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Yuan, X.*; Hu, Q. H.*; Fang, X.*; Wang, Q. M.*; Ma, Y.*; Tachi, Yukio
Sedimentary Geology, 465, p.106633_1 - 106633_14, 2024/05
Amaya, Masaki
High Temperature Corrosion of Materials, 15 Pages, 2024/00
Times Cited Count:0 Percentile:0.02(Metallurgy & Metallurgical Engineering)Kim, M.; Malins, A.*; Machida, Masahiko; Yoshimura, Kazuya; Saito, Kimiaki; Yoshida, Hiroko*
Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 22(4), p.156 - 169, 2023/11
Dose reduction factor of a Japanese house is important information in the external exposure estimation of returning residents. In 2019, a total of 19 wooden houses were surveyed in Iitate Village and Namie Town using a gamma plotter that can continuously measure the air dose rate. In addition, the characteristics of the reduction factor were investigated from the measured air dose rate. In the vicinity of houses, uncontaminated areas exist underneath houses and, the ratio of paved surfaces such as asphalt roads is relatively high; furthermore, the pavement has a tendency for the radiation source to decay quickly. Therefore, the air dose rate near the house showed a relatively low value in common at all sites. Air dose rates above unpaved surfaces showed higher values and larger variations than those above paved surfaces within a radius of 50 m form the center of a house. The reduction factor was widely distributed even for one house, if the ratio of every air dose rate observed inside and outside the house is considered. It is suggested that a realistic reduction factor may not be obtained when the reduction factor is obtained based on the measured values at a small number of points that do not have the representativeness of the radiation field to be measured.
Wang, Q.*; Ma, N.*; Huang, W.*; Shi, J.*; Luo, X.-T.*; Tomitaka, Sora*; Morooka, Satoshi; Watanabe, Makoto*
Materials Research Letters (Internet), 11(9), p.742 - 748, 2023/09
Tatsuno, Takahiro*; Nihei, Naoto*; Yoshimura, Kazuya; Ote, Nobuhito*
Journal of Radioanalytical and Nuclear Chemistry, 332(6), p.1677 - 1686, 2023/06
Times Cited Count:1 Percentile:68.31(Chemistry, Analytical)Takino, Kazuo; Oki, Shigeo
JAEA-Data/Code 2023-003, 26 Pages, 2023/05
Since next-generation fast reactors aim to achieve a higher core discharge burn-up than conventional reactors do, core neutronics design methods must be refined. Therefore, a suitable analysis condition is required for the analysis of burn-up nuclear characteristics to accomplish sufficient estimation accuracy while maintaining a low computational cost. We investigated the effect of the analysis conditions on the accuracy of estimation of the burn-up nuclear characteristics of next-generation fast reactors in terms of neutron energy groups, neutron transport theory, and spatial mesh. This study treated the following burn-up nuclear characteristics: criticality, burn-up reactivity, control rod worth, breeding ratio, assembly-wise power distribution, maximum linear heat rate, sodium void reactivity, and Doppler coefficient for the equilibrium operation cycle. As a result, it was found that the following conditions were the most suitable: 18-energy-group structure, 6 spatial meshes per assembly with diffusion approximation. Additionally, these conditions should apply to correction factors for energy group structure, spatial mesh and transport effects.
Ito, Ayumi*; Yamashita, Susumu; Tasaki, Yudai; Kakiuchi, Kazuo; Kobayashi, Yoshinao*
Journal of Nuclear Science and Technology, 60(4), p.450 - 459, 2023/04
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)Yanagisawa, Hiroshi; Umeda, Miki; Motome, Yuiko; Murao, Hiroyuki
JAEA-Technology 2022-030, 80 Pages, 2023/02
Nuclear criticality benchmark analyses were carried out for TRIGA-type reactor systems in which uranium-zirconium hydride fuel rods are loaded by using the continuous-energy Monte Carlo code MVP with the evaluated nuclear data library JENDL-5. The analyses cover two sorts of benchmark data, the IEU-COMP-THERM-003 and IEU-COMP-THERM-013 in the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Handbook, and effective neutron multiplication factors, reactivity worths for control rods etc. were calculated by JENDL-5 in comparison with those by the previous version of JENDL. As the results, it was confirmed that the effective neutron multiplication factors obtained by JENDL-5 were 0.4 to 0.6% greater than those by JENDL-4.0, and that there were no significant differences in the calculated reactivity worths by between JENDL-5 and JENDL-4.0. Those results are considered to be helpful for the confirmation of calculation accuracy in the analyses on NSRR control rod worths, which are planned in the future.
