Volume 101, Issue 11

Continuous liquid–liquid extraction of short-lived radionuclides has traditionally been performed with the SISAK system consisting of static mixers and H-centrifuges for phase separation. SISAK operates at flow rates of typically 1 mL/s. Thus, it produces large volumes of radioactive liquid waste that is difficult to dispose of. Therefore, it has been aimed to develop and use a further miniaturised extraction unit based on microtechnology and precision engineering to reduce the flow rate by at least two orders of magnitude. The accordingly developed MicroSISAK device is a micro membrane extractor in which a micromixer element with 2 × 16 feed channels of 30 µm width followed by a 60 µm high mixing chamber is used for intimately contacting the aqueous and organic phase. Subsequent phase separation is achieved via hydrophobic Teflon membranes with a pore size of 1 µm. The MicroSISAK device has been tested and optimized with radiotracers of the group-4 elements Zr and Hf in the system H 2 SO 4 /trioctyl amine (TOA) in toluene. At a temperature of 58°C and a flow rate of 0.2 mL/min of both phases, extraction yields of 87 ± 3% were achieved. The transport time from the micromixer to the first Teflon membrane was in this case 3.9 s. It can be shortened to 1.56 s at a flow rate of 0.5 mL/min. Under similar conditions, the extraction yield of 99 m Tc milked from a  99 Mo generator in the system HNO 3 /tetraphenyl arsonium chloride (TPAC) in chloroform was 83 ± 3%. In an on-line experiment at the TRIGA Mainz reactor, short-lived Tc isotopes produced in the fission of 235 U with thermal neutrons were transported by a He/KCl gas-jet to the chemistry apparatus, deposited by impaction, dissolved in 0.01 mol/L HNO 3 /KBrO 3 , and extracted into 10 −4  mol/L TPAC in chloroform in MicroSISAK. The separated phases were transported via capillaries to two separate flow-through cells positioned in front of two Ge detectors. The extraction yield determined as the ratio of the Tc γ -ray activities in both detectors was 76 ± 1%. With this experiment, it was demonstrated that MicroSISAK is in principle ready for an on-line experiment for the chemical characterization of the superheavy element bohrium, element 107. However, the detection of α -particle activities by liquid scintillation counting still needs to be worked out.

Single crystals of [Th(TMP) 6 (NO 3 ) 2 ][Th(TMP) 2 (NO 3 ) 5 ] 2 ( 1 ), [Th(TMP) 4 (NO 3 ) 3 ][Th(TMP) 2 (NO 3 ) 5 ] ( 2 ), [U(DMP) 3 (NO 3 )] ( 3 ), [Np(DMP) 3 (NO 3 )] ( 4 ), and [Pu(DMP) 2 (NO 3 ) 2 (H 2 O)]·H 2 O ( 5 ) have been synthesized and their structures have been determined by X-ray analysis. IR and optical spectra of polycrystalline compounds 3 and 4 were measured at room temperature. The Th(IV) is crystallized as two complexes with TMP molecular ligands and NO 3 anions in coordination environment. The Th atoms in cationic moieties of 1 and 2 are characterized by coordination number of 10 and in the anionic moieties by coordination number of 12. Compounds of U(IV), Np(IV) and Pu(IV) were obtained with two different anions (NO 3 and DMP) in coordination environment of the central atom. U(IV) and Np(IV) compounds are isostructural and the main motif of structure is made of infinite chains of [An(DMP) 3 (NO 3 )] n , twisted around hexagonal axes. In the structure of Pu(IV) the main structural motif is made of infinite chains [Pu(DMP) 2 (NO 3 ) 2 (H 2 O)] n , extending along the b axis. The coordination numbers of An(IV) are equal to 8 for U and Np, and 9 for Pu. The difference in the structure and composition of formed compounds Th and U, Np, Pu could be explained by hydrolysis of TMP at the synthesis conditions.

The reduction of PuO 2 (am) by Fe(II) in the presence and absence of hematite was studied over a range of pH values and oxidation/reduction potentials. In contrast to thermodynamic predictions, the presence of hematite did not have a major effect on the overall reduction of PuO 2 (am) to aqueous Pu(III). Instead the aqueous Pu(III) concentrations at longer time frames were accurately predicted using the measured Fe(II) concentration and existing thermodynamic data for the reaction: H 2 O + H + + Fe 2+ + PuO 2 (am) ⇌ Pu 3+ + Fe(OH) 3 (am) with log  K  =− 0.6. The accuracy of this approach in all solutions containing aqueous Fe(II), coupled with the apparent lack of oxidation of Fe(II) by O 2 (g), suggests that the Fe(OH) 3 (am) is formed by the oxidation of Fe(II) to Fe(III) by radiolysis. The continued generation of reactive amorphous iron hydroxide by radiolysis prevents thermodynamic equilibrium from being reached with more stable ferric oxide compounds, except possibly under acidic conditions where amorphous ferric hydroxide is soluble. The use of measured pe values, instead of aqueous Fe(II) measurements, also yields reasonable predictions of the final Pu(III) concentrations although the predictions are more uncertain.

