Benbow, S. J.*; Kawama, Daisuke*; Takase, Hiroyasu*; Shimizu, Hiroyuki*; Oda, Chie; Hirano, Fumio; Takayama, Yusuke; Mihara, Morihiro; Honda, Akira
Crystals (Internet), 10(9), p.767_1 - 767_33, 2020/09
Details are presented of the development of a coupled modeling simulator for assessing the evolution in the near-field of a geological repository for radioactive waste disposal where concrete is used as a backfill. The simulator uses OpenMI, a standard for exchanging data between simulation software programs at run-time, to form a coupled chemical-mechanical-hydrogeological model of the system. The approach combines a tunnel scale stress analysis finite element model, a discrete element model for accurately modeling the patterns of emerging cracks in the concrete, and a finite element and finite volume model of the chemical processes and alteration in the porous matrix and cracks in the concrete, to produce a fully coupled model of the system. Combining existing detailed simulation software in this way with OpenMI has the benefit of not relying on simplifications that might be necessary to combine all of the modeled processes in a single piece of software.
Abe, Toru*; Hirano, Fumio; Mihara, Morihiro; Honda, Akira
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 27(1), p.3 - 11, 2020/06
Degradation of TRU waste in a geological disposal facility may cause the formation of a nitrate plume. A Nitrate Evolution model due to mineral reactions, microbial activity, and metal corrosiON (NEON) has therefore been developed to evaluate the safety case for geological disposal of TRU waste. Small scale laboratory experiments can be reproduced satisfactorily, however, it is necessary to demonstrate the applicability of the NEON model on scales relevant to the geological disposal of TRU waste. In the current study, an industrial analogue of a nitrate plume from the pollution of groundwater from nitrate fertilizers used on Ikuchi Island, Japan was selected to test the applicability of the NEON model. Concentration profiles of nitrate ions in the groundwater were successfully reproduced over the hundreds of meters scale demonstrating the applicability of the NEON model in evaluating the chemical behavior of a nitrate plume derived from the geological disposal of TRU waste.
Akai, Masanobu; Ito, Nobuyuki*; Yamaguchi, Tetsuji; Tanaka, Tadao; Iida, Yoshihisa; Nakayama, Shinichi; Inagaki, Shingo*
JAERI-Tech 2004-058, 47 Pages, 2004/09
Geochemistry Research Equipment for TRU Waste Elements has been installed in Back-end Cycle Key Elements Research Facility (BECKY) of Nuclear Fuel Cycle Safety Engineering Research Facility (NUCEF). This equipment is designed to study geochemical behavior of TRU elements and other radionuclides contained in TRU waste (TRU waste elements) and to acquire data for safety assessments of radioactive wastes disposal. The equipment consists of anaerobic glove box systems, aerobic glove box systems equipped with built-in barrier performance testing apparatus, and analytical instruments. This report describes principles, structure, performance and safety designs of each component of the equipment, and results of research performed in the equipment.
Kanno, Mitsuhiro*; Takeda, Seiji; Minase, Naofumi; Kato, Hideo; Kimura, Hideo
JAERI-Conf 2004-011, p.131 - 132, 2004/07
no abstracts in English
Kato, Hiroshige*; Mine, Tatsuya*; Mihara, Morihiro; Oi, Takao; Honda, Akira
JNC-TN8400 2001-029, 63 Pages, 2002/01
Cementitious materials will be used for the TRU waste repository as a component of engineered barrier system. The distribution coefficients which represent the retardation of radionuclides migration for the cementitious materials would be one of the important parameter for the safety assessment. The much information of radionuclide sorption onto the cementitious materials has been accumulated through the study in the world. Therefore it is necessary to compile the information and Kd of the radionuclides reported in previous studies. In this report, the Kd of the important radionuclides, such as C, Ni, Se, Sr, Zr, Nb, Mo, Tc, Sn, I, Cs, Sm, Pb, Ra, Ac, Th, Pa, U, Np, Pu, Am, Cm, for the cementitious materials were compiled as the Sorption Database (SDB). For radionuclides to be sensitive to the redox potential, e.g. Se, Tc, Pa, U, Pu and Np, some Kds measured under the controlled atmosphere had been reported, and few Kds measured under the controlled redox potential had been reported. For Se, Mo, Sm, Cm and Ac, the distribution coefficients had not been reported, therefore distribution coefficients of Se and Mo for OPC (Ordinary Portland Cement) pastes were measured by batch sorption experiments and these data were added into the SDB.
