - outer flow channel; 8 - inner flow channel; 9 - shunt tube; 10 - nitrogen inlet; 11 - nitrogen outlet; 12 - cooling water inlet; 13 - cooling water outlet; 14 - fuel section inlet thermocouple; 15 - fuel section outlet thermocouple; 16 - self-powered neutron detector; 17 - helium outlet pipe; 18 - helium inlet pipe. Detailed implementation manners

[0040] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in combination with embodiments and drawings. The illustrative embodiments and descriptions thereof of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0041] Embodiment 1

[0042] Embodiment 1 of the present invention provides a power transient irradiation device applicable to plate-shaped elements, as Figures 1 - 4 shown, including:

[0043] A square box 5 with both the upper and lower ends open. The inner cavity of the square box 5 is an inner flow channel 8 for cooling water to pass through. In the inner flow channel 8, a plurality of plate-shaped fuel elements 6 are evenly distributed at intervals from bottom to top. The plurality of plate-shaped fuel elements 6 are placed vertically and are located in the same vertical plane;

[0044] A plurality of helical tube helium shields 4, which correspond to the plurality of plate-shaped fuel elements 6 one by one. The helical tube helium shields 4 are wound around the outside of the square box 5, and adjacent helical tube helium shields 4 are communicated with each other; the lower end of the lowermost helical tube helium shield 4 is communicated with the helium inlet pipe 18, and the upper end of the uppermost helical tube helium shield 4 is communicated with the helium outlet pipe 17;

[0045] Both ends of the fuel section of the plate-shaped fuel element 6 are located between the two ends of the corresponding helical tube helium shield 4.

[0046] In the prior art, the helium screen of the helium-3 gas circuit and a part of the helium gas pipeline connected thereto are located in the active zone of the research reactor core; the 3 He gas in the gas absorption reactor absorbs thermal neutrons in the reactor to generate radioactive tritium ( 3 H). Tritium is an isotope of hydrogen, and tritium in a gaseous state has a strong penetration ability; tritium at a relatively high temperature can easily penetrate a container made of a metal material and then leak into the environment. The penetration ability of tritium increases sharply with the increase of its own temperature; and since the sheet fuel element 6 is a thin plate structure with a rectangular cross-section, the traditional helium screen structure greatly reduces the power change range of the fuel element, and due to the large power difference of the fuel elements at different positions in a single test, the traditional thermal balance method can only measure the total heat release power of multiple fuel elements, etc. The present invention provides a power transient irradiation device suitable for sheet elements, which adopts an axial multi-layer sheet fuel arrangement scheme, can carry multiple sheet fuel elements 6 at the same time, and each layer of fuel element can be matched with a helical tube helium screen 4 with different pipe inner diameters and winding pitches to achieve different power change amplitudes corresponding to the fuel elements at different positions, so as to greatly expand the power transient test ability and test parameter range of the device.

