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Journal Articles

Effort for management of radioactive waste with unknown quality and amount

Koma, Yoshikazu; Niibori, Yuichi*

Nihon Kikai Gakkai-Shi, 122(1211), p.21 - 23, 2019/10

International Topical Workshop on Fukushima Decommissioning Research was held in March 2019 by the Japan Society of Mechanical Engineers and the Atomic Energy Society of Japan. Result of track for waste management technologies among 5 tracks is outlined.

Journal Articles

Development of a method of safety assessment for geological disposal considering long-term evolution of geological and topographical environment by uplift and erosion

Wakasugi, Keiichiro; Yamaguchi, Masaaki; Koo, Shigeru*; Nagao, Fumiya; Kato, Tomoko; Suzuki, Yuji*; Ebashi, Takeshi; Umeki, Hiroyuki*; Niibori, Yuichi*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 16(1), p.15 - 33, 2017/03

This study provides a method of safety assessment for the geological disposal of HLW to evaluate the effects of uplift and erosion which are widespread phenomena identified on regional and global scales, and are more or less difficult to avoid in Japan. This method enables to deal with different uplift rate and erosion rate, and to evaluate repository depth, the time required for a repository to reach the weathered zone and surface of the ground, and the number of waste packages eroded as a function of time by using a landform evolution model. Based on trial analysis, the result shows that the maximum dose in the Base Case (uplift rate: 0.3 mm/y) is less than the targeted criterion suggested by the international organization even if the repository reaches the ground surface. Furthermore, the diversifying effect on timing the waste packages to reach to weathered zone due to heterogeneity on altitude of bottom of weathered zone reduces one order magnitude of result of the existed dose assessment. The new method is applicable to evaluate safety of geological disposal based on realistic phenomena of uplift and erosion and to quantify a safety margin and robustness of the disposal system.

Journal Articles

Chromatographic separation of nuclear rare metals by highly functional xerogels

Onishi, Takashi; Koyama, Shinichi; Masud, R. S.*; Kawamura, Takuya*; Mimura, Hitoshi*; Niibori, Yuichi*

Nihon Ion Kokan Gakkai-Shi, 25(4), p.220 - 227, 2014/11

no abstracts in English

Journal Articles

The Present situation and future prospects of groundwater colloids studies on the performance assessment of geological disposal of radioactive wastes in Japan

Nagao, Seiya*; Niibori, Yuichi*; Tanaka, Tadao; Sasaki, Takayuki*; Saito, Takumi*; Kirishima, Akira*; Yoshikawa, Hideki; Iijima, Kazuki; Hama, Katsuhiro; Iwatsuki, Teruki; et al.

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 20(1), p.3 - 14, 2013/06

This paper shows a current status of groundwater colloids studies on the performance assessment of geological disposal of radioactive wastes in Japan, and summaries realistic approach of the colloids studies at a substantial research network for Japanese universities and institutes.

Journal Articles

Burning of MOX fuels in LWRs; Fuel history effects on thermal properties of hull and end piece wastes and the repository performance

Hirano, Fumio; Sato, Seichi*; Kozaki, Tamotsu*; Inagaki, Yaohiro*; Iwasaki, Tomohiko*; Oe, Toshiaki*; Kato, Kazuyuki*; Kitayama, Kazumi*; Nagasaki, Shinya*; Niibori, Yuichi*

Journal of Nuclear Science and Technology, 49(3), p.310 - 319, 2012/03

AA2011-0278.pdf:0.56MB

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

The thermal impacts of hull and end piece wastes from the reprocessing of MOX spent fuels burned in LWRs on repository performance were investigated. The heat generation rates in MOX spent fuels and the resulting heat generation rates in hull and end piece wastes change depending on the fuel histories including the burn-up of UO$$_{2}$$ spent fuels, the cooling period before reprocessing, the storage period of fresh MOX fuels. The heat generation rates of hull and end piece wastes from the reprocessing of MOX spent fuels with any of those histories are significantly larger than those from UO$$_{2}$$ spent fuels with burn-ups of 45 GWd/THM. If a temperature below 80$$^{circ}$$C is specified for cement-based materials used in waste packages after disposal, the allowable number of canisters containing compacted hull and end pieces in a package for 45 GWd-MOX needs to be limited to a value of 0.7 to 1.6, which is significantly lower than the value of 4.0 for 45 GWd-UO$$_{2}$$.

Journal Articles

Immobilisation of caesium by zeolites and characterisation of ceramic solid forms

Tomiyama, Shin*; Mimura, Hitoshi*; Niibori, Yuichi*; Yamagishi, Isao; Morita, Yasuji

Proceedings of 11th OECD/NEA Information Exchange Meeting on Actinide and Fission Product Partitioning and Transmutation (Internet), 10 Pages, 2012/00

The immobilization of Cs has been studied by the calcination of the Cs-form of various kinds of mordenites. In this study, the effect of various parameters such as calcining temperature and time, components in mordenites, conditions for cold and hot pressing, on the immobilization of Cs in ceramic products are evaluated by using X-ray diffractometry (XRD), density balance (Archimedes' method), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Results showed that recrystallization to the stable ceramic solid forms of CsAlSi$$_{5}$$O$$_{12}$$ was achieved only in calcination of Synthetic Mordenite-C which contains Ti and Fe as binder. The Cs-form mordenites were pelletized into a disk by cold isostatic pressing and the density of the solid forms increased with calcining temperature and time.

