Lead-based fast reactor exhaust and fissile gas collection

Abstract

This invention relates to the field of nuclear reactors, specifically to a lead-based fast neutron reactor exhaust device and a fission gas collection device. The exhaust device includes fuel rods and a one-way exhaust device. The fuel rods include nuclear fuel pellets and cladding tubes. The one-way exhaust device connects the gas chamber to the outside of the cladding tubes in one direction. A metal coolant is provided inside the pressure vessel to submerge the fuel rods and the one-way exhaust device. In use, the fission gas generated by the nuclear fuel pellets passes through the one-way exhaust device and enters the metal coolant in one direction. The fission gas collection device includes a lead-based fast neutron reactor exhaust device, a temporary storage tank, a multi-stage purification device, and a circulation pump. This invention achieves the purpose of one-way exhaust by connecting a one-way exhaust device to the cladding tube of the fuel rods, so that the fission gas inside the fuel rods is discharged into the primary coolant when the pressure exceeds a certain level. The fission gas collection device collects gaseous fission products in the upper chamber of the reactor pressure vessel.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactors, specifically to a lead-based fast neutron reactor exhaust device and fission gas collection device. Background Technology

[0002] Lead-based fast neutron reactors (LFRs) are fast neutron reactors that use lead / lead-bismuth as coolants. They are characterized by high safety, chemical inertness of the coolant, simple system equipment, and low maintenance costs. They are one of the candidate reactor types for the fourth generation of nuclear energy systems for the development of inland nuclear power, offshore energy extraction, and small-scale local power and heat supply.

[0003] Nuclear fuel rods are a key component of lead-based fast neutron reactors, serving as the reactor's energy source. The fissile material contained within the lead fuel rods continuously generates heat through fission reactions, which is transferred to the coolant, while also producing a large amount of fissile gas. Current nuclear fuel rod designs incorporate gas chambers of a certain length to contain the generated fissile gas; however, as burnup increases, the internal pressure of the fuel rods gradually rises, leading to a corresponding increase in outward stress on the cladding. To prevent excessive internal pressure from causing cladding damage, a specific refueling cycle is required to remove the nuclear fuel rods.

[0004] Therefore, the accumulation of fissile gas inside the gas chamber is the main factor limiting the refueling cycle of lead-based reactors. The proposed improvement method is to design the fuel assembly as a semi-enclosed container. When the fissile gas pressure in the storage chamber reaches a threshold, the control system opens the exhaust valve to discharge the fissile gas until the pressure is below the threshold. Then, the discharged fissile gas is sent through the primary loop to the gas storage device for centralized processing.

[0005] However, the above method has the disadvantages of high internal flow resistance in nuclear fuel assemblies and potential control failure of the exhaust device, which may lead to continuous release of radioactive gases during the reactor shutdown and refueling operation, endangering the safety of operators and increasing radiation protection risks. Summary of the Invention

[0006] The technical problem to be solved by this invention is to improve the economics and nuclear fuel utilization of lead-cooled fast reactors and avoid the leakage of radioactive gases. The purpose is to provide a lead-based fast neutron reactor exhaust device and fission gas collection device, and ultimately achieve a higher breed ratio and a longer reactor utilization rate by extending the reactor refueling cycle.

[0007] This invention is achieved through the following technical solution:

[0008] A lead-based fast neutron reactor exhaust device, comprising:

[0009] A fuel rod includes a nuclear fuel pellet column and a cladding tube, wherein the nuclear fuel pellet column is disposed at the lower part of the cladding tube, and a gas cavity is formed between the nuclear fuel pellet column and the upper end of the cladding tube;

[0010] A one-way exhaust device is fixedly installed inside the air chamber and connects the air chamber to the outside of the casing tube in one direction.

[0011] The fuel rods are placed inside the pressure vessel of the reactor, and the pressure vessel is filled with a metal coolant that submerges the fuel rods and the one-way exhaust device.

