Preliminary Study on Human Dose of X and Γ Flaw Detection Accident Based on FLUKA

Mock object

The simulation was based on the Chinese male reference human body model developed by Tsinghua University [6, 7]. The phantom, which was 1.76 meters tall and 60 kg in weight, contained 103 tissues or organs. This phantom had been also applied widely in the field of radiation protection [8, 9], in order to study on the energy deposition and dose distribution of various tissues and organs of the human body who was irradiated by X-ray, Cs-137 and Co-60 radiation sour.

Calculation Method

In this study, we firstly converted the reference human body model into the voxel structure files that could be recognized by FLUKA [6, 7, 10], and then the simulated space structure and human body materials were constructed using the flair program of the FLUKA software [11]. When modeling, circular radiation fields of 200 keV and 300 keV X-ray were set to irradiate the human chest with a radiation field diameter of 10 cm. Besides, the distance between the Cs-137 or Co-60 radiation source and the human body was set to be 1 cm, and the surrounding space was set as an air sphere with a diameter of 1000 m. The number of simulated particles was 1×108.

Quality control

After the Fluka-based model was successfully debugged, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, 0.80, 1.00, 2.00, 4.00, 6.00, and 10.00 MeV X-ray was simulated to isotropically irradiate human body model. The simulation results were compared with that of reported work based on GEANT4 [4] and the deviation was less than 5%.

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Dose distribution

The 200 keV X-ray, 300 keV X-ray, Cs-137 and Co-60 radiation sources were respectively simulated to directly irradiate the human body. Then, the spatial distributions of absorbed dose for human body could be got, which were shown in Figure 1 and Figure 2, respectively. When 200 keV and 300 keV X-rays irradiated human chest, the energy deposition was high in the tissues and organs of the chest region. Among them, the absorbed dose of the lung was the highest, and the area in the irradiation field reached the maximum, followed by the heart and liver that were closer to the lungs. When Cs-137 and Co-60 radiation sources were simulated to irradiate the human body at close range, the spatial distribution of the absorbed dose of the human body was generally the same as that of 200 keV and 300 keV X-rays irradiation.

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Energy Deposition and Absorbed Dose in Major Organs

The simulated results of energy deposition in 103 tissues and organs of the human body were statistically analyzed. The top 5 organs of energy deposition were lung, heart, muscle, soft tissue, liver, and skin. The energy deposition of the five organs and the whole body was listed in Table 1, whose unit was GeV/photon. The top 5 organs of energy deposition at each energy point of X ray were the same. The masses of lung, heart, muscle, soft tissue, liver, skin and whole body used in simulation calculation were given in Table 2.

To obtain the absorbed dose of organ in unit of Gy during single photon irradiation, the energy deposition per unit mass of the organ should be obtained firstly, that is, divide the organ energy deposition data in Table 1 by its mass, and then multiply it by 1.602176462×10-7, the absorbed dose of each organ could be obtained [10]. The absorbed doses of lung, heart, muscle and soft tissue, liver and skin were shown in Table 3. Among them, the lung had the largest absorbed dose, followed by the heart and liver, while the skin, muscle and soft tissues had the third highest absorbed dose.