[0047] In a specific solution, it includes a square box 5, a helical tube helium screen 4, a helium inlet pipe 18 and a helium outlet pipe 17. The helical tube helium screen 4 is sequentially wound around the outside of the square box 5 in a helical direction. At this time, several helical tube helium screens 4, such as the first helical tube helium screen 401, the second helical tube helium screen 402 and the third helical tube helium screen 403, are connected to each other. The gas pipelines between the helical tube helium screens 4 at different positions can preferably be connected by welding. The lower end of the third helical tube helium screen 403 at the bottom is connected to the helium inlet pipe 18, and the upper end of the first helical tube helium screen 401 at the top is connected to the helium outlet pipe 17. In this way, helium gas ( 3Helium gas), helium-3 gas enters from the helium inlet pipe 18, flows through several spiral tube helium shields 4, and finally flows out through the helium outlet pipe 17; in addition, the inside of the square box 5 has an inner cavity, that is, an inner flow channel 8 for cooling water to pass through. Several sheet-shaped fuel elements 6 are evenly distributed at intervals along the axial direction of the inner flow channel 8, that is, N sheet-shaped fuel elements 6 are arranged vertically in a row. The array of sheet-shaped fuel elements 6 is in the shape of a thin cuboid and is fixed in shape and position by corresponding fixing structures. In this way, the cooling water entering the square box 5 will be divided into two parts by the sheet-shaped fuel elements 6. After being heated and raised in temperature by the fuel elements, it re-converges at the top of the array of sheet-shaped fuel elements 6 and then enters the inner flow channel 8 in the intermediate joint area; each layer of sheet-shaped fuel elements 6 corresponds to an independent spiral tube helium shield 4. In this way, a large power jump of the sheet-shaped fuel elements 6 can be achieved through the spiral tube helium shield 4; in addition, for the spiral tube helium shield 4 corresponding to each layer of sheet-shaped fuel elements 6, the diameter of the pipeline and the pitch of the spiral tube can be set independently, so that different power change amplitudes can be achieved for the sheet-shaped fuel elements 6 at different positions under the same helium-3 gas pressure change range. Among them, both ends of the fuel section of the sheet-shaped fuel element 6 are located between the two ends of the corresponding spiral tube helium shield 4, preferably the axial position and length of the spiral tube helium shield 4 are the same as those of the corresponding sheet-shaped fuel element 6.

[0048] The above solution aims to achieve: an axial multi-layer sheet-shaped fuel arrangement scheme is adopted, which can carry multiple sheet-shaped fuel elements 6 at the same time, improving the utilization rate of the irradiation space in the irradiation channel; while achieving a large power jump of the sheet-shaped fuel through the spiral tube helium shield 4, each layer of fuel elements can be paired with a spiral tube helium shield 4 with different pipe inner diameters and winding pitches to achieve different power change amplitudes for fuel elements at different positions, so as to greatly expand the power transient test ability and test parameter range of the device. In addition, the spiral tube helium shield 4 is located outside the inner flow channel 8 for cooling the sheet-shaped fuel element 6, reducing the influence of the heat release of helium-3 gas and its helium shield structural material on the measurement of the heat release power of the fuel, and improving the accuracy of the measurement of the heat release power of the sheet-shaped fuel element 6. The spiral tube helium shield 4 does not contact the relatively high-temperature cooling water for cooling the sheet-shaped fuel element 6, which to a certain extent reduces the temperature of the helium pipeline and the tritium-containing helium gas in the pipeline, thus helping to reduce the tritium permeation and leakage ability.

[0049] Embodiment 2:

[0050] This Embodiment 2 is further optimized on the basis of Embodiment 1, such as Figure 1 and Figure 2 shown, providing specific setting methods for other supporting components.

[0051] In this embodiment, as the pressure boundary to form a coolant channel, a pressure tube 3 is further included. Both the square box 5 and the helical tube helium shield 4 are located in the chamber of the pressure tube 3. The pressure tube 3 is provided with a cooling water inlet 12, and the cooling water inlet 12 is located above the helical tube helium shield 4. The lower end of the square box 5 is communicated with the bottom of the pressure tube 3, and the upper end of the square box 5 is communicated with a cooling water outlet 13. In this solution, the pressure tube 3 is a thick-walled cylindrical structure made of stainless steel material, which serves as the pressure boundary to accommodate the cooling water with typical pressurized water reactor environmental parameters. In this way, the cooling water can flow in from the upper cooling water inlet 12 and flow downward along the outer flow channel 7, thereby cooling the pressure tube 3 and the helical tube helium shield 4. Subsequently, it turns back upward at the bottom of the pressure tube 3 and the outer tube, and then passes through the inner flow channel 8. After flushing and cooling the plate-shaped fuel element 6, it flows out from the coolant outlet.

[0052] To completely separate the outer flow channel 7 and the inner flow channel 8, a shunt tube 9 is further included. One end of the shunt tube 9 is communicated with the upper end of the square box 5 through an intermediate joint, and the other end of the shunt tube 9 penetrates through the pressure tube 3.