[0012] In use, the fission gas generated by the nuclear fuel pellet column passes through the one-way exhaust device and enters the metal coolant in one direction.

[0013] Specifically, the one-way exhaust device includes: a cylinder, an upper plug, a cylinder plug, and an exhaust pipe. The upper plug seals the upper end of the casing tube. The cylinder is fixedly installed inside the casing tube, and a gap is provided between the upper opening of the cylinder and the upper plug. The cylinder plug is installed inside the cylinder and seals the gap.

[0014] Both the upper plug and the cylinder plug are provided with through holes that connect the inside of the cylinder to the outside of the casing tube. The lower end of the exhaust pipe passes through the through hole and is located in the lower part of the cylinder. The upper end of the exhaust pipe is located in the metal coolant. The outer side of the exhaust pipe is sealed and fitted to the inner side of the through hole.

[0015] The cylinder plug has a porous structure, and the fission gas can pass through the pores of the cylinder plug, while the metal coolant cannot pass through the pores of the cylinder plug.

[0016] Optionally, the cylinder is a barrel-shaped structure with an open top, and the casing tube is a barrel-shaped structure with an open top.

[0017] Optionally, the lower end of the exhaust pipe is located below the gap, and the lower end face of the exhaust pipe does not contact the bottom surface of the cylinder.

[0018] Optionally, the outer diameter of the cylinder is smaller than the inner diameter of the casing tube, and the outer side of the cylinder is fixedly connected to the inner side of the casing tube by a plurality of gaskets.

[0019] Optionally, a retaining ring is provided on the upper inner side of the cylinder, the lower side of the cylinder plug is attached to the upper side of the retaining ring, the upper side of the cylinder plug is attached to the lower side of the upper plug, and the circumferential side of the cylinder plug is attached to the inner side of the cylinder.

[0020] A fission gas collection device for a lead-based fast neutron reactor includes:

[0021] Exhaust system for lead-based fast neutron reactors;

[0022] A temporary storage tank, the air inlet of which is connected to the upper chamber of the pressure vessel via a valve;

[0023] A multi-stage purification device, the air inlet of which is connected to the air outlet of the temporary storage tank;

[0024] The circulation pump has its air inlet connected to the outlet of the multi-stage purification device, and its air outlet connected to the upper chamber.

[0025] Optionally, the multi-stage purification device includes multiple sleeves connected in series and a filter unit disposed within the sleeves, the filter unit being used to separate and capture condensed phase fission products in gaseous fission products.

[0026] Furthermore, the fission gas collection device also includes a sensor and a transmitter. The detection end of the sensor is located in the upper chamber, and the signal output end of the sensor is connected to the transmitter and transmits the detection signal through the transmitter.

[0027] Optionally, the temporary storage tank has a hollow structure and an internal storage space for receiving gaseous fission products.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] This invention connects a one-way venting device to the cladding tube of the fuel rod, allowing the fission gas inside the fuel rod to be discharged into the primary coolant when the pressure exceeds a certain level. The special structure of the one-way venting device achieves liquid sealing of the cladding tube at high temperatures and solid sealing at low temperatures, ensuring that the fission gas inside the fuel rod can be discharged under the pressure difference, ultimately achieving the purpose of one-way venting. Because the internal pressure of the fuel rod is controlled at a low level, the length of the gas chamber section can be significantly reduced compared to existing fuel rod designs, thereby reducing the height of the fuel assembly and flow resistance.

[0030] Finally, the fission gas collection device collects gaseous fission products in the upper chamber of the reactor pressure vessel, and the gaseous fission products are controlled for emission, temporary storage, and treatment through valves, temporary storage tanks, and multi-stage purification devices. Sensors, transmitters, and other components monitor and identify the parameters and status of the volume, valves, and gaseous fission products, providing useful information and signals to support the operation and control of the reactor. Attached Figure Description

[0031] The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, but do not constitute a limitation on the embodiments of the present invention.

