Online monitoring device and monitoring method for radionuclide in liquid with ultra-wide range

Abstract

The invention discloses an online monitoring device and monitoring method for radionuclides in a liquid with an ultra-wide range, and belongs to the technical field of radionuclide continuous measurement, the online monitoring device comprises a measurement sample chamber, the measurement sample chamber comprises a plurality of transparent sample pools, and scintillation crystal particles with different particle sizes are arranged in the sample pools; the liquid flow sensing and control module comprises a first liquid flow start-stop control switch and a first pipeline gating switch, and is arranged on the liquid inlet pipeline and the liquid outlet pipeline of each sample cell; and the photon detection module is attached to the pool wall of each sample pool. A plurality of sample cells are designed, and scintillation crystal particles with different particle sizes are arranged in different sample cells, so that different sample cells can measure the activity of radionuclides in to-be-measured liquid in different activity ranges, and the measurement range can be effectively widened while the measurement accuracy is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of continuous measurement of radioactive nuclides, and in particular to an online monitoring device and a monitoring method for radioactive nuclides in liquid with an ultra-wide measuring range. Background Art

[0002] During the operation of nuclear power plant reactors, deuterium-tritium fusion devices and other tritium-related nuclear facilities, liquid effluents containing tritium are inevitably produced. When the tritium concentration is low, the liquid scintillation method can be used for measurement, but when the tritium concentration is high (>1×105Bq / L), the liquid scintillation method will have too high a count rate, which greatly reduces the accuracy of the measurement results. In addition, the liquid scintillation method is an offline measurement, and the measurement process is time-consuming and cannot meet the requirements of continuous online monitoring.

[0003] In order to achieve continuous online monitoring of high concentrations of tritium in water, researchers at home and abroad have adopted a variety of technical routes and developed a variety of online monitoring methods for tritium in water, including BIXS (β-ray-induced X-rays), calorimetry, imaging plate method, and solid scintillation method. The measurement principle of the BIXS method is to use the electromagnetic interaction between low-energy β rays in water and materials to produce bremsstrahlung, which then deposits energy in the scintillator and generates photons, which are finally measured by photosensitive components. The advantage of this method is that it can achieve non-contact continuous monitoring of tritium water and will not cause pollution to tritium water. However, due to the extremely low energy of tritium decay electrons, the energy of the generated X-rays is also low, and there is a strong directionality, resulting in a high final detection limit of about 4×106Bq / L. The measurement principle of the calorimetric method is that the tritium decay electrons convert kinetic energy into heat energy in the sample chamber, and the activity of tritiated water is obtained by measuring the temperature change in the sample chamber. This method is the same as the BIXS method. Due to the extremely low energy of tritium decay electrons, the temperature change is not obvious when the activity of tritiated water is low, resulting in a higher detection limit of about 4×107Bq / L. The measurement principle of the imaging plate method is to place an imaging plate in the sample chamber, and the tritiated water vapor is in direct contact with the imaging plate. Tritium penetrates into the fluorescent material and causes it to emit photons. This method is slightly different from the previous two and belongs to contact measurement with tritiated water, but its detection limit is also not high, about 4×106Bq / L, and there is tritium contamination, which affects the accuracy of the measurement results. For the solid scintillation method, the measurement principle is to directly mix the solid scintillator with tritium water, and the tritium decay electrons deposit energy in the scintillator. Then the scintillator generates scintillation fluorescence after the deexcitation process, which is transmitted to the photosensitive components coupled to the scintillator, and converted into a current pulse signal through the photoelectric effect and recorded, and finally the tritium water activity is inferred through the pulse signal count rate. Based on the current advancement of photon detection technology, the solid scintillation method has shown great application potential in the continuous measurement of high-concentration tritium in water. In known research reports, solid scintillation materials include plastic scintillators, calcium fluoride inorganic scintillation crystals, etc., and scintillator structures include scintillation optical fibers, scintillation thin plates, and scintillation crystal particles. Although the solid scintillation method has good measurement capabilities in the continuous measurement of high-concentration tritium in water, there is still a problem of short tritium concentration range in water. Specifically, limited by the characteristics of the back-end photosensitive components, the range of the same tritium scintillation measurement sample chamber in water generally includes 4-5 concentration levels, which cannot meet the use requirements for scenes with large changes in tritium concentration in water. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of the prior art and to provide an online monitoring device and a monitoring method for radioactive nuclides in liquid with an ultra-wide measuring range.

[0005] The object of the present invention is to achieve the following technical solution: an online monitoring device for radioactive nuclides in liquid with an ultra-wide measuring range, the device comprising:

[0006] The measuring sample chamber includes a plurality of transparent sample pools, each of which is provided with scintillation crystal particles of different particle sizes;

[0007] A liquid flow sensing and control module, comprising a first liquid flow start-stop control switch and a first pipeline selection switch, wherein the first liquid flow start-stop control switch and the first pipeline selection switch are arranged on the liquid inlet pipeline of each sample pool, or the first liquid flow start-stop control switch and the first pipeline selection switch are arranged on the liquid inlet pipeline and the liquid outlet pipeline of each sample pool;

[0008] The photon detection module is arranged to fit the wall of each sample pool.

[0009] In one example, the scintillation crystal particles are calcium fluoride crystal particles that have been spheroidized by high temperature plasma spheroidization technology.

[0010] In one example, the measurement sample chamber includes a first sample pool, a second sample pool and a third sample pool. The particle size range of the scintillation crystal particles in the first sample pool is 30, the particle size range of the scintillation crystal particles in the second sample pool is 200, and the particle size range of the scintillation crystal particles in the third sample pool is 800.

[0011] In one example, the liquid flow sensing and control module further includes a control unit, which is connected to a first liquid flow start-stop control switch and a first pipeline selection switch.

