Tritium sampling device and method

Abstract

The invention discloses a tritium sampling device and method, and relates to the technical field of tritiated water sampling in air, the tritium sampling device comprises a sample collection module, the sample collection module is communicated with a sampling pipeline and can refrigerate sampling gas conveyed by a gas inlet pipeline of the sampling pipeline, and tritium-containing water vapor in the sampling gas is frozen and then collected; the temperature control module is connected with the sample collection module and can regulate and control the temperature of the sample collection module; the air pressure detection module is arranged on an air outlet pipeline of the sampling pipeline and can detect the air pressure in the air outlet pipeline and control the temperature control module to refrigerate or heat the sample collection module according to the air pressure. According to the invention, tritium-containing substances in organic and inorganic states in air can be efficiently collected, pipeline blockage can be avoided, and the sampling efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of sampling tritiated water in air, and in particular to a tritium sampling device and method. Background Art

[0002] Tritium is an important natural and artificial radioactive nuclide. Artificially produced tritium is produced as a byproduct in the atomic energy industry developed by humans. During the operation of nuclear power and the reprocessing of spent fuel, tritium and other radioactive substances will inevitably be discharged into the environment. This part of tritium is mainly discharged in gaseous and liquid forms. The tritium discharged into the environment will exchange with its isotope hydrogen, and with the migration and transformation of natural water cycles in different environments and organisms, its radioactivity will have a long-term impact on organisms and the environment. Therefore, monitoring the radiation dose of tritium around nuclear power plants and within the scope of biological activities has become an important measure to avoid serious radiation effects on organisms and the environment.

[0003] The radiation environment monitoring institutions known to the inventor mainly collect tritiated water in the environment through bubbling, condensation, freezing and desiccant adsorption, and measure the activity concentration of tritium with a liquid scintillation counter after distillation and purification. Among them, the freezing method has stronger environmental adaptability and can be used for normal sampling in cold and dry areas. However, when the freezing method is used, when the sampling temperature is lowered and the water vapor condenses into ice, it is easy to block the pipeline, thereby seriously affecting the sampling efficiency. Therefore, it is urgent to design a technical solution that can improve the sampling efficiency. Summary of the invention

[0004] The purpose of the present invention is to provide a tritium sampling device and method to solve the problems existing in the above-mentioned prior art and to improve the sampling efficiency of tritium in the air.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a tritium sampling device, comprising:

[0007] A sample collection module, which is connected to a sampling pipeline and is capable of refrigerating the sampled gas transported through the air inlet pipeline of the sampling pipeline, and freezing and collecting the tritium-containing water vapor in the sampled gas;

[0008] A temperature control module, connected to the sample collection module, capable of regulating the temperature of the sample collection module;

[0009] The air pressure detection module is arranged on the air outlet pipeline of the sampling pipeline, and can detect the gas pressure in the air outlet pipeline, and control the temperature control module to cool or heat the sample collection module accordingly.

[0010] Preferably, two sample collection modules are provided, and the two sample collection modules are connected in series through pipelines, and the air inlet pipeline is connected to one of the sample collection modules, and the air outlet pipeline is connected to the other sample collection module.

[0011] Preferably, it also includes a high-temperature catalytic module, which is a heating furnace encapsulated with alumina-supported platinum and palladium, so that the organic tritium-containing substance is catalytically oxidized into water vapor under the action of high temperature and catalyst; the high-temperature catalytic module is connected in series to the pipeline between the two sample collection modules, and can oxidize the gaseous tritium-containing organic matter in the sampled gas into carbon dioxide and tritium-containing water vapor, wherein the tritium-containing water vapor is further collected and the carbon dioxide is discharged.

[0012] Preferably, the sample collection module includes a first collection cold trap and a second collection cold trap of the same structure; the first collection cold trap includes a stainless steel tube, one end of the stainless steel tube is connected to an air inlet pipeline provided with a valve, and the other end is connected to the stainless steel tube of the second collection cold trap through a pipeline, and the end of the stainless steel tube of the second collection cold trap is connected to an air outlet pipeline provided with a valve; the stainless steel tube is coated with a heat conduction component, and the heat conduction component is connected to the temperature control module.

[0013] Preferably, the temperature control module includes a heating module and a circulating heat dissipation module, each of the heat conduction components is provided with the heating module, and the heat conduction components of the first collection cold trap and the second collection cold trap are provided with the circulating heat dissipation modules connected in series.

