A gas multi-point sampling online radioactivity measurement system and method

Abstract

The present invention belongs to nuclear facility radioactivity monitoring technology, and specifically relates to a gas multi-point sampling online radioactivity measurement system and method. The system includes a first measurement chamber, a second measurement chamber, a third measurement chamber, a sampling pipeline, a purge pipeline and an exhaust pipeline; the sampling pipeline includes a plurality of parallel sampling solenoid valves, a sampling manifold, a filter device, and a first manual regulating valve, and the purge pipeline includes an air dust removal device and a second manual regulating valve; firstly, a high-purity germanium energy spectrum detector S is placed at the measurement position of the three measurement chambers, the exhaust pipeline is opened, and sampling is started, and at the same time, the radiation count rate level of the smallest measurement chamber is measured, and then the radiation count rate level cps of the smallest measurement chamber is determined and the energy spectrum measurement and analysis are performed, and the background radiation count rate of each chamber is determined after purging. The device and method realize the analysis and measurement of the nuclide components of the sampled gas, improve the efficiency of sampling measurement, and reduce the risk of contamination of the inner wall of the measurement chamber.

Description

Technical Field

[0001] The invention belongs to nuclear facility radioactivity monitoring technology, and in particular relates to a gas multi-point sampling online radioactivity measurement system. Background Art

[0002] During the operation and production process of nuclear facilities, radioactive gases are generated. The online measurement equipment currently used can only monitor the total radioactive activity of the gas, but cannot identify the nuclide components in the radioactive gas and the corresponding radioactive activity of the nuclides. It cannot meet the requirements of certain process systems and effluent monitoring, and can only obtain results through laboratory equipment analysis and measurement by manual sampling. In addition, the existing measurement and sampling system adopts a design and operation mode of one instrument corresponding to one measurement point, so the number of equipment layouts is large, resulting in high engineering costs for nuclear facility sampling and measurement systems. At the same time, since the sampling pipeline and the instrument measurement chamber are in direct contact with the measurement gas, after long-term operation, the gas sampling pipeline and the inner wall of the measurement chamber are easily contaminated, which directly affects the accuracy of the gas sampling measurement results. Summary of the invention

[0003] The purpose of the present invention is to provide a gas multi-point sampling online radioactivity measurement system and method, which can collect the measured gas medium online and realize nuclide analysis and activity measurement.

[0004] The technical solution of the present invention is as follows:

[0005] A gas multi-point sampling online radioactivity measurement system comprises a first measurement chamber, a second measurement chamber, a third measurement chamber, a sampling pipeline, a purge pipeline and an exhaust pipeline;

[0006] The sampling pipeline includes a plurality of sampling solenoid valves connected in parallel, a sampling manifold connected to each sampling solenoid valve pipeline, a measured gas medium aerosol and an iodine filter device connected to the sampling manifold pipeline, and a first manual regulating valve installed on the measured gas medium aerosol and iodine filter device outlet pipeline, and the outlet of the first manual regulating valve is respectively connected to the inlet pipelines of the first measuring chamber, the second measuring chamber, and the third measuring chamber;

[0007] The purge pipeline includes an air dust removal device and a second manual regulating valve installed on the outlet pipeline of the air dust removal device, and the outlet of the second manual regulating valve is respectively connected to the inlet pipelines of the first measuring chamber, the second measuring chamber, and the third measuring chamber;

[0008] The exhaust pipeline includes an exhaust manifold connected to the outlets of the first measurement chamber, the second measurement chamber, and the third measurement chamber respectively.

[0009] The first measuring chamber has the largest volume, the second measuring chamber has the second largest volume, and the third measuring chamber has the smallest volume.

[0010] The volume of the first measuring chamber is 300 liters, the volume of the second measuring chamber is 30 liters, and the volume of the third measuring chamber is 3 liters.

[0011] A sampling loop flow meter is arranged on the pipeline between the sampling manifold and the aerosol and iodine filtering device of the gas medium to be measured.

