Radioisotope production facility

Abstract

The present invention discloses a radioactive isotope production device. The radioactive isotope production device comprises: a containing tube with an open end for filling fuel salt; a first air inlet pipe and a second air inlet pipe are arranged in the containing tube; the top of the first air inlet pipe and the top of the second air inlet pipe are both located above the liquid level of the fuel salt; the bottom of the first air inlet pipe is located below the liquid level; a gas distributor is arranged at the bottom of the second air inlet pipe; the gas outlet of the gas distributor is located below the liquid level and faces the liquid level; the bottom of the first air inlet pipe is lower than the gas outlet of the gas distributor. The radioactive isotope device has the advantages of simple structure, high reliability, low cost, and replaceability. The production of radioactive isotopes using the device has the advantages of simple process, high fuel utilization, high production efficiency, low pollution, process safety, and online extraction.

Description

Technical Field

[0001] The invention relates to a radioactive isotope production device. Background Art

[0002] Radioactive isotopes are widely used in medicine, industry, agriculture, scientific research, resource management and environmental protection.

[0003] The production of radioactive isotopes mainly includes accelerator target activation method, reactor target activation method, reactor target fission method and spent fuel extraction. The target activation method is used to produce neutron-deficient isotopes, and has disadvantages such as low yield, low specific activity and high cost. The reactor target fission method is the main way to produce isotopes. Through high-flux irradiation fission uranium fuel, a variety of radioactive isotopes can be produced in large quantities. It has the advantages of large yield, high specific activity and small generator size, but it also has disadvantages such as low uranium utilization, high waste, nuclear proliferation risk and high cost.

[0004] Compared with solid fission targets, liquid fuel salts have great advantages in isotope extraction. It does not require target preparation, shearing, or dissolution treatment. More importantly, the relevant isotopes and their precursor nuclei exist in the form of gas, volatilization, and aerosols, such as Xe-133, I-131, Sr-89, Y-90, Mo-99, etc. Since it is insoluble in fuel salts, it can be blown into the gas system by bubbling, spraying, etc., and then separated from most highly radioactive materials, which greatly simplifies the process and difficulty of isotope extraction, and there is basically no waste and pollution of uranium fuel. Therefore, the production of radioactive isotopes using molten salt reactors will have extremely high yields and convenience.

[0005] Half a century ago, Oak Ridge in the United States successfully operated two molten salt reactors, and a large number of radioactive isotopes, such as Mo-99 and Te-132, were detected in the exhaust system of the Molten Salt Experimental Reactor (MSRE). At the beginning of this century, with the rise of the molten salt reactor research and development boom, research on the production of radioactive isotopes using molten salt reactors has also increased. Given the advanced nature and technical challenges of molten salt reactors, there is still a large threshold for building a molten salt reactor compared to other radioactive isotope production methods. Isotope production in molten salt reactors also faces some challenges of its own: (1) The fuel salt loop of a molten salt reactor has a complex heat exchanger structure and core components. Radioactive isotope particles are easily deposited on the surface of these metals and graphite, resulting in fewer available radioactive isotopes. (2) The more bubbles entrained in the fuel salt loop, the higher the proportion of radioactive isotope particles entering the exhaust system. However, a high bubble content will affect the operating safety of the molten salt reactor, thus limiting the proportion of radioactive isotope particles entering the exhaust system. (3) The bubbling separation system of the molten salt reactor is usually installed in the pump. Its efficiency is related to the operating status of the pump, which puts forward new requirements for the design of the pump. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of the prior art in producing radioactive isotopes, such as complex process, low production efficiency, low fuel utilization, more waste, nuclear proliferation risk, and high cost, and provide a radioactive isotope production device. The radioactive isotope device of the present invention has the advantages of simple structure, high reliability, low cost, and replaceability. The production of radioactive isotopes using the device has the advantages of simple process, high fuel utilization, high production efficiency, low pollution, safe process, and online extraction.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a radioactive isotope production device, which comprises: a containing tube with an open end, used for filling fuel salt; a first air inlet pipe and a second air inlet pipe are arranged in the containing tube;

[0009] The top end of the first air inlet pipe and the top end of the second air inlet pipe are both located above the liquid level of the fuel salt; the bottom end of the first air inlet pipe is located below the liquid level; a gas distributor is provided at the bottom end of the second air inlet pipe; the gas outlet of the gas distributor is located below the liquid level and faces the liquid level; the bottom end of the first air inlet pipe is lower than the gas outlet of the gas distributor.