[0014] Preferably, the heating module comprises a heating wire, a longitudinal hole is provided in the heat conduction component, the heating wire is provided in the longitudinal hole, and the heating wire is externally connected to a power source.

[0015] Preferably, the circulating heat dissipation module includes a semiconductor refrigeration plate, and the heat conduction component of the first collection cold trap and the heat conduction component of the second collection cold trap are respectively attached with a semiconductor refrigeration plate. The hot end of each semiconductor refrigeration plate is connected in series to a hose through a water-cooled heat sink, and the hose is connected to an external cold source; a heat transfer medium is passed into the hose.

[0016] Preferably, the stainless steel tube is arranged vertically, and its bottom is a funnel-shaped structure.

[0017] Preferably, the heat conduction component includes two symmetrical copper blocks, and a concave arc groove is formed on one side of the copper block close to the stainless steel tube. The stainless steel tube is fixedly clamped between the two arc grooves, and the two copper blocks are fixedly connected by screws.

[0018] The present invention also provides a tritium sampling method, comprising the following steps:

[0019] After the sample collection module and the high-temperature catalytic module reach the set temperature value, the sample gas enters the sample collection module at a fixed flow rate; the air pressure detection module monitors the pressure of the sampling pipeline in real time. When the sampling pipeline is blocked by ice and causes air pressure changes, the heating module is turned on to actively heat the sample collection module and clear the pipeline;

[0020] The sampled gas passes through the first collection cold trap from bottom to top, and part of the tritium-containing water vapor therein is converted into liquid or solid under the action of low temperature and collected in a collection bottle;

[0021] The gaseous tritium-containing organic matter in the sampled gas is oxidized into tritium-containing water vapor and carbon dioxide through the high-temperature catalytic module;

[0022] The portion of the sampled gas that is not collected during the first condensation collection process and the tritium-containing water vapor produced by high-temperature catalysis pass through the second collection cold trap and are condensed and collected.

[0023] Compared with the prior art, the present invention has achieved the following technical effects:

[0024] The present invention is provided with an air pressure detection module and a temperature control module, and can collect tritium in the air by a freezing method. At the same time, the air pressure detection module is used to detect the air pressure in the sampling pipeline in real time. When the air pressure changes greatly, it can be determined whether the pipeline is blocked, so that the temperature control module can be adjusted in time according to the air pressure change to heat the sample collection module, thereby removing the blockage caused by low-temperature freezing in the pipeline and improving the sampling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic diagram of the arrangement of a tritium sampling device in one or some embodiments of the present invention;

[0027] Figure 2 It is a partial schematic diagram of a sample collection module of a tritium sampling device in one or some embodiments of the present invention.

[0028] In the figure: 1 is a sample collection module, 1-1 is a first collection cold trap, 1-2 is a second collection cold trap, 2 is a high temperature catalytic module, 3 is a circulating heat dissipation module, 4 is an air pressure detection module, 5 is a heating module, 6 is a stainless steel tube, 7 is a copper block, 8 is an electric heating wire, 9 is a semiconductor refrigeration sheet, 901 is a cold end, and 902 is a hot end. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The purpose of the present invention is to provide a tritium sampling device and method to solve the problems existing in the above-mentioned prior art and to improve the sampling efficiency of tritium in the air.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Tritium in the environment mainly comes from natural tritium and artificial tritium, and exists in the form of tritium gas (HT), tritium water (HTO) and organically bound tritium (OBT); the freezing sampling of tritium is a sampling method in which air passes through a cold trap through a sampling pipeline, and the cold trap is cooled to below the freezing point with liquid nitrogen or a semiconductor refrigeration element, so that the tritiated water in the air is frozen into a solid state. After the sampling is completed, a heating device is required to melt and collect the captured frozen ice. The current freezing sampling device is prone to ice formation in the pipeline due to the low temperature, thereby causing the pipeline to be blocked. In order to solve this problem, the present invention provides a tritium sampling device, such as Figure 1 , Figure 2 As shown, it includes a sample collection module 1, a temperature control module, a high-temperature catalytic module 2 and an air pressure detection module 4. Two sample collection modules 1 are provided. The two sample collection modules 1 are connected in series through pipelines, and the air inlet pipeline of the sampling pipeline is connected to one of the sample collection modules 1, and the air outlet pipeline is connected to the other sample collection module 1. The air inlet of the sampling pipeline is connected to an air source, and the air source conveys the air to be sampled into the air inlet pipeline. The high-temperature catalytic module 2 is connected in series on the pipeline between the two sample collection modules 1, and it can oxidize the gaseous tritium-containing organic matter in the sampled gas into carbon dioxide and tritium-containing water vapor; the air pressure detection module 4 is arranged on the air outlet pipeline of the sampling pipeline, and can detect the gas pressure in the air outlet pipeline, and control the temperature control module to cool or heat the sample collection module 1 accordingly. The two sample collection modules 1 are connected by a high-temperature catalytic module 2, which can realize the collection of organic and inorganic tritium-containing substances respectively; the present invention adopts the principle of low-temperature condensation and high-temperature catalytic oxidation, which can efficiently collect organic and inorganic tritium-containing substances in the air, and the device can be connected to an external cold source to adapt to a higher temperature sampling environment. The device has high collection efficiency and is easy to operate. It is suitable for tritium sampling in indoor and outdoor environments, chimneys, and exhaust ducts in fields including environmental monitoring, nuclear power plants, nuclear industry, radioactive waste treatment plants, and isotope laboratories.

