Single Particles Handling and Analyses

Abstract

A single environmental hot particle carries a wealth of information about its radiological, chemical and metallurgical history, including clues about its release-scenario. The physical and chemical characteristics of the particle bear upon its mobilization and long-term behavior in the ecosystem. The ability to locate, re-locate, handle and analyze single, isolated particles is essential in the arenas of nuclear forensics, safeguards investigations and environmental research. Single particles should be analyzed rather than agglo- merates, because the latter invariably display averaged values, such as speciation or radionuclide dispersion in environmental samples or enrichment levels in safeguards samples. A rainbow of advanced microanalytical techniques is presently available, often in remote laboratories. Full characterization of an individual particle is a multiple-instrument task that requires the ability to repeatedly re-locate and micromanipulate particles in the sub-micrometer size-range and up. Within the framework of the Hot Particles Coordinated Research Project (CRP), launched by the IAEA (NAAL, Seibersdorf) in 2001, methods have been developed, implemented, and tested on real samples for single particle re-location, ex-situ micromanipulation and relocation (transfer) between source- and target-instru- ments. The two, three, and six reference marks re-location algorithms have been written. Two types of ex-situ particle micromanipulation systems based on light microscopes (binocular- and stereo-microscope types) have been built. They were used in a variety of cases, such as loading single particles on TIMS filaments, or attaching them to needles for synchrotron measurements. FIB micro-surgery of single particles, exposing their inner structure, has been demonstrated. These methods, along with other methods for single particles handling and analyses will be discussed in this article. D.H.