J. Miller “Investigation of Trace Uranium in Biological Matrices”, Ph.D. Dissertation, Nuclear Engineering, Texas A&M University, College Station, TX (2013).
A system for the analysis of urine bioassay samples for the purpose of inversely investigating an unknown exposure has been developed. This technique involves the use of a thin flow electrochemical cell in conjunction with an anodized glassy carbon electrode to selectively separate uranium atoms out of solution for later analysis on an inductively coupled plasma mass spectrometer. A series of uranium urinalysis bioassay sample results can be used to investigate the time frame and type of exposure. This analysis uses an exposure database and regression analysis to best fit urinalysis uranium excretion data to expected profiles using commercially available mathematics software. The least number of data points to determine an acceptable confidence interval is ten bioassay samples taken at least a week apart. The system was benchmarked using a random sampling of urinary excretion samples from a known case at the Y-12 plant in the 19601″s. The electrochemical system was characterized using U.S. Department of Energy synthetic urine quality assurance standards from and inter-laboratory exercise in 2012. The separation apparatus was able to consistently separate uranium from the synthetic urine solutions with a consistent recovery between ten and fifteen percent and up to fifty percent. The method is isotope independent and maintains the enrichment of any excreted material. This allows for the material to be compared to operational logbooks at facilities using multiple enrichments in the nuclear fuel cycle. This methodology is recommended for spot estimation in support of a traditional bioassay program.