Tritiated hydrogen sample preparation device for liquid flash measurement and sample preparation and measurement method

Abstract

The invention relates to the technical field of radioactive substance content measurement, and discloses a tritiated hydrogen sample preparation device for liquid flash measurement and a sample preparation and measurement method. During sample preparation, a gas supply module provides a to-be-measured tritiated hydrogen sample, hydrogen, air and water vapor, and the flow of each gas is adjusted through a corresponding mass flow meter and a control valve; the method comprises the following steps: taking tritiated hydrogen as a gas source, mixing the gas, performing catalytic oxidation on the mixed gas through a catalytic oxidation module, converting the tritiated hydrogen into a tritiated water sample, and collecting the converted tritiated water sample by a collection module for measuring the content of the tritiated hydrogen. In combination with the measurement of the low background liquid flash instrument, the measurement of the tritiated hydrogen with low activity content can be realized, and the measurement requirement of the tritiated hydrogen with wide measuring range can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of radioactive substance content measurement, in particular to a low-content tritiated hydrogen sample preparation device for liquid scintillation measurement and a sample preparation and measurement method. Background Art

[0002] The quantitative analysis of low-activity tritiated hydrogen (HT) plays a crucial role in tritium monitoring and measurement, including but not limited to the monitoring of tritium-containing nuclear facilities and the determination of tritium content in waste generated during reactor decommissioning. Currently, the main techniques for measuring low-activity gaseous tritium include ionization chambers, proportional counting, and liquid scintillation counting.

[0003] Although the ionization chamber method and the proportional counting method can provide online monitoring capabilities for tritium, these technologies are generally suitable for measuring gaseous tritium with a concentration of 10Bq / L (under standard conditions) or higher, and their measurement range is relatively narrow. This limits their application potential in scenarios with extremely low tritium content and large concentration fluctuations. Relatively speaking, the liquid scintillation counting method exhibits a lower detection limit, and its ability to detect tritium activity in water can be reduced to below 1Bq / L (liquid volume), and this method has no memory effect and can adapt to the measurement needs of a wide range of tritium activity. However, it is worth noting that the liquid scintillation counting method is not suitable for direct measurement of gaseous samples. It requires that gaseous tritium be converted into liquid water before it can be effectively measured using a liquid scintillation analyzer.

[0004] Therefore, to address the challenges faced by existing technologies in measuring low-activity gaseous tritium, particularly the need to effectively convert gaseous tritium samples into liquid water samples suitable for liquid scintillation counting, this paper proposes an innovative low-activity tritiated hydrogen sample preparation device and measurement method. By optimizing conversion efficiency and collection technology, this method achieves high-precision measurement of low-activity tritiated hydrogen, expanding the application of liquid scintillation counting in tritium measurement and meeting market demand for low-activity tritium measurement. Summary of the Invention

[0005] In view of the difficulty in measuring the low-activity concentration tritiated hydrogen content in the above-mentioned prior art, the object of the present invention is to provide a tritiated hydrogen sample preparation device and a sample preparation and measurement method for liquid scintillation measurement, which can use a catalytic oxidation method to convert tritiated hydrogen into liquid tritiated water, so as to facilitate the measurement of tritiated hydrogen (HT) content by liquid scintillation measurement.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A tritiated hydrogen sample preparation device for liquid scintillation measurement, comprising:

[0008] The gas supply module is used to provide the tritiated hydrogen sample to be tested, hydrogen, air and water vapor, and adjust the flow rate of each gas through the corresponding mass flow meter and control valve;

[0009] A catalytic oxidation module, used for catalytically converting tritiated hydrogen into tritiated water samples;

[0010] The collection module is used to collect the converted tritiated water sample for the measurement of tritiated hydrogen content.

[0011] In the tritiated hydrogen sample preparation device for liquid scintillation measurement, the gas supply module includes: a sample air inlet unit, a hydrogen supply unit, an air supply unit, a water vapor supply unit, a gas mixing pipe, a first mass flow meter, a first control valve, a second mass flow meter, a second control valve, a third mass flow meter, a third control valve and a water vapor control valve group;

[0012] The sample air intake unit is connected to the first mass flowmeter and the first control valve, the hydrogen supply unit is connected to the second mass flowmeter and the second control valve, the air supply unit is connected to the third mass flowmeter and the third control valve, and the water vapor supply unit is connected to the water vapor control valve group for adjusting the supply of water vapor; the sample air intake unit, the hydrogen supply unit, the air supply unit, and the water vapor supply unit are respectively controlled by the first control valve, the second control valve, the third control valve, and the water vapor control valve group to input the tritiated hydrogen sample to be measured, hydrogen, air, and water vapor into the mixing pipe, and then sent into the catalytic oxidation module after mixing.