Aoyagi, Takayoshi*; *; Mihara, Morihiro; Okutsu, Kazuo*; Maeda, Munehiro*
JNC-TN8400 2001-024, 103 Pages, 2001/06
In the disposal concept of TRU waste, concentrated disposal of wastes forms in large cross-section underground cavities is envisaged, because most of TRU waste is no-heat producing in spite of large generated volume as compared with HLW. In the design of engineered barrier system based on large cross-section cavities, it is necessary to consider the long-term mechanical process such as creep displacement of the host rock from the viewpoint of the stability of engineered barrier system. In this study, the long-term creep displacement of the host rock was calculated using the non-linear viscoelasticity model and the effects on the stability of engineered barrier system was evaluated. As a result, in the disposal concept of crystalline rock, no creep displacement occurred at the time after 1 milion year. On the other hand, in the disposal concept of sedimentary rock, creep displacement of 8090mm occurred at the time after 1 milion year. Also, in this calculation, a maximum reduction of 45mm concerned with the thickness of buffer material was estimated. But these values resulted within allowance of design values. Therefore, these results show that the effects of the creep displacement on the stability of engieered barrier system would not be significant.
Yoshikawa, Hideki; Ishikawa, Hirohisa;
JNC-TN8200 2001-004, 160 Pages, 2001/06
Haruyama, Mitsuo; Ara, Katsuyuki*; Takase, Misao*
Nippon Genshiryoku Gakkai-Shi, 43(4), p.397 - 404, 2001/04
no abstracts in English
; Nishikawa, Yoshiaki*; ;
JNC-TN8400 2001-002, 23 Pages, 2000/12
The soluble organic compounds generated by radiological degradation of asphalt ( ray) were confirmed as a part of influence of the bituminized waste degradation in the TRU waste repositry. Especially, the influence of the nitrate was focused on. As a result, the concentration of the soluble organic compounds generated by radiological degradation of asphalt (10MGy, ray which is correspond to absorbed dose of asphalt for 1,000,000years) were lower (each formic acid : about 50mg/dm, acetic acid : about 30mg/dm and oxalic acid : about 2mg/dm) than that of the formic acid, the acetic acid and the oxalic acid which Valcke et al. had shown (the influence of the organic at the solubility examination which uses Pu and Am). Moreover, the change in the concentration of TOC and the soluble organic compounds (formic acid, acetic acid and oxalic acid) is little under the existence of nitrate ion. That is, the formic acid and acetic acid which can be organic ligands were generated little by oxidative decomposition of asphalt in the process that nitrate ion becomes nitrite ion by radiation. The influence of the soluble organic compounds by the radiological degradation of the asphalt ( ray) on adsorption and solubility by the complexation of radionuclides in the performance assessment can be limited.
Owada, Hitoshi*; Mihara, Morihiro; *; *
JNC-TN8400 2000-027, 19 Pages, 2000/08
Bactch leaching experiments of granite with the artifitial cement leachate and the leachate of low-alkalinity-cement (LW) were carried out to evaluate the effect of the hiperalkaline plume on the environment of the high-level and TRU radioactive waste repository. Dissolution of Si and Al from feldspar included in the granite and precipitation of C-S-H were confirmed from the results of the leaching experiments with artifitial cement leachate. From this result it was found that the composition of sorrounding rock changed. It also suggested that the retardation factor of migration of radionuclides would change. On the contrary, only decrease of concentrations in Si, Al and Ca in the leachate was observed in the experiment with LW. This result might indicate that C-S-H and/or C-A-S-H precipitated as secondary minerals in the LW case. From these results, it was considered that the hiperalkaline plume from the cementitious leachate might caused the change of disposal conditions such as the change in distribution coefficients of rock by precipitation of the secondary mineral and the increase in hydraulic conductivity by the dissolution of rock. On the other hand, the influences of the LW would be comparatively small, because LW and granite might equilibrate in short time.
Mine, Tatsuya*; Mihara, Morihiro;
JNC-TN8430 2000-009, 35 Pages, 2000/07
In the geological disposal system of TRU wastes, nitrogen generation by denitrifying bacteria could provide significant impact on the assessment of this system, because nitrate contained in process concentrated liquid waste might be electron acceptor for denitrifying bacteria. In this study, the activities and tolerance of denitrifying bacteria under disposal condition were investigated. pseudomonas denitrificans as denitrifying bacteria was used. The results showed that Pseudomonas denitrificans had activity under reducing condition, but under high pH condition (PH9.5), the activity of Pseudomonas denitrificans was not detected. It is possible that the activity of Pseudomonas denitrificans would be low under disposal condition.
