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Nakazawa, Osamu; Takiya, Hiroaki; Murakami, Masashi; Donomae, Yasushi; Meguro, Yoshihiro
JAEA-Review 2023-012, 6 Pages, 2023/08
JAEA-Review-2023-012.pdf:0.93MB
The selection of back-end technology development issues to be prioritized and their schedule of the Japan Atomic Energy Agency (JAEA) have been put together as the "Strategic Roadmap for Back-end Technology Development." The results of questionnaires on development technologies (seeds) and technical issues (needs) within JAEA conducted in FY2022 were reflected in the selection. The issues were extracted from among those that match the seeds and needs, from the perspective of early implementation in the work front and the perspective of common issues, and nine themes were selected. We will build a cross-organizational implementation framework within JAEA and aim to implement the development results in the work front as well as social implementation.
Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.
Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03
Times Cited Count：51 Percentile：96.49(Astronomy & Astrophysics)Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 
C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.
Abe, Tomohisa; Shimazaki, Takejiro; Osugi, Takeshi; Nakazawa, Osamu; Yamada, Naoto*; Yuri, Yosuke*; Sato, Takahiro*
QST-M-16; QST Takasaki Annual Report 2017, P. 140, 2019/03
no abstracts in English
Irisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu
QST-M-16; QST Takasaki Annual Report 2017, P. 63, 2019/03
no abstracts in English
-ray during dehydrationIrisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu
QST-M-8; QST Takasaki Annual Report 2016, P. 63, 2018/03
A solidification technique with minimized water content is being developed using a phosphate cement for safe storage of secondary radioactive wastes in the Fukushima Daiichi Nuclear Power Plant. To understand the applicability of the solidification technique for the actual secondary wastes, phosphate cement during dehydration was irradiated by 
Co -ray. The G(H
) for the phosphate cement decreased with time during dehydration, and was not detected after 7 days. Moreover, the Co -ray irradiation during dehydration did not change the crystalline and amorphous phases of the phosphate cement.
Sato, Junya; Kikuchi, Hiroshi*; Kato, Jun; Sakakibara, Tetsuro; Matsushima, Ryotatsu; Sato, Fuminori; Kojima, Junji; Nakazawa, Osamu
QST-M-8; QST Takasaki Annual Report 2016, P. 62, 2018/03
no abstracts in English
Kato, Jun; Nakagawa, Akinori; Taniguchi, Takumi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro
JAEA-Review 2017-015, 173 Pages, 2017/07
JAEA-Review-2017-015.pdf:6.67MB
Various radioactive wastes have been generated at the Fukushima Daiichi Nuclear Power Station (1F). To dispose of the wastes underground, it is necessary to make a suitable waste package by the volume reduction and solidification of the wastes. To plan the future decommissioning of 1F, it is also necessary to estimate feasibility of existing treatment technology for those wastes. Therefore the document survey has been performed about volume reduction and solidification technologies that have domestic or foreign experiences of practical treatment for radioactive wastes to assist selection of suitable treatment of the wastes. This report shows the arranged results. The 1F wastes are classified into two groups, homogeneous particulate and liquid wastes and heterogeneous solid wastes. The needful items for the feasibility study such as a technology name, a fundamental principle, treatment efficiency, and characteristic of solidified waste are summarized in each group.
Irisawa, Keita; Taniguchi, Takumi; Namiki, Masahiro; Garc
a-Lodeiro, I.*; Osugi, Takeshi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro; Kinoshita, Hajime*
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 6 Pages, 2017/04
A solidification technique with minimized water content is being developed using phosphate cements for the safe storage of secondary radioactive wastes in the Fukushima Daiichi Nuclear Power Plant. Conventional cement systems become solidified via hydration reactions, and need a certain water content. Phosphate cement systems, however, become solidified via an acid-base reaction, and so they only require water mainly for reasons of workability. A reduced water content of phosphate cement systems is beneficial for the immobilization of the radioactive wastes from mitigating the potential to generate hydrogen gas by the radiolysis of water by radioactive wastes. The current study investigated the water content and mineralogy of calcium aluminate cement (CAC) and phosphate-modified CAC (CAP) cured in open systems at 60, 90 and 120 C and in a closed system at 20 C as a reference case. Water contents in both the CAC and the CAP were seen to decrease as curing progressed. For 
90 C, the CAP contained less water than CAC. Free water in CAC converted to structural water by heat treatment, but this was not the case for CAP. An orthophosphate hydrate salt, a precursor phase of hydroxyapatite, was found in CAP when cured at 20 and 60 C, and a mixture of the orthophosphate hydrate salt and hydroxyapatite, Ca
(PO
)
(OH), were formed in the CAP when cured at 90 C. Phosphate products in CAP cured at 120 C appears to consist of a different phosphate phase compared with the CAP cured at 20, 60 and 90 C.
