Volume 101, Issue 12

Redox potentials of Sg in acid solutions as a function of pH are predicted. The work is based on earlier estimates of standard redox potentials via a correlation with multiple ionization potentials of group-6 elements calculated using a multiconfiguration Dirac–Fock method. As expected, most of the potentials, except for those from the M 3+ to the M 2+ and M (M = Cr, Mo, W and Sg) states, decrease with increasing pH, with the most pronounced effect for the M IV /M III couple. The obtained values show that the reduction of Sg to the IV and III states should be feasible in HCl solutions in a pH range from 0 to 3 or 4.

The separation of minor actinides from high level liquid waste (HLLW) belongs to the principal challenges of advanced nuclear fuel treatment. We studied in this work several diamides of dipicolinic acid for direct separation of trivalent actinides from post-PUREX raffinate. The N , N ′-diethyl- N , N ′-di- meta -tolyldipicolinamide, Et( m )TDPA, exhibited the highest Am(III) extraction ability and sufficient Am(III)/Eu(III) selectivity (SF Am/Eu  ≥ 5) from all tested derivatives. Am(III) and Eu(III) extraction with the Et( m )TDPA into solvents of different polarities was studied in detail. The extraction abilities of extractants dissolved in polar nitro- or fluorinated solvents were significantly higher than those in less or low polar solvents like hexyl methyl ketone, 1-octanol, chloroform, toluene, etc. Et( m )TDPA in nitrobenzene provided selective separation of americium from lanthanides (SF Am/Ln  > 5) and from the majority of other fission products (SF > 150) present in model PUREX raffinate. The co-extraction of some undesirable elements as Zr and Pd was significantly suppressed by addition of oxalic acid and HEDTA to the raffinate solution.

The extractant-impregnated polymeric beads (EIPBs), containing polyethersulfone as base polymer and 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) as an extractant, were prepared by phase inversion method. These EIPBs were characterized by FTIR, TGA and SEM techniques. The beads were found to have excellent acid stability, since these did not exhibit any structural deformation or loss of the extractant into aqueous nitric acid solution (6 M), for a period of 15 d. The feasibility of Pu(IV) extraction, using these beads, from nitric acid solution was tested by batch equilibration method. Parametric dependence of Pu(IV) extraction on experimental variables, like strength of nitric acid, equilibration time, Pu(IV) concentration, etc. , was investigated. The present study also addressed the important practical issues, like maximum loading capacity and the reusability of these beads. Under optimized conditions, equilibrium capacity and maximum loading capacity for Pu(IV) were found to be 2.03 and 7.50 mg per gram of the swollen beads, respectively. The reusability of the beads was also ascertained by repetitive extraction-stripping of Pu(IV) up to 7 cycles of operation, without significant change in their extraction performance. The extraction of Pu(IV) by the blank polymeric beads was observed to be almost negligible, under the similar experimental conditions.

This paper describes our studies on the partitioning of actinides from high level liquid waste of PUREX origin employing a supported liquid membrane technique. The process uses a solution of DHDECMPO in n -dodecane as a carrier with poly tetra fluoro ethylene support and a mixture of citric acid, formic acid and hydrazine hydrate as a receiving phase. Transport studies are carried out for 241 Am under different experimental conditions to optimize the transport parameters such as feed acidity, carrier concentration and effect of uranium, Nd(III) and salt concentration in the feed. Studies indicated good transport of neptunium, americium and plutonium across the membrane from a nitric acid medium. Under the optimized conditions the transport of 241 Am has been studied for uranium depleted synthetic PHWR-HLW and finally the technique is used for the partitioning of alpha emitters from an actual HLW after reprocessing. A high concentration of uranium in the feed is found to retard the transport of americium, suggesting the need of prior removal of uranium from the waste. Separation of actinides from uranium-lean simulated as well as actual HLW has been found to be feasible using the above described technique.

In the present study, the suitability of Raman spectroscopy for nuclear forensics is proven by a systematic investigation of laboratory-prepared synthetic and industrial uranium ore concentrate (UOC) samples, of different origin and with wide range of impurity content. Besides the identification of the compound type, the identification of process-related impurities observed in these samples is reported for the first time. Both handheld and laboratory Raman spectrometers were used in the measurements. The ability to measure different UOCs and the sufficient sensitivity of the handheld device demonstrate its usefulness in nuclear safeguards and nuclear security applications. Even more importantly in such a context, the likely identity of process-related impurities could be verified by Raman Spectroscopy in the present work, allowing to draw conclusions on the process history of the sample.

Acid–base titrations of magnetite/graphene oxide (M/GO) and Sr(II) adsorption onto M/GO were operated to investigate surface properties of M/GO and surface complexation bonding interactions between Sr(II) and M/GO. Experimental results showed that Sr(II) adsorption onto M/GO was facilitated by a high pH value and a low ionic strength. Modeling results exhaustively explained the changes of adsorption morphological at different pH and ionic strengths. Thermodynamic parameters ( ΔH ○ , ΔS ○ , and ΔG ○ ) calculated from the adsorption isotherms showed the adsorption of Sr(II) onto M/GO composite was an endothermic and spontaneous process. M/GO could be separated by magnetic separation from aqueous solution in large scale. The adsorption performance suggests M/GO could be a promising adsorbent material for the preconcentration and separation of radiostrontium from aqueous solution in radionuclide pollution cleanup.

Since 201 Tl is widely used in SPECT and porphyrins are important biological carriers, we tried to obtain a stable complex between thallium and porphyrins. The thallium porphyrin complex was synthesized by reaction of 201 Tl(III) with porphyrin at 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (H 2 PFPP) for 60 min at 100°C. The complex was analysed via TLC and HPLC stability (in the final formulation and human serum) and the partition coefficient of the complex was determined. The biodistribution of the labeled compound in vital organs of wild-type rats was investigated. The complex was prepared with high radiochemical purity (> 99% ITLC, > 99% HPLC, specific activity: 13–14 GBq/mmol) (log  P  = 1.92). The stability of the Tl +3 -complex seems to be low since the complex or free thallium is rapidly cleared through the kidneys and the liver.

Determining the gross alpha activity concentration of water samples is one way to screen for waters whose radionuclide content is so high that its consumption could imply surpassing the Total Indicative Dose as defined in European Directive 98/83/EC. One of the most commonly used methods to prepare the sources to measure gross alpha activity in water samples is desiccation. Its main advantages are the simplicity of the procedure, the low cost of source preparation, and the possibility of simultaneously determining the gross beta activity. The preparation of the source, the construction of the calibration curves, and the measurement procedure itself involve, however, various factors that may introduce sufficient variability into the results to significantly affect the screening process. We here identify the main sources of this variability, and propose specific procedures to follow in the desiccation process that will reduce the uncertainties, and ensure that the result is indeed representative of the sum of the activities of the alpha emitters present in the sample.