[0032] Figure 1 This is a schematic diagram of the structure of a fission gas collection device for a lead-based fast neutron reactor according to the present invention.

[0033] Figure 2 This is a schematic diagram of the structure of the fuel rod according to the present invention.

[0034] Figure 3 This is a schematic diagram of the structure of the one-way exhaust device according to the present invention.

[0035] Figure 4 This is a cross-sectional view (AA) of the one-way exhaust device according to the present invention.

[0036] Figure 5 This is a schematic diagram of the installation of the retaining ring according to the present invention.

[0037] Reference numerals: 1-Fuel rod; 2-Valve; 3-Upper chamber; 4-Temporary storage tank; 5-Multi-stage purification device; 6-Circulation pump; 7-Pipeline; 8-Sensor; 9-Emitter; 10-Fuel cladding tube; 11-Nuclear fuel pellet column; 12-Gas chamber; 13-One-way exhaust device; 14-Valve body; 15-Valve core; 16-Storage space; 17-Exhaust port of temporary storage tank; 18-Filter unit; 19-Exhaust port of multi-stage purification device; 20-Upper plug; 21-Exhaust pipe; 22-Cylinder; 23-Gasket; 24-Retaining ring; 25-Cylinder plug. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0039] It should also be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0040] Where there is no conflict, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] Example 1

[0042] like Figure 1As shown, a fission gas collection device for a lead-based fast neutron reactor is provided, comprising: a lead-based fast neutron reactor exhaust device, a temporary storage tank 4, a multi-stage purification device 5, and a circulation pump 6.

[0043] The air inlet of the temporary storage tank 4 is connected to the upper chamber 3 of the pressure vessel through valve 2; the temporary storage tank 4 has a hollow structure and is provided with a storage space 16 for receiving gaseous fission products.

[0044] The air inlet of the multi-stage purification device 5 is connected to the air outlet 17 of the temporary storage tank.

[0045] The air inlet of the circulation pump 6 is connected to the air outlet 19 of the multi-stage purification device 5, and the air outlet of the circulation pump 6 is connected to the upper chamber 3.

[0046] The multi-stage purification device 5 includes multiple sleeves connected in series and a filter unit 18 disposed within the sleeves. The filter unit 18 is used to separate and capture the condensate phase fission products in the gaseous fission products.

[0047] Gaseous fission products are collected in the upper chamber 3 of the reactor pressure vessel, and the gaseous fission products are controlled, temporarily stored and purified through components such as valve 2, temporary storage tank 4, and multi-stage purification device 5. The condensed phase fission products are separated and captured, reducing waste volume and improving waste management.

[0048] Valve 2 is the control part of the fission gas collection device, which enables the controlled emission and temporary storage of gaseous fission products. Valve 2 includes a valve body 14 and a valve core 15. When the valve core 15 is in the closed position, the upper chamber 3 is isolated from the temporary storage tank 4. When the valve core 15 is in the open position, the upper chamber 3 is connected to the temporary storage tank 4, and the gaseous fission products are transported to the temporary storage tank 4.

[0049] The temporary storage tank 4 is the collection section, enabling the collection and transport of gaseous fission products. The temporary storage tank 4 is a hollow cylindrical structure, with one end connected to valve 2 and the other end connected to the multi-stage purification device 5. The temporary storage tank 4 has an internal storage space 16 for receiving the gaseous fission products emitted from valve 2. The temporary storage tank 4 also has a gas outlet 17, used to periodically transport the gaseous fission products to the multi-stage purification device 5.

[0050] The multi-stage purification device 5 is the purification section, capable of purifying and treating gaseous fission products. The multi-stage purification device 5 is a detachable cylindrical structure, connected at one end to the temporary storage tank 4 and at the other end to the external processing system. Internally, the multi-stage purification device 5 contains several filter units 18 for separating and capturing condensed-phase fission products, such as iodine, carbon, and tin, from the gaseous fission products. Different filter materials, such as activated carbon, zeolite, and metal mesh, can be selected for the filter units 18 based on the characteristics of different condensed-phase fission products. The multi-stage purification device 5 also has an outlet 19 for transporting inert gas fission products from the gaseous fission products to the external processing system.

