Y. Komori

Solvent extraction of Zr and Hf from hydrochloric acid using tributylphosphate for the extraction of element 104, rutherfordium

Summary For the solvent extraction experiment on element 104 (Rf), solvent extraction of Zr and Hf as its homologues was performed in tributylphosphate (TBP)/hydrochloric acid (HCl) system using the carrier-free radiotracers 88Zr and 175Hf. Time dependences of the distribution ratios of Zr and Hf were investigated using 6.1 and 10.0M HCl and 0.5 and 2.0M TBP benzene solutions. The distribution ratios in equilibrium were determined for these elements as a function of HCl concentrations in the range of 4.1-10.2M. We found that the neutral chloride complexes of Zr and Hf were formed and extracted into the organic phase within 20 min in HCl with a concentration higher than 6 M. From the results, we propose that solvent extraction of Rf from 4-8M HCl into 2.0M TBP benzene is suitable for investigating the chloride complexation properties of Rf. In addition, for the development of the rapid liquid-liquid extraction apparatus, three types of microchannel devices, namely, a micro reactor, capillary tube and micro-chemical chip, were tested as a mixing-solution part in the apparatus. The chemical reactions of Zr and Hf in the extraction were found to be fast only when using the microchemical chip, which is important for investigations with the 68-s 261Rf.

Excitation function of the alpha particle induced nuclear reactions on enriched 116Cd, production of the theranostic isotope 117mSn

117mSn is one of the radioisotopes can be beneficially produced through alpha particle irradiation. The targets were prepared by deposition of 116Cd metal onto high purity 12 μm thick Cu backing. The average deposited thickness was 21.9 μm. The beam energy was thoroughly measured by Time of Flight (TOF) methods and proved to be 51.2 MeV. For the experiment the well-established stacked foil technique was used. In addition to the Cd targets, Ti foils were also inserted into the stacks for energy and intensity monitoring. The Cu backings were also used for monitoring and as recoil catcher of the reaction products from the cadmium layer. The activities of the irradiated foils were measured with HPGe detector for gamma-ray spectrometry and cross section values were determined. As a result excitation functions for the formation of 117mSn, 117m,gIn, 116mIn, 115mIn and 115m,gCd from enriched 116Cd were deduced and compared with the available literature data and with the results of the nuclear reaction model code calculations EMPIRE 3.2 and TALYS 1.8. Yield curves were also deduced for the measured nuclear reactions and compared with the literature.

Production cross-sections of radionuclides from α-induced reactions on natural copper up to 50MeV.

The excitation functions were measured for the (nat)Cu(α,x)(66,67)Ga,(65)Zn,(57,58,60)Co reactions in the energy range of 16.5 -50MeV. A conventional stacked-foil activation technique combined with HPGe γ-ray spectrometry was employed to determine cross-sections. The measured cross-sections were critically compared with relevant previous experimental data and also with the evaluated data in the TENDL-2014 library. Present results confirmed some of the previous experimental data, whereas only a partial agreement was found with the evaluated data. The measured data are useful for reducing the existing discrepancies in the literature, to improve the nuclear reaction model codes, and to enrich the experimental database towards various applications.

Development of an automated batch-type solid-liquid extraction apparatus and extraction of Zr, Hf, and Th by triisooctylamine from HCl solutions for chemistry of element 104, Rf

Abstract Solid-liquid extraction of the group 4 elements Zr and Hf, which are homologues of Rf (Z = 104), and Th, a pseudo homologue, by triisooctylamine (TIOA) from HCl solutions was performed by batch method. After examining the time required to reach extraction equilibrium for these elements in various concentrations of TIOA and HCl, we investigated in detail variations in the distribution coefficients (Kd) with TIOA and HCl concentrations. The Kd values of Zr and Hf increased with increasing the HCl and TIOA concentrations, suggesting an increase in the abundance of the anionic chloride complexes of Zr and Hf. On the other hand, the Kd values of Th were low in all the HCl concentrations studied, implying that Th does not form anionic species dominantly. We developed a new automated batch-type solid-liquid extraction apparatus for repetitive experiments on transactinide elements. Using this apparatus, we performed solid-liquid extraction employing the radioactive nuclides 89mZr and 175Hf produced by nuclear reactions and transported continuously from the nuclear reaction chamber by the He/KCl gas-jet system. It was found that the distribution behaviors in 7–11 M HCl are almost constant in the time range 10–120 s, and the Kd values are consistent with those obtained in the above manual experiment. This result suggests that the chemical reactions in the extraction process reach equilibrium within 10 s for Zr and Hf under the present experimental conditions. It took about 35 s for the extraction using the apparatus. These results indicate the applicability of the present extraction using the developed apparatus to 261Rf (T1/2 = 68 s) experiments.

