Fabrication of Nd- and Ce-doped uranium dioxide microspheres via internal gelation

Abstract

Nd-and Ce-doped gels with Ln contents up to 30 mol% and good sphericity synthesised • successful implementation of the dopant into 3UO 3 •2NH 3 •4H 2 O matrix of the gel • Ce III more suitable than Ce IV for the fabrication of doped UO 2 by internal gelation • single phases for U 0.95 Ln 0.05 O 2±x to U 0.7 Nd 0.3 O 2±x and U 0.8 Ce 0.2 O 2±x obtained • fabrication process for transmutation fuel or targets materials via IG improved

Structural changes of Nd- and Ce-doped ammonium diuranate microspheres during the conversion to U1−LnO2±

“…Intensity variations were observed, but no additional reflections compared to the un-doped composition were recognised [15].…”

“…The actual dopant contents of the particles were determined by inductive coupled plasma mass spectrometry in our former study [15]. Two particles of each composition, dissolved in HNO 3 , were diluted and analysed.…”

“…The IG process was applied to fabricate Nd-doped UO 2±x particles with up to 43 mol% Nd [14], using neodymium as simulant for the trivalent MA americium. It was optimised in terms of automation and its suitability to prepare Ce-doped UO 2±x microspheres was investigated using Ce III and Ce IV dopant precursors to simulate plutonium [15]. Microspheres containing up to 30 mol% Ln were fabricated using Nd III and Ce III , while Ce IV was suitable to prepare microspheres with up to 10 mol% dopant, using the chosen gelation parameters.…”

“…Microspheres containing up to 30 mol% Ln were fabricated using Nd III and Ce III , while Ce IV was suitable to prepare microspheres with up to 10 mol% dopant, using the chosen gelation parameters. The dopant was successfully incorporated into the 3UO 3 •2NH 3 •4H 2 O matrix [16] of the dried gels, which was converted into U 1−y Ln y O 2±x solid solutions by a calcination in air at 900°C for one hour and a subsequent sintering in reducing atmosphere at 1600°C for 10 h. Sintering under reducing conditions resulted in broken particles for the compositions prepared with the Ce III precursor and higher dopant contents (≥ 15 mol%), while compositions prepared with Ce IV exhibited cracks on the surface [15]. The thermal decomposition of un-doped ADU particles during the calcination in air was investigated by a combination of thermogravimetric analyses (TGA), thermogravimetric differential scanning calorimetry (TG-DSC), evolved gas analysis mass spectrometry (EGA-MS) and in-situ high-temperature X-ray powder diffraction (HT-XRD) [16].…”

“…A similar methodology was applied to prepare Nd-and Ce-doped ADU gels with dopant contents up to 30 mol%, using the hexahydrate nitrates of the trivalent lanthanides and diammonium nitrate of cerium(IV) as dopant precursors. The fabrication is described in detail in our previous study [15]. In both studies, urea and hexamethylenetetramine (HMTA) served as gelation agents during the IG process, the gelation agent amount is expressed as ratio (R) of the molar amounts of the gelation agents to the molar amounts of the metals in the sol.…”