[0051] In addition, the fission gas collection device also includes a sensor 8 and a transmitter 9. The detection end of the sensor 8 is located in the upper chamber 3, and the signal output end of the sensor 8 is connected to the transmitter 9 and transmits the detection signal through the transmitter 9.

[0052] The system uses components such as sensor 8 and transmitter 9 to monitor and identify the parameters and states of the upper chamber 3 of the reactor pressure vessel, valve 2, and gaseous fission products, providing useful information and signals to support the operation and control of the reactor.

[0053] Sensor 8 is the monitoring component, enabling the monitoring of parameters and states of the reactor upper chamber 3, valve 2, and gaseous fission products. Sensor 8 is a small electronic device installed on the upper chamber 3 of the pressure vessel and connected to the transmitter 9. Sensor 8 can detect and record parameters such as pressure and temperature within the reactor upper chamber 3, as well as the type, quantity, and radioactivity of the gaseous fission products. Based on these parameters and states, it can determine whether valve 2 needs to be opened or closed, and whether the gaseous fission products need to be transported or processed.

[0054] Transmitter 9 is the identification unit, enabling the identification and transmission of information and signals from the upper chamber 3, valve 2, and gaseous fission products. Transmitter 9 is a small wireless device connected to sensor 8. It receives and decodes the information and signals sent by sensor 8 and transmits them to the reactor's operation and control system. Based on this information and signals, transmitter 9 can provide useful prompts and warnings, such as whether valve 2 is functioning properly or whether gaseous fission products exceed safety limits.

[0055] Example 2

[0056] like Figure 2 , 3 As shown in Figure 4, this embodiment provides a lead-based fast neutron reactor exhaust device, including: fuel rods 1 and a one-way exhaust device 13.

[0057] The fuel rod 1 includes a nuclear fuel pellet column 11 and a cladding tube. The nuclear fuel pellet column 11 is disposed at the lower part of the cladding tube, and a gas chamber 12 is formed between the nuclear fuel pellet column 11 and the upper end of the cladding tube. A one-way exhaust device 13 is fixedly disposed in the gas chamber 12 and connects the gas chamber 12 to the outside of the cladding tube in one direction.

[0058] The fuel rod 1 is placed inside the pressure vessel of the reactor, and the pressure vessel is filled with a metal coolant that submerges the fuel rod 1 and the one-way exhaust device 13.

[0059] In use, the fission gas generated by the nuclear fuel pellet column 11 passes through the one-way exhaust device 13 and enters the metal coolant in one direction.

[0060] By installing a one-way exhaust device 13 on the cladding tube, the generated fission gas can be discharged from the fuel rod 1, and external metal coolant is prevented from entering the fuel rod 1 and affecting the nuclear fuel pellet column 11.

[0061] Therefore, as Figure 3 The diagram illustrates the specific structure of a one-way exhaust device 13. The one-way exhaust device 13 includes: a cylinder 22, an upper plug 20, a cylinder plug 25, and an exhaust pipe 21. The upper plug 20 seals the upper end of the casing tube. The cylinder 22 is fixedly disposed within the casing tube, and a gap is provided between the upper opening of the cylinder 22 and the upper plug 20. The cylinder plug 25 is disposed within the cylinder 22 and seals the gap.

[0062] Both the upper plug 20 and the cylinder plug 25 are provided with through holes that connect the inside of the cylinder 22 with the outside of the casing tube. The lower end of the exhaust pipe 21 passes through the through hole and is located at the lower part of the cylinder 22. The upper end of the exhaust pipe 21 is located inside the metal coolant. The outer side of the exhaust pipe 21 is sealed and fitted to the inner side of the through hole.

[0063] The cylinder plug 25 has a porous structure, and the fission gas can pass through the pores of the cylinder plug 25, while the metal coolant cannot pass through the pores of the cylinder plug 25.

