Absorbed dose rate dependence for PEO-Fricke dosimeter using sodium thiocyanate as indicator

Fricke solution, composed of ferrous ammonium sulfate in an aqueous sulfuric acid medium, is widely used as a chemical dosimeter for the quantification of radiological parameters such as exposure, kerma, and absorbed dose. The conventional Fricke dosimeter has been modified by the addition of a gelling agent to allow three-dimensional absorbed dose measurements. Additionally, the incorporation of ion indicators, as xylenol orange, improves gel stability and enables the use of optical analyzers for dosimetric calculations. In this study, the response of a Fricke gel dosimeter using polyethylene oxide (PEO-Fricke) as a gelling agent and sodium thiocyanate as an ion indicator was investigated as a function of absorbed dose rate, in the range from 1.78 × 10² Gy h^-1 to 1.19 × 10³ Gy h^-1, in a cobalt-60 gamma radiation field. The dosimetric response of the PEO-Fricke formulation was evaluated by spectrophotometry and compared with a conventional Fricke gel based on porcine gelatin and xylenol orange (FXG). The results showed that the PEO-Fricke dosimeter exhibited a maximum variation of approximately 5.2 % in its spectrophotometric response as a function of absorbed dose rate, while the FXG formulation presented a variation of approximately 1.3 % over the same range. In addition, the PEO-Fricke dosimeter showed a linear absorbed dose response between 5 Gy and 150 Gy. These results indicate that the proposed PEO-Fricke formulation with sodium thiocyanate is a promising alternative for three-dimensional dosimetry and high-dose irradiation applications.