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Ito, Kengo*; Takahashi, Shin*; Kato, Chizu*; Fukutani, Satoshi*; Matsumura, Tatsuro; Fujii, Toshiyuki*
Journal of Radioanalytical and Nuclear Chemistry, 334, p.2467 - 2475, 2025/02
Times Cited Count：0 Percentile：0.00(Chemistry, Analytical)In this study, the solvent extraction behavior of tin (Sn), specifically 
Sn, from high-level radioactive waste was evaluated using six different extractants in a HNO
system. Among the tested extractants, N,N-Didodecyl-2-hydroxyacetoamide (HAA) exhibited higher efficiency, still not sufficient for industrial implementation. In systems where HCl was added to HNO, both tributyl phosphate (TBP) and N,N,N,N'-tetra-2-ethylhexyl diglycolamide (TEHDGA) achieved D
values greater than 1 at 
1 M HCl. However, due to practical challenges in industrial applications, HAA extraction in HNO systems, particularly at low Sn concentrations (0.0008 M), may provide a more effective solution for Sn recovery.
Ito, Kengo*; Morita, Misaki*; Araki, Yuta*; Kato, Chizu*; Fukutani, Satoshi*; Matsumura, Tatsuro; Fujii, Toshiyuki*
Solvent Extraction Research and Development, Japan, 32(1), p.53 - 62, 2025/00
Rhodium (Rh) and Palladium (Pd) in high-level radioactive waste are primarily fission products. This Study focused on understanding the extraction behavior of these platinum group elements (PGEs) using the novel extractants 
-hexaoctylnitriloacetamide (HONTA) and alkyl diamideamine (ADAAM). Both extractants showed affinity for Pd, with distribution coefficients significantly exceeding 1, demonstrating their effectiveness in Pd separation. In contrast, the distribution coefficients for Rh were consistently below 10 
, indicating low extraction efficiency from nitric acid. However, by leveraging the salting-out effect with calcium nitrate hydrate, a distribution coefficient of 
570 for Rh was achieved using HONTA. To overcome the difficult back-extraction of PGEs with HONTA, experiments were conducted using HEDTA and thiourea. Back-extraction with HEDTA in high-concentration nitric acid (2M) resulted in 90% extraction of Pd, while thiourea-based back-extraction with nitric acid yielded over 40% extraction for Rh, with the maximum of 62.7% achieved using hydrochloric acid.
Ito, Kengo*; Kawakami, Takahiro*; Kato, Chizu*; Fukutani, Satoshi*; Matsumura, Tatsuro; Fujii, Toshiyuki*
Journal of Radioanalytical and Nuclear Chemistry, 333(10), p.5183 - 5189, 2024/10
Times Cited Count：1 Percentile：51.66(Chemistry, Analytical)Solvent extraction behaviors of Se (VI) from nitric acid solutions were investigated with multiple extractants used for uranium, plutonium, minor actinides, and rare earthelements separation processes from high-level liquid waste. During the processes, Se remained in the residual aqueous solutions, as all extractants showed distributionratios 
1. In contrast, Se showed distribution ratios 1 with 
-phenylenediamine in dilute nitric acid ( 2 M HNO), octanol as the organic phase, and concentrated nitric acid (8 M HNO) for back extraction, suggesting a potential new single separation process and recovery of Se.
Yoshida, Naoki; Ono, Takuya; Amano, Yuki; Yoshida, Ryoichiro; Abe, Hitoshi; Yamane, Yuichi
Nuclear Technology, 210(10), p.1999 - 2007, 2024/10
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)A malfunction of the cooling system of high-level liquid waste (HLLW) and failure of countermeasures may lead to the "evaporation to dryness due to the loss of cooling functions" (EDLCF) of HLLW. In the EDLCF, ruthenium (Ru) can be released at a greater fraction to initial amount than other elements in HLLW by forming gaseous Ru. It is important to identify the chemical form of the released gaseous Ru to achieve a comprehensive understanding of the events impacting the source term assessment of Ru in this accident, such as particle formation, gas absorption and deposition on migration pathways. In this study, we observed the ultraviolet/visible spectroscopy of the off-gas generated during the heating of an HLLW simulant. Employing a program that allows the separation and quantification of known components within the spectrum (ruthenium tetroxide (RuO
), nitrogen dioxide, and nitric acid), we attempted to analyze the composition of gaseous Ru within the generated off-gas. Our findings reveal RuO as the main component of the gaseous Ru in off-gas after comparing the total amount of released Ru and the RuO released amount obtained via spectroscopic analysis.