Four new alkyl-pyridinedicarboxyamides (R-PDA; R = butyl, octyl, decyl, dodecyl) were synthesized and used as extractants for partitioning minor actinides from high level radioactive waste using extraction chromatography. The R-PDAs were successfully impregnated into XAD resins (Amberlite). The prepared adsorbents, R-PDA/XAD, exhibited moderate adsorptions of both Am(III) and Eu(III), and separation between Am(III) and Eu(III), over a high HNO 3 concentration range (3–5 M). Deterioration of the prepared adsorbent as a result of contact with HNO 3 solution was prevented by using R-PDAs containing longer alkyl groups. The equilibrium data for Eu(III) were analyzed using Langmuir and Freundlich isotherm models. The adsorption of Eu(III) ions onto the R-PDA/XAD was fitted better to the Langmuir isotherm than to the Freundlich isotherm. The maximum adsorption capacity was determined to be 24.2 mg Eu/g (R-PDA/XAD).

Extraction behavior of Np 4+ and Pu 4+ was investigated using several tetraalkylsubstituted diglycolamide (DGA) extractants such as N , N , N ′, N ′-tetrapentyl-diglycolamide (TPDGA), N , N , N ′, N ′-tetrahexyl diglycolamide (THDGA), N , N , N ′, N ′-tetraoctyl diglycolamide (TODGA), and N , N , N ′, N ′-tetradecyl diglycolamide (TDDGA). The organic phases used were 0.1 M solutions of the diglycolamide extractants in n -dodecane modified with 30% iso -decanol for avoiding third phase formation while the aqueous phases contained dilute nitric acid solutions spikes with the radiotracers. The stoichiometry of the extracted species was ascertained by ligand concentration variation experiments and was found to be M(NO 3 ) 4  · 2L, where M was Np and Pu and L was the substituted DGA ligand. In general, the extraction equilibrium constant (log  K ex ) values for both Np 4+ and Pu 4+ showed an increasing trend with increasing alkyl group chain length and the log  K ex values were higher for Pu 4+ as compared to those for Np 4+ . While for Np 4+ , the K ex values were 7.03 ± 0.04 for TPDGA which increased steadily up to 7.98 ± 0.05 for TDDGA, for Pu 4+ , the respective value for TPDGA was 7.32 ± 0.05 which increased to 7.78 ± 0.03 for TDDGA. Thermodynamic parameters were also determined for the two-phase extraction equilibrium reaction.

Radioyttrium (containing 86 Y, 87 Y and 88 Y) was produced by irradiating a  nat SrCO 3 target with 15 MeV proton beam at a current of 30 µA for 12 min. A synthesized ion imprinted (IIP) and control polymer (CP) nanoparticles as sorbents were used for the separation of radioyttrium from strontium. The sorbents were characterized by Fourier Transform Infra-red spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX), Thermogravimetric analysis (TGA) and Surface area analysis. Effect of various parameters such as pH, mass sorbent, nature and volume of eluent were investigated on the percent extraction of radioyttrium ion using IIP and CP particles. Chemical and radionuclidic purity were determined by ICP-AES and HPGe detector gamma-ray spectrometry, respectively. The radioyttrium recovery yield was 99.5% and the stable Sr content in the final product was estimated to be 4.5 µg mL −1 . In conclusion, the suggested method in this manuscript can be used for the production of other 86/87 Y radionuclides.

The binding sequence of the regulatory peptide Neurotensin, NT(8-13), represents a promising tumour-specific vector for the development of radiopeptides useful in nuclear oncology for the diagnosis (imaging) and therapy of cancer. A number of radiometal-labelled NT(8-13) derivatives have been reported, however, the effect of the spacer which connects the vector with the radiometal complex has yet not been investigated systematically. Because a spacer moiety can influence potentially important biological characteristics of radiopeptides, we synthesized three [DOTA( 177 Lu)]-X-NT(8-13) derivatives and evaluated the effect of a spacer (X) on the physico-chemical properties of the conjugate including lipophilicity, stability, and in vitro receptor affinity and cell internalization.

Instrumental neutron activation analysis (INAA) was used to investigate REEs in carbonatite from Kpong southeastern, Ghana. Total rare earth element (TREEs) obtain were in the range of 540 mg/kg to 705 mg/kg. The total number of rare earth elements (REEs) determined by INAA in the carbonatite rocks from Kpong were 11, namely; La, Ce, Nd, Sm, Eu, Tb, Dy, Ho, Tm, Yb, Lu. The INAA results from the carbonatite show a high enrichment of light rare earth elements (LREEs) deposits, marking the Kpong carbonatite as a potential REE source.

Age-dating of single plutonium oxide particles ∼ 1 µm in diameter was demonstrated using eight particles. For this demonstration, the particles were prepared from a standard reference material SRM-947 that had been stored for 3.9 years since the last Pu purification. The Pu particles were separately dissolved, and Am and Pu were chemically separated from the solution via anion-exchange chromatography. The isotope ratios of Am and Pu in the eluted fractions were measured using a high-resolution inductively coupled plasma mass spectrometer (HR-ICP-MS). The precision and accuracy of the Pu age were improved through the addition of an 243 Am spike to the sample solutions and by the trace chemical separation of Pu and Am. The determined age in this work was in good agreement with the expected age with high accuracy (deviation: 7.1–105 days) and precision (uncertainty: 0.16–0.5 years ( k  = 1)). These results indicate that a combination of ICP-MS and chemical separation after spiking with 243 Am provides an effective tool for the analysis of environmental samples collected during nuclear safeguard inspections.