Low-enriched uranium hexafluoride, the starting material for the chemical conversion process, is vaporized. This gaseous uranium hexafluoride is then reacted with pure water to produce an aqueous solution of uranyl fluoride. Aqueous amonia is added to the uranyl fluoride, and the precipitate is filtered and dried to form a powdered form of ADU (ammonium diuranate). Further, through the processes of dewatering, drying, calcinations/reduction, and milling, the uranium dioxide powder is manufactured from the ADU.
Granulated UO2 powder is pressed into pellet form by a rotary press. The "green" pellets are fired in a sintering furnace at a temperature higher than 1700℃ to produce UO2 pellets sinteral. The sintered pellets are then ground to specified dimensions.
UO2 pellets are loaded into a zirconium alloy-cladding tube. Then, a pellet compression spring is inserted at one end, and end plugs are pressed into place at both ends. Top and bottom end plugs are welded to the cladding tube. The tube is filled with helium gas which is pressurized through a small vent hole in the top end plug. Finally the vent hole is seal-welded which completes the fuel rod assembly.
Fuel rods are inserted into a matrix of six to nine grids (or spacers). Guide thimble tubes are mechanically joined to the grids (or spacers) and top and bottom nozzles are attached, completing the fuel assembly fabrication.