IN-SITU EXAMINATION OF URANIUM CONTAMINATED SOIL PARTICLES BY MICRO-X-RAY ABSORPTION AND MICRO-FLUORESCENCE SPECTROSCOPIES

Two complimentary spectroscopic techniques, X-ray absorption and fluor escence spectroscopy have been conducted at spatial scales of 1 to 25 mu m on uranium contaminated soil sediments collected from two former nuclear materials processing facilities of the DOE: Fernald, OH and Sa vannah River Site, SC. A method of imbedding particles in a non-reacti ve Si polymer was developed such that individual particles could be ex amined before and after extraction with a wide range of chemicals typi cally used in sequential extraction techniques and others proposed for ex situ chemical intervention technologies. Using both the micro-X-ra y fluorescence (XRF) and micro-X-ray Absorption Near Edge Structure (X ANES) techniques, both elemental and oxidation state distribution maps were generated on individual particles before and following chemical extraction. XANES can determine the relative proportion of U(VI) and U (IV) in phases comprising individual particles before and after extrac tion and showed that greater than 85% of the uranium existed as hexava lent U(VI). Fluorescence spectra of contaminated particles containing mainly U(VI) revealed populations of uranyl hydroxide phases and demon strated the relative efficacy and specificity of each extraction metho d. Correlation of XAS and fluorescence data at micron scales provides information of U oxidation state as well as chemical form in heterogen eous samples.