An online monitoring system for total beta and total gamma in water

Abstract

The present invention relates to an online monitoring system for total beta and total gamma in water, comprising a sample pipeline and a sampling unit sequentially arranged on the sample pipeline, a concentration unit for concentrating ions on a water sample obtained by the sampling unit, a measuring unit for measuring the activity concentrations of total beta and total gamma in a concentrated solution, and a standard solution supply unit for providing a standard solution for calculating the detection efficiency of the measuring unit after detection by the measuring unit. The measuring unit comprises a vessel for holding the concentrated solution, a first detection mechanism for detecting the total beta and gamma activity concentration in the concentrated solution, a second detection mechanism for detecting the total gamma activity concentration in the concentrated solution, and a data collector. The monitoring system of the present invention has a reasonable structural design and high detection accuracy. It can be unmanned and stable and reliable through coordinated control of a system program, and is suitable for monitoring total beta and gamma nuclides in water.

Description

[0001] This application is a divisional application of the invention patent application with the application date of June 23, 2020, application number 202010577578.9, and invention name "A device for online monitoring of total beta and total gamma in water and a method for calculating the activity concentration of total beta and total gamma in water". Technical Field

[0002] The invention relates to the field of environmental detection, and in particular to an online monitoring system for total beta and total gamma in water. Background Art

[0003] The operation of nuclear facilities generates large quantities of beta and gamma radionuclides, which are released into the environment in liquid form, enter the biosphere through ecological cycles, and subsequently enter the human body, causing radiation damage. National Standard GB14587-2011 stipulates that "radioactive liquid effluents from nuclear power plants must be sampled and monitored online and continuously." Although nuclear power plants have installed online total gamma continuous monitoring systems at their liquid effluent outlets, these devices, with a detection limit of nearly 4 Bq / L, still pose significant environmental risks after discharge. Consequently, no nuclear power plants have installed total beta continuous monitoring systems.

[0004] Traditional total gamma measurements use a sodium iodide detector, which has extremely poor energy resolution and is difficult to distinguish specific nuclides. To distinguish specific nuclides, sampling and analysis are required. This operation is relatively complex and time-consuming, requiring a lot of manpower and material resources. Summary of the Invention

[0005] The purpose of the present invention is to provide an online monitoring system for total beta and total gamma in water in order to overcome the deficiencies of the prior art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] An online monitoring system for total beta and total gamma in water, comprising a sample pipe and a sampling unit sequentially arranged on the sample pipe, a concentration unit for concentrating ions in a water sample obtained by the sampling unit, and a measuring unit for measuring the activity concentrations of total beta and total gamma in a concentrated solution. The measuring unit comprises a vessel for holding the concentrated solution, a first detection mechanism for detecting the total beta and gamma activity concentrations in the concentrated solution, a second detection mechanism for detecting the total gamma activity concentration in the concentrated solution, and a data collector.

[0008] Preferably, the first detection mechanism includes a plastic scintillator detector capable of directly contacting the concentrated liquid and detecting total βγ rays in the concentrated liquid, and a first photomultiplier tube for amplifying the detection signal of the plastic scintillator detector and converting it into an electrical signal.

[0009] Preferably, the first detection mechanism further comprises a high-purity germanium detector arranged close to the vessel and detecting the total gamma rays in the concentrated liquid therein, and a second photomultiplier tube amplifying the detection signal of the high-purity germanium detector and converting it into an electrical signal.

[0010] Preferably, the concentration unit includes a primary concentration mechanism, a secondary concentration mechanism, and a tertiary concentration mechanism for sequentially concentrating ions on the obtained water sample.

[0011] Preferably, each stage of the concentration mechanism includes an osmotic membrane assembly, a first pressure sensor and a second pressure sensor provided upstream and downstream of the osmotic membrane assembly, and a pressure boosting valve provided upstream of the first pressure sensor.

[0012] Preferably, the sampling unit includes a water pump, a filter, a first liquid mass flowmeter, and a second liquid mass flowmeter arranged on the sample pipe. The water pump, the filter, and the first liquid mass flowmeter are arranged in sequence, and the second liquid mass flowmeter is located between the concentration unit and the measurement unit.

