Characterization of selected nuclear fuel cycle materials by column extraction chromatography and ICP-AES

Abstract

Current research efforts at the Argonne National Laboratory on nuclear reactor fuel developments require analytical support for the characterization of uranium metal and uranium-bearing alloys and salts. Attempts to determine trace elements at the μg −1 level in these matrices directly by inductively coupled plasma-atomic emission spectrometry (ICP-AES) proved unsuccessful. Even at moderate uranium concentrations (500 μg ml −1), severe spectral interferences for a large number of elements were observed. In particular, the spectral region of 300–400 nm contained numerous uranium lines that interfered with those of important rare earth elements. As a consequence, methods were developed that allowed the quantitative separation of 35 impurities from uranium prior to ICP-AES analysis. Column extraction chromatography was used with neutral organophosphorus compounds as extractants. Columns were prepared from tri(2-ethylhexyl)phosphate (TEHP) or di-n-hexyl-N,N-diethylcarbamoylmethylenephosphonate (DHDECMP) coated trifluorochloroethylene polymer (Plaskon). Uranium was adsorbed by the organic phase and the impurities were eluted by nitric acid. After evaporation and volume adjustment, the trace metals were determined by ICP-AES. Except for Sc and Zr, recoveries obtained using this technique were 86–107%.