[en] Internal Gelation Process (IGP), one of the many variants of sol-gel process can be successfully exploited to prepare spherical particles of desired size from metal salt solutions. Ytterbium-169 is used in brachytherapy for the treatment of prostate cancer. Neutron irradiated Yb₂O₃ microspheres (600 -700 μm) are used as brachytherapy source. IGP has been developed to prepare ytterbia spheres from ytterbium nitrate (Yb(NO₃)₃) solution

[en] (U_0_._7_2,Pu_0_._2_8)O_2 and (U_0_._7_9,Pu_0_._2_1)O_2 are the proposed fuel materials for Prototype Fast Breeder Reactor (PFBR). Conventionally, these fuel materials are being fabricated by powder metallurgical route which poses dust hazard and man-rem problems. Sol-gel process which uses solutions and free flowing solids are highly advantageous for fabrication of such fuel materials. Ce being a chemical homologue of Pu, is used as a surrogate for Pu. In the present study, (U_0_._7_2,Ce_0_._2_8)O_2 and (U_0_._7_9,Ce_0_._2_1)O_2 microspheres were prepared by internal gelation process. The process parameters for the preparation of crack free microspheres were optimized. The Temperature Programmed Reduction (TPR) studies of these microspheres were carried out from RT to 1100°C under (Ar+8% H_2) flow (20 ml min"-"1). The TPR profile showed two reduction peaks at 450 and 500 °C which were merged together corroborating to the reduction of Ce"4"+ to Ce"3"+ and U"6"+ to U"4"+. The XRD analysis of the TPR residue showed the formation of complete solid solution and single phase for both the compositions. From the lattice parameter of these oxides reduced at 1100 °C, it was observed that the oxides pick up oxygen and form hyper stoichiometric oxide which was confirmed by O/M analysis. The dried microspheres were also calcined at different temperatures from 400-800 °C in air. The surface area and pore size distribution of these microspheres were determined by BET method. The calcined microspheres were pressed into pellets of 10 mm diameter and 12 mm length and sintered in (Ar+8%H_2) atmosphere at 1400 °C for 4 h. Alternatively, the dried microspheres were directly reduced to 600 °C at (Ar+8%H_2) atmosphere, stabilized at room temperature in commercial N_2 atmosphere and pellets derived from these microspheres were sintered in a vacuum furnace. The densities of sintered pellets derived from both the routes were determined geometrically. It was observed that the density of pellets sintered in (Ar+8%H_2) atmosphere were more compared to pellets sintered in vacuum. The SEM analysis of these sintered pellets was carried out for microstructure. (author)

[en] The present paper describes the preparation and characterisation of sodium titanate microspheres using Internal Gelation Process which has been already developed for Li₂TiO₃

[en] This paper presents the studies on the direct reduction of uranium trioxide with carbide in vacuum for the preparation of uranium monocarbide microspheres. The UC microspheres were prepared by carbothermic reduction of UO₃+C gel particles, produced by internal gelation process, over a temperature range 1250 to 1500degC in vacuum. The product contained negligible amount of dicarbide and 0.1 per cent of oxygen. The UC microspheres were sintered at 1700degC to high density ( > 95 per cent T.D.), in argon atmosphere. (author). 6 refs

[en] Spherical beads of titania were prepared by a sol-gel route. During the preparation a cationic surfactant was added in the feed broth to modify the surface characteristics of the microspheres. The absorption behavior of Pu(IV) from carbonate medium on these microspheres was studied by batch experiments. Loading and elution behavior of Pu(IV) on a bed of titania microspheres was studied and the practical capacity was determined. (author)

[en] Uranium dioxide microspheres have been prepared by internal gelation process, one of the sol-gel routes for fuel fabrication. The process flow sheet for internal gelation has been modified by employing trichloroethylene(TCE) as an alternate gelation medium. Based on the modified flow sheet, a 5Kg/day assembly for the production of UO₂ microspheres has been developed and installed. (author). 1 fig

[en] Soft UO₂ microspheres could be obtained without addition of pore formers by introduction of a calcination step to convert UO₃ to U₃O₈ prior to its reduction to UO₂, The changes occurring during the calcination step and the mechanism of conversion would be useful in understanding the reason for yielding soft product, The present study deals with the conversion of UO₃ microspheres to U₃O₈ microspheres by heating up to 800 degC, at known partial pressures of oxygen, A probable reaction mechanism of conversion of UO₃ to U₃O₈ has been suggested with the diffusion of molecular oxygen through the product layer as the rate controlling step. (author)

[en] The present study deals with kinetic investigation on hydrogen reduction of U₃O₈ microspheres of different surface characteristics. For low surface area microspheres, reduction reaction was governed by adsorption of H₂ on the surface of the oxide, with activation energy of 94 kJ/mole. However, for high surface area microspheres, reduction reaction was governed by transformation of U₃O_8-z to UO_2+x at the U₃O₈/UO₂ interface, with activation energy of 290 kJ/mole. A probable reaction mechanism has been suggested to explain this observation. (author)

[en] Uranium-cerium mixed oxide microspheres containing 5 and 15 mole percent cerium were prepared by internal gelation process without any pore forming additives. The microspheres were calcined and reduced to give soft (U,Ce) oxide microspheres suitable for gel pelletisation. Green pellets were prepared from these microspheres and sintered at 1200 degC in CO₂ atmosphere.(author). 8 refs., 1 tab

[en] Absorption behaviour of Pu(IV) on titania microspheres, from carbonate medium has been studied. The titania microspheres were subjected to heat treatment at different temperatures and its effect on distribution ratio was determined. The distribution ratio was found to decrease with increase in temperature. (author)