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Noguchi, Hiroki; Sato, Hiroyuki; Nishihara, Tetsuo; Sakaba, Nariaki
Kagaku Kogaku, 88(5), p.211 - 214, 2024/05
High temperature gas-cooled reactor (HTGR), one of the next-generation innovative reactors, has an inherent safety and can generate very high-temperature heat which can be used for various heat application including hydrogen production. In Japan, Green Growth Strategy for Carbon Neutrality in 2050 and Basic Policy for the Realization of GX state the promotion of technology development necessary for mass and low-cost carbon-free hydrogen production and development and construction of next-generation innovative reactors including the HTGR for the decarbonization of industrial sectors. Based on these policies, JAEA has been conducted the world's first hydrogen production test using nuclear heat from an HTGR, in addition to verifying the excellent safety features of HTGR, and has also started to study the construction of an HTGR demonstration reactor in cooperation with the industrial community. This paper shows the current status of R&D of HTGR in Japan.
Ouchi, Kazuki
Hosha Kagaku, (49), p.3 - 7, 2024/03
I introduce the elucidation of the deposition following the oxidation state of uranium and the electrochemical behavior of uranium(IV) chloride in an ionic liquid-organic mixture, as a basic study of in-solution reactions. In addition, I introduce the development of separation methods for actinides using a microchemical chip and polyacrylamide gel electrophoresis, as an applied study for quantitative analytical methods for small amounts of samples.
Sato, Nobuaki*; Kirishima, Akira*; Sasaki, Takayuki*; Takano, Masahide; Kumagai, Yuta; Sato, Soichi; Tanaka, Kosuke
Current Location of Fuel Debris Chemistry, 178 Pages, 2023/11
Considerable efforts have been devoted to the decommissioning of the TEPCO's Fukushima Daiichi Nuclear Power Station (1F) and now the retrieval of fuel debris is being proceeded on a trial basis. It can be said that the succession of science and technology related to debris, that is, human resource development, is important and indispensable. For that reason, we thought that a specific textbook on decommissioning is necessary. Regarding the 1F fuel debris, we still do not know enough, and it would be difficult to describe the details. However, 12 years have passed since the accident, and we have come to understand the situation of 1F to a certain extent. At this stage, it is essential for future development to organize the current situation by combining examples of past severe accidents. Therefore, we presented in this book the current state of fuel debris chemistry research from the perspectives of solid chemistry, solution chemistry, analytical chemistry, radiochemistry, and radiation chemistry.
Morii, Shiori; Yomogida, Takumi; Asai, Shiho*; Ouchi, Kazuki; Oka, Toshitaka; Kitatsuji, Yoshihiro
Bunseki Kagaku, 72(10.11), p.441 - 448, 2023/10
Rapid analytical method for the determination of Zr-93 in radioactive wastes has been developed. Laser ablation (LA)-ICP-MS was applied to the analysis of Zr isotopes in simulated high-level radioactive waste (HLW). Sample preparation time was dramatically reduced by using a DGA resin as the adsorbent for Zr. Direct quantification of Zr isotopes in this resin sample was carried out by LA-ICP-MS. Laser settings were optimized to obtain a reliable isotope ratio of the sample by LA-ICP-MS. Quantification of Zr isotopes in the simulated HLW solution by isotope dilution mass spectrometry (IDMS) was examined. The amount of Zr-90 in the sample obtained by IDMS corresponded to a value calculated from the given concentration of Zr in the sample within uncertainty. Thus, this method can be applied for the quantification of Zr-93 in radioactive wastes.
Tachi, Yukio
Kagaku To Kyoiku, 71(10), p.420 - 423, 2023/10
no abstracts in English
Tomita, Ryohei; Tomita, Jumpei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
Hosha Kagaku, (48), p.1 - 15, 2023/09
Secondary Ion Mass Spectrometry (SIMS) is the method to detect secondary ions produced by the sputtering of primary ions. SIMS is one of effective method to measure isotopic composition of particles containing nuclear material in environmental sample for safeguards. We are a group member of the International Atomic Energy Agency (IAEA)'s network of analytical laboratories and have developed analytical techniques using SIMS and other mass spectrometers for nuclear safeguards. We will introduce the principle of SIMS and analytical techniques developed by our group to measure isotopic composition of uranium particles which having a particle diameter of micron order in environmental sample for safeguards.
