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2024.10.18
Ms. Shiori Morii of the Research Group for Nuclear Chemistry won the Young Researcher Presentation Award of the 68th Symposium on Radiochemistry of The Japan Society of Nuclear and Radiochemical Sciences on September 25, 2024. The presentation title was “Analysis of redox and structural properties of Fe in clay minerals by Fe-57 Mössbauer spectroscopy” .
To understand the influence of redox properties of structural Fe in clay minerals on removal and immobilization of radionuclides in geological disposal environment, we investigated redox and structural properties of Fe in clay minerals at reducing conditions. Clay mineral sample was reduced by controlled-potential electrolysis at -0.5 V vs the standard hydrogen electrode. Redox state and structural properties of Fe in this prepared clay mineral sample was investigated by Fe-57 Mössbauer spectroscopy. From the Mössbauer spectra, we found that structural Fe(III) in octahedral sheets was reduced to Fe(II). This fundamental information about the Fe in clay minerals will contribute to technical reliabilities of geological disposal.
2024.10.17
Dr. Katsuhiro Ueno of the Research Group for Nuclear Chemistry received the Young Presentation Award of the 68th Symposium on Radiochemistry of The Japan Society of Nuclear and Radiochemical Sciences, on September 25, 2024, for his excellent poster presentation entitled “Influence of chloride ion concentration on redox reaction of uranium (IV) chloride in a non-aqueous solvent”.
The redox-reaction properties of metal ions in electrolyte solutions are important for applications in electrochemical devices such as redox capacitors and chemical batteries. In this study, he focused on the properties of uranium(IV) chloride in non-aqueous solvents and evaluated the effect of adding chloride ions using electrochemical and spectroscopic measurements. As a result, it was found that a hexacoordinated uranium(IV) chloride complex is stabilized by the addition of an excess amount of chloride ions relative to uranium (IV) chloride. Furthermore, the redox-reaction rate of uranium (IV) chloride improved with an increase in chloride ion concentration in the solution. These findings are expected to contribute to realizing new electrochemical devices.
2024.10.17
Mr. Yoshimasa Kitamura of the Research Group for Nuclear Chemistry, Nuclear Science and Engineering Research Center, received the “Best Presentation Award” for the poster presentation at the 67th Annual Meeting of Japanese Society of Radiation Chemistry Symposium held in Hiroshima University.
Radiation is used in a wide range of fields, including industry and medicine, for irradiation, modification, sterilization of materials, and so on. In such radiation fields, dose control is indispensable to evaluate the radiation dose. Irradiation facilities use simple chemical dosimeters for dose control; however, they are mainly designed to evaluate high doses above 10 Gy. Hence it is technically difficult to accurately measure low doses in the order of a few Gy or mGy. We are developing a new solid-state dosimeter that enables accurate dosimetry in the such low-dose range. In this work, we focused on the long-lived carbonate radicals produced in tooth enamel by irradiation. The amount of carbonate radicals produced by irradiation can be used as an indicator to estimate the radiation dose from the time the tooth was formed to the present. We measured the carbonate radicals produced in hydroxyapatite, the main component of tooth enamel, by 60Co gamma rays irradiation with an electron spin resonance spectrometer, and demonstrated that hydroxyapatite sample can detect a wide dose range from 100 mGy to several kGy. This new dosimeter is expected to be applied to dose control in a wide range of fields such as the reproduction of the effects of low-dose exposure in the Fukushima Daiichi Nuclear Power Plant accident, as well as in industrial and medical fields.
2024.05.21
Drs. Osamu Iwamoto and Nobuyuki Iwamoto of Nuclear Data Center and Dr. Kenichi Tada of Research Group for Reactor Physics and Thermal Hydraulics in Nuclear Engineering Research Center, received 56th Atomic Energy Society of Japan Special Award and Technology Award for the development of the evaluated nuclear data library JENDL-5, which were conducted together with the colleagues of Kyoto University, Tokyo Institute of Technology, International Atomic Energy Agency, Hokkaido University, and National Institutes for Quantum Science and Technology.
