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Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Fukasawa, Tomonori*; Fukui, Kunihiro*
Funtai Kogakkai-Shi, 57(9), p.485 - 494, 2020/09
In the spent fuel reprocessing process, a mixed solution of uranyl nitrate and plutonium nitrate is converted into mixed oxide powder by the microwave heating. To evaluate the applicability to the industrial-scale and acquire the characteristics data of the microwave heating denitration of various metal nitrate aqueous solutions based on the knowledge studied in the development of laboratory-scale basic experiments, the microwave heating characteristics and metal oxide powder properties were investigated using cerium nitrate, cobalt nitrate and copper nitrate aqueous solutions. The progress rate of the denitration reaction was depended on the position, and the denitration reaction proceeded faster at the periphery than at the center. The morphologies of the synthesized products were porous and hard dry solid with cerium nitrate aqueous solution, foamed dry solid with cobalt nitrate aqueous solution, and powdery particles with copper nitrate aqueous solution. The denitration ratio and average particle size of the synthesized products increased in the order of the cerium nitrate aqueous solution, the cobalt nitrate aqueous solution, and the copper nitrate aqueous solution. The numerical simulations revealed that the periphery of the bottom surface of the metal nitrate aqueous solution was heated by microwaves. This results consistent with the experimental results in which the denitration reaction started from the periphery of the metal nitrate aqueous solution.
Segawa, Tomoomi; Yamamoto, Kazuya; Makino, Takayoshi; Iso, Hidetoshi; Kawaguchi, Koichi; Ishii, Katsunori; Sato, Hisato; Fukasawa, Tomonori*; Fukui, Kunihiro*
Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.738 - 745, 2019/09
In the MOX fuel fabrication process, the dry grinding technology of mixed oxide pellets have been developed for the effective use of nuclear fuel materials. To develop a technology to control the particle size of dry recovered powder, the performance of the buhrstone mill and the collision plate type jet mill were studied using a simulated powder of particle size distribution about 500 
m. We found that the particle size can be controlled at the range of about 250 m or less by both by adjusting the clearance between the grinding wheels of the buhrstone mill, and the clearance and elevation angle of the clarification zone of the collision plate type jet mill. And furthermore, the collision plate type jet mill is considered to be suitable for particle size control because the operating parameters of the classifier can be finely adjusted.
Fukui, Katsunori*; Hashiba, Kimihiro*; Matsui, Hiroya
JAEA-Research 2018-006, 57 Pages, 2018/10
JAEA-Research-2018-006.pdf:2.99MB
It is important to evaluate the stability of a repository for high-level radioactive waste not only during the design, construction and operation phases, but also during the post-closure period, for time frames likely exceeding several millennia or longer. The rock mass around the tunnels could be deformed through time in response to time dependent behavior. In view of above points, this study has been started as a collaboration study with the University of Tokyo from FY2016. In the FY2017, the creep test of Tage tuff was continuously conducted and reached its twentieth year. The overview of the test was described, and the phenomenological aspects and the mechanisms of the creep of tuff were discussed with comparing the long- and short-term creep tests. The effects of loading rate and water content on rock strength were examined under various water conditions. The variable-compliance-type constitutive model was modified to reproduce those under uniaxial tension.
Fukui, Katsunori*; Hashiba, Kimihiro*; Matsui, Hiroya
JAEA-Research 2017-010, 61 Pages, 2017/11
JAEA-Research-2017-010.pdf:16.86MB
JAEA has started this study as a collaboration study with Tokyo University from 2016. In the fiscal year of 2016, creep testing on Tage tuff was continuously conducted. Existing theory of rate process and stochastic process was modified to be applied to evaluate effects of water, and then the modified theory was validated based on the results of strength and creep tests performed under dry and wet conditions. Furthermore, effects of water contents on stress-strain curves were examined by uniaxial compression testing under various water content conditions.