[0012] In one example, the liquid flow sensing and control module further includes a liquid level acquisition unit connected to the control unit, which is disposed on the liquid inlet pipeline of each sample pool, or on the liquid inlet pipeline and liquid outlet pipeline of each sample pool.

[0013] In one example, the device further includes a preselected pipeline set at the liquid inlet end, and the liquid flow sensing and control module further includes a peristaltic pump;

[0014] The preselected pipeline group at the liquid inlet end includes a measuring pipeline, a cleaning pipeline, and a drying pipeline. The measuring pipeline, the cleaning pipeline, and the drying pipeline are connected to the liquid inlet pipelines of the first sample pool, the second sample pool, and the third sample pool via a peristaltic pump and a second pipeline selection switch in sequence. A second liquid flow start and stop control switch is respectively provided on the pipeline between the peristaltic pump and the second pipeline selection switch.

[0015] In one example, the device further includes an industrial computer, which is connected to the photon detection module.

[0016] In one example, the device further includes a shielding shell, in which the measurement sample chamber and the photon detection module are disposed.

[0017] It should be further explained that the technical features corresponding to the above-mentioned device examples can be combined or replaced with each other to form a new technical solution.

[0018] The present invention provides an online monitoring method for radioactive nuclides in liquid with an ultra-wide measurement range, which has the same inventive concept as the above-mentioned online monitoring device, and the method comprises the following steps:

[0019] Counting the current pulse signal output by the photon detection module, and calculating the activity of the radioactive nuclide in the liquid according to the counting rate of the current pulse signal;

[0020] According to the activity of radionuclides, sample pools with different particle size ranges are selected for online monitoring of radionuclides:

[0021] If the activity of the radioactive nuclide gradually increases, the radioactive nuclide liquid to be measured is passed into the sample pool of the smallest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool of the smallest particle size range is reached, the radioactive nuclide liquid to be measured is passed into the next sample pool of the particle size range larger than the smallest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the next sample pool of the particle size range larger than the smallest particle size range is reached, the radioactive nuclide liquid to be measured is continued to be passed into the sample pool of the larger particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline until the measuring range of the sample pool of the largest particle size range is reached, and the measurement is stopped;

[0022] If the activity of the radioactive nuclide gradually decreases, first pass the radioactive nuclide liquid to be measured into the sample pool with the largest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool with the largest particle size range is reached, pass the radioactive nuclide liquid to be measured into the next sample pool with a particle size range smaller than the maximum particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the next sample pool with a particle size range smaller than the maximum particle size range is reached, pass the radioactive nuclide liquid to be measured into the sample pool with a smaller particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline until the measuring range of the sample pool with the smallest particle size range is reached, and the measurement is stopped;

[0023] If the activity of the radionuclide changes randomly, the radionuclide liquid to be tested is randomly introduced into a sample pool through the inlet pipeline or the switches on the inlet pipeline and the outlet pipeline. If the activity of the radionuclide continues to increase and reaches the measurement range of the random sample pool, the radionuclide liquid to be tested is introduced into a sample pool with a larger particle size through the switches on the inlet pipeline and the outlet pipeline. If the activity of the radionuclide in the sample pool with a larger particle size range decreases and reaches the measurement range of the sample pool with a larger particle size range, the radionuclide liquid to be tested is randomly introduced into a sample pool through the inlet pipeline or the switches on the inlet pipeline and the outlet pipeline. The switch on the liquid passes the radioactive nuclide liquid to be tested into a sample pool with a smaller particle size; if the concentration of the radioactive nuclide liquid to be tested passed into the random sample pool continues to decrease and reaches the measurement range of the random sample pool, the switch on the liquid inlet pipeline and the liquid outlet pipeline is used to pass the radioactive nuclide liquid to be tested into a sample pool with a smaller particle size range; if the activity of the radioactive nuclide increases and reaches the measurement range of the sample pool with a smaller particle size range, the radioactive nuclide liquid to be tested is passed into a sample chamber with a larger particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline.

[0024] In one example, the method includes the following steps:

[0025] Counting the current pulse signal output by the photon detection module, and calculating the activity of the radioactive nuclide in the liquid according to the counting rate of the current pulse signal;

[0026] According to the activity of radionuclides, sample pools with different particle size ranges are selected for online monitoring of radionuclides:

[0027] If the activity of the radioactive nuclide gradually increases, the liquid of the radioactive nuclide to be measured is passed into the sample pool of the smallest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool of the smallest particle size range is reached, the liquid of the radioactive nuclide to be measured is passed into the sample pool of the moderate particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool of the moderate particle size range is reached, the liquid of the radioactive nuclide to be measured is passed into the sample pool of the largest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool of the largest particle size range is reached, the measurement is stopped;

[0028] If the activity of the radionuclide gradually decreases, first pass the radionuclide liquid to be measured into the sample pool of the largest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool of the largest particle size range is reached, pass the radionuclide liquid to be measured into the sample pool of the moderate particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline, or pass the radionuclide liquid to be measured into the sample pool of the moderate particle size range and the maximum particle size range at the same time. If the measuring range of the sample pool of the moderate particle size range is reached, pass the radionuclide liquid to be measured into the sample pool of the smallest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline, or pass the radionuclide liquid to be measured into the sample pool of the smallest particle size range, the moderate particle size range and the maximum particle size range at the same time. If the measuring range of the sample pool of the smallest particle size range is reached, stop the measurement;

