双探测位置螺旋γ扫描技术研究

Research on two-measurement position helical gamma scanning technology

为了解决螺旋γ扫描技术(Helical Gamma Scanning,HGS)在放射性核素不均匀分布时测量精度差的问题,提出了基于双探测位置测量的螺旋γ扫描技术(Two-measurement Position Helical Gamma Scanning,THGS)。THGS在HGS的基础上,增加了一个偏心位置的螺旋扫描测量,由两个位置的计数率比值,确定放射性废物桶内放射源的等效半径,重建其活度。通过数值计算方法,模拟三种放射性核素在400 L放射性高密度废物桶中的重建过程,验证了THGS重建结果的准确性。结果显示:HGS对高密度400 L废物桶内单线源的最大重建误差超过400%,而THGS的重建误差控制在50%以内。采用双探测器测量,THGS的测量时间与HGS一样。整体而言,THGS适用于高密度400 L放射性废物桶的测量。

[Background]Helical gamma scanning(HGS)is one of non-destructive assay(NDA)for the measurement of radioactive waste drum.However,the accuracy of HGS in measuring the heterogeneous radioactive waste is poor.[Purpose]This study aims to evaluate the performance of two-measurement position helical gamma scanning(THGS)for a 400-liter high density waste drum.[Methods]On the basis of HGS,THGS adds eccentric helical scanning measurement.The equivalent radius of the radioactive source in the waste drum was determined by the ratio of the counting rate of the two positions.Finally,the activity of the radioactive source was reconstructed.The reconstruction process of three radionuclides in 400-liter waste drum was simulated by numerical calculation method to verify the accuracy of THGS.[Results]For a single line source in high density 400-liter waste drum,the maximum reconstruction error of HGS is more than 400%,while that of THGS is less than 50%.When two detectors are used,the measurement time of THGS is the same as that of HGS.[Conclusions]THGS is suitable for measuring 400 L-waste drum whose density is high.