Design And Evaluation Of On-line Monitoring System For Water Radiation

With the development of nuclear technology,the nuclear activities around people have been increasing,and the problem of radioactive pollution has also appeared in the benefit of society.When the radioactive waste liquid discharged from uranium ore and radioactive associated mines,factories and nuclear power plants into the surrounding water,it will have a certain influence on the environment safety and ecological balance of the surrounding water.Therefore,the research on the method of monitoring the radioactivity of water is paid attention.At present,the establishment of the radioactivity monitoring system in China is not perfect,and the sampling method and the laboratory energy spectrum analysis method are used to monitor the inland water body and the marine water body.However,these two methods can not reflect the radioactivity level of target waters in real time because of the long sampling period,cumbersome operation procedures and poor timeliness of measurement and analysis.Based on the current situation of radioactivity monitoring in water bodies and the monitoring of radioactivity level in inland water bodies,the design and analysis of water radioactivity monitoring system based on Na I(Tl)detector and HPGe detector are carried out respectively in this paper.Firstly,the water ? radiation monitoring system based on 10cm×10cm×40cm Na I(Tl)detector is designed,the system detection part is optimized and analyzed by using Monte Carlo numerical method,finally the thickness of the system lead shield is 10 cm,and the inner dimension of lead box is 64×64cm.According to the average concentration of natural radionuclides in water,the natural radioactivity instrument spectra of Ra(U)series,Th system and K were calculated,and the detection sensitivity,minimum detectable activity and minimum detectable concentration of radionuclide 131 I,137Cs and 60 Co were computed respectively.At the same time,a water ? radiation monitoring system based on HPGe detector is designed,which is used to monitor the radioactivity of water body by pumping.In this paper,the system size is designed and the detection efficiency of 40 K,131I,137 Cs and 60 Co of the detection system is calculated by using Monte Carlo numerical method.According to the design parameters,the monitoring system is built and the indexes of the system are tested.The detection efficiency of 40 K is calculated by measuring KCl solution,and the detection efficiency deviation of simulation and experiment is less than 2.3%.The detection sensitivity,minimum detectable activity and minimum detectable concentration of radionuclide 131 I,137Cs and 60 Co are analyzed based on the spectral and detection efficiency of analog instruments.At last,a three-dimensional instantaneous diffusion model of radioactive pollutant in water is considered,and the diffusion model of radioactive material in water is simulated and analyzed,and the relationship between the concentration of radioactive material and the source concentration is established,which provides the basis for the installation of monitoring system.It also provides reference for the traceability of radioactivity in the related water bodies.