Sato, Junya; Suzuki, Shinji*; Kato, Jun; Sakakibara, Tetsuro; Meguro, Yoshihiro; Nakazawa, Osamu
QST-M-2; QST Takasaki Annual Report 2015, P. 87, 2017/03
no abstracts in English
Sato, Junya; Suzuki, Shinji*; Kato, Jun; Sakakibara, Tetsuro; Meguro, Yoshihiro; Nakazawa, Osamu
QST-M-2; QST Takasaki Annual Report 2015, P. 88, 2017/03
no abstracts in English
Abe, Tomohisa; Shimazaki, Takejiro; Nakayama, Takuya; Osone, Osamu; Osugi, Takeshi; Nakazawa, Osamu; Yuri, Yosuke*; Yamada, Naoto*; Sato, Takahiro*
QST-M-2; QST Takasaki Annual Report 2015, P. 83, 2017/03
no abstracts in English
Meguro, Yoshihiro; Nakagawa, Akinori; Kato, Jun; Sato, Junya; Nakazawa, Osamu; Ashida, Takashi
Proceedings of International Conference on the Safety of Radioactive Waste Management (Internet), p.139_1 - 139_4, 2016/11
A variety of radioactive wastes have been generated in decommissioning of Fukushima Daiichi Nuclear Power Station. It is necessary to evaluate feasibility of conditioning methods to these wastes, because the majority of such wastes have not been solidified in Japan. The authors investigated an approach for screening of conditioning methods for the Fukushima wastes on the basis of the findings of the existing methods and results of fundamental solidification tests using synthetic Fukushima wastes. Here five solidification methods were selected, and also 13 wastes with different chemical composition are solidified, and characteristics of the solidified form are studied. A screening flow was proposed, and evaluation criteria on each step in the flow was set up. In this presentation a trial result was opened for a waste and improvements of the screening flow found in the trial evaluation was described.
Irisawa, Keita; Komatsuzaki, Toshio; Kawato, Yoshimi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro
JAEA-Technology 2015-008, 28 Pages, 2015/03
JAEA-Technology-2015-008.pdf:13.63MB
In JAEA, 16,671 drums of intermediate-radioactive bituminized waste products (BWPs) have been stored in asphalt solidification storages. As a way of reduction of uncertainty in assessment of disposal of the BWPs, a processing technique of separation of nitrate salts from the BWP by means of an aqueous leaching method was studied. As elemental techniques for the denitration process, (1) crushing techniques of a BWP and (2) denitration techniques for the crushed BWP by the aqueous leaching method were investigated. In order to promote leaching amounts of nitrates, the BWP was crushed, and the grain size distribution was investigated by sieving. Moreover, leaching behaviors of nitrate, nitrite and elements as radionuclides including in the BWP were investigated.
Nakayama, Takuya; Kawato, Yoshimi; Osugi, Takeshi; Shimazaki, Takejiro; Hanada, Keiji; Suzuki, Shinji; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro
JAEA-Technology 2014-046, 56 Pages, 2015/03
JAEA-Technology-2014-046.pdf:7.61MB
The combustible and flame-retardant radioactive wastes generated as a result of the research activities in Japan Atomic Energy Agency (JAEA) are incinerating to reduce their volume. The incinerated ash is planned to be solidified using cement for disposal. Since the properties of ashes generated in each institute of JAEA are varied with the type of incinerator and the wastes to be incinerated, it is necessary to do fundamental solidification tests in each institute to decide operating conditions of the planning cement solidification facility. It is important to standardize evaluating methods of cement and solidified waste because some characters depend on measuring method. This user's guide have been prepared how to decide the cement solidifying conditions of ash to design the cement solidification facility in JAEA. Requirements on the regulations of solidified radioactive waste have been examined and seven technical criteria, e.g. compressive strength, fluidity, have been selected as characters to be evaluated. Some empirical notes about selection of cement, admixtures, procedure on making a test piece, evaluation of expanding, compressive strength, solubility have been described. The strategy of tests and tips for finding optimized solidification condition has been summarized. Finally the example of optimized conditions satisfied the requirements and some problems to be solved have been described.
