| BackgroundRadon and its daughters widely exist on the earth,which is the most important source of internal radiation.It causes internal radiation in the respiratory system,especially serious damage to lung cells,which greatly increases the probability of lung cancer.The risk of personal internal exposure caused by radon and its daughters of workers in uranium mines,non uranium mines and underground culverts should be paid special attention to,and personal dose monitoring should be carried out.At present,the radon personal dosimeter used for wearing and the supporting system mainly adopt the solid nuclear track detection technology.The health industry standard WS/T 675-2020 radon and its daughters personal dose monitoring method has stipulated the measurement system and performance requirements composed of the radon personal dosimeter using the solid nuclear track detection technology,the chemical etching device and the track readout system.Although there are various systematic measurement systems,there are also independent dosimeters and reading systems,In particular,the radon personal cumulative dosimeter for personal monitoring purposes has not been widely used.At the same time,there are many kinds of radon dosimeters using solid nuclear track technology.Because the filter membrane,gap,shape,size and volume of the dosimeter have different effects on the dosimeter,especially for automatic measurement,and there is no radon personal dosimeter system in China It is necessary to carry out the research on the performance experiment of dosimeter and measuring system..ObjectiveBased on the taslimage automatic track reading system,the chemical etching conditions of the solid nuclear track detector used for radon personal dose measurement are experimentally studied in this study.The main radiation performance quantities and experimental methods are established to compare and study the radon personal dose meters with different structures commonly used in the current market,so as to grasp the influence on the measurement results and design or select radon personal dose meters It provides reference for human dosimeter,personal dose monitoring of radon and performance test of measurement system of personal dose monitoring of radonMethods and contentsThe main contents and methods of this study are as follows(1)Based on the investigation and summary of the structural characteristics of commonly used radon personal dosimeters,the measurement system and experimental process based on taslimage automatic track recognition are established.According to the radon personal dose monitoring specifications and reference to the relevant verification regulations,the main radiation performance quantities and experimental methods are established(2)Using the detector produced by track analysis systems(TASL)in the UK and based on taslimage system,orthogonal experiments were carried out on three main etching influence conditions,namely etching time,etching solution concentration and etching temperature.Track image and track density were analyzed and studied to determine the best etching conditions of the measurement system.(3)Three groups of the same dosimeter are equipped with three kinds of filter membranes of different materials,and the same detector is equipped.The standard radon chamber is used to carry out low,medium and high concentration experiments,and the concentration in use is used to carry out accumulation experiments in different periods of time.Through the study of the main radiation performance,the influence of different materials of filter membranes on the measurement results is analyzed and compared.(4)In the investigation of existing radon dosimeters at home and abroad,seven different types of radon dosimeters with different structures are selected,equipped with the same detector,and the standard radon chamber is used to carry out low,medium and high concentration experiments respectively,as well as the accumulation experiments of the concentration in use in different periods of time.Through the study of the main radiation performance,the influence of different structures on the measurement results is analyzed and compared.ResultsThe main results of this study are as follows(1)The results of etching experiments show that the number of net tracks measured when the etching time is 3h,the concentration of NaOH etching solution is 7 mol/L,and the etching temperature is 80? is about 40.7%higher than the etching conditions recommended by the company.Among them,there are three factors that affect the net track density by range analysis,the biggest one is etching temperature,and the smallest one is etching time.(2)It is found that the lower detection limit and the better time accumulation linearity of polytetrafluoroethylene(PTFE)membrane as radon dosimeter membrane are lower,and the better choice of PTFE membrane as radon personal dosimeter membrane is.(3)It is found that the conductivity,size,shape and filtering method of the radon dosimeter shell will affect the monitoring results in the comparative experiment of seven radon dosimeters.It is suggested that the radon dosimeter shell should be made of conductive plastics.The gap type radon dosimeter is suitable for the structural design of cylinder with large diameter and short height,while the filter membrane type radon dosimeter is more suitable for the structural design of hemispherical with small diameter and short height.Conclusion(1)The best etching condition of the detector is that the etching time is 3h,the concentration of NaOH etching solution is 7 mol/L,and the etching temperature is 80?.Among the three factors that affect the net track density,the most obvious one is the concentration of etching solution,and the least one is the etching time.(2)The filter membrane material of the filter membrane type radon dosimeter is the main reason affecting the monitoring results.In the experiment,the PTFE filter membrane is better as the filter membrane of the radon personal dosimeter.(3)The main characteristics of radon dosimeter,such as its shell conductivity,shape and size,can affect the monitoring results.Radon dosimeters with different characteristics can be selected according to different monitoring environment and site requirements. |
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