[0013] In the tritiated hydrogen sample preparation device for liquid scintillation measurement, the water vapor supply unit includes a first bubbler, the water vapor control valve group includes a fourth control valve, a fifth control valve and a sixth control valve, the input end of the first bubbler is connected to one end of the third control valve and one end of the fourth control valve through the fifth control valve, and the output end of the first bubbler is connected to the other end of the fourth control valve, one end of the first control valve and the input end of the mixing pipe through the sixth control valve.

[0014] In the tritiated hydrogen sample preparation device for liquid scintillation measurement, the catalytic oxidation module includes:

[0015] a catalytic bed filled with a hydrogen-oxygen composite catalyst;

[0016] The temperature and heating rate of the high temperature furnace are controlled by an external programmable controller. The temperature range is 100-1000℃ and the heating rate is 10-100℃ / min.

[0017] In the tritiated hydrogen sample preparation device for liquid scintillation measurement, the collection module includes:

[0018] A bubbling collection device comprises a second bubbler and a third bubbler connected in series in two stages, wherein the second bubbler and the third bubbler are provided with 5-50 ml of tritium-free water;

[0019] and / or,

[0020] Cold trap collection device, the temperature of the cold trap collection device is controlled at 0℃ to -196℃.

[0021] A sample preparation and measurement method using a tritiated hydrogen sample preparation device, comprising:

[0022] Air is introduced into the catalytic oxidation module, and the catalytic oxidation module is heated to a preset temperature for 10-60 minutes;

[0023] The gas supply module provides the tritiated hydrogen sample to be tested, hydrogen, and air, which are mixed and then sent to the catalytic oxidation module. The catalytic oxidation module catalytically converts the tritiated hydrogen into a tritiated water sample, and the collection module collects the converted tritiated water sample.

[0024] The collected tritiated water samples were mixed with liquid scintillator and placed in a low-background liquid scintillation instrument for measurement.

[0025] In the sample preparation and measurement method, the collected tritiated water sample is mixed with liquid scintillator and then placed in a low-background liquid scintillation instrument for measurement, which also includes:

[0026] Hydrogen, air and water vapor are introduced into the catalytic oxidation module and the collection module from the gas supply module to clean the catalytic oxidation module and the collection module to remove residual tritium in the gas supply pipeline and the catalytic oxidation module.

[0027] In the sample preparation and measurement method, after the tritiated hydrogen sample to be measured, hydrogen, and air are provided and mixed by the gas supply module, the method further includes:

[0028] The gas supply module provides water vapor, which is mixed with the tritiated hydrogen sample to be tested, hydrogen, and air.

[0029] In the sample preparation and measurement method, the gas supply module provides a tritiated hydrogen sample to be measured, hydrogen, and air, which are mixed and then sent to a catalytic oxidation module. The catalytic oxidation module catalytically converts the tritiated hydrogen into a tritiated water sample, and the collection module collects the converted tritiated water sample, which also includes:

[0030] The gas supply module controls the flow rate of the tritiated hydrogen sample to be tested to 0-100 ml / min, the flow rate of hydrogen and air to 0-1 L / min, controls the temperature of the first bubbler to 25-80°C, and the temperature of the catalytic oxidation module to 100-800°C;

[0031] The collection module collects tritiated water samples after conversion using a bubbling collection device and / or a low-temperature cold trap collection device.

[0032] In the sample preparation and measurement method, the step of introducing hydrogen, air, and water vapor from the gas supply module into the catalytic oxidation module and the collection module to clean the catalytic oxidation module and the collection module to remove residual tritiated hydrogen includes:

[0033] The flow rates of hydrogen and air are controlled at 0-1 L / min by a first mass flow meter and a second mass flow meter respectively; the temperature of the first bubbler is controlled at 25-80° C. to provide water vapor;

[0034] The hydrogen, air and water vapor are mixed and sent into the catalytic oxidation module and the collection module for cleaning for 10-60 minutes.

