Goto, Takahiro*; Mitsui, Seiichiro; Takase, Hiroyasu*; Kurosawa, Susumu*; Inagaki, Manabu*; Shibata, Masahiro; Ishiguro, Katsuhiko*
MRS Advances (Internet), 1(63-64), p.4239 - 4245, 2016/00
NUMO and JAEA have conducted a joint research since FY2011, which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation stage for deep geological disposal of radioactive waste. As a part of this joint research, we have been developing glass dissolution models which consider various processes in EBS, such as precipitation of Fe-silicates associated with iron overpack corrosion, and Si transport through corrosion products in the cracked overpack. The objectives of the modeling work are to evaluate relative importance of relevant processes and to identify further R&D issues towards development of a convincing safety case. Sensitivity analyses suggested that predicted glass dissolution time ranges from 110 to 110 years or more due to uncertainties in the current understanding of the key processes, namely precipitation of Fe-silicates and transport characteristics of the altered glass layer.
Yuguchi, Takashi; Sasao, Eiji; Ishibashi, Masayuki; Nishiyama, Tadao*
American Mineralogist, 100(5-6), p.1134 - 1152, 2015/05
This paper describes the biotite chloritization process with a focus on mass transfer in the Toki granitic pluton, Central Japan, and also depicts the temporal variations in chemical characteristics of hydrothermal fluid associated with chloritization during the sub-solidus cooling of the pluton. Singular value decomposition (SVD) analysis results in chloritization reaction equations for eight mineral assemblages, leading to the quantitative assessment of mass transfer between the reactant and product minerals, and inflow and outflow of components through the hydrothermal fluid. The matrices for SVD analysis consist of arbitrary combinations of molar volume and closure component in the reactant and product minerals. The eight reactions represent the temporal variations of chemical characteristics of the hydrothermal fluid associated with chloritization: the progress of chloritization results in gradual increase of silicon, potassium and chlorine and gradual decrease of calcium and sodium in the hydrothermal fluid with temperature decrease. The biotite chloritization involves two essential formation processes: Formation Process 1, small volume decrease from biotite to chlorite and large inflow of metallic ions from the hydrothermal fluid, and Formation Process 2, large volume decrease and large outflow of metallic ions into hydrothermal fluid. Chlorite produced during Formation Process 1 dominates over that of Formation Process 2, resulting in the gradual decrease of metallic components in the hydrothermal fluid with chloritization progress. The combination of continuous reactions based on compositional variations in chlorite together with corresponding continuous Al variations gives an indication of the temporal variations in rates of decreasing and increasing concentration of chemical components in the hydrothermal fluid associated with chloritization.
Yamaguchi, Tetsuji; Sakamoto, Yoshifumi; Iida, Yoshihisa; Negishi, Kumi; Taki, Hiroshi; Akai, Masanobu; Jinno, Fumika; Kimura, Yuichiro; Ueda, Masato; Tanaka, Tadao; et al.
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10
no abstracts in English
Tanaka, Tadao; Sakamoto, Yoshifumi; Yamaguchi, Tetsuji; Takazawa, Mayumi; Akai, Masanobu; Negishi, Kumi; Iida, Yoshihisa; Nakayama, Shinichi
JAERI-Conf 2005-007, p.105 - 110, 2005/08
Highly alkaline environments induced by cementitious materials in radioactive waste repositories are likely to dissolve and to alter montmorillonite, the main constituent of bentonite buffer materials. For the prediction of the long-term variations in permeability of compacted sand-bentonite mixtures, long-term alteration of bentonite should be quantified based on information accumulated by using the compacted or powdered bentonite materials, with batch experiments or column experiments. In this study, we summarize distinctive information obtained from various experimental systems, and propose functional and effective integration of experimental approaches to prediction of bentonite alteration.