Irisawa, Keita; Komatsuzaki, Toshio; Kawato, Yoshimi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro
JAEA-Technology 2014-039, 28 Pages, 2014/12
JAEA-Technology-2014-039.pdf:6.13MB
In JAEA, 13,296 drums of low-radioactivity bituminized waste products (BWPs) have been stored in asphalt solidification storages. In order to effectively utilize the space of the BWP in a repository site, we studied refilling techniques of the BWP from the drum to a box-shaped container. Tentative processes, which we devised, consisted of (1) take-off of BWP from the drum, (2) separation of a post filling part from BWP and (3) filling of BWP to a box-shaped container. Two methods for each process were selected, and work efficiencies of the methods were investigated by using a synthetic BWP.
Nakanishi, Yoshiki; Aoyama, Yoshio; Nonaka, Kazuharu; Sone, Tomoyuki; Nakazawa, Osamu; Tashiro, Kiyoshi
JAEA-Testing 2011-008, 31 Pages, 2012/03
JAEA-Testing-2011-008.pdf:2.8MB
Steam reforming technology has been developed to reduce the volume of liquid uranium waste such as a Tri-n-butyl phosphate adding n-dodecane solvent (TBP/nDD), which is difficult to incinerate. The localized corrosion like pitting corrosion occurred on the inner surface of the gasification chamber of the demonstration scale steam reforming system during the treatment of TBP/nDD. Therefore we conducted the corrosion tests to identify the form of corrosion. It is found that the form of corrosion is crevice corrosion which caused by the residues generated by treatment of TBP/nDD. The cathodic protection system using a galvanic anode was selected as the corrosion protection method of the gasification chamber. The continuous treatment test of TBP/nDD was conducted using the steam reforming system with the cathodic protection system. As a result, the crevice corrosion did not occur during 600 hours continuous treatment of TBP/nDD, and the effectiveness of the protection method was verified.
Nakagawa, Akinori; Sone, Tomoyuki; Sasaki, Toshiki; Nakazawa, Osamu; Tashiro, Kiyoshi
Proceedings of International Waste Management Symposia 2011 (WM2011) (CD-ROM), 7 Pages, 2011/03
Nakagawa, Akinori; Sone, Tomoyuki; Sasaki, Toshiki; Nakazawa, Osamu; Tashiro, Kiyoshi
JAEA-Technology 2010-014, 46 Pages, 2010/06
JAEA-Technology-2010-014.pdf:1.76MB
Steam reforming treatment system was developed for volume reduction of Tri-n-butyl phosphate contaminated with uranium, which is difficult to treat with incineration, due to generation of corrosive compounds, a large amount of secondary waste, etc. This system consists of a steam reforming process in which organic waste is decomposed/gasified in steam atmosphere and a submerged combustion process in which vaporized waste is burned in water and has good features such as high volume reduction rate of waste, low secondary waste generation rate, etc. Results obtained this study were as follows: Volume reduction rate of waste was 99.6%. Uranium entrainment to off-gas was suppressed and the concentration of uranium in waste water was under 0.037mg/L. The concentration of CO and NOx in the off-gas were less than 100ppm and 250ppm respectively. Plugging and corrosion control technologies were developed and it was confirmed that the waste treatment system can run for long periods.
Sudo, Makoto; Takai, Masakazu; Sasaki, Toshiki; Nakazawa, Osamu; Fukumoto, Masahiro
Proceedings of International Waste Management Symposium 2005 (WM 2005), 0 Pages, 2005/03
None
Katsumi, Muto,; Koakutsu, Masayuki; Nakazawa, Osamu; Kato, Hiroshi; Ebashi, Takeshi
Saikuru Kiko Giho, (27), 84, 86, 98 Pages, 2005/00
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