[0029] If the activity of the radionuclide changes randomly, the liquid of the radionuclide to be measured is passed into the sample pool with an appropriate particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the activity of the radionuclide continues to increase and reaches the measurement range of the sample pool with an appropriate particle size range, the liquid of the radionuclide to be measured is passed into the sample pool with the largest particle size range through the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the activity of the radionuclide decreases and reaches the measurement range of the sample pool with the largest particle size range, the liquid of the radionuclide to be measured is passed into the sample pool with the largest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. The radioactive nuclide liquid is passed into the sample chamber with a moderate particle size range; if the concentration of the radioactive nuclide liquid to be tested in the sample pool with a moderate particle size range continues to decrease and reaches the measuring range of the sample pool with a moderate particle size range, the radioactive nuclide liquid to be tested is passed into the sample pool with the smallest particle size range through the switches on the liquid inlet pipeline and the liquid outlet pipeline; if the activity of the radioactive nuclide increases and reaches the measuring range of the sample pool with the smallest particle size range, the radioactive nuclide liquid to be tested is passed into the sample chamber with a moderate particle size range through the liquid inlet pipeline or the switches on the liquid inlet pipeline and the liquid outlet pipeline.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. In one example, by designing multiple sample pools, and scintillation crystal particles with different particle sizes are arranged in different sample pools, different sample pools can be used to measure the activity of radionuclides in the liquid to be tested with different activity ranges, which can effectively broaden the measurement range while ensuring the measurement accuracy.

[0032] 2. In one example, the calcium fluoride crystal particles are spheroidized using vacuum plasma spheroidization technology, which can effectively improve the microscopic morphology (surface roughness) of the particles, obtain better sphericity, and significantly improve the liquid flow characteristics in the stacking state of the calcium fluoride crystal particles, thereby avoiding the problem of reduced measurement accuracy due to uneven liquid flow, thereby improving the measurement accuracy; at the same time, the calcium fluoride crystal particles with better sphericity can improve the tritium residual contamination phenomenon on the surface of existing rough particles, further improving the measurement accuracy.

[0033] 3. In one example, the use of the sample chamber is dynamically adjusted according to the change in the activity of the radionuclide. When the activity increases or decreases to the limit value of the current sample chamber, the measurement is continued by switching to another sample chamber, thereby ensuring the continuity and accuracy of the measurement. At the same time, when the activity measurement range of a single sample chamber is insufficient to cover the measurement range, the current pulse signal count rate can be increased by using multiple sample chambers for measurement at the same time, thereby widening the measurement range and ensuring the accuracy of the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The specific implementation methods of the present invention are further described in detail below in conjunction with the accompanying drawings. The accompanying drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The same reference numerals are used in these drawings to represent the same or similar parts. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0035] Figure 1 A device block diagram provided for an example of the present invention;

[0036] Figure 2 Schematic diagram of the microscopic morphology of calcium fluoride particles without spheroidization treatment;

[0037] Figure 3 A device block diagram is provided for a preferred example of the present invention. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. 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.

[0039] In the description of the present invention, it should be noted that the directions or positional relationships indicated by "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are directions or positional relationships based on the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the use of ordinal numbers (e.g., "first and second", "first to fourth", etc.) is to distinguish objects, and is not limited to this order, and cannot be understood as indicating or implying relative importance.

[0040] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] In one example, an online monitoring device for radioactive nuclides in liquid with an ultra-wide measurement range is described in detail using the online monitoring of high concentrations of tritium in water as an example. Of course, other radioactive nuclides can also be measured, such as the radioactivity of all alpha particles and beta particles in liquid. In this example, the online monitoring device includes a measurement sample chamber, a liquid flow sensing and control module, and a photon detection module.

[0043] Specifically, the measurement sample chamber includes a plurality of transparent sample cells, such as sample cells made of quartz glass (quartz glass tubes), such as Figure 1 As shown, the measurement sample chamber in this example includes three sample pools, namely, quartz glass tube A (first sample pool), quartz glass tube B (second sample pool), and quartz glass tube C (third sample pool). Of course, fewer or more sample pools can also be set, depending on the actual needs of the online monitoring scenario. Furthermore, each sample pool is provided with scintillation crystal particles of different particle sizes, and the particle size of the scintillation crystal particles in each sample pool can be adaptively adjusted according to the measurement requirements. The scintillation crystal particles can be plastic scintillation particles, calcium fluoride inorganic scintillation crystal particles, etc., preferably calcium fluoride crystal particles, which have good performance, low processing difficulty, low cost, simple assembly method, and show good detection capabilities of high-concentration tritium in water.

[0044] Furthermore, the liquid flow sensing and control module includes a first liquid flow start-stop control switch and a first pipeline selection switch. The first liquid flow start-stop control switch is used to control the flow or shutoff of liquid in the pipeline, that is, to open / close the corresponding liquid circuit, and may be a solenoid valve, a ball valve, etc. The first pipeline selection switch is used to switch and select different pipelines, and may be a diverter, a two-way valve, a three-way valve, a multi-way valve, etc. The first liquid flow start-stop control switch and the first pipeline selection switch are arranged on the liquid inlet pipeline, or the liquid inlet pipeline and the liquid outlet pipeline of each sample pool. Preferably, the liquid inlet pipeline and the liquid outlet pipeline of each sample pool are provided with the first liquid flow start-stop control switch and the first pipeline selection switch, such as Figure 1 As shown, the liquid inlet pipeline of quartz glass tube A is provided with three-way valve 3WV2 and electromagnetic valve YV4 in sequence, the liquid inlet pipeline of quartz glass tube B is provided with three-way valve 3WV3 and electromagnetic valve YV5 in sequence, the liquid inlet pipeline of quartz glass tube C is provided with two-way valve TWV1 and electromagnetic valve YV6 in sequence; the liquid outlet pipeline of quartz glass tube A is provided with electromagnetic valve YV7 and two-way valve TWV2 in sequence, the liquid outlet pipeline of quartz glass tube B is provided with electromagnetic valve YV8 and two-way valve 3WV4 in sequence, and the liquid outlet pipeline of quartz glass tube C is provided with electromagnetic valve YV9 and two-way valve 3WV5 in sequence. Through the coordinated work of electromagnetic valves, two-way valves and three-way valves, the tritium water to be tested can be passed into different sample chambers.

