Abstract: A method for improving fluidization of a particulate material flowing through a fluid conductor is provided by controlling the rate of addition of fluid, such as aerating gas or steam at a plurality of spaced apart locations along the conduit. The composition and rate of flow of the fluidized particles, is controlled by positioning a source of penetrative radiation such as neutrons, gamma rays, or X-rays at any location along the conduit so that the radiation traverses the fluidized particulate material flowing therein. A radiation detector is positioned opposite the source so that radiation absorbed in the conduit by the fluidized mixture may be measured as an electrical quantity. This electrical quantity may represent the total number of gamma rays of a preselected energy interacting with a detector in a given time interval or the average number of all gamma rays generating electrical pulses by interaction with the radiation detector.