[0010] When the radioactive isotope production device of the present invention is in use, the fuel salt undergoes fission reaction after being irradiated by reactor neutrons to generate isotopes, which are attached to the bubbles blown out of the first air inlet pipe and brought to the liquid surface of the fuel salt. They are then brought out of the liquid surface under the impact of the gas blown out of the gas distributor and collected.

[0011] In the present invention, the gas distributor may be a conventional device in the art for evenly distributing gas, preferably a nozzle.

[0012] Preferably, a plurality of air outlet holes are evenly arranged on the nozzle.

[0013] Preferably, the surface of the nozzle is ellipsoidal, which can make the sprayed gas distribute over a wider surface, thereby improving the purging efficiency.

[0014] In the present invention, preferably, a cover plate is provided at the open end of the containing tube, an air outlet pipe is provided on the cover plate, and the bottom end of the air outlet pipe is higher than the liquid level; the air outlet pipe, the first air inlet pipe and the second air inlet pipe all pass through the cover plate.

[0015] The setting of the cover plate can fix the first air inlet pipe and the second air inlet pipe on the one hand, and can also prevent nuclear proliferation on the other hand. The air outlet pipe is set on the cover plate, which can collect the generated radioactive isotopes more safely and conveniently.

[0016] In the present invention, the fuel salt may be conventional in the art, generally including nuclear fuel and base salt. Wherein, the nuclear fuel is preferably low-enriched uranium. The base salt may be a conventional compound with a low melting point and a high boiling point in the art, preferably a fluoride and / or chloride of metal M, wherein the metal M is one or more of the following elements: Li, Be, Na, K, Rb and Zr; more preferably a mixture of NaF and ZrF4.

[0017] In the present invention, preferably, the bottom end of the first air inlet pipe is arranged close to the bottom of the accommodating tube.

[0018] The outlet port of the first air inlet pipe is close to the bottom of the containing pipe, so that all the radioactive isotopes generated in the containing pipe can be attached to the bubbles blown out of the first air inlet pipe and brought to the liquid surface of the fuel salt.

[0019] In the present invention, preferably, the gas outlet of the gas distributor is arranged close to the liquid surface.

[0020] The gas outlet of the gas distributor is arranged close to the liquid surface of the fuel salt. The gas blown out from the gas outlet has a stronger impact force at the liquid surface, and can blow more isotope particles out of the liquid surface.

[0021] In the present invention, the first air inlet pipe, the second air inlet pipe and the air outlet pipe may all be provided with valves according to conventional operation, and any of the valves may be switched between an open state and a closed state.

[0022] The valve can adjust the opening of the first air inlet pipe, the second air inlet pipe and the air outlet pipe. The valve is opened when air inlet or air outlet is needed, and closed when not in use. This allows all generated radioactive isotopes to be discharged and collected through the air outlet pipe, thereby improving collection efficiency and reducing the risk of nuclear proliferation.

[0023] In the present invention, preferably, a heat-insulating layer is further provided on the outer periphery of the housing tube.

[0024] The material of the thermal insulation layer may be conventional in the art, preferably silicon fiber material.

[0025] The heat-insulating layer can play a heat-insulating role during the preheating process before the containing tube is filled with salt, so that the temperature inside the containing tube remains constant during the salt filling process.

[0026] In the present invention, preferably, the housing tube is a double-layer casing.

[0027] The double-layer casing design ensures that when the inner tube leaks, the outer tube still has the capacity to contain the fuel salt, thus avoiding the release of radioactive substances.

