PNNL

Abstract

An accurate particle size and density distribution (PSDD) for nuclear tank wastes is an essential piece of information that helps determine the engineering requirements for a host of waste management unit operations including tank mixing, pipeline transport, and filtration. The existing approach has involved a laborious approach in which individual particles are identified using SEM/XRD methods and the density of these materials obtained from the technical literature. Further, some methods simply approximate individual particle densities by assuming chemical composition rather than actual measurements of particle density. A particle shadowgraph velocimetry and size (PSVS) system has been designed to obtain representative PSDDs for a broad range of Hanford tank waste materials existing as both individual particles and agglomerates. The PSVS utilizes optical hardware, a temperature controlled settling column, and particle introduction chamber to accurately and reproducibly obtain images of settling particles. Image analysis software then provides a highly accurate determination of both particle terminal velocity and equivalent spherical particle diameter. The particle/agglomerate density is then calculated from Newton’s terminal settling theory. The PSVS was designed to accurately image particle/agglomerate sizes between 10-1000µm and particle/agglomerate densities ranging from 1.4-11.5g/cm3 where the maximum terminal velocity does not exceed 20cm/s. Preliminary testing was completed and results were in good agreement with terminal settling theory. Recent results of this method development are presented, as well as experimental design, and future proposed work.