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Journal Articles

Discrimination of the current level of activity of groundwater flow in deep underground by using stable water isotopes

Mochizuki, Akihito; Ishii, Eiichi

Isotope News, (784), p.23 - 27, 2022/12

no abstracts in English

Journal Articles

Development of a new model simulating contaminations of forest resources with radiocesium in Fukushima

Ota, Masakazu; Koarashi, Jun

Isotope News, (784), p.28 - 31, 2022/12

In forests affected by the Fukushima Daiichi Nuclear Power Plant accident, trees became contaminated with $$^{137}$$Cs. However, $$^{137}$$Cs transfer processes determining the tree contamination (particularly for stem wood, a prominent commercial resource) remain insufficiently understood. We propose a model (SOLVEG-R) for simulating dynamic behavior of $$^{137}$$Cs in a forest tree-litter-soil system and applied it to contaminated forests of cedar plantation and natural oak stand in Fukushima to elucidate relative impact of distinct $$^{137}$$Cs transfer processes determining the tree contamination. The transfer of $$^{137}$$Cs to the trees occurred mostly ($$>$$99%) through surface uptake of $$^{137}$$Cs trapped by needles and bark during the fallout. Root uptake of soil $$^{137}$$Cs was several orders of magnitude lower than the surface uptake over a 50-year period following the accident. As a result, internal contamination of the trees proceeded through an enduring recycling (translocation) of $$^{137}$$Cs absorbed on the tree surface. A significant surface uptake of $$^{137}$$Cs through bark was suggested, contributing to 100% (leafless oak tree) and 30% (foliated cedar tree; the remaining uptake occurred at needles) of the total uptake by the trees. It was suggested that the activity concentration of $$^{137}$$Cs in stem wood of the trees at these sites are currently (as of 2021) decreasing by 3% per year, mainly through radioactive decay of $$^{137}$$Cs and partly through dilution effect from tree growth.

Journal Articles

New feature of PHITS dedicated to calculate the atomic-size transport of radiation

Ogawa, Tatsuhiko; Hirata, Yuho; Matsuya, Yusuke; Kai, Takeshi

Isotope News, (784), p.13 - 16, 2022/12

Track-structure calculation, a method to simulate every secondary electron production reaction explicitly, has been extensively used as an important techniques in various fields such as radiation biology, material irradiation effect, and radiation detection. However, it requires the dielectric function of the target materials, which is not well known except for liquid water. Therefore we developed a model to perform track-structure calculation based on a systematic formula of secondary electron production cross section and that of stopping power. The model can therefore perform track-structure calculation regardless of the availability of dielectric function measurement data. Stopping range, and energy deposition radial distribution calculated by this model agreed well with the earlier experimental data and calculation by precedent codes. The lineal energy in tissue-equivalent gas calculated by this model agreed with measurement data taken from literature, showing distinct difference from that in liquid water. This model was implemented to PHITS Ver3.25, the general-purpose radiation transport simulation code of JAEA, being distributed to users as the first track-structure calculation model applicable to arbitrary materials available in general-purpose transport code.

Journal Articles

Career paths for young researchers

Oka, Toshitaka

Isotope News, (784), p.43 - 44, 2022/12

We participated in Young Scientists Project Career Paths for Researchers held at the 59th Isotope and Radiation Research Presentation Meeting, where we heard from four lecturers and discussed how to encourage students to enter doctoral programs.

Journal Articles

Structure and properties of amorphous magnesium carbonate, a key material for geological storage of carbon dioxide

Kyono, Atsushi*; Yamamoto, Genichiro*; Yoneda, Yasuhiro; Okada, Satoru*

Isotope News, (783), p.23 - 27, 2022/10

Mineral traps are attracting attention as an underground storage method for carbon dioxide. Carbon dioxide laden groundwater reacts with basalt to form magnesite. The formed magnesium carbonate phase varies in many ways, but we tried to clarify the structure because all of them pass through amorphous magnesium carbonate. Pair distribution function using high-energy X-ray diffraction revealed that amorphous magnesium carbonate has a structure similar to that of hydromagnesite. It can be said that it is a safe sequestration method as a carbon dioxide storage technology.