Yamaguchi, Akiko
Hosha Kagaku, (48), p.56 - 59, 2023/09
The adsorption reaction on clay minerals is an important chemical reaction that controls the environmental behaviors of various ions at the Earth's surface, but the details are unknown due to the complexity of the reaction, such as the diversity of clay mineral compositions and the existence of multiple adsorption sites. In this study, we focused on the adsorption structure on clay minerals at the atomic level, and clarified it in detail by combining X-ray absorption fine structure (XAFS) methods and first-principles calculations. In particular, XAFS measurements of radium, which has the largest ionic radius among alkaline earth metals and has been difficult to measure at the atomic level, were successfully performed, and new knowledge was obtained by comparing the results with those of other elements.
Kumagai, Yuta
Hoshasen Kagaku (Internet), (115), p.43 - 49, 2023/04
Oxidation and dissolution of uranium oxide materials has been a subject of numerous studies as a basis of the geological disposal technology for spent nuclear fuel. The understandings obtained by these studies provide useful suggestions for research and development regarding the retrieval and storage of nuclear fuel debris generated by a nuclear severe accident. Here, these research backgrounds of oxidative dissolution of uranium oxides are briefly reviewed and some studies relating to radiation-induced reactions will be introduced.
Sr and 
Cs into wild animals after the Fukushima Daiichi Nuclear Power Plant accident using hard tissue as an indicatorKoarai, Kazuma
Hosha Kagaku, (47), p.24 - 27, 2023/03
Ca-based tissues, such as teeth and bones, are called hard tissues. Sr is incorporated into the tooth during calcification. Once incorporated, it remains until the tooth falls out. Therefore, Sr in teeth recorded Sr contamination by the 1F accident in the environment during the formation period. The article presents current research findings.
Tokunaga, Kohei
Hosha Kagaku, (47), p.20 - 23, 2023/03
no abstracts in English
Yamaguchi, Akiko
Hosha Kagaku, (47), p.41 - 42, 2023/03
Radium (Ra) is essential for various fields, such as environmental chemistry and nuclear medicine. However, even the hydration structure of Ra remains unclear due to the difficulty in the Ra treatment, caused by the fact that Ra has no stable isotopes and forms radon, noble gas. This study measured the extended X-ray absorption fine structure (EXAFS) of Ra to investigate its hydration structure and adsorption structures on clay minerals. The EXAFS results were consistent with our environmental analysis of core samples in a uranium mine.
Cs concentration and Cs/Cs isotopic ratio measurementShimada, Asako
Bunseki Kagaku, 71(12), p.625 - 633, 2022/12
Cesium-135 is one of the important nuclides to assess the safe disposal of High Level Waste (HLW). Therefore, the calculation code and library to evaluate the Cs concentration in HLW have been improved through comparisons with experimental results. On the other hand, even basic data of Cs, such as its half-life, have large uncertainty. Because the Cs/Cs isotopic ratio suggests its origin and introduction date, the ratios in environmental samples are measured to study global fallout from nuclear weapons testing and nuclear accidents. Such measurement methods was attracted attention, in particular, after the accident at the Fukushima Daiichi Nuclear Power Station. Measurement of the Cs/Cs isotopic ratio in environmental samples was challenging because the radiocesium has a very low concentration and it co-exists with huge amounts of Ba isotopes, which are isobaric interfering nuclides, are co-exist. Chemical separation methods were developed to eliminate interfering nuclides and improve the performance of the mass spectrometer to enable the measurement of the ratios. In this review, the features of the Cs/Cs isotopic ratio for each origin and recent developments in measurement techniques are summarized.
O-induced oxidative degradation of simulated fuel debrisKumagai, Yuta; Kusaka, Ryoji; Nakada, Masami; Watanabe, Masayuki; Akiyama, Daisuke*; Kirishima, Akira*; Sato, Nobuaki*; Sasaki, Takayuki*
Hoshasen Kagaku (Internet), (113), p.61 - 64, 2022/04
The severe accident at TEPCO's Fukushima Daiichi Nuclear Power Station resulted in generation of fuel debris. The fuel debris is in contact with water and the radiolysis of water can accelerate degradation of the debris. The analysis of particles sampled from inside or near the damaged reactors indicates the complicated compositions of the fuel debris. It is challenging to estimate the effect of water radiolysis on such a complicated material. Therefore, in this study, we investigated the potential degradation process by leaching experiments of simulated fuel debris in aqueous HO solution. The results show that the reaction of HO induced uranium dissolution from most of the samples and then formation of uranyl peroxides. In contrast, a sample that had U-Zr oxide solid solution as the major phase exhibited remarkable resistance to HO. These findings revealed that the degradation of the simulated debris reflects the reactivity and stability of the uranium phase in the matrices.
