CN118068388A - Liquid effluent on-line monitoring system and on-line monitoring method based on nuclide analysis - Google Patents
Liquid effluent on-line monitoring system and on-line monitoring method based on nuclide analysis Download PDFInfo
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Abstract
The invention relates to a liquid effluent on-line monitoring system based on nuclide analysis, which comprises a sample pretreatment subsystem, a detector subsystem and a data control processing subsystem; the sample pretreatment subsystem comprises a wet oxidation unit, a radionuclide concentration unit and a refractory nuclide pretreatment unit; the detector subsystem comprises a beta array detector unit and a gamma detector unit; the gamma detector unit is arranged between the radionuclide concentration unit and the refractory nuclide pretreatment unit, and the refractory nuclide pretreatment unit is arranged between the beta array detector unit and the gamma detector unit; the data control processing subsystem comprises a data acquisition subsystem, a data monitoring subsystem and a graphic report subsystem. The online monitoring system can remarkably improve the advanced level of the liquid effluent monitoring equipment of nuclear facilities such as nuclear power plants and the like, and greatly improves the monitoring efficiency on the basis of meeting the national regulation and standard requirements.
Description
Technical Field
The invention belongs to the technical field of monitoring of liquid effluents of nuclear facilities such as nuclear power plants and the like, relates to a liquid effluent online monitoring system based on nuclide analysis and a method for online monitoring of liquid effluents based on the online monitoring system, and can cover online monitoring of monitoring items of current liquid effluent sampling nuclide analysis of all nuclear power plants, wherein the online monitoring items comprise H-3, C-14 and gamma nuclides in liquid outflow, refractory nuclides Sr-90, sr-89, fe-55, ni-63 and the like.
Background
At present, the monitoring of liquid effluents of nuclear facilities such as nuclear power plants and the like is designed for decades, and two sets of systems are adopted for carrying out effluent monitoring, namely on-line alarm monitoring and laboratory analysis. On-line alarm monitoring only measures total gamma radioactivity, generally adopts a NaI (Tl) detector, has no radionuclide quantification function, and only provides information of alarm and closing of certain valves; specific nuclide quantification needs to be done after analysis in the effluent laboratory after sample collection for counting the amount of radionuclide emitted in a batch and the total amount emitted over a certain period of time.
Currently, each nuclear power plant builds a plurality of effluent monitoring laboratories in the plant area according to the number of units for performing quantitative analysis of radioactivity in the discharged effluent. Each effluent laboratory is generally tens of square meters, is equipped with a plurality of sets of core analysis equipment (comprising a liquid flash spectrometer, a high-purity germanium spectrometer, an alpha/beta counter, a NaI spectrometer and the like) and is simultaneously equipped with a hot laboratory and a cold laboratory for sample preparation. The construction cost of each effluent laboratory and the configuration cost of the laboratory are estimated to be tens of millions of yuan, and the higher nuclear power construction cost is occupied. In addition, the liquid effluent on-line monitoring systems (as part of the KRT system) of current nuclear power plant configurations do not have nuclide analysis capabilities.
With the increasing demands on effluent monitoring management, liquid effluent monitoring will face greater operating pressures.
In recent years, based on the real demand of effluent monitoring, several nuclear power plants have been driving automated work or development of new methods for effluent monitoring. For example, studies have used NaI (Tl) gamma spectrometers or HPGe gamma spectrometers to directly conduct gamma radionuclide analyses, where specific radionuclides cannot be identified due to poor energy resolution of NaI (Tl). And the HPGe spectrometer is adopted for automatic measurement, and the detection limit level is higher because the sample is not concentrated. In addition, the current pure beta nuclides such as H-3, C-14, sr-90, sr-89, fe-55, ni-63 and the like are not fully utilized.
In general, the current design of monitoring liquid effluents is not applied by automated analysis techniques, the main work still depends on traditional manual operation, the efficiency is low, and the analyst may be exposed to a certain occupational irradiation risk. In the case of a lack of personnel configuration, problems with the quality of the effluent monitoring data may result.
Disclosure of Invention
In order to solve the problems faced by radionuclide monitoring in the liquid effluents of nuclear facilities of a nuclear power plant and the like at present, the invention provides a liquid effluent on-line monitoring system based on radionuclide analysis, which aims at national regulation standard requirements and realizes on-line monitoring of radionuclide analysis in the liquid effluents of the nuclear facilities of the nuclear power plant and the like based on radiochemical automation and novel detection technology.