[0035] Compared with the prior art, in the tritiated hydrogen sample preparation device for liquid scintillator measurement provided by the present invention, a gas supply module provides a tritiated hydrogen sample to be measured, hydrogen, air and water vapor, and the flow rate of each gas is adjusted by a corresponding mass flow meter and a control valve, and these gases are mixed. At the same time, the mixed gas is catalytically oxidized by a catalytic oxidation module to convert the tritiated hydrogen into a tritiated water sample, and the converted tritiated water sample is collected by a collection module for measurement of the tritiated hydrogen content. The present invention, combined with the measurement of a low-background liquid scintillator, can realize the measurement of tritiated hydrogen with low activity content and can meet the measurement requirements of tritiated hydrogen over a wide range. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the tritiated hydrogen sample preparation device for liquid scintillation measurement provided by the present invention.

[0037] Figure 2 This is a schematic diagram of a bubble collector in a tritiated hydrogen sample preparation device for liquid scintillation measurement provided by the present invention.

[0038] Figure 3 This is a schematic diagram of a cold trap collector in a tritiated hydrogen sample preparation device for liquid scintillation measurement provided by the present invention.

[0039] Description of Reference Numerals

[0040] Sample air intake unit 11, hydrogen supply unit 12, air supply unit 13, water vapor supply unit 14, gas mixing pipe 15, first mass flowmeter F1, first control valve V1, second mass flowmeter F2, second control valve V2, third mass flowmeter F3, third control valve V3, water vapor control valve group 16, first bubbler 17, fourth control valve V4, fifth control valve V5, sixth control valve V6, catalytic oxidation module 20, catalytic bed 21, high temperature furnace 22, collection module 30, bubbling collection device 31, second bubbler 311, third bubbler 312, cold trap collection device 32 DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present 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 only used to explain the present invention and are not intended to limit the present invention.

[0042] The tritiated hydrogen sample preparation device provided by the present invention is mainly used for measuring tritiated hydrogen with low activity concentration. It uses a catalytic oxidation method to convert tritiated hydrogen (HT) into liquid tritiated water (HTO), and then measures it through liquid scintillation counting (liquid scintillation analysis). It can meet the measurement requirements of tritiated hydrogen (HT) with an activity concentration level of the lowest 10-12 Ci / L (Curie per liter, Ci / L, Curie per liter) (standard gas) and can also meet the continuous measurement of tritium over a wide range.

[0043] See also Figure 1 The tritiated hydrogen sample preparation device for liquid scintillation measurement provided by the present invention includes a gas supply module (not numbered in the figure), a catalytic oxidation module 20 and a collection module 30, wherein the gas supply module is used to provide the tritiated hydrogen sample to be measured, hydrogen, air and water vapor, and adjust the flow rate of each gas through the corresponding mass flow meter and control valve; the catalytic oxidation module 20 is used to catalytically convert tritiated hydrogen into a tritiated water sample; and the collection module 30 is used to collect the converted tritiated water sample for measurement of the tritiated hydrogen content.

[0044] Since gaseous tritiated hydrogen (HT) is difficult to measure directly by liquid scintillation counting, it needs to be converted into liquid tritiated water (HTO) through a catalytic oxidation reaction. HT reacts with oxygen in the presence of a catalyst to produce HTO. The reaction formula is as follows:

[0045]

[0046] The catalyst may be copper oxide (CuO), platinum or palladium supported on alumina, etc., and the reaction temperature is usually between 100-800°C.

[0047] Optionally, the gas supply module includes: a sample air intake unit 11, a hydrogen supply unit 12, an air supply unit 13, a water vapor supply unit 14, a gas mixing pipe 15, a first mass flow meter F1, a first control valve V1, a second mass flow meter F2, a second control valve V2, a third mass flow meter F3, a third control valve V3 and a water vapor control valve group 16. Each unit is connected to the gas mixing pipe 15 through a pipeline, and each mass flow meter and control valve can be set on the corresponding pipeline.

[0048] The sample air intake unit 11 is connected to the first mass flowmeter F1 and the first control valve V1, and the first mass flowmeter F1 quantitatively controls the sample injection amount. The hydrogen supply unit 12 is connected to the second mass flowmeter F2 and the second control valve V2, and the second mass flowmeter F2 controls the flow rate of hydrogen. The air supply unit 13 is connected to the third mass flowmeter F3 and the third control valve V3, and the third mass flowmeter F3 controls the flow rate of air. The present invention uses three mass flowmeters and three control valves to control the flow rate and on-off state of tritiated hydrogen gas, hydrogen and air respectively.