[0064] The cylinder 22 is fixed inside the casing tube by means of partial welding, pins, and tenons. A gas flow channel is left between the cylinder 22 and the casing tube. In practice, the gap between the upper end of the cylinder 22 and the upper plug 20 is a certain distance to allow gas to pass through.

[0065] The fission gas flows upward through the gas flow channel. After passing through the cylinder plug 25 through the gap, the fission gas enters the upper part of the cylinder 22, then flows downward along the cylinder 22, enters the exhaust pipe 21 from the bottom, and finally flows upward along the exhaust pipe 21 and is discharged from the fuel rod 1.

[0066] When no large amount of fission gas is generated, the metal coolant outside the fuel rod 1 enters the exhaust pipe 21 from the upper end of the exhaust pipe 21 and flows downward along the exhaust pipe 21, eventually filling the entire cylinder 22.

[0067] Because the metal coolant cannot pass through the orifice of the cylinder plug 25, the cylinder plug 25 can impede the passage of the metal coolant while ensuring gas flow, thus preventing the metal coolant from contacting the fuel.

[0068] The porous structure of cylinder plug 25 utilizes the fact that the surface tension of the metal coolant is greater than that of the fission gas, allowing the fission gas to pass through while the metal coolant cannot.

[0069] In addition, since the metal coolant is solid at low temperatures, during the production stage of fuel rod 1, the metal coolant is added into cylinder 22 and solidified to ensure that air and water vapor do not enter the fuel rod before it is fed into the reactor, thus avoiding additional oxidation / corrosion caused by air and water vapor entering the primary circuit after the reactor is started.

[0070] At high temperatures, the metal coolant melts, and the fission gas inside the fuel rod 1 can be discharged under the pressure difference between the inside and outside. That is, when the gas pressure inside the casing tube is high, the fission gas will push the metal coolant in the cylinder 22 to be discharged from the exhaust pipe 21, and finally the fission gas can be discharged.

[0071] Furthermore, because the metal coolant solidifies at low temperatures, it ensures that radioactive materials will not leak when the material is removed from the reactor.

[0072] Example 3

[0073] In order for Embodiment 2 to be implemented normally, as a preferred embodiment, the cylinder 22 is a barrel-shaped structure with an open top, and the casing tube is a barrel-shaped structure with an open top. The barrel-shaped structure makes it easy for the upper plug 20 and the cylinder plug 25 to seal it.

[0074] The lower end of the exhaust pipe 21 is located below the gap, and the lower end face of the exhaust pipe 21 does not contact the bottom surface of the cylinder 22, forming a U-shaped structure, which can effectively discharge the metal coolant in the cylinder 22.

[0075] The outer diameter of the cylinder 22 is smaller than the inner diameter of the casing tube 10. The outer side of the cylinder 22 is fixedly connected to the inner side of the casing tube through multiple gaskets 23, thus reserving a gas flow channel for the fission gas.

[0076] In addition, to enable axial positioning of the cylinder plug 25, a retaining ring 24 is provided on the upper inner side of the cylinder 22. The lower side of the cylinder plug 25 is attached to the upper side of the retaining ring 24, the upper side of the cylinder plug 25 is attached to the lower side of the upper end plug 20, and the circumferential side of the cylinder plug 25 is attached to the inner side of the cylinder 22. Simultaneously, because the lower side of the cylinder plug 25 is attached to the retaining ring 24, even if there is a gap between the circumferential side of the cylinder plug 25 and the inner side of the cylinder 22, it is possible to prevent the metal coolant from flowing into the casing tube.