Journal Articles

Radioactive waste engineering and management

Nakayama, Shinichi; Okoshi, Minoru; Shimada, Taro; Tachibana, Mitsuo; Momma, Toshiyuki; Niibori, Yuichi*; Nagasaki, Shinya*; Ahn, J.*

Genshiryoku Kyokasho "Hoshasei Haikibutsu No Kogaku", 235 Pages, 2011/01

This book is designed to provide everyone with an interest in radioactive waste issues, including students and individuals involved in engineering and public administration, with a graduate-level understanding of radioactive wastes from the scientific foundations that support radioactive waste management covering radioactive waste generation including decommissioning of nuclear facilities, treatment, disposal, clearance and their safety assessment. This book is the one volume of the English translation of the text series "An Advanced Course in Nuclear Engineering" lectured in the University of Tokyo.

Journal Articles

Selective separation and recovery of Mo(VI) by hybrid microcapsules containing organic extractants

Ikeda, Kaoru*; Wu, Y.*; Mimura, Hitoshi*; Niibori, Yuichi*; Wakui, Yoshito*; Osaka, Masahiko; Koyama, Shinichi; Onishi, Takashi

36th Annual Radioactive Waste Management Symposium 2010 (WM 2010), Vol.2, p.1566 - 1576, 2010/00

In order to separate and selectively recover molybdenum those content in high level vitrified waste is limited, two kinds of hybrid microcapsule containing organic extractants LIX63 that is effective for the extraction of Mo(VI) are synthesis, characterized and used for adsorption experiment with real radioactive liquid waste. In adsorption experiment with cold solution, uptake attained equilibrium within 5 h, the uptake percentage was above 99% within 3 h. In adsorption experiment with real radioactive liquid waste, the uptake percentage was 99.9%.

Journal Articles

Selective separation of heat-generating nuclide by silica gels loaded with ammonium molybdophosphate; Adv.-ORIENT cycle development

Endo, Yusuke*; Wu, Y.*; Mimura, Hitoshi*; Niibori, Yuichi*; Koyama, Shinichi; Onishi, Takashi; Obayashi, Hiroshi; Yamagishi, Isao; Ozawa, Masaki

Proceedings of International Conference on Advanced Nuclear Fuel Cycle; Sustainable Options & Industrial Perspectives (Global 2009) (CD-ROM), p.1007 - 1015, 2009/09

The separation of heat-generating nuclide (Cs) from high-level liquid wastes is important in relation to the waste volume reduction. The present paper deals with the preparation of Cs-selective ion-exchangers (silica gels loaded with ammonium molybdophosphate, AMP-SG), uptake properties and characterization. The AMP-SG exhibited large distribution coefficient above 10$$^{3}$$ cm$$^{3}$$/g for Cs even in the 2-3 M HNO$$_{3}$$ solution. The uptake isotherm of Cs followed a Langmuir-type equation, and the maximum Cs capacity was 0.24 mmol/g. The breakthrough curves of Cs had S-shaped profile, and the 94% of Cs adsorbed on the AMP-SG column was eluted with 5 M NH$$_{4}$$NO$$_{3}$$ - 1 M HNO$$_{3}$$ solution. The eluent containing ammonium salt is suitable for both the recovery of Cs and the regeneration of AMP-SG. The precise chromatographic separation of Cs and Rb was also accomplished by using mixed solutions of NH$$_{4}$$NO$$_{3}$$ and HNO$$_{3}$$.

JAEA Reports

None

Tochiyama, Osamu*; Niibori, Yuichi*; *; *; Yui, Mikazu; Shibata, Masahiro; *

JNC TY8400 2002-014, 129 Pages, 2002/05

JNC-TY8400-2002-014.pdf:2.35MB

None

Journal Articles

Concept and applicability of sorption distribution coefficient in the radionuclide transport model

*; Takasu, Aki*; *; Kimura, Hideo; Sato, Seichi*; Nagasaki, Shinya*; Nakayama, Shinichi; Niibori, Yuichi*; *; Mitsugashira, Toshiaki*; et al.

Genshiryoku Bakkuendo Kenkyu, 5(1), p.3 - 19, 1998/08

no abstracts in English

Oral presentation

Identification of the water-conducting features using fluid electric conductivity logging

Takeuchi, Shinji; Matsuoka, Kiyoyuki*; Niibori, Yuichi*

no journal, , 

Fluid Electric Conductivity (FEC) Logging was performed in 1000m borehole, named DH-15, located near to the Mizunami Underground Research Laboratory Site in Mizunami, central Japan. The purpose of this study is to detect water-conducting features of fractured rock in the deep borehole and to evaluate hydraulic properties such as transmissivity and electric conductivity (salinity). 29 water-conducting features (WCFs) were identified by the logging with changing pumping rate three times and evaluated hydraulic properties with numerical simulation based on the advection-diffusion equation. We propose this method would be useful for evaluating hydraulic properties for WCFs in deep underground effectively.