The nuclear data library is a database containing data of nuclear reactions between radiation and atomic nuclei. It is used for various radiation simulation calculations including nuclear reactors. JENDL-5 nearly doubles the number of nuclides in neutron reaction data from the previous version, JENDL-4.0, using experimental data measured at J-PARC and the latest nuclear reaction theoretical models. These data cover naturally existing nuclides and most of radionuclides with a half-life longer than 1 day, which can be used for materials containing various nuclides. In addition, consistency and convenience have been improved by integrating activation cross sections, high-energy nuclear data, and nuclear reaction data for protons, deuterons, alpha particles, and photons, which had been published separately for each application. Furthermore, we have conducted a wide range of benchmark tests and made improvements to the nuclear properties of nuclear reactors, resulting in improvement of prediction performance from JENDL-4.0.
【JENDL-5 web page】https://wwwndc.jaea.go.jp/jendl/j5/j5.html
【JENDL-5 paper】https://doi.org/10.1080/00223131.2022.2141903
2024.05.17
Afiqa Mohamad from the Research Group for High Temperature Science on Fuel Materials received an “56th Encouragement Award” from the Atomic Energy of Society Japan at Kindai University, Osaka on 27th March 2024. This award was given to a young researcher for her contribution to the nuclear field. Her work on the “Chemical interaction between Sr vapor species and nuclear reactor core structure” published in Journal of Nuclear Science and Technology.
Strontium (Sr), one of the main radiation sources was assume to form non-volatile Sr compounds. It was estimated that Sr was remained in the solidified fuel left within the reactor (fuel debris). Therefore, leaching of Sr in the fuel debris into water was considered to be the main release pathway at the Fukushima Daiichi Nuclear Power Plant (1F), but the adhesion of Sr to debris samples and soil could not be explained simply by release through the aqueous phase. The present results show that Sr can be released from the fuel under the seawater injection conditions of the 1F accident, and that it chemisorbed to the reactor core structural materials through gas-solid state reactions, and identify the chemical reactions involved. This is expected to be useful as basic knowledge contributing to the understanding the behavior, distribution and properties of Sr in the reactor core, and to the evaluation of public exposure and safety measures in the decommissioning of 1F.
【Awarded paper】
https://doi.org/10.1080/00223131.2022.2092227
2024.05.10
Dr. Masao Komeda and Dr. Yosuke Toh of the Research Group for Nuclear Sensing at Nuclear Science and Engineering Center, along with their collaborators from the National Research Institute of Police Science and Kyoto University, received the prize of the "56th Atomic Energy Society of Japan Article Award" for the paper entitled “Development of a water Cherenkov neutron detector for the active rotation method and demonstration of nuclear material detection”.
At airports and other transportation-related facilities, it is necessary to detect concealed nuclear materials in luggage. There are various types of nuclear material detection devices, and while active devices that examine objects by irradiating them with radiation have the highest performance, the devices themselves are expensive and large in size. To develop a low-cost and transportable active device, we developed a new active device known as the rotating irradiation device. This device generates pseudo-pulses (neutron intensity) by rotating a neutron source such as Cf-252, irradiates the object, and detects nuclear materials with high sensitivity by measuring changes in neutron flux. This method was demonstrated through proof-of-principle experiments. However, in the proof-of-principle experiments, many expensive He-3 detectors were used as neutron detectors, and it was necessary to develop new neutron detectors to reduce the cost. In this study, we developed a water Cherenkov neutron detector (WCND) that costs less than one-tenth the price of He-3 detectors and has a neutron detection efficiency more than four times higher than that of He-3 detectors by using inexpensive water. Using the developed WCND, we conducted a nuclear material detection experiment with the rotating irradiation device and succeeded in detecting a small amount of nuclear material (56.7 g of U-235) in a short time (15 minutes).
