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Journal Articles

Electrochemistry of actinide

Kitatsuji, Yoshihiro

Radioisotopes, 67(10), p.483 - 493, 2018/10

Electrochemical reactions and redox properties of actinides such as uranium and neptunium are outlined. The flow electrolysis enables rapid and high-efficient treatment. It was demonstrated to measure slow processes of actinide redox. Experimental results of electrolysis of actinide ions and the preparation method of oxidation state of the ions based on the fundamental data are described. Mediator reaction and catalysis observed in the process of electrolysis of actinide ions are also explained.

Journal Articles

Liquid-phase chemistry of rutherfordium (Rf), dubnium (Db) and seaborgium (Sg)

Nagame, Yuichiro

Radioisotopes, 67(10), p.507 - 526, 2018/10

Recent studies of the chemical separation and characterization experiments of the first three transactinide elements, rutherfordium (Rf), dubnium (Db) and seaborgium (Sg), conducted atom-at-a-time in liquid phases, are reviewed. A short description on experimental techniques based on partition methods, specifically automated rapid chemical separation systems, as well as on assessment of role of relativistic effects is also given. Perspectives for liquid phase chemistry experiments on heavier elements are briefly discussed.

Journal Articles

NMR study of actinide compounds; Case of actinide dioxides

Kambe, Shinsaku

Radioisotopes, 67(8), p.389 - 401, 2018/08

no abstracts in English

Journal Articles

Science of heavy and superheavy elements (nuclear physics); Experimental studies on shell structure of superheavy nuclei

Asai, Masato

Radioisotopes, 67(6), p.291 - 298, 2018/06

Stability and limit of existence essentially depend on nuclear shell structure. It is theoretically predicted that stable doubly-closed-shell spherical superheavy nuclei should exist around the region of the proton number 114 to 126 and the neutron number 172 to 184, although their locations and degree of stability have not been established because of large variety of theoretical predictions. On the other hand, recent advances on experimental techniques have made it possible to accumulate experimental data concerning the shell structure of superheavy nuclei, such as half-lives and nuclear masses. In addition, some pioneering experiments have been performed to directly establish the level structure of superheavy nuclei through spectroscopic methods. This paper introduces the current status of experimental studies on nuclear shell structure of superheavy nuclei.

Journal Articles

Knowledge discovery of suppressive effect of disease and increased anti-oxidative function by low-dose radiation using self-organizing map

Kanzaki, Norie; Kataoka, Takahiro*; Kobashi, Yusuke*; Yunoki, Yuto*; Ishida, Tsuyoshi*; Sakoda, Akihiro; Ishimori, Yuu; Yamaoka, Kiyonori*

Radioisotopes, 67(2), p.43 - 57, 2018/02

We previously reported that low-dose radiation induces the anti-oxidative function in many organ systems of mice. This results in the suppression of several kinds of oxidative stress-induced damage. This study was conducted with the objective of revealing the health effects of low-dose radiation obtained from our previous reports and searching for a new treatment based on low-dose radiation, such as radon therapy. We extracted the characteristics of the effects of low dose radiation suppressing diseases and enhancing the anti-oxidative function using fuzzy answer by self-organizing map (SOM) based on mutual knowledge. The relationship between the suppressive effect and increased antioxidative function was shown in our result, and the concentration dependence of the effect against pain was shown on the output map. Although the effect against other organs depending on concentration was unpredictable, our results indicate that low-dose radiation may also be suitable for treatment of liver disease and brain disease.

Journal Articles

Modern radiation chemistry (Applications), 13; Dose heterogeneity from a viewpoint of microdosimetry

Sato, Tatsuhiko

Radioisotopes, 66(11), p.507 - 512, 2017/11

Absorbed doses are inhomogeneously distributed in microscopic scales such as DNA and cell nucleus. In order to quantify the radiation effect due to this inhomogeneity, the probability density of the absorbed dose should be evaluated. This report reviews the concept of dose inhomogeneity from the viewpoint of microdosimetry, and introduces our established method for calculating the probability density of microscopic doses and its applications to radiation biology.