[0012] Solenoid valves are respectively provided on the pipelines between the outlet of the first manual regulating valve and the inlets of the first measuring chamber, the second measuring chamber and the third measuring chamber, which are respectively recorded as the first solenoid valve of the measuring circuit, the second solenoid valve of the measuring circuit and the third solenoid valve of the measuring circuit.

[0013] Solenoid valves are respectively provided on the pipelines between the outlet of the second manual regulating valve and the inlets of the first measuring chamber, the second measuring chamber and the third measuring chamber; they are respectively recorded as the first solenoid valve of the gas purge circuit, the inlet of the second solenoid valve of the gas purge circuit and the third solenoid valve of the gas purge circuit.

[0014] The measuring ports of the first measuring chamber, the second measuring chamber and the third measuring chamber are provided with high-purity germanium energy spectrum detectors.

[0015] The high-purity germanium energy spectrum detector is provided with a rotatable collimator outside, and the upper surface of the first measurement chamber is fixedly provided with a self-checking radiation source slot, in which a Eu-152 standard radiation source is placed.

[0016] The outlet of the exhaust manifold is connected to the negative pressure inlet of the vacuum pump through a pipeline, and the positive pressure outlet of the vacuum pump is connected to the exhaust process pipeline of the factory building through a pipeline.

[0017] A method for measuring the online radioactivity of gas by multi-point sampling is based on the above-mentioned system for measuring the online radioactivity of gas by multi-point sampling, and comprises the following steps:

[0018] 1) Firstly, place the high purity germanium energy spectrum detector S at the measurement positions of the three measurement chambers;

[0019] 2) Open the exhaust pipeline, open the sampling pipeline, and take samples through the sampling solenoid valve;

[0020] 3) While sampling, measure the radiation count rate level of the smallest measurement chamber;

[0021] 4) Determination of the radiation count rate level cps and spectrum measurement analysis of the smallest measurement chamber;

[0022] 4.1) When cps < N1, select the largest measurement chamber for spectrum measurement and analysis, and after obtaining the radionuclide composition and volume activity of the radioactive gas, close the measurement loop corresponding to the largest measurement chamber;

[0023] 4.2) N1≤cps≤N2, select the measurement chamber with the second largest volume to perform spectrum measurement and analysis, and after obtaining the radionuclide composition and the volume activity of the radioactive gas, close the measurement loop corresponding to the measurement chamber with the second largest volume;

[0024] 4.3) When cps>N2, select the smallest measurement chamber to perform spectrum measurement and analysis, and after obtaining the radionuclide composition and volume activity of the radioactive gas, close the measurement loop corresponding to the smallest measurement chamber;

[0025] N1 is 150-250cps, N2 is 2500-3500cps;

[0026] 5) Open the purge line for purge;

[0027] 6) Measure the background radiation count rate of each chamber. If the measured values ​​are lower than their respective set values, the measurement ends; if any one or more of the measured values ​​are higher than the corresponding set values, go to step 5) until all measured radiation count rates are lower than the set values.

[0028] In the step 3), after the measured sampling flow rate reaches 20 L / min, the sampling gas continues to be introduced to start measuring the radiation count rate level of the measurement chamber with the smallest volume.

[0029] In the steps 4.1), 4.2) and 4.3), it must be ensured that the gas in the measurement chamber is completely replaced by the sampling gas.

[0030] In step 5), the purge loop flow rate is adjusted to 50 L / min, and the duration is 20-50 minutes.

[0031] The set values ​​are 50cps, 70cps, and 100cps respectively.