Hashiba, Kimihiro*; Fukui, Katsunori*; Sugita, Yutaka; Aoyagi, Kazuhei
Proceedings of ITA-AITES World Tunnel Congress 2017 (WTC 2017) (USB Flash Drive), 8 Pages, 2017/06
It is essential to understand the mechanical and rheological characteristics of diatomaceous and siliceous mudstones for the construction of underground structures and for the assessment of their long-term stability. In this study, the siliceous mudstone of the Wakkanai Formation was applied to various laboratory tests: compression test, creep test, relaxation test, drying shrinkage test, and slaking test. The test results showed that water has a major impact on the mechanical and rheological properties of the siliceous mudstone. In addition, water content at a tunnel wall was measured in the Horonobe URL. Comparing the results of the laboratory tests and the in situ measurement, the effect of water on the tunnel stability was discussed.
Fukui, Katsunori*; Hashiba, Kimihiro*; Matsui, Hiroya; Kuwabara, Kazumichi; Ozaki, Yusuke
JAEA-Research 2016-014, 52 Pages, 2016/09
JAEA-Research-2016-014.pdf:7.19MB
With respect to high-level radioactive waste disposal, knowledge of the long-term mechanical stability of shafts and galleries excavated in rock is required, not only during construction and operation but also over a period of thousands of years after closure. On the other hand, it is known that rock and the rock mass surrounding the disposal gallery shows time dependent behavior such as creep or the stress-relaxation. It becomes the issue in the stability evaluation of the disposal gallery to grasp the behavior. In order to solve this issue, we pushed forward research development. we pushed forward research development. In the fiscal year of 2015, the creep testing machine for Tage tuff was moved to the new building. The creep test was continuously conducted and the total testing time exceeded 17 years. The testing equipment and procedure were examined to investigate the deformation, failure and time-dependency of rock under wet conditions and between room temperature and 100
C. The long-term strength of rock under triaxle stress state was researched with the aid of laboratory testing results and in situ stress measurement.
Fukui, Katsunori*; Hashiba, Kimihiro*; Sato, Toshinori; Kuwabara, Kazumichi; Takayama, Yusuke
JAEA-Research 2015-015, 61 Pages, 2015/11
JAEA-Research-2015-015.pdf:5.52MB
With respect to high-level radioactive waste disposal, knowledge of the long-term mechanical stability of shafts and galleries excavated in rock is required, not only during construction and operation but also over a period of thousands of years after closure. On the other hand, it is known that rock and the rock mass surrounding the disposal gallery shows time dependent behavior such as creep or the stress-relaxation. It becomes the issue in the stability evaluation of the disposal gallery to grasp the behavior. About this issue, we pushed forward research development. In the fiscal year of 2014, the creep test was continuously conducted and the total testing time exceeded 17 years. The testing equipment and procedure were examined to investigate the deformation, failure and time-dependency of rock under wet conditions and between room temperature and 100C. The long-term strength of rock under triaxial stress state was researched with the aid of laboratory testing results and in situ stress measurement.
Segawa, Tomoomi; Kawaguchi, Koichi; Ishii, Katsunori; Suzuki, Masahiro; Arimitsu, Naoki*; Yoshida, Hideto*; Fukui, Kunihiro*
Advanced Powder Technology, 26(3), p.983 - 990, 2015/05
Times Cited Count：8 Percentile：27.86(Engineering, Chemical)Denitration of the aqueous solution of nickel nitrate hexahydrate (Ni(NO
)
6HO) by a microwave heating method was investigated. Since Ni(NO)6HO aqueous solution cannot be heated to over 300 C by microwave irradiation owing to the low microwave absorptivity of its intermediate, NiO could not previously be obtained by microwave heating. We propose a novel NiO synthesis method that uses microwave heating without the risk of chemical contamination. A NiO powder reagent was added to the solution as a microwave acceptor. The denitration efficiency to NiO could be improved by an adiabator around the reactor to increase the temperature homogeneity in the reactor. Numerical simulations also reveal that the use of the adiabator results in remarkable changes in the electromagnetic field distribution in the reactor, temperature inhomogeneity decreases.