[0049] The water vapor supply unit 14 is connected to the water vapor control valve group 16 for regulating the water vapor supply. The water vapor control valve group 16 adjusts the on / off state of the water vapor supply. The mixing pipe 15 is used to evenly mix all gases before entering the catalytic oxidation module 20. The sample air intake unit 11, hydrogen supply unit 12, air supply unit 13, and water vapor supply unit 14 are controlled by the first control valve V1, the second control valve V2, the third control valve V3, and the water vapor control valve group 16, respectively, to input the tritiated hydrogen sample to be measured, hydrogen, air, and water vapor into the mixing pipe 15 before being mixed and delivered to the catalytic oxidation module 20.

[0050] Optionally, the water vapor supply unit 14 includes a first bubbler 17, and the water vapor control valve group 16 includes a fourth control valve V4, a fifth control valve V5 and a sixth control valve V6. The input end of the first bubbler 17 is connected to one end of the third control valve V3 and one end of the fourth control valve V4 through the fifth control valve V5, and the output end of the first bubbler 17 is connected to the other end of the fourth control valve V4, one end of the first control valve V1 and the input end of the mixing pipe 15 through the sixth control valve V6.

[0051] In this embodiment, the first bubbler 17 regulates the opening and closing of the water vapor supply via the fourth, fifth, and sixth control valves connected thereto, thereby adjusting whether water vapor is introduced into the gas mixing pipe 15 and the flow rate of the water vapor introduced. The first, second, third, fourth, fifth, and sixth control valves can all be two-way valves, and can also be manually or automatically opened and closed control valves, such as solenoid valves.

[0052] Optionally, the catalytic oxidation module 20 is connected to the rear end of the gas supply module, and includes: a catalyst bed 21 and a high-temperature furnace 22, wherein the catalyst bed 21 is a fixed bed reactor filled with a hydrogen-oxygen composite catalyst; the highly active hydrogen-oxygen composite catalyst is copper oxide, platinum supported on alumina, palladium supported on alumina, etc.

[0053] The high temperature furnace 22 is arranged outside the catalyst bed 21. The temperature and heating rate of the high temperature furnace 22 are controlled by an external programmable controller. The temperature range is 100-1000°C, and the heating rate is 10-100°C / min.

[0054] The collection module 30 is connected to the outlet of the catalytic oxidation module 20, and includes: a bubbling collection device 31 and / or a cold trap collection device 32. The bubbling collection device 31 and the cold trap collection device 32 are sample collection devices with two different measurement methods. Among them, the cold trap collection device 32 does not add background water for dilution during the process of collecting tritiated hydrogen samples, and the detection limit is lower, but the measurement operation is more complicated than the low background liquid scintillation measurement method of the bubbling collection device 31. The bubbling collection device 31 is relatively simple to operate during measurement, but the detection limit of the determination of low concentration tritium may be slightly higher than that of the cold trap collection device 32. The present invention can select the type of collection device according to the activity range of tritium, or select both collection devices and then make a comprehensive judgment.

[0055] Please also refer to Figure 2 In an optional embodiment, the bubble collection device 31 includes a second bubbler 311 and a third bubbler 312 connected in series in two stages, and 5-50 ml of tritium-free water is provided in the second bubbler 311 and the third bubbler 312.

[0056] Please also refer to Figure 3 The cold trap collection device 32 is a glass bottle with a short inlet and a long outlet. It can be cooled by using semiconductor refrigeration cold trap, liquid nitrogen Dewar, liquid nitrogen-alcohol bath, etc. The temperature of the cold trap collection device 32 is controlled at 0℃ to -196℃.

[0057] The present invention converts the low-activity concentration tritiated hydrogen to be measured into liquid tritiated water (HTO) by adding hydrogen, air, and water vapor to the low-activity concentration tritiated hydrogen gas through a hydrogen-oxygen catalytic bed 21. The sample required for low-background liquid scintillation testing is then obtained through methods such as freezing and bubbling collection. The present invention improves the final catalytic conversion efficiency of tritium by adding hydrogen, and increases the quality of the final water sample by adding water vapor. Using the sample preparation device of the present invention, 4-15g of HTO sample can be collected, significantly reducing the volume of the required test sample while ensuring measurement accuracy.

[0058] Based on the above-mentioned tritiated hydrogen sample preparation device for liquid scintillation measurement, the present invention also provides a method for preparing the tritiated hydrogen sample preparation device for liquid scintillation measurement, which comprises the following steps:

[0059] S1. Air is introduced into the catalytic oxidation module 20 and the catalytic oxidation module 20 is heated to a preset temperature for 10-60 minutes;

[0060] S2. The gas supply module provides a tritiated hydrogen sample to be tested, hydrogen, and air, which are mixed and then sent to the catalytic oxidation module 20. The catalytic oxidation module 20 catalytically converts the tritiated hydrogen into a tritiated water sample, and the collection module 30 collects the converted tritiated water sample.