Oral presentation

Re-interpretation of the fluid electric conductivity measurements carried out in the MIZ-1 borehole at the Mizunami Underground Research Laboratory project

Bruines, P.*; Ando, Kenichi*; Niibori, Yuichi*; Matsuoka, Kiyoyuki*; Takeuchi, Shinji

no journal, , 

Fluid electric conductivity (FEC) measurements have been carried out in the 1,350 m long MIZ-1 borehole followed by the modeling of FEC curve with newly developed finite difference code and obtaining tranmissivity in each feed point from FEC logging. The obtained results are comparable to those obtained by hydraulic testing. The method can be valuable to help in the selection of locations for more detailed hydraulic tests. Under certain circumstances the method can be used as a low cost alternative to hydraulic testing.

Oral presentation

Deposition behavior of soluble and colloidal silicic acid on silica mineral in alkali-front

Kokubun, Hiroshi*; Niibori, Yuichi*; Mimura, Hitoshi*; Iijima, Kazuki

no journal, , 

Deposition behavior of silicic acid on silica mineral was investigated with various initial oversaturation concentration of silicic acid and amount of silica mineral. As a results, soluble silica dominates deposition behavior of silicic acid when surface area of solid phase in the experimental solution is higher than significant threshold value in 3 mM oversaturation concentration of silicic acid.

Oral presentation

Selective separation of Cs by ammonium molybdophosphate loaded silica gels

Endo, Yusuke*; Wu, Y.*; Mimura, Hitoshi*; Niibori, Yuichi*; Yamagishi, Isao; Koyama, Shinichi; Onishi, Takashi; Ozawa, Masaki

no journal, , 

no abstracts in English

Oral presentation

Adsorption properties of oxoanions for hybrid microcapsules enclosing extractant

Sugimori, Toshiaki*; Wu, Y.*; Mimura, Hitoshi*; Niibori, Yuichi*; Sasaki, Yuji

no journal, , 

no abstracts in English

Oral presentation

Immobilization of cesium using zeolites

Tomiyama, Shin*; Mimura, Hitoshi*; Niibori, Yuichi*; Yamagishi, Isao; Morita, Yasuji

no journal, , 

Immobilization of cesium separated from high-level liquid waste was studied by using a mordenite, which adsorbs cesium selectively. Ceramic samples were prepared by pressing and sintering the mordenite loaded with cesium. Ceramics of the higher density were obtained by sintering the pressed mordenites of the smaller particle size. The density of the sample sintered with pressing, which is called hot-pressing, was higher than that of the sample sintered after pressing by a facor of 1.5.

Oral presentation

Selective separation of Cs by hybrid microcapsules containing AWP

Murao, Ayako*; Mimura, Hitoshi*; Niibori, Yuichi*; Yamagishi, Isao; Ozawa, Masaki

no journal, , 

Fine crystals of ammonium tungstophosphate (AWP) exchanger having high selectivity toward Cs were encapsulated in the biopolymer matrices (calcium alginate, CaALG). The uptake of Cs in the AWP microcapsule was 80.2 and 80.0% for simulated high-level liquid waste solutions of nitric acid and hydrochloric acid, respectively. The biopolymer matrices, however, adsorbed slightly Ru, Zr, Mo, etc.

Oral presentation

Immobilization of cesium by zeolites and characterization of ceramic solid forms

Tomiyama, Shin*; Mimura, Hitoshi*; Niibori, Yuichi*; Yamagishi, Isao; Morita, Yasuji

no journal, , 

The immobilization of Cs has been studied by the calcination of the Cs-form of various kinds of mordenites. In this study, the effect of various parameters such as calcining temperature and time, components in mordenites, conditions for cold and hot pressing, on the immobilization of Cs in ceramic products are evaluated by using X-ray diffractometry (XRD), density balance (Archimedes' method), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Results showed that re-crystallization to the stable ceramic solid forms of CsAlSi$$_{5}$$O$$_{12}$$ was achieved only in calcination of Synthetic Mordenite-C which contains Ti and Fe as binder. The Cs-form mordenites were pelletized into a disk by cold isostatic pressing.

Oral presentation

Immobilization of cesium by zeolites and characterization of solid forms

Tomiyama, Shin*; Mimura, Hitoshi*; Niibori, Yuichi*; Yamagishi, Isao; Morita, Yasuji

no journal, , 

The immobilization of Cs has been studied by the calcination of the Cs-form of various kinds of mordenites. In this study, the effect of various parameters such as calcining temperature and time, components in mordenites, conditions for cold and hot pressing, on the immobilization of Cs in ceramic products are evaluated by using X-ray diffractometry (XRD), density balance (Archimedes' method), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Results showed that re-crystallization to the stable ceramic solid forms of CsAlSi$$_{5}$$O$$_{12}$$ was achieved only in calcination of Synthetic Mordenite-C which contains Ti and Fe as binder. The Cs-form mordenites were pelletized into a disk by cold isostatic pressing.

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