[0032] The remarkable effects of the present invention are as follows: a plurality of sampling pipelines and sampling solenoid valve groups are arranged at the front end of the measuring device, and the sampling of the gas medium at the corresponding sampling point can be realized by controlling the switch of the solenoid valve group on the sampling pipeline, thereby realizing multi-point measurement of the sample; three sampling and measuring chambers and a high-purity germanium energy spectrum detector are designed, so that the analysis and measurement of the radionuclide components of the sampled gas can be realized, and the corresponding measuring chamber is selected according to the radioactive counting rate level of the gas sampling medium, thereby improving the efficiency of sampling and measurement; by designing a clean air purge measurement loop, pure air is introduced into the sampling and measurement system, so that the sampling pipeline and the inner wall of the measuring chamber can be purged and cleaned, thereby reducing the risk of contamination of the inner wall of the measuring chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of a gas multi-point sampling online radioactivity measurement system;

[0034] Figure 2 The flow chart of the on-line radioactivity measurement method for gas multi-point sampling;

[0035] In the figure: 1. Sampling solenoid valve group unit; 2. Air dust removal device; 3. Aerosol and iodine filtering device for the gas medium to be measured; 4. The first solenoid valve V of the measuring circuit m1 ; 5. Measurement circuit second solenoid valve V m2 ;6. Measurement circuit third solenoid valve V m3 ; 7. Gas purge circuit first solenoid valve V f1 ; 8. Second solenoid valve V of gas purge circuit f2 ; 9. Gas purge circuit third solenoid valve V f3 ; 10. First measurement chamber MC1; 11. Second measurement chamber MC2; 12. Third measurement chamber MC3; 13. High purity germanium energy spectrum detector; 14. Exhaust manifold; 15. Suction pump; 16. Factory exhaust process pipeline; 17. Sampling manifold; 18. Sampling loop flow meter F1; 19. Purge loop flow meter F2; 20. Rotatable collimator; 21. Self-checking radiation source slot; 22. First manual regulating valve V C1 ; 23. Second manual regulating valve V C2 . DETAILED DESCRIPTION

[0036] The present invention will be further described below through the accompanying drawings and specific implementation methods.

[0037] like Figure 1 As shown,

[0038] The sampling pipeline is as follows:

[0039] The sampling solenoid valve group unit 1 consists of n sampling solenoid valves V s1 ~V snThe electromagnetic valves are connected in parallel to realize multi-point gas sampling and measurement through the control of electromagnetic valve switches. Each sampling electromagnetic valve is connected to the sampling manifold 17 through a pipeline.

[0040] The sampling manifold 17 is connected to the inlet end of the sampling loop flow meter F1 18 through a pipeline, and the outlet end of the sampling loop flow meter F1 18 is connected to the inlet of the measured gas medium aerosol and iodine filtering device 3 through a pipeline.

[0041] The outlet of the measured gas medium aerosol and iodine filter 3 is connected to the first manual regulating valve V through a pipeline. C1 22 Inlet connection, first manual regulating valve V C1 22 outlets are connected to the first solenoid valve V of the measuring circuit through pipelines m1 4. Measurement circuit second solenoid valve V m2 5. Measurement circuit third solenoid valve V m3 6 inlet connections.

[0042] Measuring circuit first solenoid valve V m1 The outlet 4 is connected to the inlet 10 of the first measuring chamber MC1 through a pipeline, and the second solenoid valve V m2 The outlet 5 is connected to the inlet 11 of the second measuring chamber MC2 through a pipeline, and the third solenoid valve V m3 6 The outlet is connected to the inlet of the third measuring chamber MC3 12 through a pipeline.

[0043] The purge line is as follows:

[0044] The outlet of the air dust removal device 2 is connected to the inlet of the purge circuit flow meter F2 19 through a pipeline, and the outlet of the purge circuit flow meter F2 19 is connected to the second manual regulating valve V C2 23 Inlet connection, second manual regulating valve V C2 23 outlets are connected to the first solenoid valve V of the gas purge circuit f1 7 Inlet, gas purge circuit second solenoid valve V f2 8 Inlet, gas purge circuit third solenoid valve V f3 9 inlet connections.