Takazawa, Mayumi; Negishi, Kumi; Sakamoto, Yoshifumi; Akai, Masanobu; Yamaguchi, Tetsuji; Iida, Yoshihisa; Tanaka, Tadao; Nakayama, Shinichi
JAERI-Conf 2005-007, p.236 - 241, 2005/08
no abstracts in English
Takazawa, Mayumi; Yamaguchi, Tetsuji; Sakamoto, Yoshifumi; Akai, Masanobu; Tanaka, Tadao; Nakayama, Shinichi
NUMO-TR-04-05, p.A3_59 - A3_62, 2004/10
no abstracts in English
*; Mihara, Morihiro;
JNC-TN8430 2001-007, 56 Pages, 2002/01
In the geological disposal concept of radioactive wastes, a kind of clay with sorption ability and low permeability, called bentonite, is envisaged as an engineered barrier system in the geological repository. Also, the cemetitious material is envisaged as the backfill material in the vaults and the structure material of the vaults. The groundwater in contact with the cementitious material will promote hyperalkaline conditions in the repository environment and these conditions will affect the performance of the bentonite. Therefore, it is necessary to investigate the interaction between the cementitious material and the bentonite for the evaluation of long term stability of the disposal system. In this study, for the identification and the investigation of the secondary minerals, the batch immersion experiments of the powder bentonite were carried out using synthetic cement leachates (pH=7, 12.5, 14) at 200C. As the results, it was confirmed that Na as exchangeable cations in the bentonite can exchange relatively easily with Ca in the solution from the experiment results. And the ratio of cation exchange was estimated to be about 25% based on the amount of exchangeable cations Ca between layers. Furthermore, it was concretely shown that the generation of analcime might be affected by the Na concentration from results of the solution analyses and a stability analysis of analcime using the chemical equilibrium model, in addition to the pH in the solution.
Ito, Akira; Kawakami, Susumu; Yui, Mikazu
JNC-TN8400 2001-028, 38 Pages, 2002/01
In a repository for high-level radioactive waste, coupled thermo -hydro -mechanical and chemical (THMC) processes will ocurr, involving the interactive processes between radioactive decay heat from the vitrified waste, infiltration of groundwater, swelling pressure generation and chemical evolution of the buffer material and porewater chemistry. In this program, numerical experiment system for the coupled THMC processes will be developed in order to predict the long-term performance of the near-field (engineered barrier and host rock) for various geological environments. The simulation code development has been started in FY 2001 and three development steps are planned, because (1)development will be continued for some years, (2)feasibility of numerical experiment have to be confirmed by using existing tools. This report presents the following items of the simulation code development for the coupled THMC processes. (1)First step of the simulation code development (2)Mass transport passways in compacted bentonite (3)Parallelization of the simulation code
Fukumoto, Masahiro; Nishikawa, Yoshiaki*
JNC-TN8400 2001-017, 355 Pages, 2001/03
The alkali hydrolysis experiments which seem to be important from the view point of the alteration mechanism using the following seven organic materials was performed as a part of the evaluation of the influence on the disposal of the organic materials contained in the TRU wastes. As a result of the alkali hydrolysis experiments (90C and 91d), each organic materials became those of lower molecular weight. The degradation products were able to be detected in the solution. The organic materials seem to be degraded to the organic matters which were confirmed in this study in a long term of disposal. The degradation products were shown below. Therefore, the evaluation of the influence on the migration of radionuclides by degradation products becomes important in the future. (1)Cement additives of Naphthalenesulfonic acid and Ligninsulfonic acid ( Naphthalenedisulfonic acid etc.) (2)Cement additives of polycarboxylic acid ( Oligomer of distal methoxypoly ethylene glycol.) (3)Ethylenediamine-N,N,N',N'-tetraacetic acid disodium salt ( Acetic acid desorped and cyclized organic matters from EDTA.) (4)Tributyl phosphate ( Dibutyl phthalate, n-butanol) (5)Poly vinyl acetate ( Acetic acid) (6)Nylon66 ( Adipic acid, Hexamethylenediamine) (7)Cured epoxy resin ( Glycerol poly glycidyl ether, Carboxylic acid)
JNC-TN8400 2001-008, 36 Pages, 2001/03