[0061] S3. Mix the collected tritiated water sample with liquid scintillator and place it in a low-background liquid scintillation instrument for measurement.

[0062] Wherein, in step S2, the flow rate of the tritiated hydrogen sample to be measured is 0-100 ml / min, the flow rates of hydrogen and air are 0-1 L / min, and the sample preparation time in the catalytic oxidation module 20 is 10-60 min.

[0063] Furthermore, before step S3 , step S21 is also included, in which hydrogen, air and water vapor are introduced from the gas supply module to the catalytic oxidation module 20 and the collection module 30 to clean the catalytic oxidation module 20 and the collection module 30 to remove residual tritium in the gas supply pipeline and the catalytic oxidation module 20 .

[0064] Furthermore, step S1 also includes: the gas supply module provides water vapor, which is mixed with the tritiated hydrogen sample to be measured, hydrogen, and air. In this embodiment, the control valve enables the first bubbler 17 to provide water vapor.

[0065] Optionally, in step S1, the gas supply module controls the flow rate of the tritiated hydrogen sample to be tested to 0-100 ml / min, the flow rate of hydrogen and air to 0-1 L / min, controls the temperature of the first bubbler 17 to 25-100°C, the temperature of the catalytic oxidation module 20 to 100-800°C, and controls the temperature of the mixing pipe 15 to 60-100°C.

[0066] The collection module 30 collects tritiated water samples after conversion using a bubbling collection device 31 and / or a cryogenic cold trap collection device 32. When the bubbling collection device 31 is used to collect tritiated water, 5-50 ml of tritium-free water is added to the second and third bubblers 312. The tritium-free water can be deep well water, distilled water, or the like.

[0067] Furthermore, the step S21 includes:

[0068] S211, respectively controlling the flow rates of hydrogen and air to 0-1 L / min through the first mass flow meter F1 and the second mass flow meter F2; controlling the temperature of the first bubbler 17 to 25-80°C to provide water vapor;

[0069] S212: Mix hydrogen, air and water vapor and send them into the catalytic oxidation module 20 and the collection module 30 for cleaning for 10-60 minutes.

[0070] In step S3, the liquid scintillation measurement includes: mixing the prepared HTO sample with liquid scintillation liquid in a certain volume ratio, and then placing the sample in a low-background liquid scintillation instrument for measurement for a certain time.

[0071] Optionally, the total volume of the HTO sample and liquid scintillator is 20-50 ml, and the mass ratio of HTO sample to liquid scintillator is 2:18, 3:17, 4:16 or 5:15.

[0072] Optionally, the liquid scintillator may be one or more of Ultima Gold, Ultima Gold AB, Ultima Gold μLLT, American Optiphase Hisafe 3, etc.

[0073] Optionally, the low-background liquid scintillation instrument may be LSC-LB5 or LSC-LB7 produced by Aloka Corporation of Japan, or Quantulus 1220 produced by Perkin Elmer Corporation of the United States.

[0074] Furthermore, after mixing the HTO sample and liquid scintillator, the low-background liquid scintillation counter was placed in the instrument for 6-24 hours and measured, and the detection limit during the measurement was 0.5-1 Bq / L. In other words, the liquid scintillation counter can control the detection limit between 0.5 Bq / L and 1 Bq / L within the 6-24 hour measurement period. This means that when measuring low-activity tritiated water, the instrument can detect the lowest activity concentration within this range, significantly reducing the detection limit.

[0075] Low-activity content tritiated hydrogen (HT) is difficult to measure by conventional methods such as ionization chamber method and proportional counting method at the level below 0.1Bq / L (standard conditions). The liquid scintillation counting method has the advantages of low detection limit and low memory effect. According to the low-content tritiated hydrogen sample preparation device and method for liquid scintillation measurement of the present invention, gaseous HT is catalytically converted into HTO and collected by bubbling and cold trap methods. Combined with the measurement of low-background liquid scintillator, it can meet the measurement of low-activity content tritiated hydrogen (HT). This method can be expanded to the measurement of HT under conditions of medium and high concentrations and limited gas volume. The following introduces the present invention based on two application scenarios:

[0076] Example 1

[0077] The activity concentration of the existing tritium samples to be tested is about 10 -12 Ci / L level, this Example 1 uses a high temperature CuO catalyst combined with a cold trap collection method to obtain HTO samples. Specifically, Figure 1The sample supply module is installed in front of the first mass flow meter F1, the hydrogen and air supply modules are installed in front of the second mass flow meter F2 and the third mass flow meter F3 respectively, tritium-free water is added to the first bubbler 17, and the catalytic bed 21 is filled with CuO catalyst.

