Accurate analysis of secondary references for the measurement of fissionable materials

Titrations of the oxidation-reduction type are used either as a method of measuring fissionable materials in cases where the product being analysed is of sufficient purity, or as an isotope dilution calibration method in the case of irradiated fuels containing numerous interfering elements. The results described in the paper refer to uranium and plutonium. In the effort to achieve accuracy account is taken of three factors: the experimental conditions under which dissolving and titration take place; the quantitative characteristics of the reactions and the possibility of systematic errors; the chemical behaviour of the neptunium and americium present in the plutonium in small quantities. With the operational procedures used, accuracies ranging between 0.02 and 0.1% can be attained, depending on the individual case. The authors conclude that a programme of research on the transuranium elements must be pursued if accurate analysis of future fuels is to be possible. (author)