[0045] Furthermore, the photon detection module is used to receive the scintillation fluorescence generated by the scintillation crystal particles and the liquid to be tested, and can be a photomultiplier tube (PMT), a single photon detector, etc., preferably a 2-inch PMT with a voltage divider, which outputs a single photon pulse under the high-voltage power supply of the SHV connector to achieve scintillation photon detection of the fluid. In this example, the photosensitive surface of the PMT is supported by elastic damping, and flexibly and tightly fits the side wall of the sample cell to obtain scintillation fluorescence.

[0046] Preferably, the device also includes an industrial computer, which is connected to the photon detection module and is used to receive the current pulse signal sent by the photon detection module, count the current pulse signal, and inversely infer the tritium water activity through the pulse signal counting rate.

[0047] In this example, multiple sample pools are designed, and scintillation crystal particles with different particle sizes are arranged in different sample pools, so that different sample pools can measure the activity of radionuclides in the liquid to be tested with different activity ranges, which can effectively broaden the measurement range while ensuring the measurement accuracy.

[0048] Calcium fluoride particles are usually obtained by single crystal grinding. The particles have irregular morphology and high surface roughness, such as Figure 2As shown. During the measurement process, particles accumulate inside the sample chamber, and tritium water flows through the gaps between the particles. At this time, the irregular morphology of the particles will affect the fluidity of the liquid, causing the liquid to flow unevenly in the sample chamber, affecting the accuracy of the measurement results. In addition, the rough surface of the particles will cause residual contamination of tritium water on the surface of the particles, further affecting the measurement results. To solve this problem, in one example, high-temperature plasma spheroidization technology is used to spheroidize calcium fluoride crystal particles. Specifically, the calcium fluoride single crystal is first ground, and then the ground particles are spheroidized using vacuum plasma spheroidization technology to ensure that the calcium fluoride particles are not disturbed by impurity gases during the spheroidization process, while obtaining better sphericity, and finally a sieve is used to obtain spherical calcium fluoride particles with different particle size distributions.

[0049] In this example, the microscopic morphology of calcium fluoride particles was first improved through high-temperature plasma spheroidization technology, which significantly enhanced the liquid flow characteristics in the particle accumulation state and improved the tritium residual contamination on the particle surface. Subsequently, by adjusting the particle size, sample chambers for tritium scintillation measurement in water with different ranges were designed, and they were combined and applied in the form of sample chamber arrays to achieve continuous measurement of high-concentration tritium in water over an ultra-wide range.

[0050] In one example, the measurement sample chamber includes a first sample pool, a second sample pool and a third sample pool. The particle size range of the scintillation crystal particles in the first sample pool is 30μm-200μm, preferably 50μm, and the first sample chamber is a high-sensitivity sample chamber; the particle size range of the scintillation crystal particles in the second sample pool is 200μm-800μm, preferably 300μm, and the third sample chamber is a medium-sensitivity sample; the particle size range of the scintillation crystal particles in the third sample pool is 800μm-1200μm, preferably 1000μm, and the third sample chamber is a low-sensitivity sample.

[0051] In one example, the liquid flow sensing and control module further includes a control unit, which is connected to a first liquid flow start-stop control switch (such as a solenoid valve), a first pipeline selection switch, and an industrial computer, wherein the industrial computer is integrated with a display and a human-machine display interface. Figure 3 As shown, the device includes a multifunctional data acquisition and control board, in which a control unit is provided. Switches such as solenoid valves and three-way valves are connected to a solenoid valve control subunit via a valve cable interface and a multi-core cable. The solenoid valve control subunit is connected to the control unit, and switches such as liquid solenoid valves are automatically controlled by the control unit.

[0052] In one example, the liquid flow sensing and control module further includes a liquid level acquisition unit connected to the control unit, which is arranged on the liquid inlet pipeline of each sample pool, or on the liquid inlet pipeline and liquid outlet pipeline of each sample pool. The liquid level acquisition unit may be a liquid level sensor. Figure 3As shown, a liquid level sensor LT1 is provided on the liquid inlet pipeline of the first sample chamber, a liquid level sensor LT2 is provided on the liquid inlet pipeline of the second sample chamber, a liquid level sensor LT3 is provided on the liquid inlet pipeline of the third sample chamber, a liquid level sensor LT4 is provided on the liquid outlet pipeline of the first sample chamber, a liquid level sensor LT5 is provided on the liquid outlet pipeline of the second sample chamber, and a liquid level sensor LT6 is provided on the liquid outlet pipeline of the third sample chamber. Each liquid level sensor is connected to a liquid level sensor state reading subunit via a cable interface and a multi-core cable, and the liquid level sensor state reading subunit is connected to a control unit, so that the control unit obtains real-time liquid storage level information of each sample chamber, controls switches such as solenoid valves to open or close corresponding pipelines, and thus realizes automatic control.