[0013] Preferably, the monitoring system also includes a standard solution supply unit for providing a standard solution to calculate the detection efficiency of the measuring unit after the measuring unit performs detection. The standard solution supply unit includes a reagent bottle containing the standard solution, a supply pipe connecting the reagent bottle with the sample pipeline, and a third liquid mass flow meter provided on the supply pipe. The connection between the supply pipe and the sample pipeline is located between the concentration unit and the first liquid mass flow meter.

[0014] The present invention also relates to a method for calculating the total beta and total gamma activity concentrations in water, wherein the calculation method uses the data information obtained during monitoring by the monitoring system described in the present invention. The data information obtained during monitoring includes: the count rate n of the high-purity germanium detector; γ ; Background count rate of high purity germanium detector n γ0 ; The third liquid mass flow meter measures the volume V3; the plastic scintillator detector count rate n s ; Plastic scintillator detector background count rate n s0 ; Plastic scintillator detector for γ measurement count rate n β ; First liquid mass flow meter volume V1; Second liquid mass flow meter volume V2; Background measurement time t0; c β is the β activity concentration in the standard solution; c |γ is the γ activity concentration in the standard solution.

[0015] Preferably, the calculation method includes the following calculation formula: where ε γ is the detection efficiency of high-purity germanium detector; ε βis the detection efficiency of the plastic scintillator detector; ρ is the response factor of the plastic scintillator detector and the high-purity germanium detector; is the system concentration ratio; A β is the total β activity concentration in water; A γ is the total γ activity concentration in water.

[0016] Preferably, the calculation method further includes the following calculation formula: Among them, MDC β is the detection limit of total β in water; MDC γ is the detection limit of total γ in water.

[0017] Due to the implementation of the above technical solution, the present invention has the following advantages compared with the prior art:

[0018] The online monitoring system for total beta and total gamma in water of the present invention concentrates ions in water through a concentration unit, and the concentrated liquid is measured by a plastic scintillator and a high-purity germanium detector respectively to calculate the activity concentrations of total beta and gamma nuclides in the water. The concentration rate of the concentration unit is not less than 40 times, the detection limit of total beta in water is as low as 1Bq / L, and the detection limit of gamma nuclides in water is as low as 0.1Bq / L. The monitoring system of the present invention has a reasonable structural design and high detection accuracy. It can be unmanned and stable and reliable through system program coordinated control, and is suitable for monitoring total beta and gamma nuclides in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the overall structure of the monitoring system of the present invention;

[0020] Figure 2 This is a schematic diagram of the structure of the measuring unit of the present invention from a top view;

[0021] Among them: G10, sample pipe; C1, water pump; C2, filter; C31, first liquid mass flowmeter; C32, second liquid mass flowmeter; B1, reagent bottle; B2, third liquid mass flowmeter; B3, supply pipe; N1, first-stage concentration mechanism; N2, second-stage concentration mechanism; N3, third-stage concentration mechanism; Z10, boosting valve; Y10, first pressure sensor; Y20, second pressure sensor; M10, permeable membrane; F10, flat three-way valve; J10, Marlin cup; J1, plastic scintillator detector; J2, first photomultiplier tube; J3, high-purity germanium detector; J4, second photomultiplier tube. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figures 1 to 2As shown, an online monitoring (device) system for total β and total γ in water includes a sample pipe g10 and a sampling unit sequentially arranged on the sample pipe g10, a concentration unit for concentrating ions of the water sample obtained by the sampling unit, and a measuring unit for measuring the activity concentration of total β and total γ in the concentrated liquid. In addition, the monitoring system also includes a standard solution supply unit for providing a standard solution for calculating the detection efficiency of the measuring unit after the measuring unit performs detection.