Research on geologic disposal of high-level radioactive waste(HLW) has been underway in many countries. Bentonite exhibiting a low permeability, high swelling property and high sorption capacity for many radioelements is proposed as a buffer material in many countlies. Recently, cementitious materials are considered as candidate matelials for the geologic disposal of high-level radioactive waste. As the pH and the Ca, Na, K contents of hyperalkaline pore water from the cementitious materials are high, this hyperalkaline pore water would alter the buffer material. The main aim of this study is to investigate the effect of alkaline pore water into the bentonite. Used materials are montmorillonite, albite and quartz composing bentonite. These minerals mixed in a constant ratio (1:1wt%) made to react to distilled water and the alkali solutions (pH11-13). These studies have been conducted at temperatures of 50 - 150C and run times of 10 - 200 day. XRD(X-ray powder diffraction) and SEM (Scanning Electron Microscopy) analyses were applied to studying the structure and quantitative data of each sample. From the result of this study, the main formed mineral of this experiment was analcime, which showed the tendency with a large amount of generation at a higher pH and temperature. Quantitative data of this study was conducted by X-ray powder diffraction method. THe order of the amount of the second analcime in each experiment is shown in the following. Montmorillonite and albite mixing test Montmorillonite test Montmorillonite and quartz mixing test Activation energies (E) using the quantitative data of each test are shown in the following. (1)Montmorillonite test : 54.9kJ/mol (2)Montmorillonite and albite mixing test : 51.9kJ/mol (3)Montmorillonite and quartz mixing test : 59.6kJ/mol
*; *; *; *; Hasegawa, Makoto;
JNC-TY9400 2000-007, 50 Pages, 2000/03
no abstracts in English
Iriya, Keishiro*; *; Fujita, Hideki*; Kubo, Hiroshi*
JNC-TJ8400 2000-034, 212 Pages, 2000/02
Cementious materials and highly compacted bentnite are expectable candidates as materials of TRU waste repositories. It was pointed out that Bentonite might be changed to Zeolite and surrounding rock might be altered by high alkalinity water flow, since cement hydrate leached to pore water of cement and it was changed to alkaline. Transportation of radio-nuclides might be accelerated by organic materials, such as super plasticizer, and nitlate which is contained in nuclear wastes. It was concluded by previous studies that rock and bentonite is stable in alkaline water which pH is less than 10.5. The new type of low alkalinity cement with high silica fume and fly ash content which could keep pH below 11.0 was developed and its performance has been assessed. However since Zeolitation and ilitation were reported upon deterioration of bentonite bated in certain condition, it should be assessed by long term experiment. Since Capacity of keeping integrity of bentonite hasn't been directly checked by experiments upon the developed new type of low alkalinity cement it should be done. Although amount of leaching organic was quantitatively and experimentally assessed at an early age, effect of changing of amount and shape hasn't assessed in leaching of radio nuclides. Although it is pointed out that deterioration of cementitious materials isn't accelerated by condensed nitrate solution at early period after closure, it is considered that it might be accelerated corresponding to chemical composition in case of decrement of concentration of nitrate. In this study, deterioration of materials will be assessed in detail in order to feed back the results to assessment of transportation of radio nuclides. Long term deterioration of bentonite by leaching water of cement will be experimentally assessed, and deteriorating test of bentonite will be carried out by leaching water of low alkalinity cement. Amount of organic and component of it will be measured. Furthermore ...
Iriya, Keishiro*; *; Kubo, Hiroshi*; Fujita, Hideki*
JNC-TJ8400 2000-033, 95 Pages, 2000/02
Cementious materials and highly compacted bentnite are expectable candidates as materials of TRU waste repositories. It was pointed out that Bentonite might be changed to Zeolite and surrounding rock might be altered by high alkalinity water flow, since cement hydrate leached to pore water of cement and it was changed to alkaline. Transportation of radio-nuclides might be accelerated by organic materials, such as super plasticizer, and nitrate which is contained in nuclear wastes. It was concluded by previous studies that rock and bentonite is stable in alkaline water which pH is less than 10.5. The new type of low alkalinity cement with high silica fume and fly ash content which could keep pH below 11.0 was developed and its performance has been assessed. However since Zeolitation and ilitation were reported upon deterioration of bentonite bated in certain condition, it should be assessed by long term experiment. Since Capacity of keeping integrity of bentonite hasn't been directly checked by experiments upon the developed new type of low alkalinity cement it should be done. Although amount of leaching organic was quantitatively and experimentally assessed at an early age, effect of changing of amount and shape hasn't assessed in leaching of radio nuclides. Although it is pointed out that deterioration of cementitious materials isn't accelerated by condensed nitrate solution at early period after closure, it is considered that it might be accelerated corresponding to chemical composition in case of decrement of concentration of nitrate. In this study, deterioration of materials will be assessed in detail in order to feed back the results to assessment of transportation of radio nuclides. Long term deterioration of bentonite by leaching water of cement will be experimentally assessed, and deteriorating test of bentonite will be carried out by leaching water of low alkalinity cement. Amount of organic and component of it will be measured. Furthermore ...
