Process improvements in uranium oxide powder production for PHWRs in India

Nuclear Fuel Complex (NFC) an industrial unit of Department of Atomic energy, India, manufactures natural Uranium-di-Oxide fuel for all the PHWRs in India. NFC follows Ammonium Di-Uranate (ADU) route for the production of Uranium Oxide (UO2) powder. The raw material for production of UO2 powder is Magnesium Di-Uranate (MDU). The raw material, after dissolution in commercial nitric acid is purified and precipitated to form ammonium-di-uranate (ADU). ADU is filtered, dried, calcined, reduced and stabilized to get UO2 powder suitable for pellet fabrication. Over the period several modifications and developments in the process and equipment were made. The authors have discussed the modifications made in various process steps to enhance and improve productivity and quality of UO2 powder and also for better environmental pollution control. The major developments are: A novel way of passing feed of higher concentration in the purification step; Washing of raffinate with solvent to recover uranium; and, Adopting ammonia vapour for ADU precipitation from pure Uranyl Nitrate solution and for neutralization of raffinate, in place of aqueous ammonium hydroxide and sodium hydroxide solutions, respectively. The paper gives the details of these successful modifications and developments. (author)