[0077] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0078] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0079] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above invention, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A lead-based fast neutron reactor exhaust device, characterized in that, include: The fuel rod (1) includes a nuclear fuel pellet column (11) and a cladding tube (10), wherein the nuclear fuel pellet column (11) is disposed at the lower part of the cladding tube, and a gas cavity (12) is formed between the nuclear fuel pellet column (11) and the upper end of the cladding tube. A one-way exhaust device (13) is fixedly installed in the air chamber (12) and connects the air chamber (12) to the outside of the casing tube in one direction; The fuel rod (1) is placed inside the pressure vessel of the reactor, and the pressure vessel is provided with a metal coolant that submerges the fuel rod (1) and the one-way exhaust device (13); When in use, the fission gas generated by the nuclear fuel pellet column (11) passes through the one-way exhaust device (13) and enters the metal coolant in one direction; The one-way exhaust device (13) includes: a cylinder (22), an upper plug (20), a cylinder plug (25), and an exhaust pipe (21). The upper plug (20) blocks the upper end of the casing tube. The cylinder (22) is fixedly installed inside the casing tube, and a gap is provided between the upper opening of the cylinder (22) and the upper plug (20). The cylinder plug (25) is installed inside the cylinder (22) and blocks the gap. Both the upper plug (20) and the cylinder plug (25) are provided with through holes that connect the inside of the cylinder (22) and the outside of the casing tube. The lower end of the exhaust pipe (21) passes through the through hole and is located at the lower part of the cylinder (22). The upper end of the exhaust pipe (21) is located inside the metal coolant. The outer side of the exhaust pipe (21) is sealed and fitted with the inner side of the through hole. The cylinder plug (25) has a porous structure, and the fission gas can pass through the pores of the cylinder plug (25), while the metal coolant cannot pass through the pores of the cylinder plug (25).

2. The lead-based fast neutron reactor exhaust device according to claim 1, characterized in that, The cylinder (22) is a barrel-shaped structure with an open top, and the casing tube is a barrel-shaped structure with an open top.

3. The lead-based fast neutron reactor exhaust device according to claim 1, characterized in that, The lower end of the exhaust pipe (21) is located below the gap, and the lower end face of the exhaust pipe (21) does not contact the bottom surface of the cylinder (22).

4. The lead-based fast neutron reactor exhaust device according to claim 1, characterized in that, The outer diameter of the cylinder (22) is smaller than the inner diameter of the casing tube, and the outer side of the cylinder (22) is fixedly connected to the inner side of the casing tube by a plurality of gaskets (23).

5. The lead-based fast neutron reactor exhaust device according to claim 1, characterized in that, A retaining ring (24) is provided on the upper inner side of the cylinder (22). The lower side of the cylinder plug (25) is attached to the upper side of the retaining ring (24). The upper side of the cylinder plug (25) is attached to the lower side of the upper end plug (20). The circumferential side of the cylinder plug (25) is attached to the inner side of the cylinder (22).

6. A fission gas collection device for a lead-based fast neutron reactor, characterized in that, include: A lead-based fast neutron reactor exhaust device as described in any one of claims 1-3; The temporary storage tank (4) has its air inlet connected to the upper chamber (3) of the pressure vessel via a valve (2); The multi-stage purification device (5) has its air inlet connected to the air outlet (17) of the temporary storage tank; The circulation pump (6) has its air inlet connected to the outlet of the multi-stage purification device (5), and its air outlet is connected to the upper chamber (3).

7. The fission gas collection device for a lead-based fast neutron reactor according to claim 6, characterized in that, The multi-stage purification device (5) includes multiple sleeves connected in series and a filter unit (18) disposed in the sleeves. The filter unit (18) is used to separate and capture the condensed phase fission products in the gaseous fission products.

8. The fission gas collection device for a lead-based fast neutron reactor according to claim 6, characterized in that, It also includes a sensor (8) and a transmitter (9). The detection end of the sensor (8) is located in the upper chamber (3), and the signal output end of the sensor (8) is connected to the transmitter (9) and transmits the detection signal through the transmitter (9).

9. A fission gas collection device for a lead-based fast neutron reactor according to claim 6, characterized in that, The temporary storage tank (4) has a hollow structure and is equipped with a storage space (16) for receiving gaseous fission products.

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