JNC-TN1400 2000-007, 100 Pages, 2000/07
no abstracts in English
Kato, Hiroshige*; Sato, Mitsuyoshi*; Owada, Hitoshi*; Mihara, Morihiro;
JNC-TN8430 2000-008, 53 Pages, 2000/05
Cementitious materials will be used in TRU waste disposal repository. In such cases, it is considered that the migration of alkaline leachates from cementitious materials, so called high pH plume, will cause dissolution of rock and precipitation of secondary minerals. In addition, the high pH plume will move along the flow of groundwater, so it is predicted that rock formation and components of high pH groundwater vary with time and space. However, time and spatial dependence of the variations of secondary minerals and groundwater components has not been clarified. In order to acquire the data of variations of secondary minerals and groundwater components, we carried out the rock alteration experiments with column method. The crushed granodiorite was filled into 4 meters length column (3.7 cm) and artificial cement leachate (pH=13.3; Na=0,1 mol/l, K=0.1 mol/l, Ca=0.002 mol/l) was streamed at flow rates of 0.1 ml/min for 7 months at 80C. As the result, secondary minerals confirmed on the rock were calcite and C-S-H at upstream of column and C-S-H at mid-downstream. The pH value of the fluid dominated by Na and K did not be decreased by reaction with the rock. In this study, the data relating to the effect of high pH plume on rock over the long term was acquired.
Mine, Tatsuya*; Mihara, Morihiro; ; *; *
JNC-TN8430 2000-003, 33 Pages, 2000/04
On the geological disposal system of the radioactive wastes, the activities of the microorganisms that could degrade the asphalt might be significant for the assessment of the system performance. As the main effects of the biodegradation of the asphalt, the fluctuation of leaching behavior of the nuclides included in asphalt waste has been indicated. In this study, the asphalt biodegradation test was carried out. The microorganism of which asphalt degradation ability was comparatively higher under aerobic condition and anaerobic condition was used. The asphalt biodegradation rate was calculated and it was evaluated whether the asphalt biodegradation in this system could occur. The results show that the asphalt biodegradation rate under anaerobic and high alkali condition will be 300 times lower than under aerobic and neutral pH.
Federation of Electric Power Companies of Japan*
JNC-TY1400 2000-001, 464 Pages, 2000/03
Owada, Hitoshi*; Mihara, Morihiro; Iriya, Keishiro*; *
JNC-TN8400 99-057, 43 Pages, 2000/03
Cementitious materials are considered as candidate materials for the geological disposal of high-level radioactive waste and TRU waste. As the pH and the Ca content of leachate from the cementitious materials are high, the host rock and the buffer-material would be degraded by the leachate in the long-term. Therefore, transport properties and parameters such as solubilities and distribution coefficients of radionuclides would be changed and affect the performance of the repository. In order to dissolve this "High pH plobrem", the use of a low alkalinity cement is considered for the disposal. In this study, we summarized the necessity of the low alkalinity cement, and developed the approach of the low alkalinization of cement. And, the following were carried out in this study : A leaching test of cement paste, a fluid test of the mortar and a installation test of the concrete to the trial structure. From the leaching test using the cement paste, we confirmed that we were able to obtain the low alkalinity cement (HFSC) by addition of pozzolanic materials such as silica-fume and flyash. From the result of the fluid test of the mortar, we chose the cement for the practicability evaluation. The practicability of low alkalinity concrete was evaluated by installation test to the trial structure.As a result of these examinations, we proved that the pH value of the leachate from the cementitious material was reduced by adding SF and FA to Portland cement. Simultaneously, SF and FA had to be added in order to obtain the good workability. In addition, workability and mechanical strength of the cement which SF and FA were added are almost equivalent to the ordinary Portland cement. The results shows that the HFSC has high practicability.
