Abstract: A critically safe container for the storage and rapid discharge of enriched nuclear fuel material in powder form is disclosed. The container has a hollow, slab-shaped container body that has one critically safe dimension. A powder inlet is provided on one side wall of the body adjacent to a corner thereof and a powder discharge port is provided at another corner of the body approximately diagonal the powder inlet. Gas plenum for moving the powder during discharge are located along the side walls of the container adjacent the discharge port.

Abstract: A mixture of powders, preferably UO.sub.2 powders, is blended to complete homogeneity in a nuclear-safe, bubbling-bed fluidized bed blender. The blender includes a generally vertically-oriented, slab-shaped, nuclear-safe mixing vessel having a fluidizing grid disposed on the bottom of the vessel. The fluidizing grid comprises a linear array of generally downwardly-directed pyramidal-shaped hoppers each having walls converging into a conically-shaped closable opening. A plurality of gas orifices is provided for directing a flow of fluidizing gas downwardly into the bottom of each of the hoppers and fluidizing gas is supplied to the orifices at a velocity sufficient to cause bubbles of fluidizing gas to rise through and emerge from the mixture of UO.sub.2 powders until a homogeneous blend of solid UO.sub.2 powders is achieved. The apparatus eliminates dead-zones normally present near the bottom of prior art fluidized bed blenders.