Year
1989
Abstract
The Savannah River Site operates two radiochemical separations areas to recover uranium and plutonium from nuclear reactor fuel and target assemblies. Chemical processes in these areas are controlled based on laboratory analysis of samples extracted from the process. While analytical results from the laboratory are reliable, the process of pulling samples, transporting them to the laboratory, analyzing them, and then reporting results is time consuming and potentially exposes many workers to highly radioactive solutions. To improve the timeliness of chemical information and reduce personnel radiation exposure, the Savannah River Laboratory (SRL) has developed online absorption spectrophotometers.Absorption spectrophotometers are rugged instruments which can provide precise, detailed information about chemical states and concentrations. However the technique is susceptible to interference from other optically absorbing species and changes in analyte absorbance due to different matrixes. Also it is difficult and expensive to interface absorption spectrophotometers to SRS's radioactive processes. SRL has developed an online fiberoptic spectrophotometer which substantially solves these problems by combining three new technologies, fiberoptics, diode array spectrophotometers, and multivariate data analysis.The analyzer monitors the uranium and nitrate concentration of seven aqueous process streams in a uranium purification process. The analyzer remotely controls the sampling of each process stream and monitors the relative flow rate through each sampler.Spectrophotometric data from the analyzer is processed by multivariate data analysis to give both uranium arid nitrate concentrations as well as an indication of the quality of the data. The precision and sensitivity of the instrument is 0.5 milliabsorbance units which translates to 20 ppm uranyl and 4 ppm plutonium. The accuracy of the PLS models is better than 2% of reading for concentrations above 1 gram per liter.