[0024] Specifically, the measuring unit includes a container for holding the concentrated liquid (a 1L Marin cup j10), a first detection mechanism for detecting the total βγ activity concentration in the concentrated liquid, a second detection mechanism for detecting the total γ activity concentration in the concentrated liquid, and a data collector. The first detection mechanism includes a plastic scintillator detector j1 that can directly contact the concentrated liquid and detect the total beta and gamma rays in the concentrated liquid, a first photomultiplier tube j2 that amplifies the detection signal of the plastic scintillator detector j1 and converts it into an electrical signal, a high-purity germanium detector j3 that is arranged close to the vessel and detects the total gamma rays in the concentrated liquid therein, and a second photomultiplier tube j4 that amplifies the detection signal of the high-purity germanium detector j3 and converts it into an electrical signal. The 1L Marlin cup j10 well has an inner diameter of 85 mm and a depth of approximately 100 mm. It is made of plastic and contains a high-purity germanium detector j3 with a diameter of 83 mm and a height of 100 mm. The Marlin cup j10 well and the annular plastic scintillator detector j1 are an integrated structure, that is, the plastic scintillator detector j1 forms the outer wall of the Marlin cup j10, and the plastic scintillator is in direct contact with the liquid to be tested.

[0025] During online monitoring, the electric refrigeration unit of the high-purity germanium detector j3 must be turned on first to cool it to below -179°C, and the plastic scintillator detector j1 must be turned on. After the background measurement is stable, water samples can be collected for monitoring.

[0026] The plastic scintillator detector j1 measures the total βγ rays in the test liquid, and the signal is amplified by the first photomultiplier tube j2 and collected into the data acquisition device. The activity concentration of the total βγ in the water is calculated by software.

[0027] The high-purity germanium detector j3 is used to measure the gamma rays in the liquid to be tested. The signal is amplified by the second photomultiplier tube j4 and collected into the data acquisition device. The activity concentration of the gamma nuclide in the water is calculated by software to obtain the total gamma measurement result. The total gamma measurement result is calculated with the measurement result of the above-mentioned plastic detector to obtain the activity concentration of the total beta in the liquid to be tested.

[0028] Furthermore, the sampling unit includes a water pump c1, a filter c2, a first liquid mass flowmeter c31, and a second liquid mass flowmeter c32 arranged on the sample pipe g10. The water pump c1, the filter c2, and the first liquid mass flowmeter c31 are arranged in sequence, and the second liquid mass flowmeter c32 is located between the concentration unit and the measurement unit.

[0029] The standard solution supply unit includes a reagent bottle b1 containing the standard solution, a supply pipe b3 connecting the reagent bottle b1 with the sample pipe g10, and a third liquid mass flowmeter b2 provided on the supply pipe b3. The connection between the supply pipe b3 and the sample pipe g10 is located between the concentration unit and the first liquid mass flowmeter c31, and a flat three-way valve f10 is provided at the connection between the supply pipe b3 and the sample pipe g10.

[0030] The flat three-way valve f10 provided at the connection between the supply pipe b3 and the sample pipe g10 is controlled to connect the supply pipe b3 with the concentration unit and the measurement unit on the sample pipe g10. The total β and γ nuclide standard substances in the reagent bottle b1 are quantitatively transferred through the third liquid mass flowmeter b2. After concentration in the concentration unit, the standard substances enter the measurement unit to calibrate the efficiency of the plastic scintillator detector j1 and the high-purity germanium detector j3. That is, before monitoring the total β and total γ in water, the plastic scintillator and the high-purity germanium detector j3 of the measurement unit are first calibrated with a standard solution to calculate the detection efficiency of the plastic scintillator detector j1 and the high-purity germanium detector j3.

[0031] Furthermore, the concentration unit includes a first-level concentration mechanism n1, a second-level concentration mechanism n2, and a third-level concentration mechanism n3 for sequentially concentrating ions on the obtained water samples; each level of concentration mechanism includes an osmotic membrane assembly, a first pressure sensor y10 and a second pressure sensor y20 arranged upstream and downstream of the osmotic membrane assembly, and a boosting valve z10 arranged upstream of the first pressure sensor y10.

[0032] Each level of concentration mechanism includes a first pressure sensor y10 and a second pressure sensor y20 located upstream and downstream of its osmotic membrane assembly. Through the measurement information of the first pressure sensor y10 and the second pressure sensor y20, the system can control the pressure difference between the front and rear ends of the osmotic membrane m10, thereby achieving efficient water sample concentration.