[0053] To reduce heat transfer, a protection tube 1 is further included. The pressure tube 3 and the protection tube 1 are coaxial and arranged in sequence from inside to outside. The chamber between the inner side of the protection tube 1 and the outer side of the pressure tube 3 is a nitrogen chamber 2. In this solution, the protection tube 1 is located outside the pressure tube 3 and is also a cylindrical structure. There is a nitrogen chamber 2 between the two, filled with normal-pressure nitrogen, and connected to a nitrogen inlet 10 and a nitrogen outlet 11 respectively.

[0054] To reduce the heat exchange between the cooling water in different flow channels inside and outside the tube and provide a measurement lead channel, both the shunt tube 9 and the square box 5 adopt a first double-layer tube structure, and the gap in the first double-layer tube structure is filled with nitrogen.

[0055] To further prevent tritium from permeating and leaking into the cooling water in the helical tube helium shield 4 and the connected helium pipelines, the helical tube helium shield 4, the helium inlet pipe 18, and the helium outlet pipe 17 all adopt a second double-layer tube structure with a filling layer. The second double-layer tube structure includes an inner layer tube, a filling layer filled with sponge-like titanium metal tubes, and an outer layer tube in sequence from inside to outside. Both the inner layer tube and the outer layer tube are made of stainless steel material with a dense Al2O3 coating. In this solution, a helium pipeline with a double-layer stainless steel tube structure with a sandwich is adopted, and both layers of this double-layer tube are designed with Al2O3 coating. The inner layer tube accommodates tritium-containing helium, which can prevent tritium in the helium shield and the connected helium pipelines from permeating and leaking into the cooling water, thereby effectively reducing the radioactive hazard caused by tritium leakage.

[0056] To online monitor the thermal neutron fluence rate near different sheet-shaped fuel elements 6, so as to accurately measure the relative power distribution of sheet-shaped fuel elements 6 at different positions during the power transient test, a measuring head of a self-powered neutron detector 16 is installed at the central region of the wide side of each sheet-shaped fuel element 6. A plurality of measuring heads of the self-powered neutron detectors 16 are all located in the square box 5. In this solution, the self-powered neutron detector 16 is preferably arranged to be implanted in the hollow sandwich layer of the square box 5, and the number of detectors is the same as the number of sheet-shaped fuel elements 6. Each detector corresponds to one layer of sheet-shaped fuel elements 6, and its installation position is close to the central region of the wide side of the sheet-shaped fuel element 6. The self-powered neutron detectors 16 arranged in the device can online monitor the thermal neutron fluence rate near different sheet-shaped fuel elements 6; thus, accurately measure the relative power distribution of sheet-shaped fuel elements 6 at different positions during the power transient test.

[0057] To measure the temperature rise of the cooling water in the inner flow channel 8 in the fuel region, a plurality of fuel section inlet thermocouples 14 are arranged below the lowermost sheet-shaped fuel element 6; a plurality of fuel section outlet thermocouples 15 are arranged above the uppermost sheet-shaped fuel element 6. Among them, by measuring the temperature rise of the cooling water in the test fuel region of the inner flow channel 8 and using the cooling water flow rate measured by an external system connected to the device, the total heat release power of all sheet-shaped fuel elements 6 can be obtained.

[0058] Embodiment 3:

[0059] This Embodiment 3 further limits on the basis of Embodiment 2, and provides the specific working principle of the power transient irradiation device structure applicable to sheet-shaped elements and its power partition measurement method.