[0045] Gas purge circuit first solenoid valve V f1 7 outlet is connected to the inlet of the first measuring chamber MC110 through a pipeline, and the second solenoid valve V of the gas purge circuit f1 8 outlet is connected to the inlet of the second measuring chamber MC211 through a pipeline, and the third solenoid valve V of the gas purge circuit f1 The outlet 9 is connected to the inlet of the third measuring chamber MC312 through a pipeline.

[0046] The purge air passes through the air dust removal device 2 to remove dust from the air, thereby preventing dust deposition on the inner walls of the pipeline and the three measuring chambers mentioned above due to long-term operation, and reducing the occurrence of contamination of the measuring inner walls.

[0047] During detection, the high-purity germanium energy spectrum detector 13 is placed at the measurement positions of the first measurement chamber MC1 10, the second measurement chamber MC2 11, and the third measurement chamber MC3 12, and a non-contact measurement method is adopted.

[0048] The high purity germanium energy spectrum detector 13 is connected to a rotatable collimator 20, which is wrapped around the outside of the high purity germanium energy spectrum detector 13. Before measurement, the high purity germanium energy spectrum detector 13 can be checked for detector energy and efficiency characteristic technical performance parameters by a radioactive source placed in a self-checking radioactive source slot 21.

[0049] The self-checking radiation source slot 21 is fixed on the upper surface of the first measuring chamber MC110.

[0050] The exhaust pipeline is as follows:

[0051] The outlets of the first measurement chamber MC110, the second measurement chamber MC211, and the third measurement chamber MC312 are respectively connected to the inlet of the exhaust manifold 14 through pipelines; the outlet of the exhaust manifold 14 is connected to the negative pressure inlet of the exhaust pump 15 through a pipeline, and the positive pressure outlet of the exhaust pump 15 is connected to the factory exhaust process pipeline 16 through a pipeline.

[0052] Among the three measurement chambers, the first measurement chamber MC110 has the largest volume, the second measurement chamber MC211 is the second largest, and the third measurement chamber MC312 has the smallest volume.

[0053] In this embodiment, the volume of the first measuring chamber MC110 is 300 liters, the volume of the second measuring chamber MC211 is 30 liters, and the volume of the third measuring chamber MC312 is 3 liters.

[0054] like Figure 2 As shown, the measurement method using the above radioactive gas multi-point sampling measurement system is as follows:

[0055] Step 1. Place the detector and check using standard radiation sources

[0056] A rotatable collimation device 20 is installed on the high-purity germanium energy spectrum detector S13. The collimation hole of the rotatable collimation device 20 is aligned with the self-inspection radiation source slot 21. A Eu-152 standard radiation source is placed in the self-inspection radiation source slot 21. After the self-inspection is completed, subsequent steps are performed. The self-inspection method of the high-purity germanium energy spectrum detector S13 is a well-known technology for the equipment.

[0057] Step 2. Sampling at the sampling point

[0058] During the sampling measurement process, the air pump 15 is in an open operation state. s1 ~V sn The front end of each solenoid valve is connected to the corresponding sampling point, and the required sampling point can be sampled by opening one of the sampling solenoid valves.

[0059] Generally n is 1-20;

[0060] Step 3. Measurement of radioactivity technical level of the medium under test

[0061] During the gas sampling measurement, the radiation count rate level of the third measurement chamber MC3 (3L) 12 is measured. Open one of the solenoid valves in the solenoid valve group unit 1 and the third solenoid valve V of the measurement circuit. m3 6. The first manual regulating valve V C1 22. By adjusting the first manual regulating valve V C1 22, the sampling flow value in the pipeline measured by the sampling loop flow meter F118 reaches 20L / min. Continue to pass the gas (1 minute in this embodiment) until the gas in the third measurement chamber MC312 is completely replaced. Rotate the rotatable collimator 20 and align the collimation hole with the third measurement chamber MC312. The high-purity germanium energy spectrum detector 13 starts to measure the radiation count rate level.