The system and the corresponding method are used for on-line monitoring of radionuclides in liquid effluents of nuclear facilities such as nuclear power plants and the like, and comprise on-line monitoring of H-3, C-14 and other radionuclides in the liquid effluents, wherein the radionuclides comprise gamma nuclides and refractory nuclides such as Sr-90, ni-63, fe-55 and the like. The system comprises a sample pretreatment subsystem, a detector subsystem and a data control processing subsystem; the sample pretreatment subsystem comprises a wet oxidation unit, a radionuclide concentration unit and a refractory nuclide pretreatment unit; the detector subsystem comprises a beta array detector unit and a gamma detector unit; the gamma detector unit is arranged between the radionuclide concentration unit and the refractory nuclide pretreatment unit, and the refractory nuclide pretreatment unit is arranged between the beta array detector unit and the gamma detector unit; the data control processing subsystem comprises a data acquisition subsystem, a data monitoring subsystem and a graphic report subsystem.
According to some preferred embodiments of the invention, the beta array detector unit comprises a C-14 monitoring unit, an H-3 monitoring unit, a radioactive Sr monitoring unit, a radioactive Fe monitoring unit, a radioactive Ni monitoring unit; automated analysis was performed on pure beta nuclides in the liquid effluent. The C-14 monitoring unit is connected with the wet oxidation unit, the H-3 monitoring unit is connected with the radionuclide concentration unit, and the refractory nuclide pretreatment unit is connected with the radioactive Sr monitoring unit, the radioactive Fe monitoring unit and the radioactive Ni monitoring unit.
According to some preferred embodiments of the present invention, the refractory species includes Sr-90, sr-89, fe-55, ni-63.
According to some preferred embodiments of the invention, the wet oxidation unit is configured to chemically convert C-14 in the liquid effluent sample using a wet oxidation process to produce a 14CO2 sample for beta counting. Wet oxidation processes include, but are not limited to, chemical oxidation processes plus ultraviolet radiation sterilization processes. The chemical oxidation method adopts Fenton reagent, peroxide (such as Na 2S2O4) and the like.
Specifically, in some embodiments, the wet oxidation unit is designed in two alternative ways. The 14CO2 sample, which is converted to the gaseous state, is transferred by carrier gas or negative pressure to a C-14 monitoring unit in a beta array detector unit in the detector subsystem. 2 nd, capture with NaOH solution, transfer to C-14 monitoring unit in beta array detector unit in detector subsystem by opening valve. The recovery of C-14 was isolated and calculated by a high-precision CO 2 sensor. After each sample is collected in the wet oxidation unit, the collection bottle and the loop are cleaned by carrier gas or NaOH solution, and the cleaning time is generally several minutes. The purpose of the cleaning of the collection bottle and the sample feeding pipeline is to reduce the memory effect.
And collecting CO 2 gas or NaOH collecting liquid after the liquid effluent is treated by the wet oxidation unit, and performing beta counting by a C-14 monitoring unit in the beta array detector unit for 1-24 hours according to specific detection lower limit requirements. A wash and self-calibration is designed before each C-14 measurement to eliminate the effects of possible effects of memory. Wherein the cleaning liquid adopts tritium-free water, the cleaning time is designed to be several minutes to 1h, the self-calibration time is 1 to 2h, and the beta counting is formally carried out after the self-calibration.
According to some preferred embodiments of the invention, the radionuclide concentration unit is used for enriching radionuclides such as Cr, mn, co, co, fe, zn, ru, ag, sb, cs, I, sr, fe, ni except H-3 and C-14 in liquid effluent by ultrafiltration and electrodialysis, wherein the concentrated solution is used for gamma nuclide analysis and the fresh water is used for H-3 analysis.
Specifically, in some embodiments, the purification methods such as ultrafiltration adopted by the radionuclide concentration unit are mainly used for purifying macromolecular compounds (such as esters, surfactants, etc.), emulsions (such as grease-detergents and oil-water emulsions), etc. possibly existing in the liquid effluent, so as to provide raw water meeting the water inlet requirement for the electrodialysis treatment at the rear end, and avoid blocking an ion exchange membrane and damaging electrodes in the electrodialysis device; the electrodialysis method adopted by the radionuclide concentration unit has the advantages of high concentration multiple, strong decontamination capability, simple operation, lower energy consumption and the like, and has the characteristics of no environmental pollution and flexible system design when being used as a deep desalting technology. According to the electrodialysis method, the ion transmission direction is changed according to different anion/cation membrane sequences or membrane stack configurations of different types of ion membrane combinations, so that the purposes of concentration and separation are achieved. Electrodialysis methods provide a concentration ratio of 50 times or more for various radionuclides.
According to some preferred implementation aspects of the invention, the refractory nuclide pretreatment unit is used for further enriching Sr, fe and Ni elements in the concentrated solution by adopting an adsorption and desorption method to prepare samples for measuring decay counts of Sr-90, sr-89, fe-55 and Ni-63 refractory nuclides. The adsorption and desorption method adopts different types of cation resins and special effect resins to carry out adsorption and separation on Sr, fe, ni and other ions.
