Effects of radiation on the extraction system composed of DEHPA extractant and DTPA aqueous solution containing nitrate were
studied by measuring distribution ratios of Am(III) and Nd(III) with the extractant and DTPA solution either one of which
was irradiated with60Co γ-rays or the organic—aqueous mixed phase irradiated under continuous stirring. The irradiation causes an increase of Df
and a decrease of the Nd/Am separation factor β, to an especially large extent in the mixed phase system. These effects are
due firstly to the radiolytic decomposition of DTPA and secondarily to the formation of MEHPA. The replacement of nitrate
with lactate stops the degradation of DTPA and DEHPA resulting in the retardation of increase of Df and a decrease of separation
factor. The DEHPA-DTPA-lactic acid system is concluded to sustain absorption of radiation at an absorbed dose up to 200 Wh·I−1 in the partitioning of transplutonium elements in HLW.
Authors:V. Ramakrishna, S. Patil, L. Reddy, and A. Reddy
Extraction of Tm(III), from thiocyanate media, by different sulfoxides (R2SO) has revealed that the extractable complex is Tm(SCN)3·4 R2SO. When mixtures of DPSO and HTTA are used for the extraction of Tm(III) from thiocyanate or perchlorate media, synergistic
enhancement of the extraction of Tm(III) results. The complexes responsible for the enhanced extraction are Tm(TTA)3·DPSO and Tm(TTA)3·2 DPSO when perchlorate media were employed for the extraction and Tm(SCN)(TTA)2·2 DPSO and Tm(SCN)2(TTA)·3 DPSO, in addition to the above two when a thiocyanate medium was employed for the extraction. Values of equilibrium
constants for some equilibria encountered in the extraction of Am(III) and Tm(III) by mixtures of DPSO and HTTA are given.
Authors:A. Jadhav, V. Goyal, S. Pattanaik, P. Shankaran, and S. Patil
The extraction of Am(III), Pu(IV) and U(VI) as representatives of tri-, tetra- and hexavalent actinides by dibutyl-N,N-diethylcarbamoylmethylenephosphonate (DBDECMP) from nitric acid solution has ben studied with an objective of understanding the extraction mechanism. The dependence of the distribution ratios of the actinide ions was studied as a function of the concentration of H+, DBDECMP and NO
. The extraction data revealed that all the three actinide ions are extracted as their neutral nitrate complexes solvated by DBDECMP which behaves as neutral extractant only. The absorption spectra of DBDECMP and TBP extracts of these actinide ions were recorded. From the close similarity of these spectra it is inferred that DBDECMP acts as a monodentate extractant in the present system.
Distribution behavior of Ce(III), Am(III), and Cm(III) between tri-n-butyl phosphate solution and molten calcium nitrate hydrate Ca(NO3)2·RH2O or molten calcium chloride hydrate CaCl2·RH2O was studied radiochemically. In Ca(NO3)2·RH2O systems, maximum separation factors of Ce and Cm to Am were observed to be 12 (Ce/Am) and 1.7 (Cm/Am). The distribution
ratios of these elements increased with the decrease of water activity in the hydrates, and the extractabilities at the water
deficient region was less sensitive compared to those at the water abundant region. This trend was similar to the coordination
circumstance change observed in electronic absorption spectra of Nd(III) in the hydrates.
Authors:M. Watanabe, R. Tatsugae, Y. Morita, and M. Kubota
Back-extraction of tri- and tetravalent actinides from diisodecylphosphoric acid (DIDPA) is studied using hydrazine carbonate as back-extractant. In experiments using 0.5M DIDPA–0.1M TBP n-dodecane solution, Am(III), Eu(III), Pu(IV) and Np(IV) are back-extracted, and the distribution ratios are decreased with an increase of hydrazine carbonate concentration. The back-extraction equilibria are confirmed by slope analysis in consideration of neutralization between DIDPA and hydrazine carbonate, which occurs quantitatively during back-extraction. In particular, oxidation of Np(IV) to Np(V) during back-extraction is observed by measuring absorption spectra. The hydrazinium ion acts as an oxidation reagent in the back-extraction of Np(IV). Separation factors of those metals are compared with the results of HDEHP. Hydrazine carbonate back-extracts Np(IV) more selectively from DIDPA than from HDEHP.
Authors:Ping Zhang, Hairong Wang, Jianchen Wang, and Jing Chen
To simplify TRPO process, a novel ligand, N,N’-dimethyl-3-oxa-glutaramic acid (DMOGA), was synthesized and used for stripping
of An(III, IV) from 30% TRPO-kerosene. The distribution ratios for transuranium elements, including Np(IV), Pu(IV), Am(III),
and some fission products, including Eu(III), Fe and Zr between 30% TRPO-kerosene and various HNO3-DMOGA solutions were measured. An(III, IV) and Ln(III) extracted to TRPO from simulated high level liquid waste could be
recovered with an efficiency of 99.9% above in one stream with a 3-stage crosscurrent strip experiment with 0.2M DMOGA in
HNO3 solution. Using this new agent, the back extraction of TRU elements from loaded TRPO phase becomes more simple and practical.
Therefore, the original TRPO process could be simplified.
