Design And Development Of Environmental Radiation Monitoring And Localization System

In recent years nuclear safety and environmental nuclear radiation level is drawing moreand more attention with the rapid development of nuclear technology. It’s significantlyimportant to develop an environment radiation monitoring system (RMS), since it haswide application in many areas such as store and transporation of the radiation sources,disposal of nuclear waste, anti-terrorism, radiation detection in public transportation,radiation detection and monitoring in sectors such as nuclear power plants, laboratories,PET and CT in hospital and so on. γ-surveymeter is widely used to detect and locate theremovable radiation source in traditional system. Environmental radiation monitoringsystem which is able to localize the radiation source can not only get the dose rate of thedetector’s site but also give the location of the radiation source. It’s helpful to people tosearch the radiation source and waste. There is no such system developed in China. Thereare some studies and productions of localizing radiation source with γ-camera abroad,but γ-camera is inadequate for localizing radiation source in RMS since its narrow angleof view, low detection efficiency and additional complex system. I analy the radiation fieldmodel and designed the environmental radiation monitoring and localization systemframework in this thesis. I also realized the system including the detector, the DAQ andthe radiation source localization system.It’s well known that the traditional scintillation detector which is made up of NaI(Tl)coupling to PMT requires high voltage supply and is large and fragile. I use a newphotoconducting device which is called SiPM. It is coupled with the high density BGOscintillation to build the detector. Much more flexibility and detection efficiency areobtained due to its high integration density and high linear attenuation coefficient.I analyed the radiation field model and got the location of the radiation source withNewton iteration method. A5.6cm spatial resolution is obtained with our environmentalradiation monitoring and localizaion system. I developed a new directional detector basingon the scintillation arrays to localize the radiation source in a better way. Because γ-raywould attenuate while it goes through the scintillation, the detector near the radiationsource will get more counts of γ-ray. The direction of the radiation source is revealed by the distribution of the γ-ray detected. I have proven by simulations and mathematicalmodels that the vector between the scintillation’s geometric centre and the distributioncentroid of the detecting γ-ray would point the direction of the radiation sourceapproximately. I got a2.94angle resolution on average from the whole vision angle. Thismethod has lots of advantages, such as the high detection efficiency and the360-degreedetecting vision angle. It is very suitable to the environmental radiation monitoringsystem.