[0028] Preferably, a heating device is arranged in the tube gap of the double-layer casing, and preferably, the heating device is an electric heating wire.

[0029] A heating device is provided in the tube gap of the double-layer casing, and the device can be heated before the fuel salt is loaded. During the process of producing radioactive isotopes by the device, if the heat is transferred too quickly, the heating device can also be turned on to heat the fuel salt in the device, so that the fuel salt in the double-layer casing remains in a liquid state, that is, the temperature is 500-800°C, and the generated radioactive isotopes can be carried to the liquid surface of the fuel salt by the bubbles.

[0030] Preferably, a fuel salt monitoring device is provided in the tube gap of the double-layer casing.

[0031] The provision of the fuel salt monitoring device can enable the leakage of fuel salt into the tube gap to be quickly monitored, thereby improving the safety of the radioactive isotope production device.

[0032] In the present invention, the material of the containing tube may be a conventional alloy in the art that is resistant to high temperature corrosion of the fuel salt, preferably a nickel-based alloy.

[0033] In the present invention, when the housing tube is a double-layer casing, the inner layer of the double-layer casing can be a nickel-based alloy, and the outer layer of the double-layer casing can be a zirconium alloy. The double-layer casing is installed in the reactor, and the reactor's cooling medium cools the double-layer casing to keep the temperature of the fuel salt within a suitable range. The zirconium alloy is more resistant to corrosion by the cooling medium.

[0034] In the present invention, preferably, the bottom end of the accommodating tube is arc-shaped.

[0035] The radioisotope production device of the present invention, a preferred embodiment of the assembly and use instructions:

[0036] S1: The pre-loading process includes the following steps:

[0037] (1) The radioisotope production device is assembled in a factory, the electric heating wire in the double-layer casing is turned on, and the thermal insulation layer is wrapped around the outer circumference of the double-layer casing to keep the temperature of the double-layer casing constant during the salt filling process.

[0038] (2) Open the valve of the first air inlet pipe and the valve of the air outlet pipe, pass protective gas (N2 or inert gas), and purge oxygen impurities in the device.

[0039] (3) A base salt (such as a mixture of NaF and ZrF4) is pressed into the first air inlet pipe by air pressure, and the protective gas is discharged from the air outlet pipe. After the base salt is filled, it is allowed to stand for a period of time, and then the protective gas is passed through the air outlet pipe to discharge the base salt from the first air inlet pipe.

[0040] (4) Same as base salt cleaning operation, add the fuel salt until the specified liquid level.

[0041] (5) Cooling. After the salt is loaded, the protective gas is continuously injected from the top of the first air inlet pipe and the top of the second air inlet pipe, and the protective gas is discharged from the air outlet pipe. The insulation layer is removed, the heating device is turned off, and the fuel salt is waited for to solidify gradually.

[0042] (6) Packaging. Since the protective gas is continuously blown into the device, there are still many pores in the solid molten salt after the fuel salt is condensed. The first air inlet pipe, the second air inlet pipe and the gas distributor are all filled with protective gas. After complete condensation, the valve of the first air inlet pipe, the valve of the second air inlet pipe and the valve of the air outlet pipe are all closed for packaging.

[0043] (7) Transportation. The isotope production device is transported as a whole to a designated reactor site using shock-absorbing packaging.

[0044] S2: In-pile operation and material replacement process, including the following steps:

[0045] (1) Nuclear thermal thawing. The isotope production device is installed in the reactor. The reactor is started. Through high-flux neutron irradiation, the fuel salt undergoes a nuclear fission reaction, releasing a large amount of heat. The fuel salt continues to heat up until it melts. Since the solid molten salt has a porous structure, it can absorb the thermal expansion stress caused by melting. Since the first air inlet pipe, the second air inlet pipe and the gas distributor are filled with protective gas and no solid molten salt, there is no local freezing problem.