[0033] The water sample passes through filter c2 and the first liquid mass flowmeter c31, then enters the primary concentration mechanism n1. It is pressurized to 300 kPa by the booster valve z10 of the primary concentration mechanism n1 and enters the osmotic membrane assembly of the primary concentration mechanism n1. The low-ion water is discharged from the side of the osmotic membrane m10 of the primary concentration mechanism n1.

[0034] The concentrated water collected by the first concentration mechanism n1 then enters the second concentration mechanism n2, where it is pressurized to 400 kPa by the booster valve z10 of the second concentration mechanism n2 and enters the osmotic membrane assembly of the second concentration mechanism n2. The low-ion water is then discharged from the side of the osmotic membrane m10 of the second concentration mechanism n2.

[0035] The concentrated water concentrated by the secondary concentration mechanism n2 then enters the tertiary concentration mechanism n3, is pressurized to 500 kPa by the booster valve z10 of the tertiary concentration mechanism n3, and enters the osmotic membrane assembly of the tertiary concentration mechanism n3. The low-ion water is discharged from the side of the osmotic membrane m10 of the tertiary concentration mechanism n3; then the concentrated water passes through the second liquid mass flowmeter c32 and enters the Marlin cup j10 of the measuring unit for measurement.

[0036] In addition, in this example, the permeable membrane assembly of each concentration mechanism includes two permeable membranes m10 (made of cellulose acetate) arranged in parallel. The inlets of the two permeable membranes m10 are connected to the sample pipe g10 through a flat three-way valve f10, and the concentrated liquid outlets of the two permeable membranes m10 are also connected to the sample pipe g10 through a flat three-way valve f10. When the water sample is monitored online, the liquid volume measured by the first liquid mass flowmeter c31 is compared with the liquid volume measured by the second liquid mass flowmeter c32 to calculate the concentration ratio of the water sample in the system. The concentration ratio is lower than the set value. After that, the system automatically switches from one permeable membrane m10 to another permeable membrane m10 to continue monitoring, and at the same time issues an alarm to remind the operator to replace the permeable membrane m10 used before the switch; when the inlet and concentrated liquid outlet of one permeable membrane m10 are connected to the sample pipe g10 through the flat three-way valve f10, the inlet and concentrated liquid outlet of the other permeable membrane m10 are disconnected from the sample pipe g10, that is, a one-in-one combination is adopted, by controlling the on and off of the flat three-way valve f10, the permeable membrane m10 can be replaced without stopping the machine, providing the premise for online continuous monitoring of the monitoring system.

[0037] In addition, the present invention also relates to a method for calculating the total beta and total gamma activity concentrations in water, which is calculated using the data information obtained during monitoring by the monitoring system described in the present invention;

[0038] The detection efficiency of the two detectors can be calculated by the third liquid mass flow meter b2, the plastic scintillator detector j1 count and the high-purity germanium detector j3 count using formula (1) and formula (2) respectively:

[0039]

[0040] Where: ε γ : Detection efficiency of high purity germanium detector j3, %;

[0041] n γ : High purity germanium detector j3 count rate, CPM;

[0042] n γ0 : High purity germanium detector j3 background count rate, CPM;

[0043] c |γ: activity concentration of γ nuclide in standard solution, Bq / L;

[0044] V3: The third liquid mass flowmeter b2 measures volume, L.

[0045]

[0046] Where: ε β : Detection efficiency of plastic scintillator detector j1, %;

[0047] n s : plastic scintillator detector j1 count rate, CPM;

[0048] n s0 : plastic scintillator detector j1 background count rate, CPM;

[0049] ρ: response factor of plastic scintillator detector j1 and high purity germanium detector j3, %;

[0050] c β : Activity concentration of β nuclide in standard solution, Bq / L.

[0051] The response efficiency of the plastic scintillator detector j1 and the high-purity germanium detector j3 were compared using γ standard materials. The response factor was calculated using formula (3):

[0052]

[0053] Where: n β : Plastic scintillator detector j1 measures the count rate of gamma nuclides, CPM.

