"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
1960'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.
Associated Project(s):Measurement of Uranium in Bio Matrices for Nuclear Forensic Purposes