[0033] In a preferred embodiment, the sample collection module 1 includes a first collection cold trap 1-1 and a second collection cold trap 1-2 of the same structure, which can be connected to their respective collection bottles through pipelines to facilitate sample collection; the first collection cold trap 1-1 includes a vertically arranged stainless steel pipe 6, and the bottom of the stainless steel pipe 6 is a funnel-shaped structure; one end of the stainless steel pipe 6 is connected to an air inlet pipeline with a valve, and the other end is connected to the stainless steel pipe 6 of the second collection cold trap 1-2 through a pipeline, and the end of the stainless steel pipe 6 of the second collection cold trap 1-2 is connected to an air outlet pipeline with a valve; the stainless steel pipe 6 is coated with a heat conduction component, and the heat conduction component is connected to a temperature control module. The temperature control module of this embodiment includes a heating module 5 and a circulating heat dissipation module 3, each heat conduction component is provided with a longitudinal hole, and the longitudinal hole is provided with a heating wire 8 of the heating module 5, and the heating wire 8 is externally connected to a power source. The circulating heat dissipation module 3 of the present embodiment includes a semiconductor refrigeration plate 9. A semiconductor refrigeration plate 9 is attached to the heat conduction component of the first collection cold trap 1-1 and the heat conduction component of the second collection cold trap 1-2, respectively, and is attached to the cold end 901 of the semiconductor refrigeration plate 9. The hot end 902 of each semiconductor refrigeration plate 9 is connected in series to a hose through a water-cooled heat sink, and the hose is connected to an external cold source; the hose serves as a refrigerant circulation pipeline, and its external cold source inlet and outlet are respectively provided with valves, and an external cold source can be connected. Antifreeze is introduced into the hose as a heat transfer medium, and the cold source includes a radiator, which is a known structure; the hose has an external refrigerant interface and is installed with a valve, and the opening and closing of the valve can be used to select whether to add an additional cold source to adapt to a sampling environment with worse temperature conditions.

[0034] The present invention uses a vacuum pump connected to the air intake pipeline as a power source for the sampled gas. The sampled gas first passes through a flow meter arranged on the air intake pipeline, and then passes through a first collecting cold trap 1-1 to collect most of the tritium-containing water vapor therein. The organic tritium-containing substance in the sampled gas passes through a high-temperature catalytic module 2, and is further catalyzed into the form of carbon dioxide and tritium-containing water vapor under the action of high temperature and catalyst, and then enters a second collecting cold trap 1-2 with a small amount of remaining tritium-containing water vapor not collected by the first collecting cold trap 1-1 to continue freezing and collecting.

[0035] The present invention adopts semiconductor refrigeration to efficiently collect tritium-containing water vapor in the environment through the first collection cold trap 1-1 and the second collection cold trap 1-2. At the same time, a catalytic furnace is installed between the two cold traps as a high-temperature catalytic module 2. After the first collection cold trap 1-1 samples the tritium-containing water vapor in the air, the tritium-containing organic matter in the air is oxidized and catalyzed into carbon dioxide and tritium-containing water vapor, and then enters the second collection cold trap 1-2 for continued freezing and collection. An air pressure detection module 4 is set at the end of the sampling pipeline to detect whether the pipeline is blocked due to ice formation. At the same time, it can automatically heat and defrost through a control system such as a computer to maintain normal operation of the equipment.

