2247 - Verification of a Simulation Toolkit Step-By-Step Reaction Diffusion Master Equation Model for Long-Term Simulation of Radiolysis in Fricke Dosimetry
E. Yoon1, J. I. Kim2, S. Kang3, J. Jin2, H. Park2, and C. H. Choi2; 1Seoul National University, Seoul, Korea, Republic of (South), 2Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea, Republic of (South), 3Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea, Republic of (South)
Purpose/Objective(s): Calculation efficiency is a key factor in radiation chemistry simulation using the Monte Carlo method. Recently, a Step-By-Step-Reaction Diffusion Master Equation (SBS-RDME) model that can improve computational efficiency was implemented in a simulation toolkit, a Monte Carlo Track Structure (MCTS) code. In this study, we tried to verify the SBS-RDME model based on calculations using the Independent Reaction Time (IRT) method. Materials/
Methods: Radiolysis in Fricke dosimeter was simulated using a simulation toolkit. Including the Fenton reaction, reactions related to the oxidation of ferrous ions were added to the existing chemistry constructor, and the effect of acidity on reaction rates, known as ionic strength, was taken into account in reaction rate constants. The energy spectrum of the secondary electrons was sampled from 1 × 1 × 1 cm3 cubic water phantom with the gamma irradiation of 109 histories for both 1173 and 1332 keV. The sampled energy spectrum was used as the source for the Fricke dosimeter simulation. To mimic the Fricke dosimeter, 0.4 M of H2SO4, 5 mM of FeSO4, and 0.25 mM of O2 were added to a 204.8 µm sided homogeneous cubic water phantom. The isotropic electron point source was placed at the center of the Fricke dosimeter phantom, and 640 histories were simulated for up to 100 seconds. Finally, the time-dependent chemical yields of Fe3+ were evaluated as G-value. In the configuration described above, a simulation using the SBS-RDME model and the IRT method was performed, and the G-value at 100 s was compared. The experimental G-value of Fe3+ for Co-60 presented in ICRU report 34 was also compared. Results: The SBS-RDME model calculated the G(Fe3+) at 100 seconds as 15.97, while the IRT calculation resulted in 16.11. The agreement between the two calculations was within 0.9%. When compared to the ICRU report value, 15.5 ± 0.2, a discrepancy of 3% existed. Conclusion: The SBS-RDME model was verified using IRT calculations. Further investigation will be conducted for validation with experimental value.
