Numerical modeling of radiation-induced reactions: Fricke dosimeter at 298 K, 198 K, and 77 K

Abstract

The Fricke dosimeter is a widely used gamma radiation dosimetry system. The system is based on the detection of Fe2+ to Fe3+ oxidation in an aqueous solution of ferrous sulfate in sulfuric acid, exposed to ionizing radiation in the presence of oxygen. The system is formed by a series of highly dependent chemical reactions. We developed a numerical model of coupled differential equations based on the mass balance; each equation incorporates information about the formation and breakdown of each molecule, as well as a term that represents an external source of radiation. The numerical model can reproduce the behavior of the experimental data at room temperature. We proposed a correction factor to simulate the behavior of the dosimeter at temperatures of 198 K and 77 K, respectively, when the system is in a thermal bath of dry ice or liquid nitrogen. This model could support a variety of experimental challenges for radiation at low temperatures in different fields of industry and could have relevance for astrobiology problems by offering the possibility of simulating reactions in comets and other exoplanetary bodies.