[0053] In one example, the device further includes a preselected pipeline group at the liquid inlet end, and the liquid flow sensing and control module further includes a peristaltic pump; Figure 3 As shown, the preselected pipeline group at the liquid inlet end includes a measuring pipeline, a cleaning pipeline, and a drying pipeline. The measuring pipeline, the cleaning pipeline, and the drying pipeline are connected to the liquid inlet pipelines of the first sample cell, the second sample cell, and the third sample cell via a peristaltic pump and a second pipeline selection switch in sequence. A second liquid flow start-stop control switch is provided on the pipeline between the peristaltic pump and the second pipeline selection switch. The second liquid flow start-stop control switch is used to control the flow or shutoff of the liquid in the pipeline, and may be a solenoid valve, a ball valve, etc. The second pipeline selection switch is used to switch and select different pipelines, specifically selecting the measuring pipeline or the cleaning pipeline or the drying pipeline to be connected to the liquid inlet pipeline of the sample chamber, and may be a 1-to-3 diverter or a three-way valve, etc., such as Figure 3 As shown, the second pipeline selection switch in this example is a three-way valve 3WV1, a solenoid valve YV1 is provided on the measuring pipeline between the three-way valve 3WV1 and the peristaltic pump, a solenoid valve YV2 is provided on the cleaning pipeline between the three-way valve 3WV1 and the peristaltic pump, and a solenoid valve YV3 is provided on the drying pipeline between the three-way valve 3WV1 and the peristaltic pump. The three-way valve and the three solenoid valves cooperate with the three-way valves and solenoid valves of the liquid inlet pipelines of each sample chamber to realize the selective connection between the measuring pipeline, the cleaning pipeline, the drying pipeline and the liquid inlet pipeline of each sample chamber.

[0054] Specifically, the sources of the fluids of the present invention are the incoming flow to be measured (tritium water to be measured), the cleaning fluid, and the drying gas. The incoming flow to be measured flows to the measuring pipeline, the cleaning fluid flows to the cleaning pipeline, and the drying gas flows to the drying pipeline. The incoming flow to be measured, the cleaning fluid, and the drying gas are driven by the peristaltic pump to form a flow capacity and flow to the subsequent circuit; after the three fluids pass through the solenoid valve (YV1 or YV2 or YV3), they are combined into one path through the three-way valve 3WV1 and flow to the subsequent stage. In principle, only one of the three fluids will be opened (the other two are in a closed state), thereby forming different functions. When the incoming flow to be measured is opened, the normal test function is to fill the sample pool with liquid, and the photon detector is linked to count scintillation photons and judge the intensity; when the cleaning fluid is opened, the sample pool is cleaned with liquid, the tritium-containing liquid therein is discharged, and the sample chamber count is restored to the background state; when the drying gas is opened, all liquids in the pipeline are discharged and fully dried, which is equivalent to completely initializing the entire device.

[0055] Furthermore, the fluid flows through the three-way valve 3WV1 and enters the sample pool. The three glass sample pools are each equipped with an independent solenoid valve and a liquid level sensor, which realizes the complete independent control of the fluid in the sample pool. The functions include: (1) Adding liquid: Open the solenoid valve of the corresponding channel, pump in the flow to be measured, and observe the state of the liquid level sensor. When the two liquid level sensors on the inlet and outlet pipelines are both in state 1, it means that the sample pool is full of cleaning fluid. Maintain this state, and combine the signal response of the photon detector (for example, the count rate decreases) to judge the cleaning effect and stop time. (3) Drying: Open the solenoid valve of the corresponding channel, pump in dry gas, and when the two liquid level sensors on the inlet and outlet pipelines are both in state 0, it means that the sample pool is empty. Maintain this state, and combine the signal response of the photon detector (for example, the count rate decreases) to judge the emptying effect and stop time. (4) Range switching: According to the actual working conditions, when the activity of tritiated water gradually increases during the measurement process, the high-sensitivity first sample chamber (filled with 50μm particle size particles) is first introduced. When the counting rate gradually increases and approaches the limit value (about to exceed the range), the injection is stopped, and the sample chamber is treated by cleaning and drying. Then, the liquid is introduced into the next sensitive sample chamber (filled with 300μm particle size particles) by controlling the solenoid valve until the total measurement range of the device is exceeded. It should be noted that the next sensitive sample chamber of the first sample chamber is the second sample chamber, and the next sensitive sample chamber of the second sample chamber is the third sample chamber. When the activity of tritiated water gradually decreases during the measurement process, the low-sensitivity third sample chamber is first introduced. When the counting rate gradually decreases to the limit value, the sample is simultaneously introduced into the next sensitive sample chamber, that is, the two sample chambers are simultaneously measured. By analogy, when the counting rate further decreases, the three sample chambers are simultaneously measured until the sample activity exceeds the total measurement range of the device. When the activity of tritium water changes randomly during the measurement process, it is first passed into the first sample chamber with high sensitivity. According to the trend of the counting rate change, if the counting rate rises to the limit, the sample chamber is cleaned and then passed into the sample chamber with the next sensitivity. If the counting rate drops to the limit, the sample is simultaneously passed into the sample chamber with the next sensitivity. The two sample chambers are used simultaneously, and the subsequent work logic is similar.

[0056] In one example, the device further includes a shielding shell, and the measuring sample chamber and the photon detection module are disposed in the shielding shell. Optionally, the liquid level sensor may also be disposed in the shielding shell. In this example, low-background lead is used to realize the shielding of the device, the sample pool and part of the liquid path are shielded, and the internal electronic components are interfaced through cables, and are connected, driven and program-controlled by the electronic control subunit.

[0057] Optionally, the device also includes an overall packaging shell, and the device as a whole is split and packaged into two parts. The first part is the sample pool, photon detection module and pipeline part, and the second part is the liquid flow sensing and control module. The two are connected by an interface + cable to achieve one-to-one function definition and program control.

[0058] Combining the above examples, we can get Figure 3 The preferred device shown in the figure includes a measuring sample chamber, a liquid flow sensing and control module, a photon detection module and an industrial computer. The measuring sample chamber includes three sample pools, and the three sample pools are provided with calcium fluoride crystal particles that have been spheroidized by high-temperature plasma spheroidization technology. The particle size of the calcium fluoride crystal particles in the first sample pool is 50 μm, the particle size of the calcium fluoride crystal particles in the second sample pool is 300 μm, and the particle size of the calcium fluoride crystal particles in the third sample pool is 1000 μm; the liquid flow sensing and control module includes a control unit, solenoid valves and three-way valves, liquid level sensors and peristaltic pumps. The solenoid valves and three-way valves, and liquid level sensors are arranged on the liquid inlet and outlet pipelines of the three sample pools, and the preselected pipeline group at the liquid inlet end is also provided with solenoid valves and three-way valves, and peristaltic pumps.

