Mechanistic Study of The Acidic Aqueous Solution of Chrome Alum Chemical Dosimeter: Steady State, Pulse Radiolysis and Conductivity Studies

It is crucial to have an efficient and reliable approach to ensure an optimum traceability in high dose range and high dose rate dosimetry for radiation processing (food irradiation, surgery devices sterilization…). Chemical solution dosimeters are well suited for this purpose. By using γ-irradiation and pulse radiolysis, we evaluated the performances of the chrome alum KCr(SO4)2·12H2O based on the radiation induced oxidation of Cr3+ to Cr6+ in N2O-saturated aqueous solutions buffered at pH 4 by the hydroxyl radical (•OH). With combination of spectrophotometric and conductometric measurements, a mechanism has been put forward to elucidate the oxidation of Cr3+ leading to Cr6+. The suggested mechanism involves an initial adduct formation, [Cr3+ – •OH], that enables inner-sphere electron transfer. As far as dosimetry is concerned, this study showed that the absorbance at 350 nm of the radiation induced Cr6+ increases linearly with the dose with a yield of G(Cr6+) = 0.128 μmol J-1. No dose rate effect was observed up to 80 kGy min-1. This aqueous solution could be used for chemical dosimetry, mainly in the high dose range (up to 5 kGy) and high dose rate (up to 80 kGy.min-1). The main advantage of using this aqueous solution is its equivalence to human tissue in terms of radiation absorption properties.