Extraction of U/VI/ by mixtures of 8-hydroxy quinoline /Oxine/ and neutral donors was studied from 0.1M NaCl at a pH 4.5. The presence of a neutral donor enhanced the extraction of U/VI/ and the species responsible for synergism was established to be 11 adduct UO2Ox2S. From the data, the equilibrium constants for the adduct formation reaction were calculated and was found to be the lowest with TBP and the highest with TOPO.
Due to the scarcity of good quality uranium resources, the growth of nuclear technology in India is dependent on the utilization
of the vast thorium resources. Therefore, Advance Heavy Water Reactor is going to acquire significant role in the scenario
of Indian nuclear technology, where (Th, Pu)O2 will be utilized as fuel in the outermost ring of the reactor core. This will lead to a complex matrix containing thorium
as well as americium, which is formed due to β- decay of plutonium. The amount of americium is dependent on the burn up and
the storage time of the Pu based fuels. In the present case, attempt was made to develop a method for the determination of
americium as well as thorium by ICP-AES. Two emission lines of americium were identified and calibration curves were established
for determination of americium. Though the detection limit of 283.236 nm line (5 ng mL−1) of americium was found to be better than that of 408.930 nm (11 ng mL−1), the former line is significantly interfered by large amount of thorium. Three analytical lines (i.e. 283.242, 283.730 and
401.913 nm) of thorium were identified and calibration curves were established along with their detection limits. It was observed
that 283.242 and 401.913 nm line are having similar detection limits (18 and 13 ng mL−1, respectively) which are better than that of 283.730 nm (60 ng mL−1). This can be attributed to the high background of 283.273 nm channel of thorium. The spectral interference study revealed
that even small amount of americium has significant contribution on 283.242 nm channel of thorium while the other two channels
remain practically unaffected. Considering both these facts, spectral interference and analytical performance (detection limits
and sensitivity), it was concluded that 401.913 nm line is the best analytical line out of the three lines for determination
of thorium in presence of americium.
Synergistic extraction studies on Np(VI) and Pu(VI) have been carried out as a part of the programme on the synergistic extraction
of hexavalent actinides. Extraction of Np(VI) and Pu(VI) were carried out by mixtures of HTTA and TBP in benzene from aqueous
perchlorate and nitrate media. Equilibrium constant values for the various reaction equilibria involved were calculated from
the data obtained by using slope-ratio as well as Job’s method. The extraction of Np(VI) by the synergistic mixture from 1M
nitric acid indicated that the species NpO2 (TTA) (NO3). TBP was not involved in the extraction. The log values of KA, KAB and βAB were −1.5, 2.92 and 4.43, respectively for Np(VI) and −1.63, 2.50 and 4.13 respectively for Pu(VI).
DHOA (Di-n-hexyl-octanamide) is one of the alternative extractants to TBP (tri-n-butyl phosphate) known for the extraction
of uranium from moderate nitric acid medium without significant extraction of the fission products. Analytical application
of DHOA was explored to develop a methodology for determination of trace metallic constituents in uranium based nuclear materials.
This involved the separation of uranium matrix by 1.1 M DHOA-dodecane followed by the analysis of the raffinate for trace
constituents by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). A systematic study showed that four contacts
of 1.1 M DHOA-dodecane were required for quantitative extraction of U from 4 M HNO3 feed for the sample size of 1 g in 10 mL. The feasibility of using DHOA for extraction of U from trace metallic constituents
in U based fuel materials without losing trace quantities of analytes of interest was studied by using synthetic samples after
appropriate spiking of common impurities and critical elements at their required specification limits (common elements—5 ppm,
critical elements—1 ppm). A systematic study was carried out to compare the analytical performance of DHOA with TBP, which
revealed that DHOA could successfully be employed for the determination of 19 trace constituents with lower estimation limits
of 5 ppm for common impurities and 1 ppm for critical elements.
Authors:A. Godbole, P. Mapara, and Rajendra Swarup
Extraction of U(VI) by mixtures of 2-ethylhexyl 2-ethylhexylphosphonic acid (PC88A) and TOPO in cyclohexane and xylene from aqueous sulfuric acid medium has been investigated. Synergism was observed and the species responsible was identified as UO2H2Y4.TOPO. From the data equilibrium constants for the various reaction equilibria at different temperatures and the thermodynamic parameters were calculated. Antagonism was observed when alkylamide or TBP was used as the neutral donor.
Authors:P. Mapara, A. Godbole, Rajendra Swarup, and M. Nagar
Solvent extraction and extraction chromatography studies of uranium and plutonium from oxalate supernatant solutions were
carried out using 2-ethyl hexyl-2-ethyl hexyl phosphonic acid (PC88A). Based on the distribution data, it was inferred that
both the uranium and plutonium could be recovered satisfactorily from such a solution. These studies were found to be useful
in optimising the appropriate concentration of PC88A, HNO3, oxalic acid and temperature to recover more than 90% of plutonium from the large volumes of oxalate bearing waste solutions.
Spectral characteristics of the extractant and its complexing behavior with U(VI) was also studied using IR & FTIR.
Authors:K. Chetty, P. Mapara, A. Godbole, and Rajendra Swarup
Ion-exchange studies on uranium and plutonium using macroporous (MP) anion-exchange resins from an aqueous-organic solvent mixed media were carried out to develop a separation method. Out of the several water miscible organic solvents tried methanol and acetone were found to be best suited. Distribution data were obtained for U(VI) and Pu(IV) using three macroporous resins under various parameters. Based on these data, separation factors for Pu/U were calculated. Column experiments using Tulsion A-27(MP) were also carried out. The method has the advantage of loading plutonium from as low as 1M nitric acid in the presence of methanol or acetone and could be used satisfactorily for its recovery from solutions containing plutonium and uranium.
Authors:A. Sengupta, V. Adya, P. Mohapatra, S. Godbole, and V. Manchanda
This paper describes the development of a separation method for americium from the effluents emanating from anion exchange
column, used for the recovery of plutonium from analytical waste solutions. The waste contained uranium, sodium, calcium and
iron as the major impurities as estimated by ICP-AES method. ~99% pure americium was obtained by three separation steps using
solvent extraction and extraction chromatography techniques. In the first step, uranium was quantitatively separated by giving
five contacts of equal volumes of 30% TBP in n-dodecane. Fe and Na were separated in the next step using 0.1 M TODGA + 0.5 M DHOA as the extractant. In the last step, Am
was separated from the co-extracted Ca (about 76%) using CMPO loaded extraction chromatographic column. The overall recovery
was >80% with decontamination factor (D.F.) from the impurities being >3000 while the purity of the product was 99%.
Authors:V. Natarajan, S. Godbole, A. Argekar, A. Page, M. Sastry, and P. Natarajan
This paper describes the results of photoreduction of uranyl (UO22+) ion to U4+ in 0.2M HNO3 and ethanol using a 308 nm XeCl excimer laser. The effects of different concentrations of ethanol and the addition of sulfamic acid on the quantum yield for U4+ formation are discussed.