[0036] In order to improve the heat transfer efficiency, the heat conduction component in this embodiment includes two symmetrical copper blocks 7. The copper block 7 is provided with a concave arc groove on one side close to the stainless steel tube 6. The stainless steel tube 6 is fixedly clamped between the two arc grooves, and the two copper blocks 7 are fixedly connected by screws.

[0037] The present invention also provides a tritium sampling method, comprising the following steps:

[0038] After the sample collection module 1 and the high-temperature catalytic module 2 reach the set temperature value, the sampled gas enters the sample collection module 1 at a fixed flow rate; the air pressure detection module 4 monitors the pressure of the sampling pipeline in real time. When the sampling pipeline is blocked by ice and causes the air pressure to change, the heating module 5 is turned on to heat the sample collection module 1 in an active heating manner to clear the pipeline; the sampled gas passes through the first collection cold trap 1-1 from bottom to top, and part of the tritium-containing water vapor therein is converted into liquid or solid under the action of low temperature and is collected in the collection bottle; the gaseous tritium-containing organic matter in the sampled gas passes through the high-temperature catalytic module 2 and is oxidized into tritium-containing water vapor and carbon dioxide; the part of the sampled gas that is not collected in the first condensation and collection process and the tritium-containing water vapor generated by high-temperature catalysis pass through the second collection cold trap 1-2 and are condensed and collected.

[0039] Embodiment 1

[0040] In order to verify the sampling efficiency of the technical solution of the present invention, the experiment of this embodiment was designed. It was found through the experiment that it has a high recovery efficiency for tritiated water in the air.

[0041] In this embodiment, the experiment is carried out according to the following principle: a tritium standard sample with known activity is used, and an air purge method is adopted, in which the sampling gas is carried by a carrier gas (nitrogen) into the air inlet pipeline of the device of the present invention, and the sampling is collected in turn using a collecting bottle, which is vertically fixed under the stainless steel pipe 6 by the thread designed by the outer shell of the device of the present invention, and liquid water flows into the collecting bottle by gravity and is collected. After the collection is completed, the activity of tritium in the collecting bottle of the first collecting cold trap 1-1 and the collecting bottle of the second collecting cold trap 1-2 is measured, and the collection efficiency of the device of the present invention is calculated to achieve the purpose of testing the recovery efficiency in the air.

[0042] This embodiment is carried out according to the following steps:

[0043] a. Prepare three background samples. Take 8 ml of tritium-free water and 12 ml of scintillation fluid and mix them evenly. Record them as N 01 、N 02 、N 03 .

[0044] b. Prepare three standard samples. Take 8 ml of tritium-free water and 12 ml of scintillation fluid respectively, add 10 ul of tritium standard substance and mix well. Record them as Ns1 、N s2 、N s3 .

[0045] c. Take 10 μl of tritium standard substance and add it into 50 mL of tritium-free water, and put it into a mature bubbling bottle with a known structure. The bubbling end of the bubbling bottle is connected to high-purity nitrogen, and the other end is connected to the air inlet pipeline of the present invention.

[0046] d. Measure the mass of the collected samples by differential weight method. First, measure the mass of the empty bottle of the first collection cold trap 1-1 and the empty bottle of the second collection cold trap 1-2, which are recorded as m P01 、m P02 , and install them at the sampling bottle mouth position of the first collection cold trap 1-1 and the sampling bottle mouth position of the second collection cold trap 1-2 respectively.

[0047] e. Turn on the refrigeration, and when the temperature of the device of the present invention drops to -20°C, turn on the nitrogen and set the flow rate to 60L / h. Stop sampling when the mass loss of the bubbling bottle is constant. The marked liquid in the bubbling bottle is converted into gas by bubbling evaporation. When all the liquid water is converted into gas or the mass of the remaining liquid water in the bubbling bottle is so small that it cannot be evaporated by bubbling, weigh the mass of the bubbling bottle several times and the mass of the lost water remains unchanged. Turn on the thawing function, collect all the samples in two collection bottles, weigh them separately and record them as m P11 、m P12 .

[0048] f. First, mix the tritium-containing water in the two collection bottles evenly, then accurately measure 8 ml of the mixed sample, and then add 12 ml of scintillation liquid to the measured 8 ml of the mixed sample and shake well for testing. Prepare three samples in the same way and measure the activity and record it as N. 11 、N 12 、N 13 .