[0046] (2) Isotope production. As the fuel salt undergoes continuous fission reactions, a large amount of fission products are produced, including some insoluble gases and isotope particles, such as Xe-133, Mo-99 and their precursor nuclei. These isotope particles are suspended in the fuel salt or attached to the wall.

[0047] (3) Isotope collection. The protective gas is blown into the device through the first air inlet pipe, and the gas forms bubbles in the fuel salt and passes through the fuel fission zone. Since the gas and isotope particles are easily attached to the bubble surface, the bubbles can bring them to the liquid surface of the fuel salt. The protective gas is blown into the device through the second air inlet pipe, and the particle isotopes break through the liquid surface under the impact of the protective gas, and are discharged from the device through the air outlet pipe along with the air flow, and then the isotopes are collected outside the device.

[0048] (4) Heat transfer. During operation, the isotope production device achieves temperature control through heat balance. Nuclear heat is generated in the fuel salt, and the flow of the fuel salt is achieved through bubbling and thermal gradient, making its internal temperature more uniform. Nuclear heat is then transferred from the fuel salt to the inner tube of the double-layer casing, and then transferred to the outer casing through thermal radiation. The outer casing is cooled by the cooling medium in the reactor.

[0049] (5) Device replacement. When the device reaches the end of its service life, in order to continue to use the fuel salt, the device can be replaced in the reactor. The specific process is: install a new radioactive isotope production device in the reactor, and the new device has been cleaned and packaged in the factory. Close the valves of the outlet pipes of the new and old devices, and interconnect the first air inlet pipe of the new device with the first air inlet pipe of the old device. By blowing gas into the second air inlet pipe of the old device, the fuel salt in the old device is pressed into the new device. Disconnect and close the valve. Take the old device out of the reactor to complete the replacement of the device in the reactor. A certain amount of new fuel salt can be pre-installed in the new device, and the salt can be replaced after nuclear heat heating. The new fuel salt added can make up for the problem of decreased isotope yield caused by the burnup of the old fuel, and at the same time make up for the problem of fuel salt loss caused by the residual fuel salt in the salt replacement process.

[0050] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0051] The positive and progressive effects of the present invention are:

[0052] (1) Compared with the current solid fuel fission target method, the radioactive isotope production device provided by the present invention has the advantages of high yield, online extraction, simple process flow and low cost;

[0053] (2) Compared with isotope production in molten salt reactors, the present invention does not require the reconstruction of reactors, and can utilize existing reactors and the radioactive isotope production device of the present invention to produce isotopes, which has the advantages of low construction threshold, simple device structure, and high reliability;

[0054] (3) The simple internal structure reduces the adhesion of isotopes to the wall, making the isotope extraction efficiency higher. In the molten salt reactor experiment, the proportion of isotope particles reaching the fuel salt liquid surface is about 50%, while the present invention is close to 100%, which greatly improves the isotope extraction efficiency;

[0055] (4) The radioisotope production device of the present invention is easy to replace when its service life reaches the end, which facilitates the reuse of fuel salt, reduces fuel loss, reduces radioactive waste, and reduces pollution;

[0056] (5) There is no problem of local freezing and blockage of various components during isotope production; there are a large number of bubbles in the solid molten salt, which can absorb local stress when melting, and the device is not easily damaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a schematic diagram of a radioisotope production facility;

[0058] Figure 2 Schematic diagram of the process of loading salt into a radioisotope production unit;

[0059] Figure 3 This is a schematic diagram of the operation and material replacement process of the radioisotope production device.

[0060] 1-double-layer casing; 2-fuel salt; 3-cover plate; 4-first air inlet pipe; 41-first air inlet pipe valve; 5-air outlet pipe; 51-air outlet pipe valve; 6-second air inlet pipe; 61-second air inlet pipe valve; 62-nozzle; 7-isotope particles; 8-bubbles; 9-protective gas space. DETAILED DESCRIPTION

[0061] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples.

[0062] The raw materials used in the following examples are all commercially available.