Hashiba, Kimihiro*; Fukui, Katsunori*; Sugita, Yutaka; Sanada, Masanori*
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 21(2), p.75 - 82, 2014/12
Diatomaceous earth and siliceous rock are widespread in the areas along the Sea of Japan in Hokkaido Prefecture, Akita Prefecture, Noto Peninsula and Oki Islands. To construct underground structures in the siliceous rock mass, it is essential to understand its mechanical properties. In this study, siliceous mudstone of the Wakkanai formation obtained from the deep underground in Horonobe, Hokkaido was applied to various laboratory tests; uniaxial compression test, Brazilian tension test, drying shrinkage test and the test to investigate the time dependent behavior and strength recovery. The testing results showed that water has a huge effect on the deformation and failure of the siliceous mudstone; when the specimen is air dried in room temperature, the axial shrinkage strain reashes 0.9% and the strength is twice larger than that in wet condition. It was found that the siliceous mudstone exhibits the same degree of time dependent behavior and strength recovery as other rocks such as tuff and sandstone.
Fukui, Katsunori*; Hashiba, Kimihiro*; Sato, Toshinori; Sanada, Hiroyuki; Kuwabara, Kazumichi
JAEA-Research 2014-020, 50 Pages, 2014/11
JAEA-Research-2014-020.pdf:2.8MB
On the radioactive waste disposal, the long-term mechanical stability of shafts and galleries excavated in rock is required. Therefore, it is very important to understand the time-dependent behavior of rock mass for evaluating long-term mechanical stability. The purpose of this study is determining the mechanisms of time-dependent behavior of rock mass by precise testing, observation and measurement in order to develop methods for evaluating long-term mechanical stability of a rock mass. This report describes the results of the activities in fiscal year 2013. In Chapter 1, we described the overview and background of this study. In Chapter 2, the results of a long-term creep test on Tage tuff, started in fiscal year 1997 are described. In Chapter 3, the result of organization and analysis for time-dependent behavior of crystalline rock was described. In Chapter 4, for the drafting of in-situ test plan, examination of the numerical analysis technique of rock mass was carried out.
Fukui, Katsunori*; Hashiba, Kimihiro*; Tanno, Takeo; Hikima, Ryoichi; Sanada, Hiroyuki; Sato, Toshinori
JAEA-Research 2013-031, 52 Pages, 2013/12
JAEA-Research-2013-031.pdf:4.06MB
It is very important to understand the time-dependent behavior of rock for evaluating long-term mechanical stability. The purpose of this study is determining the mechanisms of time-dependent behavior of rock by the precise test, observation and measurement, to develop methods for evaluating long-term mechanical stability. This report describes the results of the activities in fiscal year 2012. In Chapter 1, we provide an overview and the background to this study. In Chapter 2, the results of a long-term creep test on Tage tuff, started in fiscal year 1997 are described. In Chapter 3, the experimental results concerning the loading-rate dependency of strength were examined to understand the time-dependency of rock. In Chapter 4, the stability of tunnels, around which rock stress is larger than that around a circular tunnel, were examined to obtain useful information on the future plan for 
tests in the underground research laboratory.
Sugita, Yutaka; Sanada, Masanori; Fujita, Tomoo; Hashiba, Kimihiro*; Fukui, Katsunori*; Okubo, Seisuke*
Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.207 - 212, 2013/01
Radionuclide migration can be undesirably increased by weakening the mechanical properties of a rock mass in the excavated disturbed zone (EDZ) around the tunnels of a geolical disposal facility for high level radioactive waste. Laboratory testing of loading stress and loading time on failed siliceous mudstone specimens has identified the potential for the long-term recovery of the strength and impermeability of the rock mass in the EDZ.