[0078] First, preheat the sampling device. Set the third mass flowmeter F3 to 1 L / min, open the third and fourth control valves, set the high-temperature furnace 22 to 800°C, and purge the catalyst bed for 2130 minutes. After preheating, close all control valves.

[0079] After that, the sample preparation and collection process is carried out. Open the first, second, third, fifth, and sixth control valves, set the first mass flow meter F1 to 10 ml / min, the second mass flow meter F2, and the third mass flow meter F3 to 200 ml / min, add 50-100 g of tritium-free water into the first bubbler 17, and install a cold trap collection bottle (such as Figure 3 As shown, the temperature of the catalyst bed 21 is set to 800°C, and the cold trap is controlled at -80°C using a liquid nitrogen-alcohol bath. A mixture of hydrogen and air, loaded with sufficient water vapor through the first bubbler 17, is evenly mixed with the sample to be tested in the mixing tube 15 and enters the catalyst bed 21 for hydrogen-oxygen complex conversion. The gas is collected by the cold trap at the outlet of the catalyst bed 21. After sample preparation is completed, all control valves are closed.

[0080] Finally, the device was cleaned by setting the third mass flow meter F3 to 1 L / min, opening the third and fourth control valves, setting the high-temperature furnace 22 to 800°C, and purging for 30 minutes; after the cleaning was complete, the device was shut down.

[0081] Specifically, the efficiency of hydrogen-oxygen recombination of the CuO catalytic bed 21 at 800° C. is 98%, and the water collection efficiency of the cold trap at -80° C. is 99%, and the amount of water collected by the cold trap is 4-5 g.

[0082] Specifically, the liquid scintillation instrument is LSC-B7 produced by Aloka Company, the liquid scintillation liquid is Ultima Gold μLLT, and the detection efficiency of 4 ml sample water + 16 ml liquid scintillation liquid is 24.5%.

[0083] In this embodiment, 300 ml of the tritium sample to be tested can be converted to an HTO activity concentration of 13.6 Bq / L (water sample). After conversion, the tritium activity concentration of the tritium sample to be tested is 5.0E-12 Ci / L.

[0084] Example 2

[0085] The activity concentration of the existing tritium samples to be tested is about 10 -11Ci / L level. In Example 2, a high temperature CuO catalyst was used in combination with a bubbling collection method to obtain HTO samples. Figure 1 The sample supply module is installed in front of the first mass flow meter F1, the hydrogen and air supply modules are installed in front of the second mass flow meter F2 and the third mass flow meter F3 respectively, tritium-free water is added to the second and third bubblers, and the catalytic bed 21 is filled with CuO catalyst.

[0086] First, preheat the sampling device. Set the third mass flowmeter F3 to 1 L / min, open the third and fourth control valves, set the high-temperature furnace 22 to 800°C, and purge for 30 minutes. After the preheating process is complete, close all control valves.

[0087] Afterwards, the sample preparation and collection process proceeds. Open the first, second, third, and fourth control valves. Set the first mass flowmeter F1 to 20 ml / min, the second mass flowmeter F2, and the third mass flowmeter F3 to 200 ml / min. Add 15 g of tritium-free water to the second and third bubblers. Connect the outlet of the catalyst bed 21 to the second and third bubblers, and set the temperature of the catalyst bed 21 to 800°C. Hydrogen, air, and the sample to be tested are evenly mixed in the mixing tube 15 and enter the catalyst bed 21 for hydrogen-oxygen complex conversion, where they are captured by the second and third bubblers at the outlet.

[0088] Finally, the device was cleaned by setting the third mass flow meter F3 to 1 L / min, opening the third and fourth control valves, setting the high-temperature furnace 22 to 800°C, and purging for 30 minutes; after the cleaning was complete, the device was shut down.

[0089] Specifically, at 800°C, the efficiency of the CuO catalytic bed 21 was 98%, the efficiency of the bubbling collection was 98%, and 15 g of tritium-free water was added to the second and third bubblers;

[0090] Specifically, the liquid scintillation instrument is LSC-B7 produced by Aloka Company, the liquid scintillation liquid is Ultima Gold μLLT, and the detection efficiency of 4 ml sample water + 16 ml liquid scintillation liquid is 24.5%.

