Assessment of Uranium Detection Through Active Interrogation with Conventional and Tensioned Metastable Fluid Detectors

This thesis describes the first step in successfully developing an Acoustically Tensioned Metastable Fluid Detector (ATMFD) based method for active detection of Special Nuclear Materials (SNMs). Also described is the successful use of neutron-based active interrogation with state-of-the-art detectors to detect significantly smaller amounts of uranium compared to that achieved by others. One of the greatest difficulties in detection of SNMs by active interrogation is the task of distinguishing between the probing particles and the secondary particles that indicate the presence of SNMs. The ATMFD\u27s selective insensitivity and γ photon blindness features are advantageous for alleviating this problem. The working principle of the ATMFD is discussed along with its applications for security. A literature survey of other active interrogation techniques is summarized to act as a basis for comparison with the ATMFD based technique. Simulations were conducted using MCNP to predict the outcome of several ATMFD based active detection scenarios. Experimental work involving detection of small quantities of uranium with conventional detectors is discussed along with results of fission neutron detection. Statistically significant detection was obtained within 5 minutes of counting to ascertain and measure conclusive evidence for the presence of a 25 g sample of uranium (in uranyl nitrate form) containing \u3c 0.1g of 235U. The same was found to be the case with enhanced certainty with a larger natural uranium-based sample of 630 g (in UO2 form). The results of the experimental work along with the simulation results are compared to the published results from the literature survey to make a case for the potential utility of an ATMFD based active interrogation. It is also pointed out that the ATMFD could be directly integrated into several of the existing systems to provide a γ photon blind and less costly alternative to the current state-of-the-art detectors. Lastly, recommendations have been made for the next steps in developing an ATMFD based active interrogation based detection system