Okubo, Seisuke*; Fukui, Katsunori*; Hashiba, Kimihiro*; Hikima, Ryoichi; Tanno, Takeo; Sanada, Hiroyuki; Matsui, Hiroya; Sato, Toshinori
JAEA-Research 2011-040, 54 Pages, 2012/02
JAEA-Research-2011-040.pdf:2.85MB
With respect to high-level radioactive waste disposal, knowledge of the long-term mechanical stability of shafts and galleries excavated in rock are required, not only during construction and operation but also over a period of thousands of years after closure. Therefore, it is very important to understand the time-dependent behavior of rock for evaluating long-term mechanical stability. This report describes the results of the activities in FY2010. In Chapter 1, we provide an overview and the background to this study. In Chapter 2, the results of a long-term creep test on Tage tuff, started in FY1997 are described. In Chapter 3, the relation of loading-rate dependency of strength and stress dependency of creep life, the relationship of time dependency and probability distribution of strength or creep life and size effects are discussed to indicate more clearly the meaning of the value of "n" to express the degree of time dependency of the rock. In Chapter 4, failure criterions of a rock mass considering time dependency are discussed. In Chapter 5, the FEM analysis implemented with a generalized variable-compliance-type constitutive equation considering the change of "n" in confining pressure and strength distribution of rock mass carried out to clarify the long-term behavior of Toki granite is described. Finally, based on the numerical analysis, an in situ testing method is proposed.
Hirokawa, Katsunori; Hisada, Masaki; Fukui, Yasutaka; Inoue, Setsunari
Dekomisshoningu Giho, (44), p.33 - 42, 2011/09
In Japan Atomic Energy Agency, facilities where the mission was finished and superannuation facilities are decommissioned systematically for rationalization and efficiency improvement of business. It is necessary to execute safe and economically by making good use of the technology according to the kind of facilities and the feature of the dismantlement object. In this report, it reports on the radiation measurement, decontamination and dismantling technology that develops in the Waste Treatment Technology Section O-ARAI Research and Development Center JAEA.
Yamazaki, Masanao; Fukui, Katsunori*; Minamide, Masashi*; Hatsuyama, Yoshihiro*
no journal, ,
The correlation between the energy per unit excavated volume calculated from the electric power consumption of the road header during the shaft excavation and the rock properties observed at the excavation wall was investigated in the Horonobe Underground Research Project. As a result, it was found that the energy per unit excavated volume correlate better with the rock mass classification determined from both a fracture intensity as well as a rock strength rather than with a fracture intensity. We will continue to measure the electric power consumption data in order to establish rock mass evaluation method using the energy per unit excavated volume.
Fukui, Katsunori*; Okubo, Seisuke*; Inagaki, Daisuke; Hatsuyama, Yoshihiro*; Yamamoto, Takuya*
no journal, ,
no abstracts in English
Fukui, Kunihiro*; Arimitsu, Naoki*; Yamamoto, Tetsuya*; Yoshida, Hideto*; Yamamoto, Takuma*; Ishii, Katsunori; Suzuki, Masahiro
no journal, ,
no abstracts in English
Saiki, Yuta*; Fukui, Kunihiro*; Yamamoto, Tetsuya*; Yoshida, Hideto*; Yamamoto, Takuma*; Ishii, Katsunori; Suzuki, Masahiro
no journal, ,
no abstracts in English
Hikima, Ryoichi; Sato, Toshinori; Sanada, Hiroyuki; Tanno, Takeo; Hirano, Toru*; Yamashita, Masayuki*; Ishiyama, Koji*; Fukui, Katsunori*
no journal, ,
no abstracts in English
Hashiba, Kimihiro*; Fukui, Katsunori*; Matsui, Hiroya
no journal, ,
This poster summarize the results of Study on Crystalline Rock Aiming at Evaluation Method of Long-Term Behaviour of Rock Mass in FY 2016