Ijiri, Yuji; ;
JNC-TN8400 99-091, 69 Pages, 1999/11
It is crucial for the performance assessment of geosphere to evaluate the characteristics of fractures that can be dominant radionuclide migration pathways from a repository to biosphere. This report summarizes the charactelistics of fractures obtained from broad literature surveys and the fields surveys at the Kamaishi mine in northern Japan and at outcrops and galleries throughout the country. The characteristics of fractures described in this report are fracture orientation, fracture shape, fracture frequency, fracture distribution in space, transmissivity of fracture, fracture aperture, fracture fillings, alteration halo along fracture, flow-wetted surface area in fracture, and the correlation among these characteristics. Since granitic rock is considered the archetype fractured media, a large amount of fracture data is available in literature. In addition, granitic rock has been treated as a potential host rock in many overseas programs, and has JNC performed a number of field observations and experiments in granodiorite at the Kamaishi mine. Therefore, the characteristics of fractures in granitic rock are qualitatively and quantitatively clarified to some extent in this report, while the characteristics of fractures in another rock types are not clarified.
JNC-TN8400 99-061, 9 Pages, 1999/10
The porosities and dry densities for rock samples sampled from a fractured zone (fracture type C: composed of intact ganodiorite, altered ganodiorite and fracture fillings) at the Kamaishi mine were obtained by a water saturation (intrusion) method as input parameters for nuclide migration analysis in performance assessment of the geological disposal of high-level radioactive waste. Consequently, the average porosity, 8.60.43% was higher than those of fracture fillings, altered garnodiorite and intact ganodiorite composing fracture type B with a single fracture taken from the Kamaishi mine so far. While, the average dry density, 2.430.0089 Mgm, was lower than those of rocks composing the fracture type B. Based on this, it is predicted that radionuclides are the easiest to migrate in the fracture zone.
Onuki, Toshihiko; Kozai, Naofumi; Isobe, Hiroshi; Murakami, Takashi*; Yamamoto, Shunya; Narumi, Kazumasa; Naramoto, Hiroshi
Radiochimica Acta, 86(3-4), p.161 - 165, 1999/00
no abstracts in English
; Kubota, Mitsuru*; *; *
JNC-TN8430 98-001, 12 Pages, 1998/11
Leaching experiments were performed with simulated nuclear waste glasses in silica saturated water at 90C for periods of 28 days in order to clarify the alteration mechanism of waste glass under silica saturation. After leaching experiments, the depth profiles of some elements of glass surfaces were measured by ERDA and ESCA. Depth profiles of H and soluble elements, such as B and Na, for the simulated nuclear waste glass after leaching experiments demonstrated the formation of glass hydration layer and the depletion of soluble elements in the glass hydration layer. The results suggest that alteration of nuclear waste glass under silica saturation is attributed to glass hydration and the leaching behaviour of soluble elements depends on the growth of the glass hydration layer.
PNC-TJ1626 98-001, 123 Pages, 1998/03
; Onuki, Toshihiko; Isobe, Hiroshi; Yanase, Nobuyuki; Sekine, Keiichi; *; *
Journal of Contaminant Hydrology, 35, p.191 - 199, 1998/00
no abstracts in English
PNC-TN8420 97-013, 24 Pages, 1997/10