Research On Simulation And Detection Method Of Gamma Radiation Field

Background: Radiation monitoring is an important part of nuclear accident emergency response,and monitoring results provide important data support for personnel protection,situation analysis,consequence evaluation,medical rescue,etc.Routine radiation monitoring training is very important for improving the capability of radiation monitoring for nuclear emergency response.However,training with radioactive sources may cause certain health hazards to personnel or radioactive pollution to the environment.Therefore,it is difficult to use real radioactive sources in the training process.Due to the lack of real radiation environment,radiation monitoring instruments does not respond,and the training effect is not ideal.Through the establishment of virtual radiation environment and simulated radiation monitoring instruments,the simulated training system avoids the use of real radiation sources,eliminates the potential danger of safety,and can set up abundant training conditions according to various requirements,which is of great significance to improve the training effect of nuclear emergency medical rescue teams.Objective: Aiming at requirements of nuclear accident emergency simulation training,this study investigated gamma radiation field simulation and detection methods.The simulated gamma radiation source was developed to release the simulated gamma ray signal which conforms to the characteristics of gamma ray signal.Based on the diffusion law of radioactive plume and the geographic information system,a virtual simulation model of large-scale radiation field was established,and the virtual radiation field of radioactive contamination was generated according to the given accident scenario.An analog signal detector which can detect signals from simulated radioactive sources and virtual radiation field of large range radioactive contamination was developed,and a simulated radiation monitoring instrument was also developed.The main research contents and results are as follows:Research contents and results:(1)Study on radiation field characteristics and simulation method of sealed gamma source.The radiation field characteristics of sealed radioactive sources in a small space and the application status of sealed radioactive sources were analyzed,and the basic content and simulation training requirements of sealed radioactive sources detection training were summarized.According to the law of point source that dose rate is approximately inversely proportional to the distance square,and the comparison between advantages and disadvantages of various kinds of simulation methods,gamma rays simulated by radio frequency signals,and sealed radioactive sources gamma radiation field intensity changes simulated by ultra-wideband ranging technology was determined.Analog signal characteristics of the radiation field,signal coverage area,meet the demands of radiation monitoring training signal resolution.(2)Study on radiation field characteristics and simulation methods of major nuclear accident.Based on the analysis of radiation field characteristics of major nuclear accident and different types of accident scenarios,a simulation method of large-scale nuclear accident radiation field based on computer simulation model of wide-area radiation field was proposed.The basic needs of the radiation field simulation model were determined.By using the Gaussian diffusion model,dependence of the simulated the dose rate on variables such as source term parameters,environmental parameters,and diffusion model was analyzed.,Calculation formula of simulated dose rate was derived.Combined with GIS information system,a wide-area radiation field simulation model was developed,making it possible to generate widespread radioactive pollution virtual radiation field according to the different accident scenarios.(3)Development of simulated γ source.According to the radiation field characteristics of the sealed radioactive source and the simulation method of ultra-wideband technology,the simulated γ radioactive source was designed,which is mainly composed of hardware and software.The hardware part mainly includes the control circuit module and the analog signal transceiver module.The control circuit module adopts ARM processor,which is responsible for the processing of data signals.The analog signal transceiver module adopts DW1000 chip,which is responsible for the transceiver of RF analog signals.The control software of simulating gamma radiation source is developed to realize the control of signal sending and receiving.The experimental results show that the hardware and software design of the simulated γsource can meet the requirements of the simulated training system,and the simulated signal can be effectively covered in the area of 300 meters.(4)Development of analog gamma radiation monitoring instrument.Based on the analysis of the methods of detecting the analog signals of sealed radioactive source and wide area radiation field,an analog gamma radiation monitoring instrument which can detect the two kinds of analog signals was designed.The hardware of the instrument consists of control circuit module,analog signal transceiver module,input and output module,display module,GPS positioning module and wireless communication module.Taking FH40 G multi-function radiation monitor as the objective instrument,the application software program and the configuration of the simulated gamma radiation monitor instrument were designed.The experimental test results show that the simulated gamma radiation monitoring instrument can steadily detect the simulated radiation field signal within the signal coverage area of the simulated gamma radiation source and the large range of radiation field simulation model,,display response data in real-time,and finely simulate the radiation monitoring instrument operation process and data response characteristics.Conclusion: A method for simulating the radiation field of sealed source and large scale nuclear accident was established,and a simulated gamma radiation monitoring instrument was developed.For radiation field of sealed source in a small range of space,a simulated gamma radiation source was designed,which can release analog signals stably and continuously in a certain range of space.For radiation field of large-scale nuclear accident,the model of radiation field of nuclear accident was developed based on computer simulation,and the virtual radiation field of large-scale radioactive pollution can be generated by combining GIS system.An analog gamma radiation monitor was developed based on FH40 G multi-function radiation monitor,which can detect the analog signals generated in the above two types of radiation fields.The test results show that the above two simulation methods can produce simulated radiation field signals in accordance with the characteristics of real radiation field,and the developed simulated gamma radiation monitor can respond in real time in the effective area.The test effect reaches the expectation.The prototype can be used for nuclear emergency simulation radiation monitoring training after further improvement.