Journal Articles

Modern radiation chemistry (Applications), 18; Radiation chemistry at solid/water interfaces

Kumagai, Yuta

Radioisotopes, 66(11), p.537 - 541, 2017/11

Radiation effects on the mixtures of inorganic oxides and water have been investigated for understanding radiation chemistry in solid-liquid systems. A number of studies revealed that energy deposition on solid phase stimulates reactions at the interface. This energy/charge transfer has been demonstrated by experiments to affect early stage of the radiation-induced reaction. However, the interfacial reactions subsequent to the energy/charge transfer require further studies. Here, we will see gaps between the basic understanding on the early stage and radiation effects in solid-liquid systems connected to applications, taking zeolite/water and uranium oxide/water interfaces for examples. Understanding of the interfacial reactions subsequent to the energy/charge transfer would bridge the gaps and enable to predict the radiation effects in applications.

Journal Articles

Modern radiation chemistry (Applications), 24; Radiation chemistry and positron annihilation

Hirade, Tetsuya

Radioisotopes, 66(11), p.587 - 593, 2017/11

Positron, anti-particle of electron, annihilates with the lifetime of 100ps to several ns in condensed matter. The energy of the mass of both particles emits as two $$gamma$$-rays. The annihilation rate of energy of $$gamma$$-rays indicate information just before the annihilation. Positrons have some possibility of reaction with excess electrons to form Positronium (Ps). Ps formation occur within ~ps, therefore Ps formation can be a probe of very fast reactions. Moreover, long lived triplet Ps can have reaction with reactive species until the lifetime of ~ns. Here, methods of positron annihilation research for radiation chemistry and some researches done by positron annihilation methods are introduced.

Journal Articles

Modern radiation chemistry (Applications), 16; Computer simulation study of initial process of radiation biological effect

Watanabe, Ritsuko*; Kai, Takeshi; Hattori, Yuya*

Radioisotopes, 66(11), p.525 - 530, 2017/11

To understand the mechanisms of radiation biological effects, modeling and simulation studies are important. In particular, simulation approach is powerful tool to evaluate modeling of mechanisms and the relationship among experimental results in different spatial scale of biological systems such as DNA molecular and cell. This article summarizes our approach to evaluate radiation action on DNA and cells by combination of knowledge in radiation physics, chemistry and biology. It contains newly theoretical approach to estimate physico-chemical process of DNA damage induction in addition to typical method of DNA damage prediction. Outline of the mathematical model for dynamics of DNA damage and cellular response is also presented.

Journal Articles

Journal Articles

Bonding study on trivalent europium complexes by combining M$"o$ssbauer isomer shifts with density functional calculations

Kaneko, Masashi; Watanabe, Masayuki; Miyashita, Sunao*; Nakashima, Satoru*

Radioisotopes, 66(8), p.289 - 300, 2017/08

Scalar-relativistic density functional calculations applied to some trivalent europium complexes. Five Eu(III) complexes whose $$^{151}$$Eu M$"o$ssbauer isomer shifts vary from -1.8 to 0.5 mm/s are referred by previously reported results. Geometrical optimizations of their complexes reproduces the experimental coordination structures. Single-point calculations are applied to their optimized geometries at three density functionals, namely, BP86, B3LYP, and B2PLYP, to obtain their electron densities at Eu nucleus. A comparison of the linearity between the electron densities and the corresponding $$^{151}$$Eu M$"o$ssbauer isomer shifts reveals that B2PLYP functional shows the best linearity. Electron population and bond analyses indicate that d- and f-orbital electrons of Eu ion in the complexes are found to be correlated to the experimental $$^{151}$$Eu M$"o$ssbauer isomer shifts. This indicates that the d- and f-orbital electrons are involved in the covalent interaction of the coordination bond between the Eu ion and the ligands.

Journal Articles

Comparison of classification performances between Random forests and Support vector machine for $$gamma$$-ray spectral data of uranium-bearing waste drums

Hata, Haruhi; Ishimori, Yuu

Radioisotopes, 66(4), p.149 - 158, 2017/04

For the estimation of radioactive inventory, the radioactive waste drums should be classified based on their radioactive composition. We compared the classification performances between random forests and support vector machine, both of which are machine learning methods. The tested uranium in waste drums included natural uranium from uranium ore, reprocessed uranium from nuclear fuel, and natural uranium with rich radium from the impurities in yellow cake. A total of 75 data in 1037 $$gamma$$-ray spectral data of these drums were trained, and 962 data were applied in the classification models. It was found that the random forests were advantageous in the shift of the channels.

