Study On The Application Of Vehicle Gamma Ray Spectrometry In Radioactive Source Search

This topic comes from the National 863 project theme project "High Precision Spectrum Detection Instrument Development"(project number: 2012AA061803).Vehicle gamma ray spectral survey refers to the gamma spectrometer placed the gamma ray energy and intensity in the region in the mobile platform,and identify the type and content of radionuclide method,usually used in environmental radiation monitoring field,and assume the task of radioactive prospecting.In the radiation environment monitoring vehicle,gamma spectrometer is mainly responsible for collecting the background data,the abnormal situation,the radioactive source search,statistics,statistical distribution of dose rate of radionuclide identification and distribution of radioactive plume tracking,environmental monitoring and nuclear emergency monitoring task.At present,in the application of environmental radiation monitoring,data analysis and interpretation of experimental vehicle gamma ray spectral lags behind the airborne gamma ray spectrum,has long been regarded as the gamma dose rate instrument used for vehicle gamma ray spectral study on the influencing factors of less in practical measurement,related literatures are mostly theoretical derivation,data support.Based on a vehicle gamma spectrometer,the applied research is vehicleried out.According to the attenuation of gamma ray radiation distribution theory and in a variety of media,described the crystal between the shielding thickness and the chassis of the vehicle instrument placed high impact on the measurement results;according to the test of single crystal detector sensitive area,put forward the vehicle gamma detecting ability distribution,and establishes the speed and detection of boundary relations.On the basis of the above research results,this paper establishes a set of practical guidance scheme for the source guidance by avoiding the shielding factor and implementing the source finding experiment.Research shows that the location and height of instrument is the key to affect the search efficiency of the radiation source,the main design and a few part of theexperiment:(1)through single crystal detector test,discusses the relationship between the large crystal energy resolution and point source position,detection distance from the vehicle in the longitudinal direction of gamma system is near and around the direction is far,and the week as the FCL capacity and internal crystal crystal shielding effect.(2)the experiment of the gamma ray spectrum measurement with the height of different instruments is vehicleried out.The results show that if the 80% photon flux is taken as the boundary of the vehicle gamma system,the recommended height is 3M,and the speed is not more than 35km/h.If the 90% photon flux ratio as the resolution boundary,when the instrument height is 0.5m in the 1.8 detection angle can be guaranteed under the scanning area 10 m wide,more than this range will lead to lower detection efficiency and the detection area is expanding rapidly.(3)to vehiclery out the source test,and make sure the recommended installation height of the vehicle gamma ray spectrometer,and get the minimum detection limit of the specific radiation source under the corresponding altitude LLD.