[0091] In this embodiment, 300 ml of the tritium sample to be tested can be converted to an HTO activity concentration of 21.8 Bq / L (water sample). After conversion, the tritium activity concentration of the tritium sample to be tested is 3.0E-11 Ci / L.

[0092] From the above two embodiments, it can be seen that the present invention can measure tritiated hydrogen as low as 10-12Ci / L by catalytic conversion and liquid scintillation counting, which can achieve the measurement of low activity content tritiated hydrogen and solve the problem of measuring tritiated hydrogen at 10-12Ci / L. -12The present invention addresses the challenge of measuring tritiated hydrogen at low activity concentrations (Ci / L, standard conditions). This method is applicable to measurements of tritiated hydrogen ranging from low to medium-high activity concentrations. Furthermore, the measurement method provided by this invention exhibits a low memory effect, enabling measurement of tritiated hydrogen over a wide range. Furthermore, post-sampling cleaning effectively reduces cross-contamination of the device, ensuring measurement accuracy.

[0093] In summary, compared with the prior art, the tritiated hydrogen sample preparation device of the present invention combined with low-background liquid scintillation measurement has the following beneficial effects:

[0094] 1. By adding hydrogen, air, and water vapor, low-activity tritiated hydrogen (HT) is efficiently converted into tritiated water (HTO). This high conversion efficiency effectively addresses the difficulty in directly measuring gaseous tritium. Furthermore, the use of highly active hydrogen-oxygen composite catalysts (such as copper oxide and platinum supported on alumina) combined with precise temperature control in a high-temperature furnace ensures the efficiency and stability of the catalytic reaction.

[0095] 2. The present invention combines the low-background liquid scintillation counting method, and the detection limit can be as low as 0.5-1Bq / L, which can meet the measurement requirements of extremely low activity concentrations of tritiated hydrogen (such as 10-12Ci / L).

[0096] 3. By precisely controlling the gas flow, temperature and collection method, high-precision measurement of low-activity concentration tritiated hydrogen can be achieved. The liquid scintillation counting method is used, with a low detection limit and low memory effect, and the measurement results are more accurate and reliable.

[0097] 4. The present invention is not only applicable to the measurement of tritiated hydrogen with low activity concentration, but can also achieve a wide range of measurement from low to medium concentrations to higher concentrations by adjusting the sample amount and measurement time.

[0098] 5. The present invention is applicable to a variety of application scenarios, including environmental monitoring of nuclear facilities, measurement of tritium in reactor decommissioning waste, nuclear accident emergency monitoring, etc. It can meet the measurement needs of tritiated hydrogen in different concentration ranges, from extremely low concentrations (such as 10-12Ci / L) to medium and high concentrations.

[0099] 6. The present invention provides a variety of sample collection methods (such as the bubbling method and the cold trap method), and the appropriate collection device can be selected according to different measurement requirements and the activity range of tritium. It can efficiently collect the converted HTO samples and reduce sample loss and measurement errors.

[0100] 7. In addition, a cleaning process is set up after sampling to effectively remove residual tritium in the pipeline and catalytic bed, ensuring the accuracy and repeatability of the measurement.

[0101] 8. In addition, the sampling and measuring method and device of the present invention have a simple structure and low cost, and are suitable for wide promotion and application. During the measurement process, the safety of the operation is ensured by precisely controlling the reaction conditions and gas flow.

[0102] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A tritiated hydrogen sample preparation device for liquid scintillation measurement, characterized in that: include: The gas supply module is used to provide the tritiated hydrogen sample to be tested, hydrogen, air and water vapor, and adjust the flow rate of each gas through the corresponding mass flow meter and control valve; A catalytic oxidation module, used for catalytically converting tritiated hydrogen into tritiated water samples; The collection module is used to collect the converted tritiated water sample for the measurement of tritiated hydrogen content.