[0054] Through the first liquid mass detector and the second liquid mass detector, the system concentration ratio can be calculated by formula (4):

[0055]

[0056] Where: System concentration ratio;

[0057] V1: volume of the first liquid mass flow meter c31, L;

[0058] V2: Volume of the second liquid mass flow meter c32, L.

[0059] The total β activity concentration in water and the total γ activity concentration in water can be calculated by formula (5) and formula (6) respectively through the measurement data of the system concentration ratio, plastic scintillator detector j1 and high-purity germanium detector j3.

[0060]

[0061] Where: Aβ : Total β activity concentration in water, Bq / L.

[0062]

[0063] Where: A γ : Total γ activity concentration in water, Bq / L.

[0064] The detection limits of total β and γ nuclides in water are calculated using formula (7) and formula (8) respectively:

[0065]

[0066] Where: MDC β : Detection limit of total β in water, Bq / L;

[0067] t0: Background measurement time.

[0068]

[0069] Where: MDC γ : Detection limit of total γ in water, Bq / L.

[0070] In summary, the online monitoring system for total beta and total gamma in water of the present invention concentrates ions in water through a concentration unit, and the concentrated liquid is measured by a plastic scintillator and a high-purity germanium detector respectively to calculate the activity concentrations of total beta and gamma nuclides in water. The concentration rate of the concentration unit is not less than 40 times, the detection limit of total beta in water is as low as 1Bq / L, and the detection limit of gamma nuclides in water is as low as 0.1Bq / L. The monitoring system of the present invention has a reasonable structural design and high detection accuracy. It can be unmanned and stable and reliable through system program coordinated control, and is suitable for monitoring total beta and gamma nuclides in water.

[0071] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. An online monitoring system for total beta and total gamma in water, characterized by: The monitoring system includes a sample pipe and a sampling unit sequentially arranged on the sample pipe, a concentration unit for concentrating ions in a water sample obtained by the sampling unit, a measurement unit for measuring the activity concentrations of total beta and total gamma in the concentrated solution, and a standard solution supply unit for providing a standard solution to calculate the detection efficiency of the measurement unit after detection by the measurement unit; the measurement unit includes a container for holding the concentrated solution, a first detection mechanism for detecting the total beta and gamma activity concentrations in the concentrated solution, a second detection mechanism for detecting the total gamma activity concentration in the concentrated solution, and a data collector; The first detection mechanism includes a plastic scintillator detector capable of directly contacting the concentrated liquid and detecting the total beta and gamma rays in the concentrated liquid, a first photomultiplier tube for amplifying the detection signal of the plastic scintillator detector and converting it into an electrical signal, a high-purity germanium detector arranged close to the vessel and detecting the total gamma rays in the concentrated liquid therein, and a second photomultiplier tube for amplifying the detection signal of the high-purity germanium detector and converting it into an electrical signal; The high-purity germanium detector is used to measure the gamma rays in the concentrated liquid. The signal is amplified by the second photomultiplier tube and collected into the data acquisition device. The activity concentration of the gamma nuclide in the water is calculated using the following formula: Where: A γ : total γ activity concentration in water, Bq / L; n γ : High purity germanium detector count rate, CPM; n γ0 : Background count rate of high purity germanium detector, CPM; ε γ : detection efficiency of high purity germanium detector, %; System concentration ratio.

2. The online monitoring system for total beta and total gamma in water according to claim 1, characterized in that: The sampling unit includes a water pump, a filter, a first liquid mass flowmeter, and a second liquid mass flowmeter arranged on the sample pipeline. The water pump, the filter, and the first liquid mass flowmeter are arranged in sequence, and the second liquid mass flowmeter is located between the concentration unit and the measurement unit.

3. The online monitoring system for total beta and total gamma in water according to claim 2, characterized in that: The standard solution supply unit includes a reagent bottle containing a standard solution, a supply pipe connecting the reagent bottle with a sample pipeline, and a third liquid mass flowmeter provided on the supply pipe. The connection between the supply pipe and the sample pipeline is located between the concentration unit and the first liquid mass flowmeter.

