Authors:M. Sampath, Pranay Sinha, Shekhar Kumar, U. Mudali, and R. Natarajan
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.
Authors:A. Palamalai, S. Mohan, M. Sampath, R. Srinivasan, P. Govindan, A. Chinnusamy, V. Raman, and G. Balasubramanian
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.
Authors:Shekhar Kumar, Bijendra Kumar, M. Sampath, D. Sivakumar, U. Kamachi Mudali, and R. Natarajan
Nuclear solvent extraction was traditionally performed with packed columns, pulse columns, mixer-settlers and centrifugal
extractors. However for rapid separations at micro-flow level, micro mixer-settlers were desired and in the past, few of them
were actually designed and operated in nuclear solvent extraction research. In the current era of micro-reactor and microchannel
devices, there is a renewed interest for micro-mixer-settlers for costly solvents and specialty solutes where small flow-rate
is not an issue. In this article, development of a simple but effective micro-mixer-settler for nuclear solvent extraction
is reported. The developed unit was tested with 30% TBP/n-dodecane/nitric acid system and in both the regimes of mass transfer c → d (mass transfer from continuous phase to dispersed
phase, also written as c → d) and d → c (mass transfer from dispersed phase to continuous phase, also written as d → c) nearly
100% efficiency was observed in extraction as well as stripping modes of operation.
Authors:Bijendra Kumar, Shekhar Kumar, M. Sampath, D. Sivakumar, U. Mudali, and R. Natarajan
Supercritical CO2 assisted dissolution of metals and metal-oxides and in situ extraction by TBP (or co-solvent) has been reported in literature.
However, in this work, the dissolution and in situ extraction by nitric acid solvates of TBP and alternate solvent TiAP has
been reported for g-level UO2 (essentially PHWR fuel pellet fragments) feeds at atmospheric pressure without requiring supercritical fluids. Encouraging
results were obtained.
Authors:Bijendra Kumar, M. Sampath, Shekhar Kumar, D. Sivakumar, U. Kamachi Mudali, and R. Natarajan
Recently authors demonstrated direct dissolution of g-level PHWR UO2 fuel pellet fragments and in situ extraction by TBP-HNO3 and TiAP-HNO3 solutions at atmospheric pressures. Extending the work, similar studies were performed on intact unirradiated PHWR UO2 fuel pellets (~15 g U) with varying compositions of organic solvate of tri-n-butyl phosphate (TBP). It was observed that extent of dissolution was a strong function of organic solution composition TBP·(HNO3)x(H2O)y. Complete dissolution of intact UO2 pellet in a reasonable time was observed only in case of a particular solvate composition.