Ban, Yasutoshi; Suzuki, Hideya*; Hotoku, Shinobu; Tsubata, Yasuhiro
Proceedings of International Conference on Nuclear Fuel Cycle (GLOBAL2024) (Internet), 4 Pages, 2024/10
A continuous counter-current extraction experiment was performed by mixer-settler extractors to recover minor actinides (MA; Am and Cm) from high-level liquid waste. Using hexaoctyl nitrilotriacetamide (HONTA) as an extractant, 0.17 g of MA was recovered in a MA fraction.
Yoshida, Naoki; Ono, Takuya; Yoshida, Ryoichiro; Amano, Yuki; Abe, Hitoshi
Journal of Nuclear Science and Technology, 57(11), p.1256 - 1264, 2020/11
Times Cited Count：11 Percentile：71.69(Nuclear Science & Technology)Emphasis has been placed on the behavior of ruthenium (Ru) in the evaporation to dryness accident due to the loss of cooling functions (EDLCF) of high-level liquid waste in fuel reprocessing plants. It is because Ru would form volatile compounds such as ruthenium tetroxide (RuO) and could be released into the environment with other coexisting gasses such as nitric acid (HNO), water (H
O). To contribute to the safety evaluation of this accident, we experimentally evaluated the decomposition and chemical change behavior of the gaseous RuO (RuO(g)) under the various atmospheric conditions: temperature and composition of coexisting gasses. As a result, the behavior of the RuO(g) was diverse depending on the atmospheric conditions. In the experiments with the dry air or HO vapor, decomposition of RuO(g) was observed. In the experiment with the mixed gas which containing HNO, almost no decomposition of the RuO(g) was observed, and chemical form of the RuO(g) was retained.
Sasaki, Yuji
Kagaku Kogaku, 84(9), p.425 - 427, 2020/09
The reduction of waste volume and hazardous substance though separation methods concerning atomic energy must be requested. As disposal methods or temporary measures, geological disposal, transmutation and interim storage are proposed. In order to perform effectively the disposal methods, the development of separation method of aimed elements is indispensable. Here, the new separation method of U and Pu from spent nuclear fuel and minor actinide separation and fission products from high level radioactive waste are explained.
Morita, Yasuji; Tsubata, Yasuhiro
JAEA-Data/Code 2019-015, 45 Pages, 2020/01
JAEA-Data-Code-2019-015.pdf:2.09MB
Decay heat from radioactive elements in high-level liquid waste (HLLW) and separated solutions in partitioning process was evaluated as a basic data for safety assessment of partitioning process. In the evaluation of HLLW from spent UO fuel burned-up to 45 GWd/t in light water reactor, decay heat value from fission products decreased as the cooling period become longer but heat from actinides, Am and Cm, was almost constant until 50-year cooling. Decay heat density in solutions of Am, Cm and rare earth elements and of Am and Cm without concentration for volume reduction does not exceed the heat density of HLLW, but the concentration should be required to minimize the scale of the partitioning process. Separated solution of Am and Cm must be concentrated to convert the two elements to a solid state to make fuel for transmutation, and the decay heat density of the concentrated solution of Am and Cm is 10 times higher compared with the Pu solution of same element concentration. Higher burn-up UO fuel and MOX fuel in light water reactor and minor-actinide-recycled MOX fuel in fast reactor were also considered and the evaluated decay heat was compared among the spent fuels.
-ray irradiationAmbai, Hiromu; Nishizuka, Yusuke*; Sano, Yuichi; Uchida, Naoki; Iijima, Shizuka
QST-M-2; QST Takasaki Annual Report 2015, P. 90, 2017/03
The spent fuel stored in the storage pools at the Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Company Holdings, Inc. is exposed with the environment containing seawater components, owing to the injection of seawater into the storage pools. Therefore, during reprocessing, it is expected that the spent fuel will be contaminated with seawater components, and the influence of seawater on reprocessing needs to be investigated. We conducted the corrosion tests of the HAW storage tanks under -ray irradiation, and revealed that no significant effect of seawater components was emerged.