Journal Articles

Verification of the quantitative method of caesium radioactivity concentration of decontamination wastes

Yokoyama, Kaoru; Suzuki, Atsuo*; Ishimori, Yuu

Radioisotopes, 66(3), p.117 - 125, 2017/03

Decontamination wastes contaminated with radioactive cesium ($$^{134}$$Cs, $$^{137}$$Cs) are housed in the flexible container bags. Canberra manufactured flexible container concentration measurement car has been developed for the radioactivity measurement of decontamination waste. For reduction of background, the flexible container bags is mounted to the frame, it is measured from the lower side. In the flexible container bag, if there is uneven distribution of the source, it is estimated that quantification error increases. We proposed the method quantifying the shielding situation of $$gamma$$ rays. Then, it demonstrated that quantification accuracy of radioactivity can be improved.

Journal Articles

A Study on dynamics of non-crystalline materials and superionic conductors by chopper spectrometers in J-PARC

Nakamura, Mitsutaka

Radioisotopes, 66(2), p.93 - 99, 2017/02

Studying the dynamical properties of structurally isotropic materials such as glass, liquid, and polycrystalline powder samples, the inelastic neutron scattering measurement by chopper spectrometer in pulsed neutron source shows the whelming strength compared with that by triple axis spectrometer in research reactor. When a new material exhibiting the unusual physical properties is discovered, it might be difficult to grow the single crystal and only possible to obtain the powder form in the early stage of research. The strong neutron beam of J-PARC can provide opportunity promptly for the dynamical study of newly-discovered materials. The chopper spectrometers in J-PARC have the potential to create innovative research outcomes.

Journal Articles

Classification of radioactive waste drums using random forests for their $$gamma$$-ray spectra

Hata, Haruhi; Ishimori, Yuu

Radioisotopes, 66(1), p.1 - 10, 2017/01

The feasibility of Random Forests, one of machine learning methods was examined for the classification of radioactive waste drums. It was carried out using 954 $$gamma$$-ray spectra of drums which were already classified to natural or reprocessed uranium. After 300 spectra were selected at random to reassemble training datasets, the percentages of correct classification by Random Forests were evaluated with another 654 spectra. When the counts of spectra were reprocessed as the difference of their logarithm, Random Forests accurately classified 654 drums.

Journal Articles

Dynamics in condensed matter by 4SEASONS

Kajimoto, Ryoichi

Radioisotopes, 65(12), p.523 - 534, 2016/12

no abstracts in English

Journal Articles

Verification of the quantitative method to measure enrichment of uranium-235 in radioactive waste

Yokoyama, Kaoru; Sato, Katsunori*; Yamanaka, Takashi*; Ishimori, Yuu

Radioisotopes, 65(11), p.441 - 450, 2016/11

It is important for the processing manufacturers of the uranium fuels to determine the quantity of U-235 and the enrichment. This study shows that the U-235 content evaluated from measurement of 186 keV $$gamma$$ rays emitted from U-235 can be corrected by a shielding factor, Xgeometry which quantified uneven distribution of U-238. The Xgeometry is evaluated from the direct and the scattered $$gamma$$ rays from the 1001 keV emitted from the Pa-234m. The Xgeometry was originally introduced for U-238 measurements. Because U-235 coexists with U-238, the Xgeometry is also possible to apply to the U-235 measurements. The experimental study with simulated waste drums demonstrated that the quantification errors of the U-235 content and the enrichment are reduced considering the factor.

Journal Articles

Calculation of conversion factor for estimation of $$^{131}$$I concentrations in the air from pulse-height distribution observed by NaI(Tl) detector in monitoring posts

Yamada, Junya; Hashimoto, Makoto; Seya, Natsumi; Haba, Risa; Muto, Yasunobu; Shimizu, Takehiko; Takasaki, Koji; Yokoyama, Sumi*; Shimo, Michikuni*

Radioisotopes, 65(10), p.403 - 408, 2016/10

The purpose of this study is to develop a quick method for estimation of $$^{131}$$I concentrations in the air using data measured by monitoring posts. In this method, $$^{131}$$I concentrations were estimated by multiplying $$^{131}$$I count rates at the full-energy peak measured with a NaI(Tl) detector by a concentration conversion factor. The concentration conversion factor for monitoring posts in JAEA Oarai Center was calculated with an EGS5 Monte Carlo code. As a result, the concentration conversion factor for an infinite-air-source was 25.7 Bq/m$$^{3}$$/cps.

410 (Records 1-20 displayed on this page)