Evaluation of the Fricke solution-PMMA interaction and its influence in Fricke dosimetry

The Fricke dosimeter is a chemical solution whereby oxidation of ferrous ions to ferric ions occurs when submitted to ionizing radiation. The absorbed dose in the Fricke solution is obtained by reading the optical density of the solution after it is irradiated, subsequently, converted to the absorbed dose to water by using a conversion factor. However, chemical oxidation in the solution can occur even in the absence of the ionizing radiation. The interaction between the Fricke solution and the PMMA walls of a new holder for a period of time was evaluated in this study. This work demonstrates that the effect of this interaction is not negligible and can cause a systematic uncertainty of the final results if used in the first months after the holder is manufactured. After this, the reaction stabilizes making the PMMA material suitable for the Fricke dosimetry. (author)