A comparison between experimental results and a mathematical model of the oxidation reactions induced by radiation of ferrous ions

The dependence of the response of chemical dosimeters as a function of the irradiation temperature is an important issue that has not yet been addressed within a mathematical modeling framework. The temperature dependence of the dose–response function has to be taken into account in practical applications, mainly in frozen food sterilization by radiation. Significant errors may occur if the dependence of the dosimeter response on the irradiation temperature is not taken into account properly. The experimental results obtained irradiating iron salt solutions at different temperatures below and above 0∘C show that the change in the valence of Fe2+Fe2+ as a function of dose are linear for both liquid and frozen solutions. This led us to conclude that the iron salt solution seems suitable for low-temperature applications having a linear dose–response up to 600 Gy, despite a progressive decrease of sensitivity as temperature decreases. A nonlinear differential model for the kinetics of reactions induced by radiation in iron salt solutions was established. In the model a temperature correction factor was included in order to take into account abrupt changes observed in the kinetics of the chemical process when the irradiated solution's allotropic phase changes from liquid to solid (ice). Fitting the kinetic model to the experimental results at different temperatures we found the temperature correction factors.