According to some preferred embodiments of the invention, the beta array detector unit adopts a multi-channel low-background beta counting measurement system to measure H-3, C-14, sr-90, sr-89, fe-55 and Ni-63 pure beta nuclides, and adopts a solid scintillation detection method or a liquid scintillation detection method. The number of the array detector units is determined according to actual requirements, and one array detector unit is generally configured for each of H-3, C-14, sr-90, sr-89, fe-55 and Ni-63. The solid scintillation detection method can adopt CaF Eu materials, plastic scintillation microspheres, scintillation optical fibers or other solid scintillation materials with scintillation characteristics. The scintillating material has certain structural stability and provides long-term running conditions for on-line monitoring. The liquid scintillation detection method can adopt a flowing liquid scintillation detection method. Based on scintillation detection materials, a single tube (photomultiplier tube, PMT or SiPM) or a multi-tube electronic system with coincidence and anti-coincidence functions is arranged in a unit mode, so that the background of beta detection is reduced, and the efficiency of beta detection is improved.
According to some preferred embodiments of the invention, the gamma detector unit is used for gamma counting measurements with a tellurium zinc cadmium detector or a high purity germanium detector. Cadmium Zinc Telluride (CZT) detector, high purity germanium detector (HPGe) with gamma ray resolution of not less than 1.3% for 662keV (Cs-137) energy. NaI (Tl) gamma spectrometers have poor energy resolution and cannot fully identify gamma radionuclides in liquid effluents.
The data control processing subsystem of the invention has the functions of: communicating with each functional module, setting parameters, debugging and the like; realizing an automatic measurement flow; collecting and displaying the states of all functional modules in real time; displaying the measurement data and the result in real time; storing and inquiring, and outputting a report; independent control of each module; the nuclide library is provided with each monitoring module for automatic identification and automatic measurement of nuclides; setting a concentration threshold; an external data interface is provided. The control system consists of an upper computer and a lower computer, wherein the upper computer is responsible for controlling the instruction issuing and data processing, and compiling by using Labview software; the lower computer is responsible for the implementation of control instructions, data acquisition and other works, and comprises a singlechip control module, a data acquisition module, a control feedback module and other modules.
According to some preferred embodiments of the present invention, the data acquisition subsystem operates in a service mode with a watchdog function for acquiring data generated during the monitoring process and transmitting the data to a background database for storage.
According to some preferred embodiments of the present invention, the data monitoring subsystem is used for real-time display of data, provides a convenient data switching display function, and can display in real time: (1) The operating state, operating parameters, possible fault information, etc. of the sample pretreatment subsystem; (2) The monitoring data and related parameters of the detector subsystem comprise the information of the activity concentration of H-3, C-14, gamma nuclides, refractory nuclides (Sr-90, sr-89, fe-55, ni-63 and the like) in the liquid effluent.
According to some preferred implementation aspects of the invention, the graphic report subsystem can graphically display monitoring data of the liquid effluent online monitoring system based on nuclide analysis, provide trend analysis and alarm data analysis, and provide special marks of alarm data and invalid data according to pre-design; and can inquire the measurement result in any time period, automatically generate output result in form, and realize remote printing function according to statistics and graph curve analysis. The monitoring data table provides data sample statistics including sample size, minimum, maximum, median, average, etc. The monitoring data form provides relevant early warning information, and provides warning according to relevant action level preset by a user.
The invention can realize the following functions and objects: (1) The on-line monitoring of all possibly related radionuclides in the liquid effluent required to be developed by national regulation standards can be realized, no human operation is needed, and the whole sample pretreatment and monitoring process is controlled through a preset program. The nuclides that are being monitored include H-3、C-14、Cr-51、Mn-54、Co-58、Co-60、Fe-59、Zn-65、Ru-106、Ag-110m、Sb-124、Sb-125、Cs-134、Cs-137、I-131、I-133、Sr-90、Sr-89、Fe-55、Ni-63, etc. (2) Typical lower detection limit levels for radionuclides in liquid effluents as specified by national regulatory standards can be achieved, with a lower detection limit of 1X 10 4Bq/m3 for H-3, 5X 10 4Bq/m3 for C-14, 1X 10 3Bq/m3 for Cs-137, 1X 10 2Bq/m3 for Sr-90, and 1X 10 3Bq/m3 for Fe-55 and Ni-63. (3) All the requirements of each batch measurement concerning the monitoring items in the liquid effluent developed by the national regulatory standards can be met.
