Effect of Silver ions in dichromate dosimetry

Abstract

Dichromate solutions containing silver ions have been investigated for use in dosimetry. The marked effect of hydrogen on the 60Co γ radiation-induced reduction of potassium dichromate solutions is completely inhibited by 1 × 10 −3 M silver nitrate. A silver nitrate concentration of 1 × 10 −4 M significantly improves the linearity and precision of response of dichromate to radiation, probably by inhibiting impurity effects as well as the hydrogen effect. G(−Cr 2O −2 7) values are given for a number of solutions containing different concentrations of silver and dichromate ions and sulphuric acid, for the measurement of doses up to 10 Mrad. The G(−Cr 2O 2− 7) value decreases with increasing silver ion concentration and increases with increasing dichromate ion concentration. No difference was found between the response of solutions prepared using singly distilled water and those using triply distilled water. Simple empirical equations are given for the calculation of dose from the absorbance of solutions. The mean error for doses in the range 0.3–4.2 Mrad, estimated with solutions containing 1 × 10 −4 M silver nitrate, was ± 1.5%; for doses of 1–9 Mrad from solutions containing 1 × 10 −3 M silver nitrate, the mean error was ± 0.9%. Spectrophotometry at 350 nm on an undiluted solution of 4 × 10 −4 M K 2Cr 2O 7/1 × 10 −4 M AgNO 3/0.4 M H 2SO 4 allows measurements in the range 0.08 to 0.80 Mrad; the G(−Cr 2O 2− 7) value for this solution was 0.37 ± 0.001.