[0060] Specific working principle:

[0061] A power transient irradiation device structure applicable to sheet-shaped elements provided by the present invention is as Figure 1 and Figure 2 shown. The device is installed in the core region of the research reactor and is a part of the fuel power transient test system; the cooling water inlet and outlet, helium inlet and outlet pipes, and nitrogen inlet and outlet of the device are connected to the external equipment of the test system, and the external equipment provides cooling water and helium (high-purity 3Helium gas) and nitrogen source. From outside to inside, the main structural components of the device include a protection tube 1, a pressure tube 3, a shunt tube 9, and a square box 5, as well as gas cavities or fluid domains separated by the above structures. The nitrogen cavity 2 between the protection tube 1 and the pressure tube 3 mainly functions to keep warm and reduce the heat transfer from the pressure tube 3 to the protection tube 1; at the same time, by connecting to external equipment through the nitrogen inlet and outlet, the circulation and quality detection of nitrogen are realized, thereby realizing the on-line detection of the integrity of the pressure tube 3 (whether there is cooling water leakage). The cooling water in the device is driven by external equipment, enters from the cooling water inlet 12, flows into the outer flow channel 7, flows down to the bottom of the square box 5 and then turns back upward, flows into the inner flow channel 8 and is divided into two streams. After being heated by the cooling finned fuel element 6, it converges at the top of the fuel section, and then flows out of the device through the shunt tube 9 from the cooling water outlet 13. For helium-3 gas, it also flows in from the helium inlet pipe 18 driven by external equipment, flows through multiple helical tube helium shields 4 in sequence, enters the helium outlet pipe 17 through the connecting pipe, and finally flows out of the device.

[0062] Multiple (generally 2 to 5) sheet-shaped fuel elements 6 are arranged vertically in a row and cooled by the cooling water in the square box 5; by using the temperature rise of the cooling water in the inner flow channel 8 measured by the thermocouples arranged at the lower and upper parts of the fuel section and combining with the cooling water flow measured by the external system connected to the device, the total heat release power of all sheet-shaped fuel elements 6 can be obtained. By using the measurement data of the self-powered neutron detectors 16 on each layer, the relative power distribution of the sheet-shaped fuel elements 6 can be obtained, and finally the real-time measurement of the power of each layer of sheet-shaped fuel elements 6 can be realized.

[0063] Each layer of sheet-shaped fuel element 6 corresponds to an independent helium shield, and the axial position and length of the helium shield are the same as those of the corresponding fuel element. The helium shield is formed by winding a double-layer tube-structured helium gas pipeline around the square box 5 in a spiral shape. The diameter of the pipeline and the pitch of the spiral tube can be independently set for each layer of spiral tube helium shield 4, so that different power change amplitudes of the fuel elements can be realized at different axial positions.

[0064] Both the shunt tube 9 and the square box 5 adopt a hollow double-layer structure, and nitrogen is filled in the gap of the double-layer structure to reduce the heat exchange of the cooling water between the inner and outer flow channels 7 and provide a measurement lead channel. Self-powered neutron detectors 16 are implanted in the hollow interlayer of the square box 5, and each detector corresponds to one layer of sheet-shaped fuel element 6, and its installation position is in the central area near the wide side of the sheet-shaped fuel element 6.

[0065] Power partition measurement method:

[0066] At the lower and upper parts of the fuel section of the internal flow channel 8, multiple thermocouples are respectively arranged to measure the temperature rise of the cooling water in the internal flow channel 8 in the test fuel area; by using the cooling water flow rate measured by an external system connected to the device, the total heat release power of all the plate-shaped fuel elements 6 can be obtained. On the other hand, by using the relative power distribution of the plate-shaped fuel elements 6 measured online by the self-powered neutron detector 16 and combining it with the total heat release rate power measured from the cooling water flow rate and temperature rise, the power data of each plate-shaped fuel element 6 during the fuel power transient test process can be measured in real time.