[0062] Step 4. The high purity germanium energy spectrum detector 13 measures the radiation count rate cps in the third measurement chamber MC312, and compares the radiation count rate with the set value N1;

[0063] Step 4.1: When the radiation count rate cps is less than N1, the first measurement chamber MC1 (300L) 10 is selected to perform energy spectrum measurement and analysis.

[0064] Close the third solenoid valve V in the measurement circuit m3 6. Open the first solenoid valve V of the measurement circuit m1 4. Waiting time is 10 minutes. The sampling flow rate in step 3 has been adjusted to 20L / min to ensure that the gas in the first measurement chamber MC1 (300L) 10 is completely replaced by the measured medium gas at the sampling point corresponding to the solenoid valve in the magnetic valve group unit 1. Rotate the rotatable collimator 20, align the collimation hole of the rotatable collimator 20 with the first measurement chamber MC1 (300L) 11, and the high-purity germanium energy spectrum detector 13 starts the energy spectrum analysis measurement. According to the set measurement time, the energy spectrum analysis and measurement are completed to obtain the radioactive nuclide composition of the measured medium and the volume activity of the radioactive gas (which belongs to the basic function of the energy spectrum detector). Close the corresponding sampling solenoid valve in the solenoid valve group unit 1 and the first solenoid valve V of the measurement circuit m1 4.

[0065] Step 4.2: When the radiation count rate N1≤cps≤N2 is less than, the second measurement chamber MC2 11 is selected to perform energy spectrum measurement and analysis.

[0066] Close the third solenoid valve V in the measurement circuit m3 6. Open the second solenoid valve V of the measurement circuit m2 5. Waiting time is 3 minutes. The sampling flow rate in step 3 has been adjusted to 20L / min to ensure that the gas in the second measurement chamber MC211 is completely replaced by the measured medium gas at the sampling point corresponding to the solenoid valve in the magnetic valve group unit 1. Rotate the rotatable collimator 20, align the collimation hole of the rotatable collimator 20 with the second measurement chamber MC211, and the high-purity germanium energy spectrum detector 13 starts the energy spectrum analysis measurement. According to the set measurement time, the energy spectrum analysis and measurement are completed to obtain the radioactive nuclide composition of the measured medium and the volume activity of the radioactive gas. Close the corresponding sampling solenoid valve in the solenoid valve group unit 1 and the second solenoid valve V of the measurement circuit m2 5.

[0067] Step 4.3: When the radiation count rate cps>N2, the third measurement chamber MC312 is selected to perform energy spectrum measurement and analysis.

[0068] The high purity germanium energy spectrum detector 13 starts the energy spectrum analysis measurement, completes the energy spectrum analysis and measurement according to the set measurement time, and obtains the radioactive nuclide composition of the measured medium and the volume activity of the radioactive gas. The corresponding sampling solenoid valve in the solenoid valve group unit 1 and the third solenoid valve Vm36 of the measurement circuit are closed.

[0069] In this embodiment, N1 is 200 cps and N2 is 3000 cps.

[0070] Step 5 Air Purge

[0071] When step 4 is completed, open the second manual regulating valve V C2 23. Gas purge circuit first solenoid valve V f1 7. Second solenoid valve V for gas purge circuit f2 8. The third solenoid valve V of the gas purge circuit f3 9.

[0072] Adjust the second manual regulating valve V C2 23 degrees, according to the reading of the purge circuit flow meter F219, adjust the purge circuit flow to 50L / min. At this time, use clean air to purge the measurement chamber and pipelines for 20-50 minutes.

[0073] Step 6: Measure the background radiation count rate in each chamber

[0074] Align the collimation hole of the rotatable collimation device 20 to the measurement chamber MC1 10, the measurement chamber MC2 11, and the measurement chamber MC3 12 successively, and measure their radiation background radiation count rates in turn. If the measured values ​​are lower than the set values ​​B1, B2, and B3 respectively, the entire measurement process of the sampling point is completed, and step 7 is executed.

