Use of the dichromate solution as a dosimeter for high dose and high dose rate

The radiolytic reduction of Cr(VI) in N₂O-saturated aqueous solutions has been investigated over a large range of pH by steady state radiolysis. At pH 3 in the presence of formate as scavenger for ·OH, G(−Cr(VI)) is higher than the expected yield and a strong dose rate effect is observed. The solution cannot be used for dosimetry at this pH. The proposed mechanism to explain the enhanced response and the dose rate dependence involves the reduction of the unstable radiolytically produced Cr(IV) by HCO₂⁻. At pH 9.2 the reaction between Cr(IV) and formate is absent and no dose rate effect was observed up to 70 kGy min⁻¹, which makes this system particularly attractive as a dosimeter in the 0.1–10 kGy dose range. Radiation chemical aspects relating to the use of this system as a high-dose and high-dose rate chemical dosimeter are discussed.