Sensitivity analysis towards trace-uranium detection with $\gamma$-$\gamma$ coincidence NAA

Abstract

We present an improved approach for detection of trace amounts of $^{238}$U by means of neutron activation analysis (NAA). The analysis enhancement is obtained by utilizing $\gamma$-$\gamma$ coincidence counting. An empirical method for evaluating the sensitivity gain in the presence of a large source-related background is presented. A comparison of detection limits is made between two counting schemes; namely, counting single gammas using one HPGe detector versus counting coincident gammas using two HPGe detectors placed face-to-face. A data-validated radiation transport model, created in GEANT4 for a single HPGe detector, is extended to handle the two-detector setup. In this counting scheme, a $^{238}$U-detection sensitivity enhancement of about a factor of 8 is predicted for a sample of Saint-Gobain G3 Sapphire when compared to the simpler singles counting approach.