[0049] The experimental data are as follows:

[0050]

[0051]

[0052]

[0053]

[0054] Recovery efficiency η

[0055]

[0056] It can be seen from the data that when the carrier gas flow rate is 60 L / h and the freezing temperature is -20°C, the collection efficiency of the tritiated water vapor is 98.4%.

[0057] This embodiment illustrates that the present invention has a very high collection efficiency for tritiated water under conventional sampling conditions, and can actively detect pipeline blockages and automatically start heating during the sampling process, thereby improving sampling efficiency and saving sampling time.

[0058] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A tritium sampling device, characterized in that: include: A sample collection module, which is connected to a sampling pipeline and is capable of refrigerating the sampled gas transported through the air inlet pipeline of the sampling pipeline, and freezing and collecting the tritium-containing water vapor in the sampled gas; A temperature control module, connected to the sample collection module, capable of regulating the temperature of the sample collection module; The air pressure detection module is arranged on the air outlet pipeline of the sampling pipeline, and can detect the gas pressure in the air outlet pipeline, and control the temperature control module to cool or heat the sample collection module accordingly.

2. The tritium sampling device according to claim 1, characterized in that: The sample collection modules are provided with two, and the two sample collection modules are connected in series through pipelines, and the air inlet pipeline is connected to one of the sample collection modules, and the air outlet pipeline is connected to the other sample collection module.

3. The tritium sampling device according to claim 2, characterized in that: It also includes a high-temperature catalytic module, which is connected in series on the pipeline between the two sample collection modules and can oxidize the gaseous tritium-containing organic matter in the sampled gas into carbon dioxide and tritium-containing water vapor.

4. The tritium sampling device according to claim 1, characterized in that: The sample collection module includes a first collection cold trap and a second collection cold trap with the same structure; the first collection cold trap includes a stainless steel tube, one end of the stainless steel tube is connected to an air inlet pipeline with a valve, and the other end is connected to the stainless steel tube of the second collection cold trap through a pipeline, and the end of the stainless steel tube of the second collection cold trap is connected to an air outlet pipeline with a valve; the stainless steel tube is coated with a heat conduction component, and the heat conduction component is connected to the temperature control module.

5. The tritium sampling device according to claim 4, characterized in that: The temperature control module includes a heating module and a circulating heat dissipation module. The heating module is provided on each of the heat conduction components. The heat conduction components of the first collection cold trap and the second collection cold trap are provided with the circulating heat dissipation modules connected in series.

6. The tritium sampling device according to claim 5, characterized in that: The heating module comprises a heating wire. A longitudinal hole is provided in the heat conduction component. The heating wire is arranged in the longitudinal hole. The heating wire is externally connected to a power source.

7. The tritium sampling device according to claim 5, characterized in that: The circulating heat dissipation module includes a semiconductor refrigeration plate, and the heat conduction component of the first collection cold trap and the heat conduction component of the second collection cold trap are respectively attached with a semiconductor refrigeration plate. The hot end of each semiconductor refrigeration plate is connected in series to a hose through a water-cooled heat sink, and the hose is connected to an external cold source; a heat transfer medium is passed into the hose.

8. The tritium sampling device according to claim 4, characterized in that: The stainless steel pipe is arranged vertically, and the bottom thereof is in a funnel-shaped structure.

9. The tritium sampling device according to claim 4, characterized in that: The heat conduction component includes two symmetrical copper blocks. A concave arc groove is opened on one side of the copper block close to the stainless steel pipe. The stainless steel pipe is fixedly clamped between the two arc grooves, and the two copper blocks are fixedly connected by screws.

10. A tritium sampling method, characterized in that: The steps include: After the sample collection module and the high-temperature catalytic module reach the set temperature value, the sample gas enters the sample collection module at a fixed flow rate; the air pressure detection module monitors the pressure of the sampling pipeline in real time. When the sampling pipeline is blocked by ice and causes air pressure changes, the heating module is turned on to actively heat the sample collection module and clear the pipeline; The sampled gas passes through the first collection cold trap from bottom to top, and part of the tritium-containing water vapor therein is converted into liquid or solid under the action of low temperature and collected in a collection bottle; The gaseous tritium-containing organic matter in the sampled gas is oxidized into tritium-containing water vapor and carbon dioxide through the high-temperature catalytic module; The portion of the sampled gas that is not collected during the first condensation collection process and the tritium-containing water vapor produced by high-temperature catalysis pass through the second collection cold trap and are condensed and collected.

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