Fig. 1. Schematic diagram of horizontal level measurement of waste drum

Fig. 2. Schematic diagram of circumferential mesh merging(a) Traditional meshing, (b) Circumferential mesh merging and partitioning

Fig. 3. Schematic representation of radial meshing with different exponential weights

Fig. 4. Variations of line source efficiency with radius under different measurement conditions

Fig. 5. Schematic diagram of voxel division optimization method

Fig. 6. Schematic diagram of traditional voxel division(a₁) 2×12, (a₂) 2×18, (a₃) 2×24, (b₁) 3×12, (b₂) 3×18, (b₃) 3×24, (c₁) 4×12, (c₂) 4×18, (c₃) 4×24

Fig. 7. Diagram of random distribution of radioactive sources

Fig. 8. Reconstruction error statistics under bipartite division of voxel radial

Fig. 9. Reconstruction error statistics under voxel radial tripartite division

Fig. 10. Reconstruction error statistics under voxel radial quadripartite division

Fig. 11. Reconstruction error statistics for voxel partition optimization methods

Fig. 12. Diagram of point source distribution at voxel boundary

Fig. 13. Trend diagram of activity reconstruction error with radius variation

Fig. 14. Count rate deviation of different voxel partitions