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Miyamoto, Yutaka; Suzuki, Daisuke; Tomita, Ryohei; Tomita, Jumpei; Yasuda, Kenichiro
Isotope News, (786), p.22 - 25, 2023/04
no abstracts in English
Sato, Ikken; Yoshikawa, Shinji; Yamashita, Takuya; Cibula, M.*; Mizokami, Shinya*
Nuclear Engineering and Design, 404, p.112205_1 - 112205_21, 2023/04
Times Cited Count:2 Percentile:84.55(Nuclear Science & Technology)Based on updated knowledge from plant-internal investigations, experiments and model simulations until now, the in-vessel phase of Fukushima-Daiichi Nuclear Power Station Unit 2 was analyzed using the MAAP code. In Unit 2, it is considered that the core material enthalpy was relatively low when it relocated to the lower plenum of the pressure vessel, then, cooled by the coolant and solidified there. Although the MAAP code tended to underestimate the degree of core-material oxidation during the relocation, this probable underestimation was compensated for by an existing study that was considered more reliable, so that more realistic debris conditions in the lower plenum could be obtained. Basic validity of the former prediction of the Unit 2 accident progression behavior was confirmed and detailed boundary condition for the later phase was provided. This boundary condition should be utilized for future studies addressing debris reheating process leading to lower head failure and debris relocation toward the pedestal.
Tateishi, Ryo*; Shimada, Koji; Shimizu, Mayuko; Ueki, Tadamasa*; Niwa, Masakazu; Sueoka, Shigeru; Ishimaru, Tsuneari
Oyo Chishitsu, 62(2), p.104 - 112, 2021/06
We attempted to discriminate between active and non-active faults by linear discriminant analysis using the chemical composition data of fault gouges in Japan, and then examined the elements that represent the difference between them and better discriminants. As a result, the multiple discriminants obtained could discriminate between them with high probability. In addition, the generalization performance of these discriminants is discussed, and the discriminants that can be expected to have high discriminant performance for unknown samples are presented. Also, from the combination of elements common to these discriminants, we narrowed down the number of elements that represent the difference between active and non-active faults to 6, and showed that the combination of TiO and Sr contributing the most to the discrimination. The method applied in this study is an innovative one that can discriminate the activity by chemical analysis of fault rocks that are universally present in the bedrock.
Miwa, Kazuji; Terasaka, Yuta; Ochi, Kotaro; Futemma, Akira; Sasaki, Miyuki; Hirouchi, Jun
Nihon Genshiryoku Gakkai-Shi ATOMO, 61(9), p.687 - 691, 2019/09
This report summarizes the contents of the session of the Health Physics and Environment Science Division, which was held in Atomic Energy Society of Japan 2019 Spring Meeting. In this session, six students and young researchers who engaged in the field of nuclear energy and radiation gave a lecture about health physics and environmental science research through their expertise. After the all presentations end, we took discussion time about the issues and future development in this field with all attendees. In this report, we summarized each lecture outline and discussion contents.
Ito, Hiroto*; Shiotsu, Hiroyuki; Tanaka, Yoichi*; Nishihara, Satomichi*; Sugiyama, Tomoyuki; Maruyama, Yu
JAEA-Data/Code 2018-012, 42 Pages, 2018/10
Chemical composition of fission products transported in nuclear facilities in severe accidents is controlled by slower chemical reaction rates, therefore, it could be different from that evaluated on the chemical equilibrium assumption. Hence, it is necessary to evaluate the chemical composition with reaction kinetics. On the other hand, databases applicable to the analysis of nuclear facilities have not been constructed because knowledge of reaction rates of complex chemical reactions in severe accidents is currently limited. Accordingly, we have developed the CHEMKEq code based on a partial mixed model with chemical equilibrium and reaction kinetics to decrease uncertainties of the chemical composition caused by the reaction rate. The CHEMKEq code, under mass conservation law, firstly evaluates chemical species obeying the chemical equilibrium model, and then, relatively slow reactions are solved by the reaction kinetics model. Moreover, the CHEMKEq code has a multiplicity of use in evaluations of chemical composition because general chemical equilibrium and reaction kinetics models are also available and databases required to calculation are external file formats. This report is the user's guide of the CHEMKEq code, showing models, solution methods, structure of the code and calculation examples. And information to run the CHEMKEq code is summarized in appendixes.
Sakai, Toshihiro
JAEA-Data/Code 2018-006, 75 Pages, 2018/07
Data of bulk chemical compositions (major elements and trace elements) and/or of modal compositions of the Toki granitic body are compiled as a data-base for the purpose of improving geological and petrological basic information of the Mizunami Underground Research Laboratory Project and the Regional Hydrogeological Study Project. 696 rock samples are collected from the outcrops and boreholes of the Regional Hydrogeological Study Project, and 636 rock samples are collected from the Mizunami Underground Research Laboratory Construction Site. The analysis data of rock samples, as granitic rock samples, intrusive rock samples and crack filling samples, are attached three-dimensional position information to each thesis and report.