Solvent extraction of trivalent actinides with di(2-ethylhexyl) phosphoric acid

Abstract We carried out solvent extraction on the trivalent actinides of Am, Cm, Cf, and Fm and the lanthanides (except Pm) using di(2-ethylhexyl)phosphoric acid (HDEHP) in benzene by a batch method. The extraction constants of the HDEHP complexes for these elements were determined systematically under identical conditions. The tetrad effect was clearly observed in the variation of the extraction constants of the lanthanide series. We found that the extraction constant for Fm(III) is much smaller than that for Dy(III), which have similar ionic radii. The extraction constants for Am(III), Cm(III), and Cf(III) are similar to those for corresponding Ln(III) having similar ionic radii. Two possibilities that account for the lower extraction constant of Fm(III) is suggested.

Cross section measurement of alpha particle induced nuclear reactions on natural cadmium up to 52 MeV

Cross sections of alpha particle induced nuclear reactions have been measured on thin natural cadmium targets foils in the energy range from 11 to 51.2MeV. This work was a part of our systematic study on excitation functions of light ion induced nuclear reactions on different target materials. Regarding the cross sections, the alpha induced reactions are not deeply enough investigated. Some of the produced isotopes are of medical interest, others have application in research and industry. The radioisotope 117mSn is a very important theranostic (therapeutic + diagnostic) radioisotope, so special care was taken to the results for that isotope. The well-established stacked foil technique followed by gamma-spectrometry with HPGe gamma spectrometers were used. The target and monitor foils in the stack were commercial high purity metal foils. From the irradiated targets 117mSn, 113Sn, 110Sn, 117m,gIn, 116mIn, 115mIn, 114mIn, 113mIn, 111In, 110m,gIn, 109mIn, 108m,gIn, 115gCd and 111mCd were identified and their excitation functions were derived. The results were compared with the data of the previous measurements from the literature and with the results of the theoretical nuclear reaction model code calculations TALYS 1.8 (TENDL-2015) and EMPIRE 3.2 (Malta). From the cross section curves thick target yields were calculated and compared with the available literature data.

Solvent extraction using carrier-free radiotracers of Mo and W from HCl and HCl/LiCl solutions into Aliquat 336

We performed solvent extraction of 99Mo and 181W from HCl and HCl/LiCl solutions into Aliquat 336-chloroform solutions. It is found that the extracted anionic species of Mo and W have a net charge of −1 from the logD versus log[Aliquat 336] plots. At high H3O+ concentrations, the D values in HCl were lower than those in HCl/LiCl, probably because of the protonation of anionic Mo and W species in HCl. The D values of Mo were significantly higher than those of W, suggesting that the extracted Mo and W species are different from each other and/or have different stabilities in HCl.

Production of 88Nb and 170Ta for chemical studies of element 105, Db, using the GARIS gas-jet system

A technology to utilize radioisotopes of Nb and Ta was developed for chemical studies of element 105, Db, by coupling a gas-jet transport system to the RIKEN gas-filled recoil ion separator (GARIS). 88Nb and 170Ta were generated via the natGe(19F, xn)88Nb and natGd(19F, xn)170Ta reactions, respectively. They were separated by GARIS and extracted by the gas-jet method to a chemistry laboratory under the almost same experimental conditions for 262Db produced in the 248Cm(19F, 5n)262Db reaction. Yields of 88Nb and 170Ta at the chemistry laboratory were optimized by changing the setting parameters of the GARIS gas-jet system, such as magnetic field of GARIS, energy degrader and shutter for recoil ions, and volume of the recoil transfer chamber.

Extraction behavior of rutherfordium as a cationic fluoride complex with a TTA chelate extractant from HF/HNO3 acidic solutions

Abstract The aim of this study was to identify relevant Rf chemical species by using reversed-phase extraction chromatography with 2-thenoyltrifluoroacetone (TTA) resin as the stationary phase. Because TTA can be used to extract specific metal ions, the distribution ratios of the system enabled determination of the specific complex formation constant of Rf. We performed several experiments on chemical systems with Zr, Hf, No, and Rf, determined their adsorption coefficients, and deduced the Kd values for Rf.

Online chemical adsorption studies of Hg, Tl, and Pb on SiO2 and Au surfaces in preparation for chemical investigations on Cn, Nh, and Fl at TASCA

Abstract Online gas-solid adsorption studies with single-atom quantities of Hg, Tl, and Pb, the lighter homologs of the superheavy elements (SHE) copernicium (Cn, Z=112), nihonium (Nh, Z=113), and flerovium (Fl, Z=114), were carried out using short-lived radioisotopes. The interaction with Au and SiO2 surfaces was studied and the overall chemical yield was determined. Suitable radioisotopes were produced in fusion-evaporation reactions, isolated in the gas-filled recoil separator TASCA, and flushed rapidly to an adjacent setup of two gas chromatography detector arrays covered with SiO2 (first array) and Au (second array). While Tl and Pb adsorbed on the SiO2 surface, Hg interacts only weakly and reached the Au-covered array. Our results contribute to elucidating the influence of relativistic effects on chemical properties of the heaviest elements by providing experimental data on these lighter homologs.