Uranium Assay of Phosphate Fertilizers and Other Phosphatic Materials

Abstract

A method utilizing solvent extraction coupled with liquid scintillation spectrometry was developed for the assay of U in fertilizers and other phosphate-containing minerals and chemicals. Tri-n-octyl phosphine oxide in toluene is used to extract U from a nitric acid solution, while phosphate interference is suppressed by the addition of Al ion. The U is stripped from this solution and reextracted into a scintillator for counting in a high-resolution liquid scintillation spectrometer. The sensitivity of the counting method is enhanced by the use of pulse-shape rejection of the .beta.-.gamma. background. Results indicate a detection threshold of 0.0028 pCi (0.004 ppm) of U with a reproducibility of .+-. 2.5% and an average recovery of 99% at the 50-ppm level.