; Nishikawa, Yoshiaki*; ;
JNC-TN8400 2000-017, 30 Pages, 2000/03
The influence of the cement additives on the distribution coefficients of americium-241 to the Ca-bentonite was confirmed. The adsorption experiment of americium-241 to Ca-bentonite with cement additives was performed by the batch method, as a part of the influence evaluation of the organic in the research of TRU waste disposal. As a result, the distribution coefficient of americium-241 to the Ca-bentonite was over 1.2E+3m/kg in the condition of the absence of cement additives. In the case of low concentration (0.3g/kg) of the naphthalenesulfonic acid type cement additives, the distribution coefficient was 5.2E+2mkg. And, in the case of high concentration (30g/kg) of the same cement additives, the distribution coefficients was 2.0E-1m/kg. On the other hand in the case of flow concentration (0.5g/kg) of the polycarboxylic acid type cement additives, the distribution coefficients was over 1.3E+3m/kg. And, in the case of high concentration (50g/kg) of the same cement additives, the distribution coefficient was 1.8E-1m/kg. Here, selected cement additives concentrations were based on a standard concentration of 10g/kg when the ratio of water:cement is about one. From these results, the distribution coefficient of americium-241 to the Ca-bentonite decreases according cement additive concentration. The distribution coefficients were similar on different kinds of cement additives. The cement additives concentration influences the distribution coefficient. The distribution coefficient was small in the case of high concentration of the cement additives. That is, it is thought that the cement additives have small influences on the distribution coefficient of americium-241 to the Ca-bentonite in the case of low concentration, though the cement additives have influences on the distribution coefficient of americium-241 to the Ca-bentonite in the case of high concentration.
JNC-TJ8400 2000-044, 53 Pages, 2000/02
To estimate the polyelectrolyte effect and the effect of the heterogeneous composition of humic acids, the complex formation constants of Eu(III) and Ca(II) with Aldrich humic acid and polyacrylic acid were obtained, for Eu(10 to 10 M) by solvent extraction with TTA and TBP in xylene, for Ca (10M) with TTA and TOPO in cyclohexane and for Ca(10M) by using ion-selective electrode. By defining the apparent formation as = [MR]/([M][R]), where [R] denotes the concentration of dissociated functional group, [M] and [MR] denote the concentration of free and bound metal ion and pcH is defined as-log[H], the values of log have been obtained at pcH 4.8 - 5.5 in 0.1 - 1.0M NaClO and NaCl. Log of Eu-humate varied from 5.0 to 9.3 and that of Ca-humate from 2.0 to 3.4..For both humate and polyacrylate, log increased with pcH or with the degree of dissociation. The increase in the ionic strength O.1 to 1.0 M decreased the log, the decrease in log of Eu(III)-humate is 1.6, that of Eu(III), polyacrylate 0.7, that of Ca(II)-humate 1.9 and that of Ca(II)-polyacrylate 1.2. While the increase in the metal ion produced no effect on log of polyacrylate, log of humate decreased. Depending on the concentration of Eu(III), the coexistence of Ca(II) reduced log of humate by 0 to 0.8. The dependence of log of humate on the metal ion concentration suggests the coexistence of strong and weak binding sites in the hmnic acid.
Aoyagi, Takayoshi*; Mihara, Morihiro; Tanaka, M.*; Okutsu, Kazuo*
JNC-TN8400 99-058, 55 Pages, 1999/11
For the emplaced waste in TRU waste disposal facility, it may have the void for waste bodies it. And, generating void which accompanies those component elution in concrete pit and filler in which the cement material becomes the candidate material is assumed. It is considered that the security of the diffusion control in the bentonite is not done when these voids collapsed, and when it generated the volume change inside the buffer material (bentonite). The imperfect blockage of the void by not obtaining, the sufficient swelling pameability swelling bentonite is a cause on this. Then, volume change of the bentonite inside is analyzed in this study under the conservative estimation. And the following are tested: Self-sealing, maximum swelling rate, density distribution change of the batonite. Evaluation of the engineered barrier system for volume change from the result was carried out. Prior to the evaluation, generating void was calculated based on the conservative estimation. The density of the buffer material as it assumed the blocking by buffer material uniformly awelling using this calculated data, was obtained. By the permeability got from existing research result which shows the relationship between density and permeability of the bentonite, it was confirmed to become diffusion control in the buffer material inside, in existing engineered barrier specification. Next, it was tested, when the conservative void of the superscription was assumed, in order to confirm whether it does the security, as permeability necessaly for maintaining diffusion control, puts it for the swelling of actual bentonite. As the result, it was possible to confirm sufficient swelling performance in order to do the security of the diffusion control in Na-bentonite. However, the swelling performance greatly lowered by comparing Na-bentonite in Ca-bentonite with under 1/6. The increase of the permeability not do the security of the diffusion control, when it was based on void quantity ...
JNC-TN1400 99-019, 117 Pages, 1999/10
no abstracts in English