Spur diffusion model for radiolysis of aqueous solutions

A computer model which simulates the simultaneous reaction and diffusion of chemical species resulting from the radiolysis of aqueous solutions was updated and improved. This model numerically solves the deterministic rate equations for the deaerated Fricke dosimeter (dilute ferrous sulfate in sulfuric acid). Based on a review of the literature, the model results were compared to other models and experimental data. The model was improved by the addition of an algorithm to determine the optimum timestep. This decreased the execution time of the model significantly with less than a 5% difference in the yield results. It was determined that the model does not correctly describe scavenger reactions and only accurately reflects experimental results during the period of spur reactions (1 ps to 200 ns). The model results for long term yields of Fe⁺³ and H₂ were within 10% of experimental values. The G values, the number of species produced per 100 eV of energy absorbed, determined from the model were 8.6 for Fe⁺³ and 4.1 for H₂. Agreement with experimental data can be improved by adjusting several parameters in the model.