Study Of How To Improve The Accuracy Of Sgs System Based On The Scale Of Detecting Efficiency

There are mass of un-known radioactive nuclides in the produced low and medium level radioactive waste.Inside the radioactive waste drum,filling materials and the radioactive stuff distribute complexly,which leads that the mean density of waste drum fluctuate seriously,the hyper-dispersion of spatial distribution inside the drum and physical and chemical form inside the drum complex.As a result,it is unrepresentative to use the traditional sampling and chemical analysis method to measure the radioactive waste drum.At present,Non-Destructive Assay(Short for SGS)is usually used to measure the radioactive waste drum.Among which,Segmented Gamma Scanning is the most common technique.For Segmented Gamma Scanning,the scale of detecting efficiency is the critical process.During the measuring process of SGS,the radioactive waste drum rotated at an average speed,the point source can be considered as an annular source.The different detecting efficiency of annular source with each radius is the most important reason which brings error to SGS.Therefore,some specialists proposed an improved Segmented Gamma Scanning method,this method can obtain the equivalent radius of annular source by measuring with two detectors,and then rebuild the activity of radioactive nuclides by calculating the detecting efficiency of each annular source.Such method improves the accuracy of SGS system in case that there is limited point source in the waste drum.This assay will study the law how the detecting efficiency changes along with the radius,firstly infers a numerical formula of detecting efficiency,and then analyzes how the eccentric distance between detectorand waste drum impacts the accuracy of SGS system,finally mention a new measuring way to improve the accuracy of SGS system.This study is provided with both scientific significance and practical engineering value.The main contents and achievements are shown as below:(1)Studies on laws of how the radioactive source posited on different radius impacts the accuracy of detecting efficiency for the traditional SGS system.(2)Studies on how the eccentric distance between detector and waste drum impacts the accuracy of detecting efficiency in different measuring conditions.(3)Inferring a numerical formula to calculate the detecting efficiency in different measuring conditions.Verifying the veracity and reliability of the formula by Monte-Carlo method and experiments.With which formula,the calculation of detecting efficiency won’t be impacted by the shape of collimator.(4)Directing at different conditions,coming up with the corresponding best eccentric distance between detector and waste drum which can improve the accuracy of SGS mostly.