The liquid effluent on-line monitoring system based on nuclide analysis has the sample treatment volume range of 100-200L, wherein the sample amount treated by the wet oxidation unit is less than 1L, and the sample amount treated by the radionuclide concentration unit is 50-200L. Meanwhile, the on-line monitoring system provides a radioactive concentration processing unit with concentration ratio of more than 50 times, and the detection efficiency of gamma nuclides and refractory nuclides (Sr-90, sr-89, fe-55, ni-63 and the like) is reduced by tens of times under other similar test conditions by sample concentration. The system adopts an integrated design, realizes modularization and compactness design on the sample pretreatment subsystem, the detector subsystem and the data control processing subsystem, and the projection area of the whole machine is not more than 4m 2.
The invention also provides an online monitoring method for liquid effluent according to the online monitoring system, which comprises the following steps:
the liquid effluent enters a sample pretreatment subsystem, part of the liquid effluent enters a wet oxidation unit, and C-14 in the part of the liquid effluent is subjected to chemical conversion to convert into a 14CO2 sample for beta counting;
the C-14 monitoring unit in the beta array detector unit counts beta of the 14CO2 samples obtained by conversion;
The rest liquid effluent enters a radionuclide concentration unit to concentrate radioactive elements in the rest liquid effluent;
the fresh water treated by the radionuclide concentration unit is led into an H-3 monitoring unit in the detector subsystem to carry out beta counting;
transferring the concentrated solution processed by the radionuclide concentration unit to a gamma detector unit of a detector subsystem, and carrying out online monitoring on gamma nuclides;
After the testing of the gamma detector unit is completed, the concentrated solution treated by the radionuclide concentration unit is transferred to a refractory nuclide pretreatment unit in a sample pretreatment subsystem to enrich and separate the radioactive Sr, fe and Ni; solutions for beta counting of the radioactive Sr, fe and Ni are respectively prepared and respectively transferred to a radioactive Sr monitoring unit, a radioactive Fe monitoring unit and a radioactive Ni monitoring unit in the beta array type detector unit for beta counting.
Compared with the prior art, the invention has the beneficial effects that: the liquid effluent on-line monitoring system based on nuclide analysis of the invention (1) adopts an automatic design to replace manual operation in a laboratory, obviously improves the generation level of nuclear facility liquid effluent monitoring equipment such as a nuclear power plant and the like, and promotes corresponding digital management; (2) saving labor cost and improving working efficiency; (3) Based on the application of the invention and the liquid effluent on-line monitoring system, the effluent laboratory construction expectation of nuclear facilities such as nuclear power plants and the like can be simplified or even cancelled, thereby indirectly saving the construction cost of the effluent monitoring facilities.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic block diagram of an on-line monitoring system for liquid effluent based on nuclide analysis in a preferred embodiment of the present invention.
In the figure: 1. a sample pretreatment subsystem; 2. a detector subsystem; 3.a data control processing subsystem; 4. a wet oxidation unit; 5. a radionuclide concentration unit; 6. a pretreatment unit for refractory nuclides (Sr-90, sr-89, fe-55, ni-63, etc.); 7. a beta array detector unit; 8. a gamma detector unit; 9. a C-14 monitoring unit; 10. an H-3 monitoring unit; 11. a radioactive Sr (Sr-90, sr-89) monitoring unit; 12. a radioactive Fe (Fe-55) monitoring unit; 13.a radioactive Ni (Ni-63) monitoring unit; 14. a data acquisition subsystem; 15. a data monitoring subsystem; 16. and the graphic report subsystem.
Detailed Description
For better understanding of the present invention, the objects, technical solutions and advantages thereof will be more clearly understood by those skilled in the art, and the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the implementation manner not shown or described in the drawings is a manner known to those of ordinary skill in the art. Additionally, although examples of parameters including particular values may be provided herein, it should be appreciated that the parameters need not be exactly equal to the corresponding values, but may be approximated to the corresponding values within acceptable error margins or design constraints. It will be apparent that the described embodiments are merely some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, in the description and claims, are intended to cover a non-exclusive inclusion, such that a process, method, apparatus, article, or device that comprises a list of steps or elements is not necessarily limited to those steps or elements that are expressly listed or inherent to such process, method, article, or device.
The liquid on-line monitoring system based on nuclide analysis can effectively liberate the two hands of nuclear power plant technology and management personnel, realize nuclide on-line analysis and report automatic generation, and improve the efficiency and management level of liquid effluent monitoring.
