半层析γ扫描技术(Semi-tomographic Gamma Scanning, STGS)在综合分段γ扫描技术(Segmented Gamma Scanning, SGS)和层析γ扫描技术(Tomographic Gamma Scanning, TGS)的基础上,对其测量方法和重建算法进行了改进.用STGS方法测量核电厂废物桶活度是在SGS基础上,将废物桶轴向分段的每层进一步划分为数个环状体素,然后采用拓扑层析方法进行活度重建.针对包含三种放射性核素的400 L超压废物桶,蒙特卡罗方法被用于验证STGS方法的正确性.结果显示:SGS对高密度400 L废物桶的最大测量误差超过100%,而STGS的重建误差和统计偏差可控制在50%以内,且往往是SGS方法的二分之一或更低.而测量时间显著短于TGS.从整体上讲,STGS是一种平衡了精度和测量时间,测量高密度400L废物桶的有效方法.%[Background] Segmented gamma scanning (SGS) and tomographic gamma scanning (TGS) are the normal standard non-destructive assay (NDA) techniques for low intermediate waste drum detection. [Purpose] This study aims to evaluate the performance of semi-tomographic gamma scanning (STGS) for waste drum of nuclear power plant (NPP). [Methods] The principles of SGS and TGS are synthesized in the STGS method and the implementation of its algorithm, each segment of the waste drum is divided into annual voxels and tomography is used in the radiation reconstruction. The accuracy of STGS is verified by MCNP calculation for the 400 L standard waste drums which contains three types of nuclides. The cases of point source and uniform materials are employed for comparison. [Results] The experimental results show that the reconstruction error and statistical bias for STGS can be controlled lower than 50% and is always half or less of SGS while maximum error of SGS is over 100%. The detection time of STGS is obviously shorter than TGS. [Conclusion] STGS can keep the balance between accuracy and detection time, it is an effective method for non-destructive assay of 400 L radioactive waste drums with high density.
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