Kogure, Toshihiro*; Yamaguchi, Noriko*; Segawa, Hiroyo*; Mukai, Hiroki*; Motai, Satoko*; Akiyama, Kotone*; Mitome, Masanori*; Hara, Toru*; Yaita, Tsuyoshi
Microscopy, 65(5), p.451 - 459, 2016/10
Times Cited Count:54 Percentile:97.07(Microscopy)Hoshino, Yuzuru; Sakamoto, Yoshiaki; Muroi, Masayuki*; Mukai, Satoru*
JAEA-Technology 2015-015, 96 Pages, 2015/07
In order to dispose of the radioactive waste which generates from post-irradiation examination (PIE) facilities, the common evaluation method of radioactivity in wastes from PIE should be established by the actual data such as radioactivity values and the theoretical calculation. In this study, the radioactivity concentrations of 17 nuclides (H-3, C-14, Co-60, Ni-63, Sr-90, Tc-99, Cs-137, Eu-154, U-234, U-235, U-238, Pu-238, Pu-239, Pu-240, Pu-241, Am-241, Cm-244) in combustible wastes stored in NUCLEAR DEVELOPMENT CORPORATION were measured from 3 samples and the radioactivity was calculated by ORIGEN-2 based on initial contents and operation record of the spent fuel. From the comparison of the obtained data by the radiological measurement with the calculated values, the subject to be solved for establishment of the radioactivity evaluation method for PIE was extracted.
Saito, Takumi; Hamamoto, Takafumi*; Mizuno, Takashi; Iwatsuki, Teruki; Tanaka, Satoru*
Journal of Analytical Atomic Spectrometry, 30(6), p.1229 - 1236, 2015/06
Times Cited Count:13 Percentile:60.40(Chemistry, Analytical)Size distribution and elemental compositions of colloids in granitic and sedimentary deep groundwater was determined by flow field flow fractionation (Fl-FFF) combined with ICP-MS. In the granitic groundwater organic colloids and various inorganic elements were found in limited size ranges (10 nm and 140 nm). The presence of different types of organic colloids was suggested in this groundwater. Most of the inorganic elements exhibited similar size distributions at 10 nm, which were largely overlapped with organic colloids rich in fluorophores. In the sedimentary groundwater small organic and probably inorganic colloids were found at 5 nm together with relatively large inorganic colloids. Organic colloids in this groundwater were homogeneous in terms of their sizes and the compositions of chromohores and fluorophores. The size distribution of inorganic elements depended on their types, indicating the presence of different host colloidal phases for them.
Ozu, Akira; Tachi, Yoshiaki; Arita, Yuji*
Reza Kenkyu, 42(12), p.913 - 917, 2014/12
Laser-induced breakdown spectroscopy (LIBS) analysis has been applied to the molten alloy production process, in which simulated metals (Zr, Cu, Sm, Ce) are used instead of nuclear metallic fuels contained minor actinide (MA), with the aim of in-situ monitoring the elementary composition of the surface of the molten alloy in a chamber and vapor particles generated from the surface of the molten alloy. The variation in the ratio of elementary composition of the surface of the molten alloy in the crucible was successfully observed depending on temperature of the crucible. The elementary composition of the vapor particles appeared in the molten alloy chamber was also measured. The practical experimental results show that LIBS technique is very useful for investigating the elementary composition in the process and understanding the behavior of molten alloy in the crucible.
Schwehr, K. A.*; Otosaka, Shigeyoshi; Merchel, S.*; Kaplan, D. I.*; Zhang, S.*; Xu, C.*; Li, H.-P.*; Ho, Y.-F.*; Yeager, C. M.*; Santschi, P. H.*; et al.
Science of the Total Environment, 497-498, p.671 - 678, 2014/11
Times Cited Count:14 Percentile:38.58(Environmental Sciences)A new, accurate and simple pH-dependent solvent extraction method combined with accelerator mass spectrometry (AMS) measurement for I/I isotopes and iodine speciation (iodide, iodate, and organo-I) quantification in liquids of any ionic strength has been developed. We then validated the AMS method for activity concentration measurements with a recently developed gas chromatography mass spectrometry method for I concentrations of 1 Bq/L or higher. This technique was applied to I-contaminated groundwater from the Savannah River Site, USA, and demonstrated changes of I and I concentrations and speciation along a pH, redox potential, and organic carbon gradient. The data suggest that I/I and species distribution is strongly pH dependent. The new method can now be applied to a wide range of chemically-diverse aquatic systems, including uncontaminated environments.