[0059] In this preferred example, by spheroidizing the calcium fluoride crystal particles, the flow characteristics of the liquid in the particle accumulation state and the problem of residual tritium contamination on the particle surface can be effectively improved. At the same time, by preparing spherical calcium fluoride particles of different particle sizes and assembling them with sample pools, sample chambers with different ranges for continuous measurement of high concentrations in water are obtained, and by combining sample chambers with different ranges, a sample chamber array with ultra-wide range of continuous measurement of high concentrations of tritium in water is obtained, with a range of 1×10 4 Bq / L—1×10 15 Bq / L. Furthermore, by setting up 3-way sample injection pipelines, the tritium water measurement and cleaning and drying processing functions are realized, and there is no need to frequently replace the sample chamber due to tritium residual contamination, thus realizing continuous online monitoring of tritium activity. In addition, through the injection control logic of sample chambers with different ranges, effective connection of different ranges is realized.

[0060] In one example, the present invention also includes a method for online monitoring of radionuclides in liquid with an ultra-wide measurement range, the method comprising the following steps:

[0061] S1: Counting the current pulse signal output by the photon detection module, and calculating the activity of the radioactive nuclide in the liquid according to the counting rate of the current pulse signal;

[0062] S2: According to the activity of radionuclides, select sample pools with different particle size ranges for online monitoring of radionuclides:

[0063] If the activity of the radioactive nuclide gradually increases, the radioactive nuclide liquid to be measured is passed into the sample pool of the smallest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool of the smallest particle size range is reached, the radioactive nuclide liquid to be measured is passed into the next sample pool of the particle size range larger than the smallest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the next sample pool of the particle size range larger than the smallest particle size range is reached, the radioactive nuclide liquid to be measured is continued to be passed into the sample pool of the larger particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline until the measuring range of the sample pool of the largest particle size range is reached, and the measurement is stopped;

[0064] If the activity of the radioactive nuclide gradually decreases, first pass the radioactive nuclide liquid to be measured into the sample pool with the largest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool with the largest particle size range is reached, pass the radioactive nuclide liquid to be measured into the next sample pool with a particle size range smaller than the maximum particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the next sample pool with a particle size range smaller than the maximum particle size range is reached, pass the radioactive nuclide liquid to be measured into the sample pool with a smaller particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline until the measuring range of the sample pool with the smallest particle size range is reached, and the measurement is stopped;

[0065] If the activity of the radionuclide changes randomly, the radionuclide liquid to be tested is randomly introduced into a sample pool through the inlet pipeline or the switches on the inlet pipeline and the outlet pipeline. If the activity of the radionuclide continues to increase and reaches the measurement range of the random sample pool, the radionuclide liquid to be tested is introduced into a sample pool with a larger particle size through the switches on the inlet pipeline and the outlet pipeline. If the activity of the radionuclide in the sample pool with a larger particle size range decreases and reaches the measurement range of the sample pool with a larger particle size range, the radionuclide liquid to be tested is randomly introduced into a sample pool through the inlet pipeline or the switches on the inlet pipeline and the outlet pipeline. The switch on the liquid passes the radioactive nuclide liquid to be tested into a sample pool with a smaller particle size; if the concentration of the radioactive nuclide liquid to be tested passed into the random sample pool continues to decrease and reaches the measurement range of the random sample pool, the switch on the liquid inlet pipeline and the liquid outlet pipeline is used to pass the radioactive nuclide liquid to be tested into a sample pool with a smaller particle size range; if the activity of the radioactive nuclide increases and reaches the measurement range of the sample pool with a smaller particle size range, the radioactive nuclide liquid to be tested is passed into a sample chamber with a larger particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline.

[0066] Specifically, take the measurement sample chamber including three sample pools as an example for explanation, the three sample pools are respectively the first sample pool, the second sample pool and the third sample pool, the particle size range of the scintillation crystal particles in the first sample pool (the sample pool with the smallest particle size range) is 30% of the particle size of the scintillation crystal particles, and it is a high-sensitivity sample pool; the particle size range of the scintillation crystal particles in the second sample pool (the sample pool with a moderate particle size range) is 200% of the particle size range of the crystal particles, and it is a medium-sensitivity sample pool; the particle size range of the scintillation crystal particles in the third sample pool (the sample pool with the largest particle size range) is 800% of the particle size range of the crystal particles, and it is a low-sensitivity sample pool.

[0067] If the activity of the detritiated water gradually increases, the incoming flow to be measured is introduced into the high-sensitivity sample cell, specifically through the corresponding sample cell inlet pipeline or the switches on the inlet pipeline and the outlet pipeline (the first liquid flow start-stop control switch and the first pipeline selection switch) to introduce the incoming flow to be measured into the corresponding sample cell, which will not be repeated below; if the measurement range of the high-sensitivity sample cell is reached, the incoming flow to be measured is introduced into the medium-sensitivity sample cell, if the measurement range of the second sample cell is reached, the incoming flow to be measured is introduced into the low-sensitivity sample cell, and if the measurement range of the low-sensitivity sample cell is reached, the measurement is stopped;

[0068] If the activity of the detritiated water gradually decreases, the incoming flow to be measured is passed into the low-sensitivity sample cell. If the measurement range of the low-sensitivity sample cell is reached, the incoming flow to be measured is passed into the medium-sensitivity sample cell. Preferably, the incoming flow to be measured is passed into the medium-sensitivity sample cell and the low-sensitivity sample cell at the same time. If the measurement range of the medium-sensitivity sample cell is reached, the incoming flow to be measured is passed into the high-sensitivity sample cell. The incoming flow to be measured can also be passed into the high-sensitivity sample chamber, the medium-sensitivity sample chamber and the low-sensitivity sample cell at the same time. If the measurement range of the high-sensitivity sample cell is reached, the measurement is stopped.

