CHARACTERIZATION OF THE SOLIDS FORMED FROM SIMULATED NUCLEAR-FUEL REPROCESSING SOLUTIONS

Solids formed from synthetic nuclear fuel reprocessing solutions under process conditions containing Zr, Mo and Ru and additionally U and Pu have been characterized by use of emission, X-ray fluorescence, Raman and infrared spectroscopy, thermogravimetry and X-ray diffraction techniques. In solutions containing an excess of Mo relative to Zr, the solid residues consist of a mixture of ZrMo2O7(OH)2·2H2O and MoO3 while in the absence of Zr mainly UO2Mo2O7·1.3H2O and/or Pu(MoO4)2·H2O are precipitated. Hydrated Zr and U molybdates from non-crystalline phases on dehydration and on further heating to above 500°C result in the recrystallization of ZrMo2O8 and UO2MoO4 and MoO3, respectively. Hydrated Pu molybdate is different from the known structures and the X-ray diffraction patterns and the Raman spectra of its hydrated and anhydrous forms are identical. The infrared and Raman spectra support the presence of MoO6 octahedra in hydrated Zr and U molybdates and MoO4 tetrahedra in their dehydrated structures. The advantages and the limitations of the Raman microprobe technique with regard to its applicability to the nuclear fuel cycle are discussed. © 1990.