US EPA

3793852 

Technical Report 

72F | Statistical Analysis 

F. D., R 

2015 

NTIS\ADA619753_a 

Nuclear and radiological materials in the possession of those who intend to use them for malicious purposes are considered to be out of regulatory control. The ability to interdict the movement of special nuclear materials out of regulatory control is of utmost importance in national security. In the maritime environment where such material may be moved on large vessels, detection is complicated. Additionally, the level of the radiation background on and in the immediate vicinity of the ship (where an illicit source might be detected) is affected by the "ship effect." The neutron and radiation ship effect is a phenomenon involving high energy physics where cosmic radiation interacts preferentially with high atomic number materials to produce additional background radiation. This research project's purpose was to advance the ability to identify special nuclear material aboard a maritime vessel by stand-off radiation detection through characterization of the ship effect. The objectives of this project were the completion of the following steps: (1) Integrating a portable and environmentally protected radiation detection system to be used in a mobile situation. (2) Conducting measurements of the background neutron radiation both on land and surrounding a ship on the water. (3) Simulating a radiation signature emitted from nuclear material aboard a ship using radiation transport software. (4) Comparing the measured radiation signatures and modeled source signatures to show the ship effect's impact on detection feasibility of nuclear material in a maritime environment.