Example 1 on-line monitoring System
As shown in fig. 1, the liquid effluent on-line monitoring system based on nuclide analysis of the invention comprises a sample pretreatment subsystem 1, a detector subsystem 2 and a data control processing subsystem 3. The sample pretreatment subsystem 1 comprises a wet oxidation unit 4, a radionuclide concentration unit 5 and a pretreatment unit 6 for refractory nuclides (Sr-90, sr-89, fe-55, ni-63 and the like); the detector subsystem 2 comprises a beta array detector unit 7 and a gamma detector unit 8. The gamma detector unit 8 is arranged between the radionuclide concentration unit 5 and the refractory nuclide pretreatment unit 6, and the refractory nuclide pretreatment unit 6 is arranged between the beta array detector unit 7 and the gamma detector unit 8.
The beta array detector unit 7 comprises a C-14 monitoring unit 9, an H-3 monitoring unit 10, a radioactive Sr (Sr-90, sr-89) monitoring unit 11, a radioactive Fe (Fe-55) monitoring unit 12 and a radioactive Ni (Ni-63) monitoring unit 13. The C-14 monitoring unit is connected with the wet oxidation unit, the H-3 monitoring unit is connected with the radionuclide concentration unit, and the refractory nuclide pretreatment unit is connected with the radioactive Sr monitoring unit, the radioactive Fe monitoring unit and the radioactive Ni monitoring unit.
The wet oxidation unit adopts a wet oxidation method to chemically convert C-14 in the liquid effluent sample to prepare 14CO2 samples for beta counting. Wet oxidation treatment is generally found in total carbon analysis (TOC), and the existing industry standard "14 C analysis method in liquid effluent of nuclear power plant-wet oxidation method" (HJ 1056-2019) can adopt a high-intensity ultraviolet and strong oxidant double-cooperation oxidation digestion mode to digest samples, so as to meet the requirement of large-volume sample injection. 14CO2 absorption liquid prepared after wet oxidation treatment is automatically injected into a measuring chamber and detected by adopting a beta array detector.
And the radionuclide concentration unit is used for enriching radionuclides except H-3 and C-14 in the liquid effluent by adopting ultrafiltration, electrodialysis and other methods. Ultrafiltration is mainly used for providing raw water meeting water inlet requirements for the back-end electrodialysis treatment, and avoiding blocking of ion exchange membranes and damage of electrodes in electrodialysis equipment, and macromolecular compounds (such as esters, surfactants and the like) possibly existing in liquid effluents, emulsions (such as grease-detergents and oil-water emulsions) and the like. The principle of electrodialysis is to utilize the selective permeability of an ion exchange membrane to directionally migrate anions and cations through the ion exchange membrane under the action of an externally applied direct current electric field so as to realize the separation and purification of solute ions. The ion exchange membrane is a membrane synthesized by macromolecular or compound materials, has the characteristic of selectively penetrating ions, and comprises a cation exchange membrane and an anion exchange membrane, wherein the cation exchange membrane can selectively penetrate cations to block anions, and the anion exchange membrane can selectively penetrate anions to block cations. The prepared concentrated solution is repeatedly concentrated, so that up to 200 liters of liquid effluent is concentrated, the concentrated solution is used for gamma nuclide analysis and refractory nuclide analysis, and fresh water meets the water quality requirement (1X 10 -6 S/cm) and is used for H-3 analysis.
The refractory nuclides (Sr-90, sr-89, fe-55 and Ni-63) pretreatment unit further enriches elements such as Sr, fe and Ni in the refractory nuclides by adopting a plurality of adsorption and desorption methods to prepare samples for measuring the decay count of radioactive nuclides such as Sr-90, sr-89, fe-55 and Ni-63. The automatic radioactive treatment process is realized through programming, the beta radioactivity is measured by combining a scintillation counting technology, the quantification of Ni-63 and Fe-55 is automatically realized, and meanwhile, the measurement of Sr-89 and Sr-90 by adopting a Chenlukov counting method is considered.
The beta detector array detector detects refractory nuclides such as H-3, C-14, sr-90, sr-89, fe-55, ni-63 and the like, and adopts a multi-channel low-background beta counting measurement system for measurement, wherein the method comprises, but is not limited to, a solid scintillation detection method and a liquid scintillation detection method. The solid scintillation detection method can adopt plastic scintillation microspheres, scintillation optical fibers or other solid materials with scintillation characteristics. The scintillating material has certain structural stability and can provide long-term running conditions for on-line monitoring. The liquid scintillation detection method can adopt a flowing liquid scintillation detection method. Based on scintillation detection materials, an electronic system with coincidence and anti-coincidence functions is arranged in a unit configuration single tube or multiple tubes (PMT or SiPM) so as to reduce the background of beta detection and improve the efficiency of beta detection.
