[en] Airborne radionuclides from the accident of Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in 2011 were measured at the RIKEN Wako Institute, Japan, about 220 km to the southwest of FDNPP, from March 15, 2011 to March 16, 2012. Radioactivity concentrations of "1"4"0Ba, "1"3"7Cs, "1"3"6"gCs, "1"3"4"gCs, "1"3"3"gI, "1"3"2Te, "1"3"1I, "1"2"9"mTe, "1"1"0"mAg, "9"9Mo, and "9"5"gNb (m: metastable state; g: ground state) were determined by γ-ray spectrometry with a germanium detector. The time variations of the radioactivity concentrations and their ratios in Wako are discussed by referring to those of the ambient effective dose rate as well as the amount of rainfall. The pronounced peaks of the radioactivity concentrations were observed on March 15, 20-21, and 29-31, 2011. The highest concentrations for typical radionuclides in unit Bq m"-"3 were 8.8 ± 0.2 for "1"3"7Cs, 1.2 ± 0.2 for "1"3"6"gCs, 8.5 ± 0.2 for "1"3"4"gCs, 4.7 ± 0.3 for "1"3"3"gI, 58 ± 2 for "1"3"2Te, 8.0 ± 1.2 for "1"2"9"mTe, and 35 ± 1 for "1"3"1I in the sample collected in the period of March 15, 2011, 11:15-11:45 JST (Japan Standard Time). The "1"3"4"gCs/"1"3"7Cs radioactivity ratio was determined to be 1.0 ± 0.1 for March 11, 2011, and this value was consistent with other observations related to the FDNPP accident. The environmental radioactive contamination in Wako occurred mainly on March 21, 2011, due to the first rainfall after the accident. (author)

[en] Extraction behavior of carrier-free Nb and Ta with tributyl phosphate (TBP) from HF solutions was studied by a batch method. Tantalum is extracted well to an organic phase, while Nb is left in an aqueous phase at 0.053-1.0 M HF concentrations. The similar extraction trends of Nb and Ta are shown in the solid phase extraction using a TBP resin. The extraction equilibria in the solid phase extraction are attained within ∼10 s. (author)

[en] We studied solid-liquid extraction behavior of carrier-free Mo and W radiotracers onto an Aliquat 336-loaded resin from HCl solutions toward extraction chromatography experiments of element 106, seaborgium (Sg). Distribution coefficients (K_d) of Mo and W on the resin were determined as a function of HCl concentration by a batch method. On-line extraction chromatography of Mo and W was also carried out in 2-8 M HCl solutions with an automated rapid chemistry apparatus. The order of extraction probability from 2 to 8 M HCl was Mo > W, which reflected the order of the K_d values in the batch experiment. (author)

[en] We are aiming to investigate complex formation properties of Sg with fluoride and chloride ions by extraction chromatography from HF and HCl solutions. We have selected Aliquat 336 as an extractant for anionic species in aqueous solution. In this study, solid-liquid extraction behaviors of carrier-free radiotracers Mo and W on Aliquat 336-loaded resin from 1–10 M HF and 0.1–10 M HCl solutions were investigated. (author)

[en] 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. (author)

[en] The extraction and reduction behavior of Mo and W, lighter homologs of Sg, was studied in continuous on-line experiments at the JAEA tandem accelerator to develop a new chemistry assembly consisting of a membrane degasser (MDG), a flow electrolytic column (FEC), and the continuous liquid-liquid extraction apparatus (SISAK). Extraction yields of Mo and W from 0.1 M HCl/0.9 M LiCl into 4-isopropyltropolone (hinokitiol, HT) in toluene were investigated. In the reduction experiment, Mo(VI) was successfully reduced to a lower oxidation state while W(VI) showed no reduction under the given conditions. (author)

[en] Production cross sections of Nb and Ta isotopes in the proton-induced reactions on ^natZr and ^natHf, respectively, were measured up to 14 MeV using a stacked-foil technique. The observed nuclides in the ^natZr(p,x) reactions were ^{90g,91m,92m,95m,95g,96}Nb, ⁹⁵Zr, and ^87g,88Y. In the ^natHf(p,x) reactions, ^{175,176,177,178,179}Ta and ¹⁷⁵Hf were observed. The obtained cross sections for each nuclide were compared with the previously reported data and with the theoretical cross sections calculated by the TALYS-1.4 code. Thick-target yields of the observed nuclides were deduced from the measured production cross sections. - Highlights: • Production cross sections of the ^natZr(p,x) and ^natHf(p,x) reactions were measured up to 14 MeV. • Experimental data were compared with the calculated values by the TALYS-1.4 code. • Thick-target yields of the individual isotopes were derived from the measured cross sections

[en] A new technique for continuous dissolution of nuclear reaction products transported by a gas-jet system was developed for superheavy element (SHE) chemistry. In this technique, a hydrophobic membrane is utilized to separate an aqueous phase from the gas phase. With this technique, the dissolution efficiencies of short-lived radionuclides of ^91m,93mMo and ¹⁷⁶W were measured. Yields of more than 80 % were observed for short-lived radionuclides at aqueous-phase flow rates of 0.1-0.4 mL/s. The gas flow-rate had no influence on the dissolution efficiency within the studied flow range of 1.0-2.0 L/min. These results show that this technique is applicable for on-line chemical studies of SHEs in the liquid phase. (author)

[en] We developed a production technology for radioisotopes of Ta and Nb for chemical studies of element 105, Db, using the RIKEN gas-filled recoil ion separator GARIS. Isotopes of ¹⁷⁰Ta and ⁸⁸Nb produced via the ^natGd(¹⁹F, xn)¹⁷⁰Ta and ^natGe(¹⁹F, xn)⁸⁸Nb reactions, respectively, were successfully extracted by the gas-jet method to a chemistry laboratory after physical separation by GARIS. (author)

[en] Solvent extraction of ^93mMo and ¹⁷⁶W using 4-isopropyltropolone (Hinokitiol, HT) was investigated. Extraction mechanism of Mo and W with HT was examined by slope analysis. The slopse of the distribution ratio of Mo and W vs. [HT] in logarihmic scale are 1.88 and 1.54, respectively. (author)