Chemical qualification of magnesium di-uranate by ICP-AES technique

Nuclear Fuel Complex (NFC), an industrial unit of Department of Atomic Energy (DAE) is engaged in fabrication of nuclear fuel subassemblies for Pressurized Heavy Water Reactors (PHWR) operating in India. Uranium Di-Oxide (UO2) in the form of pellets finds extensive applications as nuclear fuel in nuclear power reactors. Magnesium Di-Uranate (MDU), also known as Yellow Cake, is the raw material for the production of UO2 fuel pellets. NFC receives Magnesium Di-Uranate (MDU) from Uranium Corporation of India Limited (UCIL) which extracts Uranium from mines located at Jaduguda and Turamdih. Generally, MDU is produced by leaching of Uranium from the ore with H2SO4 and its purification using anion-exchange followed by precipitation of Uranium as MDU by addition of calcined dolomite. During these processes, a host of impurities present in ore finds their way into MDU through the elute in the anion-exchange purification stage. Also some more impurities are picked up by the process stream while adding dolomite. Many of these impurities find their way in to Uranium Di-Oxide (UO2) fuel pellets during the conversion of MDU into UO2 pellets. Due to different reasons, presence of these impurities is monitored in MDU. Hence, quantitative estimation of concentration of impurity elements in MDU for its use in nuclear applications forms an important part of Quality Assurance (QA) programme. The present paper describes a method for estimation of different impurity elements in MDU using Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES). The method involves dissolution of MDU, separation of uranium matrix from impurity elements by solvent extraction using Tri-n-Butyl Phosphate (TBP) in CCl4 and Tri-n-Octyl Phosphine Oxide (TOPO) in CCl4 solvents in sequence. The resultant aqueous solution subjected for quantitative estimation of different elements by ICP-AES. Optimization of solvent extraction conditions for effective separation of impurity from matrix is discussed in the paper. Standard recovery and comparison studies of MDU from Jaduguda and Turamdih are also in the paper. An RSD of ± 10% has been achieved for most of the elements by this method. This method offers a fast, accurate and simultaneous determination of impurity elements at trace level in MDU. (author)