Irrespective of low bioavailability, some plant species accumulate Y and rare earth elements (REEs) to a great extent (accumulator species). The uptake mechanisms of Y and REEs were investigated for autumn fern, one of accumulator species. For comparison, plant species which accumulated poorly REEs (non-accumulator species) were also studied. In the present investigation, two noticeable phenomena were observed. (I) Autumn fern showed no ionic-radius dependence of Y-REE uptake by leaves, while non-accumulator species showed an extremely high uptake for Y compared with REEs. (II) Y-REE uptake by autumn fern was influenced by the addition of chelating reagents to the uptake solution, while no effect was observed for non-accumulator species.
With the aim of preparing carrier-free 28Mg and 47Ca simultaneously, Ti, V and Fe targets were examined by irradiating with high-energy ions of 12C, 14N and 16O accelerated by the RIKEN Ring Cyclotron. Among the targets, V gave the highest cross section for the formation of both 28Mg and 47Ca irrespective of the kind of beams. The cross section for the formation of 28Mg by the reactions of Ti, V and Fe targets with ion beams increased in the order of 12C < 16O<14N. On the other hand, the three beams exhibited almost the same cross sections for the formation of 47Ca by the reaction of a given target. Titanium and V were selected as prospective targets and 14N as a suitable beam for the production of 28Mg and 47Ca. Chemical separation procedures of the radiotracers in carrier- and salt-free states have been established by using cation exchange resins. The recovery yields of 28Mg and 47Ca from Ti target were 70 and 90%, respectively, and the decontamination factor was less than 10-5. The recovery yields of 28Mg and 47Ca from V target were 80% and the decontamination factor was less than 10-7.
Trivalent actinides Am(III), Cm(III), and Cf(III) were successfully separated for the first time using capillary electrophoresis in 2-hydroxyisobutyric acid/acetic acid. It was found that the ionic radius was primarily important for separation of trivalent actinides as well as lanthanides in this condition. The stability constants of the Am(III) complexes with 2-hydroxyisobutyrate were estimated using the correlations between the molar fraction ratio of lanthanides and their ionic radii.
Chemical studies on element 104, rutherfordium (Rf), at JAERI (Japan Atomic Energy Research Institute) are reviewed. The transactinide nuclide 261Rf has been produced in the reaction 248Cm(18O, 5n) at the JAERI tandem accelerator with the production cross section of about 13 nb. On-line anion-exchange experiments on Rf together with the lighter homologues, group-4 elements Zr and Hf, in acidic solutions have been conducted with a rapid ion-exchange separation apparatus. From the systematic study of the anion-exchange behavior of Rf, it has been found that the properties of Rf in HCl and HNO3 solutions are quite similar to those of Zr and Hf, definitely confirming that Rf is a member of the group-4 elements. However, we have observed an unexpected chemical behavior of Rf in HF solutions; the fluoride complex formation of Rf is significantly different from those of the homologues. Prospects of extending chemical studies on transactinide elements in the near future at JAERI are briefly considered.