M. Sampath

Final purification of uranium-233 oxide product from reprocessing treatment of irradiated thorium rods

Some batches of233U oxide product obtained from the reprocessing treatment of irradiated thorium rods, called J-rods in our plant, have been found to contain thorium as much as 85% and iron above 5% as impurities. This product has to be purified before sending for fabrication of the fuel. The present purification method consists of the following three steps: (1) preferential dissolution of U3O8 as compared to thoria, (2) a novel solvent extraction process, and (3) preferential precipitation of Th as oxalate leaving behind the entire U in the filtrate. Development and application of the present purification method to the above233U oxide proxduct are presented in this paper.

Dissolution of intact UO2 pellet in batch and rotary dissolver conditions

Comparative dissolution of intact un-irradiated UO2 pellet of PHWR fuel dimensions was performed in batch and dynamic rotary dissolver conditions in aqueous nitric acid solutions at elevated temperatures. The extent of dissolution was estimated by determining the uranium concentration of the resulting aqueous solution. It was observed that rate of dissolution was much faster in dynamic conditions as compared to static batch conditions.

Characterisation of submicron size entrainment in the aqueous product stream of a 40 mm diameter centrifugal extractor for 30% tbp/nitric acid biphasic system

Annular centrifugal extractor is a favoured solvent extraction contactor where process flowsheet requires a low hold-up, lower residence times and compact layout. However during operation of annular centrifugal extractor, a small entrainment, generally of the order of few hundred ppm, is always observed. To characterise this small entrainment, hydrodynamic experiments in a no-mass transfer mode were conducted on a 40 mm centrifugal extractor with 30%TBP/dodecane and acidified water. The aqueous product stream was analysed by dynamic light scattering based methods and drop size distribution was experimentally measured. The maximum entrained micro-drop size was typically below 1 μm in most of the cases and in the rest it was well below 10 μm. Thus the original assertion, that small entrainment occurred due to micro-sized drops, was proved right. However due to complex relations of peak locations and relative peak intensities to the physical and operating properties of solvent extraction system, mathematical modelling or correlation of experimental results was not feasible.

Particle Size Variation and Prediction of Molecular Weight of Bi(III) Hydrolyzed Polymer Using Light Scattering Technique

The present paper gives an overview of the hydrolysis reactions up to colloid formation of Bi(III) in aqueous nitric acid medium using light-scattering measurements. The hydrolysis products of Bi were polynuclear complexes such as dimers, pentamers, and the most important is the hexameric species. In the present investigation Bi3

New data on decomposition of nitric solutions of acetohydroxamic acid

Acetohydroxamic acid (AHA) is an important complexant/reductant for Pu(IV) in the UREX process. It decomposes in the presence of nitric acid. In literature, its decomposition kinetics in nitric acid is traditionally reported as pseudo-first order reaction. In this study, new experimental data were reported for kinetics experiments under wide consecration conditions. It was found that the decomposition reaction was first order with respect to both the components hence overall second order.