核废物桶放射性探测的层析γ扫描技术

Tomographic Gamma Scanning Technique for Radioactivity Detection of Nuclear Waste Drum

介绍了用于非均匀放射性核废物无损测量层析γ扫描技术的原理和方法,并对标准200 L核废物钢桶样品进行了实际测量,采用152Eu作为透射源而实现了层析γ扫描重建的全过程,采用极坐标的体素划分形式和MCNP程序对系统进行效率刻度,分别采用代数迭代法和最大似然重建算法进行了透射和发射重建,得到了线性衰减系数与活度的分布图,并与分段γ扫描的测量结果加以对比.结果表明,层析γ扫描技术的重建结果明显好于分段γ扫描,其与真实值的偏差在10%以内,从而验证了极坐标划分和重建算法的可行性.

The principle of tomographic gamma scanning（TGS） method for nondestructive assay of heterogeneous radioactive waste was described.An experiment of a 200 liter drum detection was conducted using the radioisotope（）～（152）Eu as the transmission source.A polar voxel representation was used,and the efficiency matrix was calculated by MCNP codes.The algebraic reconstruction technique and maximum likelihood expectation-maximization method were adopted for transmission and emission reconstruction to get the distribution of linear attenuation coefficient and radioactivity,respectively.The TGS results are obviously better than segmented gamma scanning（SGS） results,fitting the real activity very well with a relative error less than 10%.The results indicate that the polar voxel representation and reconstruction algorithms are feasible.