[0069] If the activity of the radionuclide changes randomly, the liquid of the radionuclide to be tested is passed into the medium-sensitivity sample pool through the liquid inlet pipeline or the switches on the liquid inlet pipeline and the liquid outlet pipeline. If the activity of the radionuclide continues to increase and reaches the measurement range of the medium-sensitivity sample pool, the liquid of the radionuclide to be tested is passed into the low-sensitivity sample pool through the switches on the liquid inlet pipeline and the liquid outlet pipeline. If the activity of the radionuclide decreases and reaches the measurement range of the low-sensitivity sample pool, the liquid of the radionuclide to be tested is passed into the low-sensitivity sample pool through the liquid inlet pipeline or the switches on the liquid inlet pipeline and the liquid outlet pipeline. The radioactive nuclide liquid to be measured is introduced into a sample chamber with a moderate particle size range; if the concentration of the radioactive nuclide liquid to be measured randomly introduced into the medium-sensitivity sample cell continues to decrease and reaches the measuring range of the medium-sensitivity sample cell, the radioactive nuclide liquid to be measured is introduced into the high-sensitivity sample cell through the switches on the inlet and outlet pipes; if the activity of the radioactive nuclide increases and reaches the measuring range of the high-sensitivity sample cell, the radioactive nuclide liquid to be measured is introduced into the medium-sensitivity sample chamber through the inlet pipe or the switches on the inlet and outlet pipes.

[0070] Optionally, if the activity of tritiated water changes randomly, the tritiated water is passed into a high-sensitivity sample cell; if the activity of tritiated water continues to increase and reaches the measurement range of the high-sensitivity sample cell, the tritiated water is passed into a medium-sensitivity sample cell; if the activity of tritiated water decreases and reaches the measurement range of the medium-sensitivity sample cell, the tritiated water is passed into the high-sensitivity sample chamber and the medium-sensitivity sample cell at the same time, or the tritiated water is passed into the high-sensitivity sample chamber, the medium-sensitivity sample chamber, and the low-sensitivity sample cell at the same time.

[0071] The present invention prepares spherical calcium fluoride crystal particles with different particle sizes, effectively improving the flow characteristics of the liquid in the particle accumulation state and the problem of residual tritium contamination on the particle surface, and realizes ultra-wide range continuous measurement of high-activity tritium in water by designing sample chambers for continuous measurement of tritium in water with different ranges, combined with sampling control and cleaning and drying functions.

[0072] The above specific implementation methods are detailed descriptions of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. An online monitoring device for radioactive nuclides in liquid with an ultra-wide measurement range, characterized in that: include: The measuring sample chamber includes a plurality of transparent sample pools, each of which is provided with scintillation crystal particles of different particle sizes; A liquid flow sensing and control module, comprising a first liquid flow start-stop control switch and a first pipeline selection switch, wherein the first liquid flow start-stop control switch and the first pipeline selection switch are arranged on the liquid inlet pipeline of each sample pool, or the first liquid flow start-stop control switch and the first pipeline selection switch are arranged on the liquid inlet pipeline and the liquid outlet pipeline of each sample pool; The photon detection module is arranged to fit the wall of each sample pool.

2. The on-line monitoring device for radioactive nuclides in liquid with an ultra-wide measurement range according to claim 1, characterized in that: The scintillation crystal particles are calcium fluoride crystal particles that have been spheroidized by high-temperature plasma spheroidization technology.

3. The on-line monitoring device for radioactive nuclides in liquid with an ultra-wide measurement range according to claim 1, characterized in that: The measurement sample chamber comprises a first sample pool, a second sample pool and a third sample pool. The particle size range of the scintillation crystal particles in the first sample pool is 30 μm-200 μm, the particle size range of the scintillation crystal particles in the second sample pool is 200 μm-800 μm, and the particle size range of the scintillation crystal particles in the third sample pool is 800 μm-1200 μm.

4. The on-line monitoring device for radioactive nuclides in liquid with an ultra-wide measurement range according to claim 3, characterized in that: The liquid flow sensing and control module also includes a control unit, which is connected to the first liquid flow start-stop control switch and the first pipeline selection switch.

5. The on-line monitoring device for radioactive nuclides in liquid with an ultra-wide measurement range according to claim 4, characterized in that: The liquid flow sensing and control module also includes a liquid level acquisition unit connected to the control unit, which is arranged on the liquid inlet pipeline of each sample pool, or on the liquid inlet pipeline and liquid outlet pipeline of each sample pool.

6. The on-line monitoring device for radioactive nuclides in liquid with an ultra-wide measurement range according to claim 4, characterized in that: The device also includes a preselected pipeline group at the liquid inlet end, and the liquid flow sensing and control module also includes a peristaltic pump; The preselected pipeline group at the liquid inlet end includes a measuring pipeline, a cleaning pipeline, and a drying pipeline. The measuring pipeline, the cleaning pipeline, and the drying pipeline are connected to the liquid inlet pipelines of the first sample pool, the second sample pool, and the third sample pool via a peristaltic pump and a second pipeline selection switch in sequence. A second liquid flow start and stop control switch is respectively provided on the pipeline between the peristaltic pump and the second pipeline selection switch.

7. The on-line monitoring device for radioactive nuclides in liquid with an ultra-wide measurement range according to claim 1, characterized in that: The device also includes an industrial computer, which is connected to the photon detection module.

