UC Berkeley

Rapid scanning of intermodal cargo containers for clandestine fissionable material is a security concern of the United States government. This issue has been investigated over the past ten years with limited success. This dissertation builds on previous simulation work to investigate the limits of a multi-view scanning technique to determine the linear attenuation coefficients of small high-Z objects hidden within cargo containers. Monte Carlo modeling was used to estimate the uncertainties in the measurement, the false negative rates, and the false positive rates, as well as the dose that a person inside the container might receive. It was found that bremsstrahlung beams with 6 and 9 MeV endpoint energies provide sufficient penetration through the cargo. With an applied energy threshold of 2-3 MeV and a correction for the intensity due to singly-scattered photons, the effective linear attenuation coefficient could be determined for uranium spheres as small at 1.5 cm radius with an estimated dose of 10-40 mad and an estimated 1% false negative rate.