A New Method for Tracking Single Radioactive Particles

A. H. Shehata and R. P. Gardner

Center for Engineering Applications of Radioisotopes (CEAR), Nuclear Engineering Department, North Carolina State University, North Carolina, Raleigh, USA

E-mail: gardner@ncsu.edu

ABSTRACT

A system based on the use of three collimated detectors for non-invasive radioactive single particle tracking in three dimensions is presented. It consists of a set of three, well collimated detectors mounted on a movable platform. The platform can be moved to track the radioactive particle vertically via one collimated detector that has a horizontal slot opening. The other two collimated detectors with vertical slot openings can be rotated to track the radioactive particle in the planar domain and deduce the particle polar coordinates. A complete description of the actual system developed is outlined including the hardware, the automation and control software and the data acquisition aspects.

A critique of the "conventional tomographic" radioactive particle tracking approach in comparison to this new three-detector approach is given. A number of obvious and valuable advantages of the new method are evident – particularly for slow moving particles in randomly packed particle beds as would be the case for pebbles in a nuclear pebble bed reactor. This includes the elimination of detector dead time counting loss problems and the minimization of stochastic (variable) attenuation paths through packed particle beds. Results for a series of benchmark experiments to test and verify the performance of the system are provided. This includes results for tests with real trajectories of a single radioactive particle moving in air and in a bed filled with a mass of granular spherical attenuating media. Testing with these benchmark experiments that include a variety of real time trajectories demonstrates the success of this new three-detector tracking system.

Keywords Radioactive particle tracking, pebble flow monitoring, flow characterization