[0063] Example 1

[0064] S1: Loading process before loading, such as Figure 2 shown.

[0065] (1) Assemble the isotope production device in the factory. Preheat the device before loading salt. Heat the electric heating wire in the double-layer casing 1 and wrap the device with a thermal insulation layer of silicon fiber material to keep the temperature constant during the salt loading process.

[0066] (2) Open the first air inlet valve 41 and the air outlet valve 51 to pass the protective gas to purge oxygen impurities in the device.

[0067] (3) Cleaning the inside of the device with base salt (a mixture of NaF and ZrF4). Specifically, the base salt is pressed into the first air inlet pipe 4 by air pressure, and the protective gas is discharged from the air outlet pipe 5. After the base salt is filled, it is left to stand for a period of time, and then the protective gas is passed through the air outlet pipe 5 to discharge the base salt from the first air inlet pipe 4.

[0068] (4) Same as the base salt cleaning operation, add liquid fuel salt 2 until the specified liquid level.

[0069] (5) Cooling. After the salt is loaded, the first air inlet pipe 4 continuously injects the protective gas, while the second air inlet pipe valve 61 is opened to inject the protective gas, and the air outlet pipe 5 continues to discharge the protective gas. Remove the insulation layer, turn off the power supply of the electric heating wire, and wait for the fuel salt 2 to gradually solidify.

[0070] (6) Packaging. Since the protective gas is continuously blown into the device, there are still many pores inside the liquid fuel salt 2 after it is condensed into solid salt. The first air inlet pipe 4 and the second air inlet pipe 6 are both filled with protective gas. After complete condensation, the first air inlet pipe valve 41, the second air inlet pipe valve 61 and the air outlet pipe valve 51 are all closed for packaging.

[0071] (7) Transportation. The isotope production device shall be transported as a whole to the designated reactor site using shock-absorbing packaging.

[0072] S2: In-pile operation and replacement process, such as Figure 1 and 3 shown.

[0073] (1) Nuclear thermal thawing. Install the isotope production device in the reactor. Start the reactor, and through high-flux neutron irradiation, the fuel salt 2 undergoes a nuclear fission reaction, releasing a large amount of heat. The fuel salt 2 continues to heat up until it melts. Since the solid molten salt has a porous structure, it can absorb the thermal expansion stress caused by melting. Since there is no solid fuel in the first intake pipe 4 and the second intake pipe 6, there is no local freezing problem.

[0074] (2) Isotope production. As the fuel salt 2 undergoes continuous fission reactions, a large number of fission products are produced, including some insoluble gases and isotope particles 7, such as Xe-133, Mo-99 and their precursor nuclei. These isotope particles 7 are suspended in the fuel salt 2 or attached to the wall.

[0075] (3) Isotope collection. Open the first air inlet valve 41 and the second air inlet valve 61, and blow the protective gas into the device. The gas forms bubbles 8 in the fuel salt 2 and passes through the fuel fission zone. Since the gas and isotope particles 7 are easily attached to the bubble surface, the bubbles can bring them into the liquid level of the fuel salt 2. Then, the gas impact below the liquid level breaks through the liquid surface and brings the isotope particles 7 into the protective gas space 9. In the protective gas space 9, the isotopes are discharged from the outlet pipe 5 to the outside of the device along with the air flow, and then the isotopes are collected outside the device.

[0076] (4) Heat transfer. During operation, the isotope production device achieves temperature control through heat balance. Nuclear heat is generated in the fuel salt 2, and the flow of the fuel salt 2 is achieved through bubbling and thermal gradient, making its internal temperature more uniform. The nuclear heat is then transferred from the fuel salt 2 to the inner casing, and then to the outer casing through thermal radiation. The outer casing is cooled by the cooling medium in the reactor.