Journal Articles

Eutectic melting of metals

Sumita, Takehiro; Ikeda, Atsushi

Isotope News, (783), p.28 - 32, 2022/10

no abstracts in English

Journal Articles

Resumption of radioisotope production in the Research Reactor JRR-3

Endo, Akira

Isotope News, (781), P. 3, 2022/06

The research reactor JRR-3 at the Nuclear Science Research Institute of Japan Atomic Energy Agency resumed its operation in February 2021 for the first time in 10 years. After commissioning, neutron beam experimental apparatus and irradiation facilities were used from July to November, and the operation in 2021 was completed as planned. During this period, Ir-192 and Au-198 were produced and supplied for therapeutic use, and test irradiation for the production of Mo-99 was performed. This is resumption of radioisotope production using nuclear reactors in Japan, which had stopped after the Great East Japan Earthquake. This article introduces future efforts of radioisotope production for medical applications in JRR-3.

Journal Articles

3D visualization of radioactive contamination using an integrated Radiation Imaging System (iRIS)

Sato, Yuki

Isotope News, (781), p.19 - 23, 2022/06

no abstracts in English

Journal Articles

Development of proton beam control technology for transmutation characteristic test

Takei, Hayanori

Isotope News, (779), p.11 - 15, 2022/02

The Japan Atomic Energy Agency (JAEA) has designed a Transmutation Physics Experimental Facility (TEF-P) as an experimental facility in the Japan Proton Accelerator Research Complex (J-PARC). The TEF-P is a critical assembly driven by a low-power proton beam, a maximum of 10 W, which is extracted from a high-power beam source, such as 250 kW of 400 MeV proton beam of the J-PARC Linac. To extract such a low-power proton beam from the high-power proton beam, we developed a laser charge exchange (LCE) device and employed its technique, which is one of the non-contact beam extraction techniques. For the proof of performance of the LCE device to the TEF-P, a low-power proton beam was extracted using a negative-hydrogen Linac having an energy of 3 MeV, and a bright laser. This paper summarizes the experimental results.

Journal Articles

Outline and key changes of ICRP Publication 130 "Occupational Intakes of Radionuclides (OIR) Part 1"

Takahashi, Masa; Yoshizawa, Michio

Isotope News, (778), p.30 - 33, 2021/12

no abstracts in English

Journal Articles

Analysis of radiation measurement data using AI

Sasaki, Miyuki

Isotope News, (778), p.2 - 5, 2021/12

no abstracts in English

Journal Articles

Reassessment of organ doses received by A-bomb survivors by precisely reproducing body dimensions of the Japanese in 1945

Sato, Tatsuhiko

Isotope News, (776), p.26 - 28, 2021/08

A Japan-U.S. joint project team was formed, comprising Nuclear Science and Engineering Center of JAEA, RERF, the University of Florida, and the U.S. National Cancer Institute. Members of this project team developed a new set of models of the human body (called phantoms) for adults, children, and pregnant women by precisely reproducing the standard body dimensions of Japanese people in 1945, modeled in detail with the latest CT images and other information. The project team also developed a method for more accurately estimating the organ doses of A-bomb survivors with these phantoms by utilizing the latest computational techniques such as PHITS, which were originated mainly by JAEA. Based on idealized conditions in hypothetical survivors, our initial comparisons of doses using the new phantoms and methods with doses derived from the current dosimetry system found that doses were generally consistent, although for some organs dose estimates could change by approximately $$pm$$15% at the maximum.

Journal Articles

Journal Articles

Development of microstructural analysis and evaluation techniques of steel materials using RIKEN compact accelerator-driven neutron source (RANS)

Xu, P. G.; Takamura, Masato*; Iwamoto, Chihiro*; Hakoyama, Tomoyuki*; Otake, Yoshie*; Suzuki, Hiroshi

Isotope News, (774), p.7 - 10, 2021/04

no abstracts in English

Journal Articles

Journal Articles

$$^{90}$$Sr contamination monitor of drainage water using a fiber type detector

Sanada, Yukihisa

Isotope News, (772), p.21 - 25, 2020/12

no abstracts in English

Journal Articles

Relation between resistance random access memory effect and electronic structure in amorphous alumina

Kubota, Masato

Isotope News, (771), p.40 - 42, 2020/10

no abstracts in English

Journal Articles

When was the maximum observation of nuclear weapon fallout?

Tsujimura, Norio

Isotope News, (768), p.38 - 39, 2020/04

no abstracts in English

Journal Articles

Temporal change in concentration of radiocesium in Fukushima river water

Nakanishi, Takahiro

Isotope News, (765), p.22 - 25, 2019/10

Temporal change in concentration of radiocesium in Fukushima river water are outlined. Radiocesium concentration in river water keeps decreasing after several years, however, the declining trend for the dissolved radiocesium concentration is gradually decreasing with time.

179 (Records 1-20 displayed on this page)