Yoshida, Kazuo
Nihon Genshiryoku Gakkai Wabun Rombunshi, 14(1), p.40 - 50, 2015/02
An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents to occur caused by the loss of cooling function at a fuel reprocessing plant. In this case, some amount of non-volatiles fission products (FPs) will be transferred in form of mists to the vapor phase in the tank, and could be released to the environment. Therefore, the quantitative estimation of transfer rate is one of the key issues in the assessment of the accident consequence. To resolve this issue, a mechanistic correlation of entrainment rate with upward vapor velocity has been developed based on the data obtained from the experiments using simulated and actual HLLW.
Tachimori, Shoichi; Suzuki, Shinichi; Sasaki, Yuji; Apichaibukol, A.
Solvent Extraction and Ion Exchange, 21(5), p.707 - 715, 2003/09
Times Cited Count：49 Percentile：75.57(Chemistry, Multidisciplinary)no abstracts in English
Sasaki, Yuji; Suzuki, Shinichi; Tachimori, Shoichi*; Kimura, Takaumi
Proceedings of GLOBAL2003 Atoms for Prosperity; Updating Eisenhower's Global Vision for Nuclear Energy (CD-ROM), 4 Pages, 2003/00
no abstracts in English
Morita, Yasuji; Tachimori, Shoichi; Koma, Yoshikazu*; Aoshima, Atsushi*
JAERI-Research 2002-017, 20 Pages, 2002/08
JAERI-Research-2002-017.pdf:1.32MB
The present report describes the results of a joint study between Japan Nuclear Cycle Development Institute (JNC) and Japan Atomic Energy Research Institute (JAERI) on actinide separation process from high-level liquid waste. The purpose of the joint study is to point out common subjects in process development by an overall evaluation of each actinide separation process: TRUEX/SETFICS Process studied in JNC and DIDPA Extraction Process studied in JAERI. The result of the evaluation showed that both processes have common subjects to be studied in sub-processes such as treatment step for spent solvent or DTPA waste solution and solvent washing step for recycling, although the main process is different from each other. It is necessary to develop the sub-processes and to test the whole process including the sub-processes. Two essential requirements: the cost reduction and the minimization of secondary wastes, are very important in future research and development for more rational and effective actinide separation process.
Department of Fuel Cycle Safety Research
JAERI-Review 2001-038, 600 Pages, 2001/12
JAERI-Review-2001-038.pdf:19.64MB
no abstracts in English
Morita, Yasuji; Sasaki, Yuji; Tachimori, Shoichi
Proceedings of International Conference on Back-End of the Fuel Cycle: From Research to Solutions (GLOBAL 2001) (CD-ROM), 7 Pages, 2001/09
no abstracts in English
Morita, Yasuji; Yamaguchi, Isoo; Fujiwara, Takeshi; Mizoguchi, Kenichi*; Kubota, Masumitsu*
JAERI-Research 2000-024, 55 Pages, 2000/06
JAERI-Research-2000-024.pdf:2.24MB
no abstracts in English
Morita, Yasuji; Yamaguchi, Isoo; ; ; Kubota, Masumitsu
Proc. of the Int. Conf. on Future Nuclear Systems (GLOBAL'99)(CD-ROM), 8 Pages, 1999/00
no abstracts in English
L.Donnet*; Morita, Yasuji; Yamagishi, Isao; Kubota, Masumitsu
JAERI-Research 98-058, 63 Pages, 1998/10
JAERI-Research-98-058.pdf:2.19MB
no abstracts in English
Morita, Yasuji; Mizoguchi, Kenichi*; Yamaguchi, Isoo; ; Kubota, Masumitsu
JAERI-Research 98-046, 18 Pages, 1998/08
JAERI-Research-98-046.pdf:1.01MB
no abstracts in English
Mizoguchi, Kenichi*; Yamaguchi, Isoo; Morita, Yasuji; Yamagishi, Isao; ; Kubota, Masumitsu
JAERI-Research 98-026, 29 Pages, 1998/05
JAERI-Research-98-026.pdf:1.45MB
no abstracts in English
