| Radionuclides can enter the human body as one drink water,and the α/β Radiation it generates dangers human health and may cause cancer in serious cases.Therefore,it is of great significance to timely detect and master the radiation situation of water bodies.The current methods for detecting gross α/β radioactivity in water require complex operation with low efficiency.Therefore,it is urgent to establish a set of grossα/β radioactivity monitoring system that can be set on site in real time,so as to provide data support for daily water radioactivity reporting,excessive warning and decisionmaking of relevant departments.RO membrane(Reverse Osmosis membrane)separation technology has made many achievements and been widely used in the fields of nuclide separation and radioactive wastewater treatment,while it has not been used in the field of radioactive detection yet.In this paper,the RO membrane separation technology and radiation detection technology are combined to complete the following research work:(1)The surface morphology,desalting rate and retention rate of key nuclides of nanofiltration membrane and Reverse Osmosis membrane were studied and compared,and a method of water radioactivity measurement based on the concentration method of reverse osmosis membrane was proposed.The SEM surface morphology showed that there was no significant difference between NF90 NF membrane and THM10A reverse osmosis membrane.The desalination rate of reverse osmosis membrane is 5.]%higher than that of nanofiltration membrane,and the interception rate of americium241,uranium,thorium,radium,cesium-137 and strontium-90 is 9.1%～10.3%higher than that of nanofiltration membrane.According to the above conclusions,reverse osmosis membrane with higher interception ability is selected as the substrate material for nuclide enrichment.In this paper,the detection efficiency calibration method based on the mass and detection efficiency of the film surface was studied.The problem of inaccurate calculation of gross α/β activity with constant detection efficiency was solved.(2)The performance of filter enrichment module and reverse osmosis membrane module were designed and optimized.The pressure threshold and pressure retaining threshold of Reverse Osmosis membrane components are studied.The results show that the maximum operating pressure of 1 MPa can ensure the stable operation of the device.According to the measured data,LIBS surface analysis and CFD fluid simulation,the problems of poor sample uniformity and time-consuming problems were solved.The filter device was optimized,and the "mixed filter" was proposed to replace the original dead end filter.The results showed that the stability of the measured gross a increased by 3.56%～7.41%.The stability of gross β was increased by 2.18%～4.15%.Sample preparation time was reduced by 24.7%～45.3%.(3)The structure and function of an online monitoring system for gross α/β activity in water were designed and put into practice.The process of water radioactivity detection with reverse osmosis membrane as the base material is proposed,which can be divided into new membrane weighing→ background detection filtration enrichment→ residue-containing old membrane drying→ residue-containing old membrane weighing→gross activity measurement calculation.According to this process,after selecting the key equipment,a gross α/β automatic online monitoring system is constructed.Net platform developed the upper computer software of the system,through the software issued instructions to PLC,control the components to work together,and finally completed the contrast detection,continuous monitoring,equipment records,equipment Settings and other preset functions,to achieve the development of hardware and software system of the whole machine.(4)The laboratory performance test and continuous field verification of the monitoring system have been completed.The recovery rate of gross a are among 92.4%～108.09%,and the average recovery rate is 99.95%.The relative error to the true value is 1.21%～7.60%,and the average relative error is 4.69%.The recovery rate of gross β ranged from 92.10%～109.31%,with an average recovery of 99.09%.The relative error with the real value is 2.12%～9.31%,and the average relative error is 5.65%.The gross a relative error ranges from 2.72%～4.32%,and the gross P relative error ranges from 2.39%～5.59%.The two-year continuous tests in Lanzhou and Hengyang,which regularly took water samples near the water intake of the site for traditional thick source method detection,and finally deployed in Hengyang and Lanzhou detection system,verify the system on site environmental water samples continuous online monitoring ability,the results show that the system has good accuracy and stability.The study of this paper show that the online monitoring system of gross α/βradioactivity in water based on RO membrane enrichment pretreatment can achieve continuous and accurate monitoring of gross α/β radioactivity in water,and provide an advanced method for rapid acquisition of water radiation environmental information. |
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