[0075] If any one or more of the measured values ​​are higher than the corresponding set values, go to step 5 to perform air purge of the measurement chamber and pipelines again until all measured radiation count rates are lower than the set values ​​B1, B2, and B3.

[0076] In this embodiment, B1, B2, and B3 are 50cps, 70cps, and 100cps, respectively.

[0077] Step 7. End of measurement.

[0078] If step 6 determines that the radiation count rate level of the measurement chamber is lower than the set values ​​B1, B2, and B3, the entire V sn The entire measurement process of the measuring point is completed.

[0079] After opening the other sampling point valves in the gas solenoid valve group unit 1, single-point or multi-point cycle measurement can be performed according to steps 1-7.

[0080] The gas multi-point sampling online radioactivity measurement system is an important part of the radioactivity monitoring of nuclear facilities. By setting a sampling solenoid valve on each sampling pipeline, multi-point sampling measurement of the gas medium can be achieved based on controlling the switch of the solenoid valve on the sampling pipeline. The online energy spectrum measurement system is equipped with three sampling measurement chambers and a high-purity germanium energy spectrum detector. The corresponding measurement chamber is selected according to the radioactivity count rate level of the gas sampling medium, which improves the efficiency of sampling measurement. The system also sets a clean air purge circuit to reduce the probability of measurement chamber contamination. At present, there are many gas sampling and measurement systems in domestic nuclear facilities. Since it has obvious effects in improving measurement efficiency and reducing system equipment cost, this invention has good application prospects in nuclear facilities.

Claims

1. A gas multi-point sampling online radioactivity measurement system, characterized in that: It includes a first measurement chamber MC1 (10), a second measurement chamber MC2 (11), a third measurement chamber MC3 (12), a sampling line, a purge line and an exhaust line; The sampling pipeline comprises a plurality of sampling electromagnetic valves connected in parallel, a sampling manifold (17) connected to each sampling electromagnetic valve pipeline, a measured gas medium aerosol and iodine filter device (3) connected to the sampling manifold (17) pipeline, and a first manual regulating valve V installed on the outlet pipeline of the measured gas medium aerosol and iodine filter device (3). C1 (22), the first manual regulating valve V C1 (22) The outlet is connected to the inlet pipelines of the first measuring chamber MC1 (10), the second measuring chamber MC2 (11), and the third measuring chamber MC3 (12) respectively; The purge pipeline comprises an air dust removal device (2) and a second manual regulating valve V installed on the outlet pipeline of the air dust removal device (2). C2 (23), the second manual regulating valve V C2 The outlet of (23) is connected to the inlet pipelines of the first measuring chamber MC1 (10), the second measuring chamber MC2 (11), and the third measuring chamber MC3 (12) respectively; The exhaust pipeline includes an exhaust manifold (14) connected to the outlets of the first measurement chamber MC1 (10), the second measurement chamber MC2 (11), and the third measurement chamber MC3 (12), respectively; The first measuring chamber MC1 (10) has the largest volume, the second measuring chamber MC2 (11) has the second largest volume, and the third measuring chamber MC3 (12) has the smallest volume; The outlet of the exhaust manifold (14) is connected to the negative pressure inlet of the exhaust pump (15) through a pipeline, and the positive pressure outlet of the exhaust pump (15) is connected to the factory exhaust process pipeline (16) through a pipeline; The measuring ports of the first measuring chamber MC1 (10), the second measuring chamber MC2 (11), and the third measuring chamber MC3 (12) are provided with high-purity germanium energy spectrum detectors (13); A sampling loop flow meter F1 (18) is provided on the pipeline between the sampling manifold (17) and the aerosol and iodine filtering device (3) for the gas medium to be measured.

2. A gas multi-point sampling online radioactivity measurement system as claimed in claim 1, characterized in that: The volume of the first measuring chamber MC1 (10) is 300 liters, the volume of the second measuring chamber MC2 (11) is 30 liters, and the volume of the third measuring chamber MC3 (12) is 3 liters.