A gamma detector unit, which measures using a gamma counting measurement system, using detectors including, but not limited to, cadmium Zinc Telluride (CZT) detector, high purity germanium detector (HPGe), which has a gamma ray resolution of not less than 1.3% for 662keV (Cs-137) energy. The tellurium-zinc-Cadmium (CZT) detector has the main advantages of no need of low-temperature refrigeration and moderate resolution and energy resolution. The energy resolution for Cs-137 is typically better than 2%, although only 1/10 of the HPGe gamma spectrum, several gamma species involved in liquid effluent monitoring still have the ability to resolve.
The data control processing subsystem 3 comprises a data acquisition subsystem 14, a data monitoring subsystem 15 and a graphic reporting subsystem 16. The functions of the data control processing subsystem include: communicating with each functional module, setting parameters, debugging and the like; realizing an automatic measurement flow; collecting and displaying the states of all functional modules in real time; displaying the measurement data and the result in real time; storing and inquiring, and outputting a report; independent control of each module; the nuclide library is provided with each monitoring module for automatic identification and automatic measurement of nuclides; setting a concentration threshold; an external data interface is provided. The data control processing subsystem consists of an upper computer and a lower computer, wherein the upper computer is responsible for controlling the issuing of instructions and the data processing, and the Labview software is adopted for compiling; the lower computer is responsible for the implementation of control instructions, data acquisition and other works, and comprises a singlechip control module, a data acquisition module, a control feedback module and other modules.
The data acquisition subsystem operates in a service mode, has a watchdog function, and uploads data to a background database. The data monitoring subsystem provides monitoring data for real-time display, provides a convenient data switching display function, and can display in real time: (1) The operating state, operating parameters, possible fault information, etc. of the sample pretreatment subsystem; (2) The monitoring data and related parameters of the detector subsystem comprise the information of the activity concentration of H-3, C-14, gamma nuclides, refractory nuclides (Sr-90, sr-89, fe-55, ni-63 and the like) in the liquid effluent. The graphic report subsystem can graphically display monitoring data of the liquid effluent online monitoring system based on nuclide analysis, provide trend analysis and alarm data analysis, and provide special marks of alarm data and invalid data according to a pre-design; and can inquire the measurement result in any time period, automatically generate output result in form, and realize remote printing function according to statistics and graph curve analysis. The monitoring data table provides data sample statistics including sample size, minimum, maximum, median, average, etc. The monitoring data form provides relevant early warning information, and provides warning according to relevant action level preset by a user.
The liquid effluent online monitoring system based on nuclide analysis of the embodiment can develop all automatic pretreatment and online monitoring related to radionuclide in liquid effluent of a nuclear power plant based on the requirements of national regulation standards, and specifically comprises the following steps: (1) All possible radionuclides involved in the liquid effluent that are required to be developed by national regulatory standards, including H-3、C-14、Cr-51、Mn-54、Co-58、Co-60、Fe-59、Zn-65、Ru-106、Ag-110m、Sb-124、Sb-125、Cs-134、Cs-137、I-131、I-133、Sr-90、Sr-89、Fe-55、Ni-63, etc., can be achieved. (2) Typical lower detection limit levels for radionuclides in liquid effluents as specified by national regulatory standards can be achieved, with a lower detection limit of 1X 10 4Bq/m3 for H-3, 5X 10 4Bq/m3 for C-14, 1X 10 3Bq/m3 for Cs-137, 1X 10 2Bq/m3 for Sr-90, and 1X 10 3Bq/m3 for Fe-55 and Ni-63. (3) All the requirements of each batch measurement concerning the monitoring items in the liquid effluent developed by the national regulatory standards can be met. (4) According to the requirements of quality assurance, the sample retaining function is provided.
In this embodiment, the projection area of the whole system design corresponding to the data control processing subsystem is not greater than 4m 2. Under the condition that the existing liquid effluent sampling loop of the nuclear power plant or the nuclear facility is not required to be changed, the sample treatment volume range is 50-100L, wherein the sample amount treated by the wet oxidation unit is less than 1L, the sample amount treated by the radionuclide concentration unit is 100-200L, and the concentration ratio of more than 50 times is provided for gamma radionuclides and refractory nuclides (Sr-90, sr-89, fe-55, ni-63 and the like).
Example 2 on-line monitoring method
This embodiment provides a method for on-line monitoring of radionuclides in a liquid effluent using the on-line monitoring system of embodiment 1 above, comprising the steps of:
(a) The total sampling flow of the liquid effluent is 50-200L, and the liquid effluent enters the sample pretreatment subsystem 1, and 0.1-1L is taken to the wet oxidation unit 4 through the flow regulating valve to carry out chemical conversion on C-14 in the liquid effluent, so that the liquid effluent is converted into 14CO2 samples for beta counting.
