Fig. 1. Computational flowchart of the numerical simulation

Fig. 2. Pipe model and measurement positions of dose rate

Fig. 3. Ditribution of measured points (a) Test set, (b) Training set

Fig. 4. BICs of each activity distribution model (a) and activity distributions (b)

Fig. 5. RD distributions under two reconstruction methods (color online) (a) λ=1, (b) λ=2, (c) λ=3, (d) λ=4

Fig. 6. Diagram of scene model and distribution of rate measurement points

Fig. 7. BICs of each activity distribution model

Fig. 8. Results by our method of RD at each point in the test set (a) and frequency distribution histogram of RDs (b) (color online)

Fig. 9. Results by ordinary kriging interpolation of RD at each point in the test set (a) and frequency distribution histogram of RDs (b) (color online)

Fig. 10. Scene model and 3D radiation field (color online)