Carbon-in-water suspensions (CWS) have unique optical properties and have received increasing interest recently for various applications. In the field of combustion science, CWS have been recommended as a substitute for the traditional fossil fuels. The idea is to suspend carbon (coke or coal) particles in water and then inject them as a spray into a gasifier or boiler. The potential benefits are lower emissions and higher combustion efficiency, in comparison to directly injecting coal particles into air or water steam. Nevertheless, few studies have examined CWS colloidal fuels. Especially, droplet breakup can occur when the droplets are exposed to radiation. The goal of this paper is to understand droplet breakup mechanism of CWS under intense radiation. An experiment was developed to visualize the breakup process and to measure the threshold radiation intensity required for explosion at varying particle concentrations and sizes as well as droplet sizes. The results show that radiation absorption by the carbon particles play a critical role in the breakup behavior. A theoretical model was also developed to determine the effects of the particle material, size, and concentration on the threshold radiation energy. (C) 2014 Elsevier Ltd. All rights reserved.