Sequential Radiochemical Procedure for Isotopic Analysis of Uranium and Thorium in Egyptian Monazite

Abstract

Gamma and alpha spectrometry techniques were applied to determine the activity concentrations of ²³⁸U and ²³²Th (Bq kg^–1) as well as the ²³⁴U/²³⁸U and ²³⁰Th/²³⁴U isotopic ratios for commercial grade monazite (purity ≈50%) supplied from the Egypt nuclear materials authority. A method for total dissolution of monazite followed by the sequential radiochemical separation using anion-exchange chromatography is presented. The average activity concentrations of ²³⁸U and ²³²Th, measured by α-ray spectrometry, are 2.49 g kg^–1 (0.24 wt %) and 30.09 g kg^–1 (3.1 wt %), respectively. The calculated ²³⁴U/²³⁸U and ²³⁰Th/²³⁴U isotopic ratios are close to unity, suggesting closed system equilibrium. The possibility of using leaching of monazite with water at different pH values for gaining information about the masses of uranium and thorium that pass into the solution and remain fixed in the crystal lattice was examined.