Implementation of the automated potentiometric titration method for total uranium at the CNEN Safeguard Laboratory, Brazil

The Brazilian nuclear facilities, in accordance with norm CNEN-NN-2.02, must dispose of measurement systems that allow determining its inventory of nuclear material. One in the ways to also evaluate and verify these systems can be made through the participation of the involved laboratories in interlaboratorial comparison programs. Based on this premise has been developing a project that aims to make possible to CNEN to characterize of uranium compounds for the use in national interlaboratorial comparison programs for measurement systems of nuclear material. The first step of this project, described in this work, was to implement a semiautomatic version of the potentiometric titration method for characterization of total uranium in the safeguards laboratory of CNEN. This method was used to determine total uranium with traceability assured by using a potassium dichromate primary standard. In the analysis was used analytical balances, automatic titrator, Pt:Rh (90:10) indicator electrode and mercurous sulphate (Hg/HgSO₄) reference electrode. All the procedures concerning the preparation and determination of total uranium concentration of standard solutions were converted to weight basis. The emphasis on automation of the method was the trend of reduction in analysis time and in the influence of the analyst. The goal of combined standard uncertainty in determining the concentration of total uranium in the order of 0.01 % was reached, which means that this technical study obtained an order of magnitude better compared to the methods traditionally used by nuclear installations. (author)