Study of the analytical performances of an optical multi-fiber spectrophotometer for the simultaneous online analysis of uranium and plutonium

The study consists in determining limits of use of an optical multi-fiber spectrophotometer. The latter analyses both uranium and plutonium simultaneously. The study is aimed at giving concentration values of actinides in solution with error intervals. Two causes of error were considered for solution analysis: - error in concentration calculation due to the treatment method called PLS; - error in measurement of intensity of light due to instrumentation. Error percentage in concentration due to PLS method was estimated for mono-elementary solutions of uranium at IV and VI oxidation degree with different concentrations. It was also estimated for mono-elementary solutions of plutonium at III and IV oxidation degree. Then, error percentage in concentration due to instrumentation was estimated from an approximation model. The latter was calculated for solutions such as those quoted before. Nevertheless, experimental estimation of this error percentage for mono-elementary solutions of uranium VI showed limits of approximation models created. Moreover, a second type of sensors used for solution analysis involves a wrong calculation of concentrations higher than a limit value. The limit value is about 30 g l^-1 for solutions of uranium VI. A study showed that optical technology of this sensor was important because of the changing of the refractive index of solutions when their concentration increases. Highly concentrated solutions of uranium VI can eventually be analysed with a new type of sensor which was developed after the study. Performances of the new sensor are the same as performances of first sensors designed. Therefore, solutions of uranium VI with concentrations higher than 70 g l^-1 cannot be analysed properly at present only because of PLS treatment model created. (author)