The wet oxidation unit 4 is designed in two alternative ways. 1 st, is transferred by carrier gas or negative pressure to a C-14 monitoring unit 9 in a beta array detector unit 7 in the detector subsystem 2. 2 nd, capture with NaOH solution, transfer to C-14 monitoring unit 9 in beta array detector unit 7 in detector subsystem 2 by opening a valve. The recovery of C-14 was isolated and calculated by a high-precision CO 2 sensor. After each sample is collected in the wet oxidation unit 4, the collection bottle and the loop are cleaned with a carrier gas or NaOH solution, and the cleaning time is typically several minutes. The purpose of the cleaning of the collection bottle and the sample feeding pipeline is to reduce the memory effect.
(B) The liquid effluent is converted into CO 2 gas after being treated by the wet oxidation unit 4, is converted into liquid form by gas or NaOH trapping liquid, and further enters the C-14 monitoring unit 9 in the beta array detector unit 7 to carry out beta counting for 1-24 h, and is determined according to the specific detection lower limit requirement. A wash and self-calibration is designed before each C-14 measurement to eliminate the effects of possible effects of memory. Wherein the cleaning liquid adopts tritium-free water, the cleaning time is designed to be several minutes to 1h, the self-calibration time is 1 to 2h, and the beta counting is formally carried out after the self-calibration.
(C) The main flow of liquid effluent is transferred to the radionuclide concentration unit 5. The radionuclide concentration unit 5 uses ultrafiltration and electrodialysis to concentrate the concentration of elements such as Cr, mn, co, co, fe, zn, ru, ag, sb, cs, I, sr, fe, ni, which may be related to radioactivity, by more than 50 times, and the recovery rate is >90%.
(D) The fresh water treated by the radionuclide concentration unit 5, with a conductivity as low as 1×10 -6 S/cm, is directed to the H-3 monitoring unit 10 in the detector subsystem 2, and beta-counted in the H-3 monitoring unit 10. The counting time of H-3 measurement is 1-24H, and is determined according to the specific detection lower limit requirement. A wash and self-calibration is designed before each H-3 measurement to eliminate the effects of possible effects of memory. Wherein the cleaning liquid adopts tritium-free water, the cleaning time is designed to be several minutes to 1h, the self-calibration time is 1 to 2h, and the beta counting is formally carried out after the self-calibration.
(E) The concentrated solution processed by the radionuclide concentration unit 5 may involve concentration of radioactive elements such as Cr, mn, co, co, fe, zn, ru, ag, sb, cs, I, sr, fe, ni and the like to be concentrated by more than 50 times, 1-2L of the concentrated solution is transferred to the gamma detector unit 8 of the detector subsystem 2, and gamma nuclides are monitored on line. Detectors employed include, but are not limited to, cadmium Zinc Telluride (CZT) detectors, high purity germanium detectors (HPGe). The counting time is 1-24 h, and is determined according to the specific detection lower limit requirement. A wash and self-calibration is designed before each gamma measurement to eliminate the effects of possible effects of memory. The cleaning solution adopts deionized water, the cleaning time is designed to be several minutes to 1h, the self-calibration time is 1 to 2h, and the beta counting is formally carried out after the self-calibration.
(F) After the test of the gamma detector unit 8 is completed, the concentrated solution processed by the radionuclide concentration unit 5 is transferred to a pretreatment unit 6 of refractory nuclides (Sr-90, sr-89, fe-55, ni-63 and the like) in the sample pretreatment subsystem 1, and the radioactive Sr, fe and Ni in the concentrated solution are enriched and separated. The automatic separation time of the samples is about 2-8 h, solutions for beta counting of the radioactive Sr, fe and Ni are respectively prepared, and are respectively transferred to a radioactive Sr (Sr-90 and Sr-89) monitoring unit 11, a radioactive Fe (Fe-55) monitoring unit 12 and a radioactive Ni (Ni-63) monitoring unit 13 in a beta array detector unit 7, and the counting time of each sample is 1-24 h and is determined according to the specific detection lower limit requirement. Each monitoring unit is designed with a wash and self-calibration prior to each measurement to eliminate the effects of possible memory effects. The cleaning solution adopts deionized water, the cleaning time is designed to be several minutes to 1h, the self-calibration time is 1 to 2h, and the beta counting is formally carried out after the self-calibration.
The above embodiments are provided to illustrate the technical concept and features of the present invention and are intended to enable those skilled in the art to understand the content of the present invention and implement the same, and are not intended to limit the scope of the present invention. All equivalent changes or modifications made in accordance with the spirit of the present invention should be construed to be included in the scope of the present invention.
