<p>Nuclear fuel cycle processes such as aqueous separations seek improved real-time material characterization and process monitoring techniques. Gamma-gamma coincidence spectroscopy has the potential to meet this need in these high radiation environments by reducing background noise, thereby enhancing detection limits and improving isotopic identification accuracy. An array of three CdTe detectors was designed to evaluate the feasibility of passively assaying the nuclear materials flowing through a pipe in such a facility. The absolute efficiency of each CdTe detector was measured and found to be up to 60 times greater than that of an HPGe detector when normalized by active detector volume. This experimental data was then used to validate a Geant4 model of the detector array, which showed excellent agreement with the measured data, and then the validated Geant 4 model was modified to simulate a representative on-line process monitoring scenario. Finally, gamma-gamma coincidence measurements of a <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({^{241}}\text {Am}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mrow /> <mrow /> <mn>241</mn> </mmultiscripts> <mtext>Am</mtext> </mrow> </math></EquationSource> </InlineEquation> source were performed using two CdTe detectors and demonstrated the background reduction capability of this technique. Future work will include further optimization to the detector array configuration and the Geant4 model to enable on-line quantification of relevant actinides in a Pu processing glovebox containing aqueous separations equipment at PNNL.</p>