[0067] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A power transient irradiation device applicable to sheet components, characterized in that, Comprising: A square box (5), both the upper and lower ends of the square box (5) are open, the inner cavity of the square box (5) is an internal flow channel (8) for cooling water to pass through, and a plurality of sheet-shaped fuel elements (6) are evenly distributed at intervals from bottom to top in the internal flow channel. The plurality of sheet-shaped fuel elements (6) are placed vertically and are located in the same vertical plane; A plurality of spiral tube helium shields (4), the plurality of spiral tube helium shields (4) correspond one by one to the plurality of sheet-shaped fuel elements (6), and the spiral tube helium shields (4) are wound around the outside of the square box (5), and adjacent spiral tube helium shields (4) are communicated with each other; the lower end of the lowermost spiral tube helium shield (4) is communicated with a helium inlet pipe (18), and the upper end of the uppermost spiral tube helium shield (4) is communicated with a helium outlet pipe (17); Both ends of the fuel section of the sheet-shaped fuel element (6) are located between both ends of the corresponding spiral tube helium shield (4).

2. The power transient irradiation device applicable to sheet components according to claim 1, characterized in that, It further includes a pressure tube (3), the square box (5) and the spiral tube helium shield (4) are both located in the chamber of the pressure tube (3), the pressure tube (3) is provided with a cooling water inlet (12), and the cooling water inlet (12) is located above the spiral tube helium shield (4); the lower end of the square box (5) is communicated with the bottom of the pressure tube (3), and the upper end of the square box (5) is communicated with a cooling water outlet (13).

3. The power transient irradiation device applicable to sheet elements according to claim 2, wherein It further includes a shunt tube (9), one end of the shunt tube (9) is communicated with the upper end of the square box (5) through an intermediate joint, and the other end of the shunt tube (9) penetrates out of the pressure tube (3).

4. The power transient irradiation device applicable to sheet-like elements according to claim 3, characterized in that, It further includes a protection tube (1), the pressure tube (3) and the protection tube (1) are coaxial and are arranged in sequence from inside to outside, and the chamber between the inner side of the protection tube (1) and the outer side of the pressure tube (3) is a nitrogen chamber (2).

5. The power transient irradiation device applicable to sheet elements according to claim 4, characterized in that, Both the shunt tube (9) and the square box (5) adopt a first double-layer tube structure, and nitrogen is filled in the gap in the first double-layer tube structure.

6. The power transient irradiation device applicable to sheet components according to claim 1, characterized in that, The spiral tube helium shield (4), the helium inlet pipe (18) and the helium outlet pipe (17) all adopt a second double-layer tube structure with a filling layer. The second double-layer tube structure includes an inner layer tube, a filling layer filled with sponge-like titanium metal tubes and an outer layer tube in sequence from inside to outside.

7. The power transient irradiation device applicable to sheet-like elements according to claim 6, characterized in that, Both the inner layer tube and the outer layer tube are made of stainless steel material with a dense Al2O3 coating.

8. The power transient irradiation device applicable to sheet elements according to claim 1, characterized in that, The measuring head of a self-powered neutron detector (16) is installed at the central area of the wide side of each sheet-shaped fuel element (6), and the measuring heads of the plurality of self-powered neutron detectors (16) are all located in the square box (5).

9. The power transient irradiation device applicable to sheet-like elements according to claim 1, characterized in that, A plurality of fuel section inlet thermocouples (14) are arranged below the lowermost sheet-shaped fuel element (6); a plurality of fuel section outlet thermocouples (15) are arranged above the uppermost sheet-shaped fuel element (6).

10. The power partition measurement method for a power transient irradiation device applicable to sheet components according to any one of claims 1-9, characterized in that, Including the following steps: Measure the temperature of the cooling water at the lower end inlet and the upper end outlet of the internal flow channel (8) respectively, obtain the temperature rise of the cooling water in the test fuel area, and measure the cooling water flow through an external system, so as to obtain the total heat release power of all the sheet-shaped fuel elements (6); Online measure the relative power distribution of each sheet-shaped fuel element (6); By the relative power distribution of each of the sheet-like fuel elements (6) and in combination with the total heat release power, the power data of each sheet-like fuel element (6) during the fuel power transient test can be measured in real time.

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