[0077] (5) Device replacement. When the device reaches the end of its service life, in order to continue to use the fuel salt 2, the nuclear fuel and the device can be replaced in the reactor. The specific process is: install a new isotope production device at the same position in the reactor. The new device has been cleaned and packaged in the factory. Close the outlet pipe valve 51 of the new and old devices, and interconnect the first air inlet pipe 4 of the new device with the first air inlet pipe 4 of the old device. By blowing gas into the second air inlet pipe 6 of the old device, the fuel salt 2 in the old device is pressed into the new device. Disconnect and close the valve. Take the old device out of the reactor to complete the replacement of the device and fuel salt 2 in the reactor. A certain amount of new fuel salt 2 can be pre-installed in the new device, and the salt can be replaced after nuclear heat heating. The new fuel salt 2 added can make up for the problem of decreased isotope production caused by the burnup of the old fuel, and at the same time make up for the problem of fuel salt loss caused by the residual fuel salt in the salt replacement process.

[0078] The radioactive isotope production device of Example 1 has a simple internal structure, which effectively reduces the adhesion of isotopes to the wall. Nearly 100% of the isotope particles are brought to the fuel salt liquid surface by bubbles. In the molten salt reactor experiment, the proportion of isotope particles reaching the fuel salt liquid surface is only about 50%, thereby greatly improving the isotope extraction efficiency.

Claims

1. A radioisotope production device, characterized in that: It includes: A container tube with one end open for filling fuel salt; a first air inlet pipe and a second air inlet pipe are arranged in the container tube; The top end of the first air inlet pipe and the top end of the second air inlet pipe are both located above the liquid level of the fuel salt; the bottom end of the first air inlet pipe is located below the liquid level; a gas distributor is provided at the bottom end of the second air inlet pipe; the gas outlet of the gas distributor is located below the liquid level and faces the liquid level; the bottom end of the first air inlet pipe is lower than the gas outlet of the gas distributor.

2. The radioisotope production device according to claim 1, characterized in that: The fuel salt includes nuclear fuel and base salt.

3. The radioisotope production device according to claim 2, characterized in that: The nuclear fuel is low-enriched uranium.

4. The radioisotope production device according to claim 2, characterized in that: The base salt is a fluoride and / or chloride of a metal M, wherein the metal M is one or more of the following elements: Li, Be, Na, K, Rb and Zr.

5. The radioisotope production device according to claim 4, characterized in that: The base salt is a mixture of NaF and ZrF4.

6. The radioisotope production device according to claim 1, characterized in that: The gas distributor is a nozzle.

7. The radioisotope production device according to claim 6, characterized in that: The surface of the nozzle is ellipsoidal.

8. The radioisotope production device according to claim 1, characterized in that: The open end of the containing tube is provided with a cover plate, and an air outlet pipe is provided on the cover plate, and the bottom end of the air outlet pipe is higher than the liquid surface; the air outlet pipe, the first air inlet pipe and the second air inlet pipe all pass through the cover plate.

9. The radioisotope production device according to claim 1, characterized in that: The bottom end of the first air inlet pipe is arranged close to the bottom of the accommodation pipe; And / or, the gas outlet of the gas distributor is arranged close to the liquid surface.

10. The radioisotope production device according to claim 8, characterized in that: The first air inlet pipe, the second air inlet pipe and the air outlet pipe are all provided with valves, and any of the valves can be switched between an open state and a closed state.

11. The radioisotope production device according to claim 1, characterized in that: The accommodating tube is a double-layer casing.

12. The radioisotope production device according to claim 11, characterized in that: A heating device is provided in the tube gap of the double-layer casing; And / or, a fuel salt monitoring device is arranged in the tube gap of the double-layer casing.

13. The radioisotope production device according to claim 12, characterized in that: The heating device is an electric heating wire.

14. The radioisotope production device according to claim 1, characterized in that: A heat-insulating layer is arranged on the outer periphery of the containing tube.

15. The radioisotope production device according to claim 14, characterized in that: The material of the thermal insulation layer is silicon fiber material.

16. The radioisotope production device according to claim 1, characterized in that: The material of the containing tube is nickel-based alloy; And / or, the bottom end of the accommodating tube is arc-shaped.

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