U-238 Mssbauer spectroscopic study of uranium oxysulfide

Masaki, Nobuyuki; Nakada, Masami; Akabori, Mitsuo; Arai, Yasuo; Nakamura, Akio; Sato, Nobuaki*

no journal, , 

The U-238 Mssbauer effect of uranium oxysulfide, UOS, has been investigated at various temperatures from 19 K to 80 K. The -ray source used for U-238 Mssbauer spectroscopy was Pu-242 dioxide with high isotope purity. By using a pure Ge detector, the 44.9 keV U-238 Mssbauer -ray is easily distinguished from the 59.5 keV -ray of the Am-241 isotope, which is the daughter nucleus of the isotopic impurity Pu-241. Quadrupole splitting of the U-238 nucleus in UOS is approximately -40 mm/s in the temperature range without account of magnetic splitting. According to neutron diffraction and magnetic susceptibility measurements, UOS is antiferromagnetic at low temperatures with a Neel temperature of T = 55 K. However, Mssbauer spectra below 55 K could be analyzed by using only quadrupole splitting without magnetic splitting. This result showed that the magnitude of quadrupole splitting was much larger than that of magnetic splitting of U nucleus in UOS.

Lateral distributions of Th-228 activity and Ra-228/Ra-226 activity ratio of surface water within the Sea of Japan, the East China Sea, and the Sea of Okhotsk

Yoshida, Keisuke*; Inoue, Mutsuo*; Minakawa, Masayuki*; Nakano, Yusuke*; Kofuji, Hisaki*; Otosaka, Shigeyoshi; Kiyomoto, Yoko*; Shiomoto, Akihiro*; Hamajima, Yasunori*; Yamamoto, Masayoshi*

no journal, , 

The authors have developed an analytical method for Th-228, Ra-226 and Ra-228 measurements in seawater using an ultra-low background -ray detector. In this study, the authors measured the three radionuclides in surface seawater obtained from 16 stations in the Japan Sea, East China Sea and Okhotsk Sea. Concentrations of Ra-228 and Th-228 in surface waters in the southern Japan Sea were lower than those in the northern regions. Considering that the Th-228/Ra-228 activity ratios were not different between the northern and southern regions of the Japan Sea, we could conclude that (1) input of terrestrial materials from the East China Sea has not affected the distribution of the radionuclides in the Japan Sea, and (2) the efficiency of scavenging was not different between the regions.

Cation-exchange behavior of Zr, Hf, and Th in HSO/HNO mixed solutions; Towards to study on sulfate complexation of Rf

Li, Z.; Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Sato, Tetsuya; Kikuchi, Takahiro; Sato, Nozomi; Nagame, Yuichiro

no journal, , 

Sequential ion-exchange separation and analysis of trace uranium, thorium, lead and lanthanides in environmental samples

Miyamoto, Yutaka; Yasuda, Kenichiro; Magara, Masaaki; Kimura, Takaumi

no journal, , 

Appropriate composition of eluents for sequential separation of trace U, Th, Pb and lanthanides with a single anion-exchange column was examined. The mixtures of acetic acid, hydrochloric acid and nitric acid made complete separation of the elements of interest. The elements in some reference materials were separated with this technique, and performance of this separation was evaluated.

Production of long-lived Fm and Es tracers using a Cf target and its application to nuclear spectroscopy

Asai, Masato; Tsukada, Kazuaki; Kasamatsu, Yoshitaka*; Sato, Tetsuya; Toyoshima, Atsushi; Nagame, Yuichiro

no journal, , 

We have successfully obtained a large amount of long-lived Fm and Es tracers which can be used in various kinds of heavy-actinide chemistry experiments. Fm and Es isotopes were produced with a Cf target and a C beam from the JAEA tandem accelerator. Reaction products recoiling out of the target were collected with a gas-jet transport technique. After 3-day irradiation, Fm and Es isotopes were chemically separated from the collected products. By measuring - and -energy spectra, we evaluated an amount of each Fm and Es isotope, and other radioactive impurities. We also performed - coincidence measurements for Fm using the same source.

