Continuous Measurement of Radioactive Isotopes Isolated by an Automatic Analytical Process

INTRODUCTION In an attempt to improve the radioisotope analyses made in our laboratory on the products of fission mixtures, we attempted the replacement of the classical radiochemical methods (separation, then measurement) by automatic methods in which a more sophisticated analytical process is followed by on-line measurement utilizing Cerenkov counting. In the classical methods which are often manual, it is necessary to determine the chemical separation efficiency. This difficult determination is made by different techniques such as gravimetry, absorption spectrometry, etc. and when radiometric measurement is made (f3 or 'y technique) the counting rate so obtained must be corrected and one is forced to consider factors such as detection efficiency, self-absorption and coefficient of geometry, decay scheme and radioactive equilibrium, quenching, etc. In order to avoid these disadvantages we are conducting research, the object of which is the production of a liquid phase radioanalyser in modular form, allowing the continuous analysis of radioisotopes as they become isolated. Figure 1 shows a block diagram of the radioanalyser. The separation unit at uniform concentration is designed around an analytical process, the object of which is to isolate one or more chemical elements. The detection unit which uses Cerenkov detection analyses online the corresponding radioisotope and the measurement is performed versus a standard of activity of the same radioelement, treated under identical experimental conditions. After a short examination of the analytical methods used in the separation unit, we describe the technique employed ii the detection unit and give some examples of its application.