A metering system is described for metering quantities of particles, such as fissile, fertile and shim particles for nuclear fuel elements. Predetermined volume discharges from three particle reservoirs are collected and two of them are weighed in comparison with a predetermined standard. A small amount of particulate material is added to each of the two weighed containers dependent upon the difference between the weight of the volumetrically dispensed particles therein and the predetermined standard. All three intermediate containers are then discharged into a volumetric chamber which is then brought to a standard volume by the addition of further particles. The resultant charge in the volumetric chamber is comprised of a fixed volume in which the weight of particles from two of the three reservoirs is standardized.