Study On Segmented Gamma Scanning Technique Of Efficiency Calibration Method For Low And Intermediate Level Radioactive Waste

The radioactive detection of drummed nuclear waste is an indispensable link in the process of nuclear waste recovery,treatment and disposal.Segmented Gamma Scanning(SGS)is a Non-Destructive Assay(NDA)technique.It is economical,convenient and most effective method for qualitative and quantitative analysis of radionuclides in the storage of low-and medium-level radioactive waste.In the actual analysis process,due to the uncertainty of the position of the radionuclide,the detection efficiency corresponding to each position at each segment will change.There is a large error factor in the quantitative analysis of radionuclide activity in the entire radioactive waste drum.Therefore,the detection efficiency of the HPGe detector corresponding to the position under each radius in the radioactive waste drum should be corrected separately.This reduces the error in the radionuclide activity analysis process.In this paper,the geometric factor correction of the HPGe detector in the collimator response function,the correction of the point source relative attenuation distance,and the correction of wedge-disturbing between segments are involved.In this paper,a uniform density polyethylene cylinder block was used as the filling medium in the drum for experiments.The efficiency calibration is according to the shell source model.The distance from the center of the drum to the outside is selected from the inside to the outside,and 7 different rotation radii are selected,which are marked as positions 1-7.The radioactivity point source was placed in the drum at different rotation radii to test the efficiency of the experiment,and then using the geometric factors of positions 1-7 to give the weighted average of the results of the detection efficiency and give the standard value of the detection efficiency of each segment.Experimental verification by this method shows that this method can fully estimate the detection efficiency of radionuclides at different positions in each segment.The above work is based on the fact that the radius of radionuclides is known.Therefore,point source positioning analysis must be performed before the detector efficiency calibration.That is,the point source position is determined by analyzing the bipolar points in the relation curve between the rotation angle and the counting rate of the waste drum,and then the subsequent efficiency calibration and experimental analysis are completed.The results show that under the conditions of measurement and calculation errors,radioactivity of radionuclides in different positions in the radioactive waste drums can be accurately estimated and the detection accuracy can be improved.