Authors:P. Naik, P. Dhami, S. Misra, U. Jambunathan, and J. Mathur
Silica-gel has been used as an inert support for the extraction chromatographic separation of actinides and lanthanides from HNO3 and synthetic high level waste (HLW) solutions. Silica-gel was impregnated with tri-butyl phosphate (TBP), to yield STBP; 2-ethylhexyl phosphonic acid, mono 2-ethylhexyl ester (KSM-17, equivalent to PC-88A), SKSM; octyl(phenyl)-N,N-diisobutyl carbamoylmethylphosphine oxide (CMPO), SCMPO; and trialkylphosphine oxide (Cyanex-923), SCYN and sorption of Pu(IV), Am(III) and Eu(III) from HNO3 solutions was studied batchwise. Several parameters, like time of equilibration, HNO3 and Pu(IV) concentrations were varied. The uptake of Pu(IV) from 3.0M HNO3 followed the order SCMPO>SCYN>SKSM>STBP. With increasing HNO3 concentration, DPu increased up to 3.0M of HNO3 for STBP, SKSM and SCMPO and then decreased. In the case of Am and Eu with SCMPO, the D values initially increased between 0.5 to 1.0M of HNO3, remained constant up to 5.0M and then slightly decreased at 7.5M. Also, the effects of NaNO3, Nd(III) and U(VI) concentrations on the uptake of Am(III) from HNO3 solutions were evaluated. With increasing NaNO3 concentration up to 3.0M, DAm remained almost constant while it was observed that it decreases drastically by adding Nd(III) or U(VI). The uptake of Pu and Am from synthetic pressurized heavy water reactor high level waste (PHWR-HLW) in presence of high concentrations of uranium and after depleting the uranium content, and finally extraction chromatographic column separation of Pu and Am from U-depleted synthetic PHWR-HLW have been carried out. Using SCMPO, high sorption of Pu, Am and U was obtained from the U-depleted HLW solution. These metal ions were subsequently eluted using various reagents. The sorption results of the metal ions on silica-gel impregnated with several phosphorus based extractants have been compared. The uptake of Am, Pu and rare earths by SCMPO has been compared with those where CMPO was sorbed on Chromosorb-102, Amberchrom CG-71 and styrene divinylbenzene copolymer immobilized in porous silica particles.
The present paper describes a novel type of extractant for actinides called bis (dioctylcarbamoylmethyl) sulfoxide which neither contains phosphorus nor entails the addition of tributyl phosphate as phase modifier for extraction. This extractant, abbreviated as CMSO, has been found to be freely soluble in dodecane and to form no third phase even with concentrations of nitric acid as high as 10M. The distribution ratios for the extraction of Am(III), Pu(IV) and U(VI) at trace levels have been found to be 13, 220 and 11, respectively, from 5M nitric acid using 0.2M CMSO in dodecane and those for back-extraction have been found to be 2×10–4, 8×10–3 and 5×10–2 using 0.01M nitric acid, 0.1M oxalic acid and 0.35M sodium carbonate, respectively. Similar distribution ratios were obtained with the recycled extractant. Extraction was found to be very rapid. Eu(III) and Sr(II) were found to be moderately extracted with distribution ratios of 2 and 0.77, respectively, while the extraction of Cs(I) was negligible (KD=0.005).
Authors:A. Kumar, J. Sonawane, N. Rathore, H. Kapur, A. Venugopalan, and D. Bajpai
Partitioning of minor alpha-emitting actinides, especially U, Pu and Am from medium active alkaline waste is possible from intermediate level liquid wastes (ILLW) produced during spent fuel reprocessing following Purex process. This paper deals with the efficient removal of alpha-activity from ILLW by solvent extraction process. Counter current batch extraction with O/A ratio 2:1 as well as multistage mixer settler has demonstrated that most of the alpha-activity was removed from the alkaline effluents using 20% Versatic-10 (V-10) in dodecane after giving 3 to 4 contacts, thus converting alkaline waste as non-alpha waste. Under the optimum conditions (pH 9.0-9.5 and VA-10), both Pu(IV) and Am(III) are highly extractable whereas U(VI) is relatively poorly extracted. To assess the applicability of this process for regular treatment of the waste, a feasibility study on pilot plant scale using six stage mixer settler was operated to treat the ILLW. The results indicated that almost >99.90% alpha-emitting actinides are removed. Dilute nitric acid (0.5M HNO3) served as the most efficient strippant for all these actinides. This facilitate an easy regeneration of the extractant which can be recycled. This method is useful in obtaining alpha-free wastes and had positive impact on ease and safety aspects during subsequent waste treatment and long term storage.
Authors:Ruiqin Liu, Yuezhou Wei, Yuanlai Xu, Shigekazu Usuda, Seongyun Kim, Hiromichi Yamazaki, and Keizo Ishii
In order to develop a direct separation process for trivalent minor actinides from fission products in high level liquid waste
(HLLW) by extraction chromatography, a novel macroporous silica-based 2,6-bis(5,6-diisohexyl)-1,2,4-triazin-3-yl)pyridine resin (isohexyl-BTP/SiO2-P resin) was prepared. The content of isohexyl-BTP extractant in the resin was as high as 33.3 wt%. The resin exhibited much higher adsorption affinity for Am(III)
in 2–3 M (mol/L) HNO3 solution over U and FP which are contained in HLLW. The kinetic data were analyzed using pseudo-second-order equation. The
results suggested that the Eu(III), Gd(III), and Dy(III) adsorption was well explained by the pseudo-second-order equation.
Quantitative desorption for adsorbed elements was achieved by using H2O or thiourea as eluting agents. However, the kinetics of adsorption and desorption were rather slow and this drawback needs
to be resolved. Stability of the resin against HNO3 was also examined. It was found that the resin was considerably stable against ≤4 M HNO3 solution for the reasons of an extremely small leakage of the extractant into the solution from the resin and the adsorption
performance keeping for rare earths in 3 M HNO3 solution.