Miyamoto, Yutaka; Saito, Yoko; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu
Journal of Radioanalytical and Nuclear Chemistry, 271(1), p.83 - 88, 2007/01
Times Cited Count:0 Percentile:0.01(Chemistry, Analytical)Airborne dust samples were collected with a high-volume sampler at a fixed point in JAERI-Tokai for three years. Recently at JAERI-Tokai, a number of pine trees to arrest sand shifting was cut down. We analyzed the variation in elemental composition of the dust collected before and after felling the trees. It found, from the two-dimentional plots of ratio of elemental concentration such as Sc/Na-Cl/Na ratios, almost all samples consisted of mixture of sea-salt and soil. There were some differences between the elemental composition of the dust collected before and after felling the trees.
Shimura, Kenichiro; Yamaguchi, Kenji; Sasase, Masato*; Yamamoto, Hiroyuki; Shamoto, Shinichi; Hojo, Kiichi
Vacuum, 80(7), p.719 - 722, 2006/05
Times Cited Count:9 Percentile:34.22(Materials Science, Multidisciplinary)no abstracts in English
Hayakawa, Takehito; Iwamoto, Nobuyuki; Shizuma, Toshiyuki; Kajino, Toshitaka*; Umeda, Hideyuki*; Nomoto, Kenichi*
European Physical Journal A, 27(S1), p.123 - 128, 2006/03
Times Cited Count:0 Percentile:0.01(Physics, Nuclear)no abstracts in English
Hoshino, Tsuyoshi; Yasumoto, Masaru*; Tsuchiya, Kunihiko; Hayashi, Kimio; Nishimura, Hidetoshi*; Suzuki, Akihiro*; Terai, Takayuki*
Fusion Engineering and Design, 81(1-7), p.555 - 559, 2006/02
Times Cited Count:19 Percentile:77.36(Nuclear Science & Technology)no abstracts in English
Otobe, Haruyoshi; Nakamura, Akio; Yamashita, Toshiyuki; Minato, Kazuo
Journal of Nuclear Materials, 344(1-3), p.219 - 222, 2005/09
Times Cited Count:3 Percentile:24.15(Materials Science, Multidisciplinary)Actinides-bearing zirconias are prominent candidate materials for various nuclear applications: targets for actinide transmutation, inert material fuels, radioactive waste forms, etc. In this study, the oxygen potential (g(O)) behavior of fluorite-type (F-type) ZrPuO has been measured by EMF method using the zirconia oxygen sensor. It was found that the g(O) values of F-type ZrPuO were about 150 kJ/mol higher than those of F-type PuO at the same oxygen-nonstoichiometric (O/M) values. The g(O) values of F-type ZrPuO were 50 kJ/mol lower than those of pyrochlore ZrPuO at the same O/M values. These results suggest that the g(O) behavior depends on the cation and anion ordering/disordering, in addition to the cation composition ratio (Zr/Pu).
Mizuno, Tsuyoshi*; Maeda, Toshikatsu; Bamba, Tsunetaka*
JAERI-Conf 2005-007, p.225 - 229, 2005/08
no abstracts in English
Yamaguchi, Tetsuji; Minase, Naofumi; Iida, Yoshihisa; Tanaka, Tadao; Nakayama, Shinichi
JAERI-Conf 2005-007, p.150 - 155, 2005/08
no abstracts in English
Kameo, Yutaka; Haraga, Tomoko; Nakashio, Nobuyuki; Hoshi, Akiko; Nakashima, Mikio
Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(4), p.354 - 362, 2004/12
In order to investigate chemical stability of solidified products made from Low Level Radioactive Wastes (LLW) by plasma melting, a leaching test based on the MCC (Material Characterization Center)-3S Agitated Powder Leach Test Method was performed to determine Normalized Elemental Mass Loss (NL) of both main components (Na, Al, Si, Ca, and Fe) of the solidified product and radioactive tracers (Co, Cs, and Eu) incorporated into it. The results of leaching test indicated that NLi value was greatly affected by basicity defined as weight ratio of CaO to SiO in the solidified product, while effect of FeO concentration on NL value was small. In the case of basicity less than 0.8, logarithm of NL linearly increased with the basicity, implying that NL value can be estimated by chemical composition of the solidified products.
Nakashio, Nobuyuki; Nakashima, Mikio; Hirabayashi, Takakuni*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(3), p.279 - 287, 2004/09
Large-scale melting tests of simulated miscellaneous solid wastes were conducted to characterize solidified products (50L-drum size). Two heating modes were adopted in the tests: hybrid heating and induction heating modes. In the former, wastes were heated with both an induction furnace and a plasma torch, and in the latter, an electrically-conductive crucible was used with the induction furnace. Visual observation, chemical analysis and radioactivity measurements were conducted to the solidified products. It was found that the radioisotope distribution of solidified products was almost homogeneous. There was no remarkable deterioration in the solidified products subsequent to the leaching test.