Hydrothermal Synthesis and Characterization of the Thorium Phosphate Hydrogenphosphate, Thorium Hydroxide Phosphate, and Dithorium Oxide Phosphate

Synthesis and characterization of low-temperature precursors of thorium–uranium (IV) phosphate–diphosphate solid solutions

“…The unit cell parameters were refined by the means of U-Fit program [30] considering the space group P2 1 [31]. For each compound, all the diffraction lines observed are consistent with that previously reported for TPHPH [22,28,31]. No additional diffraction line was found which confirmed that the samples were all single phase.…”

“…The normalized dissolution rate ranges from (5.8 ± 0.3) · 10 À6 g m À2 day À1 (10 À1 M HNO 3 ) to (4.8 ± 0.3) · 10 À8 g m À2 day À1 (pH = 7) at room temperature, which is several orders of magnitude lower than for other matrices such as basaltic glasses [27]. The dissolution of b-TPD is rapidly followed by the formation of neoformed phases containing radionuclides in the back-end of the dissolution of the initial ceramic: they are thorium phosphate-hydrogenphosphate hydrate Th 2 (PO 4 ) 2 (HPO 4 ).H 2 O (TPHPH) for thorium [28] and uranyl phosphate pentahydrate for uranium (tetravalent uranium being oxidized into uranyl during the dissolution process) [21,26]. Due to the different chemical behaviors of thorium and uranium during leaching tests, the heterogeneity of the samples can degrade their chemical durability through the presence of Uenriched secondary phases.…”

Influence of plant activity and phosphates on thorium bioavailability in soils from Baotou area, Inner Mongolia

“…3b, which matched the ratios of Th (PO 4 ) 3 and ThP 2 O 7 , respectively. Because of their low solubility in water and high thermal stability, thorium phosphate and thorium pyrophosphate seemed to be very good matrixes for radionuclide immobilization (Fourest et al, 1999;Brandel et al, 2001). The production of the crystal compounds from the reactions of soluble thorium and phosphate/pyrophosphate indicated that the available thorium in soil could be transformed into a stable thorium due to the addition of HAp and pyrophosphate.…”

Improvement of the preparation of sintered pellets of thorium phosphate-diphosphate and associated solid solutions from crystallized precursors

“…Consequently, the synthesis of crystallized precursors of b-TPD and b-TUPD solid solutions i.e. thorium phosphate-hydrogenphosphate hydrate (TPHPH) [15] and associated U x/2 Th 2Àx/2 (PO 4 ) 2 (HPO 4 ) AE H 2 O solid solutions (TUPHPH) [16], respectively, was performed in order to get dense and homogeneous solids at high temperature. We report in this paper some new features concerning the preparation, the characterization, and the sintering of these low-temperature crystallized precursors.…”