4. The online monitoring system for total beta and total gamma in water according to claim 1, characterized in that: The detection efficiency of the high-purity germanium detector is calculated by the following formula: Where: ε γ : detection efficiency of high purity germanium detector, %; n γ : High purity germanium detector count rate, CPM; n γ0 : Background count rate of high purity germanium detector, CPM; c |γ : activity concentration of γ nuclide in standard solution, Bq / L; V3: The measurement volume of the third liquid mass flow meter, L.

5. The online monitoring system for total beta and total gamma in water according to claim 1, characterized in that: The plastic scintillator detector measures the total βγ rays in the concentrated liquid, and the signal is amplified by the first photomultiplier tube and collected into the data acquisition device. The activity concentration of the total β in the water is calculated by the following formula: Where: A β : Total β activity concentration in water, Bq / L n s : plastic scintillator detector count rate, CPM; n s0 : plastic scintillator detector background count rate, CPM; ρ: response factor of plastic scintillator detector and high purity germanium detector, %; n γ : High purity germanium detector count rate, CPM; n γ0 : Background count rate of high purity germanium detector, CPM; ε β : detection efficiency of plastic scintillator detector, %; System concentration ratio.

6. The online monitoring system for total beta and total gamma in water according to claim 5, characterized in that: The detection efficiency of the plastic scintillator detector is calculated by the following formula: Where: ε β : detection efficiency of plastic scintillator detector, %; n s : plastic scintillator detector count rate, CPM; n s0 : plastic scintillator detector background count rate, CPM; ρ: j3 response factor of plastic scintillator detector and high purity germanium detector, %; c β : Activity concentration of β nuclide in standard solution, Bq / L.

7. The online monitoring system for total beta and total gamma in water according to claim 6, characterized in that: The response factor is calculated by the following formula: Where: n β : Plastic scintillator detector for gamma nuclide counting rate, CPM; n s0 : plastic scintillator detector background count rate, CPM; n γ : High purity germanium detector count rate, CPM; n γ0 : Background count rate of high-purity germanium detector, CPM.

8. The online monitoring system for total beta and total gamma in water according to claim 1 or 5, characterized in that: The system concentration ratio is calculated by the following formula: Where: System concentration ratio; V1: volume of the first liquid mass flow meter, L; V2: Volume of the second liquid mass flow meter, L.

9. The online monitoring system for total beta and total gamma in water according to claim 1, characterized in that: The detection limit of total β nuclides in water is calculated by the following formula: Where: MDC β : Detection limit of total β in water, Bq / L; t0: Background measurement time.

10. The online monitoring system for total beta and total gamma in water according to claim 1, characterized in that: The detection limit of total gamma nuclides in water is calculated using the following formula: Where: MDC γ : Detection limit of total γ in water, Bq / L.

11. The online monitoring system for total beta and total gamma in water according to claim 2, characterized in that: The vessel and the plastic scintillator detector are arranged as an integral structure, and the plastic scintillator detector constitutes the outer wall of the vessel.

12. The online monitoring system for total beta and total gamma in water according to claim 11, characterized in that: The concentration unit includes a permeable membrane assembly, a first pressure sensor and a second pressure sensor disposed upstream and downstream of the permeable membrane assembly, and a pressure boosting valve disposed upstream of the first pressure sensor.

13. The online monitoring system for total beta and total gamma in water according to claim 12, characterized in that: The permeable membrane assembly includes two permeable membranes arranged in parallel, and the inlets and outlets of the two permeable membranes are connected to the sample pipeline through a planar three-way valve.

14. The online monitoring system for total beta and total gamma in water according to claim 13, characterized in that: When the online monitoring system is used to monitor water samples online, the liquid volume measured by the first liquid mass flow meter is compared with the liquid volume measured by the second liquid mass flow meter to calculate the concentration ratio of the water sample in the system. When the concentration ratio is lower than the set value, one of the permeable membranes is switched to the other permeable membrane and monitoring is continued.

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