Nuclear Technology / Volume 173 / Number 3 / March 2011 / Pages 318-326
Technical Paper / Miscellaneous
Nanoparticles can form during nuclear accidents as well as during normal nuclear reactor operations and can be both radioactive and nonradioactive. It is important to understand particle size characteristics, transport properties, and deposition in order to better predict the behaviors of, and effects due to, these particles in a reactor. Fission products can deposit (adsorb/absorb) on the graphite dust in the core [an amount of carbon dust is present in the Pebble Bed Modular Reactor (PBMR) because of graphite sphere abrasion] and can also be carried by the helium flow (together with some dust). Generating nanoparticles of desired shape, size, and purity for experimental purposes is difficult, and hence, there is a need for new and refined synthesis techniques. Nanoparticle generation using high-voltage electric sparks has become a technique of interest for a wide range of conducting materials, and particles with sizes ranging from a few nanometers up to microns have been generated in this manner in an aerosol state. Our purpose in this paper is to report on the generation, collection, and characterization of carbon nanoparticles. We have used a spark generator and a thermophoretic deposition cell, as well as environmental scanning electron microscopy, transmission electron microscopy, and scanning mobility particle spectrometry. We have explored a number of experimental conditions, and we find that one can generate and effectively collect test particles with a variety of different useful characteristics. We also discuss some computational fluid dynamics simulations of particle deposition in the thermophoretic deposition cell.