Motivation

Securing the nation's borders from any attempt to transport a nuclear or radiological device into the U.S. is a critical need. Current nuclear material detection technology is inadequate for several important smuggling scenarios. One of the most difficult challenges is the interdiction of shielded highly enriched uranium (HEU) being smuggled in cargo or on a vehicle into the U.S.  Meeting this threat necessitates the development of improved inspection policies and advanced detection systems. The SHIELD project at Texas A&M University has designed advanced interdiction systems that can provide revolutionary improvements in the performance of border monitoring technology. This is achieved through incorporation of detector arrays that fully integrate all available signal information, including inverse analysis simulations. Previous efforts at detector development have not considered a complete integration of all available signals and thus do not lead to optimized systems. This lack of optimization has led to the failure of current systems in some of these smuggling scenarios. 

Framework
Figure 1. The SHIELD Framework

Development of the SHIELD Framework

For the past four years, a multi-disciplinary team led by the Nuclear Security Science and Policy Institute (NSSPI) at Texas A&M University has been working on SHIELD, an NSF/DNDO Advanced Research Initiative project. The project's goal is to devise and test an innovative framework for evaluating and guiding the development of nuclear detection systems based on complete signal and information integration. This framework generates predictive knowledge through the integration of optimized radiation detection sensor arrays, radiation transport forward models, inverse analysis, systems and risk analysis, social science components, and novel sensor approaches. New detector system concepts can be evaluated using the SHIELD framework. Also, by analyzing the framework in reverse, required performance characteristics of optimized detector systems can be determined to allow the system to achieve a specified risk level.

Shield Frameword Fig 2_800
Figure 2. The results from a SHIELD evaluation for a scenario with HEU smuggled in a cargo container. Figure 2a shows the results for containers with HEU (red dots) and without HEU (blue dots) for the currently deployed system. As can be seen, the sets of dots are essentially indistinguishable. Figure 2b shows results for the same containers after optimization through the SHIELD framework where an additional detector characteristic is added. In this case the red dots and blue dots are clearly distinguishable, and the HEU can be readily detected.

Future Efforts

We are currently testing the individual SHIELD framework elements in a laboratory environment and exercising its overall system-level performance via simulation. However, the SHIELD framework will need to be tested in a field setting to verify and validate its capability. This would require utilization of the SHIELD framework and associated computational tools with a national laboratory partner with portal monitor or field interdiction test bed capability and utilizing bulk sources of HEU. Once properly validated the SHIELD framework could provide revolutionary improvements in the performance of border monitoring technology.