Conductivity, Radiolytic Effects, and Diffusion Measurements of Interdicted Time-dependent Metallic Signatures (CREDIT)

Analysis of interdicted material is an ongoing effort that is of importance to a number of government agencies including U.S. Department of Homeland Security. This project seeks to perform two separate tasks: 1) to perform innovative measurement techniques on metallic compounds, both alloys and single element samples, to determine fundamental properties, and 2) utilize these techniques to gain an in depth understanding of forensics signatures that could be used to identify interdicted materials. Interdicted nuclear materials will likely be metallic and will therefore undergo certain types of aging such as intermetallic diffusion. The diffusion of these materials can be readily observed using certain types of probing techniques (eg. SEM, scanning electron microscopy). As with the dating of very old metallic artifacts, the rates of these diffusion profiles is driven by time, temperature, and other processing parameters that can be used to provide distinctive signatures that lead to an understanding to the previous processing parameters. Similarly, as nuclear materials age, they often decay by alpha particle radiation, which causes an increase in damage sites in the material. In this project, attempts will be made to determine if these sites can be probed with imaging techniques like con-focal laser scanning microscopy (CLSM) and tunneling electron microscopy (TEM) and the results used to back- calculate the age of the sample. However, it is also known that radiolytic damage causes change in the electrical conductivity of the sample, so efforts will be made to determine the effect of radiolytic damage in order to determine the age of the sample. The radiolytic damage measurements made by electrical conductivity, TEM, and CLSM will be evaluated by other techniques such as small angle neutron spectroscopy (SANS). Ideally this project will verify that electrical conductivity measurements and bench-top SEM measurements could be used to determine age and processing parameters for interdicted material. The conductivity and SEM measurements could in theory be fieldable or deployable. The outcomes of this project would investigate innovative measurement techniques in an effort to develop a series of processing signatures for interdicted nuclear materials that would be useful to the nuclear forensics community.