【Awarded paper】
https://doi.org/10.1080/00223131.2022.2143449
2024.05.07
Dr. Tatsuhiko Sato, Dr. Yosuke Iwamoto, Dr. Shintaro Hashimoto, Dr. Takuya Furuta, and Dr. Tatsuhiko Ogawa were awarded the Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology (MEXT) in the field of science and technology for their “Development of a general-purpose radiation transport simulation code PHITS”. PHITS is currently used by approximately 10,000 researchers and engineers in 76 countries, contributing to the radiation-related research and industry all over the world. Please visit PHITS website (https://phits.jaea.go.jp) in more detail about the code.
2024.05.07
Drs. Yosuke Iwamoto et al. of Research Group for Radiation Transport Analysis received the Prize of “JNST Most Cited Article Award 2023” for the paper entitled, “Benchmark study of the recent version of the PHITS code” (J. Nucl. Sci. Technol., Vol. 54, 617-635 (2017)) on the 27th of March 2024.
A general-purpose radiation transport simulation code PHITS is a Monte Carlo simulation code developed under collaboration between JAEA, Research Organization for Information Science and Technology (RIST), High Energy Accelerator Research Organization (KEK) and other institutes. The code can transport nearly all types of radiation in any material using the implemented nuclear reaction models and the nuclear data libraries. Then, it can be applied to various fields such as design of radiation facilities, medical physics calculations, radiation protection studies, space radiation research, and other studies involving radiation transport simulations.
To validate the accuracy of the PHITS code for various applications, we carried out comprehensive benchmarks including particle production cross sections in the nuclear reactions, neutron transport calculations, as well as photon and electron scattering reactions. Agreements were found to be sufficiently satisfactory for most experimental data. However, some discrepancies were also observed between the simulations and the experimental data; particularly in particle production with incident particle energies below 100 MeV, and in neutron production from lithium targets bombarded by protons. This study has provided us important information that can guide further improvements for PHITS.
All of the benchmark results are available online for the public, and have been widely used by PHITS users all over the world as a reference of PHITS reliability in their applications.
To Download: https://www.tandfonline.com/doi/full/10.1080/00223131.2017.1297742
2024.05.07
Dr. Hiroaki Terada, Dr. Katsunori Tsuduki, and Dr. Masanao Kadowaki of Research Group for Environmental Science and Dr. Haruyasu Nagai of Nuclear Science and Engineering Center received the prize of “56th Atomic Energy Society of Japan Award: Distinguished Technical Award” for Atmospheric-dispersion database system WSPEEDI-DB on March 27, 2024.
In response to the Fukushima Daiichi Nuclear Power Plant accident, JAEA has been working on the estimation of the source term and clarification of the atmospheric dispersion processes of the radioactive materials discharged into the atmosphere due to the accident using the Worldwide version of System for Prediction of Environmental Emergency Dose Information version 2 (WSPEEDI-II). However, it was difficult to compare calculation results for various conditions because the detailed and complex WSPEEDI-II calculation model required considerable calculation time. To address this issue, we have developed a new atmospheric dispersion database system (WSPEEDI-DB) by making calculations quicker and renovating the interface for easy implementation of calculations and analysis.
The newly developed calculation method enables the automatic execution of dispersion calculations for a specific release point and the creation of a database of calculation outputs (dispersion-calculation DB) in advance, making it possible to immediately obtain prediction results for specified release conditions. In addition, we have extended the functions based on this calculation method: a method for estimating source term that is difficult to obtain in an emergency by statistical analysis comparing the dispersion-calculation DB and various environmental monitoring data, and a method for evaluating the uncertainty of future prediction results that is difficult with previous methods by applicating machine learning using the past long-term dispersion-calculation DB as training data.
The previous applications of this system are as follows. We applied it to the assessment of the monitoring posts deployment around the Shimane nuclear power station and demonstrated that this system can contribute to improving the effectiveness of disaster prevention planning. For the Fukushima Daiichi nuclear power station accident, we optimized the source term using various environmental measurements and reconstructed the spatiotemporal distribution of radionuclides in the environment, thereby contributing to the refinement of the dose assessment by the Ministry of the Environment, Japan and United Nation’s Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). In addition, as a response to overseas events, a dedicated automatic calculation system for underground nuclear tests by North Korea is in operation as a system of the Nuclear Regulation Agency.
Please see the website for more details about WSPEEDI-DB.
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