8. The on-line monitoring device for radioactive nuclides in liquid with an ultra-wide measurement range according to claim 1, characterized in that: The device also includes a shielding shell, in which the measuring sample chamber and the photon detection module are arranged.

9. A method for online monitoring of radionuclides in liquid with an ultra-wide measurement range, characterized in that: The method comprises the following steps: Counting the current pulse signal output by the photon detection module, and calculating the activity of the radioactive nuclide in the liquid according to the counting rate of the current pulse signal; According to the activity of radionuclides, sample pools with different particle size ranges are selected for online monitoring of radionuclides: If the activity of the radioactive nuclide gradually increases, the radioactive nuclide liquid to be measured is passed into the sample pool of the smallest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool of the smallest particle size range is reached, the radioactive nuclide liquid to be measured is passed into the next sample pool of the particle size range larger than the smallest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the next sample pool of the particle size range larger than the smallest particle size range is reached, the radioactive nuclide liquid to be measured is continued to be passed into the sample pool of the larger particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline until the measuring range of the sample pool of the largest particle size range is reached, and the measurement is stopped; If the activity of the radioactive nuclide gradually decreases, first pass the radioactive nuclide liquid to be measured into the sample pool with the largest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool with the largest particle size range is reached, pass the radioactive nuclide liquid to be measured into the next sample pool with a particle size range smaller than the maximum particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the next sample pool with a particle size range smaller than the maximum particle size range is reached, pass the radioactive nuclide liquid to be measured into the sample pool with a smaller particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline until the measuring range of the sample pool with the smallest particle size range is reached, and the measurement is stopped; If the activity of the radionuclide changes randomly, the radionuclide liquid to be tested is randomly introduced into a sample pool through the inlet pipeline or the switches on the inlet pipeline and the outlet pipeline. If the activity of the radionuclide continues to increase and reaches the measurement range of the random sample pool, the radionuclide liquid to be tested is introduced into a sample pool with a larger particle size through the switches on the inlet pipeline and the outlet pipeline. If the activity of the radionuclide in the sample pool with a larger particle size range decreases and reaches the measurement range of the sample pool with a larger particle size range, the radionuclide liquid to be tested is randomly introduced into a sample pool through the inlet pipeline or the switches on the inlet pipeline and the outlet pipeline. The switch on the liquid passes the radioactive nuclide liquid to be tested into a sample pool with a smaller particle size; if the concentration of the radioactive nuclide liquid to be tested passed into the random sample pool continues to decrease and reaches the measurement range of the random sample pool, the switch on the liquid inlet pipeline and the liquid outlet pipeline is used to pass the radioactive nuclide liquid to be tested into a sample pool with a smaller particle size range; if the activity of the radioactive nuclide increases and reaches the measurement range of the sample pool with a smaller particle size range, the radioactive nuclide liquid to be tested is passed into a sample chamber with a larger particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline.

10. The method for online monitoring of radioactive nuclides in liquid with an ultra-wide measurement range according to claim 9, characterized in that: The method comprises the following steps: Counting the current pulse signal output by the photon detection module, and calculating the activity of the radioactive nuclide in the liquid according to the counting rate of the current pulse signal; According to the activity of radionuclides, sample pools with different particle size ranges are selected for online monitoring of radionuclides: If the activity of the radioactive nuclide gradually increases, the liquid of the radioactive nuclide to be measured is passed into the sample pool of the smallest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool of the smallest particle size range is reached, the liquid of the radioactive nuclide to be measured is passed into the sample pool of the moderate particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool of the moderate particle size range is reached, the liquid of the radioactive nuclide to be measured is passed into the sample pool of the largest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool of the largest particle size range is reached, the measurement is stopped; If the activity of the radionuclide gradually decreases, first pass the radionuclide liquid to be measured into the sample pool of the largest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the measuring range of the sample pool of the largest particle size range is reached, pass the radionuclide liquid to be measured into the sample pool of the moderate particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline, or pass the radionuclide liquid to be measured into the sample pool of the moderate particle size range and the maximum particle size range at the same time. If the measuring range of the sample pool of the moderate particle size range is reached, pass the radionuclide liquid to be measured into the sample pool of the smallest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline, or pass the radionuclide liquid to be measured into the sample pool of the smallest particle size range, the moderate particle size range and the maximum particle size range at the same time. If the measuring range of the sample pool of the smallest particle size range is reached, stop the measurement; If the activity of the radionuclide changes randomly, the liquid of the radionuclide to be measured is passed into the sample pool with an appropriate particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the activity of the radionuclide continues to increase and reaches the measurement range of the sample pool with an appropriate particle size range, the liquid of the radionuclide to be measured is passed into the sample pool with the largest particle size range through the switch on the liquid inlet pipeline and the liquid outlet pipeline. If the activity of the radionuclide decreases and reaches the measurement range of the sample pool with the largest particle size range, the liquid of the radionuclide to be measured is passed into the sample pool with the largest particle size range through the liquid inlet pipeline or the switch on the liquid inlet pipeline and the liquid outlet pipeline. The radioactive nuclide liquid is passed into the sample chamber with a moderate particle size range; if the concentration of the radioactive nuclide liquid to be tested in the sample pool with a moderate particle size range continues to decrease and reaches the measuring range of the sample pool with a moderate particle size range, the radioactive nuclide liquid to be tested is passed into the sample pool with the smallest particle size range through the switches on the liquid inlet pipeline and the liquid outlet pipeline; if the activity of the radioactive nuclide increases and reaches the measuring range of the sample pool with the smallest particle size range, the radioactive nuclide liquid to be tested is passed into the sample chamber with a moderate particle size range through the liquid inlet pipeline or the switches on the liquid inlet pipeline and the liquid outlet pipeline.

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