The Use of synchrotron-based technique for actinide research

Ikeda, Atsushi

no journal, , 

Synchrotron-based analytical methods, such as X-ray absorption spectroscopy (XAS) or X-ray scattering (XS), have recently been recognized as a very powerful tool to investigate the solution/coordination chemistry of chemical substances. These methods have also been applied to the basic- and applied research concerning the actinide species in solution. In this talk, several recent topics related to the actinide speciation study using synchrotrons will be presented, as well as the prospect and future subjects of this research field.

The Distribution of I in the Japan Basin and Yamato Basin

Suzuki, Takashi; Minakawa, Masayuki*; Togawa, Orihiko

no journal, , 

no abstracts in English

Rapid reductive preparation of Np(IV) based on the electrocatalytic reaction

Kitatsuji, Yoshihiro; Kimura, Takaumi; Kihara, Sorin*

no journal, , 

The behaviors of reduction of NpO to Np or Np by controlled potential electrolysis were studied, and a unique time course of electrolysis current was observed. It was concluded that NpO was reduced by two reduction processes at a platinum electrode: the chemical reaction with Np and the electrocatalytic reduction by adsorbed hydrogen atom on platinum electrode surface. NpO is reduced to Np more selectively and with smaller overpotential through electrocatalytic reduction process, though long electrolysis time are required to reduce NpO completely. To improve the electrolysis efficiency of the preparation of Np from NpO, the platinized platinum electrode was applied to bulk electrolysis. The rapid preparation of Np comparable to that of reversible redox reaction such as NpO/ NpO with small overpotential was achieved successfully.

Reduction of element 101, mendelevium, with flow electrolytic column chromatography

Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Sato, Tetsuya; Li, Z.; Sato, Nozomi; Kikuchi, Takahiro; Kitatsuji, Yoshihiro; Nagame, Yuichiro; Oe, Kazuhiro*; et al.

no journal, , 

Reduction of element 101, mendelevium (Md), was studied with flow electrolytic chromatography. Mendelevium-255 with a half-life of 27 min was produced in the Cm(B, 4n) reaction at the JAEA tandem accelerator. Reaction products transported by a KCl/He gas-jet method to the chemistry laboratory were collected on a chemistry apparatus. After removing KCl with HDEHP chromatography, elution behavior of Md in 0.1 M HCl was investigated with a flow electrolytic column apparatus at the applied potentials between 0 -0.9 V vs. a Ag/AgCl reference electrode. Elution behavior of Md was the same as that of Bk at 0 V, showing that the stable Md was not reduced to the divalent state. At -0.9 V, elution of Md was quite similar to that of Sr, demonstrating that Md was successfully reduced to Md.

Production of radioisotopes for nuclear medicine using fast neutron reactions

Hatsukawa, Yuichi; Hashimoto, Masashi; Nagai, Yasuki*; Kin, Tadahiro; Segawa, Mariko; Harada, Hideo; Konno, Chikara; Ochiai, Kentaro; Takakura, Kosuke; Iwamoto, Nobuyuki; et al.

no journal, , 

Tc is the most important radioisotope used as nuclear medicine which is mostly produced by using only five nuclear reactors. Recently, two of the present authors proposed a new route to produce Mo by the Mo(n,2n)Mo reaction, which has the following characteristic features. (1) First, the reaction cross section is large. Second, the cross sections of the (n,), (n,np), and (n,p) reactions are less than a few mb at En = 14 MeV. Third, a large amount of Mo target materials can be used, compared to that for proton beam irradiation on Mo. In the present work we have measured all -rays emitted from activities produced by bombarding a natural Mo target with neutrons from the D(H,n)He reaction at FNS at Japan Atomic Energy Agency (JAEA) to study characteristic features mentioned above more in detail. The experimental results at FNS will be discussed in the conference.