Yamaguchi, Akiko; Nagata, Kojiro*; Tanaka, Kazuya; Kobayashi, Keita; Kobayashi, Toru; Shimojo, Kojiro; Tanida, Hajime; Sekiguchi, Tetsuhiro; Kaneta, Yui; Matsuda, Shohei; et al.
Hosha Kagaku, (45), p.28 - 30, 2022/03
no abstracts in English
Sato, Nobuaki*; Kirishima, Akira*; Watanabe, Masayuki; Sasaki, Takayuki*; Uehara, Akihiro*; Takeda, Shino*; Kitatsuji, Yoshihiro; Otobe, Haruyoshi; Kobayashi, Taishi*
The Chemistry of Thorium, Plutonium and MA, 254 Pages, 2022/03
The chemistry of nuclear materials such as Thorium (Part 1) and Plutonium (Part 2) was described in relation from the fundamentals on solid chemistry and solution chemistry to the practicals on the experiment and evaluation method in detail. Minor actinides such as Neptunium, Americium, Curium and Protoactinium, was introduced the basics on the solid and solution chemistry.
Haraga, Tomoko; Saito, Shingo*
Bunseki Kagaku, 70(12), p.671 - 679, 2021/12
We developed highly sensitive capillary electrophoresis-laser-induced fluorescence detection methods for lanthanide (Ln) and actinide (An) ions with small sample volume and low emission of waste, by which the radiation risk can be minimized. Specifically, determination of Nd ion in spent nuclear fuel, effective separation between Am and Cm ion, and specific detection of UO
in real radioactive samples were achieved by molecular design of fluorescence probes composed of an aminocarboxylate chelating moiety, a fluorophore and a spacer, and unique separation mode based on dynamic ternary complexation. We found that there are appropriate combination of probe and ternary complexation for detection and separation of each Ln and An ions. For example, acyclic and macrocyclic hexadentate is suitable for Ln
, Am and Cm, and planer tetradentate with 
electron system is specific for UO, with ppt-sub ppt level detection.
I in the terrestrial environment after the Fukushima Dai-ichi Nuclear Power Plant accidentHonda, Maki
Chikyu Kagaku, 55(4), p.176 - 192, 2021/12
Iodine 129 (I) is a radionuclide that decays to Xe with a half-life of 15.7 million years. The analysis of I in the environment has played an important role not only in the fields of planetary science and earth science, but also in the nuclear field in recent years. Particularly, in the case of the Fukushima Dai-ichi Nuclear Power Plant accident in March, 2011, the scientists estimated the distribution and soil deposition of 
I over a wide area, and contributed to the assessment of internal exposure doses in the early stage of the accident. This is one of the most significant achievements in recent I-related studies. Future studies are expected to be conducted to elucidate the transport mechanism of I from land to river and sea, and to investigate the possible accumulation of I in aquatic organisms. The mobility of I in the soil studied by the author during the 10-years since the accident has been mainly reviewed in this manuscript.
Okumura, Masahiko
Chikyu Kagaku, 55(4), p.110 - 121, 2021/12
no abstracts in English
Tanaka, Kazuya; Yamasaki, Shinya*
Chikyu Kagaku, 55(4), p.93 - 95, 2021/12
Ten years have passed since the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. In this special issue, we compiled review papers on the environmental behavior of the FDNPP-derived radionuclides from various research fields. This special issue shows that various research fields contributed to better understandings on the environmental behavior of the FDNPP-derived radionuclides.
Miura, Hikaru*; Kuribara, Yuichi; Takahashi, Yoshio*
Chikyu Kagaku, 55(4), p.122 - 131, 2021/12
Radiocesium-bearing microparticles (CsMPs), glassy water-resistant particles with highly concentrated radiocesium, were emitted by the Fukushima Daiichi Nuclear Power Plant accident. Since first discovery of CsMPs, a number of studies have analyzed the particles isolated from environmental samples and revealed their physical and chemical properties, distribution, and migration. This paper is intended to provide an overview focusing on the environmental transport and impact of CsMPs. First, we begin by reviewing the relationship between deposition areas and atmospheric plumes of CsMPs found on land. Next, search and separation methods for CsMPs will be described. Then, secondary transport via rivers and effect of CsMPs on Kd values of Cs in rivers will be discussed. Finally, CsMPs found in the ocean and their difference from terrestrial ones will be summarized.
