Chapter 11 - Radioactive particle tracking in multiphase reactors: Principles and applications

Abstract

This chapter discusses the principles and applications of radioactive particle tracking (RPT) in multiphase reactors. Radioactive nuclides release their excess energy by the emission of α-, β- and γ-rays.While the charged α- and β -particles are quickly absorbed by any material, the highly-penetrating γ-rays can travel substantial distances to a location where a detector may be placed. The number of photons registered, depends on the distance between the γ-emitter and the detector. This principle is exploited in RPT in which an array of scintillation detectors is used to view a single particle loaded with radioactivity. The number of photons registered (γ-ray) by a given detector is a measure of the radius of an approximately spherical surface with the detector as its center and the particle located on the surface. In practice, the three coordinates of the particle are determined by algorithms based either on phenomenological or empirical approaches that account for the relation between the number of photons registered by each detector and the location of the tracer particle. In principle, both fluid and granular flows can be studied with appropriate radioactive flow followers as long as they match in size, density, shape and buoyancy. The ability of the technique to make non-invasive, phase-specific trajectory and velocity measurements and to probe hydrodynamic phenomena ranging from slow flows (nearly at rest) to high speed flows (a few meters per second) in multiphase systems of high holdup and that are opaque makes RPT an invaluable tool to be added to the chemical engineer's expertise.