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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
Garcia-Lodeiro, I.*; Lebon, R.*; Machoney, D.*; Zhang, B.*; Irisawa, Keita; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Meguro, Yoshihiro; Kinoshita, Hajime*
Proceedings of 3rd International Symposium on Cement-based Materials for Nuclear Wastes (NUWCEM 2018) (USB Flash Drive), 4 Pages, 2018/11
-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.
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.
Ohara, Yoshiyuki; Naganuma, Masaki; Nohiro, Tetsuya*; Yoshida, Kimikazu*; Makita, Akinori*; Sakate, Mitsuo*; Irisawa, Takumi*; Murashita, Tatsuya*
JAEA-Technology 2012-048, 39 Pages, 2013/03
JAEA-Technology-2012-048.pdf:5.1MB
In Japan Atomic Energy Agency Ningyo-Toge Environmental Engineering Center, exploration for uranium and technical development of uranium refining, conversion and enrichment which are the front end of a nuclear fuel cycle have been performed since 1955. By these research and development, about 15000 radioactive waste (200 liter drum) has occurred by now. The analytical and measurement technique of the amount of uranium which are included in radioactive waste drum were very an inexperienced in those days. Therefore, measurement strict till 2002 was not able to be started. Such a situation as this, we introduced "Q2 low-level-waste drum measuring system" which is a bulk measuring method of the passive ray using a NaI scintillation detector in 2002. As a result, the total amount of uranium in a waste drum was estimated as about 20 tons.
Taniguchi, Takumi; Irisawa, Keita; Ito, Yuzuru; Namiki, Masahiro; Osugi, Takeshi; Abe, Tomohisa; Sato, Junya; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro; et al.
no journal, ,
no abstracts in English
and Cl
Irisawa, Keita; Taniguchi, Takumi; Namiki, Masahiro*; Garca-Lodeiro, I.*; Osugi, Takeshi; Nakazawa, Osamu; Kinoshita, Hajime*
no journal, ,
no abstracts in English
Co -ray on characteristics of phosphate cements synthesized during dehydrationIrisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu
no journal, ,
no abstracts in English
Taniguchi, Takumi; Irisawa, Keita; Namiki, Masahiro*; Nakazawa, Osamu
no journal, ,
no abstracts in English
Garcia-Lodeiro, I.*; Irisawa, Keita; Lebon, R.*; Mahoney, D.*; Zhang, B.*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Meguro, Yoshihiro; Kinoshita, Hajime*
no journal, ,
Irisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu
no journal, ,
no abstracts in English