Claims (12)
1. The liquid effluent on-line monitoring system based on nuclide analysis is characterized by comprising a sample pretreatment subsystem, a detector subsystem and a data control processing subsystem; the sample pretreatment subsystem comprises a wet oxidation unit, a radionuclide concentration unit and a refractory nuclide pretreatment unit; the detector subsystem comprises a beta array detector unit and a gamma detector unit; the gamma detector unit is arranged between the radionuclide concentration unit and the refractory nuclide pretreatment unit, and the refractory nuclide pretreatment unit is arranged between the beta array detector unit and the gamma detector unit; the data control processing subsystem comprises a data acquisition subsystem, a data monitoring subsystem and a graphic report subsystem.
2. The on-line monitoring system of claim 1, wherein the β array detector unit comprises a C-14 monitoring unit, an H-3 monitoring unit, a radioactive Sr monitoring unit, a radioactive Fe monitoring unit, a radioactive Ni monitoring unit; the C-14 monitoring unit is connected with the wet oxidation unit, the H-3 monitoring unit is connected with the radionuclide concentration unit, and the refractory nuclide pretreatment unit is connected with the radioactive Sr monitoring unit, the radioactive Fe monitoring unit and the radioactive Ni monitoring unit.
3. The on-line monitoring system of claim 1, wherein the refractory species comprises Sr-90, sr-89, fe-55, ni-63.
4. The on-line monitoring system of claim 1, wherein the wet oxidation unit is configured to chemically convert C-14 in the liquid effluent sample using a wet oxidation process to produce a 14CO2 sample for beta counting.
5. The on-line monitoring system according to claim 1, wherein the radionuclide concentration unit is used for enriching radionuclides except H-3 and C-14 in the liquid effluent by ultrafiltration and electrodialysis, wherein the concentrated solution is used for gamma nuclide analysis, and the fresh water is used for H-3 analysis.
6. The on-line monitoring system according to claim 5, wherein the refractory nuclide pretreatment unit is configured to further enrich Sr, fe, ni elements in the concentrated solution by an adsorption/desorption method to prepare a sample for measurement of Sr-90, sr-89, fe-55, ni-63 refractory nuclide decay counts.
7. The on-line monitoring system of claim 1, wherein the β array detector unit is configured to measure pure β species of H-3, C-14, sr-90, sr-89, fe-55, ni-63 using a multi-channel low background β count measurement system, and the method is a solid scintillation detection method or a liquid scintillation detection method.
8. The on-line monitoring system of claim 1, wherein the gamma detector unit is configured to perform gamma count measurements using a tellurium-zinc-cadmium detector or a high purity germanium detector.
9. The on-line monitoring system of claim 1, wherein the data acquisition subsystem is configured to acquire data generated during the monitoring process and transmit the data to a background database for storage.
10. The on-line monitoring system of claim 1, wherein the data monitoring subsystem is configured for real-time display of data, including operating status, operating parameters, fault information of the sample pretreatment subsystem; the monitoring data and related parameters of the detector subsystem comprise activity concentration information of H-3, C-14 and gamma nuclides and refractory nuclides in liquid effluent.
11. The on-line monitoring system of claim 1, wherein the graphical reporting subsystem is configured to graphically display the monitored data to provide trend analysis and alarm data analysis; and inquiring the measurement results in any time period, and automatically generating output results in a form.
12. A method for on-line monitoring of liquid effluents according to the on-line monitoring system of any one of claims 1 to 11, characterized in that it comprises the steps of:
The liquid effluent enters a sample pretreatment subsystem, part of the liquid effluent enters a wet oxidation unit, and C-14 in the part of the liquid effluent is subjected to chemical conversion to convert the C-14 into 14CO2 samples for beta counting;
the C-14 monitoring unit in the beta array detector unit counts beta of the 14CO2 samples obtained by conversion;
The rest liquid effluent enters a radionuclide concentration unit to concentrate radioactive elements in the rest liquid effluent;
the fresh water treated by the radionuclide concentration unit is led into an H-3 monitoring unit in the detector subsystem to carry out beta counting;
transferring the concentrated solution processed by the radionuclide concentration unit to a gamma detector unit of a detector subsystem, and carrying out online monitoring on gamma nuclides;
After the testing of the gamma detector unit is completed, the concentrated solution processed by the radionuclide concentration unit is transferred to a refractory nuclide pretreatment unit in a sample pretreatment subsystem, and the radioactive Sr, fe and Ni in the concentrated solution are enriched and separated to prepare solutions for counting the radioactive Sr, fe and Nibeta respectively;
And respectively transferring the materials to a radioactive Sr monitoring unit, a radioactive Fe monitoring unit and a radioactive Ni monitoring unit in the beta array detector unit for beta counting.
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