Ueta, Shohei; Imai, Yoshiyuki; Watanabe, Masashi; Segawa, Tomoomi; Yan, X.
International Journal of Applied Ceramic Technology, 20(1), p.261 - 265, 2023/01
Times Cited Count:2 Percentile:26.76(Materials Science, Ceramics)Reeb, C.*; Davy, C. A.*; Pierlot, C.*; Bertin, M.*; Cantarel, V.; Lambertin, D.*
Cement and Concrete Research, 162, p.106963_1 - 106963_16, 2022/12
Times Cited Count:6 Percentile:56.94(Construction & Building Technology)Ochs, M.*; Dolder, F.*; Tachi, Yukio
Applied Geochemistry, 136, p.105161_1 - 105161_11, 2022/01
Times Cited Count:4 Percentile:63.38(Geochemistry & Geophysics)Various types of radioactive wastes and environments contain organic substances that can stabilize the aqueous complexes with radionuclides and therefore lead to a decrease of sorption. The present study focuses on testing a methodology to quantify sorption reduction factors (SRFs) in the presence of organic ligands for cement systems. Three approaches for the estimation of SRFs; (1) analogy with solubility enhancement factors, (2) radionuclide speciation based on the thermodynamic calculations, and (3) experimental sorption data in ternary systems, were coupled and tested for the representative organic ligands (ISA and EDTA) and selected key radionuclides (actinides). Our approach allows to critically evaluate the dependence of SRFs for various systems on the chosen method of quantification, in accordance with the data availability for a given systems. The reliable SRFs can only be derived from the sorption measurements in ternary systems. SRF often need to be derived in the absence of such direct evidence, and estimations need to be made based on analogies and speciation information. However, such estimates may be subject to substantial uncertainties.
Villaret, F.*; Boulnat, X.*; Aubry, P.*; Yano, Yasuhide; Otsuka, Satoshi; Fabregue, D.*; de Carlan, Y.*
Materials Science & Engineering A, 824, p.141794_1 - 141794_10, 2021/09
Times Cited Count:3 Percentile:24.75(Nanoscience & Nanotechnology)Miyahara, Shinya*; Kawaguchi, Munemichi; Seino, Hiroshi; Atsumi, Takuto*; Uno, Masayoshi*
Proceedings of 28th International Conference on Nuclear Engineering (ICONE 28) (Internet), 6 Pages, 2021/08
In a postulated accident of fuel pin failure of sodium cooled fast reactor, a fission product cesium will be released from the failed pin as an aerosol such as cesium iodide and/or cesium oxide together with a fission product noble gas such as xenon and krypton. As the result, the xenon and krypton released with cesium aerosol into the sodium coolant as bubbles have an influence on the removal of cesium aerosol by the sodium pool in a period of bubble rising to the pool surface. In this study, cesium aerosol removal behavior due to inertial deposition, sedimentation and diffusion from a noble gas bubble rising through liquid sodium pool was analyzed by a computer program which deals with the expansion and the deformation of the bubble together with the aerosol absorption considering the effects of particle size distribution and agglomeration in aerosols. In the analysis, initial bubble diameter, sodium pool depth and temperature, aerosol particle diameter and density, initial aerosol concentration in the bubble were changed as parameter, and the results for the sensitivities of these parameters on decontamination factor (DF) of cesium aerosol were compared with the results of the previous study in which the effects of particle size distribution and agglomeration in aerosols were not considered. From the results, it was concluded that the sensitivities of initial bubble diameter, the aerosol particle diameter and density to the DF became significant due to the inertial deposition of agglomerated aerosols. To validate these analysis results, the simulation experiments have been conducted using a simulant particles of cesium aerosol under the condition of room temperature in water pool and air bubble systems. The experimental results were compared with the analysis results calculated under the same condition.