3. A gas multi-point sampling online radioactivity measurement system as claimed in claim 1, characterized in that: The first manual regulating valve V C1 (22) and the pipelines between the outlet and the inlets of the first measurement chamber MC1 (10), the second measurement chamber MC2 (11), and the third measurement chamber MC3 (12) are respectively provided with solenoid valves, which are respectively denoted as the first solenoid valve V of the measurement circuit m1 (4) Measurement circuit second solenoid valve V m2 (5) and the third solenoid valve V of the measurement circuit m3 (6).

4. A gas multi-point sampling online radioactivity measurement system as claimed in claim 3, characterized in that: The second manual regulating valve V C2 Solenoid valves are respectively provided on the pipelines between the outlet (23) and the inlets of the first measurement chamber MC1 (10), the second measurement chamber MC2 (11), and the third measurement chamber MC3 (12); respectively denoted as the first solenoid valve V of the gas purge circuit f1 (7) Second solenoid valve V for gas purge circuit f2 (8) and the third solenoid valve V of the gas purge circuit f3 (9).

5. A gas multi-point sampling online radioactivity measurement system as claimed in claim 1, characterized in that: The high-purity germanium energy spectrum detector (13) is externally provided with a rotatable collimator (20), and the upper surface of the first measurement chamber MC1 (10) is fixedly provided with a self-checking radiation source slot (21), and a Eu-152 standard radiation source is placed in the self-checking radiation source slot (21).

6. A method for measuring the online radioactivity of gas by multi-point sampling, characterized in that: The method is based on the gas multi-point sampling online radioactivity measurement system as claimed in claim 1, comprising the following steps: 1) Firstly, a high purity germanium energy spectrum detector (13) is placed at three measurement positions of the measurement chamber; 2) Open the exhaust pipeline, open the sampling pipeline, and take samples through the sampling solenoid valve; 3) While sampling, measure the radiation count rate level of the smallest measurement chamber; 4) Determination of the radiation count rate level cps and spectrum measurement analysis of the smallest measurement chamber; 4.1) When cps < N1, select the largest measurement chamber for spectrum measurement and analysis, and after obtaining the radionuclide composition and volume activity of the radioactive gas, close the measurement loop corresponding to the largest measurement chamber; 4.2) N1≤cps≤N2, select the measurement chamber with the second largest volume to perform spectrum measurement and analysis, and after obtaining the radionuclide composition and the volume activity of the radioactive gas, close the measurement loop corresponding to the measurement chamber with the second largest volume; 4.3) When cps>N2, select the smallest measurement chamber to perform spectrum measurement and analysis, and after obtaining the radionuclide composition and volume activity of the radioactive gas, close the measurement loop corresponding to the smallest measurement chamber; N1 is 150-250cps, N2 is 2500-3500cps; 5) Open the purge line for purge; 6) Measure the background radiation count rate of each chamber. If the measured values ​​are lower than their respective set values, the measurement ends; if any one or more of the measured values ​​are higher than the corresponding set values, go to step 5) until all measured radiation count rates are lower than the set values.

7. A method for measuring radioactivity by multi-point sampling of gas as claimed in claim 6, characterized in that: In the step 3), after the measured sampling flow rate reaches 20 L / min, the sampling gas continues to be introduced to start measuring the radiation count rate level of the measurement chamber with the smallest volume.

8. A method for measuring radioactivity by multi-point sampling of gas as claimed in claim 6, characterized in that: In the steps 4.1), 4.2) and 4.3), it must be ensured that the gas in the measurement chamber is completely replaced by the sampling gas.

9. A method for measuring the online radioactivity of gas by multi-point sampling as claimed in claim 6, characterized in that: In step 5), the purge loop flow rate is adjusted to 50 L / min, and the duration is 20-50 minutes.

10. A method for measuring radioactivity of gas by multi-point sampling online as claimed in claim 6, characterized in that: The set values ​​are 50cps, 70cps, and 100cps respectively.

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