2. The tritiated hydrogen sample preparation device for liquid scintillation measurement according to claim 1, characterized in that: The gas supply module includes: a sample gas inlet unit, a hydrogen gas supply unit, an air gas supply unit, a water vapor supply unit, a gas mixing pipe, a first mass flow meter, a first control valve, a second mass flow meter, a second control valve, a third mass flow meter, a third control valve and a water vapor control valve group; The sample air intake unit is connected to the first mass flowmeter and the first control valve, the hydrogen supply unit is connected to the second mass flowmeter and the second control valve, the air supply unit is connected to the third mass flowmeter and the third control valve, and the water vapor supply unit is connected to the water vapor control valve group for adjusting the supply of water vapor; the sample air intake unit, the hydrogen supply unit, the air supply unit, and the water vapor supply unit are respectively controlled by the first control valve, the second control valve, the third control valve, and the water vapor control valve group to input the tritiated hydrogen sample to be measured, hydrogen, air, and water vapor into the mixing pipe, and then sent into the catalytic oxidation module for mixing.

3. The tritiated hydrogen sample preparation device for liquid scintillation measurement according to claim 2, characterized in that: The water vapor supply unit includes a first bubbler, and the water vapor control valve group includes a fourth control valve, a fifth control valve and a sixth control valve. The input end of the first bubbler is connected to one end of the third control valve and one end of the fourth control valve through the fifth control valve, and the output end of the first bubbler is connected to the other end of the fourth control valve, one end of the first control valve and the input end of the mixing pipe through the sixth control valve.

4. The tritiated hydrogen sample preparation device for liquid scintillation measurement according to claim 1, characterized in that: The catalytic oxidation module comprises: a catalytic bed filled with a hydrogen-oxygen composite catalyst; The temperature and heating rate of the high temperature furnace are controlled by an external programmable controller. The temperature range is 100-1000℃ and the heating rate is 10-100℃ / min.

5. The tritiated hydrogen sample preparation device for liquid scintillation measurement according to claim 1, characterized in that: The collection module includes: A bubbling collection device comprises a second bubbler and a third bubbler connected in series in two stages, wherein the second bubbler and the third bubbler are provided with 5-50 ml of tritium-free water; and / or, Cold trap collection device, the temperature of the cold trap collection device is controlled at 0℃ to -196℃.

6. A sample preparation and measurement method using the tritiated hydrogen sample preparation device according to claim 1, characterized in that: include: Air is introduced into the catalytic oxidation module, and the catalytic oxidation module is heated to a preset temperature for 10-60 minutes; The gas supply module provides the tritiated hydrogen sample to be tested, hydrogen, and air, which are mixed and then sent to the catalytic oxidation module. The catalytic oxidation module catalytically converts the tritiated hydrogen into a tritiated water sample, and the collection module collects the converted tritiated water sample. The collected tritiated water samples were mixed with liquid scintillator and placed in a low-background liquid scintillation instrument for measurement.

7. The sample preparation and measurement method according to claim 6, characterized in that: The collected tritiated water sample is mixed with liquid scintillator and then placed in a low-background liquid scintillation instrument for measurement, and the method also includes: Hydrogen, air and water vapor are introduced into the catalytic oxidation module and the collection module from the gas supply module to clean the catalytic oxidation module and the collection module to remove residual tritium in the gas supply pipeline and the catalytic oxidation module.

8. The sample preparation and measurement method according to claim 6, characterized in that: After the tritiated hydrogen sample to be measured, hydrogen, and air are provided and mixed by the gas supply module, the method further includes: The gas supply module provides water vapor, which is mixed with the tritiated hydrogen sample to be tested, hydrogen, and air.

9. The sample preparation and measurement method according to claim 6, characterized in that: The tritiated hydrogen sample to be tested, hydrogen, and air are provided by the gas supply module and mixed, and then sent to the catalytic oxidation module, the tritiated hydrogen is catalytically converted into a tritiated water sample by the catalytic oxidation module, and the converted tritiated water sample is collected by the collection module, further comprising: The gas supply module controls the flow rate of the tritiated hydrogen sample to be tested to 0-100 ml / min, the flow rate of hydrogen and air to 0-1 L / min, controls the temperature of the first bubbler to 25-80°C, and the temperature of the catalytic oxidation module to 100-800°C; The collection module collects tritiated water samples after conversion using a bubbling collection device and / or a low-temperature cold trap collection device.

10. The sample preparation and measurement method according to claim 7, characterized in that: The step of introducing hydrogen, air and water vapor from the gas supply module into the catalytic oxidation module and the collection module to clean the catalytic oxidation module and the collection module to remove residual tritiated hydrogen includes: The flow rates of hydrogen and air are controlled at 0-1 L / min by a first mass flow meter and a second mass flow meter respectively; the temperature of the first bubbler is controlled at 25-80° C. to provide water vapor; The hydrogen, air and water vapor are mixed and sent into the catalytic oxidation module and the collection module for cleaning for 10-60 minutes.

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