Abe, Tomohisa; Yoshimura, Kazuya; Sanada, Yukihisa
Aerosol and Air Quality Research, 21(7), p.200636_1 - 200636_11, 2021/07
Times Cited Count:4 Percentile:26.95(Environmental Sciences)Lu, K.; Katsuyama, Jinya; Li, Y.
Journal of Pressure Vessel Technology, 142(5), p.051501_1 - 051501_10, 2020/10
Times Cited Count:2 Percentile:15.42(Engineering, Mechanical)Igarashi, Hiroshi
JAEA-Review 2020-006, 261 Pages, 2020/09
A literature review was conducted on the increase in surface area of vitrified products of HLW due to the fracturing caused by cooling during glass pouring process and by mechanical impact, from the perspective of a parameter of the radionuclide release model in the performance assessment of geological disposal system studied overseas. The review was focused on the value of surface area increase factor set as a parameter in the model, the experimental work to evaluate an increase in surface area, and how the parameters on surface area were determined based on the experimental results. The surface area obtained from the experiments executed in Japan was also discussed in comparison with the overseas studies. On the basis of the investigation, the effects of various conditions on the surface area were studied, such as a diameter of vitrified product, cooling condition during and after the glass pouring, impact on vitrified products during their handling, environment after the closure of disposal facility, and others. The causes of fracturing are associated with the phenomena or events in the waste management process such as production, transport, storage, and disposal. The surface area increase factors set in the nuclide release model of the glass and their bases were reviewed. In addition, the measured values and the experimental methods for surface increase factors published so far were compared. Accordingly, the methods for measuring surface area as the bases were identified for these factors set in the models. The causes of fracturing and features of these factors were studied with respect to the relation with the waste management process. The results from the review and assessment can contribute to the expanding the knowledge for the conservative and realistic application of these factors to performance assessment, and to the developing and upgrading of safety case as a consequence.
Miyahara, Shinya*; Kawaguchi, Munemichi; Seino, Hiroshi
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08
In a postulated accident of fuel pin failure of sodium cooled fast reactor, a fission product cesium will be released as an aerosol such as cesium iodide and/or oxide together with xenon and/or krypton. In this study, cesium aerosol removal behavior due to inertial deposition, sedimentation and diffusion was analyzed by a computer program which deals with the expansion and the deformation of the bubble together with the aerosol absorption. Initial bubble diameter, sodium pool depth and temperature, aerosol particle diameter and density, initial aerosol concentration were changed as parameter. From the results, it was concluded that the initial bubble diameter was most sensitive parameter to the decontamination factor (DF). It was found that the sodium pool depth, the aerosol particle diameter and density have also important effect on the DF, but the sodium temperature has a marginal effect. To meet these results, the experiments are under planning to validate the results.
Hirouchi, Jun; Takahara, Shogo; Komagamine, Hiroshi*; Munakata, Masahiro
Proceedings of Asian Symposium on Risk Assessment and Management 2019 (ASRAM 2019) (USB Flash Drive), 7 Pages, 2019/09
no abstracts in English
Horiguchi, Naoki; Miyahara, Naoya; Uesawa, Shinichiro; Yoshida, Hiroyuki; Osaka, Masahiko
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05
For source term evaluation from reactor buildings (RBs) in LWR severe accidents, we have launched to develop an evaluation method of FP aerosol particle deposition onto surfaces of internal structures in an RB based on computational fluid dynamics (CFD). This paper describes development of a CFD simulation tool as the base part of the evaluation method. A preliminary simulation for a representative RB under a representative flow condition was conducted to confirm the tool performance by roughly grasping the deposition behaviors of FP aerosol particle and decontamination factor (DF) in the RB. Calculation results showed that most of aerosol particles were deposited along with gas flow formed by the internal structures in the RB, demonstrating the advantageous feature of the present CFD tool. The DFs from 4 to 14 were obtained with increase of the particle diameters from 0.1 to 10 m as expected in terms of the particle movement equation.
Iwase, Hiroki*; Kawai, Risa*; Morishima, Ken*; Takata, Shinichi; Yoshimura, Tomokazu*; Shibayama, Mitsuhiro*
Journal of Colloid and Interface Science, 538, p.357 - 366, 2019/03
Times Cited Count:13 Percentile:41.52(Chemistry, Physical)