In-Line Determination of Uranium, Plutonium and Acidity in Spent Fuel Reprocessing for Process Monitoring on Advanced Nuclear Material Verification

Two analytical technologies, i) electrochemical method; combining differential pulse voltammetry with electric conductivity or ultrasonic wave velocity measurement and ii) spectrophotometric method with optical fiber have been developed at the Tokai reprocessing plant (TRP). Purpose of the development is to improve process and remote monitoring system, as well as in-line analytical methods to determine operational parameters such as uranium, plutonium and acidity in PUREX plant. Both analytical methods had been applied to determine operational parameters just inserting small detection devices into solution. These systems are consisted of simple instrumental components. Current peaks of uranium and plutonium were obtained by small glassy carbon and gold electrode probe, whose intensity is linearly proportional to their concentrations in the range from 1 to 170g L-1 and from 1 to 25g L-1, respectively. The quantitative range of uranium acquired by immersion spectroscopic probe is nearly the same as that obtained by the voltammetry. Absorption peak ratio of uranium over 8g L-1, measured by in-line spectrophotometry appeared relation with respect to the acidity ranging from 0.2 to 5M. Ultrasonic wave velocity and electric conductivity in solution are related to acidity. The electric conductivity method was used measurement of the acidity less than 3M, whereas, ultrasonic wave velocity method was adapted in the range from 1 to 6M. These results of each method was successfully applied for in-line determination of uranium, plutonium and acidity in reprocessing solutions with precision less than 5% as relative standard deviation. (author)