Research On Depth Measurement Methods For Radioactive Sources

During the operational cycle of nuclear facilities,a large amount of radioactive waste is generated.These radioactive waste seeps into the concrete over time,and traditional depth analysis methods include logging,micro drilling,and core sampling.However,these methods are destructive and time-consuming.Therefore,choosing a low-cost and effective depth analysis measurement method is crucial for the penetration depth of radioactive waste and the depth positioning of radioactive sources.This article mainly adopts a method based on theγray attenuation that measures the depth positioning of radioactive sources.Geant4 was used for simulation and experimental detection processing,and relevant conclusions and influence deviations of the depth measurement of radioactive sources were obtained.Firstly,the theory of this approximate three-dimensional relative attenuation measurement method was introduced.Secondly,Geant4 was used to simulate and analyze the impact of different unit detection scanning areas of line array and surface array,as well as different total detection scanning areas of surface array,on the accuracy of depth positioning of radioactive point sources,providing reference for subsequent experimental measurements.Finally,9 detectors were fabricated using 9 MPPC devices coupled with Cs I（Tl）scintillation crystal packaging,and corresponding power supplies were designed.After testing the detector power circuit,detector signal acquisition and processing,and energy spectrum measurements of relevant radiation sources were carried out.This detector can achieve experimental measurement of radiation source depth,identify different nuclide radiation sources,and has advantages such as small volume,low working voltage ratio,and good time response.At the same time,the attenuation coefficients of different radiation sources in uniform fine sand were measured,and the influence of detection time,detection area,and other factors on the depth estimation of radiation source depth positioning was studied using the constructed radiation source depth measurement platform.The simulation results indicate that this method can detect the depth of a 40 cm buried radioactive point source in uniform fine sand.In addition,experimental measurement estimates The activity 3.925×10⁵ Bq of ¹³⁷Cs radiation source,this method can measure and estimate a depth of 12 cm.The activity 7.1×10³ Bq of ⁶⁰Co radiation source,this method can measure and estimate a depth of 4 cm.The lower maximum depth recorded in the experiment is due to the average detection performance of the self-developed detector and the lower activity of the ¹³⁷Cs and ⁶⁰Co radioactive sources used.However,both results indicate that this method has superior capabilities compared to other existing methods.